title: The dynamics of MAPK inactivation at fertilization in mouse eggs.
abstract: Egg activation at fertilization in mammals is initiated by prolonged Ca(2+) oscillations that trigger the completion of meiosis and formation of pronuclei. A fall in mitogen-activated protein kinase (MAPK) activity is essential for pronuclear formation, but the precise timing and mechanism of decline are unknown. Here, we have measured the dynamics of MAPK pathway inactivation during fertilization of mouse eggs using novel chemiluminescent MAPK activity reporters. This reveals that the MAPK activity decrease begins during the Ca(2+) oscillations, but MAPK does not completely inactivate until after pronuclear formation. The MAPKs present in eggs are Mos, MAP2K1 and MAP2K2 (MEK1 and MEK2, respectively) and MAPK3 and MAPK1 (ERK1 and ERK2, respectively). Notably, the MAPK activity decline at fertilization is not explained by upstream destruction of Mos, because a decrease in the signal from a Mos-luciferase reporter is not associated with egg activation. Furthermore, Mos overexpression does not affect the timing of MAPK inactivation or pronuclear formation. However, the late decrease in MAPK could be rapidly reversed by the protein phosphatase inhibitor, okadaic acid. These data suggest that the completion of meiosis in mouse zygotes is driven by an increased phosphatase activity and not by a decline in Mos levels or MEK activity.
authors.affiliation: Institute of Molecular and Experimental Medicine, School of Medicine, Cardiff University, Cardiff CF14 4XN, UK.
authors.forename: Jose Raul
authors.initials: JR
authors.lastname: Gonzalez-Garcia
authors.affiliation: Institute of Molecular and Experimental Medicine, School of Medicine, Cardiff University, Cardiff CF14 4XN, UK School of Biosciences, Cardiff University, Cardiff CF10 3AX, UK.
authors.forename: Josephine
authors.initials: J
authors.lastname: Bradley
authors.affiliation: Institute of Molecular and Experimental Medicine, School of Medicine, Cardiff University, Cardiff CF14 4XN, UK.
authors.forename: Michail
authors.initials: M
authors.lastname: Nomikos
authors.affiliation: Institute of Molecular and Experimental Medicine, School of Medicine, Cardiff University, Cardiff CF14 4XN, UK School of Biosciences, Cardiff University, Cardiff CF10 3AX, UK.
authors.forename: Laboni
authors.initials: L
authors.lastname: Paul
authors.affiliation: Department of Animal Sciences, Purdue University, West Lafayette, IN 47907, USA.
authors.forename: Zoltan
authors.initials: Z
authors.lastname: Machaty
authors.affiliation: Institute of Molecular and Experimental Medicine, School of Medicine, Cardiff University, Cardiff CF14 4XN, UK.
authors.forename: F Anthony
authors.initials: FA
authors.lastname: Lai
authors.affiliation: Institute of Molecular and Experimental Medicine, School of Medicine, Cardiff University, Cardiff CF14 4XN, UK swannk1@cf.ac.uk.
authors.forename: Karl
authors.initials: K
authors.lastname: Swann
mesh_terms: D000818:Animals; D020013:Calcium Signaling; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D005306:Fertilization; D017930:Genes, Reporter; D049410:Luciferases, Renilla / Q000096:biosynthesis / Q000235:genetics; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008808:Mice, Inbred CBA; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D019319:Okadaic Acid / Q000494:pharmacology; D017232:Oncogene Proteins v-mos / Q000235:genetics / Q000378:metabolism; D010063:Ovum / Q000201:enzymology*; D010744:Phosphoric Monoester Hydrolases / Q000037:antagonists & inhibitors / Q000378:metabolism; D010766:Phosphorylation; D011499:Protein Processing, Post-Translational; D013094:Spermatozoa / Q000502:physiology
chemical_list: D004791:Enzyme Inhibitors; D017232:Oncogene Proteins v-mos; D019319:Okadaic Acid; D049410:Luciferases, Renilla; D020928:Mitogen-Activated Protein Kinases; D010744:Phosphoric Monoester Hydrolases
keywords: Egg; Fertilization; MAPK; Zygote
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