Meeting Abstract

P3.150  Tuesday, Jan. 6  Carbonic Anhydrase II Expression in the Chorioallantois of the Corn Snake, Pantherophis guttatus KHAMBATY, M.; ECAY, T.W.*; STEWART, J.R.; East TN State Univ; East TN State Univ; East TN State Univ stewarjr@etsu.edu

The shell of oviparous reptile eggs provides a substantial amount of calcium to the developing embryo. In corn snakes, the eggshell provides 28% of the calcium in hatchlings with the remainder coming from yolk. The chorioallantois contributes to calcium homeostasis during embryogenesis by mediating the transport of shell calcium to the embryo. Shell calcium is in the form of crystallized calcium carbonate deposited primarily on the outer surface. Our objective is to understand how the embryo regulates dissolution of mineralized shell calcium and its transport to the embryo during development. We hypothesize that cells of the chorioallantois secrete acid onto the eggshell thereby dissolving calcium carbonate crystals. Acid production is catalyzed by carbonic anhydrase II. Immunoblotting demonstrates an increase in carbonic anhydrase II expression throughout development in the chorioallantois but no detectable expression in the yolk sack. Increased carbonic anhydrase II expression in the chorioallantois is coincident with increased calbindin-D28K expression, a marker for calcium transport. Histochemical staining identifies carbonic anhydrase positive cells at the outer surface of the chorioallantois adjacent to the eggshell. Carbonic anhydrase II and calbindin-D28K immunohistochemisty are being used to determine if acid secretion and calcium transport occurs in the same or different cells. Supported by the NSF (IOB-0615695) and an APS Undergraduate Summer Research Fellowship.