Sex-linked genes are pressured to evolve due to environmental changes and the importance of fertility. This competitive nature drives certain regulatory genes towards novel roles in multiple processes. Two sex-linked genes that are essential in different fertility pathways are
gsp-3 and
gsp-4. These 98% identical genes arose from a duplication event and encode sperm-specific phosphatases that are orthologous to the PP1 gamma phosphatase in humans. We find that the GSP-3/4 phosphatases in C. elegans function sequentially in sperm meiosis, sperm motility, and the completion of oocyte meiosis. First, tracking of fluorescently-labeled chromosomes during sperm meiosis show
gsp-3/4 mutants take longer to segregate in meiosis I and fail to segregate during meiosis II. In
gsp-3/4 mutants, CLS-2, a central spindle protein that stabilized microtubules, is dumped into the mid-zone during meiosis I. We hypothesize that GSP-3/4 dephosphorylates CLS-2 as a regulatory switch to release the plus end of microtubules. This allows for microtubule de-polymerization dynamics during chromosome segregation. Secondly, sperm are less motile in
gsp-3/4 mutants. Sperm motility is driven by actin independent pseudopodial locomotion, where MSP proteins form filaments to create movement. Immunostaining and live imaging show that GSP-3/4 localize towards the disassembly end of MSP filaments. We hypothesize that GSP-3/4 play a regulatory role in disassembling MSP to complete this process of motion. Thirdly, GSP-3/4 is delivered with the paternal DNA post-fertilization. It is hypothesized that GSP-3/4 thus act as a signal for the completion of oogenesis. Co-IP with mass spectrometry, along with global phosphorylation profiling will uncover interacting partners and targets that these phosphatases regulate. Understanding the regulatory roles of GSP-3/4 in their journey throughout spermatogenesis, motility, and oogenesis will lead to a better understanding of the major players essential for fertility.