Figure 4.

AurA controls mitotic spindle orientation through regulating asymmetric localization of Mud. (A,A′) The mitotic spindle is often misoriented relative to the Mira crescent in aurA¹⁷⁹⁶¹ mutants (A′), in contrast to wild type (A) in which the spindle orientation inferred by two CNN-labeled centrosomes is always aligned perpendicular to the Mira crescent. CNN staining is often lost (A″) or strongly reduced (A′) in aurA⁸⁸³⁹ mutant NBs. In aurA mutants, one (data not shown) or three (A′″) centrosomes can also be observed. The quantification of the distribution of spindle orientation in wild-type (B) and aurA¹⁷⁹⁶¹ mutant (B′) NBs based on NBs that have two CNN⁺ centrosomes. (C–D′) AurA is required for Mud asymmetric cortical localization but not its centrosomal localization. (C) In wild-type metaphase NBs, Mud is asymmetrically localized as a cortical crescent at the apical cortex as well as to both centrosomes. (C′) In contrast, in aurA metaphase NBs, Mud is delocalized to almost the entire cortex but remains localized to both centrosomes (arrow). (D,D′) Mira is asymmetrically localized in both wild-type NBs (D) and aurA mutant (D′).