Differential Cytoskeletal and Junctional Organization in SECs Across Central and Peripheral ECM Zones. A Representative image of Tg(krt5:Gal4ff)la212; Tg(UAS:LifeAct-GFP)mu271 fin fold central region (green) and peripheral boundary (purple) as defined in Fig. 1D–F. Quantifications of (B) SEC apical area and (C) aspect ratio by violin plot (distribution=individual cells, dots=average values/embryo). (apical area: two-tailed unpaired t test p = 0.4548, n = 83-86 cells, dots n = 6-7; aspect ratio: two-tailed Mann-Whitney test p = 0.1672, n = 48-160 cells, dots n = 5-6; both: 3 independent experiments). D, G Representative images showing (D) cdh1-tdTomatoxt18, alongside immunofluorescence staining for phosphorylated-myosin light chain and (G) desmoplakin1/2 at 48hpf. Z-stack images from SEC-BEC layer. SECs identified by max projection of selected z-slices by z-position. 16-color intensity scale. E, F, H Quantification of intensity for junctional (E) E-cadherin, (F) phospho-myosin light chain, and (H) desmoplakin1/2 across embryos, shown as violin plots (distribution=individual junctional measurements, dots=average values/embryo). Intensity normalized to Center group for each graph (two-tailed Mann-Whitney test on violin plots, p = 0.2577 (E-cadherin), 0.0457 (pMyosin), and p < 0.0001 (Desmoplakin), n = 372 junctions (E-cadherin), 99-119 junctions (pMyosin), and 362-366 junctions (Desmoplakin), dots n = 18 (E-cadherin; 4 independent experiments), 6 (pMyosin; 1 independent experiment), and 18 (desmoplakin; 2 independent experiments) embryos). Source data are provided as a Source Data file. I Representative orthogonal view of the fin fold, showing live imaging of cdh1-tdTomatoxt18 or desmoplakin1/2 immunofluorescence staining in collagen-enriched (center) and laminin-enriched (periphery) regions. (Top) Images displayed using 16-color scale. (Bottom) Interface membrane (yellow dashed lines) between SEC and BEC layers, with numbers corresponding to each analyzed cell. J, K Quantification of interlayer (yellow dashed lines) (J) E-cadherin and (K) desmoplakin across embryos, individual measurements distribution shown as violin plots and average values per embryo as dots. Intensity was normalized to the Center group for each graph (two-tailed Mann-Whitney test on violin plots, p = 0.2917 (E-cadherin) and p < 0.0001 (Desmoplakin), n = 70 (E-cadherin), and 60 cells (desmoplakin), dots n = 7 (E-cadherin; 2 independent experiments) and 6 (desmoplakin; 1 independent experiment) embryos). L Summary schematic of junctional characteristics in SECs, SEC-BEC interface, and BECs. Source data are provided as a Source Data file.
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