Fig. 3

Polydom/svep1 mutants show reduced venous and lymphovenous sprouting. A and F, Quantification of sprouts from the posterior cardinal vein (PCV) in wild-type (wt) siblings and polydom/svep1 mutants, in plcg1 morphant embryos. Knockdown of plcg1 suppresses arterial formation, hence only venous structures can be observed in a fli1a:GFP transgenic background. Heterozygous embryos show a significant reduction in venous sprouting events from the PCV, and this is further exacerbated in mutant embryos at 54 h post-fertilization (hpf; wt siblings: n=29, heterozygous embryos: n=53, and polydom/svep1 mutants: n=26). B, Still frames from confocal time-lapse imaging of a wt sibling and polydom/svep1 mutant embryo in a fli1a:GFP; flt1^enh:RFP double transgenic background are shown over the course of 32.5 to 46.5 hpf. Both the number of secondary sprouts from the PCV (yellow arrowheads) and parachordal lymphangioblast (PL) cells (white arrowheads) were reduced in mutant embryos. C and G, polydom/svep1 mutant embryos form a reduced number of PLs at the horizontal myoseptum (HMS) region. Confocal images of wt sibling and polydom/svep1 mutant embryos at 48 hpf in fli1a:GFP;flt1^enh:RFP background and quantification of PLs at 54 hpf (wt siblings: n=8, heterozygous embryos; and n=11, polydom/svep1 mutants: n=6). D, PL cells at the level of the HMS fail to migrate along intersegmental arteries in the polydom/svep1 mutants. Still frames from confocal time-lapse imaging of a wt sibling (a–c) and a polydom/svep1 mutant embryo (d–f) in a fli1a:GFP transgenic background are shown over the course of 2.5 to 3.5 d post-fertilization (dpf). E and H, An increased number of arterial intersegmental vessels (ISVs) at the expense of venous ISVs in polydom/svep1 mutants is highlighted by flt1^enh:RFP expression in fli1a:GFP background at 5 dpf (siblings: n=20, polydom/svep1 mutants: n=10). Values are presented as means±SD. **P<0.01; ***P<0.001.