By Teresa Davoli, Eros Lazzerini Denchi, and Titia de Lange, The Rockefeller University
Although biologists have been watching cells divide under the microscope for ~150 years, visualizing the steps of interphase in live cells has been difficult. In 2008 Sakaue-Sawano et al. developed a clever method, called FUCCI imaging, to watch a critical decision during interphase - the choice to start replicating DNA.
Image: In FUCCI imaging, red and green fluorescent proteins are fused to two interphase regulators, Cdt1 and Geminin, respectively. Cdt1 exists only during G1 and early S phase, whereas Geminin exists during S/G2. Thus, cells appear red in G1, yellow in early S, and green in late S and G2 phases. Here human fibroblasts are visualized by time-lapse live-cell imaging (phase-contrast and fluorescent images acquired every 15 min with 10X objective).