Molecular cloning of the cone-rod homeobox gene (Crx) from the rat and its temporal expression pattern in the retina under a daily light-dark cycle.

The primary structure of the cone-rod homeobox protein (CRX), a member of the OTX-like homeobox protein family, in the rat was deduced from the cDNA nucleotide sequence. The deduced protein consisted of 299 amino acid residues with motifs conserved in mammalian CRXs, and was 98% identical to mouse CRX. Northern blot analysis showed that Crx mRNA levels in the rat retina were constant under a daily light-dark cycle. These findings suggest that the expression mechanism of rat Crx in the retina was different from that in the pineal, where Crx mRNA exhibits a daily expression rhythm.