Study On Mouse's NSN-Type And SN-Type Oocytes Maturing In Vitro And Their Nuclease Sensitivity

According to chromatin organization, full growing mouse follicle oocytes were identified as SN-type, whose condensed chromatin surrounded nucleolus, or NSN-type, whose decondensed chromatin distributed in almost whole nuclear. Surrounded by cumulus, oocytes were also identified as COC-NSN or COC-SN, otherwise they were identified as DO-NSN or DO-SN. The objection of this study was to research the difference of each type oocytes in chromatin organization, mature competence and nuclease sensitivity in vitro.Dyed by 0. 1μg/ml Hoechst 33342 for 10 minutes and exposed to lower irradiation shorter than 5 second oocytes could be successfully grouped without any meiosis competence losing.In full growing follicle oocytes, COC-NSN, COC-SN, DO-NSN and DO-SN were respectively accounted for 8.6%, 22.7%, 28.0% and 40.7%. Total of SN-type oocytes was larger than that of NSN-type oocytes. Among DO oocytes percents of NSN-type oocytes, 40. 8%, was higher than that among COC ooctyes, 27. 5%, while percents of SN-type among DO oocytes, 59. 2%, was lower than that among COC oocytes, 72. 5%.Ratio of oocytes undergoing GVBD and developing to MI stage in SN-type oocytes was higher than in NSN-type ooctyes while in COC-NSN oocytes was higher than in DO-NSN oocytes. Competence of oocytes' developing to MII after excluding FBI in SN-type oocytes was also higher than in NSN-type oocytes while in COC-NSN and in COC-SN oocytes were higher than in DO-NSN oocytes and in DO-SN oocytes respectively.The DNase I sensitivity of each type oocytes in GV stage didn' t show significant difference. But NSN-type oocytes undergoing GVBD had more S1 nuclease sensitivity than SN-type oocytes in same stage while no significant difference between COC-type oocytes and DO-type oocytes. Little difference among oocytes in Mil stage in S1 nuclease sensitivity was found.On the whole, significant difference exists between NSN-type and SN-type oocytes in chromatin organization, competence of undergoing GVBD or excluding PBI and in MI stage S1 nuclease sensitivity. Cumulus surround growing oocytesare playing important roles on oocytes' obtaining meiosis competence, and are also in coordination with chromatin organization.