title: Analysis of the mechanism(s) of metaphase I arrest in strain LT mouse oocytes: participation of MOS.
abstract: Oocytes of almost all vertebrates become arrested at metaphase II to await fertilization. Arrest is achieved with the participation of a protein complex known as cytostatic factor (CSF) that stabilizes histone H1 kinase activity. MOS and mitogen-activated protein kinase (MAPK) are important components of CSF. Strain LT/Sv mice, and strains related to LT/Sv, produce a high percentage of atypical oocytes that are arrested at metaphase I when normal oocytes have progressed to metaphase II. The potential role of MOS in metaphase I arrest was investigated using strain LT/Sv and LT-related recombinant inbred strains, LTXBO and CX8-4. MOS and MAPK are produced and functional in maturing LT oocytes. Two experimental paradigms were used to reduce or delete MOS in LT oocytes and assess effects on metaphase I arrest. First, sense and antisense Mos oligonucleotides were microinjected into metaphase I-arrested oocytes. Antisense, but not sense, Mos oligonucleotides promoted the activation of metaphase I-arrested oocytes. Second, mice carrying a Mos null mutation were crossed with LT mice, the null mutation was backcrossed three times to LT mice, and Mos(+/-) N3 mice were intercrossed to produce Mos(-/-), Mos(+/-) and Mos(+/+) N3F1 mice. Oocytes of all three Mos genotypes of N3F1 mice sustained meiotic arrest for 17 hours indicating that metaphase I arrest is not initiated by a MOS-dependent mechanism. However, unlike Mos(+/+) and Mos(+/-) CX8-4 N3F1 oocytes, metaphase I arrest of Mos(-/-) CX8-4 N3F1 oocytes was not sustained after 17 hours and became reversed gradually. These results, like the antisense Mos oligonucleotide microinjection experiments, suggest that MOS participates in sustaining metaphase I arrest in LT oocytes.
authors.affiliation: The Jackson Laboratory, Bar Harbor, ME 04609, USA.
authors.forename: Y
authors.initials: Y
authors.lastname: Hirao
authors.forename: J J
authors.initials: JJ
authors.lastname: Eppig
mesh_terms: D000818:Animals; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism; D002478:Cells, Cultured; D003433:Crosses, Genetic; D008540:Meiosis / Q000502:physiology*; D008677:Metaphase / Q000502:physiology*; D051379:Mice; D008810:Mice, Inbred C57BL; D008817:Mice, Mutant Strains; D016376:Oligonucleotides, Antisense; D009865:Oocytes / Q000166:cytology* / Q000201:enzymology / Q000378:metabolism; D017231:Proto-Oncogene Proteins c-mos / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*
chemical_list: D016376:Oligonucleotides, Antisense; D017231:Proto-Oncogene Proteins c-mos; D017871:Calcium-Calmodulin-Dependent Protein Kinases