Phenotypic effects in Xenopus and zebrafish suggest that one-eyed pinhead functions as antagonist of BMP signalling

Zebrafish one-eyed pinhead (oep) is essential for embryonic axis and dorsal midline formation by promoting Nodal signalling and is thought to act as a permissive factor. Here we describe that oep elicits profound phenotypic e ffects when overexpressed in Xenopus and zebrafish. In Xenopus, wild-type o ep inhibits mesoderm induction, disrupts axis formation and neuralizes anim al caps. A secreted Oep dorsoanteriorizes and neuralizes Xenopus embryos in dicative of:BMP inhibition. In zebrafish, misexpression of smad1 in oep mut ant embryos also reveals an interaction of oep with BMP signalling. Further more, the phenotypic effect of nodal overexpression can be rescued by coexp ression of oep both in Xenopus and zebrafish. Taken together, our results s upport an interaction between oep and nodal but they suggest also (1) that the role of oep in Nodal signalling may include negative as well as positiv e regulation, (2) that oep is able to function in an active fashion and (3) that oep exerts a regulatory effect on the BMP signalling pathway. (C) 200 0 Elsevier Science Ireland Ltd. All rights reserved.