Trophic neuron-glia interactions and cell number adjustments in the fruit fly

Trophic interactions between neurons and enwrapping glia, and between neurons and target cells, provide plasticity to the mammalian nervous system. Here, we review evidence that analogous cell interactions operate in the development of the nervous system of the fruit-fly Drosophila. Homologues of the canonical mammalian trophic factors also maintain neuronal and glial survival in Drosophila, adjusting cell populations to enable appropriate function, and revealing commonalities in nervous system development across the animals. There are also differences between neuron-glia interactions in flies and humans, not surprisingly, because we are only related to flies through a remote common ancestor. Nevertheless, the shared cellular and molecular mechanisms underlying developmental plasticity and enwrapping glial functions, strengthen the opportunity to use Drosophila to understand the brain, to model brain diseases and to understand the involvement of glial cells in nervous system regeneration.