Myotubularins and associated neuromuscular diseases

The myotubularins are a family of phosphoinositide 3-phosphatases preferentially hydrolyzing phosphatidylinositol 3-monophosphate and also phosphatidylinositol (3,5) bis-phosphate, thus generating phosphatidylinositol and phosphatidylinositol 5-monophosphate, respectively. These phosphoinositides are known regulators of vesicular trafficking and phosphatidylinositol 5-monophosphate was also implicated in signal transduction regulation. Based on their capacity to control the level of these phosphoinositides, myotubularins are involved in the regulation of vesicular trafficking, membrane homeostasis, cytoskeleton dynamics, proliferation and apoptosis. Myotubularin dysfunctions are linked to genetic diseases: MTMI is mutated in the X-linked congenital myotubular myopathy and MTMR2 and MTMR13 are mutated in autosomal recessive type 4B1 and 4B2 Charcot-Marie-Tooth neuropathies, respectively. This review presents the cellular functions of myotubularins and highlights their physiopathological roles in neuromuscular diseases.