Abstract
The developmental control of neuroblast proliferation is absolutely required for the assembly and function of the central nervous system. A lethal mutation in trol results in the failure of quiescent neuroblasts to begin division at the appropriate time. I have established a culture system in which quiescent neuroblasts in explants of Drosophila larval CNSs initiate cell division in vitro to normal in vivo levels. This activation requires removal of the CNS for culture after a specific developmental stage and the presence of fetal calf serum or a larval extract in the medium. Either supplement is effective when heat-treated. Substitution of the steroid hormone ecdysone or the non-steroidal ecdysone analog RH5992 for either fetal calf serum or larval extract also results in activation of neuroblast proliferation. Culture of trolsd CNSs with wildtype larval extract or ecdysone results in the defective neuroblast proliferation phenotype observed in trol mutants in vivo, while culture of wildtype CNSs with trolsd extract produces normal neuroblast proliferation.
