Actin dynamics drive microvillar motility and clustering during brush border assembly

Abstract

During differentiation, transporting epithelial cells generate large arrays of microvilli known as a brush borders to enhance functional capacity. To develop our understanding of brush border formation, we used live cell imaging to visualize apical surface remodeling during early stages of this process. Strikingly, we found that individual microvilli exhibit persistent active motility, translocating across the cell surface at ~0.2 m/min. Perturbation studies with inhibitors and photokinetic experiments revealed that microvillar motility is driven by actin assembly at the barbed-ends of core bundles, which in turn is linked to robust treadmilling of these structures. Because the apical surface of differentiating epithelial cells is crowded with nascent microvilli, persistent motility promotes collisions between protrusions and ultimately leads to their clustering and consolidation into higher order arrays. Thus, microvillar motility represents a previously unrecognized driving force for apical surface remodeling and maturation during epithelial differentiation.