MEMBRANE ORGANIZATION AND DYNAMICS IN MAMMALIAN SPERM

In somatic cells, membrane rafts are dynamic, existing in various time and space scales. The transient nature of these membrane microdomains and the use of detergents or multivalent probes/cross-linkers to isolate or visualize them have incited controversy in this field. In the following studies, I demonstrate for the first time in live spermatozoa, the presence of a micrometer-scale, stable domain in the plasma membrane enriched in sterols and the glycosphingolipid GM1 at physiological temperature. This sterol-enriched membrane platform is positioned to regulate the acquisition of sperm fertilization competence. I examine the properties of this domain and the mechanism behind its segregation and maintenance. I also conduct in-depth functional studies on FABP9, which was a strong candidate for tethering membrane lipids to underlying cytoskeletal elements in this region. My studies showed that the maintenance of this stable segregation in the sperm head was at least in part due to a specialized diffusion barrier at a region called the sub-acrosomal ring. I found that FABP9 did not play a role i