Time-Lapse Bioluminescence Imaging of Hes7 Expression In Vitro and Ex Vivo.

Somites are formed sequentially by the segmentation of the anterior parts of the presomitic mesoderm (PSM), and such periodical somite formation is crucial to ensure the proper vertebrae. In the mouse embryo, Hes7, a segmentation clock gene, controls this periodic event with new somites forming every 2 h. Hes7 oscillations are synchronized between neighboring PSM cells and propagate from the posterior to the anterior PSM in the form of traveling waves. However, the exact mechanisms that generate these oscillatory dynamics and control synchronization are still unclear. Given that the half-life of Hes7 is too short to be monitored with most fluorescent proteins, time-lapse bioluminescence imaging (BLI) is a suitable tool to monitor the chronological Hes7 expression dynamics. In this chapter, we introduce a ubiquitinated luciferase reporter which enables the visualization of Hes7 expression dynamics with high temporal and spatial resolution in living cells and tissues.