Myotubularin

Myotubularin (MTM1) is a lipid phosphatase that dephosphorylates phosphatidylinositol 3-monophosphate and phosphatidylinositol 3,5-bisphosphate, regulating endosomal trafficking and EGFR degradation (UniProt: Q13496). The protein also influences vacuolar morphology, desmin intermediate filament assembly, and mitochondrial architecture, and is essential for skeletal muscle maintenance.

Mutations in MTM1 cause X-linked centronuclear myopathy (CNMX, MIM 310400), a congenital disorder featuring progressive muscle weakness and centrally located nuclei in muscle fibers (UniProt: Q13496). MTM1 stabilizes MTMR12 protein levels in skeletal muscle and has pleiotropic roles in cytoskeletal and organellar homeostasis.

In Alzheimer's disease, MTM1 is significantly down-regulated in post-mortem AD brain tissue compared to age-matched controls (mean log2FC −0.484; Chaparral AD proteomics), based on TMT-labeled mass spectrometry analysis of four subcellular fractions. The functional significance of reduced myotubularin in AD pathology remains to be clarified, though impaired phospholipid metabolism and endosomal dysfunction are emerging themes in neurodegeneration.