Constant light changes daily activity patterns differently in mice missing cry genes compared to those missing per genes

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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