Cyclin E acts under the control of hox-genes as a cell fate determinant in the developing central nervous system

The mechanisms controlling the generation of cell diversity in the central nervous system belong to the major unsolved problems in developmental biology. The fly Drosophila melanogaster is a suitable model system to examine these mechanisms at the level of individually identifiable cells. Recently, we have provided evidence that CyclinE - largely independent of its role in cell proliferation - plays a critical role in the specification of neural stem cells ( neuroblasts). CycE specifies neuronal fate within neuroblast lineages by acting upstream of glial factors ( prospero and glial cell missing), whereby levels of CycE are controlled by homeotic genes, the master control genes regulating segment specific development. Considering the general relevance of CycE and homeotic genes in developing organisms, it seems likely that this mechanism has been conserved among species to contribute to regional diversification in the CNS.