MacArthur Genius Grant Winner Probes the Pruning Brain

Harvard neuroscientist Beth Stevens wins a MacArthur Fellowship for studies of how microglia cells prune away excess neuronal synapses during brain development and how that necessary function might go awry in neurodegenerative diseases.

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“They’re like the Pac-Man of our brain.”

, talking about , which make up more than half . This week Stevens got a MacArthur Fellowship, the so-called genius grant, for her studies of glia. 

“These cells are incredibly responsive to damage or injury. They can protect our brain by, for example, clearing bacteria or debris in the brain in the case of injury and disease…

“Until about 10 years ago, almost all of the research devoted to these cells was in these contexts. We discovered that there was another role for these cells in the normal healthy brain, in particular during development…

“So a synapse is the junction of communication between two neurons, it’s how neurons talk to each other…we’re actually born with an excess of synaptic connections…and through this normal developmental process called pruning, a large number of these extra synapses get permanently removed or eliminated while others get strengthened and maintained. These microglial cells were in fact engulfing or eating these extra synapses. So these cells are necessary to do this and now of course we’re trying to better understand how it is that they know which synapse to prune and which synapse to leave alone.

“A hallmark of many neurodegenerative diseases, including Alzheimer’s disease, is the early loss of synaptic connections or synapses…And what’s most striking about this is, it’s thought that the synapse loss happens years before you see signs of cognitive impairment or pathology.

“That means it’s critical that we understand how these synapses are lost—what makes synapses vulnerable. And that’s a major question my lab is addressing. So recent work in the lab suggests that these normal pruning mechanisms that I’ve just described that are relevant to development get reactivated to drive or mediate this early synapse loss in the adult brain in these diseases. This is very exciting because it allows us to think about the potential that intervening with this pruning pathway could lead to new insight into therapeutics.”

For the complete list of this year’s 24 MacArthur Fellows, including about 10 science and medicine people depending on how you define their activities, go to , for MacArthur Foundation.

—Steve Mirsky

Stevens audio via MacArthur Foundation