PRPF6 and retinitis pigmentosa 1: Perturbations in the molecular interactions between the components of the U4/U6.U5 tri-snRNP complex are consistent with the fact that mutations in PRPF6, PRPF31, and USH1G/SANS have almost identical effects on splicing and that similar pathomechanisms leading to RP also cause similar retinal phenotypes.