The ER retention of misfolded PLP proteins can also induce the UPR, as observed in some PMD models including transfected cells, mouse models and in post-mortem specimen from a PMD patient (Hudson and Nadon, 1992; Southwood and Gow, 2001; Southwood et al., 2002, 2013; McLaughlin et al., 2007; Roboti et al., 2009). This evidence concerns the gene PLP1 and Pelizeaus-Merzbacher spectrum disorder.