Circadian rhythms are an adaptation to the daily cycle of night and day on Earth and control when an individual eats, sleeps, or works. One third of Canadians suffer from difficulty sleeping, and circadian disruptions to sleep are often associated with psychiatric diseases. For example, circadian disruptions may predispose patients to disease, or could be symptoms. However, the genetic, molecular, and physiological mechanisms that underlie these links are poorly understood. Furthermore, animals can have different circadian rhythms; they can be active during the day (and sleep and night), active during the night (and sleep during the day), or active during dawn/dusk. How these sleep, wakefullness, and other activities are partitioned to specific times of day is also poorly understood at both the genetic and brain circuitry level. Answering questions related to circadian rhythms and disease is complicated by the fact that the most prominent animal model for these phenomena is the nocturnal lab mouse, making translation of discoveries to day-active humans difficult. In this proposal we will use the emerging experimental model of cichlid fishes to study the neurobiology and genomics of circadian rhythms. Fish have long been recognized as excellent models for studying the neurobiology of sleep, and the genetics of human diseases. Cichlid fishes are as closely related as humans and chimpanzees, yet remarkably, we have discovered that they display as much variation in sleep and circadian rhythms as observed across all animals. Using a combination of traditional and sophisticated genomic techniques, we will map the genes and brain circuits required for these diverse circadian rhythms. Ultimately, this proposal will improve our understanding of the links between circadian rhythms, behaviour, and disease in both animal models and humans.
