Figure 4. Yap1 mediates endothelial cell proliferation downstream of Vegfc.
(A) Trunk vasculature at 3 dpf displaying endothelial cells (ECs) in green from uninjected, p53 morpholino (MO) injected and p53 +yap1 MO injected embryos. Asterisks highlight missing parachordal LECs (PLs). Scale bars: 50 μm. (B) Trunk vasculature at 3 dpf from uninjected, p53 MO injected and p53 +yap1 MOs injected embryos of the Tg(prox1a:KalT4xUAS:uncTagRFP); Tg(10xUAS:vegfc) strain. yap1 MO injection rescues the EC proliferation phenotype. ECs in green. Asterisks mark missing PLs. Scale bars: 50 μm. (C) Quantification of total EC number across four somites in vegfc-unstimulated (uninjected: 343 ± 9, n = 18; p53 MO: 341 ± 9, n = 18; p53 +yap1 MOs: 248 ± 15, n = 18; p<0.0001(****)) and vegfc-stimulated embryos (uninjected: 811 ± 35, n = 18; p53 MO: 794 ± 38, n = 18; p53 +yap1 MOs: 212 ± 10, n = 18; p<0.0001(****)). (D) Schematic representation of vegfc-overexpressing cell transplantations for single muscle grafts in [Tg(fli1a:nEGFP);(−5.2lyve1b:DsRed2)] hosts of siblings and MZyap1mw48-/- mutants. (E) Schematic of transplanted host embryo at 3 dpf. Muscle grafts produce excessive Vegfc causing a hyperproliferation response in adjacent PLs. (F) Quantification of PL number within one somite responding to the vegfc-OE single muscle graft at 3 dpf (sibling: 23.00 ± 1.19, n = 18; MZyap1mw48-/-: 6.36 ± 0.71, n = 22; p<0.0001 (****)). (G) Examples of 3 different vegfc-OE muscle grafts (false coloured) in siblings (left panels) and MZyap1mw48-/- mutants (right panels). Merge images show ECs in green, lymphatic and venous ECs are red (yellow) [Tg(fli1a:nEGFP);(−5.2lyve1b:DsRed2)]. Scale bars: 25 μm.