Fig. 8

Etv2 function is required for induction of lymphangiogenesis by Vegfc. (A-F) Parachordal lymphangioblasts (PL) were analyzed at 52 hpf in fli1a:GFP transgenic line, and visualized by GFP fluorescence, while Etv2 depletion was achieved by UV photoactivation of previously described photomorph solution. (A) Control uninjected larva; (B) Etv2 photomorph injected and never photoactivated larva; (C) Etv2 photomorph injected larva, uncaged at 6 hpf (shield stage); (D) Etv2 photomorph injected larva, uncaged at 24 hpf; (E) Heat-shock Vegfc overexpressing larva, Etv2 depleted by photoactivation at 24 hpf; (F) Larvae injected with heat shock overexpression Vegfc construct only. Note that at this stage there are very few lymphangioblasts in the control larvae (A), while greatly increased number and precocious formation of parachordal lymphangioblasts is observed in Vegfc overexpressing larvae (F, arrows), which are reduced upon Etv2 depletion (C-E). (G) Average number of lymphatic precursor cells per segment. Analysis was accomplished by counting the number of parachordal lymphangioblasts in ten intersegmental spaces over the trunk of each larva per group. The average number of PLs per segment was then determined. Mean values ± SEM are shown. Note that the larvae were analyzed at 52 hpf, prior to the emergence of PLs in the control group. Larvae that were uncaged at 6 hpf (shield stage) had abnormal vasculature that made calculation of PLs impossible (ND, not determined) (C). The experiment has been replicated twice.