†††††††† Supervisor: Prof. Rudolf Winklbauer.
Vegetal Rotation in Xenopus laevis is an important force generating process during Gastrulation that plays an important part in tissue separation at the Brachetís cleft, as well as in the internalization of the mesoderm. Here we show that XRhoA plays a major role in vegetal rotation since a dominant-negative form thereof significantly blocks vegetal rotation at low and intermediate doses and freezes the embryos in the blastula stage at higher doses with little or no development thereafter. The blastopore never closes in these embryos. Moreover we also show that inhibition of ROK, a kinase acting downstream of RhoA in many cell mobility pathways, produces a phenotype with respect to vegetal rotation that is strikingly similar to the phenotype produced by DN-XRhoA. This suggests a possible downstream role of ROK in RhoA signalling during vegetal rotation.††††††††