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Updated: Jul 19, 2026

Measuring Sperm Guidance and Motility within the Caenorhabditis elegans Hermaphrodite Reproductive Tract
10:07

Measuring Sperm Guidance and Motility within the Caenorhabditis elegans Hermaphrodite Reproductive Tract

Published on: June 6, 2019

Nematode sperm motility: nonpolar filament polymerization mediated by end-tracking motors

Richard B Dickinson1, Daniel L Purich

  • 1Department of Chemical Engineering, College of Engineeringne, University of Florida, Gainesville, Florida 32611, USA. dickinso@che.ufl.edu

Biophysical Journal
|October 24, 2006
PubMed

Insights

Major sperm protein (MSP) filaments drive nematode sperm motility without nucleotide binding. A novel model proposes ATP-driven end-tracking proteins facilitate MSP filament assembly and force generation for membrane protrusions.

Area of Science:

  • Cell Biology
  • Biochemistry
  • Biophysics

Background:

  • Nematode sperm motility relies on major sperm protein (MSP) filament assembly, mimicking actin-based motility in other cells.
  • Unlike actin, MSP filaments are nonpolar and lack nucleotide binding sites, posing a paradox for force generation.
  • Actin-based motility depends on ATP-bound actin addition and filament polarity, mechanisms absent in MSP-driven motility.

Purpose of the Study:

  • To resolve the paradox of MSP-based motility by proposing a novel model for filament assembly and force generation.
  • To explain how membrane protrusions are generated in nematode sperm without the typical actin-based mechanisms.
  • To elucidate the role of ATP and associated proteins in MSP filament dynamics.

Main Methods:

  • Theoretical modeling of MSP filament assembly and force generation.
  • Comparison of the proposed MSP model with established actin-based motility mechanisms (e.g., actoclampin model).
  • Analysis of predictions derived from the MSP end-tracking model against experimental observations.

Main Results:

  • A model is proposed where ATP hydrolysis drives interactions between membrane proteins and elongating MSP filament ends.
  • ATP activates tracking proteins or cofactors, not MSP subunits directly, differentiating it from actin dynamics.
  • The model predicts persistent membrane attachment, directed polymerization at the membrane, and depolymerization away from it.

Conclusions:

  • The MSP end-tracking model offers a resolution to the paradox of MSP-based motility.
  • This model explains key features of MSP-driven membrane protrusions, including their persistence and directional dynamics.
  • The findings highlight a unique mechanism of cytoskeletal force generation independent of nucleotide-dependent filament subunit dynamics.

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