These experiments aimed to distinguish between two hypotheses: that splicing factor mutations cause RP due to a retina-specific defect, either in splicing or in some other function involving these proteins; or that splicing factor RP results from a defect in splicing that is subpathological elsewhere in the body but which leads to a cumulative defect in the metabolically active, irreplaceable retinal tissue. Here, BLOC1S3 is linked to retinitis pigmentosa 1.