Project Summary Circadian rhythms are fundamental in sculpting physiology, and their alignment is essential for optimal health. We have gained deep understanding of the cellular basis as well as the function of the central circadian clock of the suprachiasmatic nuclei (SCN), but we don’t yet understand how the SCN interacts with varied peripheral oscillators, and how these peripheral clocks integrate information from SCN- and non-SCN-inputs to maintain internal alignment as well as entrainment to 24h cycles. Here we will study two peripheral oscillators, the liver and skin. We will develop an animal model for study of the role of these peripheral clocks within the circadian system, to determine their entrainment capabilities. The central hypothesis of this proposal is that peripheral clocks retain some rhythmic capabilities when the SCN central clock is impaired, possibly including photic entrainment. The long term goal of this research is to understand the inter-dynamics of circadian clocks throughout the mammalian body and, ultimately, discover new tools to lessen the impact of circadian misalignment on health. Our research will first aim to characterize our new skin circadian clock reporter line K14 Cre; DBPKI/+ mice. We will more fully characterize our new mouse line using IVIS imaging, assays, and histology to rigorously determine sources of the bioluminescence recorded. Second, we will aim to test photic entrainment of skin and liver circadian rhythms in vivo in mice with or without brain central clock function. This aim will test the entrainment of skin and liver using methods for long-term circadian bioluminescent reporting from living animals, first in intact mice and then in mice with suprachiasmatic nuclei (SCN) ablation. Third, we will determine if these peripheral tissues show a wider range of entrainment than the central clock. We will test the ability for circadian rhythms of gene expression of K14 Cre; DBPKI/+ and Alb Cre; DBPKI/+ mice to entrain to cycles of varied cycle lengths (“T cycles”), to assess the range of entrainment, as compared with that of locomotor activity, using both intact and SCN-lesion mice. Completion of these studies will dramatically alter our understanding of the mammalian circadian system to include potentially photoreceptive peripheral clocks. The research will be conducted by diverse and engaged undergraduate women, with structured mentoring to encourage continued careers in biomedical science.