Change in Vertebrate Early Development

Duquesne University, Pittsburgh PA

Investigators

Abstract

0080028 Elinson Vertebrates share a common body plan, centered on the dorsal axis. Despite this similarity, early embryos of different vertebrates generate the common body plan in different ways. Frogs rely on molecules localized in the egg, while birds and mammals rely on later cell interactions. The evolution of the reptile/bird egg from the amphibian egg involved a huge increase in egg size, and this increase may have altered early development. To examine the impact of large egg size on early development, embryos of the Puerto Rican tree frog, Eleutherodactylus coqui, will be investigated. The egg of E. coqui is 20X the volume of that of Xenopus laevis, the frog whose development is best known. The evolutionary impact of this increase in size will be examined in three ways. First, alterations in egg organization will be investigated by determining the localization in E. coqui of RNAs, known to be important in patterning the X. laevis embryo. Second, the origin of the initial cell types, the germ layers, will be examined with the expectation that certain features of embryo patterning may resemble those of reptile or bird embryos. Finally, new evidence suggests that the dorsal axis arises differently in E. coqui than in X. laevis. An examination of these differences may show how the key element in vertebrate development can evolve. The results will demonstrate how an evolutionary increase in egg size affects mechanisms of early developmental patterning, and will suggest how the reptile/bird egg arose