However, given the preponderance of glia in the brain's cellular make-up, the NYU researchers hypothesized that they could play a fundamental part in brain development. To explore this, they examined the visual system of the fruit fly. The species serves as a powerful model organism for this line of study because its visual system, like the one in humans, holds repeated mini-circuits that detect and process light over the entire visual field. This dynamic is of particular interest to scientists because, as the brain develops, it must coordinate the increase of neurons in the retina with other neurons in distant regions of the brain. In their study, the NYU researchers found that the coordination of nerve-cell development is achieved through a population of glia, which relay cues from the retina to the brain to make cells in the brain become nerve cells.

"By acting as a signaling intermediary, glia exert precise control over not only when and where a neuron is born, but also the type of neuron it will develop into," notes NYU Biology Professor Claude Desplan, the paper's senior author.

For a time-lapse movie of a fruit fly visual system developing over the course of six hours, please click here: http://bit.ly/2wzUA6Q. Caption: A population of glia (bright green above magenta region) from the retina grow and infiltrate into the lamina region of the optic lobe (magenta), where they induce naïve cells to differentiate into neurons. In this way, glia coordinate neuronal development in the retina with that of the brain. Courtesy of Vilaiwan M. Fernandes, Desplan Lab, NYU's Department of Biology.

The research was supported, in part, by a grant from the National Institutes of Health (EY13012).