RELATIONSHIP BETWEEN ECTOPIC GERMINAL VESICLE BREAKDOWN IN XENOPUS OOCYTES AND DORSAL DEVELOPMENT OF THE EMBRYO

The early development of several species involves the segregation of c ytoplasmic components into different regions of the egg. In Xenopus zy gotes, a 30 degrees rotation displaces the central animal cytoplasm to the future dorsal side of the embryo. To elucidate the role of the ce ntral animal cytoplasm in dorsal determination, we induced germinal ve sicle breakdown (GVBD) closer to the equator by cold/centrifugation tr eatment of oocytes. Centrifugation moved the germinal vesicle to the c entripetal side; eggs with such displaced GVBD fertilized and began to develop normally. Dorsal embryonic structures tended to develop on th e GVBD side of the egg, but displacement of the GVBD was insufficient to rescue dorsal structures in axis-deficient embryos. The labeling of yolk platelets of oocytes with Trypan Blue revealed similar cytoplasm ic patterns in control and treated eggs. Furthermore, 67% of treated e ggs had Danilchik's swirl, indicative of the dorsal side, on the GVBD side. In conclusion, both the swirl and dorsal development tend to occ ur on the GVBD side of cold/centrifuged eggs; however, displaced GVBD cannot by itself determine dorsality.