Xenopus FK 506-binding protein homolog induces a secondary axis in frog embryos, which is inhibited by coexisting BMP 4 signaling

Abstract

FK 506-binding protein (FKBP) is an immunosuppressant mediator in mammals, but its endogenous physiological function has yet to be determined. Here we report a Xenopus homolog of FKBP, which is expressed at early stages of development. Injection of synthesized Xenopus FKBP mRNA, as well as murine constitutively active calcineurin, induced a secondary axis in Xenopus embryos, while an FKBP mutant which does not bind to calcineurin did not. This secondary-axis-inducing effect was inhibited when FKBP was coinjected with Xmad 1 or XBMP 4 mRNA. These results suggest that FKBP modifies BMP 4 signalling by recruiting calcineurin and may have an important role in axis formation during Xenopus development.