abbr. for cone-rod homeobox protein; a transcription factor protein (299 residues) that contains a homeodomain in its N-terminal region and is expressed specifically in developing and mature photoreceptor cells of the retina. It regulates expression of the genes for rhodopsin and other photoreceptor-specific proteins. Mutations in the gene at 19q13.3 result in a form of blindness called Leber's congenital amaurosis.