Head and trunk in zebrafish arise via coinhibition of BMP signaling by bozozok and chordino

Spatial variations in the levels of bone morphogenetic protein (BMP) signal ing are a critical determinant of dorsoanterior-ventroposterior pattern in vertebrate embryos. Whereas BMP overexpression abolishes both head and trun k development, known single and double loss-of-function mutations in BMP in hibitors have less dramatic effects. We report that combining mutations in the zebrafish genes bozozok and chordino causes a synergistic loss of head and trunk, whereas most cells express ventro-posterior markers and develop into a tail. Genetic inactivation of BMP signaling fully suppresses these d efects. Thus, a remarkably simple genetic mechanism, involving a coinhibiti on of BMP function by the partially overlapping bozozok and chordino pathwa ys is used to specify vertebrate head and trunk.