Collaborative Research: IPY: Extremes of hibernation physiology: patterns of expression, regulation, and limits

由于北极地松鼠分布在高纬度地区，它们自然会受到任何冬眠动物中日照时间和温度最极端的季节变化的影响。北极地松鼠有独特的适应能力，使它们能够在北极条件下茁壮成长。拟议的工作将解决冬眠生理学中的重要问题，使用综合方法，包括用于测量代谢和呼吸交换率的呼吸测量法，用于评估代谢燃料使用和身体组成变化的稳定同位素分析，以及用于极端条件下冬眠分子理解的基因组方法。该项目旨在1）阐明北极地松鼠在北极冬眠期间从哪些代谢燃料（脂肪，碳水化合物，蛋白质）中汲取，2）量化参与代谢燃料选择的酶的基因表达，3）确定在零度以下体温下冬眠的较低温度限制，以及4）继续监测阿拉斯加北坡自然种群的身体和冬眠温度。 这些实地措施将涉及冬季身体状况的变化，每年的冬眠时间和其他生活史事件，以及在气候变化的背景下对这一人口的繁殖和持久性的影响。 预计北极地松鼠将在低至-40摄氏度的环境温度下冬眠，随着环境温度的降低，它们将增加对蛋白质的依赖。 在低温下，北极地松鼠对代谢燃料选择的调节将通过增加促进蛋白质代谢和糖合成的基因表达来实现。 由于冬眠动物已被用作脑缺血（减少流向大脑的血液）、创伤性头部损伤和体温过低的模型，因此对冬眠的生理学和基因组学的研究具有生物医学意义。 此外，这项研究将帮助我们更好地了解敏感的北极生态系统中生物对气候变化的反应。该项目是跨学科的，将提供培训，在现场和实验室设置，1博士后，2博士生和本科生在分子，同位素，生理和生态技术。它是国际性的，与中国上海生物研究所的科学家合作。这项研究的结果将通过出版物和在区域、国家和国际会议上的介绍以及当地的解释性展览来传播。

Because of their high latitude distribution, arctic ground squirrels are naturally exposed to the most extreme seasonal changes in day length and temperature of any hibernator. Arctic ground squirrels have unique adaptations that allow them to thrive under arctic conditions. The proposed work will resolve important questions in hibernation physiology using integrated approaches including respirometry for measuring rates of metabolism and respiratory exchange, stable isotope analysis for assessing changes in metabolic fuel use and body composition, and genomic approaches for a molecular understanding of hibernation in extreme conditions. This project seeks to 1) elucidate which metabolic fuels (fat, carbohydrate, protein) arctic ground squirrels draw from during arctic hibernation, 2) quantify the expression of genes for enzymes involved in metabolic fuel selection, 3) identify lower thermal limits to hibernation at sub-zero body temperatures, and 4) continue monitoring body and hibernacula temperatures in a natural population on the North Slope of Alaska. These field measures will be related to changes in body condition over winter, annual timing of hibernation and other life history events, and effects on reproduction and persistence of this population in the context of climate change. It is anticipated that arctic ground squirrels will hibernate in ambient temperatures as low as -40 degrees C, and that they will increase reliance on protein to fuel metabolism with decreasing ambient temperatures. At low temperatures, regulation of metabolic fuel selection by arctic ground squirrels will be accomplished via increased expression of genes that promote protein metabolism and gluconeogenesis (synthesis of sugar). Because hibernators have been used as models for cerebral ischemia (reduced blood flow to the brain), traumatic head injury, and hypothermia, investigations of the physiology and genomics of hibernation have biomedical implications. Moreover, this research will help us better understand organismal responses to a changing climate in the sensitive arctic ecosystem. This project is interdisciplinary and will provide training, in both field and lab settings, to 1 post-doc, 2 PhD students and undergraduates in molecular, isotopic, physiological and ecological techniques. It is international with a collaborating scientist from the Shanghai Institutes of Biology in China. Results of this research will be disseminated through publications and presentations at regional, national and international meetings and local interpretive displays.