Sunday, May 11, 2025
5/11/2025
Mechanisms of transgenerational epigenetic alterations induced by polybrominated biphenyls - 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.
HHS’ Tracking Accountability in Government Grants System (TAGGS) website provides access to detailed descriptions of grants, loans, aggregated direct payments and other types of financial assistance awarded by the HHS Operating Divisions (OPDIVs) and the Office of the Secretary Staff Divisions (STAFFDIVs).