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| Mendeliome v1.2168 | PPP2R2B | Bryony Thompson edited their review of gene: PPP2R2B: Added comment: 5 cases with NDD and heterozygous missense (4/5 confirmed de novo): p.Thr246Lys (unknown inheritance), p.Asn310Lys (confirmed de novo), p.Glu37Lys (confirmed de novo, also had RNU4-2 path de novo Path variant), p.Ile427Thr (confirmed de novo, also had TAOK1 inherited Path variant), p.Arg149Pro (confirmed de novo). 5/5 with intellectual disability and developmental delay, 4/5 with seizures, 2/5 with hearing loss/auditory neuropathy. Study includes in vitro functional assays supporting a possible loss of function mechanism of disease. The 2 missense with additional diagnoses (E37K & I427T) demonstrated a partial reduction in PP2A holoenzyme assembly. Only 3 cases with a possible diagnosis that could be attributed to the PPP2R2B only, and only 2 were confirmed de novo.; Changed rating: AMBER; Changed publications: 25356899, 39565297; Changed phenotypes: Neurodevelopmental disorder MONDO:0700092 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mendeliome v1.1633 | USP14 |
Zornitza Stark gene: USP14 was added gene: USP14 was added to Mendeliome. 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 GREEN Added comment: 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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| Mendeliome v1.1526 | TTR | Zornitza Stark Tag treatable tag was added to gene: TTR. | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mendeliome v1.332 | PTPA |
Zornitza Stark gene: PTPA was added gene: PTPA was added to Mendeliome. 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, MONDO: 36073231, PTPA-related 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 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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| Mendeliome v0.14223 | FXN | Bryony Thompson edited their review of gene: FXN: Added comment: Well-established gene-disease association. 96% of cases are caused by biallelic intronic GAA triplet repeat expansion and 4% are attributable to biallelic single nucleotide variants and small indels. Loss of function is the mechanism of disease.; Changed rating: GREEN; Changed publications: 20301458, 26704351; Changed phenotypes: Friedreich ataxia MONDO:0100339; Changed mode of inheritance: BIALLELIC, autosomal or pseudoautosomal; Set current diagnostic: yes | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mendeliome v0.12343 | TTR | Zornitza Stark Marked gene: TTR as ready | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mendeliome v0.12343 | TTR | Zornitza Stark Gene: ttr has been classified as Green List (High Evidence). | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mendeliome v0.12343 | TTR | Zornitza Stark Phenotypes for gene: TTR were changed from to Amyloidosis, hereditary, transthyretin-related, MIM #105210; Carpal tunnel syndrome, familial, MIM# 115430 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mendeliome v0.12342 | TTR | Zornitza Stark Publications for gene: TTR were set to | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mendeliome v0.12341 | TTR | Zornitza Stark Mode of inheritance for gene: TTR was changed from Unknown to MONOALLELIC, autosomal or pseudoautosomal, NOT imprinted | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mendeliome v0.12323 | TTR | Manny Jacobs reviewed gene: TTR: Rating: GREEN; Mode of pathogenicity: Other; Publications: PMID:1570831, 1626570, 16115295, 16194874, 26537620; Phenotypes: Amyloidosis, hereditary, transthyretin-related, MIM #105210, Carpal tunnel syndrome, familial, MIM# 115430; Mode of inheritance: MONOALLELIC, autosomal or pseudoautosomal, NOT imprinted | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mendeliome v0.11163 | JAG1 |
Zornitza Stark changed review comment from: Two unrelated families reported with CMT type 2. Affected individuals in both families exhibited severe vocal fold paresis, a rare feature of peripheral nerve disease that can be life-threatening. Studies of mutant protein posttranslational modification and localization indicated that the mutations (p.Ser577Arg, p.Ser650Pro) impair protein glycosylation and reduce JAG1 cell surface expression. Mice harboring heterozygous CMT2-associated mutations exhibited mild peripheral neuropathy, and homozygous expression resulted in embryonic lethality by midgestation. Pre-existing rat model. Sources: Literature; to: Association with Alagille is very well established. Two unrelated families reported with CMT type 2. Affected individuals in both families exhibited severe vocal fold paresis, a rare feature of peripheral nerve disease that can be life-threatening. Studies of mutant protein posttranslational modification and localization indicated that the mutations (p.Ser577Arg, p.Ser650Pro) impair protein glycosylation and reduce JAG1 cell surface expression. Mice harboring heterozygous CMT2-associated mutations exhibited mild peripheral neuropathy, and homozygous expression resulted in embryonic lethality by midgestation. Pre-existing rat model. Sources: Literature |
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| Mendeliome v0.11071 | CHKA |
Konstantinos Varvagiannis gene: CHKA was added gene: CHKA was added to Mendeliome. 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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| Mendeliome v0.10087 | HELQ | Bryony Thompson commented on gene: HELQ: A single POI heterozygous for a frameshift variant (c.3095delA;p.Tyr1032Serfs*4), and a null mouse model (both homozygous and heterozygous) with subfertility and germ cell attrition. | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mendeliome v0.8487 | COL25A1 |
Zornitza Stark edited their review of gene: COL25A1: Added comment: PMID: 2643702 - Patient: 273182 reported in DECIPHER, chet COL25A1 missense variants (listed as Likely Pathogenic). Phenotype includes Duane anomaly of the eye. PMID: 31875546 - Mouse models, including Col25a1 KO and muscle-specific KO mice showed a significant reduction in the number of motor neurons in the cranial nerve nuclei, including the oculomotor, trochlear, trigeminal, and facial motor nuclei. Abnormalities in motor innervation of muscles of the head, such as the extraocular and masseter muscles, were also observed PMID: 31875546 - Functional studies in human cell lines showed that the reported COL25A1 variants (G382R and G497X) impaired the interaction of COL25A1 with receptor protein tyrosine phosphatases, thereby reducing the ability to attract motor axons.; Changed rating: GREEN; Changed publications: 25500261, 26486031, 31875546, 26437029 |
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| Mendeliome v0.6164 | MYADML2 |
Paul De Fazio gene: MYADML2 was added gene: MYADML2 was added to Mendeliome. Sources: Literature Mode of inheritance for gene: MYADML2 was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: MYADML2 were set to 32778762 Phenotypes for gene: MYADML2 were set to Cranial asymmetry, reduced bone maturation, multiple dislocations, lumbar lordosis, and prominent clavicles Review for gene: MYADML2 was set to RED gene: MYADML2 was marked as current diagnostic Added comment: 5 sibs from a consanguineous family identified to have biallelic deletion encompassing part of the PYCR1 gene and the coding region of the MYADML2 gene. According to the authors: "All five affected sibs had the most common features of ARCL (autosomal recessive cutis laxa) but not many of the less common ones. We attributed the anomalies not typical for ARCL to MYADML2 deficit, because no other genetic defect possibly a candidate to underlie the skeletal phenotype was found." Phenotype may still be explained by the PYCR1 deletion alone. Sources: Literature |
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| Mendeliome v0.5500 | KCNJ18 |
Zornitza Stark gene: KCNJ18 was added gene: KCNJ18 was added to Mendeliome. Sources: Expert Review Mode of inheritance for gene: KCNJ18 was set to MONOALLELIC, autosomal or pseudoautosomal, NOT imprinted Publications for gene: KCNJ18 were set to 20074522; 27008341 Phenotypes for gene: KCNJ18 were set to {Thyrotoxic periodic paralysis, susceptibility to, 2}, MIM# 613239 Review for gene: KCNJ18 was set to RED Added comment: Six variants reported in original publication, however note lack of segregation data and limited functional data. Subsequently, concerns raised about high nucleotide sequence homology between multiple potassium channel genes, with variant misattribution. Sources: Expert Review |
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| Mendeliome v0.4872 | SHMT2 |
Zornitza Stark gene: SHMT2 was added gene: SHMT2 was added to Mendeliome. 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 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). Sources: Literature |
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| Mendeliome v0.4520 | SLC12A2 |
Zornitza Stark edited their review of gene: SLC12A2: Added comment: Monoallelic : DD/ID was a feature in >= 6 individuals with monoallelic de novo SLC12A2. An individual with an exon 22 truncating variant was reported to have normal milestones and cognitive function. Exon 21 variants have been described in individuals with rather isolated hearing impairment (possibly some associated motor delay, but normal cognition). Hearing impairment was also reported in 2/6 patients with variants in other exons (1 missense / 1 frameshift). Biallelic : DD/ID was reported in at least 3 individuals in literature. Hearing impairment has been reported on 2 occasions (although this was not probably evaluated in all subjects). --- Monoallelic SLC12A2 mutations : ► Individuals with de novo mutations and developmental disorder were first identified by the DDD study (2017 - PMID: 28135719). 5 of them have been reported in detail by McNeill et al (below). ► McNeill et al (2020 - PMID: 32658972) report on 6 individuals with neurodevelopmental disorder due to de novo SLC12A2 mutation. All presented DD or ID ranging from mild to severe. ASD was reported in 3/6. Sensorineural hearing loss was a feature in 2/6 with the remaining having normal formal evaluations. Brain, cardiac and/or additional malformations were reported in a single individual. Following non-diagnostic prior work-up (CMA, FMR1 or other investigations) trio exome sequencing revealed missense (4/6) or truncating variants (2/6). Three additional individuals (incl. a father and his son) with missense variants in exon 21 (NM_001046.3 / p.Glu979Lys and p.Glu980Lys) presented with bilateral sensorineural hearing loss. Speech and/or motor delay reported in these cases were attributed to the hearing impairment/vestibular arreflexia (cognitive abilities not tested). SLC12A2 encodes sodium-potassium-chloride transporter 1 (also NKCC1). The GTEx project has identified 8 isoforms. In brain both exon 21-containing/deleted isoforms are expressed (cited Morita et al 2014 - PMID: 24695712). As the authors discuss, RNA-seq of the developing mouse cochlea suggests that the exon 21 containing isoform is the single transcript expressed. Evidence from RNA-seq data (BrainSpan project) and literature suggests that the significant amounts of exon 21 lacking isoforms in fetal brain compensate for the deleterious effects of exon 21 variants and explain the lack of NDD in relevant patients. Slc12a2 (NKCC1) null mouse model has demonstrated that the transporter plays a role in accumulation of the potassium rich endolymph in the inner ear, with NKCC1 absence causing sensorineural deafness and imbalance. Slc12a2 display cochlear malformations, loss of hair cells and hearing impairment (cited Delpire et al 1999 - PMID: 10369265). The brain phenotype has not been studied extensively, although loss of Slc12a2 has been shown to inhibit neurogenesis (cited: Magalhães and Rivera et al. - PMID: 27582690). Slc12a2 null zebrafish display a collapse of the otic vesicle and reduced endolymph (Abbas and Whitfield, 2009 - PMID: 19633174) relevant to the human hearing disorder. In vitro assessment of NKCC1 ion transporter function in Xenopus laevis, supported the deleterious effect of the identified variants (significant reduction in K+ influx). Using available single cell RNA-seq data the authors further demonstrated that SLC12A2 expressing cells display transcriptomic profiles reflective of active neurogenesis. ► Delpire et al (2016 - PMID: 27900370 - not reviewed in detail) described a 13 y.o. girl harboring a de novo 11-bp deletion in SLC12A2 exon 22. This individual reached developmental milestones on time and had a NORMAL cognitive function. Hearing was seemingly normal. Features included orthostatic intolerance, respiratory weakness, multiple endocrine abnormalities, pancreatic insufficiency and multiorgan failure incl. gut and bladder. Exome in the proband, parents and 3 unaffected sibs suggested SLC12A2 as the only candidate for her phenotype. Functional analyses in Xenopus laevis oocytes suggested that a non functional transporter was expressed and trafficked to the membrane as the wt. Detection of the truncated protein at higher molecular sizes suggested either enhanced dimerization or misfolded aggregate. There was no dominant-negative effect of mutant NKCC1. In patient fibroblasts a reduced total and NKCC1-mediated K+ influx. ► Mutai et al (2020 - PMID: 32294086) report on several individuals from 4 families, harboring variants within exon 21 or - in one case - at it's 3' splice-site (leading to skipping oe this exon at the mRNA level). All subjects were investigated for severe/profound hearing loss (in line with the role of exon 21-included isoforms in cochlea. The variant segregated with hearing impairment in 3 generations of a family while in all other subjects the variant had occured as de novo event. Despite motor delays (e.g. the subject from fam2 could not hold head or sit at the age of 10m / the proband in Fam3 was able to hold his head and walk at 6 and 20 m respectively) behavior and cognition were commented to be within normal range. ----- Biallelic SLC12A2 mutations: ► Anazi et al (2017 - PMID: 29288388) briefly reported on a 3 y.o. boy (17DG0776) with central hypotonia, neonatal respiratory distress, failure to thrive, global DD and microcephaly and a skeletal survey suggestive of osteopenia. After non-diagnostic prior investigations (CMA revealing a 1p duplication classified as VUS, extensive metabolic workup), WES revealed a homozygous SLC12A2 splicing variant [NM_001046.2:c.2617-2A>G]. ► Macnamara et al (2019 - PMID: 30740830) described a 5.5 y.o. male with sensorineural hearing loss, profound delays in all developmental areas among several other features (choanal atresia, failure to thrive, respiratory problems, absent sweat and tear production or salivation, GI abnormalities). Genetic testing for several disorders considered (cystic fibrosis, spinal muscular atrophy, sequencing and del/dup analysis of mtDNA) was normal. CMA revealed paternal uniparental isodisomy for chr. 5 and WGS a homozygous 22kb deletion in SLC12A2. This was followed by confirmation of homozygosity in the proband, heterozygosity of the unaffected father, delineation of breakpoints (chr5:127441491-127471419). mRNA studies in patient fibroblasts confirmed deletion of ex2-7, splicing of ex1 directly to ex8 and introduction of a premature stop codon in ex9. qRT-PCR confirmed that mRNA is likely subjected to NMD (expression ~80% of control). Western blot confirmed absence of the protein in the patient's fibroblasts. Again mouse models are thought to recapitulate the hearing defect but also the deficient saliva production (cited Evans et al 2000 - PMID: 10831596). Again the authors speculate a role of SLC12A2 in brain development based on evidence from murine models (migration, dendritic growth, increse in neuron density through regulation of GABAergic signalling (Young et al 2012 - PMID: 23015452). Hypotheses are also made on a regulatory relationship between NKCC1 and CFTR based on mRNA data from the ko mouse model. ► Stödberg et al (2020 - PMID: 32754646) reported 2 sibs with a complex neurodevelopmental disorder due to compound heterozygosity for a frameshift SLC12A2 variant and a splicing one (NM_001046:c.1431delT and c.2006-1G>A). Both presented hypotonia, neonatal S. aureus parotitis and respiratory problems (incl. apneas). While the older sib died at the age of 22 days, the younger one had persistent respiratory issues incl. a dry respiratory mucosa motivating metabolic, immunology investigations and testing for CF. She displayed microcephaly (OFC -2.5 SD, H was also -3.5SD), severe intellectual disability. MRI was suggestive of white matter and basal ganglia abnormalities. Other features incl. hearing impairment, and lack of tears,saliva and sweat, constipation and intestinal malrotation. There was facial dysmorphism. The variants were the only retained following WGS of the 2 affected sisters, parents and an unaffected brother. The splicing variant was shown to result in skipping of exon 13, while the indel in NMD. Again the authors discuss that the deficient saliva production, impaired hearing and GI problems are recapitulated in the mouse model (several refs provided).; Changed rating: GREEN; Changed publications: 28135719, 32658972, 27900370, 32294086, 29288388, 30740830, 32754646; Changed phenotypes: Kilquist syndrome, deafness, intellectual disability, dysmorphic features, absent salivation, ectodermal dysplasia, constipation, intestinal malrotation, multiple congenital anomalies; Changed mode of inheritance: BOTH monoallelic and biallelic, autosomal or pseudoautosomal |
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| Mendeliome v0.3075 | SV2B |
Seb Lunke gene: SV2B was added gene: SV2B was added to Mendeliome. Sources: Literature Mode of inheritance for gene: SV2B was set to Unknown Publications for gene: SV2B were set to 23617838; 23937191 Phenotypes for gene: SV2B were set to seizures Review for gene: SV2B was set to RED Added comment: Multiply described in Epilepsy studies investigating role of SV2 gene family, however no patients directly attributed to variants in this gene and mouse models indicate viability without seizures. Sources: Literature Sources: Literature |
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| Mendeliome v0.780 | SLC9A7 |
Zornitza Stark gene: SLC9A7 was added gene: SLC9A7 was added to Mendeliome_VCGS. Sources: Literature Mode of inheritance for gene: SLC9A7 was set to X-LINKED: hemizygous mutation in males, biallelic mutations in females Publications for gene: SLC9A7 were set to 30335141 Phenotypes for gene: SLC9A7 were set to Intellectual developmental disorder, X-linked 108; OMIM #301024 Review for gene: SLC9A7 was set to AMBER Added comment: 6 males from 2 unrelated families with hemizygous missense mutation in the SLC9A7 gene. The mutation segregated with the disorder in the family. In vitro functional expression studies in CHO cells (AP-1 cells) showed that the mutation caused decreased levels of protein expression and reduced oligosaccharide maturation/glycosylation compared to wildtype, indicating impaired posttranslational processing. Subcellular localization studies indicated that protein trafficking was unaffected by the mutation. However, examination of the trans-Golgi compartment suggested a gain-of-function effect and a perturbation of glycosylation of secretory cargo. Serum transferrin studies in 1 patient suggested a glycosylation defect. Sources: Literature |
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| Mendeliome v0.0 | TTR |
Zornitza Stark gene: TTR was added gene: TTR was added to Mendeliome_VCGS. Sources: Expert Review Green,Victorian Clinical Genetics Services Mode of inheritance for gene: TTR was set to Unknown |
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