PLP1 and Pelizeaus-Merzbacher spectrum disorder: The molecular pathogenesis of PMD includes the overexpression of a PLP1 protein localized and accumulated in the endoplasmic reticulum (ER) [15] and late endosomes/lysosomes in oligodendrocytes [16] and also causes ER stress and the accumulation of cholesterol, which results in the subsequent mis-sorting/mistrafficking of proteins and raft components (Figure 2A).