Sox17 and Lung Progenitor Cell Figure 4. Sox17 increases Sca-1 expression adult respiratory epithelial cells. Adult CCSPrtTA control (A) and CCSPrtTA/tetO-Sox17 (B–N) transgenic mice were exposed to Dox for 5 d. (A–B) Immunostaining for Sca-1 was performed on lung sections. Increased Sca-1 staining was detected in the peripheral lung and near the bronchoalveolar duct junctions after expression of Sox17 (arrowheads and inset). (C–E) Dual-label immunofluorescence for Sox17 (C) and Sca-1 (D) demonstrated that the Sca-1 positive cells coexpressed Sox17 (arrows). (F–N) Triple-label immunofluorescent staining was performed for CCSP, proSP-C, and Sca-1. Sca-1 colocalized with CCSP-expressing cells near the bronchoalveolar duct junctions (open arrowhead; magnified in G–J). Sca-1 positive cells located in the peripheral lung (arrowheads; magnified in K–N) did not coexpress proSP-C (arrow; F,L, and N). Scale bars, 50 mm (A–B; F), 20 mm (C–E). doi:10.1371/journal.pone.0005711.g004 PLoS ONE | www.plosone.org 6 May 2009 | Volume 4 | Issue 5 | e5711