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Fig. 4 Tissue architecture and Fn localization improve without rescue of polarity. (A-I) Transverse confocal sections of the right lateral mesoderm in zebrafish embryos expressing Tg(myl7:egfp) (green). Dorsal is up. ZO-1 (red) and Fn (blue) are detected by immunofluorescence. The boxed regions in A-C are shown at higher magnification in D-I. Scale bars: 10 μm. (J-L) Schematics of the cardiomyocyte-associated localization of ZO-1 (red) and Fn (blue) as shown in D-I. Wild-type cardiomyocytes are organized in a cohesive layer (A) and exhibit lateral localization of ZO-1 (D,J, arrows) and basal deposition of Fn (D,G,J, arrowheads). In han embryos, tissue architecture is aberrant (B) and myocardial apicobasal polarity is not evident (E,H,K). ZO-1 is diffuse or absent (E,K, arrows) and Fn deposition is disorganized (E,H,K). In han-/-;nat+/- embryos, myocardial cohesion (C) and basal Fn localization (F,I,L, arrowheads) are improved, but polarity is not consistently rescued: localization of ZO-1 is either lateral or absent (F,L, arrows).