Presence of large microvilli-lined inclusions contain apical membrane components in Myo5b KO mice. (A and B) Immunostaining for the apical protein P-ERM (red) and the brush border enzyme DPPIV (green) showed apical localization in control mice. Myo5b KO mice exhibited numerous P-ERM–positive inclusions, many of which contained DPPIV. The basolateral protein p120 (white) delineates individual cells. Scale bars = 5 µm. (B) High-magnification image shows close association of inclusions with the apical membrane and internalized DPPIV. (C) The apical endosomal protein endotubin (red) normally localizes to tubular endosomes of the apical endosome complex immediately below the enterocyte brush border of neonatal control mice. In Myo5b KO enterocytes, endotubin can be seen surrounding numerous large intracellular inclusions. Scale bars = 2 µm. (D) Endotubin is closely associated with multiple inclusions that remain contiguous with the apical membrane in Myo5b KO enterocytes. Scale bars = 5 µm. n = 6 mice per group.