Epimutation at the CD4 locus: induction, propagation and repair

描述（由申请方提供）：表位突变是由短暂暴露于环境因素（如饮食和吸烟）诱导的自我维持的染色质畸变，发育中的胚胎尤其易感。在生殖细胞中诱导的表型突变可以遗传给后代，这具有深远的临床、生物学和进化意义。表型突变比经典的DNA突变更常见，并且是多种人类疾病的基础。尽管它们的稳定性，表观突变本质上是可逆的，这推动了表观遗传疗法的概念，该疗法试图使用靶向相关酶的“表观遗传药物”来修复表观突变。目前，表观突变的诱导和增殖机制尚不清楚，表观遗传药物毒性较大。我们开发了一种新的动物模型来解决这些问题。具体来说，我们已经修改了CD 4基因座，以允许实验操作其表观遗传状态; CD 4是一种抗原辅助受体，表达在CD 4 T细胞的表面上，但在CD 8 T细胞中被抑制。我们发现，在随后的成年小鼠，甚至其后代的CD 8 T细胞中，CD 4基因座在子宫内的瞬时激活使CD 4抑制不稳定，表明我们已经成功地诱导了CD 4基因座的表型突变。在这里，我们建议使用这个系统来解决的诱导和传播的表位突变的机制，利用的事实，CD 4调节已被广泛研究。为此，我们将定义与CD 8细胞中的表突变相关的染色质缺陷，解剖导致在胎儿发育过程中建立表突变的过程，并表征精子中的染色质缺陷（Am 1）。此外，我们将测试一种新的策略，用于选择性地修复CD 4基因座的表突变（目的2）。我们的研究将提供期待已久的见解epimmutations，并建立一个新的范式研究和修复epimmutations。 公共卫生相关性：不利的环境条件可以稳定地改变基因功能，而不会使DNA突变，这种变化是许多人类疾病的基础。我们将研究这一显著现象的机制，并寻求使用新方法来逆转异常变化。

DESCRIPTION (provided by applicant): Epimutations are self-sustaining chromatin aberrations induced by transient exposures to environmental factors such as diet and smoking, with developing embryos particularly susceptible. Epimutations induced in the germ cells can be transmitted to the offspring, which has profound clinical, biological and evolutionary implications. Epimutations are far more common than classical DNA mutations, and underlie diverse human diseases. Despite their stability, epimutations are intrinsically reversible, which has fueled the concept of epigenetic therapy that seeks to repair epimutations using "epigenetic drugs" targeting relevant enzymes. At present, little is known about the mechanisms of induction and propagation of epimutations, and the epigenetic drugs are rather toxic. We have developed a novel animal model to address these problems. Specifically, we have modified the CD4 locus to allow for experimental manipulation of its epigenetic states; CD4 is an antigen coreceptor expressed on the surface of CD4 T cells but repressed in CD8 T cells. We found that transient activation of the CD4 locus in utero destabilizes CD4 repression in CD8 T cells in the ensuing adult mice and even their offspring, indicating that we have successfully induced an epimutation at the CD4 locus. Here we propose to use this system to address the mechanisms of the induction and transmission of an epimutation, taking advantage of the fact that CD4 regulation has been extensively studied. To this end, we will define the chromatin defects associated with the epimutation in CD8 cells, dissect the process leading to the establishment of the epimutation during fetal development, and characterize the chromatin defects in sperm (Am 1). In addition, we will test a novel strategy for selectively repairing the epimutation at the CD4 locus (Aim 2). Our study will provide long-awaited insights into epimutations, and establish a new paradigm for studying and repairing epimutations. PUBLIC HEALTH RELEVANCE: Adverse environmental conditions can stably changes gene functions without mutating DNA, and such changes underlie many human diseases. We will study the mechanisms of this remarkable phenomenon and seek to reverse the aberrant changes using a new approach.)