The goal of this project is to understand how genes are controlled during development. We are studying the Drosophila gene, engrailed (en), which is important for proper segmentation of the embryo and also for formation of the adult. En expression patterns reflect the multiple roles it plays during development. En is expressed in stripes throughout embryonic development, as well as in specific cells in the developing nervous system, head and tail, and the progenitors of the adult tissue (in the imaginal discs). We are interested in how this complex expression pattern is regulated. By making transgenic flies which contain potential regulatory regions driving the expression of the reporter gene beta-galactosidase, we have found that sequences within a 1 kb en intron contain the information to give &n stripes early, but not late in development. This indicated that there are separate programs for controlling &n stripes at different times in development. The ability of the en intron to induce striped expression was dependent upon the type of promoter it was combined with. Promoter specificity was also seen when testing the activity at a homeodomain-binding site in embryos. These data together suggest that the expression pattern of any particular gene is the result of interactions between different elements within a regulatory region. Further studies indicate that the en regulatory region is full of redundancy: temporally overlapping programs for making stripes, more than one control element for striped expression at a particular time, multiple programs for keeping expression off between stripes. These studies are helping us to understand the complexity of controls that go into making an organism.
