45.1 Thursday, Jan. 5 Steroidogenesis and Steroid Hormone Signaling in the Chorioallantoic Membrane of the Domestic Chicken (Gallus gallus), the American Alligator (Alligator mississippiensis), and the Florida Red-belly Slider Turtle (Pseudemys nelsoni) ALBERGOTTI, L.C.*; HAMLIN, H.J.; MCCOY, M.W.; KOHNO, S.; GUILLETTE, JR., L.J.; University of Florida, Gainesville, FL; University of Maine, Orono, ME; University of Florida, Gainesville, FL; Medical University of South Carolina, Charleston, SC; Medical University of South Carolina, Charleston, SC email@example.com
As amniotes, mammals, reptiles, and birds share common extraembryonic membranes, which function in nutrient and gas exchange, waste removal and protection, and are critical for embryonic survival. In viviparous amniotes, extraembryonic membranes and maternal uterine tissues alike contribute to the placenta, an endocrine organ that synthesizes, transports and metabolizes hormones essential for embryonic development. Surprisingly, the endocrine role of extraembryonic membranes has not been investigated in oviparous amniotes despite similarities in their basic structure, function and shared evolutionary ancestry. To address this question, we examined steroidogenesis and steroid hormone signaling in the chorioallantoic membrane (CAM) of the chicken, American alligator and Florida red-belly slider turtle, representing three major amniote lineages that reproduce strictly by oviparity. We quantified mRNA expression of steroidogenic enzymes and steroid receptors in the CAM by quantitative PCR. In addition, protein expression of the progesterone receptor in the CAM was confirmed by immunohistochemistry. Furthermore, we found that the CAM could synthesize progesterone in vitro in the presence of a steroid precursor. Our data indicate that the oviparous CAM is steroidogenic and suggests that endocrine activity of extraembryonic membranes is not a novel characteristic of placental amniotes. Further, we hypothesize that endocrine activity of extraembryonic membranes might be an evolutionarily conserved characteristic of amniotes.