RPGRIP1 and cone-rod dystrophy: CRD is caused by mutation in many genes such as ABCA4, ADAM9, C8orf37, CDHR1, CRX, DRAM2, GUCA1A, GUCY2D, PITPNM3, POC1B, PROM1, RAB28, RAX2, RIMS1, RPGRIP1, SEMA4A, and TTLL56.