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. 2023 Oct 16;222(12):e202212088. doi: 10.1083/jcb.202212088

Figure 7.

Figure 7.

AT1 cells constitute an hbEGF-EGFR signaling niche for AT2 cell proliferation. (A and B) scRNA-seq (A) and in situ hybridization (B) shows hbEGF expression by AT1 cells. (C and D) EGFR-Emerald allele shows EGFR protein (Emerald-GFP) restricted to AT2 cell apical membrane (Muc1) in control (C) and internalized on endosomes (Grb2 protein co-localization) after BHT (D). (E and F) Representative immunostaining (E) of inactive (no toxin, apical) and activated (BHT, endocytosed) EGFR with quantitation (F) of EGFR-active AT2 cells in controls and after BHT (n = 300 Lamp3+ cells scored in uninjured and n = 358 Lamp3+ cells scored 40 h after BHT; n = 3 mice per condition). (G) pErk1/2+ AT2 cell (Lamp3+) after BHT. (H) Strategy for deletion of hbEGF in AT1 or EGFR in AT2 cells prior to AT1 killing, with EdU administration 1 h prior to evaluation. (I–K) Representative images (I and J) and quantitation (K) of AT2 cell proliferation (Lamp3+EdU+) in control lungs and 2 d after BHT (hbEGF+/del: 2,181 Lamp3+ cells scored in n = 4 mice; hbEGFlox/del: 3,410 Lamp3+ cells scored in n = 5 mice; EGFR+/del: 3,432 Lamp3+ cells scored in n = 3 mice; EGFRlox/del: 2,962 Lamp3+ cells scored in n = 3 mice). Scale bars, 5 µm (B–D and G), 15 µm (E), 25 µm (I and J). Em, Emerald GFP; TMX, tamoxifen. Data are mean ± SEM. P values calculated by two-sided Student’s t test.