A localized calcium transient and polar body abscission

• Published in: Cell cycle (Georgetown, Tex.) Tex.), 2022-11, Vol.21 (21), p.2239-2254
• Main Authors: Mo, Guolong, Li, Ruizhen, Swider, Zachary, Leblanc, Julie, Bement, William M., Liu, X. Johné
• Format: Article
• Language: English
• Subjects: abscission; Animals; calcium; Calcium - metabolism; Calcium Chelating Agents - metabolism; Male; Meiosis; Oocytes - metabolism; Polar Bodies - metabolism; polar body; Protein Kinases - metabolism; Research Paper; Semen - metabolism; Xenopus oocytes
• ISSN: 1538-4101; 1551-4005
• DOI: 10.1080/15384101.2022.2092815

Polar body emission is a special form of cytokinesis in oocyte meiosis that ensures the correct number of chromosomes in reproduction-competent eggs. The molecular mechanism of the last step, polar body abscission, is poorly understood. While it has been proposed that Ca 2+ signaling plays important roles in embryonic cytokinesis, to date transient increases in intracellular free Ca 2+ have been difficult to document in oocyte meiosis except for the global Ca 2+ wave induced by sperm at fertilization. Here, we find that microinjection of the calcium chelator dibromo-BAPTA inhibits polar body abscission in Xenopus laevis oocytes. Using a novel, microtubule-targeted ratio-metric calcium sensor, we detected a calcium transient that is focused at the contractile ring-associated plasma membrane and which occurred after anaphase and constriction of the contractile ring but prior to abscission. This calcium transient was confirmed by mobile calcium probes. Further, the Ca 2+ -sensitive protein kinase Cβ C2 domain transiently translocated to the contractile ring-associated membrane simultaneously with the calcium transient. Collectively, these results demonstrate that a calcium transient, apparently originating at the contractile ring-associated plasma membrane, promotes polar body abscission.