Identification, mapping, and phylogenomic analysis of four new human members of the T-box gene family: EOMES, TBX6, TBX18, and TBX19.

Brachyury(T) is a mouse mutation, first described over 70 years ago, that causes defects in mesoderm formation. Recently several related genes, the T-box gene family, that encode a similar N-terminal DNA binding domain, the T-box, and that play critical roles in human embryonic development have been identified. It has been shown that human TBX5 and TBX3, if mutated, cause developmental disorders, Holt-Oram syndrome (OMIM 142900) and ulnar-mammary syndrome (OMIM 181450), respectively. We have identified four new human members of the T-box gene family, EOMES, TBX6, TBX18, and TBX19, and these genes have been mapped to different chromosomal regions by radiation hybrid mapping. The four T-box genes were classified into four different subfamilies and have also been subjected to phylogenomic analysis. Human EOMES maps at 3p21.3-p21.2. This Tbr1-subfamily gene is likely to play a significant role in early embryogenesis similar to that described for Xenopus eomesodermin. Human TBX6 maps at 16p12-q12. This Tbx6-subfamily gene is likely to participate in paraxial mesoderm formation and somitogenesis in human embryo. TBX18 is a novel member of the Tbx1 subfamily that maps at 6q14-q15. Two subgroups, TBX1/10 and TBX15/18 subgroups, could be distinguished within the Tbx1 subfamily. TBX19 is an orthologue of chick TbxT and maps at 1q23-q24. The genomic organization of TBX19 is highly similar to that of human T(Brachyury), another human member of the same subfamily.