Magnifying stem cell lineages: the stop-EGFP mouse.

Cell fate mapping techniques which can label clonal cell lineages are of importance because they allow one to investigate the distribution and types of daughter cells arising from single precursor cells. Thus, the potential of precursor cells to generate various types of descendent cells can be studied at the single-cell level. The stop-EGFP transgenic mouse carries a premature stop codon-containing enhanced green fluorescent protein (EGFP) gene as a target gene for mutations. A cell having undergone a mutation at the premature stop codon and its descendant cell lineage will express EGFP, thus a clonal cell lineage can be traced in vivo using a fluorescent microscope. Using the stop-EGFP mouse, stem cell clonal lineages in the mouse dorsal epidermis can be investigated in vivo and repeated analyses of the same cell lineages can be performed over time. In vivo imaging studies possible with the stop-EGFP mouse provide new insights into the structure of epidermal proliferative units (EPUs). The stop-EGFP system provides a novel tool for investigating clonal cell lineages in developmental studies as well as in stem cell biology.