Bmal1 Is Required for Normal Reproductive Behaviors in Male Mice.

Circadian rhythms synchronize physiological processes with the light-dark cycle and are regulated by a hierarchical system initiated in the suprachiasmatic nucleus, a hypothalamic region that receives direct photic input. The suprachiasmatic nucleus then entrains additional oscillators in the periphery. Circadian rhythms are maintained by a molecular transcriptional feedback loop, of which brain and muscle aryl hydrocarbon receptor nuclear translocator-like protein 1 (BMAL1) is a key member. Disruption of circadian rhythms by deletion of the BMAL1 gene (Bmal1 knockout [KO]) induces a variety of disease states, including infertility in males, due to unidentified mechanisms. We find that, despite normal sperm function, Bmal1 KO males fail to mate with receptive females, indicating a behavioral defect. Mating is dependent on pheromone detection, as are several other behaviors. We determined that Bmal1 KO males also fail to display aggression and avoidance of predator scent, despite intact main olfactory func...