Understanding epigenetic remodeling in primordial germ cells

总结 生殖细胞负责将亲本的基因组和表观基因组从一代传递到下一代。 下一个尽管受精后基因组不会发生变化（DNA损伤的情况除外）， 哺乳动物中的表观基因组通过称为表观遗传重塑的过程而发生实质性改变。后 胚胎植入后，第二波主要的表观遗传重塑发生，这次是在新的特定的生殖细胞中， 胚胎细胞称为原始生殖细胞（PGCs）。第二波表观遗传重塑，大多数 据推测，从表观基因组中显著地消除DNA甲基化会消除任何获得的表观等位基因， 可能会给后代带来疾病在过去的五年里，我的实验室与该领域的同事一起， 发现小鼠和人类PGCs中的DNA甲基化重塑是不完整的，涉及阶段- DNA甲基化擦除和DNA甲基化保护的依赖性组合。在我们以前 在资助期间，我们发现，破坏PGC中阶段依赖性DNA甲基化重塑导致 生殖细胞丧失和不育。考虑到DNA甲基化重塑的正确分期对肿瘤的重要性， PGC的生物学和繁殖能力，我们接下来感兴趣的是潜在的染色质景观 负责动态DNA甲基化保护和擦除。这项工作的结果将大大 增强我们对生殖的表观遗传基础的认识。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（H3 K27 me 3）上游的多梳阻遏物复合物2（aim 1）和 H3 K9 me 3（aim 2）上游的三分基序28（Trim 28）在阶段依赖性DNA中起主要作用 PGCs中的甲基化重塑。为了解决这些假设，我们的目标是使用基因组学， 表观基因组学和小鼠建模。此外，我们还打算使用单细胞测序技术（AIM 3） 来定义原始生殖细胞真正的表观遗传基态总之，确定PGC的表观遗传景观 维持它所需的酶对于优先考虑未来破坏表观基因组的研究至关重要， 妊娠期间的PGC，或鉴定PGC中的表观遗传热点，可以检测特定的 在未来的不孕症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.