The cold-responsive circadian gene regulatory landscape and its relevance to torpor

该项目旨在了解低温调节基因和行为的分子机制。为了应对严酷的环境条件，如冬季的寒冷温度或食物短缺的时候，许多哺乳动物采取了一种被称为麻木的非凡行为。在这里，动物进入新陈代谢降低的状态，这伴随着它们的体温急剧下降。一系列长时间的麻木被称为冬眠。尽管麻木对动物生物学很重要，但到目前为止，我们还不清楚控制这种状态进入、维持和离开的分子机制，但这样的知识将为急救医学、长寿和太空旅行方面的范式转换进展提供基础。我们最近发现了冷却和生物钟之间的联系，这可能解释了麻木的一些最基本的方面。生物钟是一种古老的高度保守的计时机制，是所有生命固有的。生物钟将细胞和生物体生理学的几乎所有方面都与地球的24小时昼夜周期相一致。调整时钟以适应不断变化的环境的能力对健康至关重要，我们大多数人都经历过时钟调整不当的后果，表现为“时差”。温度是生物钟的关键时间线索，这一信号如何解释对时钟基因的影响在很大程度上尚不清楚。我们发现，患者在手术过程中经历的将人类心脏细胞冷却到低温，对染色体的结构有深远的影响。这会导致负性调节生物钟的基因戏剧性地激活，从而停止或“冻结”其节律性。复温细胞会重新激活节律性，并有效地导致时钟的重置。我们在人类细胞模型中的这些观察结果与小型哺乳动物的麻木有显著的相似之处。当动物进入麻木状态时，同样的基因也会被激活，而生物钟的重新设置被认为是摆脱麻木的关键。这些相似之处提供了一个独特的机会来解决控制昼夜节律和旋风的基本机制。我们使用培养的人类细胞的降温和复温方法为我们提供了一个简单但有效的可控程序来解开改变染色体结构从而激活和停用时钟基因的分子机制。在这个提案中，我们将使用最新的生化和显微镜方法来描述染色体结构以前所未有的分辨率发生的变化，并阐明这是如何调节和重置细胞钟的。然后，我们可以使用相同的方法来理解这些机制如何管理和重新配置处于昏迷状态的小鼠的细胞。确定染色体结构的重组在调节细胞时钟中所起的作用，对于理解支撑细胞计时的机制及其在生物过程中的作用，如麻木，是至关重要的。虽然我们不能进入麻木状态，但对这些机制的了解可能会提供在人类中诱导类似麻木状态的策略。这将在医学上开辟巨大的新应用，特别是用于治疗创伤患者，以防止组织损伤，并可能有助于拉开移植器官储存的序幕。此外，麻木作为一种工具将为许多挑战提供解决方案，包括肌肉和骨骼丢失，以及辐射暴露，这些挑战必须克服，才能使人类在长时间的太空旅行中生存下来。

This project aims to understand the molecular mechanisms by which cold temperatures regulate genes and behaviour. In response to severe environmental conditions such as cold temperatures during winter or at times of food shortage, many mammals adopt a remarkable behaviour known as torpor. Here, animals enter a state of reduced metabolism, and this is accompanied by a drastic drop in their body temperature. A series of prolonged bouts of torpor is referred to as hibernation. Despite the importance of torpor to animal biology, to date, we do not understand the molecular mechanisms that control the entry, maintenance, and exit from this state, but such knowledge would provide the substrate for paradigm-shifting advances in emergency medicine, longevity, and space travel. We have recently identified links between cooling and the circadian clock that may explain some of the most fundamental aspects of torpor. The circadian clock is an ancient highly conserved time keeping mechanism inherent to all life. The circadian clock aligns almost all aspects of cellular and organism physiology to the earth's 24h day and night cycle. The ability to adjust the clock to a changing environment is of fundamental importance to health and most of us have experienced the consequences of a mal-adjusted clock in the form of "jetlag". Temperature is a crucial time cue to the circadian clock, and how this signal is interpreted to impact on clock genes is largely unknown.We discovered that cooling human heart cells to low temperatures, as experienced by patients during surgical procedures, has a profound impact on the architecture of the chromosomes. This results in the dramatic activation of genes that negatively regulate the circadian clock and thus stop or "freeze" its rhythmicity. Rewarming cells reactivates rhythmicity and effectively causes the resetting of the clock. There are remarkable similarities between these observations we made in the human cell model and torpor in small mammals. The same genes are activated when animals enter torpor and resetting of the circadian clock has been proposed to be critical for the exit from torpor. These parallels offer a unique opportunity to address the fundamental mechanisms that control both circadian rhythms and torpor.Our cooling and rewarming approach using cultured human cells provides us with a simple but effective controllable procedure to unravel the molecular mechanisms that change the structure of chromosomes and thus activate and deactivate clock genes. In this proposal we will use the very latest biochemical and microscopy approaches to characterise the changes to the architecture of the chromosomes at unprecedented resolution and elucidate how this regulates and resets the cellular clock. We can then use the same methodology to understand how these mechanisms also govern and reconfigure the cells of mice in torpor. Defining the role that the reconfiguration of chromosomal architecture plays in the regulation of the cellular clock is fundamental to the understanding of the mechanics that underpin cellular time keeping, and its role in biological processes such as in torpor. Whilst we cannot enter torpor, understanding of these mechanisms may provide strategies to induce torpor like states in humans. This would open tremendous new applications in medicine in particular for the treatment of trauma patients to prevent tissue damage and may help to prologue the storage of transplant organs. In addition, torpor as a tool would provide solutions to many challenges including muscle and bone loss, and radiation exposure that have to be overcome to enable humans to survive long duration space travel.