Identification and characterization of sperm-specific components required for female meiosis in C. elegans

• Author / Creator

  Banerjee,Rudra Prasanna

• In most sexually reproducing animals, sperm entry provides the signal to initiate the final stages of female meiosis. The molecular mechanism of this process is still unclear. In C. elegans, three maternally-expressed paralogs, memi-1, 2 and 3 (meiosis-to-mitosis) are required for sensing sperm entry. Loss of all three paralogs results in a skipped meiosis II (MII) phenotype. In contrast, a hypermorphic mutation, memi-1(sb41ts), results in embryonic lethality, whereby fertilized cells enter MII but are unable to exit MII properly. A previous genome-wide RNAi screen for suppressors of memi-1(sb41) lethality revealed two genes that encode sperm-specific PP1 phosphatases, gsp-3 and gsp-4. Further EMS-based suppressor screening recovered alleles of gsp-4 and additional genes in this pathway. One of the genes, gskl-1, encodes a putative GSK-3 protein kinase. Work presented in this thesis reveals that gskl-1 is functionally redundant with another GSK-3-encoding gene, gskl-2, and that double mutants exhibit a range of defects, including paternal-effect embryonic lethality, abnormal sister chromatid segregation during male meiosis, and defective spermatid budding. Furthermore, sperm produced from double-mutant males exhibited defects in motility and pseudopod treadmilling. Indirect immunofluorescence experiments showed that GSKL-1 and GSKL-2 locate to the pseudopod region of activated sperm, indicating that they could play a role in regulating the dynamics of the cytoskeletal polymer, major sperm protein (MSP), possibly by phosphorylating MSP at the tip of the pseudopod. gskl-1 gskl-2 double-mutant hermaphrodites also exhibited embryonic lethality with incomplete penetrance. Defective embryos exhibited normal MI, but MII spindle assembly was delayed, and the second polar body failed to extrude. In addition to the double mutant phenotypes, a gskl-1 gskl-2 gsp-4 triple mutant exhibited an increase in embryonic lethality, and some embryos displayed a skipped female MII phenotype, which is similar to memi-1/2/3(RNAi). Together, this work affirms that GSK-3 kinases and PP1 phosphatases perform some similar functions with respect to sperm motility and meiosis, and that these enzymes work together for post-fertilization functions involving MEMI.

• Subjects / Keywords

  • meiosis-to-mitosis
  • sperm motility
  • sperm competition
  • GSK3
  • PP1
  • MSP

• Graduation date

  Spring 2022

• Type of Item

  Thesis

• Degree

  Doctor of Philosophy

• DOI

  https://doi.org/10.7939/r3-he1h-g756

• License

  This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.