Vertebrate-specific Transcriptional Signaling

Montana State University, Bozeman MT

Investigators

Abstract

0090884 Edward Schmidt The TATA-binding protein, TBP, is a component of the basal transcription machinery. Comparison of tbp gene sequences from diverse species reveals a C-terminal core that is highly conserved in all phyla. In addition, all tetrapod vertebrate animals share a nearly identical N-terminal domain that is either absent from or unrelated to sequences in other eukaryotes including pre-vertebrate deuterostomes (e.g. echinoderms). The hypothesis of this project is that the TBP N-terminus co-evolved with a novel set of structural genes and their transcriptional regulators to allow acquisition of some vertebrate-specific function. Using targeted mutagenesis, a line of mice lacking most of the TBP N-terminus has been generated. This region of the protein is dispensable for cell survival, proliferation, differentiation, and the assembly of most tissues and organs; however, development of mutant embryos arrests in mid-gestation. In this project, the genetic pathways acting through the TBP N-terminus will be characterized. The PI's laboratory is in a unique situation to address these questions because, when candidate members of the pathway are identified, the mutant mice provide the ideal system within which to verify expression and activity. Perhaps the three most important advances that occurred between early chordates and tetrapod vertebrates are: 1) evolution of the vertebrate body plan; 2) evolution of the adaptive immune system; and 3) specializations for terrestrial life. The spontaneous abortions in the mutant mice are consistent with defects in any of these three processes. Global analysis of differential gene expression between mutant and wild type embryonic fibroblasts, embryos, and placentas is being performed on samples harvested at a stage immediately preceding manifestation of the pathological phenotype. The expression of candidate target genes is being verified by direct analysis in mutant and wild type embryos. As a result of these analyses, this project will first, further resolve the evolutionary timing of acquisition of the TBP N-terminus, and then determine what genes are mis-regulated in mice lacking this region. This study is expected to provide important advances toward an understanding of vertebrate evolution, gene regulation, and the mechanisms of transcription.