Illuminati, a novel form of gene expression plasticity in Drosophila neural stem cells
With the aim of developing a genetic instability (GI) sensor in vivo we used the well-established Gal80/Gal4-UAS system combined with a visual GFP marker in Drosophila. We generated a collection of 25 Drosophila lines carrying GAL80 transgenes in different locations in all major chromosomes (X, Y, II, and III). We found low rates of GFP cells in epithelial tissues such as wing discs. In contrast, in larval brains, GFP positive clusters containing neural stem cells- also called neuroblasts (NBs)- and their offspring, were highly frequent. Using genetic and imaging-based approaches, we show that GFP NBs do not result from aneuploidy or mutations in the GAL80 gene, but rather by stochastic repression of GAL80 expression. We named this novel type of gene expression instability Illuminati. Importantly, Illuminati frequency is influenced by environmental and stress conditions. Further, we found that once established, Illuminati can be propagated over many cell cycles.