Neuronal diversity in Drosophila is generated by the temporal specification of type II neuroblasts (NBs) and their progeny, the intermediate neural progenitors (INPs). Multiple transcription factors are expressed in a birth order-dependent manner within each INP lineage, but whether this temporal patterning gives rise to discrete neuronal sets from each individual INP cell is unclear. Now, on , Tzumin Lee and colleagues describe extensive fate-mapping of individual neurons derived from specific type II NB lineages. The authors use targeted clonal labelling to specifically label neurons in individual INP clones, and by restricting the clonal induction to specific time windows they are able to generate and characterise clones of neurons that are born from two successively produced INPs. The resulting analyses demonstrate that the temporal specification of INPs does indeed translate to distinct types of neurons, suggesting that neuronal fate diversification might operate as a function of age.
