Fig. 6

Secondary sprouting is defective in grb2b mutant embryos. a–fʹʺ Still images taken from overnight videos (see Supplementary movies 1–3) and corresponding schematic cartoons of wild type (a–bʹʺ) and grb2b^mu404 mutant (c–fʹʺ) embryos between 30hpf and 48hpf, showing different sprout behaviors. a In wild-type embryos, cells sprout from the PCV and either form PLs at the HM or remodel an intersegmental artery into a vein. c, e Still images of two different grb2b mutant embryos. The arrow in cʹ–dʹʺ highlights a cell attempting to sprout from the PCV and extending towards an aISV, but failing to establish a stable connection. The arrowhead in e and f points at an endothelial cell with a small filopodium that retracts. The arrows in pictures from e to fʹʺ point at an endothelial sprout that reaches an aISV, establishes a stable connection and remodels the artery into a vein. In all images flt4:mCitrine is shown in green and flt1:tdTomato in red. g Quantification of the different sprout behaviors observed between 31 and 48hpf (indicated as percentage). For quantification, both sides of a four segments stretch per embryo were analyzed. wt: n = 5, het: n = 16, mut: n = 23. Scale bars: 25 µm. Data in d are mean ± sd