Study reveals a winter version of the biological clock

PULLMAN, Wash. - Researchers at Washington State University have discovered a molecular "winter lock" that keeps animals in a less active winter state until favorable conditions return, a discovery that could improve pest control and lead to a better understanding of seasonal health conditions in humans.

Using fruit flies as a model, researchers found the "winter lock" is driven by seasonal changes in a key gene found in the circadian clock, which regulates daily biological rhythms. Through a process called alternative splicing, the gene, known as timeless, produces a winter-specific protein that alters activity patterns and suppresses reproduction. The findings, published in Science Advances, suggest animals may rely on multiple versions of their biological clock, with different molecular arrangements helping them adapt to seasonal environmental changes.

"We've known for a long time that animals use environmental cues to prepare for seasonal changes, but we haven't understood exactly how that information is integrated by the biological clock," said Sergio Hidalgo, an assistant professor in the WSU College of Veterinary Medicine's Department of Integrative Physiology and Neuroscience and corresponding author on the study. "What we found is that the clock itself can be rearranged into a winter state that helps animals stay there until conditions are favorable enough to switch back to summer mode."

Animals, plants and even bacteria use environmental cues to anticipate seasonal change and adjust their behavior and physiology accordingly. These adaptations can include migration, hibernation, reproductive changes and periods of dormancy that help organisms survive harsh conditions and food shortages.

While scientists know changes in day length and temperature help trigger these seasonal responses, exactly how organisms integrate those signals to coordinate seasonal behavior was largely unknown. The circadian clock was suspected to play a role in that process, but exactly how it influenced seasonal timing was unclear.

The new study found that alternative splicing - a process that allows the gene to produce different proteins - of the timeless gene plays a critical role in helping fruit flies enter and maintain a winter state, which includes shifted daily activity patterns and reproductive dormancy. The produced protein alters the function of the circadian clock, creating a molecular "winter lock" that remains in place until environmental cues signal it is time to return to a summer state.

"For years, we've been studying what is essentially the summer version of the clock," Hidalgo said. "This work shows that the clock can be remodeled in winter, creating a system that functions differently and helps animals maintain a winter program."

Hidalgo suspects similar mechanisms exist in agricultural pests and disease-carrying insects such as mosquitoes. Understanding how insects determine seasonal timing could provide new ways to disrupt populations by interfering with the biological processes that help them survive changing seasons.

The findings may also help scientists better understand seasonal influences on human health. Conditions such as seasonal affective disorder and some neurological and psychiatric disorders have been linked to seasonal patterns, though the biological processes driving those changes remain poorly understood.

The study included researchers from WSU and the University of California, Davis. Co-authors included Audrey Berry, a WSU alumna and research intern in Hidalgo's lab, along with collaborators from both institutions.

The research was supported by the National Institutes of Health and the Pew Charitable Trusts.

Media Contacts

• Sergio Hidalgo, College of Veterinary Medicine, 509-335-8113, [email protected]
• Devin Rokyta, WSU College of Veterinary Medicine communications, 509-335-1911, [email protected]