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Fig. 1
SIV development and maturation
(A-D) A model representing four phases of SIV plexus development in the zebrafish embryo between ~36 and 84 hpf. The SIV plexus is blue, and the dorsal aorta (DA), posterior cardinal vein (PCV), and intersegmental vessels are marked in grey. Single endothelial cells sprout ventrally and separate from the PCV (A) to form a primary SIV branch (B). Angiogenic sprouts grow out of the primary SIV and fuse to each other, forming a reticular plexus with multiple cross branches (C, red) and vascular loops (C, green); simultaneously, the plexus grows and moves ventrally. Eventually, the cross branches (and hence the loops) are removed, and the plexus simplifies, forming a set of parallel vertical branches draining into a large ventral SIV branch (D). (A′-E′) Stills from a SPIM time-lapse movie representing five phases of SIV development corresponding to models in A. (A′′-E′′) Stills from a SPIM time-lapse movie representing SIV development in a silent heart morphant embryo corresponding to models in A. In this case, the SIV keeps its reticular structure because of impaired pruning. (F) A graph comparing the SIV vascular loop formation and remodeling in a wild-type (grey) and silent heart embryo (orange), based on SPIM time-lapse experiments between 36 and 84 hpf. From the left, showing the number of cross branches pruned during remodeling phase, the number of cross branches/loops closed via collateral fusion, the number of cross branches/loops remaining until the end of the movie, and the sum of all loops observed throughout the movie. The values are average numbers per SIV plexus with standard deviation (n = 19 for wild type [WT] and n = 9 for silent heart [SIH]). *** p < 0.001. (G) A graph showing the percentage contribution of pruned (grey), closed by collateral fusion (orange), and remaining (blue) vascular loops to all events observed in WT versus silent heart embryos. See also S1 and S2 Figs, S4 Movies, S1 Data.