Cloning and circadian expression of rat Cry1.

In mammals, two types of cryptochrome are involved in the regulation of the circadian rhythm. We previously characterized rat Cry2 and its expression in brain tissue [Eun et al. (2001)]. We report here the cloning of another cryptochrome gene, Cry1, from rat brain by reverse-transcription coupled to polymerase chain reaction (RT-PCR), together with rapid-amplification of cDNA ends (RACE). The cloned Cry1 cDNA consists of 2557 nucleotides and has a single open-reading frame encoding a protein of 588 amino acids with start and stop codons. The deduced amino acid sequence was 70% identical with that of rat Cry2. It also showed 95% identity with mouse and human Cry1 but relatively low identity of 82% with that of zebrafish. Circadian expression of rat Cry1 and Cry2 was examined in the suprachiasma nucleus (SCN) and eye by real-time PCR. Expression of Cry1 and Cry2 mRNA in the SCN displayed a circadian rhythm with a peak at the day/night transition, and there was a slightly different circadian pattern of expression of Cry1 and Cry2 in the eye.