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| Intellectual disability v9.275 | BORCS5 |
Ida Ertmanska gene: BORCS5 was added gene: BORCS5 was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: BORCS5 was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: BORCS5 were set to 27435318; 40385417; 40621786 Phenotypes for gene: BORCS5 were set to arthrogryposis multiplex congenita, MONDO:0015168; neurodevelopmental disorder, MONDO:0700092 Review for gene: BORCS5 was set to GREEN Added comment: PMID: 40621786 Fisher et al., 2025 Report of 2 fetal cases in a consanguineous Pakistani family. Exome seq revealed a homozygous nonsense variant c.283C>T, p.(Arg95Ter) in BORCS5 (NM_058169.4). Individuals showed neuroaxonal dystrophy with osteopetrosis. PMID: 40385417 Mencacci et al., 2025 - pre-print Report of 12 individuals from 7 unrelated families with biallelic BORCS5 variants (NM_058169.4): two missense variants (c.284G>A, p.R95Q; c.296A>C, p.H99P) and four LoF alleles (c.203–1G>T, p.?; c.316delG, p.A106Pfs*20; c.382_383delAG, p.L128Vfs*86; c.417C>G, p.Y139*). Table 1 = phenotypic spectrum of 6 individuals from families 1-4: profound ID (6/6), severe spasticity (6/6), seizures (6/6), hyperreflexia (6/6), Parkinsonism/dystonia (3/6), limb contractures (5/6), optic atrophy (5/6), abnormal brain MRI including cerebral atrophy and/or corpus callosum agenesis (5/6), microcephaly (6/6 - severity not stated), muscle atrophy (5/6). Infantile onset. Neuroimaging in 5 cases showed cerebral atrophy, white matter loss, hypomyelination, small T2-hypointense thalami, thin brainstem, and optic nerve atrophy. PMID: 27435318 Charng et al., 2016 Patient BAB6775 homozygous for NM_058169.4 BORCS5: c.203-1G>T, with DD, microcephaly, seizures, cortical malformations, polymicrogyria, agenesis of corpus callosum. Also reported with more details in PMID:40385417 (do not count). Additional functional evidence: Zebrafish borcs5 knockout leads to neurodevelopmental defects:microcephaly, ventriculomegaly, movement disorders and epilepsy. BORCS5 is not yet associated with a disease in OMIM (accessed 20th Feb 2026). Sources: Literature |
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| Intellectual disability v9.236 | AIMP2 |
Ida Ertmanska changed review comment from: Additional cases: PMID: 38374194 Abolhassani et al., 2024 Patient 925, 3yo Iranian female, with NM_006303.4(AIMP2):c.34_35delinsC (p.Gly12ProfsTer?). She presented with: Preterm birth; Low birth weight; Microcephaly; Mild learning difficulty; Developmental delay, speech & motor; Epilepsy; Hypertonia; Limb atrophy & spasticity; Muscle weakness; Strabismus; Ophthalmoplegia; Visual impairment; Anemia. Also homozygous for a VUS SBF1 variant p.Met524Arg (SBF1 is associated with recessive CMT). PMID: 35140751 Mazaheri et al., 2022 Iranian proband - 7-month-old infant with a progressive neurological disorder characterized by lack of development, weight loss, severe anemia, skeletal abnormalities, microcephaly and MR imaging features of leukodystrophy. WES revealed a homozygous AIMP2 c.670A>T (p.Lys224Ter) variant, confirmed het in each parent. No mention of seizures. Variant predicted to escape NMD. PMID: 35568357 Masih et al., 2022 Patient F32.1 - 5yo Indian male - homozygous for NM_006303.4(AIMP2):c.74A>G (p.Tyr25Cys). Clinical presentation: severe DD/ID, generalised tonic-clonic seizures, dysmorphic features, short stature, feeding difficulties, spastic quadriparesis, thin corpus callosum on MRI. Diagnosed with Leukodystrophy, hypomyelinating, 17. This gene is associated with AR Leukodystrophy, hypomyelinating, 17, MIM:618006 (OMIM accessed 19th Jan 2025). The association between AIMP2 and AR leukodystrophy, hypomyelinating, 17 has been classified as Definitive in ClinGen (Leukodystrophy and Leukoencephalopathy Expert Panel, Sept 2025).; to: Additional cases: PMID: 38374194 Abolhassani et al., 2024 Patient 925, 3yo Iranian female, with NM_006303.4(AIMP2):c.34_35delinsC (p.Gly12ProfsTer?). She presented with: Preterm birth; Low birth weight; Microcephaly; Mild learning difficulty; Developmental delay, speech & motor; Epilepsy; Hypertonia; Limb atrophy & spasticity; Muscle weakness; Strabismus; Ophthalmoplegia; Visual impairment; Anemia. Also homozygous for a VUS SBF1 variant p.Met524Arg (SBF1 is associated with recessive CMT). PMID: 35140751 Mazaheri et al., 2022 Iranian proband - 7-month-old infant with a progressive neurological disorder characterized by lack of development, weight loss, severe anemia, skeletal abnormalities, microcephaly and MR imaging features of leukodystrophy. WES revealed a homozygous AIMP2 c.670A>T (p.Lys224Ter) variant, confirmed het in each parent. No mention of seizures. Variant predicted to escape NMD. PMID: 35568357 Masih et al., 2022 Patient F32.1 - 5yo Indian male - homozygous for NM_006303.4(AIMP2):c.74A>G (p.Tyr25Cys). Clinical presentation: severe DD/ID, generalised tonic-clonic seizures, dysmorphic features, short stature, feeding difficulties, spastic quadriparesis, thin corpus callosum on MRI. Diagnosed with Leukodystrophy, hypomyelinating, 17. PMID: 26795593 Helbig et al., 2016 Proband with Epileptic encephalopathy. Compound het for AIMP2 c.575-2A>G and c.72_73del (p.Met24IlefsTer25). Patient also has alteration in LRFN2 (not associated with disease in OMIM). This gene is associated with AR Leukodystrophy, hypomyelinating, 17, MIM:618006 (OMIM accessed 19th Jan 2025). The association between AIMP2 and AR leukodystrophy, hypomyelinating, 17 has been classified as Definitive in ClinGen (Leukodystrophy and Leukoencephalopathy Expert Panel, Sept 2025). |
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| Intellectual disability v9.193 | LDB1 |
Arina Puzriakova gene: LDB1 was added gene: LDB1 was added to Intellectual disability. Sources: Literature Q4_25_promote_green tags were added to gene: LDB1. Mode of inheritance for gene: LDB1 was set to MONOALLELIC, autosomal or pseudoautosomal, NOT imprinted Publications for gene: LDB1 were set to 39680505; 38091987; 33077954 Phenotypes for gene: LDB1 were set to Congenital hydrocephalus, MONDO:0016349 Review for gene: LDB1 was set to GREEN Added comment: - Allington et al. 2024 (PMID: 39680505) investigate a cohort of 2697 trios with congenital primary cerebral ventriculomegaly using WES. Eight unrelated individuals identified with de novo variants in LDB1 (7 LOF, 1 predicted damaging missense) - exhibiting perinatally diagnosed cerebral ventriculomegaly, including neurosurgically treated congenital hydrocephalus. Additionally, 5/8 GDD, 3/8 autism, 2/8 delayed gross motor development, 2/8 had congenital heart defects (inc. coarctation, PDA), 2/8 camptodactyly. Additional case was identified from GeneMatcher with a de novo frameshift variants in LDB1. Phenotypes include severe ventriculomegaly, absence of well formed gyri, severe limb contractures and camptodactyly. Search of Decipher/DDD also revealed 4 pathogenic de novo variants in LDB1 and associated binding partners in individuals congenital ventriculomegaly. - Torene et al. 2023 (PMID: 38091987) identified three individuals with protein truncating variants. Two individuals with de novo variants both had ventriculomegaly, hypotonia, GDD, craniofacial abnormalities. The third individual inherited the variants from an asymptomatic mother, and displayed developmental delay, hypotonia, congenital heart defects and a small hypoplastic hippocampi but did not have ventriculomegaly or craniofacial anomalies. - Jin et al. 2020 (PMID: 33077954) also report an individual with a de novo LOF variant in this gene who had congenital hydrocephalus but details on this case are otherwise limited. Sources: Literature |
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| Intellectual disability v9.160 | KIF26A |
Ida Ertmanska gene: KIF26A was added gene: KIF26A was added to Intellectual disability. Sources: Other Mode of inheritance for gene: KIF26A was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: KIF26A were set to 36228617; 36564622; 39305096 Phenotypes for gene: KIF26A were set to Cortical dysplasia, complex, with other brain malformations 11, OMIM:620156; cortical dysplasia, complex, with other brain malformations 11 MONDO:0859332 Review for gene: KIF26A was set to AMBER Added comment: At least 13 patients from 10 families have been described in literature with biallelic variants in KIF26A and KIF26A‐related disorder (PMIDs: 36228617; 36564622; 39305096). The heterogenous syndromic presentation may include developmental delay / intellectual disability (6/8, mild to moderate), cardiac defects (6/7), neurological features e.g. hypotonia (2), spasticity (2), paediatric intestinal pseudo‐obstruction (PIPO) (3/13). While only 3/13 patients were diagnosed with PIPO, 8/13 patients had gastrointestinal issues, including megacolon, ischemic small bowels, severe ascites, abdominal distension, vomiting, and intestinal obstruction. Note: several individuals died before certain clinical features could be assessed. Brain MRI showed Ventriculomegaly/Hydrocephalus in 12/12 patients and corpus callosum agenesis / hypoplasia in 7/12 cases; unavailable in 1 case. Other malformations noted on MRI: Hypogenesis of septum pellucidum, Brainstem patterning disorder, Long midbrain, Small pons, Brain atrophy, Reduced white matter, Bilateral schizencephaly, Absent hippocampal commissure. PMID: 39305096 Nosrati et al., 2025 Seq method: Trio exome. Case #1 - 8yo Italian male; at birth: axial hypotonia, poor suction, failed to pass meconium, leading to surgery for Hirschsprung's disease. Compound het c.4378C > T, p.(Arg1460Trp); c.5238C > G, p.(Phe1746Leu). Case #2 - 6mo Syrian female; presented with abdominal distension and intestinal obstruction symptoms; imaging revealed dilated bowels without mechanical obstruction; biopsies of small and large intestine showed hypoganglionosis. Homozygous for c.4085dup, p.(Ala1363Glyfs*47). Case #3 - female born to consanguineous parents (Palestinian / Jordanian) - very different presentation: severe spastic quadriplegic cerebral palsy (CP) with epilepsy, hearing problems and cognitive impairments. Homozygous for c.3996C > A, p.(Cys1332*). PMID: 36564622 Almannai et al., 2023 Seq method: clinical WES. Report of 2 families with KIF26A‐related disorder. Family 1: 4 affected individuals, homozygous for c.792dupC, p.(Val265Argfs*5), all presented with persistent abdominal distension and vomiting after birth. 3 individuals died between 2-11 months, 1 patient alive at 3.5 years. Family 2: proband presented at 3 months with symptoms indicating intestinal obstruction and marked abdominal distension. Symptoms persist at 7yo. Homozygous for c.3330delC, p.(Ser1111Alafs*137). 36228617 Qian et al., 2022 Seq method: WES. 5 unrelated subjects with congenital brain malformations who had inherited biallelic mutations in KIF26A A01 - consanguineous Turkish family, microcephaly (−3.45SD) and an MRI suggesting a component of cerebral atrophy, as well as dysmorphic features and ileus with megacolon. Homozygous for c.3440dupC, p.Ala1148Cysfs*20. B01 - diagnosed prenatally with bilateral schizencephaly at 21 weeks; pregnancy terminated; compound heterozygous c.2161C>T, p.Arg721Cys, and c.4676C>T, p.Ala1559Val C01 - male, non-consanguineous parents, presented with mild developmental delay and learning disability. Brain MRI at 18 years demonstrated agenesis of the corpus callosum; compound het KIF26A: c.4676C>T, p.Arg1624Cys, and c.4870C>T, p.Ala1559Val D01 - was diagnosed with polymicrogyria and hydrocephalus, with inherited compound heterozygous variants in KIF26A: c.2845C>T, p.Pro949Ser, and c.4676C>T, p.Ala1559Val E01 - male born to consanguineous parents with growth retardation and developmental delay. Brain MRI performed at 18 months revealed a thin CC, ventriculomegaly and polymicrogyria; homozygous for c.4804C>T; p.Arg1602Trp. KIF26A is associated with Cortical dysplasia, complex, with other brain malformations 11, 620156 in OMIM (accessed 31st Oct 2025). The association of KIF26A and 'complex cortical dysplasia with other brain malformations' is classified as Strong in ClinGen (March 2024). Sources: Other |
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| Intellectual disability v9.154 | KIAA0556 |
Arina Puzriakova gene: KIAA0556 was added gene: KIAA0556 was added to Intellectual disability. Sources: ClinGen,Literature new-gene-name, Q3_25_promote_green tags were added to gene: KIAA0556. Mode of inheritance for gene: KIAA0556 was set to BIALLELIC, autosomal or pseudoautosomal Phenotypes for gene: KIAA0556 were set to Joubert syndrome 26, OMIM:616784; Joubert syndrome 26, MONDO:0014771 Review for gene: KIAA0556 was set to GREEN Added comment: KIAA0556 (also known as KATNIP) is now associated with Joubert syndrome 26, OMIM:616784 (AR) in OMIM (accessed 21st Oct 2025), and has a DEFINITIVE gene disease association with autosomal recessive ciliopathy-KATNIP (MONDO:0005308) in ClinGen (curation entry from 07/10/2023). The ClinGen summary states that there are eight variants (nonsense, frameshift, splice-site) reported in 6 probands in 6 publications (PMIDs: 26714646, 27245168, 31197031, 36580738, 32164589, 30982090). There have been 2 additional reports since their review (PMIDs: 40725402, 40428346) In total there are now 13 individuals from 8 families. In 2 of the families additional variants were found in other genes. These families are listed last in this review. Main phenotypes observed in the cases with only KIAA0556 variants: - Brain abnormalities (including molar tooth sign) were seen in 9 individuals (5 families, 1 of these mild). - Hypotonia was observed in 6 individuals (4 families). - Short stature/Growth hormone deficiency/pituitary abnormalities were seen in 4 individuals (3 families) - Developmental delay/intellectual disability was reported as severe in 4 individuals( 2 families), mild/unknown severity in an additional 3 individuals (2 families). - An eye phenotype was observed in 4 individuals (3 families) - A renal phenotype was only observed in 1 family (PMID: 40725402). Evidence: PMID:26714646 (Sanders et al 2015) - 3 children in a consanguineous Saudi Arabian family with global developmental delay and suspected Jouberts syndrome based on neuroimaging studies. Variable features between the children included recurrent infections (2), hypotonia( 2), cleft palate (1), small penis (1), short stature (1), hypopituitarism (2). No renal involvement. In patient fibroblasts there were a significant reduction in cilia compared to controls, and cilia that were present were abnormally long. Kiaa0556 knockout mice showed brain-specific defects resulting in hydrocephalus. In human cells KIAA0556 was found to locate a the ciliary base, axoneme and tip. PMID:27245168 (Roosing et al 2016) - WES in consanguineous family from India identified a KIAA0556 homozygous single base pair deletion mutation in 2 siblings. Both showed nystagmus and oculomotor apraxia, bilaterial ptosis, hypotonia, characteristic ‘molar tooth’ sign on brain imaging and developmental delay (severity not noted). Cone dystrophy was identified, but gross visual function was not impaired. No renal or liver phenotype. A zebrafish model with kiaa0556 knocked down showed curly tails, smaller head size and perithoracic and abdominal edema which is like other ciliopathy morphants. PMID:31197031 (Fujita et al 2019) - blood and/or hypothalamic hamartoma (HH, congenital brain malformation associated with drug-resistant epilepsy) tissue samples from 38 undiagnosed patients were analysed using WES. Germline, compound heterozygous variants in KIAA0556 were found in one 5 yo female patient (individual 12698), c.2373del (p.Asp791Glufs*206),c.4551+1G>A. Brain anomalies in this patient included agenesis of the corpus callosum, pituitary hypoplasia, the molar tooth sign, and HH. Other clinical features reported include hypotonia, oculomotor apraxia and developmental delay. PMID:36580738 (Aksu Uzunhan et al 2023) - 2-year-old male with compound heterozygous variants KATNIP gene. He had growth hormone deficiency and central hypothyroidism, with some minor dysmorphic features. His neurodevelopment seemed normal, but cranial MRI abnormalities without a classical molar tooth sign, ectopic neurohypophysis and combined pituitary hormone deficiency. No renal, liver or eye phenotype. PMID: 40725402 (Kulyamzin et al 2025) - 24 yo female from a non-consanguineous family of mixed Jewish origin who presented with type 2 glomerulonephritis at age 7 and underwent 2 kidney transplantations. She later developed SNHL, which was attributed to antibiotic toxicity, high intracranial pressure, and a differential diagnosis of cone rod dystrophy vs macular dystrophy with peripheral involvement. WES revealed two rare heterozygous variants in the KATNIP (KIAA0556) gene (NM_015202.4): c.49C>T; p.(Arg17*) and c.4711A>G; p.(Ser1571Gly). The proband was also heterozygous for a likely-pathogenic variant in POLG. Heterozygous variants in POLG have been linked to progressive external ophthalmoplegia (weakness of eye muscles), but the proband did not present with this. PMID: 40428346 (Tedesco et al 2025) 5-year-old male from a consanguineous family of Roma ethnic background. Clinical features include severe developmental delay, hypotonia, and post-axial polydactyly. He had a normal cerebral MRI without the molar tooth sign, but showed severe anemia and esophageal atresia. WES identified a homozygous novel frameshift variant c.808del, p.Ser270ValfsTer28 in KATNIP. A good summary of all cases to date is provided. Patients with variants in KIAA0556/KATNIP and another gene: PMID:32164589 (Niceta et al 2020) - 7 year old with homozygosity for mutations in KIF7 and KIAA0556 identified by WES. The patient displayed Joubert syndrome complicated by iris and retinochoroidal coloboma, hypogonadism pituitary malformation, and growth hormone deficiency. Severe intellectual disability was reported. PMID:30982090 (Cauley et al 2019) - Sudanese family in 3 siblings with homozygous truncating variants in both KIAA0556 and ADGRG1/GPR56 and a severe brain malformation (bilateral frontal polymicrogyra, mild molar tooth sign), severe psychomotor delay, intellectual disability and seizures. Sources: ClinGen, Literature |
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| Intellectual disability v9.51 | MED16 |
Karen Stals gene: MED16 was added gene: MED16 was added to Intellectual disability. Sources: NHS GMS Mode of inheritance for gene: MED16 was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: MED16 were set to PMID: 40081376 Phenotypes for gene: MED16 were set to developmental delay; multiple congenital abnormalities; Medopathy Penetrance for gene: MED16 were set to unknown Review for gene: MED16 was set to GREEN gene: MED16 was marked as current diagnostic Added comment: 25 individuals from 18 families reported with biallelic MED16 variants with multiple congenital anomalies (MCAs)-intellectual disability syndrome. Intellectual disability, speech delay, and/or motor delay of variable severity were constant and associated with variable combinations of craniofacial defects (micro/retrognathia, cleft palate, and preauricular tags), anomalies of the extremities, and heart defects (predominantly tetralogy of Fallot). Visual impairment, deafness, and magnetic resonance imaging (MRI) abnormalities were also frequent. 8 predicted protein-truncating and 18 missense or in-frame duplication variants identified. Sources: NHS GMS |
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| Intellectual disability v9.11 | SEL1L |
Achchuthan Shanmugasundram changed review comment from: PMID:37943610 reported six patients from three unrelated families with a neurodevelopmental disorder involving developmental delay, intellectual disability, facial dysmorphisms, short stature, microcephaly and seizures. Five patients from two families (Saudi Arabian and Moroccan descent) were identified with homozygous SEL1L variants (p.(Gly585Asp) & p.(Met528Arg)), while an unrelated patient of Italian descent was identified with homozygous HRD1 variant. Although there are additional variants reported in Saudi Arabian patient, SEL1L variant was considered as the potential candidate due to its biological relevance as reported in previous studies in mice. The variants were hypomorphic and impaired endoplasmic reticulum (ER)-associated degradation. PMID:37943617 reported the identification of a homozygous SEL1L variant (p.(Cys141Tyr)) in five patients from a consanguineous Slovakian family. These patients presented with not only ERAD-associated neurodevelopmental disorders with onset in infancy (ENDI) syndromes, but infantile-onset agammaglobulinemia with no mature B cells, resulting in frequent infections and early death. All patients exhibited intellectual disability and were unable to speak words and sentences. Although variant in FAR2 gene was also identified in these patients, Sanger sequencing confirmed the segregation of the FAR2 variant with symptoms in patient 2 and FAR2 function is not linked to neurological disorder or agammaglobulinemia, leading to its exclusion from being causal for these patients. This gene has been associated with relevant phenotypes in OMIM (MIMs #621067 & #621068), but not yet in Gene2Phenotype.; to: PMID:37943610 reported six patients from three unrelated families with a neurodevelopmental disorder involving developmental delay, intellectual disability, facial dysmorphisms, short stature, microcephaly and seizures. Five patients from two families (Saudi Arabian and Moroccan descent) were identified with homozygous SEL1L variants (p.(Gly585Asp) & p.(Met528Arg)), while an unrelated patient of Italian descent was identified with homozygous HRD1 variant. The variants were hypomorphic and impaired endoplasmic reticulum (ER)-associated degradation. PMID:37943617 reported the identification of a homozygous SEL1L variant (p.(Cys141Tyr)) in five patients from a consanguineous Slovakian family. These patients presented with not only ERAD-associated neurodevelopmental disorders with onset in infancy (ENDI) syndromes, but infantile-onset agammaglobulinemia with no mature B cells, resulting in frequent infections and early death. All patients exhibited intellectual disability and were unable to speak words and sentences. This gene has been associated with relevant phenotypes in OMIM (MIMs #621067 & #621068), but not yet in Gene2Phenotype. |
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| Intellectual disability v9.11 | SEL1L | Achchuthan Shanmugasundram Phenotypes for gene: SEL1L were changed from Neurodevelopmental disorder to Neurodevelopmental disorder with hypotonia, poor growth, dysmorphic facies, and agammaglobulinemia, OMIM:621068; ?Neurodevelopmental disorder with poor growth, absent speech, progressive ataxia, and dysmorphic facies, OMIM:621067 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability v9.9 | SEL1L |
Achchuthan Shanmugasundram changed review comment from: PMID:37943610 reported six patients from three unrelated families with a neurodevelopmental disorder involving developmental delay, intellectual disability, facial dysmorphisms, short stature, microcephaly and seizures. Five patients from two families (Saudi Arabian and Moroccan descent) were identified with homozygous SEL1L variants (p.(Gly585Asp) & p.(Met528Arg)), while an unrelated patient of Italian descent was identified with homozygous HRD1 variant. Although there are additional variants reported in Saudi Arabian patient, SEL1L variant was considered as the potential candidate due to its biological relevance as reported in previous studies in mice. The variants were hypomorphic and impaired endoplasmic reticulum (ER)-associated degradation. PMID:37943617 reported the identification of a homozygous SEL1L variant (p.(Cys141Tyr)) in five patients from a consanguineous Slovakian family. These patients presented with not only ERAD-associated neurodevelopmental disorders with onset in infancy (ENDI) syndromes, but infantile-onset agammaglobulinemia with no mature B cells, resulting in frequent infections and early death. All patients exhibited intellectual disability and were unable to speak words and sentences. Although variant in FAR2 gene was also identified in these patients, Sanger sequencing confirmed the segregation of the FAR2 variant with symptoms in patient 2 and FAR2 function is not linked to neurological disorder or agammaglobulinemia (33), leading to its exclusion from being causal for these patients. This gene has been associated with relevant phenotypes in OMIM (MIMs #621067 & #621068), but not yet in Gene2Phenotype.; to: PMID:37943610 reported six patients from three unrelated families with a neurodevelopmental disorder involving developmental delay, intellectual disability, facial dysmorphisms, short stature, microcephaly and seizures. Five patients from two families (Saudi Arabian and Moroccan descent) were identified with homozygous SEL1L variants (p.(Gly585Asp) & p.(Met528Arg)), while an unrelated patient of Italian descent was identified with homozygous HRD1 variant. Although there are additional variants reported in Saudi Arabian patient, SEL1L variant was considered as the potential candidate due to its biological relevance as reported in previous studies in mice. The variants were hypomorphic and impaired endoplasmic reticulum (ER)-associated degradation. PMID:37943617 reported the identification of a homozygous SEL1L variant (p.(Cys141Tyr)) in five patients from a consanguineous Slovakian family. These patients presented with not only ERAD-associated neurodevelopmental disorders with onset in infancy (ENDI) syndromes, but infantile-onset agammaglobulinemia with no mature B cells, resulting in frequent infections and early death. All patients exhibited intellectual disability and were unable to speak words and sentences. Although variant in FAR2 gene was also identified in these patients, Sanger sequencing confirmed the segregation of the FAR2 variant with symptoms in patient 2 and FAR2 function is not linked to neurological disorder or agammaglobulinemia, leading to its exclusion from being causal for these patients. This gene has been associated with relevant phenotypes in OMIM (MIMs #621067 & #621068), but not yet in Gene2Phenotype. |
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| Intellectual disability v9.9 | SEL1L |
Achchuthan Shanmugasundram changed review comment from: PMID:37943610 reported six patients from three unrelated families with a neurodevelopmental disorder involving developmental delay, intellectual disability, facial dysmorphisms, short stature, microcephaly and seizures. Five patients from two families (Saudi Arabian and Moroccan descent) were identified with homozygous SEL1L variants (p.(Gly585Asp) & p.(Met528Arg)), while an unrelated patient of Italian descent was identified with homozygous HRD1 variant. Although there are additional variants reported in Saudi Arabian patient, SEL1L variant was considered as the potential candidate due to its biological relevance as reported in previous studies in mice. The variants were hypomorphic and impaired endoplasmic reticulum (ER)-associated degradation. PMID:37943617 reported the identification of a homozygous SEL1L variant (p.(Cys141Tyr)) in five patients from a consanguineous Slovakian family. These patients presented with not only ERAD-associated neurodevelopmental disorders with onset in infancy (ENDI) syndromes, but infantile-onset agammaglobulinemia with no mature B cells, resulting in frequent infections and early death. All patients exhibited intellectual disability and were unable to speak words and sentences. This gene has been associated with relevant phenotypes in OMIM (MIMs #621067 & #621068), but not yet in Gene2Phenotype.; to: PMID:37943610 reported six patients from three unrelated families with a neurodevelopmental disorder involving developmental delay, intellectual disability, facial dysmorphisms, short stature, microcephaly and seizures. Five patients from two families (Saudi Arabian and Moroccan descent) were identified with homozygous SEL1L variants (p.(Gly585Asp) & p.(Met528Arg)), while an unrelated patient of Italian descent was identified with homozygous HRD1 variant. Although there are additional variants reported in Saudi Arabian patient, SEL1L variant was considered as the potential candidate due to its biological relevance as reported in previous studies in mice. The variants were hypomorphic and impaired endoplasmic reticulum (ER)-associated degradation. PMID:37943617 reported the identification of a homozygous SEL1L variant (p.(Cys141Tyr)) in five patients from a consanguineous Slovakian family. These patients presented with not only ERAD-associated neurodevelopmental disorders with onset in infancy (ENDI) syndromes, but infantile-onset agammaglobulinemia with no mature B cells, resulting in frequent infections and early death. All patients exhibited intellectual disability and were unable to speak words and sentences. Although variant in FAR2 gene was also identified in these patients, Sanger sequencing confirmed the segregation of the FAR2 variant with symptoms in patient 2 and FAR2 function is not linked to neurological disorder or agammaglobulinemia (33), leading to its exclusion from being causal for these patients. This gene has been associated with relevant phenotypes in OMIM (MIMs #621067 & #621068), but not yet in Gene2Phenotype. |
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| Intellectual disability v9.9 | SEL1L | Achchuthan Shanmugasundram reviewed gene: SEL1L: Rating: GREEN; Mode of pathogenicity: None; Publications: 37943610, 37943617; Phenotypes: Neurodevelopmental disorder with hypotonia, poor growth, dysmorphic facies, and agammaglobulinemia, OMIM:621068, ?Neurodevelopmental disorder with poor growth, absent speech, progressive ataxia, and dysmorphic facies, OMIM:621067; Mode of inheritance: BIALLELIC, autosomal or pseudoautosomal | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability v8.124 | MAG | Sarah Leigh Added comment: Comment on publications: PMID: 39336794 was identified by the Genomics England Applied Machine Learning (ML) team in a Biocuration-ML project for identifying new gene-disease associations using Natural Language Processing (NLP) and Generative AI techniques. | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability v8.124 | MAG | Sarah Leigh Publications for gene: MAG were set to 39336794 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability v8.123 | MAG | Sarah Leigh Classified gene: MAG as Amber List (moderate evidence) | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability v8.123 | MAG | Sarah Leigh Gene: mag has been classified as Amber List (Moderate Evidence). | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability v8.122 | MAG |
Sarah Leigh gene: MAG was added gene: MAG was added to Intellectual disability. Sources: Literature Q1_25_ promote_green tags were added to gene: MAG. Mode of inheritance for gene: MAG was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: MAG were set to 39336794 Phenotypes for gene: MAG were set to Spastic paraplegia 75, autosomal recessive, OMIM:616680; hereditary spastic paraplegia 75, MONDO:0014729 Review for gene: MAG was set to GREEN Added comment: AT least six MAG variants have been associated with Spastic paraplegia 75, autosomal recessive, OMIM:616680 in at least five unrelated cases (PMID: 24482476; 26179919; 27606346; 31402626; 39336794). It would appear that intellectual disability is a common feature in cases of OMIM:616680, although this may be mild to moderate. Sources: Literature |
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| Intellectual disability v8.30 | GNAI2 |
Arina Puzriakova edited their review of gene: GNAI2: Added comment: Ham et al. (2024) (PMID: 39298586) - 20 individuals from 18 unrelated families with heterozygous GOF missense variants in GNAI2 and highly heterogenous clinical presentations. Most commonly observed was disruption of the immune system, with almost 90% of cases exhibiting recurrent, unusual, and/or severe infections. Other features include birth defects, growth abnormalities, neurodevelopmental delay progressing to ID at later stages, brain structural abnormalities and various dysmorphic features. Authors dubbed the syndromic disorder with the acronym MAGIS - Midline malformations of the brain, Anterior hypopituitarism, Growth retardation, Immunodeficiency/immunodysregulation, Skeletal abnormalities.; Changed publications to: 31036916, 27787898, 39298586 |
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| Intellectual disability v8.6 | PI4K2A |
Tracy Lester gene: PI4K2A was added gene: PI4K2A was added to Intellectual disability. Sources: NHS GMS Mode of inheritance for gene: PI4K2A was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: PI4K2A were set to 30564627; 35880319; 32418222 Phenotypes for gene: PI4K2A were set to Intellectual disability; developmental delay; seizures Penetrance for gene: PI4K2A were set to unknown Review for gene: PI4K2A was set to GREEN Added comment: At least three cases have been reported with biallelic variants in this gene and a neurodevelopmental disorder 35880319 - Two patients with PI4K2A deficiency (homozygous variants) were identified by exome sequencing, presenting with developmental and epileptic-dyskinetic encephalopathy. Neuroimaging showed corpus callosum dysgenesis, diffuse white matter volume loss, and hypoplastic vermis. In addition to NDD, we observed recurrent infections and death at toddler age. 30564627 - We report a family of Saudi Arabian ancestry with two children presenting with global developmental delay, dystonia, disturbed sleep, and heat intolerance. By genome sequencing, we identified a nonsense variant in the first exon of PI4K2A that was homozygous in both affected individuals and was absent from, or heterozygous in, seven unaffected siblings. 32418222 - a homozygous missense variant of uncertain significance was suggested to be responsible for some features in a case with NDD and metabolic cutis laxa. Sources: NHS GMS |
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| Intellectual disability v5.377 | CLCN6 |
Sarah Leigh gene: CLCN6 was added gene: CLCN6 was added to Intellectual disability - microarray and sequencing. Sources: Other Mode of inheritance for gene: CLCN6 was set to MONOALLELIC, autosomal or pseudoautosomal, imprinted status unknown Publications for gene: CLCN6 were set to 29667327; 26658788; 25794116; 21107136; 33217309; 16950870 Phenotypes for gene: CLCN6 were set to Neurodegeneration, childhood-onset, hypotonia, respiratory insufficiency and brain imaging abnormalities OMIM:619173 Review for gene: CLCN6 was set to RED Added comment: Sources: Other |
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| Intellectual disability v3.1677 | ZMYND8 |
Konstantinos Varvagiannis gene: ZMYND8 was added gene: ZMYND8 was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: ZMYND8 was set to MONOALLELIC, autosomal or pseudoautosomal, imprinted status unknown Publications for gene: ZMYND8 were set to 35916866; 32530565 Phenotypes for gene: ZMYND8 were set to Delayed speech and language development; Motor delay; Intellectual disability; Abnormality of cardiovascular system morphology; Hearing abnormality; Abnormality of vision; Abnormality of the face; Seizures Penetrance for gene: ZMYND8 were set to unknown Review for gene: ZMYND8 was set to GREEN Added comment: Dias et al (2022 - PMID: 35916866) describe the phenotype of 11 unrelated individuals with monoallelic de novo (or suspected de novo) missense (N=9) or truncating (N=2) ZMYND8 variants. One of these subjects was previously reported by Suzuki et al (2020 - PMID: 32530565). Features included speech delay/language difficulties (9/11), motor delay (9/11), ID (in 10/11 - profound in 1, moderate in 2), CHD (7/11 - PDA, VSD, ASD, pulmonary stenosis, etc), hearing or vision impairment (7/11). Seizures were reported in few (in text 5/11, table 2/11). Variable non-familial facial features were present in (9/11). As the authors discuss, ZMYND8 encodes a multidomain protein playing a role in transcription regulation, chromatin remodeling, regulation of super enhancers, DNA damage response/tumor suppression. The protein is broadly expressed in brain and shows highest expression in early development. Molecular modeling and/or a yeast two-hybrid system were suggestive of disrupted interaction of ZMYND8 with Drebrin (missense variants in PWWP domain) or GATAD2A (variants in MYND domain). Neuronal Zmynd8 knockdown in Drosophila resulted in deficits in habituation learning. Sources: Literature |
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| Intellectual disability v3.1677 | ZMYND15 |
Konstantinos Varvagiannis gene: ZMYND15 was added gene: ZMYND15 was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: ZMYND15 was set to MONOALLELIC, autosomal or pseudoautosomal, imprinted status unknown Publications for gene: ZMYND15 were set to 35916866; 32530565 Phenotypes for gene: ZMYND15 were set to Delayed speech and language development; Motor delay; Intellectual disability; Abnormality of cardiovascular system morphology; Hearing abnormality; Abnormality of vision; Abnormality of the face; Seizures Penetrance for gene: ZMYND15 were set to unknown Review for gene: ZMYND15 was set to GREEN Added comment: Dias et al (2022 - PMID: 35916866) describe the phenotype of 11 unrelated individuals with monoallelic de novo (or suspected de novo) missense (N=9) or truncating (N=2) ZMYND8 variants. One of these subjects was previously reported by Suzuki et al (2020 - PMID: 32530565). Features included speech delay/language difficulties (9/11), motor delay (9/11), ID (in 10/11 - profound in 1, moderate in 2), CHD (7/11 - PDA, VSD, ASD, pulmonary stenosis, etc), hearing or vision impairment (7/11). Seizures were reported in few (in text 5/11, table 2/11). Variable non-familial facial features were present in (9/11). As the authors discuss, ZMYND8 encodes a multidomain protein playing a role in transcription regulation, chromatin remodeling, regulation of super enhancers, DNA damage response/tumor suppression. The protein is broadly expressed in brain and shows highest expression in early development. Molecular modeling and/or a yeast two-hybrid system were suggestive of disrupted interaction of ZMYND8 with Drebrin (missense variants in PWWP domain) or GATAD2A (variants in MYND domain). Neuronal Zmynd8 knockdown in Drosophila resulted in deficits in habituation learning. Sources: Literature |
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| Intellectual disability v3.1648 | CNNM2 | Eleanor Williams Phenotypes for gene: CNNM2 were changed from Hypomagnesemia, seizures, and mental retardation 616418 to Hypomagnesemia, seizures, and mental retardation, OMIM:616418; Hypomagnesemia, seizures, and mental retardation, MONDO:0014631 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability v3.1593 | RYR2 |
Dmitrijs Rots gene: RYR2 was added gene: RYR2 was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: RYR2 was set to MONOALLELIC, autosomal or pseudoautosomal, NOT imprinted Publications for gene: RYR2 were set to 30170228 Penetrance for gene: RYR2 were set to Incomplete Review for gene: RYR2 was set to GREEN Added comment: In a large cohort of RYR2-related CPVT, 8% of individuals (34 of 421) were having ID of various severity. Funcional data suggest that highly damaging RYR2 variants underlie ID. Sources: Literature |
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| Intellectual disability v3.1580 | DROSHA |
Konstantinos Varvagiannis gene: DROSHA was added gene: DROSHA was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: DROSHA was set to MONOALLELIC, autosomal or pseudoautosomal, imprinted status unknown Publications for gene: DROSHA were set to 35405010 Phenotypes for gene: DROSHA were set to Global developmental delay; Intellectual disability; Seizures; Cerebral white matter atrophy; Abnormality of the corpus callosum; Abnormality of movement; Stereotypic behavior; Abnormality of head or neck; Short foot Penetrance for gene: DROSHA were set to unknown Mode of pathogenicity for gene: DROSHA was set to Loss-of-function variants (as defined in pop up message) DO NOT cause this phenotype - please provide details in the comments Review for gene: DROSHA was set to AMBER Added comment: Profound DD, ID and seizures have been reported in 2 unrelated subjects with de novo missense variants. The gene has a role in miRNA biogenesis. Both variants described have been shown to have effect on DROSHA's function in Drosophila / C. elegans (partial loss-of-function vs possibility of antimorphic effect discussed || in gnomAD several individuals with LoF alleles / Z=3.98 – pLI : 0.09). There is currently no DROSHA-related phenotype in OMIM, G2P, SysNDD. In PanelApp Australia the gene has amber rating in genetic epilepsy and microcephaly panels (not currently included in the ID one). Consider inclusion in the current panel with amber rating. Also consider inclusion in other possibly relevant panels (given postnatal microcephaly, abn. corpus callosum, progressive white matter atrophy, etc) [ NOT added ] ----- Barish, Senturk, Schoch et al (2022 - PMID: 35405010) describe the phenotype of 2 unrelated individuals with de novo missense DROSHA variants. Features included generalized hypotonia, postnatal microcephaly (-2,6 and -6 SD), feeding difficulties, profound DD and ID, seizures, abnormal movements (choreoathetosis / stereotypic movements), variable respiratory symptoms (in one case episodes of hyperventilation/apnea), cardiovascular or skeletal findings. Brain MRI demonstrated white matter atrophy and thin corpus callosum in both. Brachycephaly with broad face as well as short feet were also among the shared features. Both were investigated by trio ES/GS which were otherwise non diagnostic and without other candidate variants. The 1st individual harbored a de novo htz missense DROSHA variant (c.3656A>G/p.Asp1219Gly) while the 2nd subject had another missense variant (c.4024C>T/p.Arg1342Trp) [NM_013235.4] confirmed by Sanger seq. DROSHA (on 5p13.3) encodes a ribonuclease, subunit of the microprocessor complex, involved in miRNA biogenesis. Specifically, miRNAs are transcribed as part of pri-miRNAs (primary-miRNAs) which are cleaved to pre-miRNAs (precursor-miRNAs) in the nucleus by DROSHA (and its partner DGCR8 or Pasha) and then exported to the cytoplasm for further processing. Cleavage of pre-miRNAs by DICER1 generates mature miRNAs subsequently loaded to the RISC (RNA-induced silencing) complex which uses miRNA as template for recognition and cleavage of complementary mRNA with RNAse. As the authors discuss, miRNA defects have a well-established role in development of model organisms e.g. (several Refs. provided): - in C. elegans miRNA mutants causing lethality, developmental arrest and heterochronicity - in Drosophila playing a role in the development of ovary, eye, nervous system etc. - in mice mRNAs play a role in BMP and TGF-beta signaling while neuronal loss of miRNA processing leads to neurodegeneration/anatomical defects. Feingold syndrome 2 is the single Mendelian disease associated to date with miRNAs, through deletion of a cluster containing 6 MIR genes. miRNA dysregulation is also observed in Rett syndrome - and DROSHA implicated in the pathogenesis of the syndrome - as MECP2 and FOXG1 are cofactors of the microprocessor complex regulating processing of miRNA. One of the individuals here reported had a clinical diagnosis of Rett spectrum while both had overlapping features with Rett s. Studies of DROSHA-dependent miRNAs in fibroblasts from one individual revealed significantly altered expression of mature miRNA (e.g. increased miR98, a miRNA with reduced expression in studies of somatic DROSHA variants) although this was not likely due to processing errors (given only a modest decrease of precursor miRNAs). Previous studies have demonstrated that drosha (the Drosophila ortholog) null mutants die during post-embryonic development with 100% lethality before adulthood (3rd instar larval stage/beginning of pupariation). Mosaic flies with mutant eyes are small-eyed, while viable hypomorphic alleles display synaptic transmission defects (several Refs provided). Here, homozygous flies for null alleles died at the end of 3rd instar larval stage/beginning of pupariation, while loss of drosha resulted in lack of imaginal disc tissue (which surrounds the larval brain) and severely reduced brain size, the latter similar to the microcephaly phenotype. [To the best of my understanding] introduction of a mutated genomic rescue construct (carrying similar substitutions as those observed in human subjects) in eye-specific drosha null (W1123X) flies was partially able to rescue eye/head size for wt or Asp1219Gly (human:Asp1084Gly) suggesting that the latter is a partial LoF allele. Arg1210Trp (corresponding to human Arg1342Trp) was able to rescue the eye phenotype and was not damaging to the function in the specific assay. Drosha expression levels were similar for genomic rescue flies either for wt or for the Asp-Gly variant suggesting that the effect was not due to expression levels (but rather function). Expression of mature miRNAs known to be regulated by Drosha were not affected when comparing wildtype larvae with genomic construct for wt or Asp1084Gly. Upon expression of human cDNA using GAL4/UAS system in drosha mutant (null) eye clones, the reference partially rescued the eye size defect, Asp-Gly behaved as partial loss-of-function allele (~50% function compared to ref), while the Arg-Trp variant was shown to behave as a weaker loss-of-function allele. The authors generated eye-specific drosha mutant clones to study the aging adult eye using ERG recordings. While null mutants display almost no response to light (7- and 20-day old flies), wt genomic rescue was shown to rescue ERG responses, Asp-Gly variant had significant defects (at both 7 and 20 days) and the Arg-Trp had defects approaching statistical significance only at the age of 20 days. Overall these data suggested that Arg-Trp had less severe effect compared to Asp-Gly (as above) while both variants led to progressive neuronal dysfunction. Using CRISPR/Cas9 the authors generated C.elegans knock-ins for a variant analogous to the Asp1219Gly human one. Homozygous animals were inviable at larval stages, displayed a heterochronic phenotype (heterochronicity : development of cells or tissues at an abnormal time relative to other unaffected events in an organism / miRNAs are known to be involved in the heterochronic gene pathway) while this variant was deleterious to the Drosha's ability to process miRNAs. Sources: Literature |
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| Intellectual disability v3.1558 | SLC35B2 |
Konstantinos Varvagiannis gene: SLC35B2 was added gene: SLC35B2 was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: SLC35B2 was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: SLC35B2 were set to 35325049 Phenotypes for gene: SLC35B2 were set to Abnormality of the skeletal system; Short long bone; Short stature; Abnormality of epiphysis morphology; Scoliosis; Multiple joint dislocation; Global develpmental delay; Intellectual disability; CNS hypomyelination; Abnormality of the corpus callosum; Cerebral atrophy; Abnormality of the amniotic fluid Penetrance for gene: SLC35B2 were set to Complete Review for gene: SLC35B2 was set to AMBER Added comment: 2 unrelated individuals with biallelic SLC35B2 variants have been reported. DD and ID were part of the phenotype. There is currently no associated phenotype in OMIM/G2P/SysID. The gene has amber rating in the leukodystrophies panel of PanelApp Australia. Consider inclusion in the current panel (or other possibly relevant ones eg. for skeletal disorders, short stature, white matter disorders, corpus callosum, etc) with amber rating. --- Guasto et al (2022 - PMID:35325049) report 2 unrelated individuals with biallelic SLC35B2 variants. SLC35B2 encodes solute carrier family 35 (3'-phosphoadenosine 5'-phosphosulfate (PAPS) transporter), member B2. The protein is located in the Golgi membrane and serves as transporter of the activated nucleotide sulfate PAPS from the cytosol, where it is synthesized to the Golgi lumen. Another PAPS transporter is encoded by SLC35B3. In the Golgi apparatus PAPS serves as substrate of sulfotransferases for the addition sulfate to the covalently attached GAG chains of proteoglycans (PGs). The phenotype corresponded to a chondrodysplasia manifesting as severe pre- and postnatal growth retardation (height <-4 SD and -8 SD), early scoliosis, multiple joint dislocations (in one). There was severe DD affecting motor and expressive language development with associated ID. Brain imaging was suggestive of hypomyelinating leukodystrophy with thin corpus callosum and cerebral atrophy. One individual had a cleft palate in the context of Pierre Robin sequence. Both individuals were investigated with exome sequencing. The first individual - born to consanguineous parents - was homozygous for an in-frame del (NM_178148.3:c.1218_1220del, p.Leu407del) with Sanger sequencing confirming the variants, and heterozygosity in parents and 2 unaffected sibs. There was an initially identified hmz CUL7 variant (for 3M syndrome), which was not felt sufficient to explain the severity of the phenotype and notably ID. The 2nd proband was homozygous for a fs variant (c.1224_1225delAG / p.Arg408SerfsTer18 - leading to loss of the last 8 amino acids) occurring in the context of uniparental isodisomy [iUPD(6)] spanning the complete chr6 based on the exome data. Among the evidence presented for SLC35B2 and the variants : - SLC35B2 has high mRNA expression in fetal and adult mouse brain and other tissues. - Upon qPCR analysis of mRNA expression in human brain samples, the gene had expression across the brain (frontal lobe grey matter, subcortical frontal white matter/cerebellum). - High expression was shown upon analysis of mouse brain single cell RNA data (EMBL) in oligodendrocytes and microglial cells. - RT-PCR on mRNA from skin fibroblasts (both individuals) revealed significant decrease of SCL35B2 mRNA levels compared to controls. - Transfection of C-terminal c-myc tagged wt or mutant proteins in HEK293F cells, followed by western blotting did not reveal significant difference at the protein level. Wt SLC35B2 localized at the Golgi apparatus as suggested by colocalization with GM130 marker. The 2 variants however displayed only partial colocalization (/loss of localization specificity) with diffuse signal in the cell. - Chondroitin sulfate disaccharide sulfation was decreased upon HPLC disaccharide analysis in patient fibroblasts and bikunin (a circulating proteoglycan in blood) electrophoretic pattern in patient sera. - Disorders due to variants in genes implicated in proteoglycan biogenesis (e.g. XYLT1, B3GALT6, CHSY1) are associated with skeletal/connective tissue manifestations with DD/ID. - C-elegans model lacking pst-1 (SLC35B2 ortholog) provides support that the protein is required for migration, axonal guidance, and presynaptic development in a subset of neurons. - dsm-1 - the rat ortholog - is expressed in rat brain in D-serine and NMDA receptor rich regions. When expressed in Xenopus oocytes it accelerated the efflux of D-serine (a co-agonist for NMDA receptor). - Variants in other members of SLC superfamily (e.g. SLC17A5, SLC35A3, SLC29A3, SLC35A2) have been associated with brain-bone phenotypes. Sources: Literature |
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| Intellectual disability v3.1544 | DTYMK |
Konstantinos Varvagiannis gene: DTYMK was added gene: DTYMK was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: DTYMK was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: DTYMK were set to Global developmental delay; Intellectual disability; Microcephaly; Seizures; Global brain atrophy; Cardiorespiratory arrest Phenotypes for gene: DTYMK were set to 31271740; 34918187; 35346037 Penetrance for gene: DTYMK were set to Complete Review for gene: DTYMK was set to GREEN Added comment: 4 individuals (from 3 families) harboring biallelic DTYMK pathogenic variants have been reported. Consider inclusion in the current panel with green rating given consistent and relevant phenotype and evidence provided to date [effect of variants (LoF), pathogenesis, similar phenotypes in zebrafish model, etc]. Relevant studies are summarized below. ---- Lam et al (2019 - PMID: 31271740) described two siblings aged 25m and 7y, harboring biallelic DTYMK variants. The phenotype consisted of hypotonia, congenital microcephaly, DD, severe ID. Other shared features included raised serum lactate, pyruvate and alanine. The phenotype was more pronounced in the younger one (epilepticus during febrile illness, epilepsy on multiple anti-convulsants, evidence of regression, etc). Brain MRI revealed marked cerebral atrophy among the findings while a lactate peak was present in spectroscopy. The elder brother developed an episode of sudden onset coma with respiratory failure at the age of 7y. Quartet WES identified compound heterozygosity for a fs and a missense DTYMK variant (NM_012145.3:c.287_320del / p.Asp96Valfs*8 - c.295G>A / p.Ala99Thr). There were no additional findings. Previous genetic panel analysis for epilepsy was unremarkable for the 1st sib. There are two pathways for synthesis of dNTPs, the de novo pathway operating in the cytosol only and the salvage operating in both cytosol and mitochondria. DTYMK encodes (deoxy)thymidylate kinase which catalyzes conversion (phosphorylation) of dTMP to dTDP - a step right after convergence of both pathways - in the dTTP synthesis pathway. Mutations in TK2, an enzyme phosphorylating thymidine in mitochondria to dTMP have been associated with mitochondrial DNA depletion syndrome (MDDS). Given this and as the 2 sibs had raised serum lactate and pyruvate, the authors performed in silico analyses to calculate mtDNA/nDNA ratio dividing the respective read depths for mitochondrial and nuclear DNA obtained from WGS data of the two sibs (blood). This ratio was shown to be reduced in the more severely affected sib (65.5% of control) although this was not the case for the mildly affected brother (114.6%). As a control a non-MDDS mitochondrial cytopathy sample (corresponding to m.8993T>G) was used. The respective ratio which was calculated for a known POLG-related MDDS case was 15.6%. ---- Vanoevelen et al (2022 - PMID: 34918187) describe two unrelated children with hypotonia, absence of developmental progress, microcephaly, seizures (recurrent febrile seizures/myoclonic jerks). Severe cerebral atrophy (with unaffected cerebellum) was observed upon brain imaging. Other findings included puffy body/extremities. Both had complications following respiratory illness leading to demise. CNS pathology in the 1st individual revealed massive neuronal dropout, with sparing of dentate nucleus and brainstem. CMA in both cases was normal. This was also the case for extensive metabolic investigations (which provided no evidence of eventual mitochondrial dysfunction). WES revealed compound heterozygosity for 2 missense variants in the first individual (NM_012145.3:c.382G>A - p.Asp128Asn and c.242C>T - p.Pro81Leu). The second individual, born to consanguineous parents, was homozygous for c.242C>T / p.Pro81Leu. In silico predictions varied although each variant were (mostly) suggestive of a deleterious effect. Variants were both ultrarare without homozygotes in ExAC,. The authors generated a dtymk ko zebrafish model (hmz for a frameshift variant). Zebrafish exhibited markedly smaller eyes and pericardiac edema (3dpf-), twitching movements somewhat reminiscent of epilepsy (at 3dpf), prominent edema of brain and intestine. Head size was significantly smaller at a timepoint prior to brain edema (also after correction for length). Histology provided evidence of empty spaces in brain, suggestive of neurodegeneration, with high amounts of apoptotic cells. dTMPK activity was measured in zebrafish (at 5dpf) as well as in fibroblasts from one individual and in both cases, it was barely detectable and significantly lower compared to wt/htz zebrafish or to the activity in fibroblasts from the parents of the individual tested. In fibroblasts from the same individual with comparison to his parents, the authors demonstrated that DNA replication was impaired (using pulse-EdU staining to quantify cells in S-phase). Assessment of cell proliferation in the brain of dtymk ko zebrafish using phospo-Ser10-Histone H3 (pH3) staining was suggestive of severe proliferation defects in forebrain. Impaired biosynthesis of nucleotides for DNA synthesis/repair would be predicted to result in nucleotide pool imbalance, leading to incorporation of ribonucleotides in genomic DNA with - in turn - impairment of DNA replication and genomic instability (sensitivity to strand breakage). In line with this, genomic DNA of ko zebrafish following alkaline hydrolysis and alkaline gel electrophoresis was shown to migrate at lower position and to be more fragmented indicating increased sensitivity (due to incorporation of ribonucleotides). Visualization of DNA breakage by γH2AX staining, following UV-irradiation of zebrafish embryos revealed persistence of elevated γH2AX levels and DNA damage response signaling, interpreted as increase in unrepaired DNA breaks. mtDNA copy numbers in fibroblasts from the affected individual was somewhat but not significantly lower compared to his parents. Importantly, the copy numbers were similar to controls (N=5) which overall does not support mtDNA depletion as a consequence of DTYMK deficiency. Integrity of mtDNA did not appear to be compromised , with the mitochondrial genome migrating at the expected length of 16,5 kb with no indications of mtDNA deletions for both affected individual and his parents. Activity of the mitochondrial respiratory complexes I-V in fibroblasts from the affected individual was comparable to that of his parents. Overall, there was no evidence for mtDNA depletion (although not studied in muscle biopsy) while functional studies failed to demonstrate mitochondrial dysfunction. The authors discuss other disorders of impaired dTTP metabolism due to mutations in TYMP, RRM2B or CAD. ------ In a recent study using zebrafish model, Hu Frisk et al (2022 - PMID: 35346037) further demonstrate that Dtymk is essential for neurodevelopment providing evidence for expression of a compensatory thymidylate kinase-like enzyme at later stages of development (explaining survival of ko dtymk zebrafish despite the central role of this enzyme in dTTP generation). [Not further reviewed] Sources: Literature |
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| Intellectual disability v3.1529 | SLC38A3 |
Konstantinos Varvagiannis gene: SLC38A3 was added gene: SLC38A3 was added to Intellectual disability. Sources: Literature,Other Mode of inheritance for gene: SLC38A3 was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: SLC38A3 were set to 34605855 Phenotypes for gene: SLC38A3 were set to Infantile axial hypotonia; Global developmental delay; Intellectual disability; Seizures; Spasticity; Microcephaly; Cerebral atrophy; Cerebellar atrophy; Abnormality of the corpus callosum; Dysphagia; Constipation; Increased serum lactate; Hyperammonemia Penetrance for gene: SLC38A3 were set to Complete Review for gene: SLC38A3 was set to GREEN Added comment: Marafi et al (2021 - PMID: 34605855) describe the phenotype of 10 individuals, belonging to 7 families (6/7 consanguineous), harboring biallelic deleterious SLC38A3 variants. One subject (from fam3) was previously reported in the context of a larger cohort of consanguineous families investigated with exome sequencing (2017, PMID: 31130284). The phenotype overall corresponded to a DEE and features included axial hypotonia (10/10), severe global DD or ID (10/10), seizures (8/10, onset : 1w-15m, NOT observed in 2/10 aged 1y3m and 4y | s. types: tonic-clonic in 3/8, tonic 2/8, focal 2/8 with secondary generalization, myoclonic 1/8, gelastic 1/8 | EEG burst-suppression, hypsarrhythmia in few). Microcephaly was observed in (8/10) and was more commonly postnatal and/or progressive. Variable abnormalities were observed upon brain imaging incl. cerebral (5/10) or cerebellar atrophy (2/10) and abnormal CC (6/10), abnormal myelination for age (6/10). Other phenotypes included visual impairment (9/10), peripheral hypertonia (8/9) constipation (8/9) and dysphagia (7/9), FTT (4/8), movement disorder (3/10). Metabolic studies indicated (transient) elevation of lactate (7/8 - also pyruvate in 2) and elevated plasma ammonia (4/7). Individuals from the 1st family were investigated with ES, and the SLC38A3 splice site variant (NM_006841.6:c.855+1G>T) was the most likely candidate, additional SNVs not contributing to the NDD phenotype. Other affected subjects were ascertained through GeneMatcher/collaborations. In total, 3 different missense and 4 pLoF (1 fs, 2 nonsense, 1 splicing) variants were identified with individuals from 2 families being hmz or cmd htz for missense variants. Variants were absent/ultrarare with no homozygotes in public/in-house databases with several in silico predictions in favor of a deleterious effect. Regions of AOH (around SLC38A3/total) are provided for some individuals/families. Sanger sequencing was used for confirmation and segregation studies (apart from carrier parents in 7/7 fam, 11 unaffected sibs tested in 6/7 fam). The solute carrier (SLC) superfamily of transmembrane transporters - highly expressed in mammalian brain - is involved in exchange of amino-acids (AAs), nutrients, ions, neurotransmitters and metabolites etc across biological membranes with >100 SLC-encoding genes associated with NDDs. SLC38A3 specifically encodes SNAT3, a sodium-coupled neutral amino-acid transporter, principal transporter of Asn, His, Gln (precursor for GABA and glutamate), expressed in brain, liver, kidney, retina and pancreas. In the brain, it localizes to peri-synaptic astrocytes playing an important role in glutamate/GABA-glutamine cycle. While the pLoF variants are predicted to undergo NMD or result in non-functional protein, protein modelling suggested that missense ones affect protein activity or stability. Biochemical and metabolic screening was carried out for several individuals with plasma AAs reported normal (10/10), urinary OAs normal in 9/9, CSF AAs (incl. GABA/glutamine) normal in 2 sibs, CSF lactate normal in 1 indiv. studied. As discussed above plasma ammonia was elevated in 4/7 (2 fam), and 7/10 had elevated lactate and/or pyruvate (2/7). Untargeted metabolomic profiles performed in biofluids (plasma from 3 subjects, CSF:1, urine:1) were suggestive of altered AA and nitrogen metabolism. In particular, alterations in levels of AA known to be transported by SNAT3 were found. 676 molecules overall showed deviation in plasma samples, 630 in urine and 241 in CSF (albeit with no consistent pattern). Perturbations in several biochemical pathways were shown to occur (incl. Gln-,Asn- and His- pathways). Slc38a3-/- mice have reductions in brain glutamate and GABA neurotransmitters in homogenized brain tissue (GABA analytes being normal in plasma samples or the single CSF sample available from affected subjects). Snat3-deficient mice had elevation of plasma urea and normal ammonia levels (urea was low in all human samples and ranged from -2 to -3.5 SD in plasma, ammonia was elevated in 4/7). Slc38a3-/- mice have impaired growth, lethargy and ataxic gait, altered plasma AAs, normal glutamine in plasma with abundance in brain and exhibit early lethality. Plasma AAs were normal in 4 affected individuals, impaired growth observed in 4 and gait impairment was observed in 9/10. Hypoglycemia, previously reported in Slc38a3-/- mice, was not observed in any of the patients although this is presumably explained by diet/feeding intervals with abnormalities in pentose phosphate pathway in one individual hypothesized to be reflective of abn. glucose metabolism. The human phenotypes of microcephaly and seizures were not observed in mice. For mouse studies PMIDs cited by the authors : 27362266, 26490457. There is currently no SLC38A3-related phenotype reported in OMIM. In G2P this gene is incl. in the DD panel (biallelic, confidence: strong, SLC38A3-associated epileptic encephalopathy). SLC38A3 is listed among the primary ID genes in SysID. In PanelApp Australia, SLC38A3 is included with green rating in the epilepsy, ID and microcephaly panels. Consider inclusion with green rating (10 individuals, 7 families, 7 variants, role of SLCs and SLC38A3, alterations in AA/nitrogen metabolism etc) or amber rating (if discordances with mouse model considered). Please consider inclusion in other panels e.g. for microcephaly, CC abnormalities, metabolic disorders, etc. Sources: Literature, Other |
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| Intellectual disability v3.1520 | HIST1H4D |
Konstantinos Varvagiannis gene: HIST1H4D was added gene: HIST1H4D was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: HIST1H4D was set to MONOALLELIC, autosomal or pseudoautosomal, imprinted status unknown Publications for gene: HIST1H4D were set to 35202563 Phenotypes for gene: HIST1H4D were set to Global developmental delay; Intellectual disability; Microcephaly; Growth abnormality; Abnormality of the face Penetrance for gene: HIST1H4D were set to Complete Mode of pathogenicity for gene: HIST1H4D was set to Loss-of-function variants (as defined in pop up message) DO NOT cause this phenotype - please provide details in the comments Review for gene: HIST1H4D was set to AMBER Added comment: Histone H4 is a core component of the nucleosome, the basic repeating unit of eukaryotic chromatin. Each nucleosome consists of ~150 bp of DNA wrapped around a histone octamer. Each histone octamer is composed of 2 copies of each of the histones H2A, H2B, H3, H4. This organization is important for DNA replication, transcription and repair. There are 14 canonical histone H4 genes in the human genome, which despite being different at the nucleotide level encode an identical protein. These cluster in 3 genomic loci. Their transcription is independently regulated with differing expression during brain development and in human tissues. Histone H4 forms a dimer with H3 (which however has variant isoforms linked to specific cellular processes). Pathogenic variants in genes encoding H4 have been reported in several individuals. Irrrespective of the gene for H4 involved, all patients presented with highly overlapping features, DD and ID being universal. Available reports to date concern : - H4C3/HIST1H4C (9 subjects - PMID: 28920961, 35202563), - H4C11/HIST1H4J (1 subject - PMID: 31804630, 35202563), - H4C4/HIST1H4D (1 subject - PMID:35202563), - H4C5/HIST1H4E (17 subjects - PMID: 35202563), - H4C6/HIST1H4F (1 subject - PMID: 35202563), - H4C9/HIST1H4I (3 subjects - PMID: 35202563). Variants in all cases were missense SNVs, occurring (in almost all cases) as dn variants and affecting the same residue in the same and/or different H4 genes (details for clusters below). Eg. Arg45Cys was a recurrent variant for H4C5 (>=7 subjects), while variants affecting Arg40 have been reported in H4C4, H4C5, H4C9, H4C11 (7 subjects overall). Zebrafish studies for all genes reported have included most - if not all - patient variants and recapitulate features observed in affected individuals (head size/structure and growth). Additional studies specificaly for H4C3/HIST1H4C have been performed in patient fibroblasts (demonstrating among others transcriptional dysregulation) and zebrafish (accumulation of DSBs, increased apoptosis in head/tail, abn. cell cycle progression). Note that the nomenclature for variants - at the protein level - used in literature commonly takes into consideration cleavage of Met1, thus the numbering may not correspond to the HGVS one. Relevant entries exist in OMIM, G2P and SysID only for H4C3/HIST1H4C (Tessadori-van Haaften neurodevelopmental syndrome 1, #619758) and H4C11/HIST1H4J (?Tessadori-van Haaften neurodevelopmental syndrome 2, #619759) but not for other genes. Rating in PanelApp Australia - ID Panel : HIST1H4C Green, H4J Amber, H4D Amber, H4E Green, H4F Amber, H4I Green. Please consider inclusion in other possibly relevant panels (microcephaly, short stature/FTT, etc). ------ Initial work from Tessadori et al (incl. DDD study, 2017 - PMID:28920961) identified monoallelic missense SNVs affecting the same residue of H4C3 (HIST1H4C), in 3 individuals from 2 families. [c.274A>C/ HGVS p.(Lys92Gln) dn in 1 subject and c.275A>C/ HGVS p.(Lys92Arg) inherited from unaffected mosaic parent]. Individuals from both families having relevant age had intellectual disability (2/2 - 2 families). Other features incl. growth delay (3/3) and microcephaly (3/3). Expression of the variants in zebrafish severely affected structural development recapitulating the patient phenotypes (microcephaly and short stature). RNA sequencing in fibroblasts from 2 unrelated patients and a control, revealed that expression of H4C3 variants was similar to wt. The authors estimated that ~8% of H4 cDNA molecules contained the variant. LC-MS/MS analysis suggested that the mutant protein was present in nucleosomes at a level of 1-2% while RNA-seq identified 115 differential expressed genes, with enrichment for relevant procedures (chr. organization, histone binding, DNA packaging, nucleosomal organization, cell cycle). Post-translational modifications of Lys92 (H4K91) are highly conserved and have been previously associated with processes from chromatin assembly , DNA damage sensitivity, etc. Post-translational marks on Lys92 (K91) were absent in patient derived cells as a result of each variant. Zebrafish models for both variants were suggestive for accumulation of double strand breaks (DSBs) more visible in heads and tails of larvae. Embryos expressing mutants displayed increased apoptosis in head and tail. Additional studies in larvae were suggestive of abnormal cell cycle progression (rel. increase in cellls in S/G2/M phase, increased occurrence of activated CHK2 with p53 stabilization) applying to both variants studied. ------ In a subsequent publication, Tessadori et al. (2020 - PMID: 31804630) described the phenotype of a 14 y.o. boy harboring a dn heterozygous missense H4C11 (HIST1H4J) variant following trio-ES [c.274A>G / HGVS p.(Lys92Glu)]. Features incl. profound ID, microcephaly, short stature with some dysmorphic features (uplsanting p-f, hypertelorism, etc). Previous work-up was normal/non-diagnostic and incl. FMR1, MECP2 and a CMA showing an inherited 207 kb CNV involving KCNV1. Upon mRNA microinjection in zebrafish embryos - either for wt or for Lys92Glu HIST1H4J - effect for wt was very mild. Lys92Glu expression led to defective development of head structures (brain, eyes), faulty body axis growth and dysmorphic tail reproducing the microcephaly and short stature phenotype. This was similar to previous zebrafish studies for HIS1H4C variants (above). ------ Tessadori et al. (2022 - PMID: 35202563) describe 29 *additional individuals with de novo missense variants in genes encoding H4, namely: - H4C3 (HIST1H4C/N=6 subjects), - H4C11 (HIST1H4J/N=1), - H4C4 (HIST1H4D/N=1), - H4C5 (HIST1H4E/N=17), - H4C6 (HIST1H4F/N=1), - H4C9 (HIST1H4I/N=3). All individuals, exhibited DD and ID (29/29). Other features incl. hypotonia (10/29), seizures (5/29), autism (5/29), ataxia (4/29). Abnormal growth incl. progressive microcephaly (2/19 prenatal, 20/29 postnatal onset), short stature/FTT (each 11/29). Few had skeletal features (craniosynostosis 2/29, abn. digits 4/29, vertebral 4/29). Some had visual (17/28) or hearing impairment (7/29). Facial features incl. hypertelorism (5/29), upslanting p-f (3/29), broad nasal tip (11/29), thin upper lip (4/29) and teeth anomalies (6/29 - notably gap between central incisors). The authors state that the cohort was collected with trio WES but also after data sharing via Genematcher / DECIPHER. Identified variants were in all cases missense and de novo, the latter either by trio WES or Sanger sequencing of parents. Previous work-up or presence of additional variants are not discussed. At the protein level 10 aa were affected, 6 of which recurrently within the same gene (Arg45, His75, Lys91, Tyr98) as well among several genes for H4 (Pro32, Arg40). Variants lied within two clusters, one corresponding to the α-helix of H4 (reported variants affected Lys31 - Arg45) important for DNA contacts, interactions with H3 and histone chaperones. The other within the core of nucleosome (reported patient variants : His75-Tyr98) with important strucural contact between H3-H4 dimer and histone chaperones. There were no detectable genotype-phenotype patterns separating individual H4 genes or protein regions. Of note, variability was observed even among 7 individuals with the same dn H4C5 variant (Arg45Cys). All variants were absent from control databases incl. gnomAD and affected residues conserved through to S. cerevisiae. Substitutions affecting Arg45 and Gly94 and His75 have been studied previously with effect in growth/fitness/chromatin remodeling/DNA damage repair depending on variant (5 studies cited). Zebrafish embryos at the 1 cell stage were injected with mRNA encoding either wt or identified variants, the latter inducing significant developmental defects with the exception of Pro32Ala (H4C3) and Arg40Cys (H4C5, H4C11). For Pro32Ala and Arg40Cys however, the strong recurrence in this cohort supports pathogenicity. A dosage dependent effect was observed for 2 variants. H4 genes appear to be tolerant to both missense and loss-of-function variation (the latter even in homozygous form) suggesting a dominant effect of the variants. ------ [RefSeqs : H4C3/HIST1H4C - NM_0035242.4 | H4C4/HIST1H4D - NM_003539.4 | H4C5/HIST1H4E - NM_003545.3 | H4C6/HIST1H4F - NM_003540.4 | H4C9/HIST1H4I - NM_003495.2 | H4C11/HIST1H4J - NM_021968.4 // Variants at the protein level above are according to the HGVS nomenclature. However as the N-terminal methionine is cleaved, numbering relative to the mature peptide has also been used in publications eg. p.Pro33Ala HGVS corresponding to Pro32Ala] Sources: Literature |
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| Intellectual disability v3.1520 | HIST1H4E |
Konstantinos Varvagiannis gene: HIST1H4E was added gene: HIST1H4E was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: HIST1H4E was set to MONOALLELIC, autosomal or pseudoautosomal, imprinted status unknown Publications for gene: HIST1H4E were set to 35202563 Phenotypes for gene: HIST1H4E were set to Global developmental delay; Intellectual disability; Microcephaly; Growth abnormality; Abnormality of the face Penetrance for gene: HIST1H4E were set to unknown Mode of pathogenicity for gene: HIST1H4E was set to Loss-of-function variants (as defined in pop up message) DO NOT cause this phenotype - please provide details in the comments Review for gene: HIST1H4E was set to GREEN Added comment: Histone H4 is a core component of the nucleosome, the basic repeating unit of eukaryotic chromatin. Each nucleosome consists of ~150 bp of DNA wrapped around a histone octamer. Each histone octamer is composed of 2 copies of each of the histones H2A, H2B, H3, H4. This organization is important for DNA replication, transcription and repair. There are 14 canonical histone H4 genes in the human genome, which despite being different at the nucleotide level encode an identical protein. These cluster in 3 genomic loci. Their transcription is independently regulated with differing expression during brain development and in human tissues. Histone H4 forms a dimer with H3 (which however has variant isoforms linked to specific cellular processes). Pathogenic variants in genes encoding H4 have been reported in several individuals. Irrrespective of the gene for H4 involved, all patients presented with highly overlapping features, DD and ID being universal. Available reports to date concern : - H4C3/HIST1H4C (9 subjects - PMID: 28920961, 35202563), - H4C11/HIST1H4J (1 subject - PMID: 31804630, 35202563), - H4C4/HIST1H4D (1 subject - PMID:35202563), - H4C5/HIST1H4E (17 subjects - PMID: 35202563), - H4C6/HIST1H4F (1 subject - PMID: 35202563), - H4C9/HIST1H4I (3 subjects - PMID: 35202563). Variants in all cases were missense SNVs, occurring (in almost all cases) as dn variants and affecting the same residue in the same and/or different H4 genes (details for clusters below). Eg. Arg45Cys was a recurrent variant for H4C5 (>=7 subjects), while variants affecting Arg40 have been reported in H4C4, H4C5, H4C9, H4C11 (7 subjects overall). Zebrafish studies for all genes reported have included most - if not all - patient variants and recapitulate features observed in affected individuals (head size/structure and growth). Additional studies specificaly for H4C3/HIST1H4C have been performed in patient fibroblasts (demonstrating among others transcriptional dysregulation) and zebrafish (accumulation of DSBs, increased apoptosis in head/tail, abn. cell cycle progression). Note that the nomenclature for variants - at the protein level - used in literature commonly takes into consideration cleavage of Met1, thus the numbering may not correspond to the HGVS one. Relevant entries exist in OMIM, G2P and SysID only for H4C3/HIST1H4C (Tessadori-van Haaften neurodevelopmental syndrome 1, #619758) and H4C11/HIST1H4J (?Tessadori-van Haaften neurodevelopmental syndrome 2, #619759) but not for other genes. Rating in PanelApp Australia - ID Panel : HIST1H4C Green, H4J Amber, H4D Amber, H4E Green, H4F Amber, H4I Green. Please consider inclusion in other possibly relevant panels (microcephaly, short stature/FTT, etc). ------ Initial work from Tessadori et al (incl. DDD study, 2017 - PMID:28920961) identified monoallelic missense SNVs affecting the same residue of H4C3 (HIST1H4C), in 3 individuals from 2 families. [c.274A>C/ HGVS p.(Lys92Gln) dn in 1 subject and c.275A>C/ HGVS p.(Lys92Arg) inherited from unaffected mosaic parent]. Individuals from both families having relevant age had intellectual disability (2/2 - 2 families). Other features incl. growth delay (3/3) and microcephaly (3/3). Expression of the variants in zebrafish severely affected structural development recapitulating the patient phenotypes (microcephaly and short stature). RNA sequencing in fibroblasts from 2 unrelated patients and a control, revealed that expression of H4C3 variants was similar to wt. The authors estimated that ~8% of H4 cDNA molecules contained the variant. LC-MS/MS analysis suggested that the mutant protein was present in nucleosomes at a level of 1-2% while RNA-seq identified 115 differential expressed genes, with enrichment for relevant procedures (chr. organization, histone binding, DNA packaging, nucleosomal organization, cell cycle). Post-translational modifications of Lys92 (H4K91) are highly conserved and have been previously associated with processes from chromatin assembly , DNA damage sensitivity, etc. Post-translational marks on Lys92 (K91) were absent in patient derived cells as a result of each variant. Zebrafish models for both variants were suggestive for accumulation of double strand breaks (DSBs) more visible in heads and tails of larvae. Embryos expressing mutants displayed increased apoptosis in head and tail. Additional studies in larvae were suggestive of abnormal cell cycle progression (rel. increase in cellls in S/G2/M phase, increased occurrence of activated CHK2 with p53 stabilization) applying to both variants studied. ------ In a subsequent publication, Tessadori et al. (2020 - PMID: 31804630) described the phenotype of a 14 y.o. boy harboring a dn heterozygous missense H4C11 (HIST1H4J) variant following trio-ES [c.274A>G / HGVS p.(Lys92Glu)]. Features incl. profound ID, microcephaly, short stature with some dysmorphic features (uplsanting p-f, hypertelorism, etc). Previous work-up was normal/non-diagnostic and incl. FMR1, MECP2 and a CMA showing an inherited 207 kb CNV involving KCNV1. Upon mRNA microinjection in zebrafish embryos - either for wt or for Lys92Glu HIST1H4J - effect for wt was very mild. Lys92Glu expression led to defective development of head structures (brain, eyes), faulty body axis growth and dysmorphic tail reproducing the microcephaly and short stature phenotype. This was similar to previous zebrafish studies for HIS1H4C variants (above). ------ Tessadori et al. (2022 - PMID: 35202563) describe 29 *additional individuals with de novo missense variants in genes encoding H4, namely: - H4C3 (HIST1H4C/N=6 subjects), - H4C11 (HIST1H4J/N=1), - H4C4 (HIST1H4D/N=1), - H4C5 (HIST1H4E/N=17), - H4C6 (HIST1H4F/N=1), - H4C9 (HIST1H4I/N=3). All individuals, exhibited DD and ID (29/29). Other features incl. hypotonia (10/29), seizures (5/29), autism (5/29), ataxia (4/29). Abnormal growth incl. progressive microcephaly (2/19 prenatal, 20/29 postnatal onset), short stature/FTT (each 11/29). Few had skeletal features (craniosynostosis 2/29, abn. digits 4/29, vertebral 4/29). Some had visual (17/28) or hearing impairment (7/29). Facial features incl. hypertelorism (5/29), upslanting p-f (3/29), broad nasal tip (11/29), thin upper lip (4/29) and teeth anomalies (6/29 - notably gap between central incisors). The authors state that the cohort was collected with trio WES but also after data sharing via Genematcher / DECIPHER. Identified variants were in all cases missense and de novo, the latter either by trio WES or Sanger sequencing of parents. Previous work-up or presence of additional variants are not discussed. At the protein level 10 aa were affected, 6 of which recurrently within the same gene (Arg45, His75, Lys91, Tyr98) as well among several genes for H4 (Pro32, Arg40). Variants lied within two clusters, one corresponding to the α-helix of H4 (reported variants affected Lys31 - Arg45) important for DNA contacts, interactions with H3 and histone chaperones. The other within the core of nucleosome (reported patient variants : His75-Tyr98) with important strucural contact between H3-H4 dimer and histone chaperones. There were no detectable genotype-phenotype patterns separating individual H4 genes or protein regions. Of note, variability was observed even among 7 individuals with the same dn H4C5 variant (Arg45Cys). All variants were absent from control databases incl. gnomAD and affected residues conserved through to S. cerevisiae. Substitutions affecting Arg45 and Gly94 and His75 have been studied previously with effect in growth/fitness/chromatin remodeling/DNA damage repair depending on variant (5 studies cited). Zebrafish embryos at the 1 cell stage were injected with mRNA encoding either wt or identified variants, the latter inducing significant developmental defects with the exception of Pro32Ala (H4C3) and Arg40Cys (H4C5, H4C11). For Pro32Ala and Arg40Cys however, the strong recurrence in this cohort supports pathogenicity. A dosage dependent effect was observed for 2 variants. H4 genes appear to be tolerant to both missense and loss-of-function variation (the latter even in homozygous form) suggesting a dominant effect of the variants. ------ [RefSeqs : H4C3/HIST1H4C - NM_0035242.4 | H4C4/HIST1H4D - NM_003539.4 | H4C5/HIST1H4E - NM_003545.3 | H4C6/HIST1H4F - NM_003540.4 | H4C9/HIST1H4I - NM_003495.2 | H4C11/HIST1H4J - NM_021968.4 // Variants at the protein level above are according to the HGVS nomenclature. However as the N-terminal methionine is cleaved, numbering relative to the mature peptide has also been used in publications eg. p.Pro33Ala HGVS corresponding to Pro32Ala] Sources: Literature |
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| Intellectual disability v3.1520 | HIST1H4F |
Konstantinos Varvagiannis gene: HIST1H4F was added gene: HIST1H4F was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: HIST1H4F was set to MONOALLELIC, autosomal or pseudoautosomal, imprinted status unknown Publications for gene: HIST1H4F were set to 35202563 Phenotypes for gene: HIST1H4F were set to Global developmental delay; Intellectual disability; Microcephaly; Growth abnormality; Abnormality of the face Penetrance for gene: HIST1H4F were set to unknown Mode of pathogenicity for gene: HIST1H4F was set to Loss-of-function variants (as defined in pop up message) DO NOT cause this phenotype - please provide details in the comments Review for gene: HIST1H4F was set to AMBER Added comment: Histone H4 is a core component of the nucleosome, the basic repeating unit of eukaryotic chromatin. Each nucleosome consists of ~150 bp of DNA wrapped around a histone octamer. Each histone octamer is composed of 2 copies of each of the histones H2A, H2B, H3, H4. This organization is important for DNA replication, transcription and repair. There are 14 canonical histone H4 genes in the human genome, which despite being different at the nucleotide level encode an identical protein. These cluster in 3 genomic loci. Their transcription is independently regulated with differing expression during brain development and in human tissues. Histone H4 forms a dimer with H3 (which however has variant isoforms linked to specific cellular processes). Pathogenic variants in genes encoding H4 have been reported in several individuals. Irrrespective of the gene for H4 involved, all patients presented with highly overlapping features, DD and ID being universal. Available reports to date concern : - H4C3/HIST1H4C (9 subjects - PMID: 28920961, 35202563), - H4C11/HIST1H4J (1 subject - PMID: 31804630, 35202563), - H4C4/HIST1H4D (1 subject - PMID:35202563), - H4C5/HIST1H4E (17 subjects - PMID: 35202563), - H4C6/HIST1H4F (1 subject - PMID: 35202563), - H4C9/HIST1H4I (3 subjects - PMID: 35202563). Variants in all cases were missense SNVs, occurring (in almost all cases) as dn variants and affecting the same residue in the same and/or different H4 genes (details for clusters below). Eg. Arg45Cys was a recurrent variant for H4C5 (>=7 subjects), while variants affecting Arg40 have been reported in H4C4, H4C5, H4C9, H4C11 (7 subjects overall). Zebrafish studies for all genes reported have included most - if not all - patient variants and recapitulate features observed in affected individuals (head size/structure and growth). Additional studies specificaly for H4C3/HIST1H4C have been performed in patient fibroblasts (demonstrating among others transcriptional dysregulation) and zebrafish (accumulation of DSBs, increased apoptosis in head/tail, abn. cell cycle progression). Note that the nomenclature for variants - at the protein level - used in literature commonly takes into consideration cleavage of Met1, thus the numbering may not correspond to the HGVS one. Relevant entries exist in OMIM, G2P and SysID only for H4C3/HIST1H4C (Tessadori-van Haaften neurodevelopmental syndrome 1, #619758) and H4C11/HIST1H4J (?Tessadori-van Haaften neurodevelopmental syndrome 2, #619759) but not for other genes. Rating in PanelApp Australia - ID Panel : HIST1H4C Green, H4J Amber, H4D Amber, H4E Green, H4F Amber, H4I Green. Please consider inclusion in other possibly relevant panels (microcephaly, short stature/FTT, etc). ------ Initial work from Tessadori et al (incl. DDD study, 2017 - PMID:28920961) identified monoallelic missense SNVs affecting the same residue of H4C3 (HIST1H4C), in 3 individuals from 2 families. [c.274A>C/ HGVS p.(Lys92Gln) dn in 1 subject and c.275A>C/ HGVS p.(Lys92Arg) inherited from unaffected mosaic parent]. Individuals from both families having relevant age had intellectual disability (2/2 - 2 families). Other features incl. growth delay (3/3) and microcephaly (3/3). Expression of the variants in zebrafish severely affected structural development recapitulating the patient phenotypes (microcephaly and short stature). RNA sequencing in fibroblasts from 2 unrelated patients and a control, revealed that expression of H4C3 variants was similar to wt. The authors estimated that ~8% of H4 cDNA molecules contained the variant. LC-MS/MS analysis suggested that the mutant protein was present in nucleosomes at a level of 1-2% while RNA-seq identified 115 differential expressed genes, with enrichment for relevant procedures (chr. organization, histone binding, DNA packaging, nucleosomal organization, cell cycle). Post-translational modifications of Lys92 (H4K91) are highly conserved and have been previously associated with processes from chromatin assembly , DNA damage sensitivity, etc. Post-translational marks on Lys92 (K91) were absent in patient derived cells as a result of each variant. Zebrafish models for both variants were suggestive for accumulation of double strand breaks (DSBs) more visible in heads and tails of larvae. Embryos expressing mutants displayed increased apoptosis in head and tail. Additional studies in larvae were suggestive of abnormal cell cycle progression (rel. increase in cellls in S/G2/M phase, increased occurrence of activated CHK2 with p53 stabilization) applying to both variants studied. ------ In a subsequent publication, Tessadori et al. (2020 - PMID: 31804630) described the phenotype of a 14 y.o. boy harboring a dn heterozygous missense H4C11 (HIST1H4J) variant following trio-ES [c.274A>G / HGVS p.(Lys92Glu)]. Features incl. profound ID, microcephaly, short stature with some dysmorphic features (uplsanting p-f, hypertelorism, etc). Previous work-up was normal/non-diagnostic and incl. FMR1, MECP2 and a CMA showing an inherited 207 kb CNV involving KCNV1. Upon mRNA microinjection in zebrafish embryos - either for wt or for Lys92Glu HIST1H4J - effect for wt was very mild. Lys92Glu expression led to defective development of head structures (brain, eyes), faulty body axis growth and dysmorphic tail reproducing the microcephaly and short stature phenotype. This was similar to previous zebrafish studies for HIS1H4C variants (above). ------ Tessadori et al. (2022 - PMID: 35202563) describe 29 *additional individuals with de novo missense variants in genes encoding H4, namely: - H4C3 (HIST1H4C/N=6 subjects), - H4C11 (HIST1H4J/N=1), - H4C4 (HIST1H4D/N=1), - H4C5 (HIST1H4E/N=17), - H4C6 (HIST1H4F/N=1), - H4C9 (HIST1H4I/N=3). All individuals, exhibited DD and ID (29/29). Other features incl. hypotonia (10/29), seizures (5/29), autism (5/29), ataxia (4/29). Abnormal growth incl. progressive microcephaly (2/19 prenatal, 20/29 postnatal onset), short stature/FTT (each 11/29). Few had skeletal features (craniosynostosis 2/29, abn. digits 4/29, vertebral 4/29). Some had visual (17/28) or hearing impairment (7/29). Facial features incl. hypertelorism (5/29), upslanting p-f (3/29), broad nasal tip (11/29), thin upper lip (4/29) and teeth anomalies (6/29 - notably gap between central incisors). The authors state that the cohort was collected with trio WES but also after data sharing via Genematcher / DECIPHER. Identified variants were in all cases missense and de novo, the latter either by trio WES or Sanger sequencing of parents. Previous work-up or presence of additional variants are not discussed. At the protein level 10 aa were affected, 6 of which recurrently within the same gene (Arg45, His75, Lys91, Tyr98) as well among several genes for H4 (Pro32, Arg40). Variants lied within two clusters, one corresponding to the α-helix of H4 (reported variants affected Lys31 - Arg45) important for DNA contacts, interactions with H3 and histone chaperones. The other within the core of nucleosome (reported patient variants : His75-Tyr98) with important strucural contact between H3-H4 dimer and histone chaperones. There were no detectable genotype-phenotype patterns separating individual H4 genes or protein regions. Of note, variability was observed even among 7 individuals with the same dn H4C5 variant (Arg45Cys). All variants were absent from control databases incl. gnomAD and affected residues conserved through to S. cerevisiae. Substitutions affecting Arg45 and Gly94 and His75 have been studied previously with effect in growth/fitness/chromatin remodeling/DNA damage repair depending on variant (5 studies cited). Zebrafish embryos at the 1 cell stage were injected with mRNA encoding either wt or identified variants, the latter inducing significant developmental defects with the exception of Pro32Ala (H4C3) and Arg40Cys (H4C5, H4C11). For Pro32Ala and Arg40Cys however, the strong recurrence in this cohort supports pathogenicity. A dosage dependent effect was observed for 2 variants. H4 genes appear to be tolerant to both missense and loss-of-function variation (the latter even in homozygous form) suggesting a dominant effect of the variants. ------ [RefSeqs : H4C3/HIST1H4C - NM_0035242.4 | H4C4/HIST1H4D - NM_003539.4 | H4C5/HIST1H4E - NM_003545.3 | H4C6/HIST1H4F - NM_003540.4 | H4C9/HIST1H4I - NM_003495.2 | H4C11/HIST1H4J - NM_021968.4 // Variants at the protein level above are according to the HGVS nomenclature. However as the N-terminal methionine is cleaved, numbering relative to the mature peptide has also been used in publications eg. p.Pro33Ala HGVS corresponding to Pro32Ala] Sources: Literature |
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| Intellectual disability v3.1520 | HIST1H4I |
Konstantinos Varvagiannis gene: HIST1H4I was added gene: HIST1H4I was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: HIST1H4I was set to MONOALLELIC, autosomal or pseudoautosomal, imprinted status unknown Publications for gene: HIST1H4I were set to 35202563 Phenotypes for gene: HIST1H4I were set to Global developmental delay; Intellectual disability; Microcephaly; Growth abnormality; Abnormality of the face Penetrance for gene: HIST1H4I were set to unknown Mode of pathogenicity for gene: HIST1H4I was set to Loss-of-function variants (as defined in pop up message) DO NOT cause this phenotype - please provide details in the comments Review for gene: HIST1H4I was set to GREEN Added comment: Histone H4 is a core component of the nucleosome, the basic repeating unit of eukaryotic chromatin. Each nucleosome consists of ~150 bp of DNA wrapped around a histone octamer. Each histone octamer is composed of 2 copies of each of the histones H2A, H2B, H3, H4. This organization is important for DNA replication, transcription and repair. There are 14 canonical histone H4 genes in the human genome, which despite being different at the nucleotide level encode an identical protein. These cluster in 3 genomic loci. Their transcription is independently regulated with differing expression during brain development and in human tissues. Histone H4 forms a dimer with H3 (which however has variant isoforms linked to specific cellular processes). Pathogenic variants in genes encoding H4 have been reported in several individuals. Irrrespective of the gene for H4 involved, all patients presented with highly overlapping features, DD and ID being universal. Available reports to date concern : - H4C3/HIST1H4C (9 subjects - PMID: 28920961, 35202563), - H4C11/HIST1H4J (1 subject - PMID: 31804630, 35202563), - H4C4/HIST1H4D (1 subject - PMID:35202563), - H4C5/HIST1H4E (17 subjects - PMID: 35202563), - H4C6/HIST1H4F (1 subject - PMID: 35202563), - H4C9/HIST1H4I (3 subjects - PMID: 35202563). Variants in all cases were missense SNVs, occurring (in almost all cases) as dn variants and affecting the same residue in the same and/or different H4 genes (details for clusters below). Eg. Arg45Cys was a recurrent variant for H4C5 (>=7 subjects), while variants affecting Arg40 have been reported in H4C4, H4C5, H4C9, H4C11 (7 subjects overall). Zebrafish studies for all genes reported have included most - if not all - patient variants and recapitulate features observed in affected individuals (head size/structure and growth). Additional studies specificaly for H4C3/HIST1H4C have been performed in patient fibroblasts (demonstrating among others transcriptional dysregulation) and zebrafish (accumulation of DSBs, increased apoptosis in head/tail, abn. cell cycle progression). Note that the nomenclature for variants - at the protein level - used in literature commonly takes into consideration cleavage of Met1, thus the numbering may not correspond to the HGVS one. Relevant entries exist in OMIM, G2P and SysID only for H4C3/HIST1H4C (Tessadori-van Haaften neurodevelopmental syndrome 1, #619758) and H4C11/HIST1H4J (?Tessadori-van Haaften neurodevelopmental syndrome 2, #619759) but not for other genes. Rating in PanelApp Australia - ID Panel : HIST1H4C Green, H4J Amber, H4D Amber, H4E Green, H4F Amber, H4I Green. Please consider inclusion in other possibly relevant panels (microcephaly, short stature/FTT, etc). ------ Initial work from Tessadori et al (incl. DDD study, 2017 - PMID:28920961) identified monoallelic missense SNVs affecting the same residue of H4C3 (HIST1H4C), in 3 individuals from 2 families. [c.274A>C/ HGVS p.(Lys92Gln) dn in 1 subject and c.275A>C/ HGVS p.(Lys92Arg) inherited from unaffected mosaic parent]. Individuals from both families having relevant age had intellectual disability (2/2 - 2 families). Other features incl. growth delay (3/3) and microcephaly (3/3). Expression of the variants in zebrafish severely affected structural development recapitulating the patient phenotypes (microcephaly and short stature). RNA sequencing in fibroblasts from 2 unrelated patients and a control, revealed that expression of H4C3 variants was similar to wt. The authors estimated that ~8% of H4 cDNA molecules contained the variant. LC-MS/MS analysis suggested that the mutant protein was present in nucleosomes at a level of 1-2% while RNA-seq identified 115 differential expressed genes, with enrichment for relevant procedures (chr. organization, histone binding, DNA packaging, nucleosomal organization, cell cycle). Post-translational modifications of Lys92 (H4K91) are highly conserved and have been previously associated with processes from chromatin assembly , DNA damage sensitivity, etc. Post-translational marks on Lys92 (K91) were absent in patient derived cells as a result of each variant. Zebrafish models for both variants were suggestive for accumulation of double strand breaks (DSBs) more visible in heads and tails of larvae. Embryos expressing mutants displayed increased apoptosis in head and tail. Additional studies in larvae were suggestive of abnormal cell cycle progression (rel. increase in cellls in S/G2/M phase, increased occurrence of activated CHK2 with p53 stabilization) applying to both variants studied. ------ In a subsequent publication, Tessadori et al. (2020 - PMID: 31804630) described the phenotype of a 14 y.o. boy harboring a dn heterozygous missense H4C11 (HIST1H4J) variant following trio-ES [c.274A>G / HGVS p.(Lys92Glu)]. Features incl. profound ID, microcephaly, short stature with some dysmorphic features (uplsanting p-f, hypertelorism, etc). Previous work-up was normal/non-diagnostic and incl. FMR1, MECP2 and a CMA showing an inherited 207 kb CNV involving KCNV1. Upon mRNA microinjection in zebrafish embryos - either for wt or for Lys92Glu HIST1H4J - effect for wt was very mild. Lys92Glu expression led to defective development of head structures (brain, eyes), faulty body axis growth and dysmorphic tail reproducing the microcephaly and short stature phenotype. This was similar to previous zebrafish studies for HIS1H4C variants (above). ------ Tessadori et al. (2022 - PMID: 35202563) describe 29 *additional individuals with de novo missense variants in genes encoding H4, namely: - H4C3 (HIST1H4C/N=6 subjects), - H4C11 (HIST1H4J/N=1), - H4C4 (HIST1H4D/N=1), - H4C5 (HIST1H4E/N=17), - H4C6 (HIST1H4F/N=1), - H4C9 (HIST1H4I/N=3). All individuals, exhibited DD and ID (29/29). Other features incl. hypotonia (10/29), seizures (5/29), autism (5/29), ataxia (4/29). Abnormal growth incl. progressive microcephaly (2/19 prenatal, 20/29 postnatal onset), short stature/FTT (each 11/29). Few had skeletal features (craniosynostosis 2/29, abn. digits 4/29, vertebral 4/29). Some had visual (17/28) or hearing impairment (7/29). Facial features incl. hypertelorism (5/29), upslanting p-f (3/29), broad nasal tip (11/29), thin upper lip (4/29) and teeth anomalies (6/29 - notably gap between central incisors). The authors state that the cohort was collected with trio WES but also after data sharing via Genematcher / DECIPHER. Identified variants were in all cases missense and de novo, the latter either by trio WES or Sanger sequencing of parents. Previous work-up or presence of additional variants are not discussed. At the protein level 10 aa were affected, 6 of which recurrently within the same gene (Arg45, His75, Lys91, Tyr98) as well among several genes for H4 (Pro32, Arg40). Variants lied within two clusters, one corresponding to the α-helix of H4 (reported variants affected Lys31 - Arg45) important for DNA contacts, interactions with H3 and histone chaperones. The other within the core of nucleosome (reported patient variants : His75-Tyr98) with important strucural contact between H3-H4 dimer and histone chaperones. There were no detectable genotype-phenotype patterns separating individual H4 genes or protein regions. Of note, variability was observed even among 7 individuals with the same dn H4C5 variant (Arg45Cys). All variants were absent from control databases incl. gnomAD and affected residues conserved through to S. cerevisiae. Substitutions affecting Arg45 and Gly94 and His75 have been studied previously with effect in growth/fitness/chromatin remodeling/DNA damage repair depending on variant (5 studies cited). Zebrafish embryos at the 1 cell stage were injected with mRNA encoding either wt or identified variants, the latter inducing significant developmental defects with the exception of Pro32Ala (H4C3) and Arg40Cys (H4C5, H4C11). For Pro32Ala and Arg40Cys however, the strong recurrence in this cohort supports pathogenicity. A dosage dependent effect was observed for 2 variants. H4 genes appear to be tolerant to both missense and loss-of-function variation (the latter even in homozygous form) suggesting a dominant effect of the variants. ------ [RefSeqs : H4C3/HIST1H4C - NM_0035242.4 | H4C4/HIST1H4D - NM_003539.4 | H4C5/HIST1H4E - NM_003545.3 | H4C6/HIST1H4F - NM_003540.4 | H4C9/HIST1H4I - NM_003495.2 | H4C11/HIST1H4J - NM_021968.4 // Variants at the protein level above are according to the HGVS nomenclature. However as the N-terminal methionine is cleaved, numbering relative to the mature peptide has also been used in publications eg. p.Pro33Ala HGVS corresponding to Pro32Ala] Sources: Literature |
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| Intellectual disability v3.1518 | TIAM1 |
Konstantinos Varvagiannis gene: TIAM1 was added gene: TIAM1 was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: TIAM1 was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: TIAM1 were set to 35240055; 33328293 Phenotypes for gene: TIAM1 were set to Delayed speech and language development; Global developmental delay; Intellectual disability; Seizures; Behavioral abnormality; Abnormality of the endocrine system; Hypothyroidism; Abnormality of nervous system morphology Penetrance for gene: TIAM1 were set to Complete Review for gene: TIAM1 was set to AMBER Added comment: Lu et al (2022 - PMID: 35240055) describe 5 individuals (from 4 families) with biallelic TIAM1 missense variants. The phenotype overall corresponded to a neurodevelopmental disorder with DD (5/5), ID (4/4 individuals of relevant age - 3 families), speech delay (5/5), seizures (5/5 - onset: 2m-13y) and behavioral abnormalities (2/2, sibs with autism and ADHD). Several subjects had endocrine symptoms, namely hypothyroidism (N=3 - 2 families), Addison's disease (1) or hypomagnesemia (1). Non-consistent abnormalities were reported in (3/3) subjects who had a brain MRI. Previous investigations were mentioned for 3 individuals (incl. 2 sibs) and included normal CMA and/or metabolic workup. Singleton or trio exome sequencing (in one family) revealed biallelic missense TIAM1 variants. 6 different missense variants were reported, all ultra-rare or not present in gnomAD (also o/e:0.2, pLI:0.96), with CADD scores in favor of deleterious effect (NM_001353694.2): c.67C>T/p.Arg23Cys*, c.2584C>T/p.Leu862Phe*, c.983G>T/p.Gly328Val*, c.4640C>A/p.Ala1547Glu, c.1144G>C/p.Gly382Arg, c.4016C>T/p.Ala1339Val. TIAM1 encodes a RAC1-specific guanine exchange factor (GEF), regulating RAC1 signaling pathways that in turn affect cell shape, migration, adhesion, growth, survival, and polarity, and influence actin cytoskeletal organization, endocytosis, and membrane trafficking. RAC1 signaling plays important role in control of neuronal morphogenesis and neurite outgrowth (based on the summary by Entrez and authors). TIAM1 is highly expressed in human brain (GTEx). The authors provide evidence that sif, the Drosophila ortholog, is expressed primarily in neurons of the fly CNS (but not in glia). Using different sif LoF mutant flies they demonstrate that loss of sif impairs viability. Surviving flies exhibited climbing defects and seizure-like behaviors, both significantly rescued upon UAS-sif expression. Neuronal specific sif knockdown resulted in similar phenotypes to ubiquitous knockdown, while glial knockdown did not result in climbing defects. The semi-lethal phenotype could be fully rescued by expression of the fly sif cDNA, but only partially by human TIAM1 cDNA reference. Upon expression, 3 patient-variants (R23C, L862F, G328V) had variable rescue abilities similar to or lower (R23C) than TIAM1 Ref. TIAM1 Ref and variants could not rescue the neurological phenotypes though. Higher/ectopic expression of sif or TIAM1 Ref was toxic, which was also observed to a lesser extent for variants. Overall, the evidence provided suggests that the 3 variants tested induce partial LoF. In a recent study cited (PMID: 33328293), Tiam1 KO mice had simplified dendritic arbors, reduced spine density and diminished excitatory transmission in dentate gyrus. The authors comment that this mouse model presented only subtle behavioral abnormalities which they speculate may be secondary to GEF redundancy (eg. Tiam2). There is no TIAM1-associated phenotype in OMIM/G2P/SysID. TIAM1 is included in PanelApp Australia in the ID and epilepsy panels with green rating. Consider inclusion in the current panel with amber rating [As authors discuss: some phenotypic features differed in their small cohort and the contribution of other recessive conditions in 2 consanguineous families cannot be excluded. Also: in fig S1 only status of parents but not of affected/unaffected sibs is specified with the exception of Fam1]. Sources: Literature |
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| Intellectual disability v3.1262 | ZNF668 |
Zornitza Stark gene: ZNF668 was added gene: ZNF668 was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: ZNF668 was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: ZNF668 were set to 34313816; 26633546 Phenotypes for gene: ZNF668 were set to DNA damage repair defect; microcephaly; growth deficiency; severe global developmental delay; brain malformation; facial dysmorphism Review for gene: ZNF668 was set to AMBER Added comment: 2 consanguineous families reported with different biallelic truncating (not NMD) variants in ZNF668. Phenotypes included microcephaly, growth deficiency, severe global developmental delay, brain malformation, and distinct facial dysmorphism. Immunofluorescence indicated ZNF668 deficiency. An increased DNA damage phenotype was demonstrated in patient fibroblasts. Sources: Literature |
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| Intellectual disability v3.1220 | VPS50 |
Konstantinos Varvagiannis gene: VPS50 was added gene: VPS50 was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: VPS50 was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: VPS50 were set to 34037727 Phenotypes for gene: VPS50 were set to Neonatal cholestatic liver disease; Failure to thrive; Profound global developmental delay; Postnatal microcephaly; Seizures; Abnormality of the corpus callosum Penetrance for gene: VPS50 were set to Complete Review for gene: VPS50 was set to AMBER Added comment: Schneeberger et al (2021 - PMID: 34037727) describe the phenotype of 2 unrelated individuals with biallelic VPS50 variants. Common features included transient neonatal cholestasis, failure to thrive, severe DD with failure to achieve milestones (last examination at 2y and 2y2m respectively), postnatal microcephaly, seizures (onset at 6m and 25m) and irritability. There was corpus callosum hypoplasia on brain imaging. Both individuals were homozygous for variants private to each family (no/not known consanguinity applying to each case). The first individual was homozygous for a splicing variant (NM_017667.4:c.1978-1G>T) and had a similarly unaffected sister deceased with no available DNA for testing. The other individual was homozygous for an in-frame deletion (c.1823_1825delCAA / p.(Thr608del)). VPS50 encodes a critical component of the endosome-associated recycling protein (EARP) complex, which functions in recycling endocytic vesicles back to the plasma membrane [OMIM based on Schindler et al]. The complex contains VPS50, VPS51, VPS52, VPS53, the three latter also being components of GARP (Golgi-associated-retrograde protein) complex. GARP contains VPS54 instead of VPS50 and is required for trafficking of proteins to the trans-golgi network. Thus VPS50 (also named syndetin) and VPS54 function in the EARP and GARP complexes, to define directional movement of their endocytic vesicles [OMIM based on Schindler et al]. The VPS50 subunit is required for recycling of the transferrin receptor. As discussed by Schneeberger et al (refs provided in text): - VPS50 has a high expression in mouse and human brain as well as throughout mouse brain development. - Mice deficient for Vps50 have not been reported. vps50 knockdown in zebrafish results in severe developmental defects of the body axis. Knockout mice for other proteins of the EARP/GARP complex (e.g. Vps52, 53 and 54) display embryonic lethality. Studies performed by Schneeberger et al included: - Transcript analysis for the 1st variant demonstrated skipping of ex21 (in patient derived fabriblasts) leading to an in frame deletion of 81 bp (r.1978_2058del) with predicted loss of 27 residues (p.Leu660_Leu686del). - Similar VPS50 mRNA levels but significant reduction of protein levels (~5% and ~8% of controls) were observed in fibroblasts from patients 1 and 2. Additionally, significant reductions in the amounts of VPS52 and VPS53 protein levels were observed despite mRNA levels similar to controls. Overall, this suggested drastic reduction of functional EARP complex levels. - Lysosomes appeared to have similar morphology, cellular distribution and likely unaffected function in patient fibroblasts. - Transferrin receptor recycling was shown to be delayed in patient fibroblasts suggestive of compromise of endocytic-recycling function. As the authors comment, the phenotype of both individuals with biallelic VPS50 variants overlaps with the corresponding phenotype reported in 15 subjects with biallelic VPS53 or VPS51 mutations notably, severe DD/ID, microcephaly and early onset epilepsy, CC anomalies. Overall, for this group, they propose the term "GARP and/or EARP deficiency disorders". There is no VPS50-associated phenotype in OMIM or G2P. SysID includes VPS50 among the ID candidate genes. Consider inclusion in other relevant gene panels (e.g. for neonatal cholestasis, epilepsy, microcephaly, growth failure in early infancy, corpus callosum anomalies, etc) with amber rating pending further reports. Sources: Literature |
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| Intellectual disability v3.1217 | PIDD1 |
Konstantinos Varvagiannis changed review comment from: There is enough evidence to include this gene in the current panel with green rating. Biallelic PIDD1 pathogenic variants have been reported in 26 individuals (11 families) with DD (all), variable degrees of ID (mild to severe), behavioral (eg. aggression/self-mutilation in several, ADHD) and/or psychiatric abnormalities (ASD, psychosis in 5 belonging to 3 families), well-controlled epilepsy is some (9 subjects from 6 families) and MRI abnormalities notably abnormal gyration pattern (pachygyria with predominant anterior gradient) as well as corpus callosum anomalies (commonly thinning) in several. Dysmorphic features have been reported in almost all, although there has been no specific feature suggested. The first reports on the phenotype associated with biallelic PIDD1 mutations were made by Harripaul et al (2018 - PMID: 28397838) and Hu et al (2019 - PMID: 29302074) [both studies investigating large cohorts of individuals with ID from consanguineous families]. Sheikh et al (2021 - PMID: 33414379) provided details on the phenotype of 15 individuals from 5 families including those from the previous 2 reports and studied provided evidence on the role of PIDD1 and the effect of variants. Zaki et al (2021 - PMID: 34163010) reported 11 additional individuals from 6 consanguineous families, summarize the features of all subjects published in the literature and review the neuroradiological features of the disorder. PIDD1 encodes p53-induced death domain protein 1. The protein is part of the PIDDosome, a multiprotein complex also composed of the bipartite linker protein CRADD (also known as RAIDD) and the proform of caspase-2 and induces apoptosis in response to DNA damage. There are 5 potential PIDD1 mRNA transcript variants with NM_145886.4 corresponding to the longest. Similar to the protein encoded by CRADD, PIDD1 contains a death domain (DD - aa 774-893). Constitutive post-translational processing gives PIDD1-N, PIDD1-C the latter further processed into PIDD1-CC (by auto-cleavage). Serine residues at pos. 446 and 588 are involved in this autoprocessing generating PIDD1-C (aa 446-910) and PIDD1-CC (aa 774-893). The latter is needed for caspase-2 activation. Most (if not all) individuals belonged to consanguineous families of different origins and harbored pLoF or missense variants. Variants reported so far include : c.2587C>T; p.Gln863* / c.1909C>T ; p.Arg637* / c.2443C>T / p.Arg815Trp / c.2275-1G>A which upon trap assay was shown to lead to skipping of ex15 with direct splicing form exon14 to the terminal exon 16 (resulting to p.Arg759Glyfs*1 with exlcusion of the entire DD) / c.2584C>T; p.Arg862Trp / c.1340G>A; p.Trp447* / c.2116_2120del; p.Val706His*, c.1564_1565del; p.Gly602fs*26 Evidence so far provided includes: - Biallelic CRADD variants cause a NDD disorder and a highly similar gyration pattern. - Confirmation of splicing effect (eg. for c.2275-1G>A premature stop in position 760) or poor expression (NM_145886.3:c.2587C>T; p.Gln863*). Arg815Trp did not affect autoprocessing or protein stability. - Abnormal localization pattern, loss of interaction with CRADD and failure to activate caspase-2 (MDM2 cleavage assay) [p.Gln863* and Arg815Trp] - Available expression data from GTEx (PIDD1 having broad expression in multiple tissues, but higher in brain cerebellum) as well as BrainSpan and PsychEncode studies suggesting high coexpression of PIDD1, CRADD and CASP2 in many regions in the developing human brain. - Variants in other genes encoding proteins interacting with PIDD1 (MADD, FADD, DNAJ, etc) are associated with NDD. Pidd-1 ko mice (ex3-15 removal) lack however CNS-related phenotypes. These show decreased anxiety but no motor anomalies. This has also been the case with Cradd-/- mice displaying no significant CNS phenotypes without lamination defects. There is currently no associated phenotype in OMIM, PanelApp Australia. PIDD1 is listed in the DD panel of G2P (PIDD1-relared NDD / biallelic / loss of function / probable) . SysID includes PIDD1 among the current primary ID genes. Overall the gene appears to be relevant for the epilepsy panel, panels for gyration and/or corpus callosum anomalies etc. Sources: Literature, Other; to: There is enough evidence to include this gene in the current panel with green rating. Biallelic PIDD1 pathogenic variants have been reported in 26 individuals (11 families) with DD (all), variable degrees of ID (mild to severe), behavioral (eg. aggression/self-mutilation in several, ADHD) and/or psychiatric abnormalities (ASD, psychosis in 5 belonging to 3 families), well-controlled epilepsy is some (9 subjects from 6 families) and MRI abnormalities notably abnormal gyration pattern (pachygyria with predominant anterior gradient) as well as corpus callosum anomalies (commonly thinning) in several. Dysmorphic features have been reported in almost all, although there has been no specific feature suggested. The first reports on the phenotype associated with biallelic PIDD1 mutations were made by Harripaul et al (2018 - PMID: 28397838) and Hu et al (2019 - PMID: 29302074) [both studies investigating large cohorts of individuals with ID from consanguineous families]. Sheikh et al (2021 - PMID: 33414379) provided details on the phenotype of 15 individuals from 5 families including those from the previous 2 reports and studied provided evidence on the role of PIDD1 and the effect of variants. Zaki et al (2021 - PMID: 34163010) reported 11 additional individuals from 6 consanguineous families, summarize the features of all subjects published in the literature and review the neuroradiological features of the disorder. PIDD1 encodes p53-induced death domain protein 1. The protein is part of the PIDDosome, a multiprotein complex also composed of the bipartite linker protein CRADD (also known as RAIDD) and the proform of caspase-2 and induces apoptosis in response to DNA damage. There are 5 potential PIDD1 mRNA transcript variants with NM_145886.4 corresponding to the longest. Similar to the protein encoded by CRADD, PIDD1 contains a death domain (DD - aa 774-893). Constitutive post-translational processing gives PIDD1-N, PIDD1-C the latter further processed into PIDD1-CC (by auto-cleavage). Serine residues at pos. 446 and 588 are involved in this autoprocessing generating PIDD1-C (aa 446-910) and PIDD1-CC (aa 774-893). The latter is needed for caspase-2 activation. Most (if not all) individuals belonged to consanguineous families of different origins and harbored pLoF or missense variants. Variants reported so far include : c.2587C>T; p.Gln863* / c.1909C>T ; p.Arg637* / c.2443C>T / p.Arg815Trp / c.2275-1G>A which upon trap assay was shown to lead to skipping of ex15 with direct splicing form exon14 to the terminal exon 16 (resulting to p.Arg759Glyfs*1 with exlcusion of the entire DD) / c.2584C>T; p.Arg862Trp / c.1340G>A; p.Trp447* / c.2116_2120del; p.Val706His*, c.1564_1565del; p.Gly602fs*26 Evidence so far provided includes: - Biallelic CRADD variants cause a NDD disorder and a highly similar gyration pattern. - Confirmation of splicing effect (eg. for c.2275-1G>A premature stop in position 760) or poor expression (NM_145886.3:c.2587C>T; p.Gln863*). Arg815Trp did not affect autoprocessing or protein stability. - Abnormal localization pattern, loss of interaction with CRADD and failure to activate caspase-2 (MDM2 cleavage assay) [p.Gln863* and Arg815Trp] - Available expression data from GTEx (PIDD1 having broad expression in multiple tissues, but higher in brain cerebellum) as well as BrainSpan and PsychEncode studies suggesting high coexpression of PIDD1, CRADD and CASP2 in many regions in the developing human brain. - Variants in other genes encoding proteins interacting with PIDD1 (MADD, FADD, DNAJ, etc) are associated with NDD. Pidd-1 ko mice (ex3-15 removal) lack however CNS-related phenotypes. These show decreased anxiety but no motor anomalies. This has also been the case with Cradd-/- mice displaying no significant CNS phenotypes without lamination defects. There is currently no associated phenotype in OMIM, PanelApp Australia. PIDD1 is listed in the DD panel of G2P (PIDD1-related NDD / biallelic / loss of function / probable) . SysID includes PIDD1 among the current primary ID genes. Overall the gene appears to be relevant for the epilepsy panel, panels for gyration and/or corpus callosum anomalies etc. Sources: Literature, Other |
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| Intellectual disability v3.1217 | PIDD1 |
Konstantinos Varvagiannis gene: PIDD1 was added gene: PIDD1 was added to Intellectual disability. Sources: Literature,Other Mode of inheritance for gene: PIDD1 was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: PIDD1 were set to 28397838; 29302074; 33414379; 34163010 Phenotypes for gene: PIDD1 were set to Global developmental delay; Intellectual disability; Seizures; Autism; Behavioral abnormality; Psychosis; Pachygyria; Lissencephaly; Abnormality of the corpus callosum Penetrance for gene: PIDD1 were set to Complete Review for gene: PIDD1 was set to GREEN Added comment: There is enough evidence to include this gene in the current panel with green rating. Biallelic PIDD1 pathogenic variants have been reported in 26 individuals (11 families) with DD (all), variable degrees of ID (mild to severe), behavioral (eg. aggression/self-mutilation in several, ADHD) and/or psychiatric abnormalities (ASD, psychosis in 5 belonging to 3 families), well-controlled epilepsy is some (9 subjects from 6 families) and MRI abnormalities notably abnormal gyration pattern (pachygyria with predominant anterior gradient) as well as corpus callosum anomalies (commonly thinning) in several. Dysmorphic features have been reported in almost all, although there has been no specific feature suggested. The first reports on the phenotype associated with biallelic PIDD1 mutations were made by Harripaul et al (2018 - PMID: 28397838) and Hu et al (2019 - PMID: 29302074) [both studies investigating large cohorts of individuals with ID from consanguineous families]. Sheikh et al (2021 - PMID: 33414379) provided details on the phenotype of 15 individuals from 5 families including those from the previous 2 reports and studied provided evidence on the role of PIDD1 and the effect of variants. Zaki et al (2021 - PMID: 34163010) reported 11 additional individuals from 6 consanguineous families, summarize the features of all subjects published in the literature and review the neuroradiological features of the disorder. PIDD1 encodes p53-induced death domain protein 1. The protein is part of the PIDDosome, a multiprotein complex also composed of the bipartite linker protein CRADD (also known as RAIDD) and the proform of caspase-2 and induces apoptosis in response to DNA damage. There are 5 potential PIDD1 mRNA transcript variants with NM_145886.4 corresponding to the longest. Similar to the protein encoded by CRADD, PIDD1 contains a death domain (DD - aa 774-893). Constitutive post-translational processing gives PIDD1-N, PIDD1-C the latter further processed into PIDD1-CC (by auto-cleavage). Serine residues at pos. 446 and 588 are involved in this autoprocessing generating PIDD1-C (aa 446-910) and PIDD1-CC (aa 774-893). The latter is needed for caspase-2 activation. Most (if not all) individuals belonged to consanguineous families of different origins and harbored pLoF or missense variants. Variants reported so far include : c.2587C>T; p.Gln863* / c.1909C>T ; p.Arg637* / c.2443C>T / p.Arg815Trp / c.2275-1G>A which upon trap assay was shown to lead to skipping of ex15 with direct splicing form exon14 to the terminal exon 16 (resulting to p.Arg759Glyfs*1 with exlcusion of the entire DD) / c.2584C>T; p.Arg862Trp / c.1340G>A; p.Trp447* / c.2116_2120del; p.Val706His*, c.1564_1565del; p.Gly602fs*26 Evidence so far provided includes: - Biallelic CRADD variants cause a NDD disorder and a highly similar gyration pattern. - Confirmation of splicing effect (eg. for c.2275-1G>A premature stop in position 760) or poor expression (NM_145886.3:c.2587C>T; p.Gln863*). Arg815Trp did not affect autoprocessing or protein stability. - Abnormal localization pattern, loss of interaction with CRADD and failure to activate caspase-2 (MDM2 cleavage assay) [p.Gln863* and Arg815Trp] - Available expression data from GTEx (PIDD1 having broad expression in multiple tissues, but higher in brain cerebellum) as well as BrainSpan and PsychEncode studies suggesting high coexpression of PIDD1, CRADD and CASP2 in many regions in the developing human brain. - Variants in other genes encoding proteins interacting with PIDD1 (MADD, FADD, DNAJ, etc) are associated with NDD. Pidd-1 ko mice (ex3-15 removal) lack however CNS-related phenotypes. These show decreased anxiety but no motor anomalies. This has also been the case with Cradd-/- mice displaying no significant CNS phenotypes without lamination defects. There is currently no associated phenotype in OMIM, PanelApp Australia. PIDD1 is listed in the DD panel of G2P (PIDD1-relared NDD / biallelic / loss of function / probable) . SysID includes PIDD1 among the current primary ID genes. Overall the gene appears to be relevant for the epilepsy panel, panels for gyration and/or corpus callosum anomalies etc. Sources: Literature, Other |
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| Intellectual disability v3.1120 | GEMIN5 |
Zornitza Stark gene: GEMIN5 was added gene: GEMIN5 was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: GEMIN5 was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: GEMIN5 were set to 33963192 Phenotypes for gene: GEMIN5 were set to Neurodevelopmental disorder with cerebellar atrophy and motor dysfunction, MIM# 619333 Review for gene: GEMIN5 was set to GREEN gene: GEMIN5 was marked as current diagnostic Added comment: Neurodevelopmental disorder with cerebellar atrophy and motor dysfunction (NEDCAM) is an autosomal recessive disorder characterized by global developmental delay with prominent motor abnormalities, mainly axial hypotonia, gait ataxia, and appendicular spasticity. Affected individuals have cognitive impairment and speech delay; brain imaging shows cerebellar atrophy. 30 individuals from 22 unrelated families reported. Sources: Literature |
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| Intellectual disability v3.1037 | JMJD1C |
Zornitza Stark gene: JMJD1C was added gene: JMJD1C was added to Intellectual disability. Sources: Expert Review Mode of inheritance for gene: JMJD1C was set to MONOALLELIC, autosomal or pseudoautosomal, NOT imprinted Publications for gene: JMJD1C were set to 26181491; 32996679 Phenotypes for gene: JMJD1C were set to Intellectual disability Review for gene: JMJD1C was set to GREEN gene: JMJD1C was marked as current diagnostic Added comment: Reported in ID cohort (with Rett-like phenotypic overlap) with supporting functional studies (PMID: 26181491). 7 individuals with rare variants identified, and variants demonstrated to be de novo in 2, one with a Rett-like phenotype and the other with ID. Functional study of the JMJD1C mutant Rett syndrome patient demonstrated that the altered protein had abnormal subcellular localization, diminished activity to demethylate the DNA damage-response protein MDC1, and reduced binding to MECP2. JMJD1C protein shown to be widely expressed in brain regions and that its depletion compromised dendritic activity. Splice-disrupting JMJD1C variant reported in association with learning disability and myoclonic epilepsy (PMID 32996679). Disruption of gene due to balanced translocation (PMID 33591602) implicated in autism spectrum disease phenotype. Sources: Expert Review |
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| Intellectual disability v3.990 | RAD50 |
Arina Puzriakova edited their review of gene: RAD50: Added comment: - PMID: 33378670 (2020) - single patient described with bone marrow failure, immunodeficiency and developmental defects, who was compound heterozygous for a frameshift and premature stop codon (c.2165dup; p.Glu723Glyfs∗5 - maternally inherited) and in-frame deletion (c.3109_3111del; p.Glu1035del - de novo) in the RAD50 gene. Functional characterisation using patient-derived fibroblasts indicated defects in DNA replication, DNA repair, and DNA end resection; however, ATM-dependent DNA damage response remained intact. Studies in yeast modelling the variant corresponding to p.Glu1035del produced defects in both DNA repair and Tel1ATM-dependent signalling following thermal activation. This is the third case published with biallelic variants in the RAD50 gene. Although authors report 'developmental defects', it is unclear whether this individual displayed cognitive impairment. Therefore, maintaining the Red gene rating on this panel.; Changed rating: RED; Changed publications: 19409520, 32212377, 33378670; Changed phenotypes: Nijmegen breakage syndrome-like disorder, OMIM:613078; Changed mode of inheritance: BIALLELIC, autosomal or pseudoautosomal |
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| Intellectual disability v3.982 | DDB1 |
Arina Puzriakova changed review comment from: - PMID: 33743206 (2021) - 8 unrelated individuals with de novo variants in DDB1, including one recurrent variant in four individuals (c.637G>A, p.Glu213Lys) and two different substitutions at the same amino acid residue (p.Arg188Trp and p.Arg188Gln). Clinical features were consistent and include hypotonia (7/8) and mild-moderate developmental delay or intellectual disability (8/8) and similar facial gestalt. Brachydactyly was common and most noticeable in the feet (6/8), and two individuals had cutaneous toe syndactyly. All three older individuals had a BMI in the obese range for their age. Functional studies using patient-derived lymphoblasts showed altered DDB1 function resulting in abnormal DNA damage signatures and histone methylation following UV-induced DNA damage. Sources: Literature; to: - PMID: 33743206 (2021) - 8 unrelated individuals with de novo variants in DDB1, including one recurrent variant in four individuals (c.637G>A, p.Glu213Lys) and two different substitutions at the same amino acid residue (p.Arg188Trp and p.Arg188Gln). Clinical features were consistent and include hypotonia (7/8) and mild-moderate developmental delay or intellectual disability (8/8) and similar facial gestalt. Brachydactyly was common and most noticeable in the feet (6/8), and two individuals had cutaneous toe syndactyly. All three older individuals had a BMI in the obese range for their age. Functional studies using patient-derived lymphoblasts showed altered DDB1 function resulting in abnormal DNA damage signatures and histone methylation following UV-induced DNA damage. Variants in other CRL4 complex components, such as CUL4B (MIM# 300304) and PHIP (MIM# 612870), have been shown to cause overlapping phenotypes consisting of syndromic ID with hypotonia and obesity. Sources: Literature |
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| Intellectual disability v3.982 | DDB1 |
Arina Puzriakova gene: DDB1 was added gene: DDB1 was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: DDB1 was set to MONOALLELIC, autosomal or pseudoautosomal, imprinted status unknown Publications for gene: DDB1 were set to 33743206 Phenotypes for gene: DDB1 were set to Intellectual disability Review for gene: DDB1 was set to GREEN Added comment: - PMID: 33743206 (2021) - 8 unrelated individuals with de novo variants in DDB1, including one recurrent variant in four individuals (c.637G>A, p.Glu213Lys) and two different substitutions at the same amino acid residue (p.Arg188Trp and p.Arg188Gln). Clinical features were consistent and include hypotonia (7/8) and mild-moderate developmental delay or intellectual disability (8/8) and similar facial gestalt. Brachydactyly was common and most noticeable in the feet (6/8), and two individuals had cutaneous toe syndactyly. All three older individuals had a BMI in the obese range for their age. Functional studies using patient-derived lymphoblasts showed altered DDB1 function resulting in abnormal DNA damage signatures and histone methylation following UV-induced DNA damage. Sources: Literature |
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| Intellectual disability v3.773 | OTUD5 | Zornitza Stark changed review comment from: PMID 33523931: Another 10 individuals from 7 families reported, promote to Green. X-linked multiple congenital anomalies-neurodevelopmental syndrome (MCAND) is an X-linked recessive congenital multisystemic disorder characterized by poor growth, global developmental delay with impaired intellectual development, and variable abnormalities of the cardiac, skeletal, and genitourinary systems. Most affected individuals also have hypotonia and dysmorphic craniofacial features. Brain imaging typically shows enlarged ventricles and thin corpus callosum; some have microcephaly, whereas others have hydrocephalus. The severity of the disorder is highly variable, ranging from death in early infancy to survival into the second or third decade.; to: PMID 33523931: Another 10 individuals from 7 families reported. Key features include poor growth, global developmental delay with impaired intellectual development, and variable abnormalities of the cardiac, skeletal, and genitourinary systems. Most affected individuals also have hypotonia and dysmorphic craniofacial features. Brain imaging typically shows enlarged ventricles and thin corpus callosum; some have microcephaly, whereas others have hydrocephalus. The severity of the disorder is highly variable, ranging from death in early infancy to survival into the second or third decade. | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability v3.773 | OTUD5 | Zornitza Stark edited their review of gene: OTUD5: Added comment: PMID 33523931: Another 10 individuals from 7 families reported, promote to Green. X-linked multiple congenital anomalies-neurodevelopmental syndrome (MCAND) is an X-linked recessive congenital multisystemic disorder characterized by poor growth, global developmental delay with impaired intellectual development, and variable abnormalities of the cardiac, skeletal, and genitourinary systems. Most affected individuals also have hypotonia and dysmorphic craniofacial features. Brain imaging typically shows enlarged ventricles and thin corpus callosum; some have microcephaly, whereas others have hydrocephalus. The severity of the disorder is highly variable, ranging from death in early infancy to survival into the second or third decade.; Changed rating: GREEN; Changed publications: 33131077, 33523931 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability v3.731 | TANC2 |
Arina Puzriakova Added comment: Comment on list classification: This gene should be promoted to Green at the next GMS panel update - multiple unrelated families with a comparable neurodevelopmental disorder (including ID). As highlighted in review by Zornitza Stark, most reported SNVs are de novo putative disruptive variants, or missense variants that are predicted in silico to have a damaging or possibly damaging effect. Gene expression and function are neurodevelopmentally-relevant, and there is some limited functional data. Gene-disease association is also now listed in both OMIM and Gene2Phenotype. |
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| Intellectual disability v3.681 | SMG8 |
Arina Puzriakova edited their review of gene: SMG8: Added comment: PMID: 33242396 (2020) - 9 affected individuals from 4 consanguineous families with different biallelic variants in the SMG8 gene. Clinical features include GDD (8/8), dysmorphic features (9/9) microcephaly (6/9), short stature (4/9), brain imaging anomalies (4/5), congenital heart disease (3/9) and cataract (3/8). Only two sibs from Family 2 had a formal ID diagnosis, but this can be inferred from the clinical reports of the other cases demonstrating severe language delays, difficulties to follow simple instructions or perform daily activities. ----- Several features described here overlap with those in the previously reported cases from PMID: 31130284 (e.g. microcephaly, ID, cataract, VSD); Changed rating: GREEN; Changed publications: 31130284, 33242396 |
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| Intellectual disability v3.681 | KCNMA1 |
Arina Puzriakova changed review comment from: Multiple individuals reported with either mono- or biallelic variants. Developmental delay and intellectual disability of relevant severity to this panel has been reported in a sufficient number of cases for inclusion on this panel. Although in most cases the phenotypes are primarily characterised by seizures or dyskinesia, it is plausible that these individuals may still be tested under the ID panel. Furthermore, several individuals have been reported with severe GDD/ID and other variable feature such as craniofacial dysmorphism, ataxia, bone dysplasia, visceral malformations, and brain imaging anomalies, but without epilepsy or paroxysmal dyskinesia (namely Liang-Wang syndrome, PMID: 31152168). In less severely affected cases DD with significant speech delay has been noted as the main clinical indication of the presenting phenotypes, further indicating benefit of inclusion on a diagnostic ID panel.; to: Multiple individuals reported with either mono- or biallelic variants. Developmental delay and intellectual disability of relevant severity has been reported in a sufficient number of cases for inclusion on this panel. Although in most cases the phenotypes are primarily characterised by seizures or dyskinesia, it is plausible that these individuals may still be tested under the ID panel in context of the severe intellectual impairment that may be observed. Furthermore, several individuals have been reported with severe GDD/ID and other variable feature such as craniofacial dysmorphism, ataxia, bone dysplasia, visceral malformations, and brain imaging anomalies, but without epilepsy or paroxysmal dyskinesia (namely Liang-Wang syndrome, PMID: 31152168). In less severely affected cases DD with significant speech delay has been noted as the main clinical indication of the presenting phenotypes, further indicating benefit of inclusion on a diagnostic ID panel. |
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| Intellectual disability v3.645 | ISCA-37418-Loss | Arina Puzriakova Phenotypes for Region: ISCA-37418-Loss were changed from Potocki-Lupski syndrome; hypotonia, poor feeding, failure to thrive, developmental delay particularly cognitive and language deficity, mild-moderate intellectual deficit, and neuropsychiatric disorders; Smith-Magenis syndrome; Structural cardiovascular anomalies (dilated aortic root, bicommissural aortic valve, atrial/ventricular and septal defects) and sleep disturbance; 182290; moderate intellectual disability, delayed speech and language skills, distinctive facial features, sleep disturbances, and behavioral problems; hypotonia, failure to thrive, mental retardation, pervasive developmental disorders, congenital anomalies; Dental abnormalities to Smith-Magenis syndrome, OMIM:182290; Smith-Magenis syndrome, MONDO:0008434 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability v3.644 | KDM4B |
Zornitza Stark gene: KDM4B was added gene: KDM4B was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: KDM4B was set to MONOALLELIC, autosomal or pseudoautosomal, NOT imprinted Publications for gene: KDM4B were set to 33232677 Phenotypes for gene: KDM4B were set to Global developmental delay, intellectual disability and neuroanatomical defects Review for gene: KDM4B was set to GREEN Added comment: Nine individuals with mono-allelic de novo or inherited variants in KDM4B. All individuals presented with dysmorphic features and global developmental delay (GDD) with language and motor skills most affected. Three individuals had a history of seizures, and four had anomalies on brain imaging ranging from agenesis of the corpus callosum with hydrocephalus to cystic formations, abnormal hippocampi, and polymicrogyria. In a knockout mouse the total brain volume was significantly reduced with decreased size of the hippocampal dentate gyrus, partial agenesis of the corpus callosum, and ventriculomegaly. Sources: Literature |
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| Intellectual disability v3.573 | ISCA-37418-Loss | Zornitza Stark reviewed Region: ISCA-37418-Loss: Rating: GREEN; Mode of pathogenicity: None; Publications: ; Phenotypes: Smith-Magenis syndrome, MIM# 182290; Mode of inheritance: MONOALLELIC, autosomal or pseudoautosomal, NOT imprinted | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability v3.500 | MPP5 |
Konstantinos Varvagiannis gene: MPP5 was added gene: MPP5 was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: MPP5 was set to MONOALLELIC, autosomal or pseudoautosomal, imprinted status unknown Publications for gene: MPP5 were set to 33073849 Phenotypes for gene: MPP5 were set to Global developmental delay; Intellectual disability; Delayed speech and language development; Developmental regression; Behavioral abnormality Penetrance for gene: MPP5 were set to unknown Review for gene: MPP5 was set to GREEN Added comment: Sterling et al (2020 - PMID: 33073849) provide information on the phenotype of 3 individuals with de novo MPP5 variants. Common features included global developmental delay, intellectual disability (3/3 - severe in 2/3), speech delay/regression (the latter in at least 2) and behavioral abnormalities. Variable other features were reported, among others microcephaly (1/3), abnormal vision (1/3 : CVI, retinal dystrophy, nystagmus), brain MRI abnormalities (2/3), late-onset seizures (1/3). These subjects displayed variable and non-specific dysmorphic features. All were investigated by exome sequencing (previous tests not mentioned). One subject was found to harbor a de novo mosaic (5/25 reads) stopgain variant, further confirmed by Sanger sequencing [NM_022474.4:c.1555C>T - p.(Arg519Ter). The specific variant is reported once in gnomAD (1/251338). Two de novo missense variants were identified in the remaining individuals [c.1289A>G - p.Glu430Gly / c.974A>C - p.His325Pro). All variants had in silico predictions in favor of a deleterious effect (CADD score >24). The authors comment that MPP5 encodes an apical complex protein with asymmetric localization to the apical side of polarized cells. It is expressed in brain, peripheral nervous system and other tissues. MPP5 is a member of the membrane-associated guanylate kinase family of proteins (MAGUK, p55 subfamily), determining cell polarity at tight junctions. Previous animal models suggest that complete Mpp5(Pals1) KO in mice leads to near absence of cerebral cortical neurons. Htz KO mice display reduction in size of cerebral cortex and hippocampus. The gene is expressed in proliferating cell populations of cerebellum and important for establishment cerebellar architecture. Conditional KO of Mpp5(Pals1) in retinal progenitor cells mimics the retinal pathology observed in LCA. [Several refs. provided] The authors studied a heterozygous CNS-specific Mpp5 KO mouse model. These mice presented microcephaly, decreased cerebellar volume and cortical thickness, decreased ependymal cells and Mpp5 at the apical surface of cortical vertrical zone. The proportion of cortical cells undergoing apoptotic cell death was increased. Mice displayed behavioral abnormalities (hyperactivity) and visual deficits, with ERG traces further suggesting retinal blindness. Overall the mouse model was thought to recapitulate the behavioral abnormalities observed in affected subjects as well as individual rare features such as microcephaly and abnormal vision. Haploinsufficiency (rather than a dominant negative effect) is favored as the underlying disease mechanism. This is also in line with a dose dependent effect observed in mice. Sources: Literature |
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| Intellectual disability v3.497 | MFSD2A | Arina Puzriakova Phenotypes for gene: MFSD2A were changed from NA to Neurodevelopmental disorder with progressive microcephaly, spasticity, and brain imaging abnormalities, 616486 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability v3.494 | MFSD2A | Arina Puzriakova reviewed gene: MFSD2A: Rating: GREEN; Mode of pathogenicity: None; Publications: 26005868, 26005865, 29302074, 30043326, 32572202; Phenotypes: Neurodevelopmental disorder with progressive microcephaly, spasticity, and brain imaging abnormalities, 616486; Mode of inheritance: BIALLELIC, autosomal or pseudoautosomal | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability v3.456 | LMNB2 |
Konstantinos Varvagiannis gene: LMNB2 was added gene: LMNB2 was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: LMNB2 was set to MONOALLELIC, autosomal or pseudoautosomal, imprinted status unknown Publications for gene: LMNB2 were set to 33033404 Phenotypes for gene: LMNB2 were set to Congenital microcephaly; Global developmental delay; Intellectual disability Penetrance for gene: LMNB2 were set to Complete Mode of pathogenicity for gene: LMNB2 was set to Loss-of-function variants (as defined in pop up message) DO NOT cause this phenotype - please provide details in the comments Review for gene: LMNB2 was set to GREEN Added comment: Parry et al (2020 - PMID: 33033404) in a study to identify novel microcephaly genes using the DDD and 100k genomes project (100kGP) patient cohort, report on the phenotype of 13 individuals with heterozygous variant in LMNB1 (N=7) and LMNB2 (N=6). LMNB1 : The authors identified 3 recurrent variants (c.97A>G - p.Lys33Glu (3), c.97_99del - p.Lys33del (2) , c.269G>C - p.Arg90Pro (2) / NM_005573.4) in seven individuals (3 from the DDD study, 4 from the 100kGP). In all cases were segregation studies were possible, the variant had occurred as a de novo event. LMNB2 : 4 individuals from the DDD cohort and 1 from the 100kGP were found to harbor the same missense SNV (NM_032737.4:c.1192G>A, p.Glu398Lys). The variant had occurred de novo in 3 subjects and was inherited from a mosaic - unaffected - parent in a further case. Another individual was found to harbor c.160A>C - p.Asn54His. LMNB1/2 common phenotypes : All cases had congenital microcephaly (OFC -5.85 +/- 1.14 SD) apart from one individual, without history of IUGR or postnatally abnormal height (the latter in most). Neuroimaging suggested structurally normal brain without abnormal migration. Gyral simplification / global reduction in white matter / increased extra axial spaces / enlarged ventricles were reported in 2. LMNB1 - Global developmental delay was a feature in all (mild to severe) with some having occasional words at 7y (P3), absent speech (P9 - age category 5-10y) or ID not further specified (P13). LMNB2 - DD was a feature in all 6 subjects (5/6 moderate to severe - 1/6 GDD). 5/6 were 10y or older with language (in 3 language not achieved) and motor deficits (walking not achieved in 1/6 - occurred at the age of 6y in 1/6). Facial features were not consistent nor suggestive of a syndromic diagnosis (sloping forehead in some). Overall, as the authors comment, the phenotype corresponded to a severe nonsyndromic microcephaly (although additional features were reported in some). Animal model: Microcephaly is supported by Lmnb1 ko mouse model. Lmnb1/2 ko mice however display migration defects, while Lmnb2 ko mice do not have reduced size at birth. Heterozygous Lmnb1 mice do not present microcephaly. It is suggested that while animal models support a similar (to the human) phenotype the underlying mechanism is different. Variant effect : variants were shown to affect highly conserved residues within the lamin a-helical rod-domain. As affected residues are conserved in LMNA, modelling with available LMNA PDB structures, suggested disrupted interactions required for higher-order assembly of lamin filaments. Recurrence of specific variants at specific residues, absence of pLoF ones, the htz mouse Lmnb1 phenotype (absence of microcephaly) and the proposed mechanism (perturbation of complex formation) suggest a gain-of-function/dominant-negative effect rather than happloinsufficiency. [Please also note the additional OMIM phenotypes for LMNB1 / LMNB2 - not here reviewed] Sources: Literature |
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| Intellectual disability v3.456 | LMNB1 |
Konstantinos Varvagiannis edited their review of gene: LMNB1: Added comment: There is an additional report on LMBN1/2-associated phenotypes supporting green rating of the gene in the current panel. Parry et al (2020 - PMID: 33033404) in a study to identify novel microcephaly genes using the DDD and 100k genomes project (100kGP) patient cohort, report on the phenotype of 13 individuals with heterozygous variant in LMNB1 (N=7) and LMNB2 (N=6). LMNB1 : The authors identified 3 recurrent variants (c.97A>G - p.Lys33Glu (3), c.97_99del - p.Lys33del (2) , c.269G>C - p.Arg90Pro (2) / NM_005573.4) in seven individuals (3 from the DDD study, 4 from the 100kGP). In all cases were segregation studies were possible, the variant had occurred as a de novo event. LMNB2 : 4 individuals from the DDD cohort and 1 from the 100kGP were found to harbor the same missense SNV (NM_032737.4:c.1192G>A, p.Glu398Lys). The variant had occurred de novo in 3 subjects and was inherited from a mosaic - unaffected - parent in a further case. Another individual was found to harbor c.160A>C - p.Asn54His. LMNB1/2 common phenotypes : All cases had congenital microcephaly (OFC -5.85 +/- 1.14 SD) appart from one individual, without history of IUGR or postnatally abnormal height (the latter in most). Neuroimaging suggested structurally normal brain without abnormal migration. Gyral simplification / global reduction in white matter / increased extra axial spaces / enlarged ventricles were reported in 2. LMNB1 - Global developmental delay was a feature in all (mild to severe) with some having occasional words at 7y (P3), absent speech (P9 - age category 5-10y) or ID not further specified (P13). LMNB2 - DD was a feature in all 6 subjects (5/6 moderate to severe - 1/6 GDD). 5/6 were 10y or older with language (in 3 language not achieved) and motor deficits (walking not achieved in 1/6 - occured at the age of 6y in 1/6). Facial features were not consistent nor suggestive of a syndromic diagnosis (sloping forehead in some). Overall, as the authors comment, the phenotype corresponded to a severe nonsyndromic microcephaly (although additional features were reported in some). Animal model: Microcephaly is supported by Lmnb1 ko mouse model. Lmnb1/2 ko mice however display migration defects, while Lmnb2 ko mice do not have reduced size at birth. Heterozygous Lmnb1 mice do not present microcephaly. It is suggested that while animal models support a similar (to the human) phenotype the underlying mechanism is different. Variant effect : variants were shown to affect highly conserved residues within the lamin a-helical rod-domain. As affected residues are conserved in LMNA, modelling with available LMNA PDB structures, suggested disrupted interactions required for higher-order assembly of lamin filaments. Recurrence of specific variants at specific residues, absence of pLoF ones, the htz mouse Lmnb1 phenotype (absence of microcephaly) and the proposed mechanism (perturbation of complex formation) suggest a gain-of-function/dominant-negative effect rather than happloinsufficiency. [Please also note the additional OMIM phenotypes for LMNB1 / LMNB2 - not here reviewed]; Changed publications: 32910914, 33033404 |
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| Intellectual disability v3.369 | NEMF |
Konstantinos Varvagiannis changed review comment from: Martin et al (2020 - PMID:32934225) report on 8 individuals from 6 families with a juvenile neuromuscular disease due to biallelic NEMF variants. (In one of these 8 cases it could not be ruled out that a de novo and maternally inherited variant were on the same allele, as phase was not determined). A ninth individual with similar presentation was found to harbor a single NEMF missense SNV as de novo event (due to a speculated dominant-negative effect). This individual had a similar presentation. Features incl. hypotonia (4/8 with biallelic variant (B) | 1/1 monoallelic (M) ), DD/ID (7/8B | 0/1M) with speech delay as universal feature (8/8B | 1/1M), axonal neuropathy (3/3B | 1/1M), ataxia (3/8B | 0/1M). Other findings included tremor (1/7B | 1/1M), abnormal brain imaging (2/6B / ?/1M), kyphosis/scoliosis (4/8B | 0/1M), respiratory distress (1/8B | 0/1M). NEMF (Rqc2 in yeast) encodes the nuclear export mediator factor, a component of the Ribosome-associated Quality Control (RCQ) complex which is involved in proteolytic targeting of incomplete polypeptides prodduced by ribosome stalling. NEMF facilitates the recruitment of E3 ligase Listerin (LTN1) which ubiquitinates nascent polypeptide chains for subsequent proteasomal degradation. The author provide evidence that mice homozygous for Nemf missense mutations display progressive motor phenotypes, exhibit neurogenic atrophy and progressive axonal degeneration. A further NEMF-null mouse model displayed more severe phenotype (with heterozygous mice being unaffected). Equivalent mutations (of those in the above mouse model) in yeast (Rqc2) were shown to interfere with its ability to modify aberrant translation products with C-terminal tails which assist RQC-mediated protein degradation. Mutation of Ltn1 (belonging to the same protein control pathway) has been also shown to lead to neurodegeneration im mice. Overall NEMF is thought to play a role in neuronal translational homeostasis and the disorder to be mediated by dysfunction of the RQC pathway (normally protecting neurons against degeneration). Sources: Literature; to: Martin et al (2020 - PMID:32934225) report on 8 individuals from 6 families with a juvenile neuromuscular disease due to biallelic NEMF variants. (In one of these 8 cases it could not be ruled out that a de novo and maternally inherited variant were on the same allele, as phase was not determined). A ninth individual with similar presentation was found to harbor a single NEMF missense SNV as de novo event (due to a speculated dominant-negative effect). This individual had a similar presentation. Features incl. hypotonia (4/8 with biallelic variant (B) | 1/1 monoallelic (M) ), DD/ID (7/8B | 0/1M) with speech delay as universal feature (8/8B | 1/1M), axonal neuropathy (3/3B | 1/1M), ataxia (3/8B | 0/1M). Other findings included tremor (1/7B | 1/1M), abnormal brain imaging (2/6B / ?/1M), kyphosis/scoliosis (4/8B | 0/1M), respiratory distress (1/8B | 0/1M). NEMF (Rqc2 in yeast) encodes the nuclear export mediator factor, a component of the Ribosome-associated Quality Control (RCQ) complex which is involved in proteolytic targeting of incomplete polypeptides produced by ribosome stalling. NEMF facilitates the recruitment of E3 ligase Listerin (LTN1) which ubiquitinates nascent polypeptide chains for subsequent proteasomal degradation. The author provide evidence that mice homozygous for Nemf missense mutations display progressive motor phenotypes, exhibit neurogenic atrophy and progressive axonal degeneration. A further NEMF-null mouse model displayed more severe phenotype (with heterozygous mice being unaffected). Equivalent mutations (of those in the above mouse model) in yeast (Rqc2) were shown to interfere with its ability to modify aberrant translation products with C-terminal tails which assist RQC-mediated protein degradation. Mutation of Ltn1 (belonging to the same protein control pathway) has been also shown to lead to neurodegeneration in mice. Overall NEMF is thought to play a role in neuronal translational homeostasis and the disorder to be mediated by dysfunction of the RQC pathway (normally protecting neurons against degeneration). Sources: Literature |
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| Intellectual disability v3.369 | NEMF |
Konstantinos Varvagiannis changed review comment from: Martin et al (2020 - PMID:32934225) report on 8 individuals from 6 families with a juvenile neuromuscular disease due to biallelic NEMF variants. (In one of these 8 cases it could be ruled out that the de novo and maternally inherited variants were on the same allele, as phase was not been determined). A ninth individual with similar presentation was found to harbor a single NEMF missense SNV as de novo event (due to a speculated dominant-negative effect). This individual had a similar presentation. Features incl. hypotonia (4/8 with biallelic variant (B) | 1/1 monoallelic (M) ), DD/ID (7/8B | 0/1M) with speech delay as universal feature (8/8B | 1/1M), axonal neuropathy (3/3B | 1/1M), ataxia (3/8B | 0/1M). Other findings included tremor (1/7B | 1/1M), abnormal brain imaging (2/6B / ?/1M), kyphosis/scoliosis (4/8B | 0/1M), respiratory distress (1/8B | 0/1M). NEMF (Rqc2 in yeast) encodes the nuclear export mediator factor, a component of the Ribosome-associated Quality Control (RCQ) complex which is involved in proteolytic targeting of incomplete polypeptides prodduced by ribosome stalling. NEMF facilitates the recruitment of E3 ligase Listerin (LTN1) which ubiquitinates nascent polypeptide chains for subsequent proteasomal degradation. The author provide evidence that mice homozygous for Nemf missense mutations display progressive motor phenotypes, exhibit neurogenic atrophy and progressive axonal degeneration. A further NEMF-null mouse model displayed more severe phenotype (with heterozygous mice being unaffected). Equivalent mutations (of those in the above mouse model) in yeast (Rqc2) were shown to interfere with its ability to modify aberrant translation products with C-terminal tails which assist RQC-mediated protein degradation. Mutation of Ltn1 (belonging to the same protein control pathway) has been also shown to lead to neurodegeneration im mice. Overall NEMF is thought to play a role in neuronal translational homeostasis and the disorder to be mediated by dysfunction of the RQC pathway (normally protecting neurons against degeneration). Sources: Literature; to: Martin et al (2020 - PMID:32934225) report on 8 individuals from 6 families with a juvenile neuromuscular disease due to biallelic NEMF variants. (In one of these 8 cases it could not be ruled out that a de novo and maternally inherited variant were on the same allele, as phase was not determined). A ninth individual with similar presentation was found to harbor a single NEMF missense SNV as de novo event (due to a speculated dominant-negative effect). This individual had a similar presentation. Features incl. hypotonia (4/8 with biallelic variant (B) | 1/1 monoallelic (M) ), DD/ID (7/8B | 0/1M) with speech delay as universal feature (8/8B | 1/1M), axonal neuropathy (3/3B | 1/1M), ataxia (3/8B | 0/1M). Other findings included tremor (1/7B | 1/1M), abnormal brain imaging (2/6B / ?/1M), kyphosis/scoliosis (4/8B | 0/1M), respiratory distress (1/8B | 0/1M). NEMF (Rqc2 in yeast) encodes the nuclear export mediator factor, a component of the Ribosome-associated Quality Control (RCQ) complex which is involved in proteolytic targeting of incomplete polypeptides prodduced by ribosome stalling. NEMF facilitates the recruitment of E3 ligase Listerin (LTN1) which ubiquitinates nascent polypeptide chains for subsequent proteasomal degradation. The author provide evidence that mice homozygous for Nemf missense mutations display progressive motor phenotypes, exhibit neurogenic atrophy and progressive axonal degeneration. A further NEMF-null mouse model displayed more severe phenotype (with heterozygous mice being unaffected). Equivalent mutations (of those in the above mouse model) in yeast (Rqc2) were shown to interfere with its ability to modify aberrant translation products with C-terminal tails which assist RQC-mediated protein degradation. Mutation of Ltn1 (belonging to the same protein control pathway) has been also shown to lead to neurodegeneration im mice. Overall NEMF is thought to play a role in neuronal translational homeostasis and the disorder to be mediated by dysfunction of the RQC pathway (normally protecting neurons against degeneration). Sources: Literature |
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| Intellectual disability v3.369 | NEMF |
Konstantinos Varvagiannis changed review comment from: Martin et al (2020 - PMID:32934225) report on 8 individuals from 6 families with a juvenile neuromuscular disease due to biallelic NEMF variants. A ninth individual with similar presentation was found to harbor a single NEMF missense SNV as de novo event (due to a speculated dominant-negative effect). This individual had a similar presentation. Features incl. hypotonia (4/8 with biallelic variant (B) | 1/1 monoallelic (M) ), DD/ID (7/8B | 0/1M) with speech delay as universal feature (8/8B | 1/1M), axonal neuropathy (3/3B | 1/1M), ataxia (3/8B | 0/1M). Other findings included tremor (1/7B | 1/1M), abnormal brain imaging (2/6B / ?/1M), kyphosis/scoliosis (4/8B | 0/1M), respiratory distress (1/8B | 0/1M). NEMF (Rqc2 in yeast) encodes the nuclear export mediator factor, a component of the Ribosome-associated Quality Control (RCQ) complex which is involved in proteolytic targeting of incomplete polypeptides prodduced by ribosome stalling. NEMF facilitates the recruitment of E3 ligase Listerin (LTN1) which ubiquitinates nascent polypeptide chains for subsequent proteasomal degradation. The author provide evidence that mice homozygous for Nemf missense mutations display progressive motor phenotypes, exhibit neurogenic atrophy and progressive axonal degeneration. A further NEMF-null mouse model displayed more severe phenotype (with heterozygous mice being unaffected). Equivalent mutations (of those in the above mouse model) in yeast (Rqc2) were shown to interfere with its ability to modify aberrant translation products with C-terminal tails which assist RQC-mediated protein degradation. Mutation of Ltn1 (belonging to the same protein control pathway) has been also shown to lead to neurodegeneration im mice. Overall NEMF is thought to play a role in neuronal translational homeostasis and the disorder to be mediated by dysfunction of the RQC pathway (normally protecting neurons against degeneration). Sources: Literature; to: Martin et al (2020 - PMID:32934225) report on 8 individuals from 6 families with a juvenile neuromuscular disease due to biallelic NEMF variants. (In one of these 8 cases it could be ruled out that the de novo and maternally inherited variants were on the same allele, as phase was not been determined). A ninth individual with similar presentation was found to harbor a single NEMF missense SNV as de novo event (due to a speculated dominant-negative effect). This individual had a similar presentation. Features incl. hypotonia (4/8 with biallelic variant (B) | 1/1 monoallelic (M) ), DD/ID (7/8B | 0/1M) with speech delay as universal feature (8/8B | 1/1M), axonal neuropathy (3/3B | 1/1M), ataxia (3/8B | 0/1M). Other findings included tremor (1/7B | 1/1M), abnormal brain imaging (2/6B / ?/1M), kyphosis/scoliosis (4/8B | 0/1M), respiratory distress (1/8B | 0/1M). NEMF (Rqc2 in yeast) encodes the nuclear export mediator factor, a component of the Ribosome-associated Quality Control (RCQ) complex which is involved in proteolytic targeting of incomplete polypeptides prodduced by ribosome stalling. NEMF facilitates the recruitment of E3 ligase Listerin (LTN1) which ubiquitinates nascent polypeptide chains for subsequent proteasomal degradation. The author provide evidence that mice homozygous for Nemf missense mutations display progressive motor phenotypes, exhibit neurogenic atrophy and progressive axonal degeneration. A further NEMF-null mouse model displayed more severe phenotype (with heterozygous mice being unaffected). Equivalent mutations (of those in the above mouse model) in yeast (Rqc2) were shown to interfere with its ability to modify aberrant translation products with C-terminal tails which assist RQC-mediated protein degradation. Mutation of Ltn1 (belonging to the same protein control pathway) has been also shown to lead to neurodegeneration im mice. Overall NEMF is thought to play a role in neuronal translational homeostasis and the disorder to be mediated by dysfunction of the RQC pathway (normally protecting neurons against degeneration). Sources: Literature |
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| Intellectual disability v3.369 | NEMF |
Konstantinos Varvagiannis gene: NEMF was added gene: NEMF was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: NEMF was set to BOTH monoallelic and biallelic, autosomal or pseudoautosomal Publications for gene: NEMF were set to 32934225 Phenotypes for gene: NEMF were set to Hypotonia; Global developmental delay; Intellectual disability; Axonal neuropathy; Ataxia; Abnormal brain imaging; Kyphosis; Scoliosis; Tremor; Respiratory distress Penetrance for gene: NEMF were set to Complete Review for gene: NEMF was set to GREEN Added comment: Martin et al (2020 - PMID:32934225) report on 8 individuals from 6 families with a juvenile neuromuscular disease due to biallelic NEMF variants. A ninth individual with similar presentation was found to harbor a single NEMF missense SNV as de novo event (due to a speculated dominant-negative effect). This individual had a similar presentation. Features incl. hypotonia (4/8 with biallelic variant (B) | 1/1 monoallelic (M) ), DD/ID (7/8B | 0/1M) with speech delay as universal feature (8/8B | 1/1M), axonal neuropathy (3/3B | 1/1M), ataxia (3/8B | 0/1M). Other findings included tremor (1/7B | 1/1M), abnormal brain imaging (2/6B / ?/1M), kyphosis/scoliosis (4/8B | 0/1M), respiratory distress (1/8B | 0/1M). NEMF (Rqc2 in yeast) encodes the nuclear export mediator factor, a component of the Ribosome-associated Quality Control (RCQ) complex which is involved in proteolytic targeting of incomplete polypeptides prodduced by ribosome stalling. NEMF facilitates the recruitment of E3 ligase Listerin (LTN1) which ubiquitinates nascent polypeptide chains for subsequent proteasomal degradation. The author provide evidence that mice homozygous for Nemf missense mutations display progressive motor phenotypes, exhibit neurogenic atrophy and progressive axonal degeneration. A further NEMF-null mouse model displayed more severe phenotype (with heterozygous mice being unaffected). Equivalent mutations (of those in the above mouse model) in yeast (Rqc2) were shown to interfere with its ability to modify aberrant translation products with C-terminal tails which assist RQC-mediated protein degradation. Mutation of Ltn1 (belonging to the same protein control pathway) has been also shown to lead to neurodegeneration im mice. Overall NEMF is thought to play a role in neuronal translational homeostasis and the disorder to be mediated by dysfunction of the RQC pathway (normally protecting neurons against degeneration). Sources: Literature |
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| Intellectual disability v3.236 | SUZ12 | Sarah Leigh Phenotypes for gene: SUZ12 were changed from Overgrowth; Global developmental delay; Intellectual disability; Accelerated skeletal maturation; Abnormality of the skeletal system; Abnormality of the genitourinary system; Abnormality of the corpus callosum; Abnormality of the respiratory system; Abnormality of the abdominal wall to Imagawa-Matsumoto syndrome 618786 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability v3.227 | YARS | Sarah Leigh Added comment: Comment on phenotypes: Monoallelic variants are associated with Charcot-Marie-Tooth disease, dominant intermediate C 608323, while biallelic variants are associated with a complex phenotype that may include intellectual disability, hearing loss and liver damage. | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability v3.170 | TMEM106B |
Konstantinos Varvagiannis gene: TMEM106B was added gene: TMEM106B was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: TMEM106B was set to MONOALLELIC, autosomal or pseudoautosomal, imprinted status unknown Publications for gene: TMEM106B were set to 29186371; 29444210; 32595021 Phenotypes for gene: TMEM106B were set to Leukodystrophy, hypomyelinating, 16 (MIM #617964) Penetrance for gene: TMEM106B were set to Complete Mode of pathogenicity for gene: TMEM106B was set to Loss-of-function variants (as defined in pop up message) DO NOT cause this phenotype - please provide details in the comments Review for gene: TMEM106B was set to GREEN Added comment: 6 unrelated individuals with Leukodystrophy, hypomyelinating, 16 (MIM #617964) due to a recurrent TMEM106B variant have been reported to date in the literature (Simons et al 2017 - PMID: 29186371, Yan et al 2018 - PMID: 29444210, Ikemoto et al 2020 - PMID: 32595021). While a 3 y.o. female described by Yan et al had DD (eg sitting at 9m, walking at 25m) with normal cognitive functioning, and a 38 y.o. female had borderline intellectual functioning (IQ 76), 4 affected individuals had ID. Among them, a 19 y.o. male with severe ID was also found to harbor a second de novo possibly damaging USP7 variant. Seizures have been reported in 2 unrelated subjects. [Clinical features are also summarized in table 1 - Ikemoto et al]. All harbored NM_001134232.2(TMEM106B):c.754G>A (p.Asp252Asn) which in almost all cases occurred as a de novo event. In a single case this variant was inherited from a mosaic parent with mild DD in infancy but normal cognition (reported by Simons et al). As discussed by Ito et al (2018 - PMID: 30643851) the encoded protein is a structural component of the lysosomal membrane, playing a role on lysosome acidification. Acidity of the lysosome mediates multiple aspects of lysosomal function. Ito et al, using patient-derived fibroblasts assessed mRNA and protein levels. These were unaltered compared with controls. While TMEM106B had been previously shown to affect lysosome number, morphology and acidification, Ito et al demonstrated increased number of lysosomes in patient cells as well as impaired acidification compared to controls. As commented lysosomes are required for generation of myelin. Recurrence of this missense variant, the presence of pLoF TMEM106B variants in gnomAD as well as the phenotypically normal Tmem106b null mice suggest that this variant may have a gain-of-function or dominant negative effect. Genes for other forms of hypomyelinating lipodystrophy (incl. PLP1) have green rating in the ID panel. Overall TMEM106B can be considered for the ID panel with green rating and the epilepsy panel with amber rating. Sources: Literature |
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| Intellectual disability v3.170 | TBC1D2B |
Konstantinos Varvagiannis gene: TBC1D2B was added gene: TBC1D2B was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: TBC1D2B was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: TBC1D2B were set to 32623794 Phenotypes for gene: TBC1D2B were set to Global developmental delay; Intellectual disability; Seizures; Gingival overgrowth; Behavioral abnormality; Abnormality of the mandible; Abnormality of brain morphology; Abnormality of the eye; Hearing abnormality Penetrance for gene: TBC1D2B were set to Complete Review for gene: TBC1D2B was set to AMBER Added comment: Harms et al (2020 - PMID: 32623794) report on 3 unrelated individuals with biallelic pLoF TBC1D2B variants. Features included cognitive impairment (mild ID in one case, regression at the age of 12y in another, hypotonia and delayed milestones in a third aged 8m), seizures (3/3 - variable age of onset) and/or gingival overgrowth (2/3 - prior to initiation of AEDs). Other findings included behavioral abnormalities, mandibular anomalies, abnormal brain imaging and ophthalmologic or (rarely) audiometric evaluations. All were born to non-consanguineous couples and additional investigations were performed in some. Variants were identified by WES or trio WGS, with Sanger confirmation/compatible segregation analyses. In line with the pLoF variants, mRNA studies in fibroblasts from 2 unrelated affected individuals demonstrated significantly reduced (~80-90%) TBC1C2D mRNA levels compared to controls, restored following cycloheximide treatment. Protein was absent in patient fibroblasts. TBC-domain containing GTPase activating proteins are known as key regulators of RAB GTPase activity. TBC1D2B was shown to colocalize with RAB5-positive endocytic vesicles. CRISPR/Cas9-mediated ko of TBC1D2B in HeLa cells suggested a role in EGF receptor endocytosis and decreased cell viability of TBC1D2B-deficient HeLa cells upon serum deprivation. Genes encoding other TBC domain-containg GTPase-activating proteins, e.g. TBC1D7 and TBC1D20, TBC1D24 are associated with recessive neurodevelopmental disorders (with ID and/or seizures) and the pathophysiological defect in TBC1D2B-related disorder (deficit in vesicle trafficking and/or cell survival) is proposed to be similar to that of TBC1D24. Overall this gene can be considered for inclusion with amber/green rating in the ID panel and green in epilepsy panel. Sources: Literature |
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| Intellectual disability v3.170 | HERC2 |
Konstantinos Varvagiannis edited their review of gene: HERC2: Added comment: Please consider upgrading this gene to green in the current panel based on the following updated review (13-07-2020): Biallelic pathogenic HERC2 variants cause Mental retardation, autosomal recessive 38 (MIM 615516). The current review is based mostly on the information provided by Elpidorou et al (2020 - PMID: 32571899) summarizing the findings in several affected individuals as published in the literature. ID was a universal feature among them (27/27) and seizures were reported in some (9/27): - 22 subjects from Amish/Mennonite families were homozygous for p.Pro594Leu [NM_004667.5(HERC2):c.1781C>T] (Puffenberger et al 2012 - PMID: 23065719, Harlalka et al 2013 - PMID: 23243086, Abraham et al - PMID: 30902390) - 2 additional patients were homozygous for another missense SNV [NM_004667.5(HERC2):c.4625G>A - p.Arg1542His] (Abraham et al 2019 - PMID: 30902390) - 3 sibs born to consanguineous parents, homozygous for NM_004667.5:c.13767_13770delTGAA - p.(Asn4589LysTer4598)] as described by Elpidorou et al. - 1 male homozygous 286 kb deletion spanning several 5' exons of HERC2 as well as the first exons of OCA2 was described by Morice-Picard et al (2016 - PMID: 27759030). Despite a neurological presentation (axial hypotonia, peripheral hypertonia, extrapyramidal symptoms and uncoordinated movements) further information was not available. Apart from the cases summarized by Elpidorou et al, there have been few additional ones e.g. : - Trujillano et al (2017 - PMID: 27848944) reported briefly on a patient, homozygous for NM_004667.5:c.4676-1G>A displaying seizures, hypotonia, global DD, "Encephalopathy" and abnormality of the liver. - Yavarna et al (2015 - PMID: 26077850) provided few details with on an individual with primarily 'neurocognitive' phenotype but rather atypical presentation (MRI abnormalities, TGA, VSD, renal anomaly, growth retardation, hearing loss) due to p.Q3164X variant (recessive inheritance was specified). Several lines of evidence support an important role for the protein encoded (an E3 ubiquitin protein ligase, interacting also with UBE3A, involved in several cellular processes incl. cell cycle regulation, spindle formation during mitosis, mitochondrial functions, DNA damage responses by targeting proteins such as XPA) as well as the effect of the reported variants (mRNA studies, Western blot, detection of a fusion transcript in the case of the deletion, etc). Individuals from the Amish families displayed Angelman-like features (in line with HERC2-UBE3A interaction) with - among others - gait instability. Mouse models recapitulate some of these features (e.g. the movement disorder) as extensively discussed by Abraham et al. Overall this gene can be included in the ID and epilepsy panels with green rating. -----; Changed rating: GREEN; Changed publications: 23065719, 23243086, 30902390, 32571899, 27848944, 26077850, 27759030 |
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| Intellectual disability v3.3 | SUZ12 | Zornitza Stark edited their review of gene: SUZ12: Changed phenotypes: Imagawa-Matsumoto syndrome, MIM# 618786, Intellectual disability, Overgrowth | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability v3.0 | CLDN19 | Zornitza Stark reviewed gene: CLDN19: Rating: RED; Mode of pathogenicity: None; Publications: ; Phenotypes: Hypomagnesemia 5, renal, with ocular involvement, MIM# 248190; Mode of inheritance: None | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability v3.0 | SUPT16H |
Konstantinos Varvagiannis gene: SUPT16H was added gene: SUPT16H was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: SUPT16H was set to MONOALLELIC, autosomal or pseudoautosomal, imprinted status unknown Publications for gene: SUPT16H were set to http://dx.doi.org/10.1136/jmedgenet-2019-106193 Phenotypes for gene: SUPT16H were set to Global developmental delay; Intellectual disability; Abnormality of the corpus callosum Penetrance for gene: SUPT16H were set to Complete Review for gene: SUPT16H was set to AMBER Added comment: Bina et al (2020 - http://dx.doi.org/10.1136/jmedgenet-2019-106193) report on 4 unrelated individuals with heterozygous SNVs affecting SUPT16H as well as 1 further with microdeletion spanning this gene. The phenotype consisted of DD with subsequent ID in a subset of them (ages of the cohort: 2y-14y), autistic features in few, abnormalities of the corpus callosum (for 3 with available MRI images), variable gastrointestinal problems in some, and possibly minor dysmorphic features. SUPT16H encodes a subunit of the FACT (facilitates chromatin transcription) complex, a chromatin-specific factor required for transcription elongation as well as for DNA replication and repair (OMIM citing Belotserkovskaya et al. 2003 - PMID: 12934006). The 2 subunits of the complex [Spt16 (encoded by SUPT16H) and SSRP1] are essential for histone regulation. As the authors note, Spt16 interacts with the histone dimer H2A-H2B during transcription to allow RNA polymerase access to previously coiled DNA [cited PMIDs : 9489704, 10421373 / A recent study by Liu et al 2019 (PMID: 31775157) appears highly relevant]. SUPT16H has a Z-score of 5.1 in gnomAD and a pLI of 1 (%HI of 22.56 in Decipher). SNVs : 4 de novo missense SNVs were identified following exome sequencing (NM_007192.3:c.484A>G or I162V / L432P / N571S / R734W), all absent from gnomAD and mostly predicted to be deleterious (I162V predicted benign, tolerated, disease-causing by PolyPhen2, SIFT, MutationTaster respectively and had a CADD score of 13.61). Prior work-up for these individuals (incl. CMA in some / MS-MLPA for Angelman s. in 1 / metabolic investigations) had (probably) not revealed an apparent cause, with small CNVs inherited from healthy parents (a 4q13.3 dup / 20q13.2 del - coordinates not provided). There were no studies performed for the identified variants. CNVs : A 5th individual reported by Bina et al was found to harbor a 2.05 Mb 14q11.2 deletion spanning SUPT16H. The specific deletion also spanned CHD8 while the same individual harbored also a 30.17 Mb duplication of 18p11.32q12.1. CNVs spanning SUPT16H reported to date, also span the (very) proximal CHD8. [Genomic coordinates (GRCh38) for SUPT16H and CHD8 as provided by OMIM : 14:21,351,471-21,384,018 / 14:21,385,198-21,456,122]. Haploinsufficiency of CHD8 is associated with a distinctive syndrome with overgrowth and ID (Douzgou et al 2019 - PMID: 31001818). The phenotype of SUPT16H-CHD8 duplications is discussed in other studies/reviews. [Smol et al 2020 - PMID: 31823155 / Smyk et al 2016 - PMID: 26834018]. Animal models were not commented on by Bina et al (possibly not available for mouse : http://www.informatics.jax.org/marker/MGI:1890948 / https://www.mousephenotype.org/data/genes/MGI:1890948 ). Sources: Literature |
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| Intellectual disability v3.0 | MTHFS |
Konstantinos Varvagiannis changed review comment from: Biallelic pathogenic MTHFS variants cause Neurodevelopmental disorder with microcephaly, epilepsy, and hypomyelination (# 618367). The gene encodes 5,10-Methenyltetrahydrofolate synthetase which catalyzes conversion of 5-formyltetrahydrofolate (5-FTHF or folinic acid) to 5,10-methenyltetrahydrofolate (5,10-MTHF). At least 3 unrelated individuals have been reported. The phenotype appears to be relevant to both epilepsy and ID gene panels and the role of variants/the gene supported by enzymatic activity studies, 5-FTHF accumulation, 5,10-MTHF levels (low/low-normal), the role of folate metabolism pathway overall and some supporting (metabolic) evidence from the mouse model. --- Rodan et al (2018 - PMID: 30031689) reported on 2 individuals both presenting with microcephaly, severe global DD, epilepsy, progressive spasticity and cerebral hypomyelination upon MRI imaging. Short stature was also feature in both. The 1st patient was an 8-year-old male who following exome sequencing was found to harbor 2 missense variants each inherited from a carrier parent. (NM_006441.3:c.434G>A / p.R145Q and c.107T>C / p.L36P). A further AFG3L2 indel was not felt to fit with his phenotype (and the onset of the related disorder appears to occur later). Previous investigations included extensive metabolic testing, CMA, Angelman syndrome methylation analysis, GFAP, POLG1, TYMP sequencing, mitochondrial genome analysis and an XL-ID gene panel (further suggesting relevance of this gene to the current panel) were all non-diagnostic. CSF 5-MTHF levels were initially on the low-normal range, subsequently found to be decreased (upon folinic acid supplementation) and later normalized upon use of another regimen. MTHFS activity was measured in control fibroblasts as well as fibroblasts from this individual, with the latter demonstrating no enzyme activity. Accumulation (30x elevation) of 5-FTHF (the substrate of MTHFS) was demonstrated in patient fibroblasts. The 2nd patient was a 11-year-old male with similar features incl. global DD (standing/walking/single words at/after 4 years of age, limited vocabulary and articulation upon last examination). Extensive metabolic work-up as well as genetic testing for an epilepsy panel, vanishing white matter disease gene panel, mitochondrial genome as well as specific gene sequencing (LAMA2, POLR3A, POLR3B) were all non-diagnostic. Trio exome revealed 2 MTHFS variants in trans configuration (c.484C>T / p.Q162X and c.434G>A / p.R145Q). --- Romero et al (2019 - PMID: 31844630) reported on a 4-year-old female with congenital microcephaly, severe global DD (nonverbal/nonambulatory at the age of 4), spasticity, epilepsy and cerebral hypomyelination. Extensive investigations prior to exome sequencing revealed macrocytic anemia, decreased CSF 5-MTHF and elevated neopterin, 2 CNVs of uncertain significance upon CMA with additional long ROH on chr15. Methylation studies were negative. The child was homozygous for c.220C>T / p.R74X (RefSeq is probably NM_006441.3. MTHFS lies on chr15. The parents were unrelated but came from the same town). There were no other candidate variants from the exome analysis. Both articles discuss extensively the role of the folate metabolism pathway overall in nucleic acid synthesis, AA metabolism, neurotransmitter synthesis, methylation as well as 5-FTHF / 5,10-MTHF in particular in myelin stabilization and DNA synthesis (eg. according to Romero et al. a defect in MTHFS would impair myelin production and also lead to decreased myelin stability). --- A book chapter cited by Rodan et al (in N. Blau et al. (eds.), Physician’s Guide to the Diagnosis, Treatment, and Follow-Up of Inherited Metabolic Diseases - DOI: 10.1007/978-3-642-40337-8_10) included limited details on a patient with 'MTHFS gene mutation'. This individual had early speech delay, seizures beginning in infancy, ID, autistic features, recurrent infections and was found to have very low CSF 5-MTHF levels. [Details in p169 and table 10.6 - p173]. --- In a mouse model reported by Field et al (2011 - PMID: 22303332), Mthfs was disrupted through insertion of a gene trap vector between the first 2 exons. Heterozygous [Mthfs(gt/+)] mice were fertile and viable. Mthfs protein levels were slightly but not statistically significantly reduced in tissues measured. No homozygous embryos were recovered following intercrosses of heterozygous mice, suggesting that Mthfs is an essential gene. Mouse embryonic fibroblasts from heterozygous mice [Mthfs (gt/+)] exhibited reduced de novo purine biosynthesis, but did not exhibit altered de novo thymidylate biosynthesis. Plasma folate levels were altered in heterozygous mice on a standard (/control) diet. Sources: Literature; to: Biallelic pathogenic MTHFS variants cause Neurodevelopmental disorder with microcephaly, epilepsy, and hypomyelination (# 618367). The gene encodes 5,10-Methenyltetrahydrofolate synthetase which catalyzes conversion of 5-formyltetrahydrofolate (5-FTHF or folinic acid) to 5,10-methenyltetrahydrofolate (5,10-MTHF). At least 3 unrelated individuals have been reported. The phenotype appears to be relevant to both epilepsy and ID gene panels and the role of variants/the gene supported by enzymatic activity studies, 5-FTHF accumulation, 5,10-MTHF levels (low/low-normal), the role of folate metabolism pathway overall and some supporting (metabolic) evidence from the mouse model. --- Rodan et al (2018 - PMID: 30031689) reported on 2 individuals both presenting with microcephaly, severe global DD, epilepsy, progressive spasticity and cerebral hypomyelination upon MRI imaging. Short stature was also feature in both. The 1st patient was an 8-year-old male who following exome sequencing was found to harbor 2 missense variants each inherited from a carrier parent. (NM_006441.3:c.434G>A / p.R145Q and c.107T>C / p.L36P). A further AFG3L2 indel was not felt to fit with his phenotype (and the onset of the related disorder appears to occur later). Previous investigations included extensive metabolic testing, CMA, Angelman syndrome methylation analysis, GFAP, POLG1, TYMP sequencing, mitochondrial genome analysis and an XL-ID gene panel (further suggesting relevance of this gene to the current panel) were all non-diagnostic. CSF 5-MTHF levels were initially on the low-normal range, subsequently found to be decreased (upon folinic acid supplementation) and later normalized upon use of another regimen. MTHFS activity was measured in control fibroblasts as well as fibroblasts from this individual, with the latter demonstrating no enzyme activity. Accumulation (30x elevation) of 5-FTHF (the substrate of MTHFS) was demonstrated in patient fibroblasts. The 2nd patient was a 11-year-old male with similar features incl. global DD (standing/walking/single words at/after 4 years of age, limited vocabulary and articulation upon last examination). Extensive metabolic work-up as well as genetic testing for an epilepsy panel, vanishing white matter disease gene panel, mitochondrial genome as well as specific gene sequencing (LAMA2, POLR3A, POLR3B) were all non-diagnostic. Trio exome revealed 2 MTHFS variants in trans configuration (c.484C>T / p.Q162X and c.434G>A / p.R145Q). --- Romero et al (2019 - PMID: 31844630) reported on a 4-year-old female with congenital microcephaly, severe global DD (nonverbal/nonambulatory at the age of 4), spasticity, epilepsy and cerebral hypomyelination. Extensive investigations prior to exome sequencing revealed macrocytic anemia, decreased CSF 5-MTHF and elevated neopterin, 2 CNVs of uncertain significance upon CMA with additional long ROH on chr15. Methylation studies were negative. The child was homozygous for c.220C>T / p.R74X (RefSeq is probably NM_006441.3. MTHFS lies on chr15. The parents were unrelated but came from the same town). There were no other candidate variants from the exome analysis. Both articles discuss extensively the role of the folate metabolism pathway overall in nucleic acid synthesis, AA metabolism, neurotransmitter synthesis, methylation as well as 5-FTHF / 5,10-MTHF in particular in myelin stabilization and DNA synthesis (eg. according to Romero et al. a defect in MTHFS would impair myelin production and also lead to decreased myelin stability). --- A book chapter cited by Rodan et al (in N. Blau et al. (eds.), Physician’s Guide to the Diagnosis, Treatment, and Follow-Up of Inherited Metabolic Diseases - DOI: 10.1007/978-3-642-40337-8_10) included limited details on a patient with 'MTHFS gene mutation'. This individual had early speech delay, seizures beginning in infancy, ID, autistic features, recurrent infections and was found to have very low CSF 5-MTHF levels. [Details in p169 and table 10.6 - p173]. --- In a mouse model reported by Field et al (2011 - PMID: 22303332), Mthfs was disrupted through insertion of a gene trap vector between the first 2 exons. Heterozygous [Mthfs(gt/+)] mice were fertile and viable. Mthfs protein levels were slightly but not statistically significantly reduced in tissues measured. No homozygous embryos were recovered following intercrosses of heterozygous mice, suggesting that Mthfs is an essential gene. Mouse embryonic fibroblasts from heterozygous mice [Mthfs (gt/+)] exhibited reduced de novo purine biosynthesis, but did not exhibit altered de novo thymidylate biosynthesis. Plasma folate levels were altered in heterozygous mice on a standard (/control) diet. [Please consider inclusion in other possibly relevant panels e.g. for metabolic disorders] Sources: Literature |
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| Intellectual disability v3.0 | MTHFS |
Konstantinos Varvagiannis gene: MTHFS was added gene: MTHFS was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: MTHFS was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: MTHFS were set to 30031689; 31844630; 22303332; https://doi.org/10.1007/978-3-642-40337-8_10 Phenotypes for gene: MTHFS were set to Neurodevelopmental disorder with microcephaly, epilepsy, and hypomyelination, 618367 Penetrance for gene: MTHFS were set to Complete Review for gene: MTHFS was set to GREEN Added comment: Biallelic pathogenic MTHFS variants cause Neurodevelopmental disorder with microcephaly, epilepsy, and hypomyelination (# 618367). The gene encodes 5,10-Methenyltetrahydrofolate synthetase which catalyzes conversion of 5-formyltetrahydrofolate (5-FTHF or folinic acid) to 5,10-methenyltetrahydrofolate (5,10-MTHF). At least 3 unrelated individuals have been reported. The phenotype appears to be relevant to both epilepsy and ID gene panels and the role of variants/the gene supported by enzymatic activity studies, 5-FTHF accumulation, 5,10-MTHF levels (low/low-normal), the role of folate metabolism pathway overall and some supporting (metabolic) evidence from the mouse model. --- Rodan et al (2018 - PMID: 30031689) reported on 2 individuals both presenting with microcephaly, severe global DD, epilepsy, progressive spasticity and cerebral hypomyelination upon MRI imaging. Short stature was also feature in both. The 1st patient was an 8-year-old male who following exome sequencing was found to harbor 2 missense variants each inherited from a carrier parent. (NM_006441.3:c.434G>A / p.R145Q and c.107T>C / p.L36P). A further AFG3L2 indel was not felt to fit with his phenotype (and the onset of the related disorder appears to occur later). Previous investigations included extensive metabolic testing, CMA, Angelman syndrome methylation analysis, GFAP, POLG1, TYMP sequencing, mitochondrial genome analysis and an XL-ID gene panel (further suggesting relevance of this gene to the current panel) were all non-diagnostic. CSF 5-MTHF levels were initially on the low-normal range, subsequently found to be decreased (upon folinic acid supplementation) and later normalized upon use of another regimen. MTHFS activity was measured in control fibroblasts as well as fibroblasts from this individual, with the latter demonstrating no enzyme activity. Accumulation (30x elevation) of 5-FTHF (the substrate of MTHFS) was demonstrated in patient fibroblasts. The 2nd patient was a 11-year-old male with similar features incl. global DD (standing/walking/single words at/after 4 years of age, limited vocabulary and articulation upon last examination). Extensive metabolic work-up as well as genetic testing for an epilepsy panel, vanishing white matter disease gene panel, mitochondrial genome as well as specific gene sequencing (LAMA2, POLR3A, POLR3B) were all non-diagnostic. Trio exome revealed 2 MTHFS variants in trans configuration (c.484C>T / p.Q162X and c.434G>A / p.R145Q). --- Romero et al (2019 - PMID: 31844630) reported on a 4-year-old female with congenital microcephaly, severe global DD (nonverbal/nonambulatory at the age of 4), spasticity, epilepsy and cerebral hypomyelination. Extensive investigations prior to exome sequencing revealed macrocytic anemia, decreased CSF 5-MTHF and elevated neopterin, 2 CNVs of uncertain significance upon CMA with additional long ROH on chr15. Methylation studies were negative. The child was homozygous for c.220C>T / p.R74X (RefSeq is probably NM_006441.3. MTHFS lies on chr15. The parents were unrelated but came from the same town). There were no other candidate variants from the exome analysis. Both articles discuss extensively the role of the folate metabolism pathway overall in nucleic acid synthesis, AA metabolism, neurotransmitter synthesis, methylation as well as 5-FTHF / 5,10-MTHF in particular in myelin stabilization and DNA synthesis (eg. according to Romero et al. a defect in MTHFS would impair myelin production and also lead to decreased myelin stability). --- A book chapter cited by Rodan et al (in N. Blau et al. (eds.), Physician’s Guide to the Diagnosis, Treatment, and Follow-Up of Inherited Metabolic Diseases - DOI: 10.1007/978-3-642-40337-8_10) included limited details on a patient with 'MTHFS gene mutation'. This individual had early speech delay, seizures beginning in infancy, ID, autistic features, recurrent infections and was found to have very low CSF 5-MTHF levels. [Details in p169 and table 10.6 - p173]. --- In a mouse model reported by Field et al (2011 - PMID: 22303332), Mthfs was disrupted through insertion of a gene trap vector between the first 2 exons. Heterozygous [Mthfs(gt/+)] mice were fertile and viable. Mthfs protein levels were slightly but not statistically significantly reduced in tissues measured. No homozygous embryos were recovered following intercrosses of heterozygous mice, suggesting that Mthfs is an essential gene. Mouse embryonic fibroblasts from heterozygous mice [Mthfs (gt/+)] exhibited reduced de novo purine biosynthesis, but did not exhibit altered de novo thymidylate biosynthesis. Plasma folate levels were altered in heterozygous mice on a standard (/control) diet. Sources: Literature |
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| Intellectual disability v3.0 | SUZ12 |
Konstantinos Varvagiannis changed review comment from: ID can be a feature in individuals heterozygous for SUZ12 pathogenic variants. 13 affected individuals (from 12 families) have been reported: [1] PMID 28229514 (Imagawa et al, 2017) : 1 individual [2] PMID 30019515 (Imagawa et al, 2018) : 2 further unrelated subjects [3] PMID 31736240 (Cyrus et al, 2019) : 10 additional subjects (from 9 families) Reviewed by Cyrus et al, features observed in more than half of the (13) affected individuals included prenatal and/or postnatal overgrowth (in some only prenatal, others only postnatal, others did not manifest overgrowth at all), some suggestive facial features (eg. prominent forehead, hypertelorism, downslanting palpebral fissures, round face, broad/low nasal bridge), DD and ID (the latter in 7/13, in most cases mild), advanced bone age, musculoskeletal abnormalities and cryptorchidism. Less frequent features included brain MRI abnormalities (eg. CC hypoplasia/agenesis, etc.), umbilical hernias, respiratory abnormalities, cardiac anomalies (in one). All were diagnosed with WES/WGS/panel testing, with few having additional findings upon this or prior testing (eg. CNVs/SNVs). SUZ12 encodes one of the 4 core proteins of the PRC2 complex (the 3 other being encoded by EZH1/2, EED and RBBP4/7). The complex has a methyltransferase activity, catalyzing addition of up to 3 methyl groups on histone 3 at lysine residue 27 (H3K27), leading to chromatin compaction and further to gene silencing. Mutations in genes encoding 2 other core components of the PRC2 complex - namely EZH2 and EED - cause Weaver and Cohen-Gibson syndrome with overlapping phenotype incl. overgrowth, advanced bone age, craniofacial features and DD/ID. The SET domain of EZH1/2 and EED as well as the VEFS domain of SUZ12 are contributing to the catalytic activity. SUZ12 variants reported to date include missense and pLoF variants (frameshift, nonsense, splice site ones) predicted to disrupt or eliminate the VEFS-box domain [almost all missense within this domain with the exception of one proximal to it (Arg535Gln) / pLoF causing truncation prior or within this domain (Arg654Ter might be an exception)] {NP_056170.2}. Variants either occurred de novo or were inherited (~1/3), on some occasions from a mildly affected parent. Parental mosaicism has also been reported (eg. in ref1, and one or possibly two additional families in ref3). Some preliminary assumptions on possible genotype-phenotype correlations (for overgrowth and ID related to missense/pLoF variants) are discussed in ref3. SUZ12 is also be deleted in some patients with NF1 deletion (and a diagnosis of neurofibromatosis type 1). Deletion of SUZ12 has been proposed to contribute to the phenotype of these individuals (eg. overgrowth, cognitive development, facial features). [Discussed in ref1]. Functional studies have been carried out only in the first report (ref1) and demonstrated decreased trimethylation of H3K27 in the case of a missense variant. Overall a partial loss-of-function mechanism has been proposed for the variants. Mouse models: A study by Pasini et al (PMID: 15385962) did not report phenotypic differences between wt and heterozygous Suz12 knockout mice (gene-trap vector) as for size, morphology and fertility. Total knockout resulted in embryonic lethality, significant growth retardation and several developmental defects. Loss of Suz12 was shown to result in absence of di- and tri-methylated H3K27 in the ko embryos. In another study cited (Miro et al - PMID: 19535498) heterozygous mice (replacement of exons 12-16 with a lacZ gene and neo cassette) displayed variable CNS defects with incomplete penetrance. The role of the PRC2 complex and the phenotypes related to mutations in genes encoding its core components, are discussed in PMID: 31724824 (also by Cyrus et al, 2019). SUZ12 is not associated with any phenotype in OMIM. In G2P it is included in the DD panel associated with Weaver-like overgrowth syndrome (disease confidence : confirmed). The gene is also included in gene panels for ID offered by some diagnostic laboratories (eg. GeneDx). Sources: Literature; to: ID can be a feature in individuals heterozygous for SUZ12 pathogenic variants. 13 affected individuals (from 12 families) have been reported: [1] PMID 28229514 (Imagawa et al, 2017) : 1 individual [2] PMID 30019515 (Imagawa et al, 2018) : 2 further unrelated subjects [3] PMID 31736240 (Cyrus et al, 2019) : 10 additional subjects (from 9 families) Reviewed by Cyrus et al, features observed in more than half of the (13) affected individuals included prenatal and/or postnatal overgrowth (in some only prenatal, others only postnatal, others did not manifest overgrowth at all), some suggestive facial features (eg. prominent forehead, hypertelorism, downslanting palpebral fissures, round face, broad/low nasal bridge), DD and ID (the latter in 7/13, in most cases mild), advanced bone age, musculoskeletal abnormalities and cryptorchidism. Less frequent features included brain MRI abnormalities (eg. CC hypoplasia/agenesis, etc.), umbilical hernias, respiratory abnormalities, cardiac anomalies (in one). All were diagnosed with WES/WGS/panel testing, with few having additional findings upon this or prior testing (eg. CNVs/SNVs). SUZ12 encodes one of the 4 core proteins of the PRC2 complex (the 3 other being encoded by EZH1/2, EED and RBBP4/7). The complex has a methyltransferase activity, catalyzing addition of up to 3 methyl groups on histone 3 at lysine residue 27 (H3K27), leading to chromatin compaction and further to gene silencing. Mutations in genes encoding 2 other core components of the PRC2 complex - namely EZH2 and EED - cause Weaver and Cohen-Gibson syndrome with overlapping phenotype incl. overgrowth, advanced bone age, craniofacial features and DD/ID. The SET domain of EZH1/2 and EED as well as the VEFS domain of SUZ12 are contributing to the catalytic activity. SUZ12 variants reported to date include missense and pLoF variants (frameshift, nonsense, splice site ones) predicted to disrupt or eliminate the VEFS-box domain [almost all missense within this domain with the exception of one proximal to it (Arg535Gln) / pLoF causing truncation prior or within this domain (Arg654Ter might be an exception)] {NP_056170.2}. Variants either occurred de novo or were inherited (~1/3), on some occasions from a mildly affected parent. Parental mosaicism has also been reported (eg. in ref1, and one or possibly two additional families in ref3). Some preliminary assumptions on possible genotype-phenotype correlations (for overgrowth and ID related to missense/pLoF variants) are discussed in ref3. SUZ12 may also be deleted in some patients with NF1 deletion (and a diagnosis of neurofibromatosis type 1). Deletion of SUZ12 has been proposed to contribute to the phenotype of these individuals (eg. overgrowth, cognitive development, facial features). [Discussed in ref1]. Functional studies have been carried out only in the first report (ref1) and demonstrated decreased trimethylation of H3K27 in the case of a missense variant. Overall a partial loss-of-function mechanism has been proposed for the variants. Mouse models: A study by Pasini et al (PMID: 15385962) did not report phenotypic differences between wt and heterozygous Suz12 knockout mice (gene-trap vector) as for size, morphology and fertility. Total knockout resulted in embryonic lethality, significant growth retardation and several developmental defects. Loss of Suz12 was shown to result in absence of di- and tri-methylated H3K27 in the ko embryos. In another study cited (Miro et al - PMID: 19535498) heterozygous mice (replacement of exons 12-16 with a lacZ gene and neo cassette) displayed variable CNS defects with incomplete penetrance. The role of the PRC2 complex and the phenotypes related to mutations in genes encoding its core components, are discussed in PMID: 31724824 (also by Cyrus et al, 2019). SUZ12 is not associated with any phenotype in OMIM. In G2P it is included in the DD panel associated with Weaver-like overgrowth syndrome (disease confidence : confirmed). The gene is also included in gene panels for ID offered by some diagnostic laboratories (eg. GeneDx). Sources: Literature |
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| Intellectual disability v3.0 | SUZ12 |
Konstantinos Varvagiannis changed review comment from: ID can be a feature in individuals heterozygous for SUZ12 pathogenic variants. 13 affected individuals (from 12 families) have been reported: [1] PMID 28229514 (Imagawa et al, 2017) : 1 individual [2] PMID 30019515 (Imagawa et al, 2018) : 2 further unrelated subjects [3] PMID 31736240 (Cyrus et al, 2019) : 10 newly diagnosed subjects (from 9 families) Reviewed by Cyrus et al, features observed in more than half of the (13) affected individuals included prenatal and/or postnatal overgrowth (in some only prenatal, others only postnatal, others did not manifest overgrowth at all), some suggestive facial features (eg. prominent forehead, hypertelorism, downslanting palpebral fissures, round face, broad/low nasal bridge), DD and ID (the latter in 7/13, in most cases mild), advanced bone age, musculoskeletal abnormalities and cryptorchidism. Less frequent features included brain MRI abnormalities (eg. CC hypoplasia/agenesis, etc.), umbilical hernias, respiratory abnormalities, cardiac anomalies (in one). All were diagnosed with WES/WGS/panel testing, with few having additional findings upon this or prior testing (eg. CNVs/SNVs). SUZ12 encodes one of the 4 core proteins of the PRC2 complex (the 3 other being encoded by EZH1/2, EED and RBBP4/7). The complex has a methyltransferase activity, catalyzing addition of up to 3 methyl groups on histone 3 at lysine residue 27 (H3K27), leading to chromatin compaction and further to gene silencing. Mutations in genes encoding 2 other core components of the PRC2 complex - namely EZH2 and EED - cause Weaver and Cohen-Gibson syndrome with overlapping phenotype incl. overgrowth, advanced bone age, craniofacial features and DD/ID. The SET domain of EZH1/2 and EED as well as the VEFS domain of SUZ12 are contributing to the catalytic activity. SUZ12 variants reported to date include missense and pLoF variants (frameshift, nonsense, splice site ones) predicted to disrupt or eliminate the VEFS-box domain [almost all missense within this domain with the exception of one proximal to it (Arg535Gln) / pLoF causing truncation prior or within this domain (Arg654Ter might be an exception)] {NP_056170.2}. Variants either occurred de novo or were inherited (~1/3), on some occasions from a mildly affected parent. Parental mosaicism has also been reported (eg. in ref1, and one or possibly two additional families in ref3). Some preliminary assumptions on possible genotype-phenotype correlations (for overgrowth and ID related to missense/pLoF variants) are discussed in ref3. SUZ12 is also be deleted in some patients with NF1 deletion (and a diagnosis of neurofibromatosis type 1). Deletion of SUZ12 has been proposed to contribute to the phenotype of these individuals (eg. overgrowth, cognitive development, facial features). [Discussed in ref1]. Functional studies have been carried out only in the first report (ref1) and demonstrated decreased trimethylation of H3K27 in the case of a missense variant. Overall a partial loss-of-function mechanism has been proposed for the variants. Mouse models: An study by Pasini et al (PMID: 15385962) did not report phenotypic differences between wt and heterozygous Suz12 knockout mice (gene-trap vector) as for size, morphology and fertility. Total knockout resulted in embryonic lethality, significant growth retardation and several developmental defects. Loss of Suz12 was shown to result in absence of di- and tri-methylated H3K27 in the ko embryos. In another study cited (Miro et al - PMID: 19535498) heterozygous mice (replacement of exons 12-16 with a lacZ gene and neo cassette) displayed variable CNS defects with incomplete penetrance. The role of the PRC2 complex and the phenotypes related to mutations in genes encoding its core components, are discussed in PMID: 31724824 (also by Cyrus et al, 2019). SUZ12 is not associated with any phenotype in OMIM. In G2P it is included in the DD panel associated with Weaver-like overgrowth syndrome (disease confidence : confirmed). The gene is also included in gene panels for ID offered by some diagnostic laboratories (eg. GeneDx). Sources: Literature; to: ID can be a feature in individuals heterozygous for SUZ12 pathogenic variants. 13 affected individuals (from 12 families) have been reported: [1] PMID 28229514 (Imagawa et al, 2017) : 1 individual [2] PMID 30019515 (Imagawa et al, 2018) : 2 further unrelated subjects [3] PMID 31736240 (Cyrus et al, 2019) : 10 additional subjects (from 9 families) Reviewed by Cyrus et al, features observed in more than half of the (13) affected individuals included prenatal and/or postnatal overgrowth (in some only prenatal, others only postnatal, others did not manifest overgrowth at all), some suggestive facial features (eg. prominent forehead, hypertelorism, downslanting palpebral fissures, round face, broad/low nasal bridge), DD and ID (the latter in 7/13, in most cases mild), advanced bone age, musculoskeletal abnormalities and cryptorchidism. Less frequent features included brain MRI abnormalities (eg. CC hypoplasia/agenesis, etc.), umbilical hernias, respiratory abnormalities, cardiac anomalies (in one). All were diagnosed with WES/WGS/panel testing, with few having additional findings upon this or prior testing (eg. CNVs/SNVs). SUZ12 encodes one of the 4 core proteins of the PRC2 complex (the 3 other being encoded by EZH1/2, EED and RBBP4/7). The complex has a methyltransferase activity, catalyzing addition of up to 3 methyl groups on histone 3 at lysine residue 27 (H3K27), leading to chromatin compaction and further to gene silencing. Mutations in genes encoding 2 other core components of the PRC2 complex - namely EZH2 and EED - cause Weaver and Cohen-Gibson syndrome with overlapping phenotype incl. overgrowth, advanced bone age, craniofacial features and DD/ID. The SET domain of EZH1/2 and EED as well as the VEFS domain of SUZ12 are contributing to the catalytic activity. SUZ12 variants reported to date include missense and pLoF variants (frameshift, nonsense, splice site ones) predicted to disrupt or eliminate the VEFS-box domain [almost all missense within this domain with the exception of one proximal to it (Arg535Gln) / pLoF causing truncation prior or within this domain (Arg654Ter might be an exception)] {NP_056170.2}. Variants either occurred de novo or were inherited (~1/3), on some occasions from a mildly affected parent. Parental mosaicism has also been reported (eg. in ref1, and one or possibly two additional families in ref3). Some preliminary assumptions on possible genotype-phenotype correlations (for overgrowth and ID related to missense/pLoF variants) are discussed in ref3. SUZ12 is also be deleted in some patients with NF1 deletion (and a diagnosis of neurofibromatosis type 1). Deletion of SUZ12 has been proposed to contribute to the phenotype of these individuals (eg. overgrowth, cognitive development, facial features). [Discussed in ref1]. Functional studies have been carried out only in the first report (ref1) and demonstrated decreased trimethylation of H3K27 in the case of a missense variant. Overall a partial loss-of-function mechanism has been proposed for the variants. Mouse models: A study by Pasini et al (PMID: 15385962) did not report phenotypic differences between wt and heterozygous Suz12 knockout mice (gene-trap vector) as for size, morphology and fertility. Total knockout resulted in embryonic lethality, significant growth retardation and several developmental defects. Loss of Suz12 was shown to result in absence of di- and tri-methylated H3K27 in the ko embryos. In another study cited (Miro et al - PMID: 19535498) heterozygous mice (replacement of exons 12-16 with a lacZ gene and neo cassette) displayed variable CNS defects with incomplete penetrance. The role of the PRC2 complex and the phenotypes related to mutations in genes encoding its core components, are discussed in PMID: 31724824 (also by Cyrus et al, 2019). SUZ12 is not associated with any phenotype in OMIM. In G2P it is included in the DD panel associated with Weaver-like overgrowth syndrome (disease confidence : confirmed). The gene is also included in gene panels for ID offered by some diagnostic laboratories (eg. GeneDx). Sources: Literature |
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| Intellectual disability v3.0 | SUZ12 |
Konstantinos Varvagiannis gene: SUZ12 was added gene: SUZ12 was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: SUZ12 was set to MONOALLELIC, autosomal or pseudoautosomal, imprinted status unknown Publications for gene: SUZ12 were set to 28229514; 30019515; 31736240; 15385962; 19535498; 31724824 Phenotypes for gene: SUZ12 were set to Overgrowth; Global developmental delay; Intellectual disability; Accelerated skeletal maturation; Abnormality of the skeletal system; Abnormality of the genitourinary system; Abnormality of the corpus callosum; Abnormality of the respiratory system; Abnormality of the abdominal wall Penetrance for gene: SUZ12 were set to unknown Review for gene: SUZ12 was set to GREEN Added comment: ID can be a feature in individuals heterozygous for SUZ12 pathogenic variants. 13 affected individuals (from 12 families) have been reported: [1] PMID 28229514 (Imagawa et al, 2017) : 1 individual [2] PMID 30019515 (Imagawa et al, 2018) : 2 further unrelated subjects [3] PMID 31736240 (Cyrus et al, 2019) : 10 newly diagnosed subjects (from 9 families) Reviewed by Cyrus et al, features observed in more than half of the (13) affected individuals included prenatal and/or postnatal overgrowth (in some only prenatal, others only postnatal, others did not manifest overgrowth at all), some suggestive facial features (eg. prominent forehead, hypertelorism, downslanting palpebral fissures, round face, broad/low nasal bridge), DD and ID (the latter in 7/13, in most cases mild), advanced bone age, musculoskeletal abnormalities and cryptorchidism. Less frequent features included brain MRI abnormalities (eg. CC hypoplasia/agenesis, etc.), umbilical hernias, respiratory abnormalities, cardiac anomalies (in one). All were diagnosed with WES/WGS/panel testing, with few having additional findings upon this or prior testing (eg. CNVs/SNVs). SUZ12 encodes one of the 4 core proteins of the PRC2 complex (the 3 other being encoded by EZH1/2, EED and RBBP4/7). The complex has a methyltransferase activity, catalyzing addition of up to 3 methyl groups on histone 3 at lysine residue 27 (H3K27), leading to chromatin compaction and further to gene silencing. Mutations in genes encoding 2 other core components of the PRC2 complex - namely EZH2 and EED - cause Weaver and Cohen-Gibson syndrome with overlapping phenotype incl. overgrowth, advanced bone age, craniofacial features and DD/ID. The SET domain of EZH1/2 and EED as well as the VEFS domain of SUZ12 are contributing to the catalytic activity. SUZ12 variants reported to date include missense and pLoF variants (frameshift, nonsense, splice site ones) predicted to disrupt or eliminate the VEFS-box domain [almost all missense within this domain with the exception of one proximal to it (Arg535Gln) / pLoF causing truncation prior or within this domain (Arg654Ter might be an exception)] {NP_056170.2}. Variants either occurred de novo or were inherited (~1/3), on some occasions from a mildly affected parent. Parental mosaicism has also been reported (eg. in ref1, and one or possibly two additional families in ref3). Some preliminary assumptions on possible genotype-phenotype correlations (for overgrowth and ID related to missense/pLoF variants) are discussed in ref3. SUZ12 is also be deleted in some patients with NF1 deletion (and a diagnosis of neurofibromatosis type 1). Deletion of SUZ12 has been proposed to contribute to the phenotype of these individuals (eg. overgrowth, cognitive development, facial features). [Discussed in ref1]. Functional studies have been carried out only in the first report (ref1) and demonstrated decreased trimethylation of H3K27 in the case of a missense variant. Overall a partial loss-of-function mechanism has been proposed for the variants. Mouse models: An study by Pasini et al (PMID: 15385962) did not report phenotypic differences between wt and heterozygous Suz12 knockout mice (gene-trap vector) as for size, morphology and fertility. Total knockout resulted in embryonic lethality, significant growth retardation and several developmental defects. Loss of Suz12 was shown to result in absence of di- and tri-methylated H3K27 in the ko embryos. In another study cited (Miro et al - PMID: 19535498) heterozygous mice (replacement of exons 12-16 with a lacZ gene and neo cassette) displayed variable CNS defects with incomplete penetrance. The role of the PRC2 complex and the phenotypes related to mutations in genes encoding its core components, are discussed in PMID: 31724824 (also by Cyrus et al, 2019). SUZ12 is not associated with any phenotype in OMIM. In G2P it is included in the DD panel associated with Weaver-like overgrowth syndrome (disease confidence : confirmed). The gene is also included in gene panels for ID offered by some diagnostic laboratories (eg. GeneDx). Sources: Literature |
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| Intellectual disability v2.1135 | TRAPPC4 |
Konstantinos Varvagiannis gene: TRAPPC4 was added gene: TRAPPC4 was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: TRAPPC4 was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: TRAPPC4 were set to 31794024 Phenotypes for gene: TRAPPC4 were set to Feeding difficulties; Progressive microcephaly; Intellectual disability; Seizures; Spastic tetraparesis; Abnormality of the face; Scoliosis; Cortical visual impairment; Hearing impairment Penetrance for gene: TRAPPC4 were set to Complete Review for gene: TRAPPC4 was set to GREEN Added comment: Van Bergen et al. (2019 - PMID: 31794024) report on 7 affected individuals from 3 famillies (only 1 of which consanguineous), all homozygous for a TRAPPC4 splicing variant. Overlapping features included feeding difficulties, progressive microcephaly, severe to profound developmental disability (7/7 - DD also prior to the onset of seizures / regression also reported in 3), epilepsy (7/7 - onset in the first year), spastic quadriparesis. Other findings in some/few incl. scoliosis, cortical visual and hearing impairment. Some facial features were shared (eg. bitemporal narrowing, long philtrum, open mouth with thin tented upper lip, pointed chin, etc). Brain imaging demonstrated abnormalities in those performed (among others cerebral with/without cerebellar atrophy). Work-up prior to exome sequencing was normal (highly variable incl. metabolic testing, CMA, MECP2, CDKL5, mitochondrial depletion studies, etc). Exome of affected individuals (and parents +/- affected sibs in some families) revealed a homozygous TRAPPC4 splicing variant [NM_016146.5:c.454+3A>G / chr11:g.118890966A>G (hg19)]. Sanger sequencing confirmed variant in affecteds, heterozygosity in parents and compatible genotypes with disease status in sibs/other members. Families were of Caucasian/Turkish and French-Canadian ethnicities. SNP array to compare haplotypes between affecteds in 2 families did not reveal a shared haplotype (/founder effect) and the variant is present in gnomAD (68/281054 - no hmz) in many populations (European/Asian/African/Latino) [https://gnomad.broadinstitute.org/variant/11-118890966-A-G]. mRNA studies in fibroblasts from an affected individual confirmed the splicing defect (2 RT-PCR products corresponding to wt and a shorter due to skipping of exon 3, the latter further confirmed by Sanger sequencing. The shorter transcript is not present in controls). qPCR revealed that the normal transript in patient fibroblasts was present at 6% of the level observed in control fibroblasts (or 54% in the case of a heterozygote parent compared to controls). Western blot in patient fibroblasts, revealed presence of full-length protein in significantly reduced levels compared to fibroblasts from carrier parents or controls. There was no band using an antibody targeting the N-terminal region of the protein prior to exon 3, suggesting that NMD applies (skipping of ex3 is also predicted to lead to frameshift). TRAPPC4 encodes one of the core proteins of the TRAPP complex. Use of different accessory proteins leads to formation of 2 distinct complexes (TRAPPII / III). The complex has an important role in intracellular trafficking. Both TRAPPII & TRAPPIII have a function in the secretory pathway, while complex III has a role also in autophagy. Core proteins are important for the complex stability. The TRAPP complex serves as a GEF for Ypt/Rab GTPases [several refs in article]. Mutations in genes for other proteins of the complex lead to neurodevelopmental disorders with associated ID ('TRAPPopathies' used by the authors / TRAPPC12, C6B, C9 green in the current panel). Western blot suggested that levels of other TRAPP subunits (TRAPPC2 or C12) under denaturing conditions, although PAGE/size exclusion chromatography suggested that the levels of fully-assembled TRAPP complexes were lower in affected individuals. Studies in patient fibroblasts showed a secretory defect (between ER, Golgi and the plasma membrane) which was restored upon lentiviral transduction with wt TRAPPC4 construct. Basal and starvation-induced autophagy were also impaired in patient fibroblasts (increased LC3 marker and LC3-positive structures / impaired co-localization with lysosomes) partly due to defective autophagosome formation (/sealing). TRAPPC4 is the human orthologue of the yeast Trs23. In a yeast model of reduced Trs23 (due to temperature instability) the authors demonstrated impaired assembly of the TRAPP core. The yeast model recapitulated the autophagy as well as well as the secretory defect observed in patient fibroblasts. Sources: Literature |
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| Intellectual disability v2.1098 | SCAMP5 |
Konstantinos Varvagiannis gene: SCAMP5 was added gene: SCAMP5 was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: SCAMP5 was set to MONOALLELIC, autosomal or pseudoautosomal, imprinted status unknown Publications for gene: SCAMP5 were set to 31439720; 20071347 Phenotypes for gene: SCAMP5 were set to Global developmental delay; Intellectual disability; Seizures; Abnormality of nervous system morphology; Behavioral abnormality Penetrance for gene: SCAMP5 were set to unknown Mode of pathogenicity for gene: SCAMP5 was set to Loss-of-function variants (as defined in pop up message) DO NOT cause this phenotype - please provide details in the comments Review for gene: SCAMP5 was set to AMBER Added comment: PMID: 31439720 (Hubert et al. 2019) reported on 2 unrelated individuals with severe ID, seizures behavioral and brain MRI abnormalities (white matter hyperintensity and mesial temporal sclorosis), both harboring the same missense SCAMP5 mutation as a de novo event (NM_001178111.1:c.538G>T or p.Gly180Trp). Previously aCGH +/- metabolic workup were non diagnostic. The occurrence of the same de novo variant in both as well as the similar presentation (incl. MRI images) suggested SCAMP5 as the most probable candidate gene, despite presence of few other variants in both. SCAMP5 is highly expressed in brain (https://www.proteinatlas.org/ENSG00000198794-SCAMP5) and previous studies have suggested a role in synaptic vesicle trafficking (PMIDs cited: 29562188, 25057210, etc). Cultured skin fibroblasts from affected individuals failed to express SCAMP5. Scamp is the Drosophila orthologue, with previous studies having demonstrated that mutants display defects in climbing, olfactory-assisted memory and susceptibility to heat induced seizures (PMIDs cited: 25478561, 19144841). Expression of the Scamp Gly302Trp variant in Drosophila ('equivalent' to the SCAMP5 Gly180Trp) revealed strongly reduced levels for the variant compared with wt upon Western Blot, either due to reduced expression or due to increased turnover. Overall the effect of Gly302Trp expression was similar to Scamp knockdown by RNAi (eg. rough eye phenotype, reduced ability to climb the walls of a graded tube after tapping, less/no flies reaching adult stage) but significantly different compared to wt. As a result, a dominant-negative effect was presumed. ---------- PMID: 20071347 (Castermans et al. 2010) is cited as a previous report of a relevant affected individual. In this study a 40 y.o. male with early DD, mild ID (IQ of 63) and ASD was found to harbor a de novo apparently balanced t(1;15) translocation affecting CLIC4 and PPCDC (both not associated with ID). [1-Mb resolution aCGH revealed no relevant CNVs]. Studies were however focused on SCAMP5 given that the gene is located downstream of / proximal to PPCDC, has brain-enriched expression as well as involvement in synaptic trafficking and demonstrated: - Less than 50% expression upon quantitative RT-PCR in patients leukocytes, compared to control. - Silencing and overexpression of Scamp5 in mouse β-TC3 cells resulted in increased and suppressed respectively secretion of large dense-core vesicles (LDCVs). - Given conservation of some components involved in secretion of dense core granules (DCGs) in platelets and LDCVs in neuronal cells, study of patient platelets - where SCAMP5 was confirmed to be expressed - suggested an altered pattern of DCGs. ---------- SCAMP5 is not associated with any phenotype in OMIM/G2P/SysID and not commonly included in gene panels for ID. ---------- Overall, this gene could be considered for inclusion in the ID and epilepsy panels probably with amber (# of unrelated individuals, 1 recurrent de novo variant and 1 regulatory effect, gene expressed in brain with a role in synaptic vesicle trafficking) or red rating (pending further evidence). Sources: Literature |
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| Intellectual disability v2.1098 | PCYT2 |
Konstantinos Varvagiannis gene: PCYT2 was added gene: PCYT2 was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: PCYT2 was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: PCYT2 were set to 31637422 Phenotypes for gene: PCYT2 were set to Global developmental delay; Developmental regression; Intellectual disability; Spastic paraparesis; Seizures; Spastic tetraparesis; Cerebral atrophy; Cerebellar atrophy Penetrance for gene: PCYT2 were set to Complete Review for gene: PCYT2 was set to GREEN Added comment: Vaz et al. (2019 - PMID: 31637422 - DDD study among the co-authors) report on 5 individuals - from 4 families - with biallelic PCYT2 mutations. The phenotype corresponded to a complex hererditary paraplegia with global DD, regression (4/5), ID (mild in 3/5, severe in 2/5), spastic para-/tetraparesis, epilepsy (5/5 - variable onset 2-16 yrs - focal or tonic-clonic seizures) and progressive cerebral and cerebellar atrophy. Exome sequencing in all revealed biallelic PCYT2 variants, confirmed with Sanger s. in probands and their parents (NM_001184917.2 - corresponding to the canonical transcript used as Ref below): - P1 (Fam1) : 2 missense SNVs in trans configuration, c.730C>T or p.His244Tyr and c.920C>T or p.Pro307Leu - P2 (Fam2 - consanguineous of White British origin), P3 (Fam3 - Consanguineous of Turkish origin), P4,5 (Fam4 - consanguineous, unspecified origin) : homozygosity for c.1129C>T or p.Arg377Ter) affecting the last exon of 8/12 transcripts, including the canonical one. Individuals with the same genotype displayed variable degrees of ID (eg P3 - severe / P2, P4,5 - mild ID). For sibs in Fam4, homozygosity for a missense SACS variant led to consideration of the respective disorder (AR spastic ataxia of Charlevoix-Saguenay) though the variant was predicted to be tolerated in silico and notably the MRI images not suggestive. All variants were absent from / had extremely low AF in public databases, with no homozygotes. Posphatidylethanolamine (PE) is a membrane lipid, particularly enriched in human brain (45% of phospholypid fraction). PE is synthesized either via the CDP-ethanolamine pathway or by decarboxylation of phosphatidylserine in mitochondria. PCYT2 encodes CTP:phosophoethanolamine cytidyltransferase (ET) which is an ubiquitously expressed rate-limiting enzyme for PE biosynthesis in the former pathway. In silico, the 2 missense variants - localizing in the CTP catalytic domain 2 - were predicted to be damaging, as well as to affect protein stability. Fibroblasts of 3 patients (P1, P2, P3) representing all variants were studied: - Enzymatic activity was shown to be significantly reduced (though not absent) compared to controls. Abnormalities were noted upon Western Blot incl. absence in all 3 patients studied of one of the 2 bands normally found in controls (probably representing the longer isoform), reduced intensity in all 3 of another band probably corresponding to a shorter isoform, and presence of an additional band of intermediate molec. mass in patients with the truncating variant. - RT-PCR on mRNA from patient fibroblasts did not reveal (significant) reduction compared to controls. - Lipidomic profile of patient fibroblasts was compatible with the location of the block in the phospholipid biosynthesis pathway and different from controls. The lipidomic profile had similarities with what has been reported for EPT1 deficiency, the enzyme directly downstream of ET. The SELENO1-related phenotype (/EPT1 deficiency) is also highly overlapping. CRISPR-Cas9 was used to generate pcyt2 partial or complete knockout (ko) zebrafish, targeting either the final (ex13) or another exon (ex3) respectively. mRNA expression was shown to be moderately reduced in the first case and severely reduced/absent in the second, compared to wt. Similarly, complete-ko (ex3) led to significantly lower survival, with impaired though somewhat better survival of partial-ko (ex13) zebrafish. Complete knockout of Pcyt2 in mice is embryonically lethal (PMID cited: 17325045) while heterozygous mice develop features of metabolic syndrome (PMID cited: 22764088). Given lethality in knockout zebrafish / mice and the residual activity (15-20%) in patient fibroblasts, the variants reported were thought to be hypomorphic and complete loss of function possibly incompatible with life. PCYT2 is not associated with any phenotype in OMIM/G2P/SysID and not commonly included in gene panels for ID. As a result this gene could included in the ID / epilepsy panels with green (~/>3 indiv/fam/variants with the nonsense found in different populations, consistent phenotype, lipidomics, in silico/in vitro/in vivo evidence) or amber rating. [Please consider inclusion in other possibly relevant panels eg. for metabolic disorders, etc]. Sources: Literature |
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| Intellectual disability v2.1063 | SMPD4 | Louise Daugherty Added comment: Comment on publications: Magini P et al. (October 2019) Loss of SMPD4 Causes a Developmental Disorder Characterized by Microcephaly and Congenital Arthrogryposis. | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability v2.1046 | PMPCB |
Konstantinos Varvagiannis changed review comment from: Biallelic pathogenic PMPCB variants cause, Multiple mitochondrial dysfunctions syndrome 6 (MIM 617954). 5 relevant individuals from 4 unrelated families (in one case consanguineous) have been reported by Vögtle et al. (2018 - PMID: 29576218). Onset of symptoms (eg. hypotonia) often preceded a period of developmental regression/stagnation which was common in all individuals and occurred within the first 2 years of life, usually following febrile illness. In all cases neurological features were severe (lack of ambulation/speech). Seizures were observed in 4 individuals from 3 families, with onset at the age of 11-24m. MRI images demonstrated T2 signal hyperintensities of the basal ganglia with cerebellar and cerebral atrophy in some. Deterioration with early death was reported on three occasions, though some years after symptom onset. Following exclusion of other diagnoses in some cases (eg. aCGH, epilepsy panel), WES identified biallelic PMPCB missense variants, supported by Sanger confirmation and segregation studies. The following variants were reported (NM_004279.2): - c.523C>T (p.Arg175Cys) in trans with c.601G>C (p.Ala201Pro) [Fam A and B] - c.524G>A (p.Arg175His) in trans with c.530T>G (p.Val177Gly) [Fam C] - c.1265T>C (p.Ile422Thr) in homozygous state [Fam D with 2 affected sibs] The gene encodes the catalytic (beta) subunit of the mitochondrial processing protease (MPP) which is responsible for the cleavage/maturation of nuclear-encoded mitochondrial precursor proteins after their import in mitochondria. The alpha subunit is encoded by PMPCA (green rating proposed for this panel). Extensive studies demonstrated (perhaps a better summary provided by OMIM): - Reduced PMPCB protein levels in mitochondria isolated from patient fibroblasts or patient-derived pluripotent stem cells. - Frataxin maturation was impaired with accumulation of the intermediate form and lower amounts of mature FXN, indicating decrease in MPP activity. - Analysis of the homologous Mas1 S. cerevisiae mutants was carried out, with the exception of Ile422Thr (corresponding to Mas1 - Ile398Thr), the introduction of which did not yield viable yiest strains. Homologous mutations led to a temperature-sensitive phenotype with accumulation of immature/unprocessed precursor proteins and decrease of mature/processed forms both in vivo or in organello (following isolation of mitochondria). Under conditions of heat stress, Mas1 mutations decreased biogenesis of Fe-S clusters. - Respiratory chain complexes I-III contain Fe-S clusters. In muscle biopsy from an affected individual, complex II activity was significantly reduced (although this was not the case in fibroblasts or liver biopsy). Dysfunction of mitochondrial and cytosolic Fe-S cluster-dependent enzymes (eg. aconitase) was also shown in muscle tissue. Regression/stagnation with seizures/non-achievement of milestones may justify testing for an ID / epilepsy gene panel. In addition, metabolic studies or mitochondrial respiratory chain complex studies were sometimes non-informative (lactate elevated in 3/5 subjects) or not carried out at all / in relevant tissues (muscle biopsy in 2 individuals, fibroblasts/liver biopsy did not demonstrate reduced complex activity when tested). PMPCB is included in the ID gene panel of Radboudumc, as well as the SysID database. The gene is included in the DD panel of G2P associated with "Neurodegeneration in Early Childhood" (disease confidence : probable). As a result, PMPCB can be considered for inclusion in both epilepsy and ID panels as green (or amber). Sources: Literature, Radboud University Medical Center, Nijmegen; to: Biallelic pathogenic PMPCB variants cause, Multiple mitochondrial dysfunctions syndrome 6 (MIM 617954). 5 relevant individuals from 4 unrelated families (in one case consanguineous) have been reported by Vögtle et al. (2018 - PMID: 29576218). Onset of symptoms (eg. hypotonia) often preceded a period of developmental regression/stagnation which was common in all individuals and occurred within the first 2 years of life, usually following febrile illness. In all cases neurological features were severe (lack of ambulation/speech). Seizures were observed in 4 individuals from 3 families, with onset at the age of 11-24m. MRI images demonstrated T2 signal hyperintensities of the basal ganglia with cerebellar and cerebral atrophy in some. Deterioration with early death was reported on three occasions, though some years after symptom onset. Following exclusion of other diagnoses in some cases (eg. aCGH, epilepsy panel), WES identified biallelic PMPCB missense variants, supported by Sanger confirmation and segregation studies. The following variants were reported (NM_004279.2): - c.523C>T (p.Arg175Cys) in trans with c.601G>C (p.Ala201Pro) [Fam A and B] - c.524G>A (p.Arg175His) in trans with c.530T>G (p.Val177Gly) [Fam C] - c.1265T>C (p.Ile422Thr) in homozygous state [Fam D with 2 affected sibs] The gene encodes the catalytic (beta) subunit of the mitochondrial processing protease (MPP) which is responsible for the cleavage/maturation of nuclear-encoded mitochondrial precursor proteins after their import in mitochondria. The alpha subunit is encoded by PMPCA (green rating proposed for this panel). Extensive studies demonstrated (perhaps a better summary provided by OMIM): - Reduced PMPCB protein levels in mitochondria isolated from patient fibroblasts or patient-derived pluripotent stem cells. - Frataxin maturation was impaired with accumulation of the intermediate form and lower amounts of mature FXN, indicating decrease in MPP activity. - Analysis of the homologous Mas1 S. cerevisiae mutants was carried out, with the exception of Ile422Thr (corresponding to Mas1 - Ile398Thr), the introduction of which did not yield viable yeast strains. Homologous mutations led to a temperature-sensitive phenotype with accumulation of immature/unprocessed precursor proteins and decrease of mature/processed forms both in vivo or in organello (following isolation of mitochondria). Under conditions of heat stress, Mas1 mutations decreased biogenesis of Fe-S clusters. - Respiratory chain complexes I-III contain Fe-S clusters. In muscle biopsy from an affected individual, complex II activity was significantly reduced (although this was not the case in fibroblasts or liver biopsy). Dysfunction of mitochondrial and cytosolic Fe-S cluster-dependent enzymes (eg. aconitase) was also shown in muscle tissue. Regression/stagnation with seizures/non-achievement of milestones may justify testing for an ID / epilepsy gene panel. In addition, metabolic studies or mitochondrial respiratory chain complex studies were sometimes non-informative (lactate elevated in 3/5 subjects) or not carried out at all / in relevant tissues (muscle biopsy in 2 individuals, fibroblasts/liver biopsy did not demonstrate reduced complex activity when tested). PMPCB is included in the ID gene panel of Radboudumc, as well as the SysID database. The gene is included in the DD panel of G2P associated with "Neurodegeneration in Early Childhood" (disease confidence : probable). As a result, PMPCB can be considered for inclusion in both epilepsy and ID panels as green (or amber). Sources: Literature, Radboud University Medical Center, Nijmegen |
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| Intellectual disability v2.1046 | PMPCB |
Konstantinos Varvagiannis gene: PMPCB was added gene: PMPCB was added to Intellectual disability. Sources: Literature,Radboud University Medical Center, Nijmegen Mode of inheritance for gene: PMPCB was set to BIALLELIC, autosomal or pseudoautosomal Phenotypes for gene: PMPCB were set to Multiple mitochondrial dysfunctions syndrome 6, 617954 Penetrance for gene: PMPCB were set to Complete Review for gene: PMPCB was set to GREEN gene: PMPCB was marked as current diagnostic Added comment: Biallelic pathogenic PMPCB variants cause, Multiple mitochondrial dysfunctions syndrome 6 (MIM 617954). 5 relevant individuals from 4 unrelated families (in one case consanguineous) have been reported by Vögtle et al. (2018 - PMID: 29576218). Onset of symptoms (eg. hypotonia) often preceded a period of developmental regression/stagnation which was common in all individuals and occurred within the first 2 years of life, usually following febrile illness. In all cases neurological features were severe (lack of ambulation/speech). Seizures were observed in 4 individuals from 3 families, with onset at the age of 11-24m. MRI images demonstrated T2 signal hyperintensities of the basal ganglia with cerebellar and cerebral atrophy in some. Deterioration with early death was reported on three occasions, though some years after symptom onset. Following exclusion of other diagnoses in some cases (eg. aCGH, epilepsy panel), WES identified biallelic PMPCB missense variants, supported by Sanger confirmation and segregation studies. The following variants were reported (NM_004279.2): - c.523C>T (p.Arg175Cys) in trans with c.601G>C (p.Ala201Pro) [Fam A and B] - c.524G>A (p.Arg175His) in trans with c.530T>G (p.Val177Gly) [Fam C] - c.1265T>C (p.Ile422Thr) in homozygous state [Fam D with 2 affected sibs] The gene encodes the catalytic (beta) subunit of the mitochondrial processing protease (MPP) which is responsible for the cleavage/maturation of nuclear-encoded mitochondrial precursor proteins after their import in mitochondria. The alpha subunit is encoded by PMPCA (green rating proposed for this panel). Extensive studies demonstrated (perhaps a better summary provided by OMIM): - Reduced PMPCB protein levels in mitochondria isolated from patient fibroblasts or patient-derived pluripotent stem cells. - Frataxin maturation was impaired with accumulation of the intermediate form and lower amounts of mature FXN, indicating decrease in MPP activity. - Analysis of the homologous Mas1 S. cerevisiae mutants was carried out, with the exception of Ile422Thr (corresponding to Mas1 - Ile398Thr), the introduction of which did not yield viable yiest strains. Homologous mutations led to a temperature-sensitive phenotype with accumulation of immature/unprocessed precursor proteins and decrease of mature/processed forms both in vivo or in organello (following isolation of mitochondria). Under conditions of heat stress, Mas1 mutations decreased biogenesis of Fe-S clusters. - Respiratory chain complexes I-III contain Fe-S clusters. In muscle biopsy from an affected individual, complex II activity was significantly reduced (although this was not the case in fibroblasts or liver biopsy). Dysfunction of mitochondrial and cytosolic Fe-S cluster-dependent enzymes (eg. aconitase) was also shown in muscle tissue. Regression/stagnation with seizures/non-achievement of milestones may justify testing for an ID / epilepsy gene panel. In addition, metabolic studies or mitochondrial respiratory chain complex studies were sometimes non-informative (lactate elevated in 3/5 subjects) or not carried out at all / in relevant tissues (muscle biopsy in 2 individuals, fibroblasts/liver biopsy did not demonstrate reduced complex activity when tested). PMPCB is included in the ID gene panel of Radboudumc, as well as the SysID database. The gene is included in the DD panel of G2P associated with "Neurodegeneration in Early Childhood" (disease confidence : probable). As a result, PMPCB can be considered for inclusion in both epilepsy and ID panels as green (or amber). Sources: Literature, Radboud University Medical Center, Nijmegen |
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| Intellectual disability v2.1046 | PMPCA |
Konstantinos Varvagiannis gene: PMPCA was added gene: PMPCA was added to Intellectual disability. Sources: Literature,Radboud University Medical Center, Nijmegen Mode of inheritance for gene: PMPCA was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: PMPCA were set to 25808372; 26657514; 27148589; 30617178 Phenotypes for gene: PMPCA were set to Spinocerebellar ataxia, autosomal recessive 2 (MIM 213200) Penetrance for gene: PMPCA were set to Complete Review for gene: PMPCA was set to GREEN gene: PMPCA was marked as current diagnostic Added comment: Biallelic pathogenic PMPCA variants cause Spinocerebellar ataxia, autosomal recessive 2 (SCAR2 - MIM 213200). More than 20 individuals from several unrelated families have been reported. At least 6 different pathogenic variants have been identified. Loss of PMPCA function is the suggested mechanism. ID is a feature of the disorder. PMPCA encodes the α-subunit of mitochondrial processing peptidase (αMPP), a heterodimeric enzyme responsible for the cleavage of nuclear-encoded mitochondrial precursor proteins after import in the mitochondria (summary by Jobling et al and OMIM). Arguments for involvement of the gene include the highly similar phenotype, segregation studies, expression of the gene in fetal and relevant adult tissues (in brain/cerebellum/cerebellar vermis), lower protein levels demonstrated for some variants, abnormal processing of frataxin (in line with the role of αMPP) demonstrated in most cases, rescue of the maturation defect upon transduction of wt PMPCA cDNA, disruption of REDOX balance in patient cells, etc. Relevant studies are summarized below. PMPCA is included in gene panels for ID offered by several diagnostic laboratories (incl. Radboud UMC, GeneDx, etc) and listed as a confirmed ID gene in SysID. It is not associated with any phenotype in G2P. As a result, this gene can be considered for inclusion in the current panel probably as green (or amber). ---- [1] - Jobling et al. (2015 - PMID: 25808372) described the phenotype of 17 individuals from 4 families, all presenting with non-progressive cerebellar ataxia and the majority with ID of variable severity (15/17 - relevant to the current panel). Individuals from 3 of the families - all of Lebanese origin - were homozygous for NM_015160.3:c.1129G>A (p.Ala377Thr). A further similarly affected subject was compound heterozygous for c.287C>T (p.Ser96Leu) and c.1543G>A (p.Gly515Arg). The homozygous variant in the first family was found within a 2.85 Mb linkage region on chr 9q34. An additional variant within this region (in CAMSAP1) was discarded following results in other families of the same origin. Semi-quantitative RT-PCR demonstrated fetal expression of the PMPCA as well as relatively higher expression in adult brain, cerebellum and cerebellar vermis. As for Ala377Thr, protein levels were shown to be lowest in affected individuals (LCLs, fibroblasts) and low - though somewhat higher - in carrier parents (LCL) compared to controls. RT-PCR on total RNA from LCLs did not show evidence of abnormal transcripts/additional splicing defect. Localization of mutant protein and morphology of mitochondrial reticulum was similar to controls. Maturation of frataxin - the protein depleted in Friedreich ataxia - was shown to be abnormal in patient lymphoblasts, compatible with the role of αMPP. In line with abnormal mitochondrial function, REDOX balance was increased in patient cells. [2] - Choquet et al. (2016 - PMID: 26657514) reported on 2 sibs - born to distantly related parents. The authors noted a phenotype corresponding to SCAR2 although the presentation was somewhat milder, intellectual disability was not a feature (despite some learning difficulties in one) and ataxia was progressive. WES demonstrated homozygosity for NM_015160:c.766G>A (p.Val256Met). Western blot in patient lymphoblasts showed αMPP levels similar to carriers and controls. Abnormal maturation (accumulation of specific isoforms) was shown for frataxin. [3] - Joshi et al. (2016 - PMID: 27148589) described the phenotype of 2 cousins belonging to a large Lebanese pedigree. Presentation in both was compatible with multisystem involvement incl. profound global DD, severe hypotonia, weakness, respiratory insufficiency, blindness suggestive of mitochondrial disorder. mtDNA, analyses of mitochondrial focused nuclear gene panel and aCGH were non-diagnostic. Both subjects were compound heterozygous for NM_015160.3:c.1066G>A (p.Gly356Ser) and c.1129G>A (p.Ala377Thr) following WES, with compatible segregation studies within the family. Western blot revealed PMPCA levels similar to control. Reduction of PMPCA staining and abnormally enlarged mitochondria were observed upon immunofluorescence in patient fibroblasts. Frataxin processing was abnormal. Lentiviral transduction of patient fibroblasts with wt PMPCA cDNA, led to increased PMPCA levels and correction of frataxin processing. [4] - Rubegni et al. (2019 - PMID: 30617178) report on a 7-y.o. boy with global DD, spastic-ataxic gait and 'low IQ'. MRI images were suggestive of cerebellar atrophy with hyperintensity in the striatum. The child was homozygous for c.553C>T / p.Arg185Trp (reference not specified, although the variant would be compatible with NM_015160.3). Sources: Literature, Radboud University Medical Center, Nijmegen |
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| Intellectual disability v2.1021 | MED25 |
Konstantinos Varvagiannis changed review comment from: Please consider the 2 additional articles by Nair et al. (2019 - DOI: 10.1159/000494465 - PMID: 30800049 & DOI: 10.1159/000501114 - PMID: NA) reporting on 3 individuals from 2 consanguineous Lebanese families. All affected individuals were homozygous for a MED25 missense variant [NM_030973.3:c.518T>C / p.Ile173Thr], possibly a founder mutation in the Lebanese population. The phenotype presented some similarities with the previously described patients. The variant has a very low AF in gnomAD (0.00003470) and was also absent from the Saudi Variant Database. In silico predictions from PolyPhen2, PROVEAN, MutationTaster were suggestive of a probably damaging effect. The individual from the first report (PMID: 30800049) had an additional homozygous COQ8A variant, with some features fitting with the phenotype of AR primary CoQ10 deficiency type 4 and others negating this diagnosis. MED25 is included in gene panels for ID offered by several diagnostic laboratories (incl. Radboudumc, Victorian Clinical Genetics and many others). It is not however included in the DD panel of G2P.; to: Please consider the 2 additional articles by Nair et al. (2019 - DOI: 10.1159/000494465 - PMID: 30800049 & DOI: 10.1159/000501114 - PMID: NA) reporting on 3 individuals from 2 consanguineous Lebanese families. All affected individuals were homozygous for a MED25 missense variant [NM_030973.3:c.518T>C / p.Ile173Thr], possibly a founder mutation in the Lebanese population. The phenotype presented some similarities with the previously described patients. The variant has a very low AF in gnomAD (0.00003470) and was also absent from the Saudi Variant Database. In silico predictions from PolyPhen2, PROVEAN, MutationTaster were suggestive of a probably damaging effect. The individual from the first report (PMID: 30800049) had an additional homozygous COQ8A variant, with some features fitting with the phenotype of AR primary CoQ10 deficiency type 4 and others negating this (possibly concurrent) diagnosis. MED25 is included in gene panels for ID offered by several diagnostic laboratories (incl. Radboudumc, Victorian Clinical Genetics and many others). It is not however included in the DD panel of G2P. |
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| Intellectual disability v2.953 | DEGS1 |
Konstantinos Varvagiannis gene: DEGS1 was added gene: DEGS1 was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: DEGS1 was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: DEGS1 were set to 30620337; 30620338; 31186544 Phenotypes for gene: DEGS1 were set to Leukodystrophy hypomyelinating 18, MIM 618404) Penetrance for gene: DEGS1 were set to Complete Review for gene: DEGS1 was set to GREEN Added comment: Several individuals with biallelic pathogenic DEGS1 variants have been reported to date, in the following studies : [1] Pant et al. 2019 (PMID: 30620337) : 19 patients from 13 unrelated families [2] Karsai et al. 2019 (PMID: 30620338) : 1 individual [3] Dolgin et al. 2019 (PMID: 31186544) : 4 individuals belonging to a large consanguineous kindred As summarized in the first article and OMIM, affected individuals may have very poor psychomotor development, dystonia, spasticity, seizures with hypomyelinating leukodystrophy upon brain imaging and/or progressive atrophy of corpus callosum, thalami and cerebellum. Although a severe form overall was reported for many individuals in the first study, variable severity (eg. mild to severe ID) was reported among individuals belonging to the same kindred in the report by Dolgin et al. DEGS1 encodes Δ4-dehydroceramide desaturase which catalyzes conversion of dihydroceramide (DhCer) to ceramide (Cer) in the de novo ceramide biosynthetic pathway. Ceramide is the central unit of all sphingolipids, which are components of cellular membranes and play key roles in several processes incl. cell differentiation, neuronal signaling and myelin sheath formation. Sphingolipid balance is important for the CNS as demonstrated in the case of lysosomal disorders (eg. Gaucher, Niemann Pick, Farber) one enzymatic step away from DEGS1. Variants of all types (missense, stopgain, frameshift) have been reported with the majority/almost all located in the fatty acid desaturase (FAD) domain. Extensive studies have been carried out and demonstrated: - impaired DEGS1 activity in patients' fibroblasts and muscle suggested by increased DhCer/Cer ratio and compatible broader biochemical effects (higher levels of dihydrosphingosine, dihydrosphingomyelins, etc. and lower levels of sphingosine, monohexosylceramides, etc). - increased ROS production in patient fibroblasts (similar to a Drosophila model of excess DhCer), - high expression of the gene in child and adult CNS tissues from control individuals (evaluated by RT-qPCR in Ref. 1). A previous study has suggested that DEGS1 expression is upregulated during the 4-9th week of human embryogenesis (PMID cited: 20430792) which may suggest an important role for neural system development. - decreased expression for some variants either evaluated at the mRNA (RT-qPCR) / protein level (by Western Blot) - In zebrafish loss of Degs1 resulted in increased DhCer/Cer ratio, locomotor disability and impaired myelination similar to the patients' phenotype. Fingolimod, a sphingosine analog inhibiting Cer synthase (one step prior to DEGS1 in the de novo ceramide biosynthesis pathway, and converting sphingosine to ceramide in the salvage pathway) reduced the DhCer/Cer imbalance, ameliorated the locomotor phenotype and increased the number of myelinating oligodendrocytes in zebrafish, while it reduced the ROS levels in patient fibroblasts. Previous animal models: Apart from the zebrafish model (Pant et al.), higher DhCer/Cer ratios have been shown in homozygous Degs1 -/- mice similar to what is also observed in D. melanogaster. As summarized in MGI (and the previous studies as well) "mice homozygous for a knock-out allele exhibit premature death, decreased to absent ceramide levels, decreased body weight, scaly skin, sparse hair, tremors, hematological and blood chemistry abnormalities, decreased bone mineral content and density and decreased liver function." (PMIDs cited: 17339025, 28507162). ---- The respective OMIM entry is Leukodystrophy, hypomyelinating, 18 (#618404). DEGS1 is not associated with any phenotype in G2P. ---- As a result, DEGS1 can be considered for inclusion in the ID and epilepsy panels probably as green (relevant phenotype, sufficient number of individuals, supportive expression and biochemical studies, animal models, etc). Sources: Literature |
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| Intellectual disability v2.597 | PLEKHG2 |
Konstantinos Varvagiannis gene: PLEKHG2 was added gene: PLEKHG2 was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: PLEKHG2 was set to MONOALLELIC, autosomal or pseudoautosomal, imprinted status unknown Publications for gene: PLEKHG2 were set to 26539891; 26573021; 24001768 Phenotypes for gene: PLEKHG2 were set to Leukodystrophy and acquired microcephaly with or without dystonia, 616763 Penetrance for gene: PLEKHG2 were set to unknown Review for gene: PLEKHG2 was set to AMBER gene: PLEKHG2 was marked as current diagnostic Added comment: Karaca et al. (2015 - PMID: 26539891) in a study of 128 - mostly consanguineous - families with neurogenetic disorders and brain malformations, identified an individual homozygous for a PLEKHG2 missense variant (NM_022835.2:c.1708G>A or p.Gly570Arg). This individual (BAB4830) had a similarly affected sib. Features included hypotonia, intellectual disability, microcephaly, cerebellar atrophy and nystagmus (description provided in supplement - Table S1). This variant has been submitted in ClinVar as likely pathogenic by the corresponding laboratory (SCV000537940.1). ------- Edvardson et al. (2016 - PMID: 26573021) reported on 5 individuals from 2 unrelated consanguineous Palestinian families, harboring a missense variant in the homozygous state (NM_022835.2:c.610C>T or p.Arg204Trp - 1/5 was unavailable for testing). Unaffected relatives here either heterozygous for this variant or homozygous for the reference allele. Common features included hypotonia (5/5), DD/ID (5/5), postnatal microcephaly (5/5), dystonia (3/5), nystagmus (2/5) or seizures (1/5) [many of these similar to those reported by Karaca et al]. Brain MRI images were consistent with leukodystrophy and prolonged relaxation of dorsal tegmental tracts (similar findings were not commented by Karaca et al). PLEKHG2 encodes a Rho guanine exchange factor (RhoGEF). RhoGEFs activate RhoGTPases through release of GDP and binding of GTP. Mutations in other RhoGEFs have been associated with neurodevelopmental disorders. PLEKHG2 activity was shown to be significantly decreased in HEK293A cells transfected with R204W-PLEKHG2 when compared to tranfection with wt. Western blotting suggested that this was not the result of defective expression. Using lymphoblastoid cell lines from peripheral B lymphocytes from individuals homozygous for R204W and controls, similar levels of expression were shown between the 2 groups. As the authors note, PLEKHG2 is required for Rac- and Cdc42-stimulated actin polymerization in leukocytes (PMID cited: 24001768). SDF1a-stimulated actin polymerization was studied in patient cells and was shown to be significantly impaired. In line with this actin polymerization was also impaired upon siRNA-mediated downregulation of PLEKHG2 expression in control cells. ------- A subsequent submission of the Gly570Arg variant in ClinVar (2017 - SCV000609979.1 - same variant as the one reported by Karaca et al) reports this as a VUS. ------- PLEKHG2 is associated with Leukodystrophy and acquired microcephaly with or without dystonia (616763) in OMIM. This gene is not associated with any phenotype in G2P. PLEKHG2 is included in gene panels for ID offered by some diagnostic laboratories. ------- As a result, this gene could be considered for inclusion in this panel probably as amber (or green if the current evidence is considered to be sufficient). Sources: Literature |
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| Intellectual disability v2.595 | STAG2 |
Konstantinos Varvagiannis gene: STAG2 was added gene: STAG2 was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: STAG2 was set to X-LINKED: hemizygous mutation in males, monoallelic mutations in females may cause disease (may be less severe, later onset than males) Publications for gene: STAG2 were set to 29263825; 28296084; 30158690; 30447054; 19449417; 26443594; 25677961; 23637084; 25450604 Phenotypes for gene: STAG2 were set to Global developmental delay; Intellectual disability; Abnormality of head or neck; Microcephaly; Growth delay; Hearing impairment; Abnormal heart morphology Penetrance for gene: STAG2 were set to unknown Review for gene: STAG2 was set to GREEN gene: STAG2 was marked as current diagnostic Added comment: Several affected individuals (from at least 8 unrelated) families have been reported in the literature. The phenotype consists - among others - of DD/ID. STAG2 is located on long arm of chromosome X (Xq25). Based on these reports, both males and females can be affected. Soardi et al. (2017 - PMID: 29263825) report an affected male belonging to a large pedigree with 4 other similarly affected males. The disorder in this pedigree followed a typical X-linked inheritance pattern. All affected males were hemizygous for a missense variant (NM_001042749.1:c.980G>A or p.Ser327Asn). Common phenotype consisted of moderate ID, short stature, sensory hearing loss and some similar facial features. Unaffected males did not harbor the variant. Heterozygous females were not affected. Co-segragation of the variant with the affected status under an X-linked model, appeared unlikely to have occurred by chance (probability of 1/131,072 - logarithm of odds score of 5.12). Mullegama et al. (2017 - PMID: 28296084) report on an 8-year-old girl harboring a de novo nonsense variant in STAG2 (NM_001042749.1:c.205C>T or p.Arg69Ter). This individual presented - among others with - DD, microcephaly, growth delay, digit anomalies, particular facial features, and anomalies of other systems (eg. hearing loss, cardiac defect, etc). The authors summarize the features of 2 subjects from the DDD study as available in DECIPHER, without additional details. [Variants of these individuals NM_001042749.1:c.1913_1922del10 or p.(A638Vfs*10) / NM_001042749.1:c.1811G>A p.(R604Q)]. Yuan et al. (2018 - PMID: 30158690) report on 4 females with de novo LoF STAG2 variants as well as 1 male subject with a de novo missense one. DD (5/5) and ID (4/4) were features in all individuals for whom this information was available. One additional female had an intragenic STAG2 deletion, although this subject was not reported to have DD or ID (table S6 : microcephaly, seizures and facial phenotype). It is not known whether the deletion was inherited or had occurred as a de novo event. All variants from this study have been submitted in ClinVar (phenotype : STAG2-related disorder). Mullegama et al. (2018 - PMID: 30447054) report on a 4-year-old male with DD, microcephaly, growth delay, digit anomalies due to a de novo missense STAG2 variant (c.3027A>T or p.Lys1009Asn). As discussed by the authors at the time of the study 33 males with Xq25 duplications and ID had been reported (PMIDs cited: 19449417, 26443594, 25677961, 23637084, 25450604). Discussed in these articles : STAG2 (or STAG1) is one of the 4 core proteins of the cohesin complex, the other 3 being SMC1A, SMC3 and RAD21. Mutations in genes encoding these proteins or their interactors (eg. NIBPL, HDAC8, ESCO2, etc) have been associated cohesinopathies, a group of multisystem developmental disorders (eg. Cornelia de Lange syndrome, Roberts/SC phocomelia, etc). It has been commented that the phenotype of STAG2-related disorder presents overlap with other cohesinopathies (eg. DD, microcephaly and growth retardation, craniofacial features, anomalies of the digits, etc). Decreased proportion of nuclei with premature sister chromatid separation compared to controls was found on one occasion (suggestive of tighter sister chromatid cohesion) [Mullegama-A]. Sister chromatid cohesion was not affected in another report [Soardi et al.]. Western blot demonstrated significant reduction of STAG2 levels for a nonsense variant [Mullegama-A]. Levels were not perturbed for a missense variant [Soardi et al.]. Upon immunofluorescence STAG2 presented normal (nuclear) localization for a missense variant for which this was studied [Soardi et al.]. Perturbation of the cell cycle profile (higher percentage of G2/M cells) was demonstrated for patient fibroblasts compared to controls on one occasion where this was studied. [Soardi et al.]. Microarray expression studies in patient fibroblasts demonstrated altered transcription (upregulation) of genes implicated in cell division, mitosis and DNA replication upon comparison with normal fibroblasts [Soardi et al.]. The effect of a missense variant on STAG2 binding to other cohesin subunits (SCC1, SMC1 and SMC3) and regulators was studied. Binding was found to be reduced in vivo (in HeLa cells) for SCC1 (its direct binding partner) as well as SMC1, SMC3 (possibly indirectly). Reduced STAG2 binding to cohesin regulators was also shown in vivo. However, in vitro studies were not suggestive of impaired binding of STAG2 to SCC1 (a finding difficult to explain) [Soardi et al.]. STAG2 appears to be intolerant to LoF variants (pLI of 1 in ExAC). Z-Score for missense variants is 5.11. Mullegama et al. (B) comment that Xq25 duplications in males may be associated with milder phenotypes compared to intragenic variants. They further hypothesize that males are able to survive less damaging variants while females are able to survive more deleterious (eg. LoF) ones though with more severe phenotypes (similarity to the MECP2 model is discussed). ---------- STAG2 is not associated with any phenotype in OMIM. In G2P this gene is associated with STAG2-related developmental delay with microcephaly and congenital anomalies (disease confidence : confirmed / Both DD and ID among the phenotypes assigned to this entry). ---------- STAG2 is included in gene panels for ID offered by some diagnostic laboratories. ---------- As a result, this gene can be considered for inclusion in the ID panel as green (or amber). Sources: Literature |
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| Intellectual disability v2.588 | MAPK8IP3 |
Konstantinos Varvagiannis gene: MAPK8IP3 was added gene: MAPK8IP3 was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: MAPK8IP3 was set to MONOALLELIC, autosomal or pseudoautosomal, imprinted status unknown Phenotypes for gene: MAPK8IP3 were set to 25363768; 28213671; 28135719 Penetrance for gene: MAPK8IP3 were set to unknown Review for gene: MAPK8IP3 was set to GREEN Added comment: Platzer et al. (doi.org/10.1016/j.ajhg.2018.12.008) report on 13 unrelated individuals with de novo pathogenic variants in MAPK8IP3. The phenotype consisted - among others - of DD with ID (13/13) as well as variable brain anomalies (incl. cerebral or cerebellar atrophy, corpus callosum anomalies, perisylvian polymicrogyria, etc). Microcephaly, seizures, ataxia, ASD were features seen in fewer individuals. The variants reported included 2 nonsense, 1 frameshift as well as 6 missense mutations (3 missense variants were found - each - in 2 or more individuals). All three LoF variants were located in the first exon. (mRNA levels were not studied for these variants although NMD is presumed). The brain anomalies were more consistent for missense variants. MAPK8IP3 appears intolerant to LoF variants (pLI of 1) with constraint also for missense variants (Z-score of 4.06). In silico structural modeling was possible for 4 missense variants based on available crystal structures and different mechanisms were presumed (disruption of contacts between Leu444 of adjacent subunits, altered interaction between proximal residues at positions 461 and 466, or disruption of protein protein interactions). The C.elegans MAPK8IP3 ortholog is encoded by the unc-16 gene. Impaired clearance and accumulation of organelles (incl. lysosomes) in axons is observed in unc-16 mutants (recessive phenotype). For 6 variants, also conserved in C.elegans, mutants were engineered using CRISPR genome editing. The observed mutant phenotypes (increased axonal lysosomal density compared to controls for 2 variants, sluggish locomotion with lower swimming cycle rate for 1 nonsense and 4 missense variants) were rescued upon CRISPR reverse engineering of each mutant allele back to its wild-type sequence. The authors cite 3 previous studies, in which individuals investigated for neurodevelopmental disorders where found to harbor de novo MAPK8IP3 variants, namely: - PMID 25363768 (Iossifov et al.) : p.Tyr94Cys [ASD without ID] - PMID 28213671 (Berger et al.) : p.Glu461Gly [Smith-Magenis-like phenotype) - PMID 28135719 (DDD study) p.Arg1146Cys [This variant was found in 3 individuals in the study by Platzer et al.] ------------ A few additional individuals with neurodevelopmental disorders appear in the denovo-db after filtering for coding variants: http://denovo-db.gs.washington.edu/denovo-db/QueryVariantServlet?searchBy=Gene&target=MAPK8IP3 ------------ NM_015133.4:c.111C>G (p.Tyr37Ter) has been submitted in ClinVar by the Undiagnosed Diseases Network (NIH) as likely pathogenic, associated with MAPK8IP3-related disorder (hypotonia, DD, EEG anomalies among the phenotypes). It is not clear whether this subject corresponds to individual #3 reported by the previous study (possibly not the case). ------------ MAPK8IP3 is not associated with any phenotype in OMIM, nor in G2P. This gene is not commonly included in gene panels for ID. ------------ As a result, MAPK8IP3 can be considered for inclusion in this panel as green (rather than amber). Sources: Literature |
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| Intellectual disability v2.588 | TSEN15 |
Konstantinos Varvagiannis gene: TSEN15 was added gene: TSEN15 was added to Intellectual disability. Sources: Literature,Radboud University Medical Center, Nijmegen Mode of inheritance for gene: TSEN15 was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: TSEN15 were set to 27392077; 25558065 Phenotypes for gene: TSEN15 were set to Pontocerebellar hypoplasia, type 2F (MIM 617026) Penetrance for gene: TSEN15 were set to Complete Review for gene: TSEN15 was set to GREEN gene: TSEN15 was marked as current diagnostic Added comment: Biallelic pathogenic variants in TSEN15 cause Pontocerebellar hypoplasia, type 2F (MIM 617026). Four individuals with molecular confirmation of the diagnosis, from 3 unrelated consanguineous families have been reported by Breuss et al. (PMID: 27392077). One of these individuals was previously included in a study of neurogenetic disorders in consanguineous families (Alazami et al. - PMID: 25558065). A similarly affected sib (possibly not tested) was reported for one patient. DD with variable degrees of ID (mild to severe), progressive microcephaly were common to all. Seizures were noted in 2 individuals. MRI images (for the feature of pontocerebellar hypoplasia - PCH) were only available for 2 families. Affected subjects were homozygous for missense variants private to each family, namely: - NM_052965.3:c.226T>G (p.Trp76Gly) - NM_052965.3:c.346C>T (p.His116Tyr) - NM_052965.3:c.455A>G (p.Tyr152Cys) Trp76Gly and Tyr152Cys resulted in reduced protein abundance while His116Tyr did not have an effect on TSEN15 expression levels. TSEN15 is part of the tRNA splicing endonuclease complex, the 3 other components of which (TSEN2, TSEN34, TSEN54) have already been associated with PCH. The complex interacts with an RNA kinase encoded by CLP1. All 3 variants resulted in altered stoichiometry (/relative abundance) of the 3 other subunits of the complex as well as the relative levels of CLP1. Almost complete loss of in vitro tRNA cleavage activity was the case for purified complexes from all 3 mutants. ------ TSEN15 is included in the DD panel of G2P associated with Pontocerebellar Hypoplasia and Progressive Microcephaly (Disease confidence: probable). ID is among the assigned phenotypes. This gene is included in gene panels for ID offered by diagnostic laboratories (incl. Radboudumc). ------ As a result, TSEN15 could be considered for inclusion in this panel as green (or amber). Sources: Literature, Radboud University Medical Center, Nijmegen |
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| Intellectual disability v2.579 | RPIA |
Konstantinos Varvagiannis gene: RPIA was added gene: RPIA was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: RPIA was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: RPIA were set to 14988808; 20499043; 28801340; 30088433 Phenotypes for gene: RPIA were set to Ribose 5-phosphate isomerase deficiency, MIM 608611. Penetrance for gene: RPIA were set to unknown Review for gene: RPIA was set to GREEN gene: RPIA was marked as current diagnostic Added comment: Biallelic pathogenic variants in RPIA cause Ribose 5-phosphate isomerase deficiency, MIM 608611. PMID: 14988808 is the first report on the disorder with molecular (incl. genetic) confirmation of the diagnosis. A patient initially investigated for early developmental delay, leukoencephalopathy, seizures with onset at 4 years, with subsequent neurologic regression and peripheral neuropathy at the age of 7, was suspected to have a disorder of the pentose phosphate pathway on the basis of highly elevated polyols on brain MRS and body fluid analysis. Reduced ribose 5-phosphate isomerase activity was shown in fibroblasts. Genetic testing demonstrated the presence of a missense (NM_144563.2:c.404C>T / NP_653164.2:p.Ala135Val - previously referred to as A61V) as well as a frameshift variant (NM_144563.2:c.762delG / NP_653164.2:p.Asn255Ilefs). Additional extensive supportive functional studies were published a few years later (PMID: 20499043). [This patient was initially described in PMID: 10589548]. PMID: 28801340 is a report on a second patient. This individual presented with delayed early development (independent walking and speech achieved at 2 and 5 years respectively), seizures and regression at the age of 7 with MRI white matter abnormalities. Review of magnetic resonance spectroscopy (MRS) was suggestive of elevated polyols (arabitol and ribitol). In line with this, genetic testing revealed a homozygous missense variant in RPIA (NM_144563.2:c.592T>C or p.Phe198Leu). Urine analysis confirmed elevated excretion of polyols, thus confirming the diagnosis. PMID: 30088433 reports on a boy with neonatal onset leukoencephalopathy and developmental delay having undergone early metabolic testing and aCGH (the latter at the age of 16 months). Persistance of his delay motivated exome sequencing at the age of approx. 4.5 years which demonstrated 2 RPIA variants (NM_144563.2:c.253G>A or p.Ala85Thr and NM_144563.2:c.347-1G>A). Measurement of ribitol and arabitol in urine demonstrated significant elevations (>20x) consistent with this diagnosis. RPIA is included in gene panels for intellectual disability offered by various diagnostic laboratories. As a result this gene can be considered for inclusion in this panel as green (or amber). Sources: Literature |
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| Intellectual disability v2.550 | UFM1 |
Konstantinos Varvagiannis gene: UFM1 was added gene: UFM1 was added to Intellectual disability. Sources: Literature,Expert Review Mode of inheritance for gene: UFM1 was set to BOTH monoallelic and biallelic, autosomal or pseudoautosomal Publications for gene: UFM1 were set to 28931644; 29868776 Phenotypes for gene: UFM1 were set to Leukodystrophy hypomyelinating 14, 617899 Penetrance for gene: UFM1 were set to Complete Review for gene: UFM1 was set to GREEN Added comment: Biallelic UFM1 mutations cause Leukodystrophy hypomyelinating 14, MIM 617899. PMID: 28931644 is the first report on 16 individuals from 14 families with shared Roma ethnic background. All subjects were found to harbor a UFM1 promoter 3 basepair deletion in the homozygous state. All patients demonstrated a severe phenotype including lack of development and severe epileptic encephalopathy while their MRI images demonstrated hypomyelination with atrophy of the basal ganglia and the cerebellum. The promoter deletion was detected by exome sequencing. Previously a 0.8 Mb homozygous region was identified to be shared by all the patients in whom a SNP array was performed. Alternative causes, notably TUBB4A mutations and deletions/duplications were excluded. 3 individuals had Sanger sequencing of all coding regions within the homozygous interval to rule out other - eventually missed - variants. PMID: 29868776 reports 4 additional individuals from 2 consanguineous families (one from Ethiopia, for the other this was not specified). All 4 patients were homozygous for the c.241C>T (NM_016617.3) or p.(Arg81Cys) variant which was shown to be hypomorphic upon functional studies. The phenotype consisted of developmental delay (4/4 or 20/20 including the patients from the previous report with which comparison is made in table 2 of the article) with microcephaly (4/4 or 20/20) and seizures (4/4 or 16/20) as well as MRI abnormalities. Failure to thrive and/or short stature were also among the most common features. UFM1 (as well as UFC1 also discussed in the same article) participate in ufmylation, with mutations in other enzymes of the same process (notably UBA5 - gene rated Green in the ID and epilepsy panels) having already been described in neurodevelopmental disorders. As a result, this gene can be considered for inclusion in this panel as green (or amber). Sources: Literature, Expert Review |
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| Intellectual disability v2.535 | ATP1A1 |
Konstantinos Varvagiannis gene: ATP1A1 was added gene: ATP1A1 was added to Intellectual disability. Sources: Expert Review,Literature Mode of inheritance for gene: ATP1A1 was set to MONOALLELIC, autosomal or pseudoautosomal, imprinted status unknown Publications for gene: ATP1A1 were set to 30388404 Phenotypes for gene: ATP1A1 were set to Hypomagnesemia; Seizures; Intellectual disability Penetrance for gene: ATP1A1 were set to unknown Review for gene: ATP1A1 was set to GREEN Added comment: PMID: 30388404 reports on 3 subjects from 3 families with de novo pathogenic variants in ATP1A1. All 3 presented with similar phenotype consisting of hypomagnesemia, early onset refractory seizures as well as intellectual disability. Alternative causes of hypomagnesemia with seizures (eg. due to TRPM6 mutations) were excluded while the phenotype of the 3 patients differed from similar disorder in that hypomagnesemia as well as seizures were not responsive to magnesium supplementation. Three different missense variants are reported (L302R, G303R, M859R) all as de novo occurences and after confirmation of paternity. Functional studies were suggestive of loss of the ATPase function, abnormal cation permeabilities as well as reduced level of expression (the latter was significant for at least for 2 of the 3 variants). Mutations in ATP1A1 have also been reported in patients with Charcot-Marie-Tooth type 2 (CMT2DD - MIM: 618036) although the variants reported to date map seem to cluster within the helical linker region (residues 592 to 608). The young age of the patients with epilepsy and intellectual disability did not allow conclusions on eventual peripheral neuropathy in these individuals. As a result this gene can be considered for inclusion in this panel as green (or amber). Sources: Expert Review, Literature |
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| Intellectual disability v2.468 | MAGT1 | Louise Daugherty Source Victorian Clinical Genetics Services was added to MAGT1. | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability v2.468 | MAGEL2 | Louise Daugherty Source Victorian Clinical Genetics Services was added to MAGEL2. | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability v2.401 | ISCA-37404-Gain | Louise Daugherty Phenotypes for Region: ISCA-37404-Gain were changed from chromosome 15q11-q13 duplication syndrome; include autism, mental retardation, ataxia, seizures, developmental delays, and behavioral problems; 608636; elayed development and intellectual disability associated with abnormal behavior and dysmorphic facial features. Additional variable features may include thin corpus callosum on brain imaging and sleep disturbances. Carrier females may be mildly affected to chromosome 15q11-q13 duplication syndrome; include autism, mental retardation, ataxia, seizures, developmental delays, and behavioral problems; 608636; delayed development and intellectual disability associated with abnormal behavior and dysmorphic facial features. Additional variable features may include thin corpus callosum on brain imaging and sleep disturbances. Carrier females may be mildly affected | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability v2.398 | ISCA-37404-Gain |
Louise Daugherty Region: ISCA-37404-Gain was added Region: ISCA-37404-Gain was added to Intellectual disability. Sources: ClinGen,Expert Review Green Mode of inheritance for Region: ISCA-37404-Gain was set to MONOALLELIC, autosomal or pseudoautosomal, imprinted status unknown Publications for Region: ISCA-37404-Gain were set to 18374305; 16840569; 9106540 Phenotypes for Region: ISCA-37404-Gain were set to chromosome 15q11-q13 duplication syndrome; include autism, mental retardation, ataxia, seizures, developmental delays, and behavioral problems; 608636; elayed development and intellectual disability associated with abnormal behavior and dysmorphic facial features. Additional variable features may include thin corpus callosum on brain imaging and sleep disturbances. Carrier females may be mildly affected |
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| Intellectual disability v2.398 | ISCA-37418-Loss |
Louise Daugherty Region: ISCA-37418-Loss was added Region: ISCA-37418-Loss was added to Intellectual disability. Sources: ClinGen,Expert Review Green Mode of inheritance for Region: ISCA-37418-Loss was set to MONOALLELIC, autosomal or pseudoautosomal, imprinted status unknown Phenotypes for Region: ISCA-37418-Loss were set to Potocki-Lupski syndrome; hypotonia, poor feeding, failure to thrive, developmental delay particularly cognitive and language deficity, mild-moderate intellectual deficit, and neuropsychiatric disorders; Smith-Magenis syndrome; Structural cardiovascular anomalies (dilated aortic root, bicommissural aortic valve, atrial/ventricular and septal defects) and sleep disturbance; 182290; moderate intellectual disability, delayed speech and language skills, distinctive facial features, sleep disturbances, and behavioral problems; hypotonia, failure to thrive, mental retardation, pervasive developmental disorders, congenital anomalies; Dental abnormalities |
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| Intellectual disability | MAGEL2 | BRIDGE consortium edited their review of MAGEL2 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability | MAGEL2 | BRIDGE consortium edited their review of MAGEL2 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability | MAGEL2 | BRIDGE consortium reviewed MAGEL2 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||