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Updated: May 21, 2026
A Method for Microinjection of Patiria minata Zygotes
Published on: September 1, 2014
Effects of ionomycin on egg activation and early development in starfish
Filip Vasilev1, Jong T Chun, Giovanni Gragnaniello
1Laboratory of Cellular and Developmental Biology, Stazione Zoologica Anton Dohrn, Villa Comunale, Napoli, Italy.
Abstract:
Ionomycin is a Ca(2+)-selective ionophore that is widely used to increase intracellular Ca(2+) levels in cell biology laboratories. It is also occasionally used to activate eggs in the clinics practicing in vitro fertilization. However, neither the precise molecular action of ionomycin nor its secondary effects on the eggs' structure and function is well known. In this communication we have studied the effects of ionomycin on starfish oocytes and zygotes. By use of confocal microscopy, calcium imaging, as well as light and transmission electron microscopy, we have demonstrated that immature oocytes exposed to ionomycin instantly increase intracellular Ca(2+) levels and undergo structural changes in the cortex. Surprisingly, when microinjected into the cells, ionomycin produced no Ca(2+) increase. The ionomycin-induced Ca(2+) rise was followed by fast alteration of the actin cytoskeleton displaying conspicuous depolymerization at the oocyte surface and in microvilli with concomitant polymerization in the cytoplasm. In addition, cortical granules were disrupted or fused with white vesicles few minutes after the addition of ionomycin. These structural changes prevented cortical maturation of the eggs despite the normal progression of nuclear envelope breakdown. At fertilization, the ionomycin-pretreated eggs displayed reduced Ca(2+) response, no elevation of the fertilization envelope, and the lack of orderly centripetal translocation of actin fibers. These alterations led to difficulties in cell cleavage in the monospermic zygotes and eventually to a higher rate of abnormal development. In conclusion, ionomycin has various deleterious impacts on egg activation and the subsequent embryonic development in starfish. Although direct comparison is difficult to make between our findings and the use of the ionophore in the in vitro fertilization clinics, our results call for more defining investigations on the issue of a potential risk in artificial egg activation.
Insights
Ionomycin, used to increase intracellular calcium (Ca2+), causes harmful structural changes in starfish eggs, impairing fertilization and embryonic development. Further research is needed for its safe use in assisted reproduction.
Area of Science:
- Cell Biology
- Developmental Biology
- Reproductive Biology
Background:
- Ionomycin is a Ca(2+)-selective ionophore used to elevate intracellular Ca(2+) levels.
- Its precise molecular actions and secondary effects on egg structure and function are not fully understood.
- The ionophore is occasionally used for egg activation in in vitro fertilization (IVF) clinics.
Purpose of the Study:
- To investigate the effects of ionomycin on starfish oocytes and zygotes.
- To elucidate the molecular mechanisms and structural consequences of ionomycin exposure.
- To assess the impact of ionomycin on egg activation and early embryonic development.
Main Methods:
- Confocal microscopy and calcium imaging to monitor intracellular Ca(2+) levels.
- Light and transmission electron microscopy to examine structural changes.
- Microinjection of ionomycin to differentiate between external and internal effects.
Main Results:
- Ionomycin exposure caused rapid intracellular Ca(2+) increase and cortical structural changes in oocytes.
- Microinjected ionomycin did not elevate intracellular Ca(2+), suggesting external application is key.
- Actin cytoskeleton alterations, cortical granule disruption, and impaired cortical maturation were observed.
- Ionomycin-pretreated eggs showed reduced Ca(2+) response, failed fertilization envelope elevation, and abnormal development.
Conclusions:
- Ionomycin induces detrimental structural changes in starfish eggs, negatively affecting activation and development.
- The findings raise concerns about the potential risks of using ionomycin for artificial egg activation in IVF.
- Further investigation is warranted to fully understand ionomycin's effects and ensure safety in clinical applications.
