PLP1 and Pelizeaus-Merzbacher spectrum disorder: Among them, CNS oligodendroglial cell-related diseases typically include the proteolipid protein 1 (plp1) gene-related hypomyelinating leukodystrophy 1 [HLD1] (also called Pelizaeus–Merzbacher disease [PMD]) and other HLDs [33,34,35,36].