Fig. 1

(A) Possible modes of Wnt-Fz/PCP function in ppl migration. The direction of ppl (green) migration (black arrows) could be influenced by an attracting or repellent gradient of Wnt-Fz/PCP signaling (purple), which polarizes ppl cells, and thus directs their migration instructively. Alternatively, uniform Wnt-Fz/PCP signaling could operate in a permissive mode, allowing ppl cells to undergo directed migration by for example controlling general cell motility. (B) Animal (left column) and lateral (right column) views of the notochord (nc) and prechordal plate (ppl) in wt (upper row) and MZfz7a/b mutant (lower row) embryos at the end of gastrulation (bud stage, 10hpf) labeled by in situ hybridization for hgg (ppl), ntl (nc), and papc (paraxial mesoderm). Scale bar, 250 μm. (C,D) Length-to-width ratio of the ppl (C) and distance between the anterior end of the nc and the posterior end of the ppl (D) in wt (green) and MZfz7a/b mutant (purple) embryos. Error bars are standard deviations; N = 23 (wt), 17 (MZfz7a/b), ***p<0.001 (Student’s t-test). (E) Schematic of embryo orientation used for imaging ppl and overlying neurectoderm (ne) movements in (F). Neurectoderm, magenta; ppl and nc, green; boxed area corresponds to the imaged area in (F). (F) Confocal microscopy images of wt (upper row) and MZfz7a/b mutant (lower row) embryos at mid (left, 75% epiboly) and late (right, bud stage) gastrulation. Nuclei are marked by H2A-mCherry expression, and ppl and nc are marked by gsc:GFP-CAAX expression. Scale bar, 50 μm. (G) Local correlation between leading edge ppl cells and overlying ectodermal cells in wt (green) and MZfz7a/b mutant (purple) embryos. X-axis, time (min, stage); y-axis, order parameter of local correlation; error bars are standard error of mean; N = 3 per genotype. (H) Velocities of ppl leading edge cells in wt (green) and MZfz7a/b mutant (purple) embryos. X-axis, time (min, stage); y-axis, velocity in vegetal to animal pole direction; error bars are standard error of mean; N = 3 per genotype.