Circadian Regulation of Cellular Homeostasis

生物钟在生物体如何适应日常(昼夜节律)、每月(昼夜节律)和年度节律方面起着关键作用 (一年一次)通过调节新陈代谢、激素和激素的节律性波动来改变环境 神经递质释放、感觉能力和行为，包括睡眠。昼夜节律紊乱 (例如，倒班工作、时区变化(时差)或社交时差)会导致显著的生理反应 后果包括睡眠和代谢紊乱，以及中风和癌症风险增加。近期 数据表明，生物钟是发育调节的，它的守时活动是 悬浮在分化的组织中，使时钟组件在“发育时钟”中发挥作用 调节干细胞/祖细胞生物学和分化，以及其他过程。然而，目前尚不清楚 这种从昼夜节律到发育活动的功能转变是如何实现的，也不知道时钟是如何实现的 这些成分控制正常或恶性的干细胞/祖细胞行为。小鼠的乳腺是一种 用于研究昼夜节律、发育和干细胞/祖细胞生物学的强大模型系统。 血统追踪研究表明，乳腺中有动态的细胞群，在这些细胞群中 自我更新的单一能力的基底和腔内干细胞谱系在导管形成过程中形成各自的谱系 延长，并负责乳腺癌细胞的异质性。我们已经证明了PER2，a 转录因子在生物钟中，在乳腺发育过程中差异表达，以及 是分支形态发生所必需的，这表明了昼夜节律独立于时钟的发育作用。我们的 使用PER2-/-小鼠乳腺的最新数据表明，PER2可能在乳腺中发挥关键作用 上皮细胞谱系承诺和动态平衡，并可能通过调节EYA2的表达来实现这一点 并影响Wnt/b-catenin和转化生长因子-b信号转导。此外，我们还发现，昼夜节律的干扰 小鼠乳腺上皮细胞PER2表达下调，EYA2表达上调 和Wnt/b-catenin的激活。基于这些新的结果，我们假设PER2功能是整合 生物钟和发育钟控制乳腺上皮细胞类型的动态平衡 导管伸长和分支形态发生。为了解决这一假设，本文提出了三个具体目标。 目标1将测试昼夜节律和昼夜节律中断依赖的干细胞和祖细胞的变化 发育中的乳腺。目标2将利用遗传记者重点研究PER2在血统承诺中的作用 示踪乳腺细胞分化，检测PER2对干细胞动态平衡的影响。研究项目： 目的3将确定PER2依赖的EYA2基因表达的调节和b-连环蛋白的调节 乳腺形态发生。在成功完成这一目标后，我们将有更好的理解 PER2和EYA2相互作用的分子机制及其对WNT/WNT的影响 TGFb在分枝形态发生中的信号转导。

Biological clocks play a key role in how organisms adapt to daily (circadian), monthly (circalunar), and annual (circannual) changes in the environment by regulating rhythmic fluctuations in metabolism, hormone and neurotransmitter release, sensory capabilities and behaviors, including sleep. Disruption of circadian rhythms (e.g. shift work, time zone changes (“jet lag”), or social jet lag), can result in significant physiological consequences including sleep and metabolic disorders, as well as increased risk of stroke and cancer. Recent data indicate that the circadian clock is developmentally regulated and that its time-keeping activity is suspended in differentiating tissues to allow clock components to function in a “developmental clock”, that regulates stem/progenitor cell biology and differentiation, among other processes. However, it is not known how this functional shift from circadian to developmental activities is achieved, nor is it known how clock components control normal or malignant stem/progenitor cell behaviors. The mouse mammary gland is a powerful models system for the study of circadian rhythms, development, and stem/progenitor cell biology. Lineage tracing studies have demonstrated that the mammary gland harbors dynamic cell populations in which self-renewing unipotent basal and luminal stem cell lineages give rise to their respective lineages during ductal elongation, and are responsible for breast cancer cellular heterogeneity. We have shown that PER2, a transcription factor in the circadian clock, is differentially expressed during mammary gland development, and is required for branching morphogenesis, suggesting a circadian clock-independent developmental role. Our recent data using Per2-/- mouse mammary glands suggest that PER2 may play a critical role in mammary epithelial cell lineage commitment and homeostasis, and may do so by regulating the expression of EYA2 as well as influencing Wnt/b-catenin and TGF-b signaling. Moreover, we have found that circadian disruption in mice results in down regulation of Per2 expression in mammary epithelial cells and increased EYA2 expression and activation of Wnt/b-catenin. Based on these new results, we hypothesize that PER2 functions to integrate the circadian clock with the developmental clock to control homeostasis of mammary epithelial cell types during ductal elongation and branching morphogenesis. To address this hypothesis three Specific Aims are proposed. Aim 1 will test circadian and circadian disruption dependent changes in stem and progenitor cells in the developing mammary gland. Aim 2 will focus on the role of PER2 in lineage commitment using genetic reporters to trace mammary cell differentiation and examine the effect of PER2 on stem cell homeostasis. Studies in Aim 3 will determine PER2-dependent regulation of EYA2 gene expression and regulation of b-catenin in mammary gland morphogenesis. Upon successful completion of this aim we will have a better understanding of the molecular mechanisms that govern the interaction of PER2 and EYA2 as well as the effect on WNT/ TGFb signaling in branching morphogenesis.