During mitosis, the cell nucleus and cytoplasm undergo complex reorganizations. These are triggered in part by Aurora kinase B, which is regulated by the inner centromere protein (Incenp). Both proteins are components of the chromosomal passenger protein complex, which is required for several key mitotic functions, including spindle assembly and cytokinesis. The complex has been studied in detail in vitro but much less in developing organisms in vivo. On , Mar Carmena and colleagues report that Incenp is required for cytokinesis and asymmetric cell division during the development of the Drosophila nervous system. The authors have isolated a null allele of Drosophila Incenp, which is lethal at embryonic stage 13. In embryos homozygous for this allele, histone phosphorylation and cytokinesis are defective in the developing nervous system, which indicates depletion of Aurora kinase B activity. In addition, localization of the cell-fate determinant Prospero is abnormal during asymmetric neuroblast division in these embryos. Thus, as well as regulating mitosis in symmetrically dividing cells, the chromosomal passenger complex also influences the more elaborate process of asymmetric cell division during development.
