Fig. 4: TAp73 regulates cilia organization and polarized junctional MT assembly required for rPCP, and is essential for the subcellular arrangement of the microtubule organizing protein, Fat4.

a–i Representative confocal images of WMs from WT, p73KO (a, b, c–f, h), TAp73KO (b′, g, i) and DNp73KO (b″) mice stained with the indicated antibodies. b, b″ Immunostaining against α-tubulin (red) was used to visualize the cilia axoneme. Scale bar: 10 µm. Parallel and organized bundles of cilia in WT and DNp73, but disorganized in p73KO and TAp73KO-ECs are marked by yellow arrows. White arrows indicate cells lacking cilia axoneme. c, d To delineate cilia polarity and quantified rPCP, combined staining of FGFR1 Oncogene Partner (FOP, blue) and γ-tubulin (red) on WT and p73KO WMs was performed. Scale bar: 5 µm. The direction of each BBs was drawn by a vector (white arrows) from FOP-dot to γ-tubulin-dot within a BB. An angle of polarity, named rotational angle (RA), was drawn with respect to the horizontal axis for each BB and the mean RA for each cell was determined. d Mean vectors and circular standard deviation (CSD) of RAs around the mean in WT and p73KO were calculated (n = 105 cells from five mice per genotype). Data were graphically represented using Oriana software and statistically compared by circular analysis (Watson’s U2 test). e–g Representative confocal images of WMs from the indicated genotype stained for α-tubulin to mark MTs (e, green) and for EB3 to determine MT polarization (e′, green; f, g, red). e Arrowheads indicate the MT-meshwork underlying BB-clusters. Scale bar: 5 µm. e′–g White arrows show a second polarized MT network located at anterior intercellular junctions illustrating their coordinated orientation. Scale bar: 5 µm. h, i WMs from WT and p73KO (h) or TAp73KO (i) mice were stained against Fat4 (green), γ-tubulin (red), and β-catenin (blue). Scale bar: 5 µm. h Fat4 polarized distribution was indicated by dashed arrows. Orthogonal projections show the close association of Fat4 and the BBs indicated by a white arrow