Fig. 2

Pcdh18a is involved in the migration of SCPs. (A) VE-DIC microscopy of whole-mount in situ hybridization for pcdh18a at 25 hpf. Arrows point to pcdh18a-expressing cells at the ventral side of caudal somites, including emigrating SCPs. Some spinal cord neurons are also labeled (red asterisks). The dashed square delimits the region enlarged below. (Ba) The splice-blocking MO used in this study targets the intron 1-exon (E) 2 junction of pcdh18a. Asterisk indicates the intron retained in the morphant. (Bb) Injection of this MO leads to retention of the first intron and a premature STOP codon in it, resulting in a protein truncated after the 106th amino acid of the ICD of Pcdh18a. (Bc) Alignment of SH3, WIRS and Dab1 domains in the ICD of human (h) PCDH18 and zebrafish (z) Pcdh18a. (Ca-Cd) Time-lapse confocal imaging of Tg(pax3a:GFP; TCF:nls-mCherry) control or pcdh18a-ΔCP106 morphant embryos (maximum projections). Arrows and arrowheads indicate delaminating and migrating SCPs/SCs, respectively. Scale bars: 30 µm. (e,f) Snapshots of single SCPs during mid-migration (26-29 hpf). Scale bars: 10 µm. (Da,Db) Individual tracks of five leader SCPs from a control (Da) and a pcdh18a-ΔCP106 morphant embryo (Db); cell positions plotted every 10 min over 6 h; x,y coordinates of the SCPs' starting points (within the somite ventral clusters) are set to (0,0), and negative or positive values on the x-axis indicate anterior or posterior migration, respectively. (Dc) Overlay of individual tracks of the 30 leader cells followed in control (black) and pcdh18a-ΔCP106 morphant (orange) embryos. nexp=3, nembryos=6 for controls and morphants. (Dd) Trajectory straightness of the tracked leader SCPs (mean±s.d.; *P=0.038; unpaired, two-tailed Student's t-test). (Ea) Average speed of the tracked leader SCPs over time. E, early migration; D, decision phase; L, late migration. (Eb) Violin plot of the speed of leader SCPs during their early migration (median±s.d.; ****P<0.0001; Mann–Whitney test).