Zebrafish expando mutants lack lymphatic vessels and venous sprouting. (A,B) Lateral views of TG(fli1:GFP) expression in wild-type (wt; A) and expando mutant (B) larvae at 5 dpf demonstrate that overall vascular patterning is not perturbed in expando mutants. (C,D) Overlay image of angiogram (red) and TG(fli1:GFP) (white) indicating the presence of blood flow in wild-type (C) and mutant (D) embryos. The thoracic duct (arrows) is present in the wild type, but absent (asterisks) from mutant larvae. (E,F) Lateral views of wild type (E) and expando mutant (F) in a double-transgenic TG(fli1:GFP), TG(kdr-l:Cherry) background. All lymphatic vessels are absent in mutants at 5 dpf. Arrows indicate the thoracic duct (td), intersegmental lymphatic vessels (islv) and dorsal longitudinal lymphatic vessels (dllv) in wild-type embryos. Asterisks indicate their absence in expando mutants. (G,H) Parachordal lymphangioblasts (PLs) are absent from the horizontal myoseptum in expando mutants (asterisk in H) as compared with wild-type siblings (arrow in G indicates PL) in the double-transgenic TG(fli1:GFP), TG(kdr-l:Cherry) background at 54 hpf. (I,J) tie2 expression in venous sprouts (arrows in I) is absent in expando mutants (J). n=6/29 embryos scored and confirmed by genotyping.
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