FOCAL POINT Nasser Rusan (left) and Dorothy Lerit (right) explore how and why the centrosomes of Drosophila neuroblasts show asymmetric levels of microtubule nucleation and organizing activity. During interphase, the pericentrin orthologue PLP is enriched on the basal, mother centrosome, where it restricts the recruitment of Polo kinase, the master regulator of centrosome maturation and activity. In wild-type neuroblasts (center), the microtubule-nucleating protein γ-tubulin (green) only localizes to the active centrosome on the apical side of the cell. But in PLP-null cells (right), γ-tubulin is active at both centrosomes (red), which limits the ability of neuroblasts to separate their centrosomes and efficiently segregate them into different daughter cells.

PHOTO COURTESY OF BRIAN GALLETTA