(A?B?) Orthogonal projections in the YZ plane of a 52 hpf snai1b+/+ heart (A) immunostained for ?-catenin epitope ?-18, N-cadherin, and GFP compared with a snai1b-/- sibling heart (B). Close-up of boxed areas of snai1b+/+ (A?) and snai1b-/- (B?) CMs. Schematics illustrate the localization of activated ?-catenin (magenta) in the basal domain of extruding CMs in snai1b-/- embryos and defects in N-cadherin (yellow) localization in the junctional domain of snai1b-/- CMs (A??B?). (C?D?) Fluorescence intensity profile (FIP) (C?D) and mean fluorescence intensity (mFI) (C??D?) of ?-catenin epitope ?-18 and N-cadherin immunostaining in 52 hpf snai1b+/+ and snai1b-/- CMs, and in snai1b+/+ and snai1b-/- extruding CMs. The ?-catenin epitope ?-18 is observed in the basal domain (white arrowhead in B?) of extruding CMs (white asterisks in B?) in snai1b-/- embryos, and a reduction in junctional N-cadherin (red arrowhead in B?) is observed in snai1b-/- CMs. (FIP ?-catenin epitope ?-18: snai1b+/+ CMs, N = 179; snai1b+/+ extruding CMs, N = 60; snai1b-/- CMs, N = 140; snai1b-/- extruding CMs, N = 54; mFI ?-catenin epitope ?-18: snai1b+/+ CMs, N = 90; snai1b+/+ extruding CMs, N = 24; snai1b-/- CMs, N = 88; snai1b-/- extruding CMs, N = 44. FIP N-cadherin: snai1b+/+ CMs, N = 90; snai1b+/+ extruding CMs, N = 12; snai1b-/- CMs, N = 98; snai1b-/- extruding CMs, N = 49; mFI N-cadherin: snai1b+/+ CMs, N = 90; snai1b+/+ extruding CMs, N = 25; snai1b-/- CMs, N = 92; snai1b-/- extruding CMs, N = 70.) (E?F?) Representative images of a 52 hpf snai1b-/- heart (F) immunostained for p-myosin and GFP compared with a snai1b+/+ sibling heart (E). Schematics illustrate the basal enrichment of p-myosin (magenta) in extruding CMs in snai1b-/- embryos (E??F?). (G?G?) FIP (G) and mFI (G?) of p-myosin immunostaining in snai1b+/+ and snai1b-/- CMs, and in snai1b+/+ and snai1b-/- extruding CMs. p-myosin is enriched basally (orange arrowheads in F?) in snai1b-/- extruding CMs in (white asterisks in F?). (FIP p-myosin: snai1b+/+ CMs, N = 204; snai1b+/+ extruding CMs, N = 60; snai1b-/- CMs, N = 140; snai1b-/- extruding CMs, N = 49; mFI p-myosin: snai1b+/+ CMs, N = 100; snai1b+/+ extruding CMs, N = 29; snai1b-/- CMs, N = 153; snai1b-/- extruding CMs, N = 48). Plot values represent means ± S.E.M. (C, D, G). In the violin plots (C?, D?, G?), solid black lines indicate median. p-values determined by Kruskal?Wallis test (C?, D?, G?). Scale bars: 20 µm (A, B, E, F); 2 µm (A?, B?, E?, F?). ap: apical; ba: basal; N: number of CMs. See also Figure 2?figure supplement 1.
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