Locating the Enhancer Region for Singles Bar Expression in Drosophila melanogaster myoblasts

In Drosophila melanogaster, singles bar (sing) codes for a MARVEL domain trans-membrane protein, found in both founder cells and fusion-competent myoblasts, that is essential for myoblast fusion. Many of the molecules that control myoblast fusion have yet to be identified; therefore, we have a limited understanding of how myoblasts fuse. However, we know that the two-staged myoblast fusion process to yield multinucleated myofibers is common to both flies and humans. During the first stage of myoblast fusion, fusion-competent myoblasts fuse to a founder cell to form a pre-fusion complex. The second stage involves subsequent fusions of additional fusion-competent myoblasts to form a multinucleated myofiber. Without sing expression, however, progression does not occur past the myoblast pre-fusion complex. Sing’s role in controling myoblast fusion is not fully understood; however, there are several myocyte enhancer factor 2 (MEF2) binding sites near the region of sing that may initiate its transcription. There are three potential MEF2 binding sites within the introns of sing itself and five sites within a 5,300 base pair segment upstream of sing. This study tested whether these regions contained enhancers for sing by fusing the potential enhancer regions into a lacZ gene. We hypothesize that our enhancer region is within our 5,300 base pair segment upstream of sing; in this case, transgenic flies containing the enhancer-lacZ fusion will produce Beta-galactosidase. These studies will enhance our understanding of how sing expression and myoblast fusion are controlled.