MTM1

Myotubularin 1 (MTM1), a phosphatidylinositol 3-phosphate (PI3P) and phosphatidylinositol 3,5-bisphosphate [PI(3,5)P2] phosphatase, is a ubiquitously expressed enzyme encoded by the MTM1 gene. Also termed myotubular myopathy-associated phosphatase, it regulates endosomal trafficking and lysosomal function by hydrolyzing phosphoinositide signaling lipids. MTM1 operates within the PI3K/AKT/mTOR pathway, modulating autophagy, membrane remodeling, and neuromuscular junction maintenance. Mutations in MTM1 cause X-linked myotubular myopathy (XLMTM), a fatal congenital disorder characterized by severe hypotonia, respiratory insufficiency, and skeletal muscle pathology. Therapeutic strategies include AAV-mediated gene replacement therapy (e.g., AT132 by Astellas, currently in Phase 2/3 trials), small-molecule phosphatase activators, and antisense oligonucleotides targeting aberrant splicing. Recent preclinical studies highlight MTM1's cross-talk with DNM2 and BIN1, suggesting combinatorial therapies. Drug development faces challenges due to hepatotoxicity risks observed in early trials, driving innovations in tissue-specific vectors and dose optimization.