Myotubularin 1 (MTM1) (MTM1)

Myotubularin 1 (MTM1) is a highly conserved phosphoinositide 3-phosphatase that plays a critical role in the regulation of endosomal trafficking and the maintenance of skeletal muscle architecture [1, 4]. It acts by dephosphorylating the signaling lipids phosphatidylinositol 3-phosphate (PI3P) and phosphatidylinositol 3,5-bisphosphate (PI(3,5)P2) at the D3 position [1, 8]. Loss-of-function mutations in the MTM1 gene cause X-linked myotubular myopathy (XLMTM), a severe congenital myopathy characterized by profound muscle weakness, hypotonia, and respiratory insufficiency often resulting in early death [10, 14]. The protein is also involved in the assembly of intermediate filaments and the regulation of mitochondrial positioning within muscle fibers [1, 6]. In the therapeutic landscape, MTM1 is a primary target for gene replacement therapy, most notably with Resamirigene bilaparvovec (AT132), which utilizes an adeno-associated virus (AAV8) vector to restore functional protein expression [11, 13]. Clinical development of such therapies has encountered significant challenges, including severe hepatotoxicity and treatment-related deaths, highlighting the complexity of targeting this pathway [5, 16]. Ongoing research also explores the inhibition of antagonistic lipid kinases, such as PI3KC2β, to compensate for the lack of MTM1 activity [16].

Other names

MTMCNMCNMXMTMXXLMTMPhosphatidylinositol-3-phosphatase myotubularin 1

Gene replacement therapy utilizing an adeno-associated virus (AAV8) vector to deliver a functional copy of the MTM1 gene, thereby restoring myotubularin 1 protein expression and catalytic activity in skeletal muscle cells [11, 13].