Fig. 1

Notch mediates the local patterning of the trunk vasculature. (A) Quantification of the ratio of arterial and venous ISVs in a 10-somite region of the trunk of 6 dpf wild-type embryos (n=3 experiments, 74 embryos, 1480 ISVs). (B) Ipsilateral neighbourhood analysis of vessel identity with two neighbours in 6 dpf wild-type embryos (n=3 experiments, 74 embryos, 1184 ISVs). (C) Contralateral neighbourhood analysis of vessel identity in 6 dpf wild-type embryos (n=3 experiments, 74 embryos, 1480 ISVs). (D) Stills from time-lapse movie ( Movie 1) of a Tg[fli1a:EGFP]^y1/Tg[-0.8flt1:RFP]^hu5333 embryo showing ISV remodelling into a venous (left) and an arterial (right) intersegmental vessel (vISV and aISV). The double transgenic labelling with GFP expression in all ECs and RFP expression in arterial ECs facilitates distinction between arterial (yellow) and venous (green) structures. In both cases, a lumenised connection is formed between the secondary sprout and the primary ISV (arrowheads). Magnifications show lumenised connections in a future vISV (1) and a future aISV (2). In the case of the formation of an aISV, the connection is lost again and the secondary sprouts form lymphatic precursors at the horizontal myoseptum (parachordal lymphangioblasts, PL). In case of vISV remodelling, the secondary sprout connection is stabilised and the connection between primary ISV and DA regresses. (E) Tg[fli1a:EGFP]^y1 embryos mosaically expressing a pT2Fli1ep-zN1aICD-basfli-mCherry construct (NICD^OE) at 50 hpf. Lymphangiogenic sprouts, i.e. sprouts delivering lymphatic precursors at the horizontal myoseptum (arrowheads), can be observed at the position of NICD overexpressing (NICD^OE) ISVs (asterisks). Arrow points to a venous ISV connection. (F) Tg[fli1a:EGFP]^y1 embryos mosaically expressing a pT2Fli1ep-zN1aICD-basfli-mCherry construct at 6 dpf. NICD^OE mCherry-positive cells were found almost exclusively in the arterial compartment of the vasculature. (G) Quantification of the ratio of arterial and venous ISVs in a 10-somite trunk region of 6 dpf control embryos (n=3 experiments, 74 embryos) and mosaic NICD^OE embryos (n=3 experiments, 51 embryos). In mosaic embryos, the arterio-venous distribution was quantified overall and separately in NICD^OE and wild-type ISVs. Wild-type ISVs compensate for the forced arterialisation of NICD^OE ISVs by increased formation of venous connection. (H) Quantification of the percentile presence of arterial and venous ISVs in a 10-somite region of the trunk of 6 dpf NICD^OE embryos. Mosaic NICD^OE embryos represented in G were grouped based on their relative number of NICD^OE ISVs (<20%, 20-30% or >30%; n=13, 26 and 12 embryos, respectively). (I) Ipsilateral neighbourhood analysis of vessel identity with two neighbours in 6 dpf NICD^OE embryos (n=3 experiments, 40 embryos, 592 ISVs) compared with wild-type embryos (n=3 experiments, 74 embryos, 1184 ISVs). A, artery; DA, dorsal aorta; PCV, posterior cardinal vein; ISV, intersegmental vessel; PL, parachordal lymphangioblasts; V, vein; WT, wild type; NICD^OE, NICD overexpressing. Scale bars: 50 μm.