Actin Assembly in Non-Motile Cells

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Actin structures are critically important for functional and structural differences among the many cell types of multicellular organisms. The activities important for generation and maintenance of the different actin structures in different cell types are not well understood. This project will investigate the proteins and activities important for assembly of some of these structures. Using Drosophila as a model system, control of actin assembly into filament bundles will be studied in bristle cells. The adult sensory bristle relies on actin bundles, assembled at the proper time and proper place, for its specialized shape. Loss of function mutations in capping protein, a regulator of actin assembly, lead to actin bundle and, therefore, bristle shape defects. When amounts of other actin regulators that work with capping protein in bundle assembly are even slightly altered in capping protein mutant animals, striking changes in actin organization are observed. Thus, capping protein mutant animals provide a sensitive assay system for interactions among actin regulators. To accomplish these experiments, the amounts of different actin regulatory proteins will be altered using mutations in the genes that encode them or transgenes that increase copy number in sensitized [capping protein mutant] animals. The organization and assembly of actin bundles in fixed and live samples will be analyzed. All eukaryotic cells rely on actin structures to live and perform specialized functions. Because actin structures and their protein constituents are conserved across species, the results obtained from these studies will be generally applicable. This work will also have broad impact through training of undergraduates, graduate students, and post-doctoral fellows in the practice of science. In addition, these studies will generate collections of transgenic and mutant animals that are of use to a broad array of cell biologists interested in actin and in the development of different cellular specializations.