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| Intellectual disability - microarray and sequencing v3.1707 | STUB1 | Sarah Leigh Added comment: Comment on mode of inheritance: Associated with relevant phenotype in OMIM, but not associated with phenotype in Gen2Phen. Numerous STUB1 variants have been reported in both Autosomal recessive spinocerebellar ataxia type 16, OMIM:615768 and Spinocerebellar ataxia 48, OMIM:618093. PMIDs 34906452; 35493319 report digenic occurrence of heterozygous STUB1 variants, with TBP_CAG expansions of 41-46. They question the validy of Spinocerebellar ataxia 48 (OMIM:618093) as a condition and whether it should be included into Spinocerebellar ataxia 17 (OMIM:607136). | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v3.1564 | ADD1 |
Konstantinos Varvagiannis gene: ADD1 was added gene: ADD1 was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: ADD1 was set to BOTH monoallelic and biallelic, autosomal or pseudoautosomal Publications for gene: ADD1 were set to 34906466 Phenotypes for gene: ADD1 were set to Global developmental delay; Intellectual disability; Seizures; Ventriculomegaly; Abnormality of the corpus callosum Penetrance for gene: ADD1 were set to unknown Review for gene: ADD1 was set to AMBER Added comment: A recent study suggests an ADD1-related phenotype (3 subjects with monoallelic de novo variants/1 with biallelic variants) with DD/ID and ventriculomegaly or corpus callosum dysgenesis and possibly seizures among the features. There is currently no associated phenotype in other databases (OMIM, G2P, SysID, PanelApp Australia). Consider inclusion in the current panel with amber / green rating (3 subjects/variants/families, role of the gene and mouse models recapitulating ventriculomegaly/CC abnormalities, relevant expression, variant studies demonstrating abn. protein levels and/or disruption of adducin heterodimer formation || monoallelic vs bi-allelic variants). Please consider inclusion in other possibly relevant gene panels (e.g. for corpus callosum / ventriculomegaly) [ Not added ]. -------- Qi et al (2022 - PMID: 34906466) describe the phenotype of 3 unrelated individuals with monoallelic de novo ADD1 pathogenic variants as well as of a fourth homozygous for a missense SNV. Overall, the authors propose a common phenotype consisting of morphological brain abnormalities (incl. ventriculomegaly and corpus callosum dysgenesis) and neurological symptoms such as DD and/or ID and attention deficit. All individuals were investigated with singleton/trio ES. De novo variants - phenotype: One individual investigated for hypotonia, DD & ID, partial ACC, well controlled seizures (on ketogenic diet) and proportional short stature harbored a de novo stopgain variant (NM_014189.3:c.1418G>A / p.Trp473*) absent from gnomAD. Another affected subject with hypotonia, FTT/feeding difficulties, mild motor delays complete ACC, a seizure (2y11m), staring spells without EEG correlate, and fatigue (with low coenz. Q10, and complex I & IV deficiency in muscle biopsy) had a de novo fs variant (NM_001119:c.2029_2039del / p.Glu680Argfs*7 - gnomAD:0) and a VUS in a gene not associated with phenotype to date. A 3rd subject investigated for seizures (onset:1y), speech delay, mild ID, ADHD, without MRI abnormalities harbored a de novo missense SNV (NM_001119:c.670C>T / p.His224Tyr - gnomAD:0) and with cmp htz for 2 missense SPTBN2 SNV not fitting the phenotype (no ataxia). Biallelic variants - phenotype: One individual with ID, and ACC, abnormal sulcation, enlarged lateral and 3rd ventricles, abnormal of white matter and hypoplastic vermis upon MRI was reported to harbor in homozygosity a missense SNV (NM_001119:c.169A>T / p.Arg57Trp). There was an additional variant in a gene without associated phenotype to date and not expressed in brain. Role of the encoded protein: ADD1 encodes adducin 1/alpha (similar to ADD2, ADD3 encoding other adducins). As the authors note, adducins are cytoskeleton proteins critical for osmotic rigidity and cell shape. In neurons they have been reported to form membrane associated periodic ring-like structures with actin and β-spectrin. Deletion of Add1 in mice results in increased MPS ring diameter and axonal degeneration (several refs provided). ADD1/2/3 form heterodimers which in turn form heterotetramers. ADD1 is expressed in most tissues. Mouse model: Previous mouse models have demonstrated that Add1 null mice have also undetectable ADD2/3 (suggesting a role for stabilization of the latter) and exhibit growth delay, anemia and develop lethal hydrocephalus and ventriculomegaly with 50% penetrance (cited PMIDs: 27068466, 18723693). Here the authors demonstrated that surviving mice had ventriculomegaly and thinning of corpus callosum thus recapitulating the respective human phenotypes. Htz mice also presented thinner CC, though not to a statistically significant extent. ADD1 expression and isoforms: - Performing mRNA studies and W.Blot in (developing - GW15-17) human or mouse brain (E12.5-P40) the authors demonstrated dynamic expression of ADD1 with differentially expressed isoforms, notably alternative splicing of ex10 and ex15 with NM_176801 (extended ex10, inclusion of ex15) corresponding to a neuronal isoform and NM_001119 (shorter ex10, exclusion of ex15) corresponding to a neural progenitor cell (NPC) isoform. - Variants here reported appear to affect both isoforms with the exception of NM_001119:c.2029_2039del / p.Glu680Argfs*7 affecting only the longer NPC one. - PTBP1 is an RNA binding protein expressed in NPCs known to suppress neuronal exon insertion. The authors demonstrated in mouse Neuro2A cells, through shRNA targeting of Ptbp1, that the latter suppresses the neuronal Add1 isoform. Variant studies demonstrated that effect of variants was mediated by decreased protein levels and/or disruption of adducin complex formation (ADD1-ADD2 dimer formation known to be mediated by N- and C- terminal ADD1 domains): - Expression of Arg57Trp (found in hmz in one individual) NPC and neuronal isoforms in Neuro2a cells showed that while protein levels were not significantly affected, there were (also) truncated protein products for both isoforms suggesting that aberrant splicing or protein translation/cleavage may apply. - The authors generated HEK293FT cells for the truncating variants demonstrating decreased protein levels (using N-/C- terminal antibodies). - Reduced (HA-tagged)-ADD1-(V5-tagged)-ADD2 protein interaction was shown to apply for the Arg57Trp and Arg473* in HEK293FT cells. Similarly in Neuro2a cells, reduced ADD1-ADD2 interaction was shown for His224Tyr. Sources: Literature |
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| Intellectual disability - microarray and sequencing v3.1444 | TBP | Arina Puzriakova Added comment: Comment on mode of inheritance: Lack of phenotypic relevance for SNVs - nucleotide repeat expansion mechanism | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v3.1444 | TBP | Arina Puzriakova Mode of inheritance for gene: TBP was changed from Other - please specify in evaluation comments to Other | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v3.1443 | TBP | Arina Puzriakova Mode of pathogenicity for gene: TBP was changed from to Loss-of-function variants (as defined in pop up message) DO NOT cause this phenotype - please provide details in the comments | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v3.1442 | TBP | Arina Puzriakova Phenotypes for gene: TBP were changed from Spinocerebellar ataxia 17, 607136; {Parkinson disease, susceptibility to}, 168600 to Spinocerebellar ataxia 17, OMIM:607136 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v3.1441 | TBP |
Arina Puzriakova Tag nucleotide-repeat-expansion tag was added to gene: TBP. Tag currently-ngs-unreportable tag was added to gene: TBP. |
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| Intellectual disability - microarray and sequencing v3.930 | TBP | Arina Puzriakova Source: Expert Review Amber was removed from gene: TBP | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v3.421 | LTBP3 |
Arina Puzriakova Source Expert Review Red was added to LTBP3. Rating Changed from Amber List (moderate evidence) to Red List (low evidence) |
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| Intellectual disability - microarray and sequencing v3.421 | LTBP2 |
Arina Puzriakova Source Expert Review Red was added to LTBP2. Rating Changed from Amber List (moderate evidence) to Red List (low evidence) |
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| Intellectual disability - microarray and sequencing v3.255 | TAF1C |
Konstantinos Varvagiannis gene: TAF1C was added gene: TAF1C was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: TAF1C was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: TAF1C were set to 32779182 Phenotypes for gene: TAF1C were set to Global developmental delay; Intellectual disability; Spasticity; Strabismus; Seizures; Abnormality of nervous system morphology Penetrance for gene: TAF1C were set to Complete Review for gene: TAF1C was set to AMBER Added comment: Knuutinen et al (2020 - PMID: 32779182) report on 2 individuals from 2 consanguineous families, homozygous for TAF1C missense variants. Both presented with an early onset neurological phenotype with severe global DD, ID (2/2 - moderate and profound), spasticity (2/2), ophthalmic findings (strabismus 2/2, nystagmus 1/2). Epilepsy, abnormal brain MRI (cerebral and cerebellar atrophy and white matter hyperintensities) as well and additional findings were reported in one (always the same individual). Following a normal CMA, exome in the first case revealed a homozygous missense SNV (NM_005679.3:c.1165C>T / p.Arg389Cys) supported by in silico predictions. mRNA and protein levels were substantially reduced in fibroblasts from this subject. Only the patient and parents were tested for the variant but not 3 unaffected sibs (fig1). The second individual was homozygous for another missense variant (p.Arg405Cys) also supported by in silico predictions. The girl was the single affected person within the family with an unaffected sib and parents heterozygous for the variant. Several other unaffected relatives in the extended pedigree were either carriers for this variant or homozygous for the wt allele. TAF1C encodes the TATA-box binding protein associated factor (TAF) RNA polymerase I subunit. RNA polymerase I (Pol I) transcribes genes to produce rRNA. For Pol I to initiate transcription, two transcription factors are required : UBF (upstream binding factor encoded by UBTF) and SL1 (selectivity factor 1). The latter is formed by TBP (TATA-binding protein) and 3 Pol I-specific TBP-associated factors (TAFs). A recurrent de novo missense variant in UBTF (encoding the other Pol I transcription factor) causes a disorder with highly similar features. The specific variant acts through a gain-of-function mechanism (and not by LoF which appears to apply for TAF1C based on expression data). The authors hypothesize that altered Pol I activity and resulting ribosomal stress could cause the microcephaly and leukodystrophy (both reported in 1 - the same - individual). As a result, TAF1C may be considered for inclusion in the ID panel with amber rating pending further evidence. Sources: Literature |
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| Intellectual disability - microarray and sequencing v3.253 | LTBP3 | Arina Puzriakova commented on gene: LTBP3 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v3.253 | LTBP2 | Arina Puzriakova commented on gene: LTBP2 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v3.0 | LTBP3 | Zornitza Stark reviewed gene: LTBP3: Rating: RED; Mode of pathogenicity: None; Publications: ; Phenotypes: Dental anomalies and short stature 601216, Geleophysic dysplasia 3 617809; Mode of inheritance: None | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v3.0 | LTBP2 | Zornitza Stark reviewed gene: LTBP2: Rating: RED; Mode of pathogenicity: None; Publications: ; Phenotypes: Weill-Marchesani syndrome 3, recessive, MIM# 614819, Glaucoma 3, primary congenital, MIM# 613086, Microspherophakia and/or megalocornea, with ectopia lentis and with or without secondary glaucoma, MIM# 251750; Mode of inheritance: None | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v2.991 | CTBP1 | Rebecca Foulger Tag missense tag was added to gene: CTBP1. | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v2.980 | CTBP1 | Rebecca Foulger Classified gene: CTBP1 as Green List (high evidence) | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v2.980 | CTBP1 | Rebecca Foulger Gene: ctbp1 has been classified as Green List (High Evidence). | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v2.979 | CTBP1 | Rebecca Foulger commented on gene: CTBP1 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v2.953 | CTBP1 | Chris Buxton reviewed gene: CTBP1: Rating: GREEN; Mode of pathogenicity: Other; Publications: 27094857, 31041561; Phenotypes: intellectual disability, ataxia, hypotonia, tooth enamel defect; Mode of inheritance: MONOALLELIC, autosomal or pseudoautosomal, NOT imprinted | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v2.941 | CTBP1 | Rebecca Foulger Phenotypes for gene: CTBP1 were changed from Generalized hypotonia; Global developmental delay; Intellectual disability; Ataxia; Abnormality of dental enamel to Hypotonia, ataxia, developmental delay, and tooth enamel defect syndrome, 617915 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v2.938 | CTBP1 |
Konstantinos Varvagiannis changed review comment from: 12 individuals with a recurrent missense variant in CTBP1 have been reported, all summarized in the last article: - Beck et al. 2016 (PMID: 27094857) : 4 individuals - Sommerville et al. 2017 (PMID: 28955726) : 1 subject - Beck et al. 2019 (PMID: 31041561) : 7 further individuals Features included hypotonia, DD/ID, ataxia and tooth enamel defects. The degree of ID - when present - appeared to be highly variable based at least on the first two reports (3 individuals with severe ID, 1 with borderline-normal intellectual functioning, 1 did not exhibit ID) where this feature was further commented on. A recurrent missense variant was found in all 12 affected individuals [NM_001328.2:c.1024C>T - p.(Arg342Trp) or NM_001012614.1:c.991C>T - p.(Arg331Trp)]. De novo occurrence this SNV was shown for (almost) all individuals, although in one case maternal sequencing reads were compatible with low-level somatic mosaicism (4/75 reads) not detected by Sanger sequencing. The mother of this individual was phenotypically normal. The variant is absent from gnomAD. Several in silico predictions (SIFT, PolyPhen2, MutationTaster, etc) suggest a deleterious effect. Given recurrence of this specific variant, and presence of LoF ones in healthy individuals (pLI of 0.98 though in gnomAD) Beck et al. suggested a dominant negative or a gain-of-function effect rather than a loss of function mechanism. Exclusion of alternative causes: was mainly discussed for the subject reported by Sommerville et al., due to the primary suspicion of a mitochondrial disorder (sequencing and research for mtDNA rearrangements, additional analysis of nuclear genes for mitochondrial disorders). Expression: CTBP1 encodes C-terminal binding protein 1, with expression among others in brain and cerebellum (https://gtexportal.org/home/gene/CTBP1). Role and Functional studies: - The major nuclear isoform of CTBP1 (corresponding to NM_001328.2) and of its paralog CTBP2 function as transcriptional regulators (corepressors). The PLDLS(Pro-Leu-Asp-Leu-Ser)-binding cleft domain where this variant lies, acts as a high-affinity protein-binding interface to recruit DNA-binding repressors and chromatin modifying enzymes (PMID: 17967884). - In a human glioblastoma cell line interaction of various cofactors with (Flag-tagged) CTBP1 was studied by immunoprecitipation with the Flag antibody and subsequent proteomic (LC-MS) analysis. This demonstrated reduced interaction in the case of R342W (compared to wt) with Zn-finger transcription factors, histone deacetylases, histone methyltransferases, histone H3-K4 demethylase etc. Western blot analyses also revealed reduced interaction of the R342W with several CTBP cofactors. - RNA-seq analysis in glioblastoma cell line revealed similar overall transcriptional profiles between wt and R342W though multiple RNA species showed significant differences (eg. genes involved in the biological processes of mitotic nuclear division, DNA repair, transcription and regulation of transcription among those that were most upregulated and genes involved in brain development among the most downregulated). - Patient fibroblasts under conditions of glucose deprivation exhibited strikingly more cell death compared to control fibroblasts. Study of mRNA levels of pro-apoptotic genes by q-RT-PCR revealed that Noxa expression under glucose deprivation vs under normal glucose was 8 to 10-fold enhanced for control fibroblasts, but more than 30-fold enhanced in the case patient fibroblasts. Western blot analyses were also in line with this. - Mitochondrial dysfunction (probably secondary) with evidence of decreased complex I (and complex IV) activities in skeletal muscle was the case for 2 individuals among multiple patients who had muscle biopsies. Animal models: - Beck et al. discuss previously published mouse models where Ctbp1/2 both play overlapping transcriptional roles during development. Homozygous deletion of Ctbp2 is embryonically lethal (>E10.5). Homozygous deletion of Ctbp1 results in viable mice with reduced size and lifespan (Cited: Hildebrand et al. 2002 - PMID: 12101226) - As commented on by Sommerville et al., Ctbp1 knockout in mouse embryonic fibroblasts resulted in elongated mitochondria, abnormal mitochondrial cristae, diminished ATP and O2 consumption and mitochondrial membrane potential. ---- CTBP1 is associated with Hypotonia, ataxia, developmental delay, and tooth enamel defect syndrome (617915) in OMIM. It is not associated with any phenotype in G2P. Some diagnostic laboratories (eg. GeneDx participating in the first study and others) include this gene in panels for intellectual disability. ---- As a result, CTBP1 can be added in the current panel probably as green.; to: 12 individuals with a recurrent missense variant in CTBP1 have been reported, all summarized in the last article: - Beck et al. 2016 (PMID: 27094857) : 4 individuals - Sommerville et al. 2017 (PMID: 28955726) : 1 subject - Beck et al. 2019 (PMID: 31041561) : 7 further individuals Features included hypotonia, DD/ID, ataxia and tooth enamel defects. The degree of ID - when present - appeared to be highly variable based at least on the first two reports (3 individuals with severe ID, 1 with borderline-normal intellectual functioning, 1 did not exhibit ID) where this feature was further commented on. A recurrent missense variant was found in all 12 affected individuals [NM_001328.2:c.1024C>T - p.(Arg342Trp) or NM_001012614.1:c.991C>T - p.(Arg331Trp)]. De novo occurrence this SNV was shown for (almost) all individuals, although in one case maternal sequencing reads were compatible with low-level somatic mosaicism (4/75 reads) not detected by Sanger sequencing. The mother of this individual was phenotypically normal. The variant is absent from gnomAD. Several in silico predictions (SIFT, PolyPhen2, MutationTaster, etc) suggest a deleterious effect. Given recurrence of this specific variant, and presence of LoF ones in healthy individuals (pLI of 0.98 though in gnomAD) Beck et al. suggested a dominant negative or a gain-of-function effect rather than a loss of function mechanism. Exclusion of alternative causes: was mainly discussed for the subject reported by Sommerville et al., due to the primary suspicion of a mitochondrial disorder (sequencing and research for mtDNA rearrangements, additional analysis of nuclear genes for mitochondrial disorders). Expression: CTBP1 encodes C-terminal binding protein 1, with expression among others in brain and cerebellum (https://gtexportal.org/home/gene/CTBP1). Role and Functional studies: - The major nuclear isoform of CTBP1 (corresponding to NM_001328.2) and of its paralog CTBP2 function as transcriptional regulators (corepressors). The PLDLS(Pro-Leu-Asp-Leu-Ser)-binding cleft domain where this variant lies, acts as a high-affinity protein-binding interface to recruit DNA-binding repressors and chromatin modifying enzymes (PMID: 17967884). - In a human glioblastoma cell line interaction of various cofactors with (Flag-tagged) CTBP1 was studied by immunoprecitipation with the Flag antibody and subsequent proteomic (LC-MS) analysis. This demonstrated reduced interaction in the case of R342W (compared to wt) with Zn-finger transcription factors, histone deacetylases, histone methyltransferases, histone H3-K4 demethylase etc. Western blot analyses also revealed reduced interaction of the R342W with several CTBP cofactors. - RNA-seq analysis in glioblastoma cell line revealed similar overall transcriptional profiles between wt and R342W though multiple RNA species showed significant differences (eg. genes involved in the biological processes of mitotic nuclear division, DNA repair, transcription and regulation of transcription among those that were most upregulated and genes involved in brain development among the most downregulated). - Patient fibroblasts under conditions of glucose deprivation exhibited strikingly more cell death compared to control fibroblasts. Study of mRNA levels of pro-apoptotic genes by q-RT-PCR revealed that Noxa expression under glucose deprivation vs under normal glucose was 8 to 10-fold enhanced for control fibroblasts, but more than 30-fold enhanced in the case patient fibroblasts. Western blot analyses were also in line with this. - Mitochondrial dysfunction (probably secondary) with evidence of decreased complex I (and complex IV) activities in skeletal muscle was the case for 2 individuals among multiple patients who had muscle biopsies. Animal models: - Beck et al. discuss previously published mouse models where Ctbp1/2 both play overlapping transcriptional roles during development. Homozygous deletion of Ctbp2 is embryonically lethal (>E10.5). Homozygous deletion of Ctbp1 results in viable mice with reduced size and lifespan (Cited: Hildebrand et al. 2002 - PMID: 12101226) - As commented on by Sommerville et al., Ctbp1 knockout in mouse embryonic fibroblasts resulted in elongated mitochondria, abnormal mitochondrial cristae, diminished ATP and O2 consumption and mitochondrial membrane potential (Cited: Kim and Youn 2009 - PMID: 19136938). ---- CTBP1 is associated with Hypotonia, ataxia, developmental delay, and tooth enamel defect syndrome (617915) in OMIM. It is not associated with any phenotype in G2P. Some diagnostic laboratories (eg. GeneDx participating in the first study and others) include this gene in panels for intellectual disability. ---- As a result, CTBP1 can be added in the current panel probably as green. |
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| Intellectual disability - microarray and sequencing v2.938 | CTBP1 | Konstantinos Varvagiannis reviewed gene: CTBP1: Rating: GREEN; Mode of pathogenicity: Loss-of-function variants (as defined in pop up message) DO NOT cause this phenotype - please provide details in the comments; Publications: 27094857, 28955726, 31041561; Phenotypes: Hypotonia, ataxia, developmental delay, and tooth enamel defect syndrome (MIM 617915); Mode of inheritance: MONOALLELIC, autosomal or pseudoautosomal, imprinted status unknown; Current diagnostic: yes | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v2.938 | CTBP1 |
Konstantinos Varvagiannis changed review comment from: 12 individuals with a recurrent missense variant in CTBP1 have been reported, all summarized in the last article: - Beck et al. 2016 (PMID: 27094857) : 4 individuals - Sommerville et al. 2017 (PMID: 28955726) : 1 subject - Beck et al. 2019 (PMID: 31041561) : 7 further individuals Features included hypotonia, DD/ID, ataxia and tooth enamel defects. The degree of ID - when present - appeared to be highly variable based at least on the first two reports (3 individuals with severe ID, 1 with borderline-normal intellectual functioning, 1 did not exhibit ID) where this feature was further commented on. A recurrent missense variant was found in all 12 affected individuals [NM_001328.2:c.1024C>T - p.(Arg342Trp) or NM_001012614.1:c.991C>T - p.(Arg331Trp)]. De novo occurrence this SNV was shown for (almost) all individuals, although in one case maternal sequencing reads were compatible with low-level somatic mosaicism (4/75 reads) not detected by Sanger sequencing. The mother of this individual was phenotypically normal. The variant is absent from gnomAD. Several in silico predictions (SIFT, PolyPhen2, MutationTaster, etc) suggest a deleterious effect. Given recurrence of this specific variant, and presence of LoF ones in healthy individuals (pLI of 0.98 though in gnomAD) Beck et al. suggested a dominant negative or a gain-of-function effect rather than a loss of function mechanism. Exclusion of alternative causes: was mainly discussed for the subject reported by Sommerville et al., due to the primary suspicion of a mitochondrial disorder (sequencing and research for mtDNA rearrangements, additional analysis of nuclear genes for mitochondrial disorders). Expression: CTBP1 encodes C-terminal binding protein 1, with expression among others in brain and cerebellum (https://gtexportal.org/home/gene/CTBP1 ). Role and Functional studies: - The major nuclear isoform of CTBP1 (corresponding to NM_001328.2) and of its paralog CTBP2 function as transcriptional regulators (corepressors). The PLDLS(Pro-Leu-Asp-Leu-Ser)-binding cleft domain where this variant lies, acts as a high-affinity protein-binding interface to recruit DNA-binding repressors and chromatin modifying enzymes (PMID: 17967884). - In a human glioblastoma cell line interaction of various cofactors with (Flag-tagged) CTBP1 was studied by immunoprecitipation with the Flag antibody and subsequent proteomic (LC-MS) analysis. This demonstrated reduced interaction in the case of R342W (compared to wt) with Zn-finger transcription factors, histone deacetylases, histone methyltransferases, histone H3-K4 demethylase etc. Western blot analyses also revealed reduced interaction of the R342W with several CTBP cofactors. - RNA-seq analysis in glioblastoma cell line revealed similar overall transcriptional profiles between wt and R342W though multiple RNA species showed significant differences (eg. genes involved in the biological processes of mitotic nuclear division, DNA repair, transcription and regulation of transcription among those that were most upregulated and genes involved in brain development among the most downregulated). - Patient fibroblasts under conditions of glucose deprivation exhibited strikingly more cell death compared to control fibroblasts. Study of mRNA levels of pro-apoptotic genes by q-RT-PCR revealed that Noxa expression under glucose deprivation vs under normal glucose was 8 to 10-fold enhanced for control fibroblasts, but more than 30-fold enhanced in the case patient fibroblasts. Western blot analyses were also in line with this. - Mitochondrial dysfunction (probably secondary) with evidence of decreased complex I (and complex IV) activities in skeletal muscle was the case for 2 individuals among multiple patients who had muscle biopsies. Animal models: - Beck et al. discuss previously published mouse models where Ctbp1/2 both play overlapping transcriptional roles during development. Homozygous deletion of Ctbp2 is embryonically lethal (>E10.5). Homozygous deletion of Ctbp1 results in viable mice with reduced size and lifespan (Cited: Hildebrand et al. 2002 - PMID: 12101226) - As commented on by Sommerville et al., Ctbp1 knockout in mouse embryonic fibroblasts resulted in elongated mitochondria, abnormal mitochondrial cristae, diminished ATP and O2 consumption and mitochondrial membrane potential. ---- CTBP1 is associated with Hypotonia, ataxia, developmental delay, and tooth enamel defect syndrome (617915) in OMIM. It is not associated with any phenotype in G2P. Some diagnostic laboratories (eg. GeneDx participating in the first study and others) include this gene in panels for intellectual disability. ---- As a result, CTBP1 can be added in the current panel probably as green. Sources: Literature; to: 12 individuals with a recurrent missense variant in CTBP1 have been reported, all summarized in the last article: - Beck et al. 2016 (PMID: 27094857) : 4 individuals - Sommerville et al. 2017 (PMID: 28955726) : 1 subject - Beck et al. 2019 (PMID: 31041561) : 7 further individuals Features included hypotonia, DD/ID, ataxia and tooth enamel defects. The degree of ID - when present - appeared to be highly variable based at least on the first two reports (3 individuals with severe ID, 1 with borderline-normal intellectual functioning, 1 did not exhibit ID) where this feature was further commented on. A recurrent missense variant was found in all 12 affected individuals [NM_001328.2:c.1024C>T - p.(Arg342Trp) or NM_001012614.1:c.991C>T - p.(Arg331Trp)]. De novo occurrence this SNV was shown for (almost) all individuals, although in one case maternal sequencing reads were compatible with low-level somatic mosaicism (4/75 reads) not detected by Sanger sequencing. The mother of this individual was phenotypically normal. The variant is absent from gnomAD. Several in silico predictions (SIFT, PolyPhen2, MutationTaster, etc) suggest a deleterious effect. Given recurrence of this specific variant, and presence of LoF ones in healthy individuals (pLI of 0.98 though in gnomAD) Beck et al. suggested a dominant negative or a gain-of-function effect rather than a loss of function mechanism. Exclusion of alternative causes: was mainly discussed for the subject reported by Sommerville et al., due to the primary suspicion of a mitochondrial disorder (sequencing and research for mtDNA rearrangements, additional analysis of nuclear genes for mitochondrial disorders). Expression: CTBP1 encodes C-terminal binding protein 1, with expression among others in brain and cerebellum (https://gtexportal.org/home/gene/CTBP1). Role and Functional studies: - The major nuclear isoform of CTBP1 (corresponding to NM_001328.2) and of its paralog CTBP2 function as transcriptional regulators (corepressors). The PLDLS(Pro-Leu-Asp-Leu-Ser)-binding cleft domain where this variant lies, acts as a high-affinity protein-binding interface to recruit DNA-binding repressors and chromatin modifying enzymes (PMID: 17967884). - In a human glioblastoma cell line interaction of various cofactors with (Flag-tagged) CTBP1 was studied by immunoprecitipation with the Flag antibody and subsequent proteomic (LC-MS) analysis. This demonstrated reduced interaction in the case of R342W (compared to wt) with Zn-finger transcription factors, histone deacetylases, histone methyltransferases, histone H3-K4 demethylase etc. Western blot analyses also revealed reduced interaction of the R342W with several CTBP cofactors. - RNA-seq analysis in glioblastoma cell line revealed similar overall transcriptional profiles between wt and R342W though multiple RNA species showed significant differences (eg. genes involved in the biological processes of mitotic nuclear division, DNA repair, transcription and regulation of transcription among those that were most upregulated and genes involved in brain development among the most downregulated). - Patient fibroblasts under conditions of glucose deprivation exhibited strikingly more cell death compared to control fibroblasts. Study of mRNA levels of pro-apoptotic genes by q-RT-PCR revealed that Noxa expression under glucose deprivation vs under normal glucose was 8 to 10-fold enhanced for control fibroblasts, but more than 30-fold enhanced in the case patient fibroblasts. Western blot analyses were also in line with this. - Mitochondrial dysfunction (probably secondary) with evidence of decreased complex I (and complex IV) activities in skeletal muscle was the case for 2 individuals among multiple patients who had muscle biopsies. Animal models: - Beck et al. discuss previously published mouse models where Ctbp1/2 both play overlapping transcriptional roles during development. Homozygous deletion of Ctbp2 is embryonically lethal (>E10.5). Homozygous deletion of Ctbp1 results in viable mice with reduced size and lifespan (Cited: Hildebrand et al. 2002 - PMID: 12101226) - As commented on by Sommerville et al., Ctbp1 knockout in mouse embryonic fibroblasts resulted in elongated mitochondria, abnormal mitochondrial cristae, diminished ATP and O2 consumption and mitochondrial membrane potential. ---- CTBP1 is associated with Hypotonia, ataxia, developmental delay, and tooth enamel defect syndrome (617915) in OMIM. It is not associated with any phenotype in G2P. Some diagnostic laboratories (eg. GeneDx participating in the first study and others) include this gene in panels for intellectual disability. ---- As a result, CTBP1 can be added in the current panel probably as green. Sources: Literature |
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| Intellectual disability - microarray and sequencing v2.938 | CTBP1 |
Konstantinos Varvagiannis gene: CTBP1 was added gene: CTBP1 was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: CTBP1 was set to MONOALLELIC, autosomal or pseudoautosomal, imprinted status unknown Publications for gene: CTBP1 were set to 27094857; 28955726; 31041561 Phenotypes for gene: CTBP1 were set to Generalized hypotonia; Global developmental delay; Intellectual disability; Ataxia; Abnormality of dental enamel Penetrance for gene: CTBP1 were set to unknown Mode of pathogenicity for gene: CTBP1 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: CTBP1 was set to GREEN gene: CTBP1 was marked as current diagnostic Added comment: 12 individuals with a recurrent missense variant in CTBP1 have been reported, all summarized in the last article: - Beck et al. 2016 (PMID: 27094857) : 4 individuals - Sommerville et al. 2017 (PMID: 28955726) : 1 subject - Beck et al. 2019 (PMID: 31041561) : 7 further individuals Features included hypotonia, DD/ID, ataxia and tooth enamel defects. The degree of ID - when present - appeared to be highly variable based at least on the first two reports (3 individuals with severe ID, 1 with borderline-normal intellectual functioning, 1 did not exhibit ID) where this feature was further commented on. A recurrent missense variant was found in all 12 affected individuals [NM_001328.2:c.1024C>T - p.(Arg342Trp) or NM_001012614.1:c.991C>T - p.(Arg331Trp)]. De novo occurrence this SNV was shown for (almost) all individuals, although in one case maternal sequencing reads were compatible with low-level somatic mosaicism (4/75 reads) not detected by Sanger sequencing. The mother of this individual was phenotypically normal. The variant is absent from gnomAD. Several in silico predictions (SIFT, PolyPhen2, MutationTaster, etc) suggest a deleterious effect. Given recurrence of this specific variant, and presence of LoF ones in healthy individuals (pLI of 0.98 though in gnomAD) Beck et al. suggested a dominant negative or a gain-of-function effect rather than a loss of function mechanism. Exclusion of alternative causes: was mainly discussed for the subject reported by Sommerville et al., due to the primary suspicion of a mitochondrial disorder (sequencing and research for mtDNA rearrangements, additional analysis of nuclear genes for mitochondrial disorders). Expression: CTBP1 encodes C-terminal binding protein 1, with expression among others in brain and cerebellum (https://gtexportal.org/home/gene/CTBP1 ). Role and Functional studies: - The major nuclear isoform of CTBP1 (corresponding to NM_001328.2) and of its paralog CTBP2 function as transcriptional regulators (corepressors). The PLDLS(Pro-Leu-Asp-Leu-Ser)-binding cleft domain where this variant lies, acts as a high-affinity protein-binding interface to recruit DNA-binding repressors and chromatin modifying enzymes (PMID: 17967884). - In a human glioblastoma cell line interaction of various cofactors with (Flag-tagged) CTBP1 was studied by immunoprecitipation with the Flag antibody and subsequent proteomic (LC-MS) analysis. This demonstrated reduced interaction in the case of R342W (compared to wt) with Zn-finger transcription factors, histone deacetylases, histone methyltransferases, histone H3-K4 demethylase etc. Western blot analyses also revealed reduced interaction of the R342W with several CTBP cofactors. - RNA-seq analysis in glioblastoma cell line revealed similar overall transcriptional profiles between wt and R342W though multiple RNA species showed significant differences (eg. genes involved in the biological processes of mitotic nuclear division, DNA repair, transcription and regulation of transcription among those that were most upregulated and genes involved in brain development among the most downregulated). - Patient fibroblasts under conditions of glucose deprivation exhibited strikingly more cell death compared to control fibroblasts. Study of mRNA levels of pro-apoptotic genes by q-RT-PCR revealed that Noxa expression under glucose deprivation vs under normal glucose was 8 to 10-fold enhanced for control fibroblasts, but more than 30-fold enhanced in the case patient fibroblasts. Western blot analyses were also in line with this. - Mitochondrial dysfunction (probably secondary) with evidence of decreased complex I (and complex IV) activities in skeletal muscle was the case for 2 individuals among multiple patients who had muscle biopsies. Animal models: - Beck et al. discuss previously published mouse models where Ctbp1/2 both play overlapping transcriptional roles during development. Homozygous deletion of Ctbp2 is embryonically lethal (>E10.5). Homozygous deletion of Ctbp1 results in viable mice with reduced size and lifespan (Cited: Hildebrand et al. 2002 - PMID: 12101226) - As commented on by Sommerville et al., Ctbp1 knockout in mouse embryonic fibroblasts resulted in elongated mitochondria, abnormal mitochondrial cristae, diminished ATP and O2 consumption and mitochondrial membrane potential. ---- CTBP1 is associated with Hypotonia, ataxia, developmental delay, and tooth enamel defect syndrome (617915) in OMIM. It is not associated with any phenotype in G2P. Some diagnostic laboratories (eg. GeneDx participating in the first study and others) include this gene in panels for intellectual disability. ---- As a result, CTBP1 can be added in the current panel probably as green. Sources: Literature |
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| Intellectual disability - microarray and sequencing v2.468 | SETBP1 | Louise Daugherty Source Victorian Clinical Genetics Services was added to SETBP1. | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing | TBP | BRIDGE consortium edited their review of TBP | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing | SETBP1 | BRIDGE consortium edited their review of SETBP1 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing | LTBP3 | BRIDGE consortium edited their review of LTBP3 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing | LTBP2 | BRIDGE consortium edited their review of LTBP2 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing | LTBP3 | Louise Daugherty classified LTBP3 as amber | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing | LTBP3 | Louise Daugherty commented on LTBP3 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing | LTBP2 | Louise Daugherty classified LTBP2 as amber | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing | LTBP2 | Louise Daugherty commented on LTBP2 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing | TBP | BRIDGE consortium edited their review of TBP | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing | SETBP1 | BRIDGE consortium edited their review of SETBP1 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing | LTBP3 | BRIDGE consortium reviewed LTBP3 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing | LTBP2 | BRIDGE consortium reviewed LTBP2 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing | TBP | Louise Daugherty classified TBP as amber | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing | TBP | Louise Daugherty commented on TBP | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing | TBP | BRIDGE consortium reviewed TBP | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing | SETBP1 | BRIDGE consortium reviewed SETBP1 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||