RP9 and Alzheimer disease: Several causative genes have been associated with AD-RP, including RHO, PRPF31, PRPH2, RP1, IMPDH1, PRPF8, NR2E3, snRNP200, KLHL7, CRX, PRPF3, TOPORS, ADIPOR1, ARL3, CA4, FSCN2, GUCA1B, HK1, IMPG1, KIF3B, NRL, PRPF4, PRPF6, RDH12, ROM1, RP9, SEMA4A, SPP2, and many others [6].