Strong daily rhythms in mice with Per1 and Per2 gene mutations under constant light, and how these genes respond to long and short day lengths

Per2 mutant mice exhibit robust activity and body temperature rhythms with a period length of less than 24 hours under constant light conditions.

• Mutations in the Per1 and Per2 genes affect the phase resetting of circadian rhythms in response to light.
• Per1 mutant mice have longer than 24-hour rhythms in constant light, while Per2 mutants have shorter than 24-hour rhythms.
• Increased light illuminance prolongs the period length in Per1 mutants, whereas it shortens the period in Per2 mutants.
• The expression patterns of Per1 and Per2 genes are influenced by different light conditions.
• There appears to be a mutual influence between Per1 and Per2 genes regarding their timing of expression.
• The relationship between Per1 and Per2 gene expression may be important for processing day length information.

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