Vital labeling of embryonic cells using fluorescent dyes and proteins

This chapter presents techniques used for labeling single cells or small groups of cells with fluorescent dyes and proteins. Fluorescent dextran and photo-activatable fluorescent proteins (PAFP) labeling of cells offer a direct means to label single cells or small groups of cells, making it appropriate for either fate mapping or cell lineage studies. Lipid-soluble carbocyanine dyes offer a simpler means to label groups of cells for fate mapping studies. The experimental requirements for cell lineage and fate map studies are very similar. Both require a means of labeling a cell in a defined region of the embryo, of identifying the progeny of the labeled cell(s) over time, and of scoring the final phenotypes and positions of the progeny. There are a number of methods available to label single cells as well as small populations of cells in the chick embryo. While intracellular injection of rhodamine dextran is a very reliable technique for labeling individual cells, it is also a highly invasive technique. Consequently, cell death occurs in more than half the injected cells. 1,1′-dioctadecyl-3,3,3′,3′-tetramethylindocarbocyanine (DiI) on the other hand is less invasive but not noninvasive. It is best used for labeling more than one cell.