Disruption of tissue growth and patterning is a common step in the development of cancer, and proper tissue morphology depends upon combined input from intercellular signaling pathways and region-specific transcription factors. In Drosophila melanogaster the protein Ultrabithorax (Ubx), a region-specific transcription factor and member of Hox family of homeodomain proteins, restricts growth of hindwing (haltere) tissue in part by modulating the expression of several components of the mitogenic Decapentaplegic (Dpp) pathway. The goal of this project is to identify target genes and transcriptional regulatory elements in the Drosophila genome that are directly regulated by Ubx in the haltere;three experimental approaches will be used to accomplish this goal. First, a novel gene expression profiling .method will be used to analyze regional gene expression differences in serially homologous Ubx-expressing (haltere) and non-expressing (wing) tissues. The second step will use chromatin immunoprecipitation and DamID in combination with Drosophila genome tiling arrays to determine the DNA regions that are directly bound by Ubx in the haltere. Together, these experiments will allow the identification of direct Ubx target genes in the haltere on a genome-wide scale. The third step in this analysis will be to use Cognate Site Identity (CSI) microarray technology to characterize the DNA-binding specificity of Ubx, both as a monomer and in conjunction with the Hox cofactors Extradenticle (Exd) and Homothorax (Hth). This will permit exploration of the DNA sequences to which Ubx can and cannot bind, and, in combination with the first two steps, should allow a better understanding of a Hox regulatory network. Follow-up analysis on a subset of Ubx target genes, particularly those likely to be involved in growth regulation, will include the validation of their expression patterns in both the wing and haltere and functional analysis using standard Drosophila genetic approaches. Public Health Relevance: The Hox proteins and many of the signaling molecules controlling growth, proliferation and morphogenesis are conserved between Drosophila and humans;the goal of this research is to provide insight into the mechanisms by which a Hox transcription factor regulates tissue growth. Ultimately, a detailed description of how Hox proteins regulate tissue growth during normal development will be crucial to understanding their role when growth is misregulated in diseases states such as cancer.