PRPF31 and retinitis pigmentosa 1: The pathological mechanism whereby PRPF31 missense mutations result in RP is therefore protein insufficiency, and this may also underlie the disease pathology of other PRPF31 mutations studied to date, including gene deletion [7,10], where no mutant protein can be present, and mutations leading to premature termination where NMD of mutant transcripts occurs [13].