Other studies looking at tissue samples reported mtDNA depletion in skeletal muscle from a patient exhibiting early-onset CMT2A who harbored the D210Y MFN2 variant (Renaldo et al., 2012), while a two-fold decrease in the mtDNA copy number was observed in tissue samples from three patients carrying the MFN2 variants M376V, R707P or V226_S229 (Vielhaber et al., 2013). This evidence concerns the gene MFN2 and Charcot-Marie-Tooth disease type 2A1.