PMP22 and Sensory neuropathy: Based on the observation that vitamin C treatment suppresses the expression of PMP22, a myelin gene that is overexpressed in one of the hereditary motor and sensory neuropathies, it has been suggested that vitamin C induces dose-dependent suppression of PMP22 expression by inhibiting the production of cAMP, a regulator of CREB-binding promoter located in PMP22 (Hai et al., 2001; Kaya et al., 2007; Belin et al., 2010).