Non syndromic RP can also be caused by biallelic or monoallelic mutations in one of eight pre-mRNA splicing factors; PRPF3 (Chakarova et al., 2002), PRPF4 (Chen et al., 2014; Linder et al., 2014), PRPF6 (Tanackovic et al., 2011), PRPF8 (McKie et al., 2001), PRPF31 (Vithana et al., 2001), SNRNP200 (Zhao et al., 2009), RP9 (PAP1) (Keen et al., 2002), DHX38 (PRPF16) (Ajmal et al., 2014). This evidence concerns the gene RP9 and retinitis pigmentosa 1.