Figure 1

Expression and subcellular localization of CDK9 and cyclin T1 in mouse oocytes and preimplantation embryos. A. The antibodies against CDK9 and cyclin T1 used in the present study specifically recognize the corresponding antigens in mouse embryos. Late two-cell embryos were separately immunostained with working dilutions (1:50) of either anti-CDK9 or -cyclin T1 antibodies (left) or with such antibodies pre-incubated with 10-fold molar excesses of the peptide antigens (right). Bar: 50 μm. B. Expression of CDK9 and cyclin T1 in mouse germinal vesicles and MII oocytes. Note that, in both instances, no fluorescent signals emanated from the nucleolar area. Bar: 50 μm. C. Time course of CDK9 and cyclin T1 expression at defined preimplantation stages by immunocytochemistry. Rabbit polyclonal and mouse monoclonal antibodies were used for immunolocalization of CDK9 (green) and cyclin T1 (red), respectively. Chromatin was counterstained with DAPI. Bar: 50 μm. D. Relative intensities of fluorescent signals from both anti-CDK9 and -cyclin T1 antibodies in postfertilization embryos. Samples from all stages were simultaneously processed for immunostaining and images were taken at the same laser power, thus enabling direct comparison of signal intensities. The results are mean values from at least five embryos. The fluorescence intensity at late 2-cell stage has been set as 100%. E. Nuclear translocation of CDK9 and Pol II CTD phosphoisoforms after fertilization. One-cell embryos were immunostained with antibodies against CDK9, Ser2P-, Ser5P-, and UnP-Pol II CTD at 18 h, 24 h, and 30 h after hCG injection (h phCG). Bar: 50 μm.