Loss of or mutation in neuropilin-1 (NRP1), the voltage-gated sodium channel NaV1.6 (SCN8A) or neuronal cell adhesion molecule (NRCAM) are linked to disease severity in CMT4C–which is mediated by mutation in the glycyl-tRNA synthetase (GARS) gene (58, 59). Here, NRCAM is linked to Charcot-Marie-Tooth disease type 4C.