Maturation-promoting factor (MPF) and mitogen activated protein kinase (MAPK) expression in relation to oocyte competence for in-vitro maturation in the mare.
In the equine species, a large proportion of oocytes fail to complete meiosis during in-vitro culture. The biochemical and molecular basis of this failure is unknown. The meiotic cell cycle is controlled in part by the maturation-promoting factor (MPF) and the mitogen-activated protein kinase (MAPK). In this study, we evaluated the oocyte competence for in-vitro maturation and the expression of MPF components (p34cdc2 and cyclin B) and MAPK after in-vitro culture. The maturation rate was influenced by the culture medium and the physiological stage of the mare at the time of oocyte recovery. We showed that MAPK and the two subunits of MPF were present in equine oocytes whatever the nuclear stage they reached after in-vitro culture and whatever the culture medium used. In incompetent oocytes, MAPK remained in its non-phosphorylated form, supposed to be inactive. In conclusion, the incompetence of equine oocytes to resume and complete meiosis is not due to the absence of p34cdc2, cyclin B or MAPK. Our results suggest that it is more probably due to a deficiency of regulators of MPF and/or to an inability to phosphorylate MAPK.
Goudet
G
G
I.N.R.A.-Haras Nationaux, Equipe de Reproduction Equine, Station P.R.M.D., Nouzilly, France.
Belin
F
F
Bézard
J
J
Gérard
N
N
D000818:Animals; D016203:CDC2 Protein Kinase / Q000032:analysis; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000096:biosynthesis* / Q000235:genetics; D002453:Cell Cycle; D002478:Cells, Cultured; D003470:Culture Media; D019926:Cyclin B / Q000032:analysis; D056744:Cyclin B1; D004971:Estrus; D005260:Female; D005786:Gene Expression Regulation; D006736:Horses / Q000502:physiology*; D016200:Maturation-Promoting Factor / Q000096:biosynthesis* / Q000235:genetics; D008540:Meiosis; D020929:Mitogen-Activated Protein Kinase Kinases; D009866:Oogenesis / Q000502:physiology; D006080:Ovarian Follicle / Q000254:growth & development; D010766:Phosphorylation; D011494:Protein Kinases / Q000172:deficiency / Q000502:physiology; D011499:Protein Processing, Post-Translational
D003470:Culture Media; D019926:Cyclin B; D056744:Cyclin B1; D011494:Protein Kinases; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D016203:CDC2 Protein Kinase; D016200:Maturation-Promoting Factor; D020929:Mitogen-Activated Protein Kinase Kinases