Gene therapy in myotubular myopathy: promising progress and future directions

X-linked myotubular myopathy (MTM; OMIM 310400) is a severe congenital myopathy that is classified as one of the centronuclear myopathies (1). MTM is estimated to affect 1/50,000 live born males and is due to loss of function mutations in MTM1, which encodes myotubularin, a ubiquitously expressed lipid phosphatase (2,3). The function of myotubularin is still not entirely clear, but a picture is starting to emerge in which myotubularin is a critical maintenance protein of the myofiber sarcotubular system and has a role in excitation-contraction coupling (4-7).