Abstract

Form follows function, and this maxim holds particularly true for the nematode sperm cell. Motility is essential for fertilization, and the process of spermatogenesis culminates in the production of a crawling spermatozoon with an extended pseudopod. However, the morphological similarity to amoeboid cells of other organisms is not conserved at the molecular level. Instead of utilizing the actin cytoskeleton and motor proteins, the pseudopod moves via the regulated assembly and disassembly of filaments composed of the major sperm protein (MSP). The current work reviews the structure and dynamics of MSP filament formation, the critical role of pH in MSP assembly, and the components that regulate this process. The combination of cytological, biochemical, and genetic approaches in this relatively simple system make nematode sperm an attractive model for investigating the mechanics of amoeboid cell motility.

Highlights

  • Detailed descriptions of sperm development, or spermatogenesis, can be found in the WormBook chapter Spermatogenesis and elsewhere (e.g., Chu and Shakes, 2013); a brief summary is included here and illustrated in Figure 1 to emphasize the particulars of MSP assembly and segregation

  • Monoclonal antibodies to MSP first detect the protein in primary spermatocytes within structures termed fibrous body-membranous organelle (FB-membranous organelles (MOs)) complexes (Figure 1)

  • Secretion of MSP serves as a signaling molecule for oocyte maturation and ovulation (Miller et al, 2001); for details of these functions, the reader is directed to excellent reviews (WormBook chapter Control of oocyte meiotic maturation and ovulation; Kim et al, 2013)

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Summary

Spermatogenesis

Detailed descriptions of sperm development, or spermatogenesis, can be found in the WormBook chapter Spermatogenesis and elsewhere (e.g., Chu and Shakes, 2013); a brief summary is included here and illustrated in Figure 1 to emphasize the particulars of MSP assembly and segregation. The round, non-motile spermatids bud from the surface of the residual body, which contains components that are not needed for further development or sperm function (Ward et al, 1981). Monoclonal antibodies to MSP first detect the protein in primary spermatocytes within structures termed fibrous body-membranous organelle (FB-MO) complexes (Figure 1). MSP accumulates in paracrystalline arrays of filaments within the fibrous bodies. These FB-MO complexes segregate into the budding spermatids. Secretion of MSP serves as a signaling molecule for oocyte maturation and ovulation (Miller et al, 2001); for details of these functions, the reader is directed to excellent reviews (WormBook chapter Control of oocyte meiotic maturation and ovulation; Kim et al, 2013)

Motility and fertilization
Acquisition of motility
Cytoskeletal restructuring
Motility and MSP
MSP assembly and structure
Reconstituted MSP polymerization system
Components that control MSP assembly
10. Directionality and force generation
11. Guidance cues
12. Evolution of the MSP gene family
13. Conclusion
14. References
Findings
44. Abstract
Full Text
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