Dynamin 2 mutations in Charcot-Marie-Tooth neuropathy highlight the importance of clathrin-mediated endocytosis in myelination

Mutations in dynamin 2 ( DNM2 ) lead to dominant intermediate Charcot–Marie–Tooth neuropathy type B, while a different set of DNM2 mutations cause autosomal dominant centronuclear myopathy. In this study, we aimed to elucidate the disease mechanisms in dominant intermediate Charcot–Marie–Tooth neuropathy type B and to find explanations for the tissue-specific defects that are associated with different DNM2 mutations in dominant intermediate Charcot–Marie–Tooth neuropathy type B versus autosomal dominant centronuclear myopathy. We used tissue derived from Dnm2 -deficient mice to establish an appropriate peripheral nerve model and found that dominant intermediate Charcot–Marie–Tooth neuropathy type B-associated dynamin 2 mutants, but not autosomal dominant centronuclear myopathy mutants, impaired myelination. In contrast to autosomal dominant centronuclear myopathy mutants, Schwann cells and neurons from the peripheral nervous system expressing dominant intermediate Charcot–Marie–Tooth neuropathy mutants showed defects in clathrin-mediated endocytosis. We demonstrate that, as a consequence, protein surface levels are altered in Schwann cells. Furthermore, we discovered that myelination is strictly dependent on Dnm2 and clathrin-mediated endocytosis function. Thus, we propose that altered endocytosis is a major contributing factor to the disease mechanisms in dominant intermediate Charcot–Marie–Tooth neuropathy type B. * Abbreviations : CMT : Charcot–Marie–Tooth CNM : centronuclear myopathy EGFP : enhanced green fluorescent protein