Drosophila neural stem cells show a unique dynamic pattern of gene expression that is influenced by environmental factors

With the aim of developing a sensor for chromosome loss in vivo , we used the well-established GAL4/GAL80 system combined with a visual GFP marker in Drosophila . We show a low frequency of green cells in most Drosophila tissues, suggesting low aneuploidy levels. Unexpectedly, in the brain, GFP positive cells are more frequent, but in this case, they do not represent chromosome loss. Using genetic manipulations, RNA FISH and time-lapse microscopy, we uncovered a dynamic and reversible silencing of GAL80 that occurs in Drosophila neural stem cells. Further, we showed that this novel gene expression regulation is influenced by environmental changes such as temperature variations or food composition. These results have important implications for the Drosophila community, namely the possible interpretation of false positive cells in clonal experiments. Additionally, they also highlight a level of mosaicism and plasticity in the brain, consistent with possible epigenetic regulation of fly chromosomes, which is different from other organs and tissues. ### Competing Interest Statement The authors have declared no competing interest.