MFN2 and Charcot-Marie-Tooth disease: From these results, not only impaired mitochondrial fusion but also excessive fusion of mitochondria may underlie CMT caused by mutant MFN2, and the diversity of the mutation site in the MFN2 gene and various functional alterations of MFN2 protein caused by each MFN2 mutation may lead to the marked individual differences noted in CMT2A patients.