Septins control the apicobasal distribution of epithelial MTs. (A and B) Confocal xz images of contact-naive and polarizing MDCK cells stained for SEPT2 and α-tubulin. Schematics show position of SEPT2 filaments with respect to the nucleus (blue). Bars, 2.5 µm. (C and D) Side views of 3D-rendered confocal images of MDCK cells plated on Transwell filters for 12 h (late stages of polarization) and 48 h (polarized). Arrows point to SEPT2 filaments that arch from the basolateral to the apical cytoplasm. Images were γ adjusted. Bars, 5 µm. (E) Confocal microscopy slices taken from the basal, medial, and apical sections of MDCK cells (24 h on Transwell) treated with control and SEPT2 siRNAs and stained for SEPT2 and EB1. (F) Graph shows the percentage of EB1 comets distributed in the apical, medial, and basal cytoplasm of control (n = 16) and SEPT2-depleted (n = 18) MDCK cells. α-tub, α-tubulin. Error bars represent SEM.