Model of polyploid mitotic division containing multiple centrosomes and nuclei. Top: When a cell with two nuclei (red dots) undergoes NEBD, an Ncd/HSET-dependent clustering step gathers extra centrosomes in multiple active MTOCs. As kinetochore-MT attachments become stabilized, chromosomes can be positioned between two spindle poles and inhibit their coalescence, acting as a physical barrier to bipolarity. At anaphase, chromosomes are segregated into multipolar arrays, giving rise to more than two nuclei. Bottom: In the presence of increased MT stability, centrosomes and spindle poles cluster and coalesce more efficiently, giving rise to bipolar spindles.