The thirteen-lined ground squirrel, Ictidomys tridecemlineatus, is a mammal capable of lowering its T_b to almost 0 °C while undergoing deep torpor bouts over the winter. To decrease its metabolic rate to such a drastic extent, the squirrel must undergo multiple physiological, biological, and molecular alterations including downregulation of almost all nonessential processes. Epigenetic regulation allows for a dynamic range of transient phenotypes, allowing the squirrel to downregulate energy-expensive and nonessential pathways during torpor. DNA methylation is a prominent form of epigenetic regulation; therefore, the DNA methyltransferase (DNMT) family of enzymes were studied by measuring expression and activity levels of the five major proteins during torpor bouts. Additionally, specific cytosine marks on genomic DNA were quantified to further elucidate DNA methylation during hibernation. A tissue-specific response was observed that highlighted variant degrees of DNA methylation and DNMT expression/activity, demonstrating that DNA methylation is a highly complex form of epigenetic regulation and likely one of many regulatory mechanisms that enables metabolic rate depression in response to torpor.

十三行地松鼠Ictidomys tridecemlineatus是一种能够降低其T _{b的哺乳动物}在冬季经历深度麻木时，温度几乎降至 0°C。为了将其代谢率降低到如此剧烈的程度，松鼠必须经历多种生理、生物学和分子改变，包括几乎所有非必要过程的下调。表观遗传调控允许瞬时表型的动态范围，允许松鼠在麻木期间下调能量昂贵和非必需的途径。DNA甲基化是表观遗传调控的一种突出形式。因此，DNA 甲基转移酶 (DNMT) 酶家族通过测量鱼雷发作期间五种主要蛋白质的表达和活性水平进行了研究。此外，对基因组 DNA 上的特定胞嘧啶标记进行量化，以进一步阐明冬眠期间的 DNA 甲基化。