Microtubules tethered at epithelial cell junctions by dynein facilitate efficient junction assembly.

Efficient remodeling of cell-cell adhesions is critical during development and morphogenesis. Junctional components must be specifically and rapidly transported to sites of junction assembly. In this study, we show a mechanism by which this targeted trafficking may occur. Microtubules target epithelial adherens junctions, and the number of microtubules both projecting to and tethered at sites of contact is increased during junction assembly, consistent with an increased need for new material at the nascent junction. Cytoplasmic dynein is localized to sites of cell-cell contact, and microtubules project to dynein patches where they become tethered. Microinjection of anti-dynein antibodies disrupts the tethering of microtubules, showing that the motor anchors them. Furthermore, disruption of dynein inhibits junction formation. Immunocytochemistry with antibodies to p120 catenin support the hypothesis that tethered microtubules serve as tracks for delivery of new components to forming junctions, suggesting a model in which material is targeted for delivery to sites of need through microtubules tethered by dynein.