Effects of constant light on circadian rhythmicity in mice lacking functional cry genes: dissimilar from per mutants

Mutations in the mCry and mPer genes lead to different responses in circadian period length under constant illumination.

• mCry1 and mPer1 mutant mice show a lengthening of the circadian period with increased light intensity.
• mCry2 and mPer2 mutant mice exhibit a shortening of the circadian period under the same conditions.
• Both mCry1 and mCry2 knockout mice increase their circadian periods in response to higher light intensity, similar to wild type mice.
• Increased illumination reduces rhythmicity in mCry1, mCry2, and mPer1 mutants, but not in mPer2 deficient mice.
• The observed increase in cycle length in mCry2 deficient mice contradicts earlier predictions and suggests the model is rejected.

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