The development of the cardiovascular system is a highly dynamic process dependent on multiple signaling pathways regulating proliferation, differentiation, migration, cell-cell and cell-matrix interactions. To characterize cell and tissue dynamics during the formation of the cardiovascular system in mice, we generated a novel transgenic mouse line, Tg(Flk1::myr-mCherry), in which endothelial cell membranes are brightly labeled with mCherry, a red fluorescent protein. Tg(Flk1::myr-mCherry) mice are viable, fertile, and do not exhibit any developmental abnormalities. High levels of mCherry are expressed in the embryonic endothelium and endocardium, and expression is also observed in capillaries in adult animals. Targeting of the fluorescent protein to the cell membrane allows for subcellular imaging and cell tracking. By acquiring confocal time lapses of live embryos cultured on the microscope stage, we demonstrate that the newly generated transgenic model beautifully highlights the sprouting behaviors of endothelial cells during vascular plexus formation. We have also used embryos from this line to imaging the endocardium in the beating embryonic mouse heart, showing that Tg(Flk1::myr-mCherry) mice are suitable for the characterization of cardio dynamics. Furthermore, when combined with the previously described Tg(Flk1::H2B-EYFP) line, cell number in addition to cell architecture is revealed, making it possible to determine how individual endothelial cells contribute to the structure of the vessel.
(c) 2008 Wiley-Liss, Inc.