Drosophila Nek2 protein kinase knockdown leads to centrosome maturation defects while overexpression causes centrosome fragmentation and cytokinesis failure

The Nima-related kinase 2 (Nek2) has been implicated in the regulation of centrosome integrity and separation in several species and is a candidate for cell transformation. We now show that reduction of levels of the Drosophila Nek2 by RNAi in cultured cells leads to both dispersal of centrosomal antigens and formation of ectopic bodies of centrosomal antigens. Overexpression of the active DmNek2 kinase resulted in an increase in the number of mitotic cells with fragmented centrosomes. The DmNek2 protein kinase is associated with punctuate bodies within the centrosome consistent with its presence on centrioles. In addition, it is present at lower levels on the midbody during cytokinesis. Midbody association was enhanced following overexpression, whereupon the DmNek2 protein kinase also localised to the cell cortex becoming concentrated in the region of the cleavage furrow in late telophase. Many of such cells showed abnormalities in the organisation of anillin and actin in the cleavage furrow that was associated with formation of ectopic membrane protrusions between each daughter cell. We discuss potential roles for DmNek2 in maintaining centrosome integrity in mitosis, during cytokinesis, and consequently for the fidelity of chromosome segregation. (C) 2004 Elsevier Inc. All rights reserved.