Centronuclear myopathies (CNM) are congenital disorders associated with muscle weakness and abnormally located nuclei in skeletal muscle. An autosomal dominant form of CNM results from mutations in the gene encoding dynamin 2 (DNM2), and loss-of-function mutations in the gene encoding myotubularin (MTM1) result in X-linked CNM (XLCNM, also called myotubular myopathy), which promotes severe neonatal hypotonia and early death. Currently, no effective treatments exist for XLCNM. Here, we found increased DNM2 levels in XLCNM patients and a mouse model of XLCNM (Mtm1 -/y ). Generation of Mtm1 -/y mice that were heterozygous for Dnm2 revealed that reduction of DNM2 in XLCNM mice restored life span, whole-body strength, and diaphragm function and increased muscle strength. Additionally, classic CNM-associated histological features, including fiber atrophy and nuclei mispositioning, were absent or reduced. Ultrastructural analysis revealed improvement of sarcomere organization and triad structures. Skeletal muscle-specific decrease of Dnm2 during embryogenesis or in young mice after disease onset revealed that the rescue associated with downregulation of Dnm2 is cell autonomous and is able to stop and potentially revert XLCNM progression. These data indicate that MTM1 and DNM2 regulate muscle organization and force through a common pathway. Furthermore, despite DNM2 being a key mechanoenzyme, its reduction is beneficial for XLCNM and represents a potential therapeutic approach for patients.

Amphiphysin 2, also named bridging integrator-1 (BIN1) or SH3P9, has been recently implicated in rare and common diseases affecting different tissues and physiological functions. BIN1 downregulation is linked to cancer progression and also correlates with ventricular cardiomyopathy and arrhythmia preceding heart failure. Increased BIN1 expression is linked to increased susceptibility for late-onset Alzheimer's disease. In addition, altered splicing may account for the muscle component of myotonic dystrophies, while recessive germinal mutations cause centronuclear myopathy. Despite undoubtedly underlining the relevance of BIN1 in human diseases, the molecular and cellular bases leading to such different diseases are unclear at present. BIN1 is a key regulator of endocytosis and membrane recycling, cytoskeleton regulation, DNA repair, cell cycle progression, and apoptosis. In light of the recent findings on the molecular, cellular, and physiological roles of BIN1, we discuss potential pathological mechanisms and highlight common disease pathways and also tissue-specific regulation. Next challenges will be to validate BIN1 both as a prognostic marker for the related diseases and as a potential therapeutic target.