Astrocytes, star–shaped cells in the central nervous system, are essential to the survival and healthy function of brain neurons. But aberrant astrocytes may be driving neurodegenerative disorders.

While most of us haven’t heard of astrocytes, these cells are four times as plentiful in the human brain as nerve cells. Now, a team led by researchers at the Stanford University School of Medicine has found that astrocytes, which perform many indispensable functions in the brain, can take on a villainous character, destroying nerve cells and likely driving many neurodegenerative diseases.

A study describing the findings was published online Jan. 18 in the journal Nature.

“We’ve learned astrocytes aren’t always the good guys,” said the study’s senior author, Ben Barres, MD, PhD, professor of neurobiology, of developmental biology and of neurology and neurological sciences. “An aberrant version of them turns up in suspicious abundance in all the wrong places in brain–tissue samples from patients with brain injuries and major neurological disorders from Alzheimer’s and Parkinson’s to multiple sclerosis. The implications for treating these diseases are profound.”

Barres, who has spent three decades focusing on brain cells that aren’t nerve cells, called the findings “the most important discovery my lab has ever made.” Stanford postdoctoral scholar Shane Liddelow, PhD, is the study’s lead author.