Understanding epigenetic remodeling in primordial germ cells

摘要 生殖细胞负责将父母的基因组和表观基因组从一代传到另一代 下一首。尽管受精后基因组不会改变(DNA受损的情况除外)， 哺乳动物的表观基因组通过一个被称为表观遗传重塑的过程发生实质性的改变。之后 胚胎植入，第二波表观遗传重塑，这一次发生在新指定的胚胎中 胚胎的细胞被称为原始生殖细胞(PGCs)。第二波表观遗传重塑，大多数 值得注意的是，从表观基因组中消除DNA甲基化被推测会擦除任何获得性表观等位基因 可能会导致子孙后代患病。在过去的五年里，我的实验室与该领域的同事们一起 发现小鼠和人PGCs的DNA甲基化重塑是不完整的，涉及阶段- DNA甲基化消除和DNA甲基化保护的依赖组合。在我们之前的 Funding期间，我们发现破坏PGCs中阶段依赖的DNA甲基化重塑导致 生殖细胞丢失和不育。鉴于正确分期的DNA甲基化重塑对 原生殖细胞的生物学和繁殖能力，我们接下来对潜在的染色质景观感兴趣 负责动态DNA甲基化保护和擦除。这项工作的结果将显著 增强我们对生殖的表观遗传学基础的知识。在这次更新中，我们的总体假设是 组蛋白H3赖氨酸27三甲基化上游的多梳抑制物复合体2(H3K27me3)(目标1)和 H3K9me3上游的三方基序28(Trim28)(Aim 2)在阶段依赖的DNA中起主要作用 前列腺癌的甲基化重塑。为了解决这些假设，我们的目标是使用基因组学的组合， 表观基因组学和小鼠建模。此外，我们还计划使用单细胞测序技术(目标3) 以确定pGCs的真正表观遗传基态。综上所述，确定PGCs的表观遗传景观 而维持它所需的酶对未来扰乱表观基因组的研究至关重要 妊娠期PGCs，或在PGCs中鉴定可用于特定检测的表观遗传热点 在未来不孕不育或跨代表观遗传中的作用。

Summary Germ cells are responsible for the passage of a parent's genome and epigenome from one generation to the next. Although the genome does not change after fertilization (except in instances of DNA damage) the epigenome in mammals is substantially altered through a process known as epigenetic remodeling. After embryo implantation, a second major wave of epigenetic remodeling occurs, this time in newly specified germ cells of the embryo called primordial germ cells (PGCs). The second wave of epigenetic remodeling, most notably erasure of DNA methylation from the epigenome is speculated to erase any acquired epialleles that could cause disease in future generations. In the last five years, my lab together with colleagues in the field discovered that DNA methylation remodeling in mouse and human PGCs is incomplete, involving stage- dependent combinations of DNA methylation erasure and DNA methylation protection. In our previous funding period, we showed that disrupting stage-dependent DNA methylation remodeling in PGCs results in germ cell loss and infertility. Given the importance of correctly staged DNA methylation remodeling to the biology of PGCs and the ability to reproduce, we are next interested in the underlying chromatin landscape responsible for dynamic DNA methylation protection and erasure. Results from this work will significantly enhance our knowledge of the epigenetic basis of reproduction. In this renewal, our overall hypothesis is that Polycomb repressor complex 2 upstream of Histone H3 Lysine 27 trimethylation (H3K27me3) (aim 1) and Tripartite motif 28 (Trim28) upstream of H3K9me3 (aim 2) play major roles in stage-dependent DNA methylation remodeling in PGCs. To address these hypotheses, we aim to use a combination of genomics, epigenomics and mouse modeling. In addition, we also aim to use single cell sequencing technologies (aim 3) to define the true epigenetic ground state of PGCs. In summary, identifying the epigenetic landscape of PGCs and the enzymes required to maintain it are critical to prioritizing future studies that disrupt the epigenome in PGCs during pregnancy, or the identification of epigenetic hot-spots in PGCs that could be tested for specific roles in infertility or transgenerational epigenetic inheritance in the future.