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Dynamic changes of #gamma#--tubulin in preimplantation development of parthenogenetic mouse embryos

Zhang Qinghua, Shan Zhiyan, Guan Na, Xu Yanning, Shen Jingling, Zhong Shuqi, Lei Lei

Department of Histology and Embryology,Harbin Medical University.Harbin 150081,Heilongjiang

Abstract

Tubulin is the major protein of microtubule.#alpha#-and #beta#-tubulins form heterodimers,while #gamma#-tubulin regulates microtubule organization.The present study aimed to observe the dynamic changes of #gamma#-tubulin in preimplantation development of parthenogenetic mouse embryos.Immunofluorescence and laser confocal microscopy were used to detect the location of #gamma#-tubulin in preimplantation parthenogenetic embryos activated by SrCl_(2).The oocytes were collected at 13-14 h after hCG injection,and then activated with 10 mmol/L SrCl_(2) in Ca~(2+)-free CZB medium with 5 mmol/L cytochalasin B(CB),fixed at 1 h intervals until 6 h after activation.The results showed that spindle was paralleled with the cell membrane all the time,when the meiosis of MⅡ mouse oocytes resumed.The rotation of spindle was inhibited,but karyokinesis was not influenced.At 0 h after activation,i.e.at metaphase,#gamma#-tubulin was distributed mainly on the two poles of spindle.At 1 h after activation,i.e.at anaphase,following the separation of chromosomes,#gamma#-tubulin was transformed from dense to disperse.At 2 h after activation,#gamma#-tubulin was localized between the segregated sister chromatids at telophase.However,at 3-6 h after activation,#gamma#-tubulin concentrated around the two female pronuclei during their formation and juxtaposition.Moreover,another group of MⅡ oocytes were activated for 6 h and cultured in droplets of KSOM medium under mineral oil in 5% CO_(2) in air at 37 oC to permit parthenogenetic development.The embryos were collected and fixed at 3 h,14 h,16 h,and 18 h of culture.At 3 h after culture,i.e.at mitotic interphase,it was shown that amorphous #gamma#-tubulin distributed around the nuclei of early parthenogenetic embryos.At 24 h after culture,i.e.at prometaphase,#gamma#-tubulin migrated along the spindle microtubule to the two poles.Our results showed that #gamma#-tubulin had similar location patterns at metaphase,anaphase and telophase in meiosis and mitosis.It was concluded that #gamma#-tubulin assembly in parthenogenetically activated oocytes facilitated the formation of negative pole cap and the stabilization of microtubule,thus promoting the spindle formation at meiosis and mitosis.The relocation of #gamma#-tubulin at anaphase and telophase might be induced by the event of segregation of homologous chromosome being pulled away by the spindle.#gamma#-tubulin might contribute to the migration and juxtaposition of the two female pronuclei as well.

Key words: #gamma#-tubulin;parthenogenetic activation;meiosis;mitosis;Mouse

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Citing This Article：

Zhang Qinghua, Shan Zhiyan, Guan Na, Xu Yanning, Shen Jingling, Zhong Shuqi, Lei Lei. Dynamic changes of #gamma#--tubulin in preimplantation development of parthenogenetic mouse embryos. Acta Physiol Sin 2008; 60 (6): 777-782 (in Chinese with English abstract).