Figure 7.

PCP is altered and cell bond tension is reduced upon loss of smash function. (A and B) Smash^35null embryos (A) and WT embryos (B) at stage 8 stained for Baz. Right: Higher-magnification views of the boxed areas in corresponding left panels. (C) Quantification of planar polarization of Baz, Cno, Rok, and Sqh in stage 8 embryos. ***, P < 0,001; *, P < 0.05; ns, not significant. For Baz, n = 160 cell contacts analyzed per genotype; for all other proteins, n = 200 cell contacts analyzed per genotype. (D and E) Live imaging of laser ablation of single cell bonds in the epidermis of smash^35null (D) and control (E) third instar larvae. The ZA was marked with DE-cad-GFP. The time (seconds) relative to the time point of laser ablation (0) is given in each panel. The distance (double-headed yellow arrows) between vertices (yellow circles) of the ablated cell bond was measured over time. (F) Quantification of vertex distance increase over time in WT and smash^35null larvae. Mean vertex displacement amplitude ± SEM: WT (20 s) 0.896 ± 0.462 µm, smash³⁵ (20 s) 0.346 ± 0.353 µm; *, P = 0.0279; WT (40 s) 1.297 ± 0.352 µm, smash³⁵ (40 s) 0.485 ± 0.055 µm; ***, P = 5.998 × 10⁻⁵; WT (60 s) 1.729 ± 0.490 µm, smash³⁵ (60 s) 0.649 ± 0.182 µm; ***, P = 0.00014; mean vertex displacement speed ± SEM in first 60 s: WT 0.029 ± 0.007 µm/s, smash³⁵ 0.011 ± 0.003 µm/s; ***, P = 0.00014. P-values were determined using the two-sided unpaired t test. n = 7 representative videos were analyzed for each genotype. (G) Smash (green) localizes to the ZA of third instar larval epidermal cells. DNA was stained with DAPI (cyan). The image is a maximum-intensity projection of three adjacent optical sections at the level of the ZA taken with the Airyscan detector. Bars: (A and B) 10 µm; (D, E, and G) 20 µm. In A and B, anterior is to the left and dorsal is up. Error bars in C and F show mean ± SEM. See also Video 5.