Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0026827 (hypotonia)
 5,860 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Myotubular myopathy (MTM1) is an X-linked disease, characterized by severe neonatal hypotonia and generalized muscle weakness, with pathological features suggesting an impairment in maturation of muscle fibres. The MTM1 gene encodes a protein (myotubularin) with a phosphotyrosine phosphatase consensus. It defines a family of at least nine genes in man, including the antiphosphatase hMTMR5/Sbf1 and hMTMR2, recently found mutated in a recessive form of Charcot-Marie-Tooth disease. Myotubularin shows a dual specificity protein phosphatase activity in vitro. We have performed an in vivo test of tyrosine phosphatase activity in Schizosaccharomyces pombe, indicating that myotubularin does not have a broad specificity tyrosine phosphatase activity. Expression of active human myotubularin inhibited growth of S.pombe and induced a vacuolar phenotype similar to that of mutants of the vacuolar protein sorting (VPS) pathway and notably of mutants of VPS34, a phosphatidylinositol 3-kinase (PI3K). In S.pombe cells deleted for the endogenous MTM homologous gene, expression of human myotubularin decreased the level of phosphatidylinositol 3-phosphate (PI3P). We have created a substrate trap mutant which shows relocalization to plasma membrane projections (spikes) in HeLa cells and was inactive in the S.pombe assay. This mutant, but not the wild-type or a phosphatase site mutant, was able to immunoprecipitate a VPS34 kinase activity. Wild-type myotubularin was also able to directly dephosphorylate PI3P and PI4P in vitro. Myotubularin may thus decrease PI3P levels by down-regulating PI3K activity and by directly degrading PI3P.
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PMID:Myotubularin, a phosphatase deficient in myotubular myopathy, acts on phosphatidylinositol 3-kinase and phosphatidylinositol 3-phosphate pathway. 1100 25

The sortilin-related VPS10 domain-containing receptor 3 (SORCS3) is a type-I receptor transmembrane protein and a member of the vacuolar protein sorting 10 receptor family. Proteins of this family are defined to have a vacuolar protein sorting 10 domain at the N-terminus. They play important roles as a sorting agency within the cells and transport a variety of intracellular proteins between the Golgi apparatus, endosome, lysosome, secretory granules, and plasma membrane. They are also involved in signal transduction. Clinically, they have been implicated in the pathophysiology of multiple sclerosis and Alzheimer's disease. Here, we report details on two brothers deceased at 20 months and 2 years of age, respectively, with a neurological phenotype including infantile spasms, intellectual disability, global developmental delay, microcephaly, hypotonia, spastic quadriplegia, and delayed myelination. Whole exome sequencing and autozygome analysis showed homozygous missense variant in the SORCS3 gene. The pathogenicity is supported by functional studies in the patient mesenchymal stem cells. Patients' cells showed less proliferation capability than normal cells. In addition, making the same mutation in normal cells revealed a viability defect in them. This is the first study on human subjects with a SORCS3 gene defect and supports the important role of SORCS3 in the central nervous system.
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PMID:The SORCS3 gene is mutated in brothers with infantile spasms and intellectual disability. 3058 38