NDRG1 and Charcot-Marie-Tooth disease type 4D: The N-myc downstream-regulated gene 1 (NDRG1) was first described as a gene that is up-regulated by homocysteine [1] and during cellular differentiation [2], and later identified as the mutated gene in an inherited demyelinating neuropathy, Charcot-Marie-Tooth type 4D (CMT4D), in humans [3].