DHCR7-DT and hereditary spastic paraplegia: In humans, mutations in several subunits of the AP complexes result in severe genetic disorders, such as MEDNIK syndrome for AP-1 [10], Hermansky-Pudlack syndrome for AP-3 [11], cerebral palsy for AP-4 [12], [13], and hereditary spastic paraplegia for AP-5 [4], highlighting the fundamental role that AP complexes play.