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| Intellectual disability syndromic and non-syndromic v0.5729 | USP14 |
Zornitza Stark gene: USP14 was added gene: USP14 was added to Intellectual disability syndromic and non-syndromic. Sources: Literature Mode of inheritance for gene: USP14 was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: USP14 were set to 38469793; 35066879 Phenotypes for gene: USP14 were set to Syndromic disease MONDO:0002254, USP14-related Review for gene: USP14 was set to AMBER Added comment: AMBER rating as two of the families had affected fetuses, one had a severely affected newborn, and fourth had a progressive course: none fit well with ID, though there's likely to be a continuum. PMID 35066879: 3 fetuses from 2 different branches of a consanguineous family, presenting with distal arthrogryposis, underdevelopment of the corpus callosum, and dysmorphic facial features. Exome sequencing identified a biallelic 4-bp deletion (c.233_236delTTCC; p.Leu78Glnfs*11) in USP14, and sequencing of family members showed segregation with the phenotype. Ubiquitin-specific protease 14 (USP14) encodes a major proteasome-associated deubiquitinating enzyme with an established dual role as an inhibitor and an activator of proteolysis, maintaining protein homeostasis. Usp14-deficient mice show a phenotype similar to lethal human multiple congenital contractures phenotypes, with callosal anomalies, muscle wasting, and early lethality, attributed to neuromuscular junction defects due to decreased monomeric ubiquitin pool. RT-qPCR experiment in an unaffected heterozygote revealed that mutant USP14 was expressed, indicating that abnormal transcript escapes nonsense-mediated mRNA decay. PMID 38469793: biallelic USP14 variants in four individuals from three unrelated families: one fetus, a newborn with a syndromic NDD, and two siblings affected by a progressive neurological disease. Specifically, the two siblings from the latter family carried two compound heterozygous variants c.8T>C p.(Leu3Pro) and c.988C>T p.(Arg330*), while the fetus had a homozygous frameshift c.899_902del p.(Lys300Serfs*24) variant and the newborn patient harbored a homozygous frameshift c.233_236del p.(Leu78Glnfs*11) variant. The fetus and the newborn had extensive brain malformations. Sources: Literature |
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| Intellectual disability syndromic and non-syndromic v0.4939 | PTPA |
Konstantinos Varvagiannis changed review comment from: Biallelic PTPA pathogenic variants lead to a form of ID with later-onset parkinsonism based on 4 individuals from 2 families in the literature. Affected individuals were homozygous for missense variants demonstrated to result to reduced mRNA and protein levels as well as PP2A complex activation. Drosophila studies support an age-dependent locomotor dysfunction. Variants in other PP2A-complex-related genes also lead to NDDs. Summary provided below. There is currently no associated phenotype in OMIM, G2P, PanelApp Australia or SysID. Consider inclusion in relevant panels (ID, Parkinsonism/movement disorders, etc) with amber rating pending further reports. ------ Fevga, Tesson et al (2022 - PMID: 36073231) describe the features of 4 individuals, from 2 unrelated families, with biallelic pathogenic PTPA variants. These presented with normal or delayed early milestones, learning disability and ID (mild to moderate) followed by progressive signs of parkinsonism (at the age of 11 yrs in 2 sibs, 15 yrs in another individual). Motor symptoms were responsive to levodopa and later to deep brain stimulation. Linkage analysis in one consanguineous family followed by exome revealed homozygosity for a missense PTPA variant (NM_178001:c.893T>G/p.Met298Arg). Exome sequencing in affected subjects from the 2nd family revealed homozygosity for a further missense variant (c.512C>A/p.Ala171Asp). There were no other candidate variants for the phenotype following parental / segregation studies. Role of the gene: As the authors discuss, PTPA (or PPP2R4) is ubiquitously expressed in all tissues incl. brain and encodes a phosphotyrosyl phosphatase activator of the dimeric form of protein phosphatase-2A (PP2A). PP2A in turn, is the major Ser/Thr phosphatase in brain targeting a large number of proteins involved in diverse functions. Activation of PP2A is dependent on its methylation, which is negatively regulated by the PP2A-specific methylesterase (PME-1). By binding to PME-1, PTPA counteracts the negative influence of the former on PP2A. Pathogenic variants in genes encoding subunits/regulators of the PP2A complex (e.g. PPP2R1A or PPP2CA) are associated with neurodevelopmental disorders. Variant studies: Upon overexpression of wt and both variants in a HEK-293 cell line the authors demonstrated that both variants resulted in significantly reduced mRNA and protein levels (which for Ala171Asp were attributed to increased proteasomal degradation). Both variants were shown to result in impaired PP2A complex activation compared to wt. Drosophila / animal models: Pan-neuronal RNAi-mediated knockdown of ptpa in Drosophila resulted in an age-dependent locomotor dysfunction, reversible with L-DOPA treatment. Previous studies in mice suggest cognitive/electrophysiological impairments upon downregulation of PP2A activity in transgenic mice. Sources: Literature; to: Biallelic PTPA pathogenic variants lead to a form of ID with later-onset parkinsonism based on 4 individuals from 2 families in the literature. Affected individuals were homozygous for missense variants demonstrated to result to reduced mRNA and protein levels as well as PP2A complex activation. Drosophila studies support an age-dependent locomotor dysfunction. Variants in other PP2A-complex-related genes also lead to NDDs. Summary provided below. There is currently no associated phenotype in OMIM, G2P, PanelApp UK or SysID. Consider inclusion in relevant panels (ID, Parkinsonism/movement disorders, etc) with amber rating pending further reports. ------ Fevga, Tesson et al (2022 - PMID: 36073231) describe the features of 4 individuals, from 2 unrelated families, with biallelic pathogenic PTPA variants. These presented with normal or delayed early milestones, learning disability and ID (mild to moderate) followed by progressive signs of parkinsonism (at the age of 11 yrs in 2 sibs, 15 yrs in another individual). Motor symptoms were responsive to levodopa and later to deep brain stimulation. Linkage analysis in one consanguineous family followed by exome revealed homozygosity for a missense PTPA variant (NM_178001:c.893T>G/p.Met298Arg). Exome sequencing in affected subjects from the 2nd family revealed homozygosity for a further missense variant (c.512C>A/p.Ala171Asp). There were no other candidate variants for the phenotype following parental / segregation studies. Role of the gene: As the authors discuss, PTPA (or PPP2R4) is ubiquitously expressed in all tissues incl. brain and encodes a phosphotyrosyl phosphatase activator of the dimeric form of protein phosphatase-2A (PP2A). PP2A in turn, is the major Ser/Thr phosphatase in brain targeting a large number of proteins involved in diverse functions. Activation of PP2A is dependent on its methylation, which is negatively regulated by the PP2A-specific methylesterase (PME-1). By binding to PME-1, PTPA counteracts the negative influence of the former on PP2A. Pathogenic variants in genes encoding subunits/regulators of the PP2A complex (e.g. PPP2R1A or PPP2CA) are associated with neurodevelopmental disorders. Variant studies: Upon overexpression of wt and both variants in a HEK-293 cell line the authors demonstrated that both variants resulted in significantly reduced mRNA and protein levels (which for Ala171Asp were attributed to increased proteasomal degradation). Both variants were shown to result in impaired PP2A complex activation compared to wt. Drosophila / animal models: Pan-neuronal RNAi-mediated knockdown of ptpa in Drosophila resulted in an age-dependent locomotor dysfunction, reversible with L-DOPA treatment. Previous studies in mice suggest cognitive/electrophysiological impairments upon downregulation of PP2A activity in transgenic mice. Sources: Literature |
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| Intellectual disability syndromic and non-syndromic v0.4939 | PTPA |
Konstantinos Varvagiannis gene: PTPA was added gene: PTPA was added to Intellectual disability syndromic and non-syndromic. Sources: Literature Mode of inheritance for gene: PTPA was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: PTPA were set to 36073231 Phenotypes for gene: PTPA were set to Intellectual disability; Parkinsonism Penetrance for gene: PTPA were set to Complete Review for gene: PTPA was set to AMBER Added comment: Biallelic PTPA pathogenic variants lead to a form of ID with later-onset parkinsonism based on 4 individuals from 2 families in the literature. Affected individuals were homozygous for missense variants demonstrated to result to reduced mRNA and protein levels as well as PP2A complex activation. Drosophila studies support an age-dependent locomotor dysfunction. Variants in other PP2A-complex-related genes also lead to NDDs. Summary provided below. There is currently no associated phenotype in OMIM, G2P, PanelApp Australia or SysID. Consider inclusion in relevant panels (ID, Parkinsonism/movement disorders, etc) with amber rating pending further reports. ------ Fevga, Tesson et al (2022 - PMID: 36073231) describe the features of 4 individuals, from 2 unrelated families, with biallelic pathogenic PTPA variants. These presented with normal or delayed early milestones, learning disability and ID (mild to moderate) followed by progressive signs of parkinsonism (at the age of 11 yrs in 2 sibs, 15 yrs in another individual). Motor symptoms were responsive to levodopa and later to deep brain stimulation. Linkage analysis in one consanguineous family followed by exome revealed homozygosity for a missense PTPA variant (NM_178001:c.893T>G/p.Met298Arg). Exome sequencing in affected subjects from the 2nd family revealed homozygosity for a further missense variant (c.512C>A/p.Ala171Asp). There were no other candidate variants for the phenotype following parental / segregation studies. Role of the gene: As the authors discuss, PTPA (or PPP2R4) is ubiquitously expressed in all tissues incl. brain and encodes a phosphotyrosyl phosphatase activator of the dimeric form of protein phosphatase-2A (PP2A). PP2A in turn, is the major Ser/Thr phosphatase in brain targeting a large number of proteins involved in diverse functions. Activation of PP2A is dependent on its methylation, which is negatively regulated by the PP2A-specific methylesterase (PME-1). By binding to PME-1, PTPA counteracts the negative influence of the former on PP2A. Pathogenic variants in genes encoding subunits/regulators of the PP2A complex (e.g. PPP2R1A or PPP2CA) are associated with neurodevelopmental disorders. Variant studies: Upon overexpression of wt and both variants in a HEK-293 cell line the authors demonstrated that both variants resulted in significantly reduced mRNA and protein levels (which for Ala171Asp were attributed to increased proteasomal degradation). Both variants were shown to result in impaired PP2A complex activation compared to wt. Drosophila / animal models: Pan-neuronal RNAi-mediated knockdown of ptpa in Drosophila resulted in an age-dependent locomotor dysfunction, reversible with L-DOPA treatment. Previous studies in mice suggest cognitive/electrophysiological impairments upon downregulation of PP2A activity in transgenic mice. Sources: Literature |
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| Intellectual disability syndromic and non-syndromic v0.4507 | CHKA |
Konstantinos Varvagiannis gene: CHKA was added gene: CHKA was added to Intellectual disability syndromic and non-syndromic. Sources: Literature Mode of inheritance for gene: CHKA was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: CHKA were set to 35202461 Phenotypes for gene: CHKA were set to Abnormal muscle tone; Global developmental delay; Intellectual disability; Seizures; Microcephaly; Abnormality of movement; Abnormality of nervous system morphology; Short stature Penetrance for gene: CHKA were set to Complete Review for gene: CHKA was set to GREEN Added comment: Klöckner (2022 - PMID: 35202461) describe the phenotype of 6 individuals (from 5 unrelated families) harboring biallelic CHKA variants. Shared features incl. abnormal muscle tone(6/6 - hypertonia or hypotonia, 3/6 each), DD/ID (6/6,severe in 4, severe/profound in 2), epilepsy (6/6 - onset: infancy - 3y2m | epileptic spasms or GS at onset), microcephaly (6/6), movement disorders (3/6 - incl. dyskinesia, rigidity, choreoatetotic movements). 2/5 individuals exhibited MRI abnormalities, notably hypomyelination. Short stature was observed in 4/6. Eventual previous genetic testing was not discussed. Exome sequencing (quattro ES for 2 sibs, trio ES for 1 individual, singleton for 3 probands) revealed biallelic CHKA variants in all affected individuals. Sanger sequencing was performed for confirmation and segregation studies. Other variants (in suppl.) were not deemed to be causative for the neurodevelopmental phenotype. 3 different missense, 1 start-loss and 1 truncating variant were identified, namely (NM_0012772.2): - c.421C>T/p.(Arg141Trp) [3 hmz subjects from 2 consanguineous families], - c.580C>T/p.Pro194Ser [1 hmz individual born to consanguineous parents], - c.2T>C/p.(Met1?) [1 hmz individual born to related parents], - c.14dup/p.(Cys6Leufs*19) in trans with c.1021T>C/p.(Phe341Leu) in 1 individual. CHKA encodes choline kinase alpha, an enzyme catalyzing the first step of phospholipid synthesis in the Kennedy pathway. The pathway is involved in de novo synthesis of glycerophospholipids, phosphatidylcholine and phosphatidylethanolamine being the most abundant in eukaryotic membranes. CHKA with its paralog (CHKB) phosphorylates either choline or ethanolamine to phosphocholine or phosphoethanolamine respectively with conversion of ATP to ADP. As the authors comment, biallelic pathogenic variants in CHKB cause a NDD with muscular dystrophy, hypotonia, ID, microcephaly and structural mitochondrial anomalies (MIM 602541). [Prominent mitochondrial patterning was observed in a single muscle biopsy available from an individual with biallelic CHKA variants]. Other disorders of the Kennedy pathway (due to biallelic PCYT2, SELENOI, PCYT1A variants) present with overlapping features incl. variable DD/ID (no-severe), microcephaly, seizures, visual impairment etc. CHKA variants were either absent or observed once in gnomAD, affected highly conserved AAs with multiple in silico predictions in favor of a deleterious effect. In silico modeling suggests structural effects for several of the missense variants (Arg141Trp, Pro194Ser presumably affect ADP binding, Phe341 lying close to the binding site of phosphocholine). Each of the missense variants was expressed in yeast cells and W. Blot suggested expression at the expected molecular weight at comparative levels. The 3 aforementioned variants exhibited reduced catalytic activity (20%, 15%, 50% respectively). NMD is thought to underly the deleterious effect of the frameshift one (not studied). The start-loss variant is expected to result in significantly impaired expression and protein function as eventual utilization of the next possible start codon - occurring at position 123 - would remove 26% of the protein. Chka(-/-) is embryonically lethal in mice, suggesting that complete loss is not compatible with life. Reduction of choline kinase activity by 30% in heterozygous mice did not appear to result in behavioral abnormalities although this was not studied in detail (PMID cited: 18029352). Finally, screening of 1566 mouse lines identified 198 genes whose disruption yields neuroanatomical phenotypes, Chka(+/-) mice being among these (PMID cited: 31371714). There is no associated phenotype in OMIM, Gene2Phenotype or SysID. Overall this gene can be considered for inclusion in the ID and epilepsy panes with green or amber rating (>3 individuals, >3 variants, variant studies, overlapping phenotype of disorders belonging to the same pathway, etc). Consider also inclusion in the microcephaly panel (where available this seemed to be of postnatal onset). Sources: Literature |
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| Intellectual disability syndromic and non-syndromic v0.3062 | SHMT2 |
Konstantinos Varvagiannis gene: SHMT2 was added gene: SHMT2 was added to Intellectual disability syndromic and non-syndromic. Sources: Literature Mode of inheritance for gene: SHMT2 was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: SHMT2 were set to 33015733 Phenotypes for gene: SHMT2 were set to Congenital microcephaly; Infantile axial hypotonia; Spastic paraparesis; Global developmental delay; Intellectual disability; Abnormality of the corpus callosum; Abnormal cortical gyration; Hypertrophic cardiomyopathy; Abnormality of the face; Proximal placement of thumb; 2-3 toe syndactyly Penetrance for gene: SHMT2 were set to Complete Review for gene: SHMT2 was set to GREEN Added comment: García‑Cazorla et al. (2020 - PMID: 33015733) report 5 individuals (from 4 families) with a novel brain and heart developmental syndrome caused by biallelic SHMT2 pathogenic variants. All affected subjects presented similar phenotype incl. microcephaly at birth (5/5 with OFC < -2 SD though in 2/5 cases N OFC was observed later), DD and ID (1/5 mild-moderate, 1/5 moderate, 3/5 severe), motor dysfunction in the form of spastic (5/5) paraparesis, ataxia/dysmetria (3/4), intention tremor (in 3/?) and/or peripheral neuropathy (2 sibs). They exhibited corpus callosum hypoplasia (5/5) and perisylvian microgyria-like pattern (4/5). Cardiac problems were reported in all, with hypertrophic cardiomyopathy in 4/5 (from 3 families) and atrial-SD in the 5th individual (1/5). Common dysmorphic features incl. long palpebral/fissures, eversion of lateral third of lower eylids, arched eyebrows, long eyelashes, thin upper lip, short Vth finger, fetal pads, mild 2-3 toe syndactyly, proximally placed thumbs. Biallelic variants were identified following exome sequencing in all (other investigations not mentioned). Identified variants were in all cases missense SNVs or in-frame del, which together with evidence from population databases and mouse model might suggest a hypomorphic effect of variants and intolerance/embryonic lethality for homozygous LoF ones. SHMT2 encodes the mitohondrial form of serine hydroxymethyltransferase. The enzyme transfers one-carbon units from serine to tetrahydrofolate (THF) and generates glycine and 5,10,methylene-THF. Mitochondrial defect was suggested by presence of ragged red fibers in myocardial biopsy of one patient. Quadriceps and myocardial biopsies of the same individual were overall suggestive of myopathic changes. While plasma metabolites were within N range and SHMT2 protein levels not significantly altered in patient fibroblasts, the authors provide evidence for impaired enzymatic function eg. presence of the SHMT2 substrate (THF) in patient but not control (mitochondria-enriched) fibroblasts , decrease in glycine/serine ratios, impared folate metabolism. Patient fibroblasts displayed impaired oxidative capacity (reduced ATP levels in a medium without glucose, diminished oxygen consumption rates). Mitochondrial membrane potential and ROS levels were also suggestive of redox malfunction. Shmt2 ko in mice was previously shown to be embryonically lethal attributed to severe mitochondrial respiration defects, although there was no observed brain metabolic defect. The authors performed Shmt2 knockdown in motoneurons in Drosophila, demonstrating neuromuscular junction (# of satellite boutons) and motility defects (climbing distance/velocity). Overall this gene can be considered for inclusion with (probably) green rating in gene panels for ID, metabolic / mitochondrial disorders, cardiomyopathy, congenital microcephaly, corpus callosum anomalies, etc. Sources: Literature |
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| Intellectual disability syndromic and non-syndromic v0.1260 | TTR | Zornitza Stark Marked gene: TTR as ready | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability syndromic and non-syndromic v0.1260 | TTR | Zornitza Stark Gene: ttr has been classified as Red List (Low Evidence). | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability syndromic and non-syndromic v0.519 | TTR | Chirag Patel Classified gene: TTR as Red List (low evidence) | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability syndromic and non-syndromic v0.519 | TTR | Chirag Patel Gene: ttr has been classified as Red List (Low Evidence). | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability syndromic and non-syndromic v0.518 | TTR |
Chirag Patel Source Genetic Health Queensland was removed from TTR. Source Expert list was added to TTR. Mode of inheritance for gene TTR was changed from Unknown to MONOALLELIC, autosomal or pseudoautosomal, NOT imprinted Phenotypes for gene: TTR were changed from to Amyloidosis, hereditary, transthyretin-related, OMIM #105210; Carpal tunnel syndrome, familial; OMIM #115430 |
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| Intellectual disability syndromic and non-syndromic v0.517 | TTR | Chirag Patel reviewed gene: TTR: Rating: RED; Mode of pathogenicity: None; Publications: ; Phenotypes: Amyloidosis, hereditary, transthyretin-related, OMIM #105210, Carpal tunnel syndrome, familial, OMIM #115430; Mode of inheritance: MONOALLELIC, autosomal or pseudoautosomal, NOT imprinted | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability syndromic and non-syndromic v0.0 | TTR |
Zornitza Stark gene: TTR was added gene: TTR was added to Intellectual disability, syndromic and non-syndromic_GHQ. Sources: Expert Review Green,Genetic Health Queensland Mode of inheritance for gene: TTR was set to Unknown |
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