DHCR7-DT and hereditary spastic paraplegia: Mutations on AP subunits have been implicated in a variety of inherited disorders, including MEDNIK syndrome, Hermansky–Pudlak syndrome, Fried syndrome and hereditary spastic paraplegia (HSP) (Abdollahpour et al., 2015; Alsaif et al., 2019; Borck et al., 2008; Dell'Angelica et al., 1999).