Plasmodium NEK1 coordinates MTOC organisation and kinetochore attachment during rapid mitosis in male gamete formation

Mitosis is an important process in the cell cycle required for cells to divide and proliferate. Never in mitosis (NIMA)-like kinases (NEKs) are regulators of many functions during mitosis. Plasmodium, the causative agent of malaria is a divergent unicellular haploid eukaryote with some unusual features in terms of the cell cycle, mitosis and nuclear division during its life cycle, presumably to facilitate proliferation in varied environments. For example, during sexual stage during male gametogenesis, within the mosquito host, an atypical rapid closed endomitos is observed. Here three rounds of genome replication from 1N to 8N and successive cycles of multiple spindle formation and chromosome segregation within eight minutes takes place followed by karyokinesis to generate haploid gametes.Our previous Plasmodium kinome screen identified four Nek genes, of which two, NEK2 and NEK4, are required for meiosis. NEK1 is likely essential for mitosis in asexual blood stage schizogony in the vertebrate host, but its function during atypical cell division during male gametogenesis is unknown. Here we study NEK1 location and function, using live cell imaging, ultrastructure expansion microscopy (U-ExM) and electron microscopy, together with conditional gene knockdown and proteomic approaches. We report spatiotemporal NEK1 location in real-time, coordinated with microtubule organising centre (MTOC) dynamics during the unusual mitosis at various stages of the Plasmodium life cycle. Knockdown studies reveal NEK1 to be an essential component of the MTOC in male cell differentiation, associated with rapid mitosis, spindle formation and kinetochore attachment. These data suggest that Plasmodium NEK1 kinase is an important component of MTOC organisation and chromosome segregation during male gamete formation.