Dynamic centriolar relocalization of Polo kinase and Centrobin in early mitosis primes centrosome asymmetry in fly neural stem cells

Centrosomes, the main microtubule organizing centers (MTOCs) of metazoan cells, contain an older 9mother9 and a younger 9daughter9 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 dynamics and mechanisms regulating centrosome asymmetry and biased centrosome segregation are unclear. Using 3D-Structured Illumination Microscopy (3D-SIM) and live cell imaging we show that in fly neural stem cells (neuroblasts) the mitotic kinase Polo and its centriolar protein substrate Centrobin (Cnb) dynamically relocalize from the mother to the daughter centriole during mitosis. This mechanism generates a centrosome, containing two molecularly distinct centrioles by telophase. Cnb9s timely relocalization is regulated by Polo-mediated phosphorylation whereas Polo′s daughter centriole enrichment requires both Wdr62 and Cnb. Based on optogenetic protein mislocalization experiments we propose that the establishment of centriole asymmetry in mitosis primes biased interphase MTOC activity, necessary for correct spindle orientation.