Sperm-induced calcium oscillations at fertilisation in ascidians are controlled by cyclin B1-dependent kinase activity.
The generation of calcium oscillations at fertilisation and during mitosis appears to be controlled by the cell cycle machinery. For example, the calcium oscillations in oocytes and embryos occur during metaphase and terminate upon entry into interphase. Here we report the manipulation of sperm-triggered calcium oscillations by cyclin-dependent kinase (CDK) activity, the major component of maturation/M phase promoting factor (MPF). To control the CDK activity we microinjected mRNAs encoding full-length GFP-tagged cyclin B1 or a truncated and therefore stabilised form of cyclin B1 ((delta)90) into unfertilised oocytes. In the presence of full-length cyclin B1, the calcium oscillations terminate when cyclin B1 levels fall along with the concomitant fall in the associated CDK activity. In addition, when the CDK activity is elevated indefinitely with (delta)90 cyclin B1, the calcium oscillations also continue indefinitely. Finally, in oocytes that contain low mitogen-activated protein (MAP) kinase activity and elevated CDK activity, the sperm-triggered calcium oscillations are again prolonged. We conclude that the CDK activity of the ascidian oocyte can be regarded as a positive regulator of sperm-triggered calcium oscillations, a finding that may apply to other oocytes that display sperm-triggered calcium oscillations at fertilisation. Furthermore, these findings may have a bearing upon the mitotic calcium signals of early embryos.
Levasseur
M
M
Department of Physiological Sciences, The Medical School, University of Newcastle upon Tyne, Framlington Place, Newcastle upon Tyne NE2 4HH, UK. m.d.levasseur@ncl.ac.uk
McDougall
A
A
D000818:Animals; D002070:Butadienes / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D019926:Cyclin B / Q000235:genetics / Q000378:metabolism*; D056744:Cyclin B1; D018844:Cyclin-Dependent Kinases / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D007700:Kinetics; D008297:Male; D008845:Microinjections; D009570:Nitriles / Q000494:pharmacology; D009865:Oocytes / Q000187:drug effects / Q000502:physiology*; D009991:Oscillometry; D014176:Protein Biosynthesis; D011494:Protein Kinases / Q000378:metabolism; D011687:Purines / Q000494:pharmacology; D012333:RNA, Messenger / Q000235:genetics; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D000077546:Roscovitine; D013084:Sperm-Ovum Interactions / Q000502:physiology*; D013094:Spermatozoa / Q000502:physiology*; D014561:Urochordata / Q000502:physiology*
D002070:Butadienes; D019926:Cyclin B; D056744:Cyclin B1; D004791:Enzyme Inhibitors; D009570:Nitriles; D011687:Purines; D012333:RNA, Messenger; D011993:Recombinant Fusion Proteins; C113580:U 0126; D000077546:Roscovitine; D011494:Protein Kinases; C102333:histone H1 kinase; D018844:Cyclin-Dependent Kinases; D002118:Calcium