IMPDH1 and retinitis pigmentosa: Mutations in inosine 5′-monophosphate dehydrogenase 1 (IMPDH1), a dual RNA-binding and dinucleotide-binding enzyme [33], cause retinitis pigmentosa [34], an eye disease with severe vision impairment attributable to the progressive degeneration of the photoreceptors in the retina [35].