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Updated: Aug 17, 2026
Mouse Oocyte Microinjection, Maturation and Ploidy Assessment
Published on: July 23, 2011
Fate of microinjected sperm components in the mouse oocyte and embryo
J M Cummins1, T Wakayama, R Yanagimachi
1School of Veterinary Studies, Murdoch University, Western Australia. cummins@central.murdoch.edu.au
Abstract:
Intact mouse sperm or mouse sperm tails alone, labelled with MitoTracker Green FM fluorochrome, were injected into mouse oocytes and the cells cultured in vitro for up to 5 days. The dye stained midpiece mitochondria, the sperm tail coarse fibres and the sperm perforatorium. Intact sperm (or tails injected with separated heads) induced normal embryonic development. The mitochondria could be identified in embryos up to the 4-cell stage, remaining associated with the sperm tail. They largely disappeared by the 8-cell stage, when only a minority of embryos (6/43) could be found with small patches of mitochondria. Axonemal elements could be identified coiled up in single external blastomeres as late as day 5 blastocysts. By contrast, mitochondria as well as tail components could be identified up to 5 days after injection of sperm tails alone into non-activated oocytes and also in embryos that arrested development before the 8-cell stage. We conclude that disappearance of the labelled sperm mitochondria in normally cleaving embryos is not due to fading or inactivation of the fluorochrome marker, but is rather an event specifically tied to cell cycle activities around the second cell division.
Insights
Sperm mitochondria disappear during early mouse embryonic development, specifically around the second cell division. This disappearance is linked to cell cycle activity, not marker degradation.
Area of Science:
- Reproductive Biology
- Developmental Biology
- Mitochondrial Dynamics
Background:
- Sperm contribute essential components to fertilization and early embryonic development.
- The fate and persistence of sperm-derived organelles, particularly mitochondria, during embryogenesis are not fully understood.
- Investigating sperm component degradation provides insights into developmental regulation.
Purpose of the Study:
- To track the fate of mouse sperm mitochondria and tail components after injection into oocytes.
- To determine the timing and conditions influencing the disappearance of sperm mitochondria during early embryonic development.
- To differentiate between marker inactivation and biological processes causing sperm component loss.
Main Methods:
- Mouse sperm and sperm tails were labeled with MitoTracker Green FM.
- Labeled sperm or tails were injected into mouse oocytes.
- Injected oocytes were cultured in vitro for up to 5 days.
- Embryos were analyzed for the presence of sperm-derived mitochondria and axonemal elements using fluorescence microscopy.
Main Results:
- Mitochondria were identified in embryos up to the 4-cell stage, associated with sperm tails.
- Sperm mitochondria largely disappeared by the 8-cell stage in normally developing embryos.
- Axonemal elements persisted until the blastocyst stage (day 5).
- In arrested embryos or those receiving only sperm tails, sperm mitochondria and tail components persisted longer.
Conclusions:
- The disappearance of sperm mitochondria in normally cleaving embryos is tied to cell cycle events around the second division.
- This degradation is a biological process, not a result of fluorochrome marker fading or inactivation.
- Sperm tail components exhibit differential persistence compared to mitochondria.
