Fig. 7.

Basal cells are progenitors for ductal, but not acinar, cells. (A) Lineage tracing was performed using Krt5^CreERT2;Rosa26^mTmG with recombination induced at either P1 (a-c) or adult stages (d-f). In the absence of Cre, no GFP was detected (a,d). However, in young or adult mice, induction of Cre resulted in KRT14⁺/GFP⁺ basal cells and GFP⁺ ductal cells (b,c,e,f). Arrowheads indicate ducts. Scale bar: 25 μm. (B) GFP⁺ luminal ductal cells were adjacent to GFP⁺ basal cells but not unlabeled basal cells in partially lineage-traced ducts, suggesting luminal cells are derived from basal cells by asymmetric division. Arrowheads indicate luminal cells derived from asymmetric division. Scale bar: 25 μm.