Mutations in the pre-mRNA processing factor 4 (PRPF4) gene are a cause of retinitis pigmentosa (RP), an inherited disease that leads to blindness. PRPF4 is a key component of the spliceosome, which is responsible for pre-mRNA splicing. Mutations in PRPF4 cause mis-splicing of genes that are important for the retina, including those involved in phototransduction and photoreceptor disk morphogenesis.  ​​RP is characterized by progressive loss of photoreceptors and retinal pigment epithelium. Symptoms include difficulty seeing in dim light or at dusk, reduced peripheral vision, gradual narrowing of the area of good vision, and stumbling or tripping over objects in the periphery.

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