ROLE OF MOUSE CRYPTOCHROME BLUE-LIGHT PHOTORECEPTOR IN CIRCADIAN PHOTORESPONSES

Cryptochromes are photoactive pigments in the eye that have been propo sed to function as circadian photopigments. Mice lacking the cryptochr ome 2 blue-light photoreceptor gene (mCry2) were tested for circadian clock-related functions. The mutant mice had a lower sensitivity to ac ute Light induction of mPer1 in the suprachiasmatic nucleus (SCN) but exhibited normal circadian oscillations of mPer1 and mCry1 messenger R NA in the SCN. Behaviorally, the mutants had an intrinsic circadian pe riod about 1 hour Longer than normal and exhibited high-amplitude phas e shifts in response to Light pulses administered at circadian time 17 . These data are consistent with the hypothesis that CRY2 protein modu lates circadian responses in mice and suggest that cryptochromes have a role in circadian photoreception in mammals.