ИСТИНА

Since it has been shown that the fragment of the dorsal blastopore lip of an amphibian gastrula is able to instruct the surrounding cells to form a body axis, the molecular nature of the organizer capacity has attracted much attention among researchers. Earlier we have demonstrated that a fragment of the blastopore lip of the Nematostella gastrula can induce a second body axis upon transplantation into the blastocoel roof of the recipient gastrula, while no other gastrula tissue possesses this capacity. Here we show that, like in vertebrates, the crucial signal leading to the induction of the ectopic axis in Nematostella is a Wnt molecule. By a combination of overexpression, transplantation and inhibitor treatment, we identify which of the multiple Wnt ligands are capable of inducing ectopic body axes. We also show that the formation of the secondary "directive" body axis in Nematostella requires an initial Wnt signal. Finally, we demonstrate that once established, the directive axis stops being dependent on changes in the Wnt/beta-catenin signaling. In summary, our data allow to conclude that blastoporal organizers in animals as distant as sea anemones and vertebrates are homologous.