Two phases of calcium requirement during starfish meiotic maturation.
During meiosis in oocytes of the starfish, Asterina pectinifera, a Ca(2+) transient has been observed. To clarify the role of Ca(2+) during oocyte maturation in starfish, an intracellular Ca(2+) blocker, TMB-8, was applied. The oocyte maturation induced by 1-methyladenine (1-MA) was blocked by 100 microM TMB-8. Reinitiation of meiosis with germinal vesicle breakdown (GVBD) and the following chromosome condensation did not take place. Maturation-promoting factor (MPF) activity did not increase and GVBD and chromosome condensation did not occur. Ca(2+) transient observed immediately after 1-MA application in control oocytes was also blocked by TMB-8. When calyculin A, which activate the MPF directly, was applied to the oocytes instead of 1-MA in seawater containing 100 microM TMB-8, GVBD and chromosome condensation were blocked. Cytoplasmic transplantation studies confirmed that MPF was activated, although TMB-8 blocked GVBD. These results show that TMB-8 blocked the increase of MPF activity induced by 1-MA and the process of active MPF inducing GVBD and subsequent chromosome condensation. Together with the above phenomena, it is conceivable that there are two phases of Ca(2+) requirement during starfish oocyte maturation. These are the activation of MPF, moreover, GVBD, and the subsequent chromosome condensation.
Tosuji
Hiroaki
H
Department of Chemistry and Bioscience, Faculty of Science, Kagoshima University, Korimoto, Kagoshima 890-0065, Japan. tosuji@sci.kagoshima-u.ac.jp
Seki
Yukari
Y
Kyozuka
Keiichiro
K
D000818:Animals; D016203:CDC2 Protein Kinase / Q000378:metabolism; D002118:Calcium / Q000378:metabolism*; D002875:Chromosomes / Q000378:metabolism; D005707:Gallic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D016200:Maturation-Promoting Factor / Q000378:metabolism; D008540:Meiosis / Q000187:drug effects; D009865:Oocytes / Q000166:cytology / Q000187:drug effects / Q000201:enzymology; D011494:Protein Kinases / Q000378:metabolism; D013215:Starfish / Q000166:cytology* / Q000187:drug effects / Q000201:enzymology
C006014:8-(N,N-diethylamino)octyl-3,4,5-trimethoxybenzoate; D005707:Gallic Acid; D011494:Protein Kinases; C102333:histone H1 kinase; D016203:CDC2 Protein Kinase; D016200:Maturation-Promoting Factor; D002118:Calcium