Although two broad cell-types, neurons and glia, compose the brain, neurobiologists have tended to focus on neurons- the electrically excitable cells that process information. Glia have long been the “neglected stepchildren of the nervous system”, thought of primarily as neuronal support cells. Recent studies challenge this view by showing that glia play vital roles not only in supporting neuronal function but also in instructing their development. We focus on understanding how glia regulate two key aspects of brain development: neuronal production and neuronal diversity.
Glia-like cells are present in the most evolutionarily ancient bilateria, and share common features and functions across divergent species. Genetic model systems help drive the discovery of conserved general principles that govern how these cells interact with neural progenitors and neurons. For these reasons, our experimental model of choice is the visual system of Drosophila, an excellent paradigm for nervous system development and function. Its advantages include an extensive ‘parts catalogue’- ~100 neuronal and ~25 glial subtypes are known by anatomy, and they resemble their vertebrate counterparts in many respects, as well as sophisticated genetic tools to manipulate individual cell-types with unparalleled spatio-temporal precision.
To build a brain, precursors must divide, know when to stop dividing, adopt distinct fates and then connect with appropriate partners. Often these are co-ordinated across distant neural fields to generate neural circuits. Glia regulate neurogenesis at multiple levels. They can regulate neural stem cell proliferation by providing supportive niche signals, or act as neural stem cells themselves. Glia can also induce neuronal differentiation, which we have shown is a strategy for synchronising development across the brain. In addition to cataloguing the full repertoire of glial functions, it is also necessary to understand how they do so mechanistically. Our recent work and preliminary data show that glia adopt multiple strategies not only to induce neuronal differentiation, but also to specify individual neuronal types. The lab employs sophisticated genetic, molecular and imaging techniques to decipher how glia induce neuronal diversity, how they may generate neurons themselves, as well as to identify new roles for glia during development.