Estrogenic-like compounds severely disturb germ cell formation in Japanese quail

During avian germ cell formation, primordial germ cells (PGCs) differentiate into prospermatogonia in testicular seminiferous tubules or into oogonia in the ovarian cortex in late-stage embryos. Although estrogenic endocrine-disrupting chemicals (EDCs) have been suggested to affect the differential fate of avian germ cells, there is currently no established method to examine the effects of EDCs on the differentiation potential of germline cells due to large amount of unidentified proteins present in avian germ cells. Regarding reliable molecular probes for the detection of germ cells that differentiated from the PGCs of Japanese quail, the prospermatogonium and oogonium, respectively, integrin beta1 (ITGB1), insulin-like growth factor 2-binding protein 1 (IGF2BP1), and stimulated by retinoic acid 8 (STRA8) were identified as marker proteins by RNA-seq and liquid chromatography tandem mass spectrometry analyses. This study also showed disordered germ cell formation in ovo following the addition of 100 nmol of diethylstilbestrol (DES), o, p'-dichloro-diphenyl-trichloroethane (o,p'-DDT), ethinylestradiol (EE), and bisphenol A. DES directly induced severe damage in germline cells by inhibiting their proliferation and subsequent differentiation into ITGB1-positive germ cells in males independently of disordered gonadal differentiation, while DES and o,p'-DDT decreased the number of female germ cells. In addition, EE toxicity was characterized by a reduction in IGF2BP1-germ cells due to the partial ovarian-like differentiation of male gonads. Furthermore, all EDCs exerted deleterious effects on female ovaries, which restricted differentiation into STRA8-positive oogonia. These results demonstrate that the bioaccumulation of estrogenic EDCs in birds during incubation may reduce male and female fertility.