Figure 1. Dlk1 Expression and Notch Activation during AT2-to-AT1 Transition in Culture.

(A and B) Freshly isolated AT2 (A) acquire AT1-like morphology within 7 days in culture (B). Scale bar, 50 μm.

(C) mRNA expression of the AT2 marker Sp-C, the AT1 marker Aqp5, the proliferation marker CDC25C, and Dlk1 over the course of 7 days in culture. Data are presented as relative mRNA levels compared with expression of each gene at baseline. Mean ± SE, n = 3–5. **p < 0.01 (3-day CDC25C versus baseline CDC25C), ***p < 0.001 (3-day Dlk1 versus baseline Dlk1), ****p < 0.0001 (7-day Aqp5 versus baseline Aqp5).

(D) Schematic of the Notch reporter mouse. Expression of the fluorescent protein Venus is controlled by cleaved NICD-CBF1 binding to tandem CBF1 binding sites.

(E) AT2 isolated from the Notch reporter mouse were cultured and stained for Sp-C and the AT1 marker T1α. Cells lost Sp-C and gained T1α expression upon converting into AT1-like cells. Notch reporter Venus was expressed at intermediate stages of transition and absent in a cell expressing a high level of T1α and a low level of Sp-C at 96 h of culture. Scale bar, 20 μm.

See also Figure S1.