IMPDH has a function in the retina, apparently independent of its enzymatic activity, mediated by retina-specific variants. This moonlighting activity may involve the posttranscriptional regulation of rhodopsin mRNA. The adRP mutation D226N has reduced binding to nucleic acids and reduced association with polyribosomes. If this mutation perturbs the biosynthesis of rhodopsin in some way, this would explain a link between IMPDH and the mechanism of retinal degeneration.