A model to study the fate of genetically-marked keratinocytes in culture

In this study we demonstrate a method for analyzing the spatial distribution or fate of progeny keratinocytes derived from single progenitor cells. The method relies upon the use of retroviral vectors to introduce a reporter gene into replicating cells and to effect integration and expression of that new gene. All progeny cells from that initial cell inherit and express the transferred gene. The reporter gene is the E. coli beta-galactosidase gene (B-gal), which encodes a histochemically-detectable product in the cytoplasm. Using this method, we show that foci of genetically marked, B-gal positive cells can be readily identified in submerged cultures and we term this grouping of cells a "clonal proliferation unit". Analysis of B-gal stained whole mounts and paraffin sections allows visualization of the proliferative potential and differentiating capacity of clonogenic cells. This model will allow exploration of how agents known to alter epidermal proliferation and differentiation affect lineage relationships.