Dynein-Mediated Regional Cell Division Reorientation Shapes a Tailbud Embryo.

Regulation of cell division orientation controls the spatial distribution of cells during development and is essential for one-directional tissue transformation, such as elongation. However, little is known about whether it plays a role in other types of tissue morphogenesis. Using an ascidian Halocynthia roretzi, we found that differently oriented cell divisions in the epidermis of the future trunk (anterior) and tail (posterior) regions create an hourglass-like epithelial bending between the two regions to shape the tailbud embryo. Our results show that posterior epidermal cells are polarized with dynein protein anteriorly localized, undergo dynein-dependent spindle rotation, and divide along the anteroposterior axis. This cell division facilitates constriction around the embryo's circumference only in the posterior region and epithelial bending formation. Our findings, therefore, provide an important insight into the role of oriented cell division in tissue morphogenesis.