Hi my name is Kristen Correia. I am a postdoc investigating how Hox gene expression is controlled within the embryonic mesoderm. The Hox genes pattern the mesoderm along the anterior posterior axis. Derivatives of the mesoderm, such as the bones of the vertebral column display anterior transformations in Hox knockouts, whereas posterior transformations result from overexpression. This demonstrates the importance of regulation of expression pattern within this tissue. The genes of the Hox complex are expressed in a nested, collinear pattern with expression boundaries of genes at the 3’ end lying most anterior, and of genes at the 5’ end lying most posterior. Potential enhancer elements that drive expression of the reporter beta-galactosidase are tested using pronuclear injection to generate mouse transgenic lines. Reporter patterns that temporally and spatially match the endogenous genes expression patterns have been identified for Hoxb1 and Hoxb9. I am working with a new postdoc in the lab, Tara Alexander, to compare the sequence of these enhancers across species, identify conserved regions, and look for conserved potential transcription factor binding sites. These transcription factor binding sites are tested by deletion within the reporter and analysis of the reporter expression in mouse transgenics. Known regulators of the Hox genes include Cdx, Fgfs, Retinoic acid, Wnts, and auto and cross regulation by Hox genes themselves. Dominant active and negative forms of these proteins are being injected to test whether they shift the expression of the Hox reporters. Our experiments will allow us to determine which of these regulators work directly on the enhancer elements.