963034 Finkelstein The objective of this project is to determine the molecular basis of pattern formation during Drosophila head development. Studies of invertebrates and vertebrates suggest that head and trunk regions are patterned by different genetic mechanisms. Dr. Finkelstein will determine the pathway of head development, and compare it to previously described paradigms of trunk specification. Dr. Finkelstein has previously shown that the segment polarity genes hedgehog (hh) and wingless (wg) specify the identities of specific regions of the head of the adult fruitfly. In the experiments proposed here, he will analyze the expression and function of hh and wg in the imaginal discs that give rise to the head. In addition, he will study the molecular interactions of hh and wg with the genes decapentaplegic, orthodenticle, and engrailed, which are also involved in head formation. Finally, he will use genetic methods to identify and analyze new loci required in the developing head. By using the combination of molecular and genetic approaches possible in Drosophila, he will systematically determine the pathway of head development. Since many of the genes in this pathway are evolutionarily conserved, his results will form a foundation for studying head formation in other animals. Ultimately, such studies will be critical for understanding how genetic defects perturb normal pathways of development.