MEF2A and retinitis pigmentosa: Interestingly, many of the phototransduction genes downregulated in Mef2d−/− retinas are also mutated in human retinal diseases that result in photoreceptor degeneration, including retinitis pigmentosa (RP) and cone-rod dystrophy.14 Moreover, a decrease in MEF2 has been observed in other genetic mouse models of RP and LCA, suggesting the potential role of MEF2 transcription factors in human homologues of the disease.12,13