Transcriptional activity of the <i>Tktl1</i> promoter in oocytes and preimplantation embryos.

<p>Plasmids containing the promoter regions of the <i>Tktl1</i> (p<i>Tktl1-2467+25</i>) and <i>Zp3</i> genes were microinjected into growing oocytes (A), one-cell-stage embryos (B), and early and late two-cell-stage embryos (C and D), and their transcriptional activities were then evaluated by luciferase reporter gene assay. The transcriptional activity of a plasmid without a promoter (None) was used as a control to determine the background level. Plasmids (200 ng/µl) were microinjected into the nucleus. Experiments were performed at least three times and the results are presented as means ± SEM. Asterisks indicate significant differences (Student's <i>t</i>-test; <i>P</i><0.05).