Mechanisms of transgenerational epigenetic alterations induced by polybrominated biphenyls

项目概要/摘要 了解环境诱导的表观遗传改变如何在哺乳动物生殖系中建立， 转代遗传，并有助于疾病的成年人，可以导致一个更完整的了解 以及新的预防保健机会。然而， 由于广泛的表观遗传重塑，表观表型的跨代遗传仍然令人困惑 发生在生殖细胞发育和受精后的生殖细胞中。Corces实验室的工作 表明，由于原始时期的环境扰动， 生殖细胞（PGC）的发育使某些区域免于DNA甲基化重塑，并导致持久的变化 染色质可及性。了解蛋白质组成、基因组分布和环境中 从配子到植入后胚胎诱导TF结合位点对于理解如何 生殖系表观突变可以承受表观遗传重塑，以及这些改变如何影响健康 的后代。为了解决这些问题，我们建议研究 多溴联苯（PBBs）。密歇根州的农村人口在受污染的环境中高度接触多溴联苯。 在1970年代对牲畜进行的放射性治疗，对子宫内接触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改变的机制仍然未知。无论这个质量 接触可能产生的跨代影响也是未知的。我对老鼠的初步研究表明， 在PGC发育过程中的暴露导致精子染色质中含有结合的差异可及位点 雄激素受体（Ar）的位点，持续transgeneratively。这种小鼠暴露导致类似于 母亲脂肪中的多溴联苯水平直接暴露于密歇根州居民，并导致女性F1的青春期提前 从密歇根州多溴联苯登记处直接接触的母亲的女儿中观察到的情况。 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 该项目是使用这种反映密歇根州多溴联苯暴露的小鼠模型来增加我们对多溴联苯的基本了解 与暴露的密歇根州人口直接相关的表型突变的传播。目标1将测试 假设精子染色质中跨代持久的Ar足迹是低甲基化的， Ar，并且侧接具有组蛋白变体和指示增强子的修饰的核小体。 此外，这一目标将检验这样的假设，即祖先的多溴联苯暴露也会导致不同的Ar足迹， 与精子中观察到的卵母细胞重叠。目的2将检验PBB诱导的TF位点 暴露在受精后从配子传递到胚胎。这些实验将产生 非常重要的结果，将填补我们对管理机制的理解的关键空白， 哺乳动物的跨代现象，将直接适用于对健康的理解 这些问题影响着数千名暴露在外的密歇根州居民及其后代。

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.