Making mesoderm - upstream and downstream of Xbra

The mesoderm of the amphibian embryo is formed through an inductive interac tion in which cells of the vegetal hemisphere of the embryo act on overlyin g equatorial cells. My laboratory is studying the Brachyury gene, which pla ys a key role in this interaction, being both necessary and sufficient for normal mesoderm formation, In this article I describe our attempts to under stand how Xenopus Brachyury (Xbra) is activated in the right cells at the r ight time, and then to understand how Xbra exerts its effects.