Imaging early macrophage differentiation, migration, and behaviors in live zebrafish embryos

Because zebrafish embryos are transparent, cell behaviors and interactions can be directly imaged noninvasively in live embryos using differential interference contrast-Nomarski light microscopy. We found that the imaging quality can be much improved by coupling differential interference contrast-Nomarski to true (analogical) color video so as to visualize the image in real time on a high-resolution colour video monitor. We explain here how to apply this approach to the in vivo imaging of embryonic macrophages, which constitute a distinct early macrophage lineage, that originates from the rostral-most lateral mesoderm--adjacent to the cardiac field, differentiate in the yolk sac, and rapidly spread in embryonic tissues, although still retaining proliferative capacity.