Rac1 Temporarily Suppresses Fertilization Envelope Formation Immediately After 1-Methyladenine Stimulation
In starfish oocytes, the hormone 1-methyladenine (1-MA) induces germinal vesicle breakdown (GVBD) through a signaling cascade involving PI3K, SGK, Cdc25, and Cdk1/cyclin via G-proteinβγ subunit. Following GVBD, fertilization triggers an intracellular calcium increase, leading to the formation of the...
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MDPI AG
2025-03-01
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| author | Sakurako Aida Takako Matsumoto Yuna Yamazaki Nunzia Limatola Luigia Santella Kazuyoshi Chiba |
| author_facet | Sakurako Aida Takako Matsumoto Yuna Yamazaki Nunzia Limatola Luigia Santella Kazuyoshi Chiba |
| author_sort | Sakurako Aida |
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| description | In starfish oocytes, the hormone 1-methyladenine (1-MA) induces germinal vesicle breakdown (GVBD) through a signaling cascade involving PI3K, SGK, Cdc25, and Cdk1/cyclin via G-proteinβγ subunit. Following GVBD, fertilization triggers an intracellular calcium increase, leading to the formation of the fertilization envelope (FE) via cortical granule exocytosis. While transient calcium elevations are known to occur after 1-MA stimulation even without fertilization, the inability of these calcium elevations to induce cortical granule exocytosis and FE formation remained unexplained. In this study, we found that co-treatment with 1-MA and calcium ionophore A23187 prevents FE formation, revealing a transient period termed the “no FE phase” persisting for several minutes. After no FE phase, the oocytes regain full competence to form the FE. Furthermore, we identified that the GEF/Rac1 signaling cascade is activated during the no FE phase. Notably, constitutively active Rac1 expressed in oocytes reproduces this inhibition even in the absence of 1-MA stimulation. These findings suggest that the GEF/Rac1 cascade, triggered by 1-MA, initiates the no FE phase and plays a critical role in coordinating the progression of subsequent fertilization events. |
| format | Article |
| id | doaj-art-702ed71e66d64db3aab1c9955e178379 |
| institution | DOAJ |
| issn | 2073-4409 |
| language | English |
| publishDate | 2025-03-01 |
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| spelling | doaj-art-702ed71e66d64db3aab1c9955e1783792025-08-20T02:42:42ZengMDPI AGCells2073-44092025-03-0114640510.3390/cells14060405Rac1 Temporarily Suppresses Fertilization Envelope Formation Immediately After 1-Methyladenine StimulationSakurako Aida0Takako Matsumoto1Yuna Yamazaki2Nunzia Limatola3Luigia Santella4Kazuyoshi Chiba5Department of Biological Sciences, Ochanomizu University, Tokyo 112-8610, JapanDepartment of Biological Sciences, Ochanomizu University, Tokyo 112-8610, JapanDepartment of Biological Sciences, Ochanomizu University, Tokyo 112-8610, JapanDepartment of Research Infrastructures for Marine Biological Resources, Stazione Zoologica Anton Dohrn, 80121 Napoli, ItalyDepartment of Research Infrastructures for Marine Biological Resources, Stazione Zoologica Anton Dohrn, 80121 Napoli, ItalyDepartment of Biological Sciences, Ochanomizu University, Tokyo 112-8610, JapanIn starfish oocytes, the hormone 1-methyladenine (1-MA) induces germinal vesicle breakdown (GVBD) through a signaling cascade involving PI3K, SGK, Cdc25, and Cdk1/cyclin via G-proteinβγ subunit. Following GVBD, fertilization triggers an intracellular calcium increase, leading to the formation of the fertilization envelope (FE) via cortical granule exocytosis. While transient calcium elevations are known to occur after 1-MA stimulation even without fertilization, the inability of these calcium elevations to induce cortical granule exocytosis and FE formation remained unexplained. In this study, we found that co-treatment with 1-MA and calcium ionophore A23187 prevents FE formation, revealing a transient period termed the “no FE phase” persisting for several minutes. After no FE phase, the oocytes regain full competence to form the FE. Furthermore, we identified that the GEF/Rac1 signaling cascade is activated during the no FE phase. Notably, constitutively active Rac1 expressed in oocytes reproduces this inhibition even in the absence of 1-MA stimulation. These findings suggest that the GEF/Rac1 cascade, triggered by 1-MA, initiates the no FE phase and plays a critical role in coordinating the progression of subsequent fertilization events.https://www.mdpi.com/2073-4409/14/6/405starfishoocyte maturationRac1actincalciumfertilization |
| spellingShingle | Sakurako Aida Takako Matsumoto Yuna Yamazaki Nunzia Limatola Luigia Santella Kazuyoshi Chiba Rac1 Temporarily Suppresses Fertilization Envelope Formation Immediately After 1-Methyladenine Stimulation Cells starfish oocyte maturation Rac1 actin calcium fertilization |
| title | Rac1 Temporarily Suppresses Fertilization Envelope Formation Immediately After 1-Methyladenine Stimulation |
| title_full | Rac1 Temporarily Suppresses Fertilization Envelope Formation Immediately After 1-Methyladenine Stimulation |
| title_fullStr | Rac1 Temporarily Suppresses Fertilization Envelope Formation Immediately After 1-Methyladenine Stimulation |
| title_full_unstemmed | Rac1 Temporarily Suppresses Fertilization Envelope Formation Immediately After 1-Methyladenine Stimulation |
| title_short | Rac1 Temporarily Suppresses Fertilization Envelope Formation Immediately After 1-Methyladenine Stimulation |
| title_sort | rac1 temporarily suppresses fertilization envelope formation immediately after 1 methyladenine stimulation |
| topic | starfish oocyte maturation Rac1 actin calcium fertilization |
| url | https://www.mdpi.com/2073-4409/14/6/405 |
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