A Quebec Discovery Unravels the Mystery
A research team at the Montreal Clinical Research Institute (IRCM) has just shed light on a poorly understood but essential question: how do neuronal circuits involved in synchronizing our biological clock with the day-night cycle develop? These findings, recently published in Cell Reports, could pave the way for new approaches to treating circadian rhythm disorders.
While Canadians are adjusting to the time change that impacts their sleep pattern, this research provide new insight into the cellular mechanisms through which humans adapt to variations in the circadian rhythm. Synchronization of our internal clock to the day-night cycle relies on specialized light-sensitive cells in the retina that send information about environmental light conditions to the brain, allowing it to adjust our daily rhythms. However, the mechanisms controlling the formation of this critical neuronal circuit remained poorly understood. This is the question that the team, led by Dr. Michel Cayouette at the IRCM, in collaboration with Drs. Nicolas Cermakian and Arjun Krishnaswamy at McGill University, sought to answer.
Their study reveals that Müller glial cells,which are typically considered as simple support cells in the retina, actually play a key role in the assembly of this circuit. By releasing specific chemical signals, they enable light-sensitive neurons to properly connect to the brain. In the absence of these signals, the neurons become overly reactive, preventing them from properly entraining our biological clock after changes in the light-dark cycle.
“These findings show that the dialogue between nerve cells and their glial partners is essential for building the system that regulates our circadian rhythms,” explains Dr. Cayouette. The study’s co-first authors are Thomas Brown and Noémie Vilallongue, members of his team.
Funded by the Canadian Institutes of Health Research (CIHR), this research is particularly relevant in contexts where disruptions to circadian rhythms are linked to conditions such as insomnia, seasonal depression, metabolic imbalances, and even certain cancers. A better understanding of how this system work could one day help prevent or correct these disorders.
