Circadian Regulation of Cellular Homeostasis

生物钟在生物体如何适应每日（昼夜节律）、每月（月周）和每年的生物钟中起着关键作用。 通过调节新陈代谢、激素和新陈代谢的节律性波动， 神经递质释放，感觉能力和行为，包括睡眠。昼夜节律紊乱 (e.g.轮班工作、时区变化（“时差”）或社交时差）可导致显著的生理障碍。 这会导致睡眠和代谢紊乱，以及中风和癌症风险增加。最近 数据表明，生物钟是发育调节的，其计时活动是 悬浮在分化的组织中，以允许时钟组件在“发育时钟”中发挥作用， 调节干/祖细胞生物学和分化等过程。但殊不知 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产生的， 这些成分控制正常或恶性干/祖细胞行为。小鼠乳腺是一种 强大的模型系统，用于研究昼夜节律、发育和干/祖细胞生物学。 谱系追踪研究表明，乳腺含有动态细胞群，其中 自我更新的单能基底干细胞和管腔干细胞谱系在导管分化过程中产生各自的谱系， 延长，并负责乳腺癌细胞的异质性。我们已经证明，PER 2，a 生物钟中的转录因子，在乳腺发育期间差异表达， 是分支形态发生所必需的，这表明了昼夜节律时钟独立的发育作用。我们 最近使用Per 2-/-小鼠乳腺的数据表明，PER 2可能在乳腺癌中起关键作用。 上皮细胞谱系定型和稳态，并可能通过调节EYA 2的表达， 以及影响Wnt/β-连环蛋白和TGF-β信号传导。此外，我们还发现， 小鼠乳腺上皮细胞中Per 2表达下调，EYA 2表达增加 和Wnt/b-连环蛋白的活化。基于这些新的结果，我们假设PER 2的功能是整合 昼夜节律钟与发育时钟控制乳腺上皮细胞类型的稳态， 导管伸长和分支形态发生。为了解决这一假设，提出了三个具体目标。 Aim 1将测试在干细胞和祖细胞中的昼夜节律和昼夜节律破坏依赖性变化， 发育中的乳腺目标2将集中在使用遗传报告基因的PER 2在谱系定型中的作用 跟踪乳腺细胞分化并检查PER 2对干细胞稳态的影响。研究 目的3将确定EYA 2基因表达的PER 2依赖性调节和β-连环蛋白的调节。 乳腺形态发生在成功地完成这一目标后，我们将更好地了解 控制PER 2和EYA 2相互作用的分子机制以及对WNT/EYA的影响。 分支形态发生中的TGFb信号传导。

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.