Mechanisms of transgenerational epigenetic alterations induced by polybrominated biphenyls

项目摘要/摘要 知道环境诱导的表观遗传改变是如何在哺乳动物生殖系中建立的， 跨代遗传，并导致成人的疾病，可以导致更完整的理解 病理生理学以及新的预防保健机会。然而，潜在的机制是 由于广泛的表观遗传重塑，表型的跨代遗传仍然令人困惑 这发生在生殖细胞发育期间和受精后的生殖系中。在科尔塞斯实验室工作 提示在原始时期由于环境扰动引起的异常转录因子(TF)的占据 生殖细胞(PGC)的发育保护区域不受DNA甲基化重塑的影响，并导致持久的变化 在染色质可及性方面。了解环境中的蛋白质组成、基因组分布和命运 诱导从配子到植入后胚胎的转铁蛋白结合位点是理解如何 生殖系表观突变可以抵抗表观遗传重塑，以及这些变化如何影响健康 后代人的。为了解决这些问题，我们建议研究以下因素的跨代影响 多溴联苯(PBBS)。密歇根州的农村人口高度暴露于受污染的多溴联苯 在20世纪70年代，在子宫中暴露的个人造成了许多不利的健康后果，包括 青春期提前和其他生殖变化的机制尚不清楚。无论这个质量 暴露可能会产生跨代影响也是未知的。我对小鼠的初步研究表明，PBB 在PGC发育过程中暴露导致精子染色质中含有结合的差异可及部位 雄激素受体(AR)的位置是代代性存在的。这种老鼠暴露会导致类似的 母亲脂肪PBB水平直接暴露于密歇根州居民，并导致女性F1提前青春期 从密歇根州PBB登记处直接接触的母亲的女儿身上观察到的小鼠后代。 重要的是，在未暴露的F3代小鼠中也观察到青春期提前。建议的目标是 项目是使用这个反映密歇根多溴联苯暴露的小鼠模型来增加我们对 与暴露的密歇根州人口直接相关的基因突变的传播。目标1将测试 假设精子染色质中跨代持续存在的Ar足迹是低甲基化的，受 AR，侧翼是具有组蛋白变体和修饰的核小体，表明增强剂。 此外，这一目标将检验这一假设，即祖先接触PBB也会导致不同的Ar足迹 与精子中观察到的卵母细胞重叠的卵母细胞。目标2将检验PBB诱导的转铁蛋白位点的假设 受精后，暴露从配子传递到胚胎。这些实验将产生 非常重要的结果，将填补我们对治理机制的理解的一个关键空白 哺乳动物中的跨代现象将直接适用于对健康的理解 影响到数千名受影响的密歇根州居民及其后代的问题。

PROJECT SUMMARY/ABSTRACT Knowing how environmentally-induced epigenetic alterations are established in the mammalian germline, transgenerationally inherited, and contribute to disease in the adult, can lead to a more complete understanding of pathophysiology as well as novel preventive care opportunities. However, the mechanisms underlying the transgenerational inheritance of epiphenotypes remain perplexing due to the extensive epigenetic remodeling that happens in the germline during germ cell development and after fertilization. Work from the Corces lab suggests that aberrant transcription factor (TFs) occupancy due to environmental perturbations during primordial germ cell (PGC) development shields regions from DNA-methylation remodeling and results in lasting changes in chromatin accessibility. Understanding the protein makeup, genomic distribution, and fate of environmentally induced TF binding sites from the gametes to the post-implantation embryo is essential to understand how germline epimutations can withstand epigenetic remodeling, and how these alterations can influence the health of later generations. To address these issues, we propose to examine the transgenerational effects of polybrominated biphenyls (PBBs). Rural populations in Michigan were highly exposed to PBBs in contaminated livestock in the 1970s, resulting in numerous adverse health outcomes in individuals exposed in utero, including earlier puberty and other reproductive alterations by mechanisms that remain unknown. Whether this mass exposure could have transgenerational effects is also unknown. My preliminary mouse studies show that PBB exposure during PGC development leads to differentially accessible sites in sperm chromatin containing binding sites for the androgen receptor (Ar) that persist transgenerationally. This mouse exposure results in similar maternal adipose PBB levels as directly exposed Michigan residents, and leads to early puberty in female F1 mouse offspring, as observed in daughters of directly exposed mothers from the Michigan PBB registry. Importantly, early puberty is also observed in the unexposed F3 generation in mice. The goal of the proposed project is to use this mouse model reflecting the Michigan PBB exposure to increase our basic understanding of the transmission of epimutations with direct relevance to the exposed Michigan population. Aim 1 will test the hypothesis that transgenerationally persistent Ar footprints in sperm chromatin are hypomethylated, bound by Ar, and are flanked by nucleosomes possessing histone variants and modifications indicative of enhancers. Further, this aim will test the hypothesis that ancestral PBB exposure also results in differential Ar footprints in oocytes that overlap with those observed in sperm. Aim 2 will test the hypothesis that TF sites induced by PBB exposure are transmitted from the gametes to the embryo after fertilization. These experiments will generate highly significant results that will fill a critical gap in our understanding of the mechanisms governing transgenerational phenomena in mammals that will be directly applicable to the understanding of the health problems affecting thousands of exposed Michigan residents and their descendants.