DNA Synthesis in Mouse 1-Cell Embryos Containing Transferred Nuclei

抄録

We investigated DNA synthesis during the 1-cell stage of reconstituted mouse embryos. Nuclei from 2-cell embryos were transferred at either the G1/S or G2 stage of the cell cycle. To define the S phase period in normal embryos, it was first examined that DNA synthesis in in vitro fertilized and parthenogenetic embryos during the first and second cell cycles. The results showed that DNA synthesis during the first cell cycle began between 6 and 8 h and finished between 12 and 14 h after insemination. In the second cell cycle the DNA synthesis occurred between 1 and 4 h after cleavage. We obtained G1/S phase nuclei using aphidicolin, DNA synthesis inhibitor. The DNA synthesis of the 2-cell embryos was significantly inhibited by exposure to aphidicolin and initiated soon after release from it. DNA synthesis during the first cell cycle of nuclear transferred embryos differed depending upon the cell cycle of the ooplast and the donor nucleus. When a G2 nucleus was fused with an non-activated ooplast and then it was activated, DNA synthesis proceeded as seen in parthenogenetic 1-cell embryos. While the DNA synthesis was not seen when G2 nucleus was transferred into an activated ooplast. An activated ooplast received a G1/S nucleus the DNA synthesis started soon after fusion and it continued for a longer period. These results showed that DNA was synthesized in the 1-cell embryos containing transferred nuclei in cell cycles of an ooplast and a donor nucleus dependent manner.