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. 2020 Sep 21;9:e55589. doi: 10.7554/eLife.55589

Figure 4. Apelin signaling functions downstream of Notch signaling in endothelial cells.

(A - D) Confocal projection images of the blood vasculature in the trunk region of Tg(flt1:tdTomato) (A) and Tg(fli1a:EGFP) (B–D) animals at 54 (B–D) and 72 (A) hpf. (A) Injection of a dll4 morpholino leads to an increase in TgBAC(apln:EGFP) expression. (B) Loss of Apelin function can block excessive endothelial sprouting in dll4 morphants. (C, E) Angiogenic response in aplnrb -/-, plxnd1 -/-, and aplnrb -/-; plxnd1 -/- embryos (arrowheads) (n = 95). (D, F) Angiogenic response to bmp2b overexpression in aplnr +/- and aplnr -/- embryos (arrowheads). (E) Genotype of embryos for aplnrb after sorting them according to phenotype. (G) RT-qPCR analysis of APELIN mRNA levels in HUVECs treated with DAPT for 24 hr. Blocking Notch signaling with DAPT induces APELIN expression. (H) RT-qPCR analysis of APELIN mRNA levels in HUVECs cultured on DLL4 to activate Notch signaling. Activating Notch signaling represses APELIN expression. Arrowheads point to ectopic sprouts. n.s. not significant (two-tailed t-test). Ct values can be found in Figure 4—source data 1. Scale bars: A, C, 20 µm; B, 15 µm; D, 30 µm.

Figure 4—source data 1. Ct values of RT-qPCR.

Figure 4.

Figure 4—figure supplement 1. Apelin signaling functions downstream of Notch signaling in ECs.

Figure 4—figure supplement 1.

Confocal projection images of the trunk region of Tg(fli1a:EGFP) embryos at 54 hpf. Loss of aplnrb function can rescue excessive endothelial sprouting in dll4 morphants. Arrowheads point to ectopic sprouts and asterisks indicate missing DLAV fragments. Scale bar: 30 µm.