XENOPUS FK 506-BINDING PROTEIN HOMOLOG INDUCES A SECONDARY AXIS IN FROG EMBRYOS, WHICH IS INHIBITED BY COEXISTING BMP-4 SIGNALING

FK 506-binding protein (FKBP) is an immunosuppressant mediator in mamm als, but its endogenous physiological function has yet to be determine d, Here we report a Xenopus homolog of FKBP, which is expressed at ear ly stages of development, Injection of synthesized Xenopus FKBP mRNA, as well as murine constitutively active calcineurin, induced a seconda ry axis in Xenopus embryos, while an FKBP mutant which does not bind t o calcineurin did not, This secondary-axis-inducing effect was inhibit ed 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 develo pment. (C) 1997 Academic Press.