Talk abstracts
Talk on Thursday 04:30-04:45pm submitted by Jillian Poska
Mechanisms of developmental reprogramming in the mammary stroma following in utero exposure to bisphenol A
Jilian M. Poska (Ohio State Biochemistry Program), Bader Albalawi (Department of Molecular Genetics, James Comprehensive Cancer Center), Madeline R. Price (Department of Molecular Genetics), Craig J. Burd
Abstract:
In utero exposure to endocrine disrupting compounds (EDCs) such as bisphenol A (BPA) can increase breast cancer risk in adulthood. BPA is known to alter mammary gland development and increase tumorigenesis in rodent models following in utero exposure. However, the mechanism by which BPA exerts this effect is unclear, making it difficult to understand the risk of exposure and design safer alternatives. Our lab has previously shown that in utero BPA exposure causes alterations to the tissue microenvironment that are conducive to tumor initiation. We thus sought to understand how these alterations are regulated and propagated from the womb to adulthood. In the present study, the mammary glands of embryonic or adult mice exposed in utero to BPA were used to isolate primary cells for ATAC-seq, qPCR, CUT&Tag, and single nuclei (sn) RNA sequencing to determine the epigenetic and cellular targets of BPA exposure. Our results indicate that in utero BPA exposure causes developmental reprogramming of mammary fibroblasts that persists into adulthood. qRT-PCR of collagen genes in fibroblasts and tissue collagen staining at different timepoints indicated that the increase in collagen caused by BPA is a developmentally regulated phenotype that presents during mammary gland maturation. We then analyzed the mammary gland epigenome in order to determine how in utero exposure can drive stromal phenotypes later in life. ATAC-seq revealed changes in chromatin accessibility throughout the fibroblast genome with the majority of these marks identified as enhancers via measurement of H3K4me1. Interestingly, regions of differential accessibility and H3K4me1 were seen proximal to genes known to be involved in fibroblast identity and differentiation, suggesting that BPA may exert its effects by reprogramming fibroblast heterogeneity. Confirming this finding, both snRNA-seq and flow cytometry revealed that BPA exposure reduces the percentage of Pi16+ progenitor-like fibroblasts in both the embryonic and the adult mammary gland. Together, these studies provide insight into how EDCs affect mammary gland development and increase breast cancer risk following in utero exposure via epigenetic reprogramming of the stroma.
Keywords: Fibroblast heterogeneity, developmental reprogramming, breast cancer