Spindle orientation is regulated by a conserved mechanism in which Pins/LGN anchors Mud/NuMA to the cell cortex. This pathway has been assumed to operate in nearly all animal cell types but here (p. ) Daniel St Johnston and colleagues reveal that Pins is not required for spindle orientation in the Drosophila wing disc. Using live imaging, they first discover that spindle angles in the wing disc vary widely; spindle angles are initially random but gradually align with the plane of the tissue as cells enter anaphase, highlighting that spindle angles are not accurate predictors of division orientation until this point. Importantly, the researchers reveal that spindle orientation does not require Pins, or aPKC, Dlg or Lgl. They further report that Mud is able to localize to the cell cortex in the absence of Pins, suggesting that a parallel but as yet unknown mechanism must act to localize Mud in wing disc cells. In summary, these surprising results indicate that a Pins-independent mechanism can orient the mitotic spindle in the Drosophila wing disc and lead the authors to propose that this system provides robustness to this rapidly developing epithelial tissue.
