... ). The present loss-of-function study shows that Bmp4 is a key positive regulator of the expression of ventral center genes, such as Sizzled and Bmp4 itself. Furthermore, epistatic studies showed that the ventralization caused by knockdown of Chordin can be compensated by loss of Bmp4 function ( Fig. 5...

... for the Bmp antagonist Chordin is mutated. We isolated the gene responsible for ogon by a positional cloning strategy and found that the ogon locus encodes a zebrafish homolog of Secreted Frizzled(Sizzled), which has sequence similarity to a Wnt receptor, Frizzled. Unlike other secreted Frizzled-related...

.... We provide evidence that sizzled , a secreted Frizzled-related protein expressed ventrally during and after gastrulation, functions in a negative feedback loop that limits allocation of mesodermal cells to the extreme ventral fate, with direct consequences for morphogenesis and formation of the blood...