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| Fetal anomalies v0.2748 | SHMT2 | Zornitza Stark Marked gene: SHMT2 as ready | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Fetal anomalies v0.2748 | SHMT2 | Zornitza Stark Gene: shmt2 has been classified as Green List (High Evidence). | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Fetal anomalies v0.2748 | SHMT2 | Zornitza Stark Classified gene: SHMT2 as Green List (high evidence) | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Fetal anomalies v0.2748 | SHMT2 | Zornitza Stark Gene: shmt2 has been classified as Green List (High Evidence). | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Fetal anomalies v0.2728 | SHMT2 |
Krithika Murali gene: SHMT2 was added gene: SHMT2 was added to Fetal anomalies. 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 Polymicrogyria; corpus callosum anomalies; Microcephaly; Neurodevelopmental disorder with cardiomyopathy, spasticity, and brain abnormalities - #619121 Review for gene: SHMT2 was set to GREEN Added comment: Neurodevelopmental disorder with cardiomyopathy, spasticity, and brain abnormalities particularly thin corpus callosum and polymicrogyria (NEDCASB) associated with biallelic SHMT2 variants. Antenatal detection of microcephaly reported. -- Detailed PanelApp review Oct 2020 - no new evidence to add 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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