The role of Xenopus developmental biology in unraveling Wnt signalling and antero-posterior axis formation.

Wnt signalling plays an eminent role in development, stem cell growth, and tissue homeostasis. Much of what we know about Wnt signalling, we owe to research in developmental biology. Here I review some salient discoveries in the older literature, beginning with the Lithium experiments in sea urchin by Curt Herbst in the 1890ies, when unknown to him he observed the gradual effects of Wnt overactivation upon embryonic axis formation. After revisiting key discoveries into Wingless signalling in Drosophila, I examine the role that the Xenopus embryo has played as model system in this regard. Not only were components of the Wnt cascade dissected and secreted Wnt antagonists discovered in Xenopus, but it also played a key role in unveiling the evolutionary conserved role of Wnt signalling in primary body axis formation. I conclude that Xenopus developmental biology has played a major role in elucidating the mechanisms of embryonic Wnt signalling.