Spontaneous Recovery of Circadian Organization in Mice Lacking a Core Component of the Molecular Clockwork.

ABSTRACT: Circadian rhythms are generated by interlocked transcriptional-translational feedback loops of circadian clock genes and their protein products. Mice homozygous for a functional deletion in the Period-2 gene (Per2^m/m mice) exhibit short free-running circadian periods and eventually lose behavioral circadian rhythmicity in constant darkness (DD). We investigated Per2^m/m mice in DD for several months and identified a categorical sex difference in the dependence on Per2 for maintenance of circadian rhythms. Nearly all female Per2^m/m mice became circadian arrhythmic in DD, whereas free-running rhythms persisted in 37% of males. Remarkably, with extended testing, Per2^m/m mice did not remain arrhythmic in DD, but after varying intervals spontaneously recovered robust, free-running circadian rhythms, with periods shorter than those expressed prior to arrhythmia. Spontaneous recovery was strikingly sex-biased, occurring in 95% of females and 33% of males. Castration in adulthood resulted in male Per2^m/m mice exhibiting female-like levels of arrhythmia in DD, but did not affect spontaneous recovery. The circadian pacemaker of many gonad-intact males, but not females, can persist in DD for long intervals without a functional PER2 protein; their circadian clocks may be in an unstable equilibrium, incapable of sustaining persistent coherent circadian organization, resulting in transient cycles of circadian organization and arrhythmia.

SUBMITTER: Riggle JP 

PROVIDER: S-EPMC9484001 | biostudies-literature | 2022 Feb

REPOSITORIES: biostudies-literature