The objective of this research project is to analyse how cells respond to a morphogen gradient. The group of J.B. Gurdon has recently used the Xenopus embryo to create a model system to study the general spatial properties of cellular signaling and response to a morphogen gradient. There is evidence that the artificial concentration gradient of activin they created is achieved by passive diffusion and that cells respond directly to the forming morphogen gradient and can assess morphogen concentration continuously (Gurdon, J.B. et al., Nature 371,487492, 1994; Gurdon, J.B. et al., Nature 376, 520-521, 1995).
In this project, using J.B. Gurdon's assay system for analysing response to a morphogen gradient, we will try to determine: 1) whether activin is required throughout the gradient or whether a non activin signaling molecule is used for distant signal transmission by analysing gene response in distant cells which are dominant negative for the activin receptor. 2) how cell recognize their position in the activin morphogen gradient by analysing the effect of activin receptor overexpression on the spatial arrangement of gene expression 3) how the expression of one gene in the gradient (Xbra) is influenced by that of other early mesodermal genes (Xgscd) by study the effect of overexpression of Xgscd on the spatial arrangement of Xbra expression.