Regenerative neurogenic response from glia requires insulin driven neuron-glia communication

Abstract

Some animals can regenerate their central nervous system (CNS) after injury by inducing de novo neurogenesis: discovering the underlying mechanisms would help promote regeneration in the damaged human CNS. Glial cells could be the source of regenerative neurogenesis, but this is debated. The glia transmembrane protein Neuron-Glia antigen-2 (NG2) may have a key role in sensing injury-induced neuronal signals, however these have not been identified. Here, we used Drosophila genetics to search for functional neuronal partners of the NG2 homologue kon-tiki (kon), and identified Islet Antigen-2 (Ia-2), required in neurons for insulin secretion. Alterations in Ia-2 function induced neural stem cell fate, injury increased ia-2 expression and induced ectopic neural stem cells. Using genetic epistasis analysis and lineage tracing, we demonstrate that Ia-2 functions with Kon to regulate Drosophila insulin-like peptide 6 (Dilp-6) which in turn generates both more glial cells and neural stem cells from glia. Ectopic neural stem cells can divide, and limited de novo neurogenesis could be traced back to glial cells. Altogether, Ia-2 and Dilp-6 drive a neuron-glia relay that restores glia, and reprograms glia into neural stem cells for CNS regeneration.