Aurora kinases promote mitotic progression and asymmetric cell division through 1 activation of Polo kinase 2 3

Organ development and integrity requires the maintenance of a defined and restricted pool of dividing stem cells. This process requires the coupling of mitosis progression to the establishment of stem cells polarization and spindle orientation to ensure that they retain the ability to proliferate while their descendant cells do not proliferate excessively. How this coupling occurs is unknown. Here we show that downstream of Aurora kinases, Polo activity levels are crucial for timely mitotic progression independently from the Spindle Assembly Checkpoint (SAC). In addition, Polo functions downstream of Aurora A to ensure cortical polarity and spindle orientation in neural stem cells, thereby preventing excessive cellular proliferation in developing larval brains, and suppressing tumor development. In addition, induction of aneuploidy in polo mutant brain by inactivation of the SAC leads to an increase in tumor development Altogether, our results reveal that the Aurora-Polo kinase axis is an essential module coupling mitotic progression to asymmetric division in NSCs.