CYP19A1 (aromatase) dominates female gonadal differentiation in chicken (Gallus gallus) embryos sexual differentiation

Cytochrome P450 Family 19 SubFamily A member 1 (CYP19A1) gene encodes an aromatase which regulates the sexual differentiation in vertebrates by initiating and maintaining 17β-Estradiol (E(2)) synthesis. Here, we described the spatiotemporal expression pattern of CYP19A1 and its functional role in the embryonic gonad development in amphoteric chickens (Gallus gallus). Results showed that CYP19A1 exhibited a sexually dimorphic expression pattern in female gonads early at embryonic day 5.5 (HH 28) and robustly expressed within the cytoplasm in ovarian medullas. Most importantly, we induced the gonadal sex reversal by ectopically delivering the aromatase inhibitor (AI) or estradiol (E(2)) into chicken embryos. To further explore the role of CYP19A1 in chicken embryonic sexual differentiation, we successfully developed an effective method to deliver lentiviral particles with CYP19A1 manipulation into chicken embryos via embryonic intravascular injection. The analysis of interference and overexpression of CYP19A1 provided solid evidences that CYP19A1 is both necessary and sufficient to initiate sex differentiation toward female in chicken embryos. Collectively, this work demonstrates that CYP19A1 is a crucial sex differentiation gene in the embryonic development, which provides a foundation for understanding the mechanism of sex determination and differentiation in chickens.