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. Author manuscript; available in PMC: 2016 May 26.
Published in final edited form as: Dev Cell. 2015 May 26;33(4):442–454. doi: 10.1016/j.devcel.2015.04.001

Figure 4. Cxcr4a–Cxcl12b expression during coronary vessel formation.

Figure 4

Confocal images of transgenic fish Tg(myl7:DsRed2-NLS; fli1:EGFP; cxcl12b:YFP) (A–C, E), Tg(kdrl:mCherry; fli1:EGFP; cxcl12b:YFP) (F–H), Tg(myl7:DsRed2-NLS; fli1:EGFP; cxcr4a:YFP) (I–M), Tg(dll4:EGFP; cxcr4a:YFP) (N), Tg(dll4:EGFP; cxcr4a:YFP; kdrl:mCherry) (O), and Tg(kdrl:mCherry; fli1:EGFP; cxcr4a:YFP) (P). Ventricular, but not atrial cardiomyocytes express cxcl12b:YFP prior to and during vessel formation (A, 28 dpf, B, 56 dpf, C, 77 dpf). cxcl12b:YFP labeling is found within the cytoplasm of cells containing a myl7-positive nuclei (red) and flanked by fli1a-positive (green) endothelial cells (A, inset, from confocal section, side panel). Levels of cxcl12b:YFP expression vary over the ventricle and between hearts, but are generally higher towards the base (A–D). Quantification of cxcl12b:YFP intensity (blue, normalized mean 14dpf to 84dpf, ±SEM) and vessel density (green, mean values of individual time points 7dpf to 420dpf) between base and apex of ventricular myocardium (D), both p<0.0001 (Wilcoxon signed rank test on paired values). In addition, expression is observed on the surface of the bulbous arteriosus (ba, A–C, F). cxcl12b:YFP expression is down regulated following establishment of the vessel network in cardiomyocytes, but is later expressed in the mural cells of mature vessels (E, inset arrowhead). cxcl12b:YFP-expressing mural cells surround large arterial vessels (F–H, blue), which express high levels of kdrl:mCherry (F–H, red). cxcr4a:YFP is not expressed prior to the emergence of endothelial cells on the surface of the ventricle (I, 28 dpf). Endothelial cells of angiogenic sprouts express cxcr4a:YFP as they migrate over the surface of the myocardium (J, 42dpf, panel showing tip cell; K, 70 dpf; brackets label cells displaying active migration morphology; L, intensity of cxcr4a:YFP in endothelial cells). The majority of vessels do not express cxcr4a:YFP after their formation (K–P). Larger arterial vessels do maintain cxcr4a:YFP expression, which overlaps with high levels of kdrl:mCherry and dll4:EGFP expression in these vessels (N–P). Scale bars 50µm.