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Figure 3 Insets are magnifications of dashed boxes. (a) 13 wpf (fish size 17 mm) Tg(fli1:EGFP);Tg(prox1a:KalTA4-UAS:uncTagRFP) hearts showing ventricular lymphatic sprouting at the base of the OFT (inset) (n = 11). (b) Ventricular lymphatics grow in close proximity to coronary arteries (inset) in 116 wpf (fish size 25–32 mm) Tg(flt1_9a_cFos:GFP);Tg(lyve1b:dsRed2) hearts (n = 15). (c) Heart of 11wpf (fish size 16–22 mm) Tg(fli1:EGFP);Tg(prox1a:KalTA4-UAS:uncTagRFP) fish treated with 100 µg/ml Phenylhydrazine hydrochloride (PHZ), showing increased ventricle size and total length of blood and lymphatic vessels following PHZ treatment, quantified in (d) (ncontrol = 21, nPHZ = 15, *p<0.005). (e,f) 12 wpf (fish size 19–22 mm) Tg(βactin2:loxP-mTagBFP-STOP-loxP-vegfaa)pd262; Tg(cmlc2:CreER) fish in the background of Tg(flt1_9a_cFos:GFP);Tg(prox1a:KalTA4-UAS:uncTagRFP). Induction of Vegfaa-OE results in increased blood vessel (insets) and lymphatic vessel coverage, as compared to vehicle (Vegfaa-VEH) treated sibling control, quantified in (g) (nVegfaa-VEH = 9, nVegfaa-OE = 10, *p<0.001). (h–j) Immature coronary plexus, lacking the stereotypical tree-patterning results in nearly absent ventricular lymphatics in cxcr4a-/- hearts of 22 wpf (fish size 25–28 mm) (i), as compared to wt siblings (h), quantified in (j) (nwt = 5, ncxcr4a-/-=6, *p<0.05). (k–m) Ventricular lymphatics are absent in Tg(fli1:EGFP); Tg(lyve1b:dsRed2); flt4-/- hearts (l) at 19–23 wpf (fish size 25–30 mm) as compared to wt siblings (k). (m) Quantification of blood and lymphatic vessel phenotype in flt4 -/- hearts (nwt = 4, nflt4 -/-=5 *p<0.01). (n–p) Tg(fli1:EGFP); Tg(lyve1b:dsRed2); vegfc +/- hearts at 26 wpf (fish size 25–30 mm) display severely defective ventricular lymphatics. (p) Quantification of blood vessel coverage and lymphatic sprout length and number, in vegfc +/- hearts (nwt = 3, nvegfc+/-=5 *p<0.005). (q–t) 12 wpf (fish size 19–22 mm) Tg(βactin2:loxP-mTagBFP-STOP-loxP-vegfaa)pd262; Tg(cmlc2:CreER) fish in the background of Tg(fli1:EGFP);Tg(lyve1b:dsRed2). The increase in lymphatic, but not blood vessel coverage induced by Vegfaa-OE (r), is reversed in vegfc+/- heterozygous animals (s). (t) Quantification of blood and lymphatic vessel coverage in (q–s) (nVegfaa-VEH = 3, nVegfaa-OE = 3, nVegfaa-VEH-blood vessel coverage=3, nVegfaa-OE-lymphatic vessel coverage=10 nVegfaa-OE;vegfc +/- -lymphatic vessel coverage=4, *p<0.01, relative to vehicle treated sibling control, **p<0.001 relative to Vegfaa-OE). Scale bars are 200 µm. Error bars, mean ± S.E.M. All panels show anterior views.