| Description |
The sperm of the roundworm Caenorhabditis elegans move by a crawling motion, in contrast to mammalian sperm, which exhibit a swimming motion. This method of locomotion makes the sperm of C. elegans an excellent model for examining cell motility. In order to become motile, the sperm must undergo the process of activation, during which the sperm change morphologically and gain the ability to crawl. Because C. elegans is an androdioecious species, the sperm of both the male and hermaphrodite must activate. Previous work has shown that each sex relies on a distinct genetic pathway to activate its sperm, though both pathways are present in sperm from both males and hermaphrodites. In males, two protein factors, SWM-1 and TRY-5, have been shown to modulate sperm activation. SWM-1 activity is required to delay activation while spermatids reside in the male's seminal vesicle. In this project, I utilized two methods to identify additional protein factors that may have a regulatory role in the activation process. Both methods served to map suppressors of swm-1 that had been previously identified through a genetic screen. The first identification method was mapping by outcrossing. Suppressed lines were outcrossed to a polymorphic strain, and F2 male worms expressing the suppressed phenotype were pooled. I then sequenced the entire genomes of these worms and identified genomic regions linked to the suppression phenotype. The second method involved sequencing suppressed strains without any mapping. This strategy relied on the filtering of common variants, variants inconsistent with the mutagen of choice, and variants unlikely to influence sperm activation out of the total variant list, leaving only mutations in genes with a relatively high likelihood of affecting the activation process. Both of these variant identification methods have yielded short lists of variants of interest that can now be tested for causality using rescue experiments. As a result of this project, our understanding of the biochemical pathway governing the process of sperm activation has been broadened and we have gained general insights into the signals required for the development of cell motility. |
