Genetic labeling of PDGFRa+ cells in the carotid artery. (A) Immunostaining for PDGFRa in the mouse ascending aorta at 2 months of age. Scale bar: 100 µm. (B) Schematic showing genetic lineage tracing via Pdgfra-CreER. To express the fusion protein instead of endogenous PDGFRα, the cDNA of green fluorescent protein (GFP), Cre recombinase (Cre), and mutated estrogen receptor ligand-binding domain (ERT2) was inserted into the translational start site of the PDGFRα locus. (C) Schematic outlining the experimental strategy. (D, E) Representative images of the initial labeling of tdTomato+ cells in the carotid artery (D) and ascending aorta (E) at 10-day-chase after tamoxifen administration. Asc Aorta: ascending aorta. Scale bars: 100 µm. (F–I) Immunostaining for Sca1 (F), CD34 (G), αSMA (H), and SM-MHC (I) on carotid artery sections from 10-days-chase. The dotted box area is shown in the inset with higher magnification. Scale bars: 100 µm. See also Figures S1 and S2.