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Updated: Jan 6, 2026
Harvesting Sperm and Artificial Insemination of Mice
Published on: April 28, 2007
Cross-species insemination reveals mouse sperm ability to enter and cross the fish micropyle
Suma Garibova1, Eva Stickler2, Fatima AlAli1
1Sidra Medicine, Research Branch, Reproductive and Perinatal Health Division, Doha, Qatar.
Abstract:
Extracellular matrices surrounding eggs in fish (chorion) and mammals (zona pellucida [ZP]) regulate gamete recognition before fertilization, though their mechanisms differ. Mouse sperm bind and cross the ZP at any site, while fish sperm cross the chorion through a funnel-shaped opening, the micropyle. To explore these divergent processes, we established cross-species insemination assays, mixing zebrafish eggs with mouse sperm. While mouse sperm could not bind to the chorion, a subpopulation successfully located and crossed the fish micropyle. Confocal and electron microscopy revealed that sperm entered the micropyle and accumulated in the zebrafish inter-chorion space. However, transgenic mouse sperm with mCherry-labeled acrosomes failed to undergo acrosome exocytosis efficiently in the micropyle, with both acrosome-intact and reacted sperm found in the inter-chorion space. Sperm entry and crossing were dependent on hyperactive motility, as sperm from CatSperdNull mice, which fail to undergo hyperactivation, did not interact with or cross the micropyle. These findings suggest a conserved mechanism for sperm entry into the micropyle, providing a novel platform to investigate cross-species gamete interactions and uncover novel steps in fertilization.
Insights
Mouse sperm can navigate fish egg micropyles, revealing conserved fertilization mechanisms. This cross-species study highlights sperm motility
Area of Science:
- Reproductive biology
- Comparative embryology
- Fertilization mechanisms
Background:
- Fish eggs have a chorion with a micropyle for sperm entry, while mammals have a zona pellucida (ZP).
- Mechanisms of sperm interaction with these extracellular matrices differ significantly between fish and mammals.
- Understanding these differences is key to comprehending fertilization across species.
Purpose of the Study:
- To investigate cross-species gamete interactions using a zebrafish egg and mouse sperm model.
- To explore the conserved mechanisms of sperm entry through the micropyle.
- To identify factors influencing sperm interaction with the fish egg extracellular matrix.
Main Methods:
- Cross-species insemination assays mixing zebrafish eggs and mouse sperm.
- Confocal and electron microscopy to visualize sperm-egg interactions.
- Utilized transgenic mouse sperm (mCherry-labeled acrosomes) and CatSperdNull mutant sperm.
Main Results:
- Mouse sperm successfully located and crossed the zebrafish micropyle, but not the general chorion.
- Sperm entered the micropyle and accumulated in the inter-chorion space.
- Acrosome exocytosis was inefficient within the micropyle, and sperm hyperactivation was crucial for micropyle interaction and crossing.
Conclusions:
- Sperm entry through the micropyle appears to involve conserved mechanisms.
- Mouse sperm hyperactive motility is essential for navigating the micropyle.
- This cross-species model offers a novel platform for studying fertilization and gamete interactions.
