Conversion of hepatocyte biaxial polarity into vectorial apico-basal polarity. (a) Down-regulation of occludin impairs the lumen formation in differentiating and polarizing hepatoblasts. Immunofluorescence images of cells stained for the apical marker CD13 and occludin. Scale bar: 10 µm. (b) Down-regulation of the TJ protein ZO-1 impairs the lumen formation in differentiating and polarizing hepatoblasts. Immunofluorescence images of cells stained for ZO-1. Scale bar: 10 µm. (c) Down-regulation of Cdc42 leads to spherical lumina instead of BC in polarizing hepatoblasts. The polarity is not perturbed, as apical markers CD13 and ZO-1 still localized to the formed lumina. Scale bar: 10 µm. (d) Down-regulation of Rab35 leads to profound changes in lumen morphology of polarizing and differentiating hepatoblasts. The cells form multicellular structures with a shared lumen positive for apical markers CD13 and ZO-1. Immunofluorescence images of cells treated with three different siRNAs. Scale bar: 10 µm. (e) Estimation of knock-down efficiency of six siRNAs designed to target Rab35 mRNA 96 h post-transfection in differentiating and polarizing hepatoblasts in vitro (n = 2, SD).