Role of Septins in Developmental Regulation of Membrane Dynamics in yeast

Septins are a conserved family of cytoskeletal proteins. Proteins of this family are required for cytokinesis in both fungal and animal cells. During cytokinesis, and in post-mitotic cells, septins are often located near regions of active membrane extension. However, the molecular role of septins in membrane growth remains obscure. The prospore membrane is an intracellular membrane formed during sporulation in the yeast Saccharomyces cerevisiae, which packages the haploid nuclei produced by meiosis into spores. Septin behavior during prospore membrane formation resembles that of septins in higher cells; septins follow the leading edge of the membrane as it grows. This project focuses on illuminating the function of septins during formation of the prospore membrane. A combination of cell biological, genetic, and biochemical methods will be used to investigate this problem. The possible co-localization of septins with the protein phosphatase, Gip1p/Glc7p, as well as with proteins required for vesicle fusion will be examined. Additionally, proteins that can bind to both septins and the Gip1p subunit of the phosphatase will be sought. These experiments will shed light on the molecular function of septins in promoting the growth of the prospore membrane and the development of spores. Because of the evolutionary conservation of septins, insights gained into the function of these proteins in sporulating yeast cells may provide insight into septin function in higher cells.