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Updated: Aug 5, 2026
Measuring Sperm Guidance and Motility within the Caenorhabditis elegans Hermaphrodite Reproductive Tract
Published on: June 6, 2019
Disruption of sperm release from insect testes by cytochalasin and beta-actin mRNA mediated interference
B O Gvakharia1, P Bebas, B Cymborowski
1Department of Zoology, Oregon State University, Corvallis, Oregon 97331, USA.
Abstract:
Release of sperm bundles from moth testes is controlled by the local circadian oscillator. The mechanism which restricts migration of sperm bundles to a few hours each day is not understood. We demonstrate that a daily cycle of sperm release is initiated by the migration of folded apyrene sperm bundles through a cellular barrier at the testis base. These bundles have conspicuous concentrations of actin filaments at their proximal end. Inhibition of actin polymerization by cytochalasin at aspecific time of day inhibited sperm release from the testis. Likewise, application of double-stranded actin RNA specifically inhibited sperm release. This RNA-mediated interference (RNAi) lowered the pool of actin mRNA in tissues involved in sperm release. The decline in mRNA levels resulted in the selective depletion of F-actin from the tip of apyrene sperm bundles, suggesting that this actin may be involved in the initiation of sperm release. Combined results of RNAi experiments at physiological, cellular and molecular levels identified unique cells that are critically involved in the mechanism of sperm release.
Insights
Moth sperm release is timed daily by a local circadian oscillator. Actin filaments at the sperm bundle tip are crucial for initiating this release through a cellular barrier.
Area of Science:
- Reproductive Biology
- Circadian Rhythms
- Molecular Mechanisms
Background:
- Sperm bundle release from moth testes is regulated by a local circadian oscillator.
- The precise mechanism controlling the daily timing of sperm bundle migration remains unclear.
Purpose of the Study:
- To elucidate the molecular mechanism controlling the daily cycle of sperm release in moths.
- To identify the role of actin filaments in the initiation of sperm bundle migration.
Main Methods:
- Inhibition of actin polymerization using cytochalasin.
- RNA-mediated interference (RNAi) targeting actin mRNA.
- Analysis of actin mRNA and F-actin levels in testis tissues.
- Investigation at physiological, cellular, and molecular levels.
Main Results:
- Daily sperm release is initiated by the migration of apyrene sperm bundles through a basal testis cellular barrier.
- Actin filament concentrations at the proximal end of sperm bundles are essential for release.
- Inhibition of actin polymerization or depletion of actin mRNA specifically blocked sperm release.
- RNAi led to F-actin depletion from sperm bundle tips, implicating actin in release initiation.
- Specific cells critical for sperm release were identified.
Conclusions:
- Actin polymerization is a key molecular player in the daily initiation of sperm release in moths.
- The study identifies unique cells and the role of actin dynamics in regulating the timing of sperm bundle migration.
