||Dorsal closure in the fruit fly Drosophila melanogaster is a complex morphogenetic process dependent upon three embryonic tissues: the lateral epidermis, leading edge epidermis, and amnioserosa. Additionally, the Jun N-terminal Kinase (JNK) and Decapentaplegic (Dpp) signaling cascades are required for the cytoskeletal rearrangements and cell morphological changes necessary for closure. Embryos failing to complete dorsal closure are identifiable based on their characteristic "dorsal-open" phenotype. We have identified a new member of the dorsal-open group - l(3)7E103 - as a recessive embryonic lethal mutant. The dorsal-open phenotype is fully penetrant and leading edge morphological defects are evident when using a leading edge marker. l(3)7E103 potentially plays a cytoarchitectural role in organizing the leading edge. Only one mutant exists, and thus it is critical to clone the gene product in which the lesion exists in order to understand the molecular role of l(3)7E103. Genetic methods have been employed to map the location of the l(3)7E103 lesion, including complementation and recombination mapping. These efforts have narrowed the potential locations of the lesion to three small haploinsufficient gaps near the centromere of the third chromosome; there are over 100 potential gene candidates in these regions. Further work will narrow the region to approximately 10-30 gene candidates, and these will be used for rescue of the mutant phenotype in germline transformants. Identification of l(3)7E103 will significantly impact and enhance our understanding of the complexities of dorsal closure and hence shed light upon analogous human developmental events, such as neural tube closure and wound healing.