In contrast to mitofusins, overexpression of ganglioside-induced differentiation associated protein 1 (GDAP1) is interfering with mitochondrial fusion and induces fragmentation of mitochondria, and recessive mutations in GDAP1 have been found in patients with CMT4A [14,15]. The gene discussed is GDAP1; the disease is Charcot-Marie-Tooth disease type 4A.