Controlled microfluidics to examine growth-factor induced migration of neural progenitors in the Drosophila visual system.

BACKGROUND The developing visual system in Drosophila melanogaster provides an excellent model with which to examine the effects of changing microenvironments on neural cell migration via microfluidics, because the combined experimental system enables direct genetic manipulation, in vivo observation, and in vitro imaging of cells, post-embryo. Exogenous signaling from ligands such as fibroblast growth factor (FGF) is well-known to control glia differentiation, cell migration, and axonal wrapping central to vision. NEW METHOD The current study employs a microfluidic device to examine how controlled concentration gradient fields of FGF are able to regulate the migration of vision-critical glia cells with and without cellular contact with neuronal progenitors. RESULTS Our findings quantitatively illustrate a concentration-gradient dependent chemotaxis toward FGF, and further demonstrate that glia require collective and coordinated neuronal locomotion to achieve directionality, sustain motility, and propagate long cell distances in the visual system. COMPARISON WITH EXISTING METHOD(S) Conventional assays are unable to examine concentration- and gradient-dependent migration. Our data illustrate quantitative correlations between ligand concentration/gradient and glial cell distance traveled, independent or in contact with neurons. CONCLUSIONS Microfluidic systems in combination with a genetically-amenable experimental system empowers researchers to dissect the signaling pathways that underlie cellular migration during nervous system development. Our findings illustrate the need for coordinated neuron-glia migration in the Drosophila visual system, as only glia within heterogeneous populations exhibited increasing motility along distances that increased with increasing FGF concentration. Such coordinated migration and chemotactic dependence can be manipulated for potential therapeutic avenues for NS repair and/or disease treatment.