Knockdown of synectin disrupts thoracic duct formation in zebrafish. In all panels, the head of the embryo faces left and dorsal is up. Scale bars represent 100 μm in panels A-B and 50 μm in panels C-D. DA indicates dorsal aorta; and PCV, posterior cardinal vein. (A-D) Confocal images of GFP⁺ vessels in the trunk of 7-dpf Fli1:eGFP^y1 zebrafish embryos, showing the formation of a normal lymphatic thoracic duct (TD) in the control embryo (A,C) but not in the synectin^KD embryo (B,D). Panels C and D represent close-ups of the boxed areas in panels A and B, between the dorsal aorta (DA) and posterior cardinal vein (PCV). In these latter panels, arrows highlight the TD, while asterisks denote absence of TD. (E) Quantification of the TD formation defects after injection of Syn^ATG1 at 7 dpf. Percentages of embryos displaying complete lack of TD, TD formation over 10%-30% or 30%-90% of its normal length, and a normal TD are represented for each treatment group (see also supplemental Table 3). We quantitatively analyzed TD formation by scoring its presence in 10 consecutive somite segments (from somite 5 to somite 15).