PRPF6 and retinitis pigmentosa 1: The spliceosome is composed of 5 small nuclear RNAs (snRNAs), U1–U5, and many proteins including pre-mRNA splicing factors PRPF3, PRPF4, PRPF6, PRPF8, and SNRNP200, all of which are also genetic causes of RP (Ruzickova and Stanek, 2016).