Figure 1

Dkk1 Disrupts Collective Cell Migration Independently of Cell Fate

(A) Expression of dkk1 (green) and goosecoid (gsc, red) from 30% to 70% epiboly (EB), using RNAscope. Confocal imaging, dorsal view with anterior to the top. Maximum projection in the left panels, 5 μm z stacks at higher magnification on the right. Single-plane image at 80% EB shows dkk1 transcripts overlapping with gsc transcripts at the boundary of the gsc-expressing region. Scale bar, 10 μm.

(B) Progression of axial cells. Confocal maximum projections from shield to 80% epiboly stages in transgenic Tg(gsc:GFP) embryos, with or without injection of Dkk1 RNA. Embryos are shown in dorsal view with anterior to the top. Scale bar, 100 μm. See also Video S1.

(C) Maximum projections of anterior axial cells from time-lapse confocal imaging of Tg(gsc:GFP) embryos showing a lack of progression of the prechordal plate (green) in Dkk1-expressing embryos. Embryos were imaged at 75% epiboly for a time (t) period of 48 min. The dashed line shows the position of the anteriormost prechordal plate cells at the first and last time point (t = 0 min and t = 48 min, respectively). Scale bar, 20 μm. See also Video S2.

(D) Tracking of migrating axial cells from Tg(gsc:GFP) embryo time-lapse videos from 70% to 90% epiboly at 2-min intervals (n = 3 for each condition). Tracks from individual cells from one representative embryo for each condition are shown. Axial cells in Dkk1-expressing embryos move slower and exhibit reduced persistence and displacement. ^∗p < 0.05 and ^∗∗p < 0.01; p values were calculated using linear mixed-effects models.

(E) Dkk1 cell migration behavior is independent of transcriptional regulation of β-catenin target genes. 24 h post-fertilization (hpf) embryos (left) and confocal maximum projections of Tg(gsc:GFP) embryos at 80% epiboly (EB) (right). The Dkk1-induced cell migration defect persists in embryos at 80% EB lacking Tcf3a (Tcf3 KD). See also Figures S1A and S1B.