Analysis of body axix formation using Xenopus egg fragments as assay system for investigating gene functions

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In this project, we obtained the following three results.1. Ablation of more than 60% of vegetal cytoplasm from newly fertilized Xenopus eggs results in the development of permanent blastula-type embryos (PBEs) which cleave normally and develop into atypical epidermis. We found that PBEs did not contain any maternal Veg-T, but regenerated Veg-T translocation after injection of marginal cytoplasm.2. We found that both BMP-3b and BMP-3 dorsalize Xenopus embryos, but act as dissimilar antagonists within the BMP family. BMP-3b injected into Xenopus embryos triggered secondary head formation in an autonomous manner, whereas BMP-3 induced aberrant tail formation. At the molecular level, BMP-3b antagonized nodallike proteins and ventralizing BMPs, whereas BMP-3 antagonized only the latter.3. Using PBEs (described above) Gastrulating Non-axial Embryos (GNEs) which were deleted of 20-40% cytoplasm (relative surface area), a series of Einsteck transplantation experiments were carried out to investigate mechanisms controlling anteroposterior patterning during early Xenopus development. We have shown that anteroposterior patterning in Xenopus is not achieved solely by the dorsal marginal zone (the Spemann organizer) but instead by a synergistic mechanism of the dorsalizing domain (DMZ) and the posteriorizing domain (the entire vegetal half except for the DMZ).