The research proposed in this grant addresses the question of how genes control the process of pattern formation in developing embryos. This research will determine the role of the hedgehog gene of Drosophila in establishing the parasegmental boundary, which is one of two developmental field boundaries established during segmentation of the early Drosophila embryo. The pattern of expression of hedgehog, as judged by immunohistochemistry, will be compared with that of other segment polarity genes involved in this process, both during the establishment of this boundary in embryogenesis and in its maintenance in the imaginal discs. Controls on the regulation of hedgehog expression, both in establishing and maintaining its spatial expression pattern (as judged by the distribution of its RNA and protein products) and on the developmental regulation of splicing of the hedgehog RNA, will be investigated. Finally, the nature of the hedgehog product, and the identification of possible roles of the gene's function, will be identified by isolation and sequencing of complete cDNAs from the hedgehog locus.