(A) Whole-lung RNA homogenates obtained from Dll4+/+ and Dll4+/lacZ at P4 and P28 were used to quantify Kdr, Jag1, Nr2f2, Ephb4, Vegfa, Car4, Esm1, Apln, and Aplnr with qRT-PCR. n = 5 mice per group; *P < 0.05, **P < 0.01, ***P < 0.001. (B) Mouse lung ECs (PECAM pulldown) obtained from Dll4+/+ and Dll4+/lacZ at P6 and P14 were used to quantify Dll4, Nrp1, Jag1, Car4, Apln, Esm1, Efnb2, and Aplnr. n = 5 mice per group; *P < 0.01. (C) Mouse lung ECs were harvested from 14-day-old Dll4+/+ and Dll4+/lacZ mice. Lung homogenates were used to quantify DLL4, NICD, HES1, JAG1, VEGFA, and PECAM by immunoblotting, with densitometry shown graphically (D). n = 5 mice per group; *P < 0.01. (E) PECAM (green), CAR4 (red), and DAPI staining on P14 Dll4+/+ and Dll4+/lacZ lung sections (n = 4). (F) PECAM (green), APLNR (red) and DAPI (blue) staining on Dll4+/+ and Dll4+/lacZ mouse lung slides (n = 4). Scale bars: 10 μm. Data are shown as mean ± SD. (A, B, and D, Gaussian distribution used 1-way ANOVA with Tukey’s test) (A and B) Non-Gaussian distribution used 2-tailed Mann-Whitney U test.