BPA-induced Differential Methylation of the Androgen Receptor Promoter CpG Island in Medaka Germline and Somatic Cells

The androgen receptors (Ar) are fundamental mediators of androgen signaling, critical for male fertility. Environmental endocrine disruptors (EEDs) can impair male fertility; however, it remains unclear whether EED-induced fertility impairments are linked to DNA methylation alterations in the ar promoter within germ cells, or if a germline-to-soma transfer of these epigenetic profiles affect ar transcription in the testis leading to fertility impairment. To address this, we exposed medaka (Oryzias latipes) to bisphenol A (BPA, 100 µg/L, an EED) and determined fertility defects, testis histology, DNA methylation alterations in the CpG island of arα promoter, and mRNA levels of arα mRNA in the testicular germ cells and soma. Reduced fertility was observed in F0 and F2 generations, which was accompanied by alterations in the testicular tubular structure and germ cell landscape. In F0 males, the testicular germ cells maintained increased levels of DNA methylation on the CpG island of the arα promoter at the ground state of epigenetic reprogramming of germ cells (15 days post-fertilization, dpf) and as such in sperm. In F2 males, testis showed elevated expression of DNA methyltransferase enzyme genes. F2 germ cells maintained significantly higher levels of DNA methylation. The elevated DNA methylation profile was maintained in testicular somatic cells and correlated with significantly decreased arα mRNA levels. The present results demonstrate that ancestral BPA exposure induces transgenerational male subfertility by altering the methylation profile of arα promoter and gene expression, highlighting the profound risk EEDs pose to reproductive health in vertebrates and population stability in wildlife.