Expression of calbindin-D28K by yolk sac and chorioallantoic membranes of the corn snake,Elaphe guttata

The yolk splanchnopleure and chorioallantoic membrane of oviparous reptiles transport calcium from the yolk and eggshell to the developing embryo. Among oviparous amniotes, the mechanism of calcium mobilization to embryos has been studied only in domestic fowl, in which the mechanism of calcium transport of the yolk splanchnopleure differs from the chorioallantoic membrane. Transport of calcium is facilitated by calbindin-D28K in endodermal cells of the yolk splanchnopleure of chickens but the chorioallantoic membrane does not express calbindin-D28K. We used immunoblotting to assay for calbindin-D28K expression in yolk splanchnopleure and chorioallantoic membrane of the corn snake, Elaphe guttata, to test the hypothesis that the mechanism of calcium transport by extraembryonic membranes of snakes is similar to birds. High calbindin-D28K expression was detected in samples of yolk splanchnopleure and chorioallantoic membrane during late embryonic stages. We conclude that calbindin-D28K is expressed in these extraembryonic membranes to facilitate transport of calcium and that the mechanism of calcium transport of the chorioallantoic membrane of the corn snake differs from that of the chicken. Further, we conclude that calbindin-D28K expression is developmentally regulated and increases during later embryonic stages in the corn snake. J. Exp. Zool. (Mol. Dev. Evol.) 302B:000–000, 2004. © 2004 Wiley-Liss, Inc.