Miller 9419106 The mechanisms which regulate actin assembly are responsible for giving both form and function to cells. Actin is a protein which contributes to support structures within the cell and to mechansims which cause contraction, and consequently it is central to the existence and function of muscle cells. This proposal investigates the formation of, and regulatory mechanisms in, muscle cells. It would be technically impossible to conduct this studies on muscle cells from higher organisms because the ability for genetic manipulation is not possible. The PI uses Drosophila muscle development as a model system for the analysis. This system is the seminal system for genetic analysis in eukaryotic cells and can easily be employed for studies involving genetic manipulation. Since muscle cells organization is highly conserved among eukaryotics results from this system are anticipated to be easily extrapolated to other eukaryotic cells %%% The PI is interested how actin polymerization is controlled and how different actin-containing structures are formed and positioned in many different types of cells in eukaryotic organisms. Of particular interest is the process of muscle sarcomere assembly. A highly regular array of actin filaments is present, the location and organization of which is essential to muscle function. To understand how this regular array of actin filaments is generated, the PI is studying the actin binding protein, Cap Z. Cap Z is a heterodimeric protein (alpha and beta subunits) that binds to and blocks polymerization at the barbed (fast-growing) end of an actin filament in vitro. It is located at the Z-line of muscle in vertebrates, where the barbed end of actin filaments terminate and are anchored. Cap Z's properties in vitro and its localization in muscle suggest that it is a key component in controlling actin polymerization and/or anchoring actin filaments. However, definitive evidence for its function in vivo is lacking. The PI will obtain direct inform ation about how the actin filament organization of muscle is generated and in particular, the role of Cap Z, by making mutations in the gene that encodes one of the Cap Z subunits (beta) in the fruit fly, Drosophila. Drosophila is an attractive model system for studies on muscle function because its muscles are organized similarly to vertebrate muscles, yet it can manipulated using genetic techniques that are difficult or impossible in vertebrates. The PI will study the development, organization and function of muscles in Cap Z beta mutant flies and study Cap Z's distribution in flies that carry mutations in other sarcomere components. Through these studies the PI will determine how different proteins of the muscle interact to generate its structure. These studies should be applicable to a wide variety of organisms ***
