Cloning and embryonic expression analysis of the mouse Gbx1 gene.

We report the cloning of a cDNA encoding the complete mouse Gbx1 coding region as well as a comparative expression analysis of Gbx1 and Gbx2 during murine development. Gbx1 is expressed first during gastrulation and later in a dynamic pattern in the central nervous system, including rhombomeres 3 and 5, optic vesicles, and the medial ganglionic eminence. Gbx1 expression is not upregulated in Gbx2 null homozygotes. Therefore, the only regions of potential genetic redundancy are where Gbx1 and 2 are normally coexpressed: the primitive streak, regions of the ventricular zone of the neural tube and the medial ganglionic eminence. Finally, we demonstrate that neither Gbx1 nor Gbx2 require FGF8 for expression during gastrulation, contrary to previous published reports.