Exposure to Endocrine Disruptor Induces Transgenerational Epigenetic Deregulation of MicroRNAs in Primordial Germ Cells

In mammals, germ cell differentiation is initiated in the Primordial Germ Cells (PGCs) during fetal development. Prenatal exposure to environmental toxicants such as endocrine disruptors may alter PGC differentiation, development of the male germline and induce transgenerational epigenetic disorders. The anti-androgenic compound vinclozolin represents a paradigmatic example of molecule causing transgenerational effects on germ cells. We performed prenatal exposure to vinclozolin in mice and analyzed the phenotypic and molecular changes in three successive generations. A reduction in the number of embryonic PGCs and increased rate of apoptotic cells along with decrease of fertility rate in adult males were observed in F1 to F3 generations. Blimp1 is a crucial regulator of PGC differentiation. We show that prenatal exposure to vinclozolin deregulates specific microRNAs in PGCs, such as miR-23b and miR-21, inducing disequilibrium in the Lin28/let-7/Blimp1 pathway in three successive generations of males. As determined by global maps of cytosine methylation, we found no evidence for prominent changes in DNA methylation in PGCs or mature sperm. Our data suggest that embryonic exposure to environmental endocrine disruptors induces transgenerational epigenetic deregulation of expression of microRNAs affecting key regulatory pathways of germ cells differentiation.

在哺乳动物中，生殖细胞分化始于胎儿发育阶段的原始生殖细胞（Primordial Germ Cells，PGCs）。产前暴露于内分泌干扰物等环境有毒物质，可改变PGCs的分化状态与雄性生殖系发育，并引发跨代表观遗传紊乱。抗雄激素类化合物vinclozolin便是一类可对生殖细胞产生跨代影响的典型分子。本研究以小鼠为模型，开展产前vinclozolin暴露实验，并对连续三代个体的表型与分子变化进行了分析。在F1至F3代雄性个体中，均观察到胚胎期PGCs数量减少、凋亡细胞比例升高，以及成年雄性生育能力下降。Blimp1是调控PGCs分化的关键因子。本研究证实，产前vinclozolin暴露会失调PGCs中特定微小RNA（microRNAs）的表达，例如miR-23b与miR-21，进而在连续三代雄性个体中引发Lin28/let-7/Blimp1通路失衡。通过全基因组胞嘧啶甲基化图谱分析，本研究未在PGCs或成熟精子中发现DNA甲基化存在显著变化的证据。本研究数据表明，胚胎期暴露于环境内分泌干扰物，可引发跨代的微小RNA表达表观遗传失调，进而影响生殖细胞分化的关键调控通路。