Regulation of Caenorhabditis elegans Spermatozoa Motility by Varying External pH

Cell motility describes the methods that cells use to move through an environment and to move things internal to the cell. Cells move mainly to fulfill roles like tissue formation, tumor growth, wound healing, immune surveillance and engulfing pathogens. Cell locomotion involves protrusion of the leading edge of the cell with retraction of the cell body combining along with adhesion to the substrate. Each of these events depends on the dynamics of the cell’s cytoskeleton, which is typically composed of an actin network and other regulatory proteins. However, not all eukaryotic cells use an actin cytoskeleton to move. Since actin serve multiple roles inside cells, it is not clear what aspects of the complex biochemical network that includes actin is essential for cell locomotion. Surprisingly, amoeboid sperm cells of nematodes not only provide a unique perspective for studying cell motility, but also offer a simple experimental model in which the role of actin is replaced by a 14-KDa nematode specific major sperm protein (MSP). MSP not only forms the cell’s cytoskeleton but is also directly involved in cell locomotion. In spite of extensive research on amoeboid sperm cells, the biophysical and biochemical mechanisms by which they move remain poorly understood. The focus of this project is to get a better understanding of cytoskeleton dynamics and cell motility in nematode spermatozoa. We test the hypothesis that changes in external pH result in variation of spermatozoa cell motility and MSP assembly/disassembly. To test this hypothesis, we measured how external pH affects speed, shape, area, and MSP retrograde flow in C.elegans sperm cells. Our results indicate that crawling speed for C.elegans spermatozoa is optimized at a slightly basic pH of 7.5 and that this effect is driven by changes in the rate of polymerization at the leading edge of the cell