Prenatal exposure to benzo[a]pyrene depletes ovarian reserve and masculinizes embryonic ovarian germ cell transcriptome transgenerationally

Abstract

People are widely exposed to polycyclic aromatic hydrocarbons, like benzo[a]pyrene (BaP). Prior studies showed that prenatal exposure to BaP depletes germ cells in ovaries, causing earlier onset of ovarian senescence post-natally; developing testes were affected at higher doses than ovaries. Our primary objective was to determine if prenatal BaP exposure results in transgenerational effects on ovaries and testes. We orally dosed pregnant germ cell-specific EGFP-expressing mice (F0) with 0.033, 0.2, or 2 mg/kg-day BaP or vehicle from embryonic day (E) 6.5–11.5 (F1 offspring) or E6.5–15.5 (F2 and F3). Ovarian germ cells at E13.5 and follicle numbers at postnatal day 21 were significantly decreased in F3 females at all doses of BaP; testicular germ cell numbers were not affected. E13.5 germ cell RNA-sequencing revealed significantly increased expression of male-specific genes in female germ cells across generations and BaP doses. Next, we compared the ovarian effects of 2 mg/kg-day BaP dosing to wild type C57BL/6J F0 dams from E6.5–11.5 or E12.5–17.5. We observed no effects on F3 ovarian follicle numbers with either of the shorter dosing windows. Our results demonstrate that F0 BaP exposure from E6.5–15.5 decreased the number of and partially disrupted transcriptomic sexual identity of female germ cells transgenerationally.