Centrosome Asymmetry in Fly Neural Stem Cells is Established in Early Mitosis Through Dynamic Mother to Daughter Centriole Relocalization of Cnb and Polo

Centrosomes, the main microtubule organizing centers (MTOCs) of metazoan cells, contain an older ‘mother’and a younger ‘daughter’centriole. Stem cells either inherit the mother or daughter centriole-containing centrosome, providing a possible mechanism for biased delivery of cell fate determinants. However, the molecular mechanisms regulating centrosome asymmetry and biased centrosome segregation are unclear. Using 3D-Structured Illumination Microscopy (3D-SIM) we show that in fly neural stem cells (neuroblasts) the mitotic kinase Polo and its substrate the centriolar protein Centrobin (Cnb) relocalize from the mother to the daughter centriole during mitosis. Cnb’s dynamic relocalization is regulated by Polo-mediated phosphorylation, whereas Polo requires both Wdr62 and Cnb. This switch in protein localization generates a centrosome that contains two molecularly distinct centrioles which separate at the end of mitosis. We propose that in fly neuroblasts the establishment of centriole asymmetry during mitosis is necessary for biased interphase MTOC activity, spindle orientation and asymmetric centrosome segregation.