Goosecoid regulates the neural inducing strength of the mouse node

The homeobox gene goosecoid was the first specific genetic marker of Speman n's organizer in vertebrate embryos to be discovered. In the frog, misexpre ssion of this gene by RNA injection produces duplication of the posterior a xis, for these reasons, the recent finding that mice lacking goosecoid func tion have no early axial defects was rather surprising. Here we assay the n eural inducing strength of wild-type and goosecoid-mutant mouse nodes by tr ansplantation into primitive streak stage chick embryos. Wild-type mouse no des strongly induce the neural-specific transcription factors Sox2 and Sox3 in the chick host. Homozygous goosecoid(-/-) nodes are severely impaired i n their ability to induce both genes. Heterozygous goosecoid(+/-) nodes ind uce Sox3 as well as wild-type nodes, but resemble -/- nodes in their limite d ability to induce Sox2. We propose that goosecoid does play a role in reg ulating the neural inducing strength of the node and that regulative mechan isms exist which mask the early phenotypic consequences of goosecoid mutati ons in the intact mouse embryo, (C) 1999 Academic Press.