The connection between nervous and immune system in Drosophila melanogaster
Angela Giangrande IGBMC, Strasbourg, France
Drosophila glia originate from neural stem cells and strictly depend on the expression of a single transcription factor that makes the choice between the glial and the neuronal fates, Glide/Gcm. Glia ensure normal development of the nervous system, including the regulation of stem cell proliferation. They are also required for the function of the nervous system and act as immune cells in a broad range of pathological conditions, such as brain injury and degeneration. The Drosophila glia therefore display the combined features of the vertebrate micro- and macroglia, mesoderm-derived immune cells that invade the CNS during development and neuroectodermally derived cells, respectively. Microglia represent the professional scavenger cells of the nervous system, macroglia insulate/protect the axons and control the proliferative state of the CNS. Thus, the complex nervous system of vertebrates requires more cell types, calling for a division of labor occurring during evolution. Interestingly, the Drosophila Glide/Gcm transcription factor is also expressed and required in the immune cells of the fly called hemocytes. These are cells that patrol the organism and control the immune response outside the nervous system. Glide/Gcm inhibits the inflammatory response in these cells. This suggests that Glide/Gcm may have a function in immunity in vertebrates. Recent data support this hypothesis.