The biological switch that sends mammals into their winter states has been traced to a single gene. Researchers at the University of Glasgow's School of Biodiversity, One Health and Veterinary Medicine report that the gene Dio3 is required to set the internal seasonal clock and must be active for winter dormancy to begin. The study, published in eLife, used transcriptomic sequencing with frequent sampling in the Djungarian hamster, a classic model of mammalian seasonality.
The team, led by Professor Tyler Stevenson, found that the lengthening nights of shortening days activate Dio3, which then establishes an interval timer lasting about six months. During that window the hamsters entered winter conditions, and when the gene's activity ended they spontaneously reverted to their summer state, matching the timing of spring emergence seen in wild mammals. The mechanism thus explains not only how winter behaviour starts but also how animals know when it should stop.
The implications reach well beyond hamsters. Dio3 is conserved across mammals, birds, reptiles and fish, and is more active in animals living nearer the poles than at the equator, suggesting a shared genetic architecture for seasonal timing across vertebrates. Understanding this clock matters for predicting how hibernating and migrating species will cope as climate change shifts the seasons they evolved to anticipate. The research was funded by the Leverhulme Trust.