The prechordal midline of the chondrocranium is defective in Goosecoid-1 mouse mutants

Gsc-1 expression marks cells with Spemann organizer, or axis-inducing, activity in the vertebrate gastrula. Gsc-1 knockouts, however, did not display phenotypes related to the early phase of expression. In this paper, additional phenotypes for the Gsc-1 mouse mutant are presented. Examination of the base of the cranium in the dorsal view revealed fusions and deletions in the midline of the prechordal chondrocranium. These defects were correlated with the sites of expression of Gsc-1 in the prechordal plate/foregut endoderm in the day 7.5/8.5 embryo. Gsc-1 expression in proximal limb buds was correlated with malformations of the shoulder and hip articulations. In addition, ribs in the seventh cervical vertebra were observed with low penetrance. The role of Gsc-1 during gastrulation and axial development is discussed in relation to possible compensatory interactions with other genes such as HNF-3beta and the recently identified Gsc-2 and Gsc-3 genes.