Epigenetic Reprogramming of Cellular Age

项目摘要 目前的观点认为，系统因素调节细胞和组织的老化，在促进和 逆转衰老过程，已经出现在异时共生（HP）和异时 血液交换（HBE）方案。我们的实验室进行了第一次HP研究，以评估细胞老化， 再生，因为它涉及组织稳态和修复以及细胞年龄的分子决定因素。 最初，我们专注于肌肉干细胞（MuSC）的变化，但我们和其他人后来探索了这些表型 在许多不同的细胞群体中发生变化。从那时起，我们探索了分子机制， 系统因素可能影响衰老过程。基于大量的证据，我们假设 细胞衰老特征的改变是由于一种表观遗传重编程的形式， 在诱导多能干细胞产生期间发生，但不丧失细胞分化。 细胞衰老的一般特征是异染色质的丢失和随后的细胞内蛋白质的调节异常。 转录稳定性异染色质与特定的组蛋白修饰显著相关， 特别是通过组蛋白3上赖氨酸9的二甲基化和三甲基化（分别为H3K9me2和H3K9me3）。初步 研究表明，H3K9me3和异染色质可以在MuSC中调节， 与衰老细胞的特征相吻合根据这些数据和相关的已发表的研究结果， 这一建议是HP和HBE将衰老表型转座到年轻和年老细胞的主要介质 是细胞表观基因组的调控，特别关注H3K9甲基化和异染色质 阵 为了验证这一假设，本提案分为三个具体目标。目的1：评估转录 以及MuSC响应HP的表观遗传特征。我们将建立HP和对照组， 在转录组和表观基因组的测定中，将MuSC分子特征与对照小鼠进行比较。 目的2：研究MuSC中衰老表型转位的表观遗传机制。 使用遗传和药理学工具，我们将调节暴露于H3K9的年轻和老年MuSC中的H3K9甲基化。 年轻人或老年人的血清。我们将测试H3K9甲基化的变化对表型的影响。 先前描述的响应于异时血清暴露的MuSC的变化。目的3：体内试验 H3K9甲基转移酶和脱甲基酶活性在介导HP对 MuSC。我们将使用遗传和药理学工具来调节体内MuSC中的H3K9甲基化。我们将 评估表观遗传和异染色质状态，以及MuSC响应HP的功能变化。 总之，这些研究将阐明年龄的表观遗传编程的分子机制， HP和HBE。

PROJECT SUMMARY Current ideas that systemic factors regulate the aging of cells and tissues, in terms of both promoting and reversing the aging process, have emerged from studies of heterochronic parabiosis (HP) and heterochronic blood exchange (HBE) protocols. Our lab performed the first HP studies in order to assess cellular aging and rejuvenation as it relates to tissue homeostasis and repair and in terms of molecular determinants of cellular age. Initially, we focused changes in muscle stem cells (MuSCs), but we and others later explored these phenotypic changes in many different cell populations. Since then, we have explored the molecular mechanisms by which systemic factors might influence the aging process. Based on numerous lines of evidence, we have hypothesized that the alteration in cellular aging features is due to a form of epigenetic reprogramming that is akin to that which occurs during induced pluripotent stem cell generation but without the loss of cellular differentiation. A general feature of cellular aging is the loss of heterochromatin and subsequent dysregulation of transcriptional stability. Heterochromatin is prominently associated with specific histone modifications, most notably by di- and tri-methylation of lysine 9 on histone 3 (H3K9me2 and H3K9me3, respectively). In Preliminary Studies, we have shown the H3K9me3 and heterochromatin can be regulated in MuSCs, with loss of both leading to features seen in aging cells. Based on these data and related published findings, the primary hypothesis of this proposal is that a primary mediator of HP and HBE transposition of aging phenotypes to young and old cells is the regulation of the cellular epigenome, and with a specific focus on H3K9 methylation and heterochromatin formation. To test this hypothesis, this proposal is divided into three Specific Aims. Aim 1: To assess the transcriptional and epigenetic signature of MuSCs in response to HP. We will establish HP and control pairs, and we will assess the MuSC molecular signatures compared to control mice in assays of the transcriptome and the epigenome. Aim 2: To examine the epigenetic mechanisms underlying the transposition of aging phenotypes in MuSCs. Using genetic and pharmacologic tools, we will modulate H3K9 methylation in young and old MuSCs exposed to young or old serum in vitro. We will test for the effect of changes in H3K9 methylation on the phenotypic changes of MuSCs previously described in response to heterochronic serum exposure. Aim 3: To test in vivo for the essential roles of H3K9 methyltransferase and demethylase activities in mediating the effects of HP on MuSCs. We will use genetic and pharmacologic tools to modulate H3K9 methylation in MuSCs in vivo. We will assess epigenetic and heterochromatin status, as well as the functional changes in MuSCs in response to HP. Together, these studies will elucidate molecular mechanisms of epigenetic programming of age in response to HP and HBE.