Scientists once thought the brain’s glial cells just mopped up after nerve cells, keeping the environment just right so nerve cells could function at their best.

Now we’re learning that glial cells have an ongoing conversation with nerve cells: one that affects how nerve cells signal each other. When glial cells go bad, the results can be devastating brain disorders.

My students and I are investigating how glial cells change the activity of nerve cells, or neurons.

In our experiments we use fruit flies, because their nervous systems have much in common with our own and we can easily manipulate their genetic make-up.

My graduate student Sarah MacNamee genetically engineered motor neurons of larval flies to react to pulses of light. When she flashes light at the motor neurons, they fire and the animal moves. Interestingly, glial cells also react. However, when MacNamee decreases a protein in the glial cells that helps control a molecule the neurons use to communicate with each other, larvae can’t crawl properly.

Clearly glial cells have a two-way conversation with neurons that’s critical to proper brain function.

Nearly all brain tumors are glial tumors, and many brain disorders, such as Alzheimer’s disease and some mental illnesses, may involve dysfunctional glial cells.

We anticipate that figuring out how glial cells regulate neuronal activity in normal brains will help us understand these devastating brain disorders.