The Dio3 gene, present in all mammals, is essential for setting the internal seasonal clock and must be active to trigger winter dormancy.

A University of Glasgow-led study identifies Dio3 as the driver of seasonal behaviors such as hibernation and migration in mammals, with results published in eLife.

Researchers studied the Djungarian hamster to uncover the functional genetic mechanism behind the timing of seasonal behaviors, providing the first functional genetic evidence in this area, with findings published in eLife.

The study maps the sequence of gene expression changes that control long-term seasonal physiology and behavior, offering foundational insights into how seasonal timing is set in mammals.

Dio3 activity is higher in animals near the poles, indicating latitude-linked differences in gene expression related to seasonal physiology.

Dio3 is evolutionarily conserved across mammals, including humans, and shows higher activity in temperate regions with lower activity near the equator, suggesting latitude-driven variation in seasonal behavior.

Active Dio3 expression is particularly observed in polar-adjacent populations, reinforcing the connection between latitude and gene activity.

The research demonstrates that Dio3 is essential for establishing the mammal internal clock governing winter dormancy and must be active to trigger these seasonal changes.

The spring resumption of summer-like physiology aligns with the emergence of mammals in spring, highlighting Dio3’s role in sustaining and terminating the annual cycle.

Full citation: Calum Stewart et al., Hypothalamic deiodinase type-3 establishes the period of circannual interval timing in mammals (2025), DOI: 10.7554/elife.106383.2.

Lead researcher Professor Tyler Stevenson notes that identifying the genes and expression changes controlling long-term seasonal physiology advances understanding of health and illness related to annual cycles.

Understanding Dio3 expression patterns could illuminate annual health mechanisms and potential links to seasonality-related illnesses.