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| Early onset or syndromic epilepsy v4.40 | RHEB | Arina Puzriakova changed review comment from: Comment on list classification: There is sufficient evidence to support an association with epilepsy; however, it is worth noting that variants are brain-specific somatic. Still adding to this panel as other somatic mosaic genes (e.g. GNAQ, MTOR, TSC1, TSC2) are included.; to: Comment on list classification: There is sufficient evidence to support an association with epilepsy; however, it is worth noting that variants are brain-specific somatic. Still adding to this panel as other somatic mosaic genes are included (e.g. GNAQ, MTOR, TSC1, TSC2). | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Early onset or syndromic epilepsy v4.40 | RHEB | Arina Puzriakova changed review comment from: Comment on list classification: The rating of this gene has been updated to Green following NHS Genomic Medicine Service approval.; to: Comment on list classification: There is sufficient evidence to support an association with epilepsy; however, it is worth noting that variants are brain-specific somatic. Still adding to this panel as other somatic mosaic genes (e.g. GNAQ, MTOR, TSC1, TSC2) are included. | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Early onset or syndromic epilepsy v2.577 | TIAM1 | Sarah Leigh edited their review of gene: TIAM1: Added comment: Associated with relevant phenotype in OMIM, but not associated with phenotype in Gen2Phen. PMID: 35240055 reports six TIAM1 variants in four unrelated cases (5 cases in total) of Neurodevelopmental disorder with language delay and seizures, OMIM:619908. All of the cases displayed seizures and intellectual disability, where an assessment was made. The drospohila ortholog (still life) and funtional studies supported this gene disease association (PMID: 35240055).; Changed rating: GREEN | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Early onset or syndromic epilepsy v2.543 | DNM1 | Arina Puzriakova changed review comment from: Comment on list classification: Currently, there is only enough evidence for an Amber rating for the biallelic form and so I have kept the MOI as just 'Monoallelic' at this time. If this is a genuine association, biallelic cases would still be picked by the Genomics England pipeline under this MOI. Added watchlist tag in anticipation of further biallelic cases emerging.; to: Comment on list classification: Currently, there is only enough evidence for an Amber rating for the biallelic form and so I have kept the MOI as just 'Monoallelic' at this time. Added watchlist tag in anticipation of further biallelic cases emerging. | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Early onset or syndromic epilepsy v2.518 | DPH5 |
Konstantinos Varvagiannis gene: DPH5 was added gene: DPH5 was added to Genetic epilepsy syndromes. Sources: Literature Mode of inheritance for gene: DPH5 was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: DPH5 were set to 35482014 Phenotypes for gene: DPH5 were set to Abnormality of prenatal development or birth; Neonatal hypotonia; Global developmental delay; Intellectual disability; Seizures; Abnormality of the cardiovascular system; Abnormality of the globe; Feeding difficulties; Short stature; Abnormality of head or neck Penetrance for gene: DPH5 were set to unknown Review for gene: DPH5 was set to AMBER Added comment: Shankar et al (2022 - PMID: 35482014) present evidence for a diphthamide-deficiency syndrome due to biallelic DPH5 pathogenic variants. As the authors summarize, DPH5 encodes a methyltransferase critical to the biosynthesis of diphthamide. Diphthamide is a post translationally modified histidine residue found in eukaryotic elongation factor 2 (eEF2). eEF2 is essential for mRNA translation and protein synthesis. The role of diphthamide is not clear, although it serves as a target for ADP-ribosylation, the latter resulting in inactivation of the eEF2 (inhibition of its translocation activity) and arrest of protein synthesis. Biosynthesis of diphthamide is complex involving multiple components (DPH1-DPH7) and the methylating co-factor S-adenosyl methionine, with 2 diphthamide-deficiency disorders due to biallelic DPH1 or DPH2 pathogenic variants and a NDD phenotype reported to date. The authors describe a phenotypic spectrum associated with biallelic DPH5 variants ranging from a prenatally lethal presentation to profound neurodevelopmental disorder. Details are provided on 5 individuals from 3 unrelated families. While one subject died at the age of few days due to multisystem complications, the phenotype appeared to be relatively consistent with prenatal findings (decreased fetal movements in 2 from 2 families, polyhydramnios in 2 from 2 families), hypotonia, global DD and ID (4/4 from 2 families - profound in 3), seizures (3/5 from 2 families - abnormal EEG in 4/4), cardiovascular findings (5/5, MVP and regurgitation in 2 from Fam1 || aortic dilatation in 2 sibs from Fam2 || VSD, ASD and hypopl. PA, pericardial effusion in 5th), GI issues (5/5, poor feeding in 4), short stature (4/4). Ocular findings were reported in 3/4 (gray sclerae in 2, ocular melanocytosis in 2). The authors describe some common craniofacial findings incl. broad/prominent forehead (5/5), sparse eyebrows (4/5), downturned corners of mouth or triangular chin (each in 3/5). WES/WGS revealed biallelic DPH5 variants in all affected individuals, namely: homozygosity for a missense variant in 2 sibs (NM_001077394.2:c.779A>G/p.His260Arg). Homozygosity for c.521dupA/p.Asn174LysTer10 for the individual deceased in the neonatal period (for this family there was significant history of spontaneous miscarriages/stillbirth/neonatal death). Two sibs born to non-consanguineous parents were compound htz for a stopgain and a missense SNV (c.619C>T/p.Arg207*, c.329A>G/p.Asn110Ser). In silico modeling revealed that the pLoF variants, not predicted to lead to NMD, likely remove the domain for interaction with eEF2 while the missense ones also affected interaction with eEF2. In recombinant MCF7 breast cancer cell line-derived DPH5-knockouts, transfected with recombinant expr. plasmids encoding wt or the 4 variants, the 2 truncating variants were shown to affect ADP-ribosylation of eEF2's diphthamide (total lack / minimal enzymatic activity for Arg207* and Asn174Lysfs respectively). Asn110Ser and His260Arg had residual activities which was thought to be explained by high expression levels compensating partial inactivation (given the multicopy plasmid-driven expression). ADP-ribosylation assays in S. cerevisiae demonstrated loss of function for the 2 truncating variants. Although the 2 missense variants retained sufficient activity to produce diphthamide (assayed through toxin induced ADP-ribosylation of eEF2), more sensitive assays indicated that diphthamide synthesis was also partially compromised for both variants. Generation of a knockin mouse model for His260Arg, appeared to recapitulate the human phenotypes with craniofacial, ophthalmologic, cardiac and visceral abnormalities and hmz mice being subviable. A single homozygous liveborn mouse had low birthweight, FTT, craniofacial dysmorphology, polydactyly, abnormal grooming behavior and early death. Few heterozygous embryos had craniofacial features, decreased body weight, reduced neuromuscular function without other abnormalities, either due to their inbred background or in the context of milder phenotype of heterozygosity in mice. DPH5 is ubiquitously expressed in all human tissues. The gene has a pLI of 0 and LOEUF score of 0.77 (0.48-1.27) in gnomAD. The authors refer to unpublished data, noting that complete absence of DPH5 is incompatible with life with embryonic lethality of a Dph5(ko/ko) line. The phenotype bears similarities to DPH1- and DPH2- related NDDs (both AR / green and amber respectively in ID panel) and appears to be more severe compared to the phenotype of de novo EEF2 variants (cited PMID: 33355653). Please consider inclusion in the ID panel with amber (4 individuals from 2 families with ID) / green rating (rather consistent phenotype in 3 families probably representing a continuous spectrum, variant studies, mouse model, similarities with diphthamide-deficiency syndromes). Also consider amber rating in the epilepsy panel (3 individuals from 2 families reported). The gene may be also relevant in other gene panels e.g. for congenital heart disease, short stature, etc (not added). Sources: Literature |
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| Early onset or syndromic epilepsy v2.518 | ALKBH8 |
Helen Lord edited their review of gene: ALKBH8: Added comment: Saad et al, 2021: Third family of Egyptian descent harbouring a novel homozygous fs variant in the last exon of ALKBH8 - seen in two affected siblings, unaffected parents are het carriers. Parents are consanguineous. Variant likely to escape NMD. Both proband and aff sister had global dev delay, autisitic features, - neither have epilepy or seizure-like episodes. Do have structural brain abnormalities including mild-mod cerebral volume loss, mild to mod cerebellar vermian hypoplasia, variable degrees of thinning of the corpus callosum and abnormal myelination for age on brain MRI. Still would classify as amber...; Changed publications to: 33544954; Changed phenotypes to: Neurodevelopmental disorders |
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| Early onset or syndromic epilepsy v2.500 | FAR1 |
Arina Puzriakova changed review comment from: Comment on mode of inheritance: As only 2/4 families with biallelic variants in this gene presented with epilepsy, in 2019, the rating was set to Amber for this allelic requirement (no new related evidence since). However, there is now evidence supporting pathogenicity of monoallelic variants affecting the Arg480 residue, and the number of unrelated individuals with seizures (8) reaches the threshold for inclusion with the monoallelic MOI. FAR1 will be flagged for GMS expert review to determine the most appropriate MOI and rating on this panel (note that if MOI is set to 'Monoallelic' only, patients with biallelic variants would still be picked up by the Genomics England pipeline); to: Comment on mode of inheritance: As only 2/4 families with biallelic variants in this gene presented with epilepsy, in 2019, the rating was set to Amber for this allelic requirement (no new related evidence since). However, there is now evidence supporting pathogenicity of monoallelic variants affecting the Arg480 residue, and the number of unrelated individuals with seizures (8) reaches the threshold for inclusion with the monoallelic MOI. FAR1 will be flagged for GMS expert review to determine the most appropriate MOI and rating on this panel. |
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| Early onset or syndromic epilepsy v2.451 | DHDDS |
Arina Puzriakova Added comment: Comment on mode of inheritance: MOI should be updated from 'Both mono- and biallelic' to 'Monoallelic' at the next GMS panel update. Monoallelic variants are associated with a neurodevelopmental disorder comprising DD/ID, epilepsy and a variable movement disorder phenotype - >3 unrelated individuals reported in literature. To date, only one individual with biallelic variants and epilepsy has been reported (PMID: 27343064). This patient presented with glycosylation defects but no corroborating cases have been reported since. As only one patient has been described with biallelic inheritance and this phenotype, MOI should be set to 'Monoallelic' until evidence of additional cases emerges - biallelic variants would still be picked up by the Genomics England pipeline under this MOI. |
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| Early onset or syndromic epilepsy v2.386 | DNM1 | Arina Puzriakova Added comment: Comment on list classification: Currently, there is only enough evidence for an Amber rating for the biallelic form and so I have kept the MOI as just 'Monoallelic' at this time. If this is a genuine association, biallelic cases would still be picked by the Genomics England pipeline under this MOI. Added watchlist tag in anticipation of further biallelic cases emerging. | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Early onset or syndromic epilepsy v2.379 | FAR1 |
Arina Puzriakova changed review comment from: Comment on mode of inheritance: As only 2/4 families with biallelic variants in this gene presented with epilepsy, the rating was set to Amber for this allelic requirement. However, there is now also evidence supporting pathogenicity of monoallelic variants affecting the Arg480 residue, and the number of unrelated individuals with seizures (8) reaches the threshold for inclusion with the monoallelic MOI. FAR1 will be flagged for GMS expert review to determine the most appropriate MOI and rating on this panel (note that if MOI is set to 'Monoallelic' only, patients with biallelic variants would still be picked up by the Genomics England pipeline); to: Comment on mode of inheritance: As only 2/4 families with biallelic variants in this gene presented with epilepsy, in 2019, the rating was set to Amber for this allelic requirement (no new related evidence since). However, there is now evidence supporting pathogenicity of monoallelic variants affecting the Arg480 residue, and the number of unrelated individuals with seizures (8) reaches the threshold for inclusion with the monoallelic MOI. FAR1 will be flagged for GMS expert review to determine the most appropriate MOI and rating on this panel (note that if MOI is set to 'Monoallelic' only, patients with biallelic variants would still be picked up by the Genomics England pipeline) |
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| Early onset or syndromic epilepsy v2.379 | FAR1 |
Arina Puzriakova Added comment: Comment on mode of inheritance: As only 2/4 families with biallelic variants in this gene presented with epilepsy, the rating was set to Amber for this allelic requirement. However, there is now also evidence supporting pathogenicity of monoallelic variants affecting the Arg480 residue, and the number of unrelated individuals with seizures (8) reaches the threshold for inclusion with the monoallelic MOI. FAR1 will be flagged for GMS expert review to determine the most appropriate MOI and rating on this panel (note that if MOI is set to 'Monoallelic' only, patients with biallelic variants would still be picked up by the Genomics England pipeline) |
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| Early onset or syndromic epilepsy v2.333 | NCDN | Arina Puzriakova changed review comment from: Comment on mode of inheritance: Setting MOI to 'Monoallelic' as only one biallelic case reported to date, and patients with biallelic variants would still be picked up by the Genomics England pipeline.; to: Comment on mode of inheritance: Setting MOI to 'Monoallelic' as only one biallelic case reported to date, and patients with biallelic variants would still be picked up by the Genomics England pipeline if this gene is upgraded to Green on this panel in the future. | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Early onset or syndromic epilepsy v2.332 | NCDN | Arina Puzriakova Added comment: Comment on mode of inheritance: Setting MOI to 'Monoallelic' as only one biallelic case reported to date, and patients with biallelic variants would still be picked up by the Genomics England pipeline. | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Early onset or syndromic epilepsy v2.25 | RNF13 | Sarah Leigh changed review comment from: Associated with relevant phenotype in OMIM and as probable Gen2Phen gene. At least 2 variants reported in 3 unrelated cases, together with supportive functional studies.; to: Associated with relevant phenotype in OMIM and as probable Gen2Phen gene. At least 2 variants reported in 3 unrelated cases, together with supportive functional studies. Gain-of-function mechanism has been reported, therefore the mutational spectrum may be limited and is still to be determined through further cases or further functional studies (view of Helen Britain, GeL Clincial Fellow). | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Early onset or syndromic epilepsy v1.497 | OXR1 |
Konstantinos Varvagiannis gene: OXR1 was added gene: OXR1 was added to Genetic epilepsy syndromes. Sources: Literature Mode of inheritance for gene: OXR1 was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: OXR1 were set to https://doi.org/10.1016/j.ajhg.2019.11.002 Phenotypes for gene: OXR1 were set to Central hypotonia; Global developmental delay; Delayed speech and language development; Intellectual disability; Seizures; Abnormality of the cerebellum Penetrance for gene: OXR1 were set to Complete Review for gene: OXR1 was set to GREEN Added comment: Wang et al (2019 - https://doi.org/10.1016/j.ajhg.2019.11.002 ) report on 5 individuals (from 3 families) with biallelic OXR1 LoF variants. Common features included hypotonia (4/5), severe global DD (5/5) and speech delay (5/5), ID (5/5), epilepsy (5/5) with cerebellar dysplasia/atrophy (5/5) and in some scoliosis. All were investigated by exome sequencing and were found to harbor biallelic loss-of-function variants (2 splice-site, a stopgain and a frameshift one) either in homozygosity (2 consanguineous families) or in compound heterozygosity. In all cases parental segregation studies were compatible and in one family, an unaffected sib shown to be carrier. Althouhgh OXR1 has been shown to affect several processes (among others DNA lesions induced by oxidative stress in E.coli, neuronal maintenance, mitochondrial morphology and DNA maintenance, etc), its mechanism of action is still not well defined. There are 6 RefSeq transcripts, the longest (NM_018002.3) encoding 3 protein domains (LysM, GRAM, TLDc). The TLDc domain is encoded by all transcripts. Identified variants affected (probably all - fig1D) transcripts expressed in the CNS, namely NM_018002.3, NM_001198532.1, NM_181354.4. The 3 transcripts not expressed in the CNS are NM_001198533.1, NM_001198534.1 and NM_001198535.1. Western blot with 2 different antibodies which would bind upstream of the truncation site failed to detect presence of truncated proteins in 2 affected individuals from 2 families. The Drosophila homolog of OXR is mustard (mtd). The authors provide evidence that loss of mtd is lethal. This was however rescued by expression of an 80kb fly BAC clone covering mtd, or the fly mtd-RH isoform cDNA, or a short human OXR1 cDNA containing only the TLDc domain or a human NCOA7 cDNA. The latter is another human mtd homolog which also contains the TLDc domain. As a result the TLDc domain compensated sufficiently for loss of mtd. Flies that survived displayed bang sensitivity and climbing defects the former assay being suggestive of susceptibility to seizures and the latter of impaired neurological/muscular function. The authors provided evidence that mtd is broadly expressed in the fly CNS. RNAi mediated mtd knockdown specific to neurons (elav/nSyb-GAL4 expression of mtd RNAi) led to lethal eclosion defects for RNAis targeting most (18)/all(23) mtd isoforms. Lifespan was increased upon expression of human OXR1 cDNA. Neuronal loss and vacuolization was demonstrated and additional experiments in R7 photoreceptors showed presence of aberrant lysosomal structures (autolysosomes, autophagosomes and/or endolysosomes). Aberrant lysosomal structures were also observed in fibroblasts from affected individuals (accumulation of lysosomes and/or presence of highly aberrant compartments with content typical of lysosomal dysfunction). Overall the data presented suggest a critical role for OXR1 in lysosomal biology. Although previous reports suggested that OXR1 is involved in oxidative stress resistance, studies performed by the authors suggested that oxidative stress is probably not the driver of the mutant fly defects. Sources: Literature |
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| Early onset or syndromic epilepsy v1.189 | STIL | Rebecca Foulger reviewed gene: STIL: Rating: AMBER; Mode of pathogenicity: ; Publications: ; Phenotypes: ; Mode of inheritance: | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Early onset or syndromic epilepsy v1.188 | STIL | Tracy Lester reviewed gene: STIL: Rating: RED; Mode of pathogenicity: ; Publications: ; Phenotypes: Microcephaly 7, primary, 612703; Mode of inheritance: BIALLELIC, autosomal or pseudoautosomal | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Early onset or syndromic epilepsy v1.187 | STIL |
Rebecca Foulger gene: STIL was added gene: STIL was added to Genetic epilepsy syndromes. Sources: Wessex and West Midlands GLH,Expert Review Red,NHS GMS Mode of inheritance for gene: STIL was set to BIALLELIC, autosomal or pseudoautosomal Phenotypes for gene: STIL were set to Microcephaly 7, primary, 612703 |
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| Early onset or syndromic epilepsy v1.79 | CSNK2B | Rebecca Foulger Added comment: Comment on list classification: Updated rating from Amber to Green based on recent 2019 paper, PMID:30655572, which reports two further unrelated cases (Japanese and Malaysian) of de novo CSNK2B variants in patients with epilepsy. Although CSNK2B is still not associated with a disorder in OMIM or Gene2Phenotype, this takes the count from two to four cases (from 3 different papers) and is therefore sufficient for a Green rating on this panel. | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Early onset or syndromic epilepsy v1.77 | CNPY3 | Rebecca Foulger Added comment: Comment on list classification: Re-reviewed gene:disease association for CNPY3 during curation of GMS panel. Amber rating is still appropriate: Probable Disease confidence rating in DD-G2P for EARLY ONSET EPILEPTIC ENCEPHALOPATHY, and literature evidence remains at 3 patients from 2 unrelated families from one paper (PMID:29394991) with limited segregation data from one of the families. | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Early onset or syndromic epilepsy v1.64 | CUX2 | Rebecca Foulger commented on gene: CUX2: Re-assessing the rating of CUX2 following a new Green review by Deb Pals (the new review contains the same paper (PMID:29630738) as described by Konstantinos Varvagiannis). CUX2 is now associated with an OMIM disorder: Epileptic encephalopathy, early infantile, 67, 618141. The DD-Gene2Phenotype rating is still probable. | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Early onset or syndromic epilepsy v0.1095 | MACF1 |
Konstantinos Varvagiannis gene: MACF1 was added gene: MACF1 was added to Genetic epilepsy syndromes. Sources: Literature,Expert Review Mode of inheritance for gene: MACF1 was set to MONOALLELIC, autosomal or pseudoautosomal, NOT imprinted Phenotypes for gene: MACF1 were set to Intellectual disability; Seizures; Lissencephaly; Brainstem dysplasia Penetrance for gene: MACF1 were set to unknown Mode of pathogenicity for gene: MACF1 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: MACF1 was set to GREEN Added comment: Dobyns et al. (doi.org/10.1016/j.ajhg.2018.10.019) report on 9 individuals (all unrelated appart from a pair of monozygotic twins) with de novo variants in MACF1. All patients presented lissencephaly and brainstem hypoplasia with associated intellectual disability (9/9) and seizures (9/9). Seven of these individuals had de novo missense variants within the GAR domain and an eighth had a deletion of several exons also spanning this domain and leading to an in-frame deletion. A further ninth patient had a de novo missense variant in the spectrin repeat domain and was found to have similar features although the brainstem dysplasia was rather subtle. 5 missense variants (4 of which in the GAR domain) and an intragenic deletion are reported in total. The variants in the GAR domain were predicted to have important effect in the zinc-binding pocket. The spectrin repeat (SR4) is thought to have an important role for the function of MACF1 and further to neuronal migration. Knockdown of Macf1 in mice has been shown to result in developmental defects similar to the human malformation. The authors note that several high-confidence loss-of-function mutations are listed in ExAC and as a result this type of variants could be non-pathogenic (or lead to neurodevelopmental disorders with reduced penetrance). Still MACF1 has a pLI of 1.0. As for the missense variants, the authors suggest either a gain-of-function or dominant negative mechanism. Caution should be taken when interpreting variants as the ENST00000372915.7 (or MACF1-204) transcript is used for the predicted protein changes, although ENST00000361689.6 or MACF1-203 (corresponding to NM_012090.5) has also been used in some tables or figures. As a result, this gene can be considered for inclusion in this panel probably as green. Sources: Literature, Expert Review |
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| Early onset or syndromic epilepsy v0.1060 | PHACTR1 |
Konstantinos Varvagiannis gene: PHACTR1 was added gene: PHACTR1 was added to Genetic epilepsy syndromes. Sources: Literature,Expert Review Mode of inheritance for gene: PHACTR1 was set to MONOALLELIC, autosomal or pseudoautosomal, NOT imprinted Publications for gene: PHACTR1 were set to 30256902; 23033978; 28135719 Phenotypes for gene: PHACTR1 were set to Global developmental delay; Intellectual disability; Seizures Penetrance for gene: PHACTR1 were set to unknown Review for gene: PHACTR1 was set to GREEN Added comment: PMID: 30256902 (Hamada et al., 2018) reports on the phenotype of 2 unrelated individuals with de novo missense variants in PHACTR1. Both had a diagnosis of West syndrome (infantile spasms and intellectual disability). As the authors note, 3 individuals with missense variants in this gene (in 2 of whom as a de novo occurrence) were previously identified : - In PMID: 23033978 (de Ligt et al., 2012) one patient with ID and epilepsy and a de novo missense variant. - In PMID: 28135719 (DDD study in 2017) one individual with developmental disorder and a further de novo missense SNV. - PMID: 27457812 (Riazuddin et al., 2017) is an exome sequencing study for intellectual disability. (NB. In the supplement of this study, the consanguineous parents of the affected individuals appear to be heterozygous for this variant but the affected children non-carriers). Extensive functional studies for the 2 novel as the 2 previously reported variants (from PMIDs: 23033978, 28135719) support a dominant negative effect for all 4 variants. One of these variants (reported by de Ligt al.) for which pathogenicity is suggested has however been reported 4 times in gnomAD. The authors discuss the possibility of reduced penetrance and/or other phenotypes in the individuals from gnomAD. Although all the variants studied appear to have a dominant negative effect, Phactr1-knockdown neurons seem to display aberrant migration and morphological phenotype. As a result, the eventual effect of haploinsufficiency probably needs to be further clarified. (Still PHACTR1 has a pLI score of 0.66 in ExAC). At least 3 individuals appeared to have epilepsy (as this information is not available for the DDD participant). 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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