GOOSECOID IS NOT AN ESSENTIAL COMPONENT OF THE MOUSE GASTRULA ORGANIZER BUT IS REQUIRED FOR CRANIOFACIAL AND RIB DEVELOPMENT

goosecoid (gsc) is an evolutionarily conserved homeobox gene expressed in the gastrula organizer region of a variety of vertebrate embryos, including zebrafish, Xenopus, chicken and mouse, To understand the rol e of gsc during mouse embryogenesis, we generated gsc-null mice by gen e targeting in embryonic stem cells, Surprisingly, gsc-null embryos ga strulated and formed the primary body axes; gsc-null mice were born al ive but died soon after birth with numerous craniofacial defects. In a ddition, rib fusions and sternum abnormalities were detected that vari ed depending upon the genetic background, Transplantation experiments suggest that the ovary does not provide gsc function to rescue gastrul ation defects, These results demonstrate that gsc is not essential for organizer activity in the mouse but is required later during embryoge nesis for craniofacial and rib cage development.