Fig. 6

Disruption of pk1b or pk1a causes NCCs to adopt aberrant polarity. To assay the polarity of NCCs, MTOCs in NCCs were labeled by injecting either XCentrin-EGFP RNA in one-cell stage Tg(sox10:mRFP) or Cherry-XCentrin RNA in one-cell stage Tg(sox10:EGFP) embryos that were also injected with H2B-CFP to label nuclei. Fixed, deyolked, flat-mounted 24 hpf embryos were imaged in dorsal view (A). Scale bar = 10 µm. The angle θ of the MTOC relative to the nucleus and the AP body axis (B) was measured for each cell and quantified using Fiji. (C-F) Polar histograms generated using MATLAB show the polarity of assayed NCCs. In all cases, the Watson-Williams F-test was used to measure statistical significance between conditions as well as with a randomly-distributed polar histogram. In WT embryos, NCCs (n = 48 cells, 5 embryos) were polarized along the mediolateral axis (C), with WT cells showing a significant difference from a random distribution (***, p < 0.001). However, in pk1b-morphant specimens (n = 42 cells, 3 embryos) (D) and pk1a^ch105/ch105 specimens (n = 40 cells, 3 embryos) (E) NCCs were polarized along the AP axis. As compared to WT NCCs, the distributions of both pk1b-morphant and pk1a^ch105/ch105 NCCs were significantly altered, and also showed a significant difference from random distributions (***, p < 0.001 for each case). However, double-heterozygous pk1a^ch105/+; pk1b^fh122/+ NCCs (n = 71 cells, 4 embryos) (F) showed no statistically significant difference as compared to a random distribution (p > 0.05), indicating that disrupting one copy each of the pk1a and pk1b genes is sufficient to randomize NCC polarity.