Volume 15, No 2, Feb 2005
ISSN: 1001-0602
EISSN: 1748-7838 2018
impact factor 17.848*
(Clarivate Analytics, 2019)
Volume 15 Issue 2, February 2005: 127-132
ORIGINAL ARTICLES
Role of the first mitosis in the remodeling of the parental genomes in mouse embryos
Hong lin LIU1, 2, Kentaro T. HARA1, Fugaku AOKI1,*
1Department of Integrated Biosciences, Graduate School of Frontier Sciences, University of Tokyo, Kashiwa, Chiba 277-8571, Japan
2College of Animal Science and Technology, Nanjing Agricultural University, Nanjing 210095, China.
Correspondence: Fugaku AOKI(aokif@k.u-tokyo.ac.jp)
Although male and female pronuclei reside in the same zygotic cytoplasm, they differ in many respects, such as volume and transcriptional activity. The aim of this study is to investigate whether these differences are lost during the first mitosis. For this purpose, a new method was developed to inhibit the mixing of two parental chromosomes during mitosis, thus to induce the formation of two nuclei after they exit from the mitotic phase. In this method, one-cell embryos are arrested at metaphase by treatment with nocodazole, and whn exitting from the mitotic phase, two nuclei were formed in a single karyocyte following treatment with 6-dimethylaminopurine (6-DMAP). These embryos were designated as post-mitotic embryos (PM-embryos), in which the two nuclei were derived from the male and female genomes. We found that in the control one-cell embryos that had not been treated with the reagents, the volume of the male pronucleus was about 1.65-fold greater than that of the female pronucleus, whereas the volumes of the two nuclei in the PM-embryos were similar (volume ratio of 1.01). Although a two-fold difference in transcriptional activity was detected between the male and female pronuclei in the control embryos, no difference in transcriptional activity was detected between the two nuclei of PM-embryos. The ratio of transcriptional activity in the nucleus derived from the paternal genome to that from the maternal genome was 1.02, for which no significant difference was detected by the c2 fitness test. Therefore, the volumes and transcriptional activities of the male and female nuclei were approximately equal in PM-embryos, which suggests that the asymmetries of pronuclear volume and transcriptional activity between male and female genomes are somehow losted during the first mitosis.
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