International Mammalian Genome Society

G25 Vertebrate T-Box Genes: A Phylogenetic Framework for the Study of Important Developmental Regulators

Ilya Ruvinsky, Jeremy J. Gibson-Brown, and Lee M. Silver. Lewis Thomas Laboratory, Department of Molecular Biology, Princeton University, Princeton, NJ 08544

The T-box genes constitute a family of transcription factors characterized by a 180-amino acid domain with sequence homology to the classical Brachyury (T) gene. Over the last several years much attention has been devoted to the study of these genes as important developmental regulators in a wide variety of animals. Recently mutations of T-box genes were identified which result in developmental abnormalities in humans, mice and zebrafish revealing diverse and essential functions played by these genes during embryogenesis.

To gain a phylogenetic perspective on the potential functions of T-box family members, we conducted a systematic screen for these genes in the genomes of a teleost, Danio rerio, and a primitive chordate - amphioxus, Branchiostoma floridae. We were able to uncover a number of T-box genes in both of these species. A phylogenetic analysis suggested that a two-fold expansion within the family occurred subsequently to the divergence of the most recent common ancestor of jawed vertebrates from a primitive chordate relative. The size of the family has remained stable thereafter, aside from occasional lineage-specific duplications (such as the one in teleosts). Therefore, our findings imply that contrary to a commonly held belief a single genome duplication may have occurred early in vertebrate evolution. Furthermore, we will highlight an evolutionary approach to the study of T-box genes in vertebrate development.