An ancient family of embryonically expressed mouse genes sharing a conserved protein motif with the T locus.

The T locus encodes a product with DNA binding activity that is likely to play a role in the development of all vertebrate organisms. We have identified and characterized a novel family of mouse genes that share a protein motif, the T-box, with the prototypical T locus. The T-box domain of the T locus co-localizes with its DNA binding activity. Each T-box gene is expressed in a unique temporal and spatial pattern during embryogenesis. Phylogenetic analysis suggests that at least three T-box genes were present in the common ancestor to vertebrates and invertebrates. Thus, members of the T-box family could have played a role in the evolution of all metazoan organisms.