RPGR also has a retina-specific transcript, which includes a large 3′ terminal exon (ORF15) that is mutated in 60% of X-linked RP patients, which highlights the functional relevance of RPGR in the retina (Vervoort et al., 2000; Megaw et al., 2015). This evidence concerns the gene RPGR and retinitis pigmentosa 1.