Making mesoderm--upstream and downstream of Xbra.

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