Collaborative Research: Biochemical Basis of Cellular Circadian Behavior

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Non-Technical Paragraph By establishing the genetic basis of rhythmic behavior, circadian clock research is a great success story in neuroscience. The molecular clock consists of positive and negative components that form a feedback loop that underlies brain rhythms. However, "the whole is greater than the sum of its parts," and we do not yet know how a handful of components coordinate to give rise to emergent daily rhythms. Therefore, this research aims to identify the biochemical properties of core clock proteins that enable rhythmic behavior. To do this, the team has developed an integrative approach that combines cell-based genetics and continuous monitoring of circadian behavior with biochemical/biophysical methods. This approach will allow them to study the function of clock proteins not only in test tubes in isolation, but also in the context of oscillatory behavior in interacting cells. This work will reveal how the "gears and springs" of the clock interact and function together, and this knowledge will increase our understanding of how the brain keeps time, as well as how proteins interact to regulate complex brain functions. The PI and his colleagues will teach a lecture/lab course that uses a "from math to genes to behavior" platform and provides cross-disciplinary training for graduate students. The team will also teach real world concepts in the local community about the health implications of circadian rhythms, which relates to people of all backgrounds and ages. These broader impacts will strengthen the nation's scientific infrastructure and improve people's health awareness. Technical Paragraph Genetic studies have identified several core clock components that form a negative feedback mechanism, which underlies circadian behavior. It is well established that, in the core feedback loop, BMAL1 and CLOCK are the two transcription activators and CRY serves as the chief repressor. However, negative feedback in transcription does not necessarily warrant recurring cellular processes with a ~24 hr periodicity. The circadian rhythm is an emergent property enabled by the core clock factors, but the biochemical basis of cellular circadian oscillation is not well understood. Recent studies from this research team show that the structurally flexible C-termini of BMAL1 and CLOCK play essential roles in regulating dynamic interactions with other clock factors to enable circadian oscillations. In the proposed research, the team will employ an integrated approach that combines cell-based genetics and kinetic bioluminescence assays with biochemical and biophysical methods to study how their C-termini use dynamic interactions to regulate rhythm amplitude and period length. In this way, protein function is assessed both in vitro and in the context of cellular circadian behavior. By providing a biochemical basis of cellular circadian behavior, this research will define the molecular architecture of the circadian transcription complex, advance current understanding of the negative feedback mechanism, and further the goals of behavioral neurobiology. During the research, the PI and his colleagues will provide cross-disciplinary education and training for graduate students and inform the general public about the important health implications of circadian rhythms.