Quiescent neural stem cells transiently become neuronal-like to coordinate long-range reactivation

Reactivation of quiescent neural stem cells (qNSCs) is a coordinated process that generates new neurons and glia to maintain homeostasis or enable repair post-injury. Here, we discovered that NSC reactivation in Drosophila follows a hierarchical sequence, whereby anterior qNSCs in the brain lobes control the timely reactivation of more posterior qNSCs in the ventral nerve cord. To achieve this, qNSCs transiently activate neuronal genes and contact neurons to relay reactivation. This transient neuronal state is specific to qNSCs, as neuronal genes are switched off after stem cells resume proliferation. Our results reveal long-range communication between qNSCs to coordinate reactivation across the entire CNS, enabled by a transient, remarkably plastic, neuronal state that allows direct interaction with axons. Overall design: Aim of the experiment is to identify differentially expressed genes between quiescent and reactivated NSCs, The CNS from stage 17 embryos (representing quiescence) and from larval 24 ALH (representing reactivated) were isolated, dissociated and NSCs were enriched by FACS.