Mechanisms of asymmetric cell division during animal development.

Recent years have seen the discovery of machineries for asymmetric cell division in a number of different organisms. The Inscuteable protein is a central component of such a machinery in Drosophila. Within dividing Drosophila neural precursor cells, Inscuteable directs both the orientation of the mitotic spindle and the asymmetric segregation of the proteins Numb, Prospero and Miranda into one of the two daughter cells. Numb can act by repressing signalling via the transmembrane receptor Notch, whereas Miranda localizes the transcription factor Prospero which initiates daughter cell specific gene expression. The identification of Numb homologs in other species has suggested that this machinery might be conserved from Drosophila to vertebrates.