We’ve all heard of neurons—the cells that transmit messages to the brain. But Beth Stevens, a Northeastern alumna and pioneering neuroscientist, has spent much of her career studying glia, the non-neuronal cells that comprise half the brain. Most recently her research has focused on a type of glia called microglia—resident immune cells of the brain that for many years was considered to have only immunological importance. These cells essentially go into “Pac-Man” mode and eat up bacteria and debris in the injured and diseased brain.
In a breakthrough finding in 2012, Stevens discovered that microglial cells are also responsible for “pruning,” or removing, excess synaptic cells during normal brain development in mice. Now she’s focused on advancing this work and what it may reveal about the healthy brain as well as potential causes of and treatments for brain disorders.
The John D. and Catherine T. MacArthur Foundation announced in September that Stevens, an assistant professor at Harvard Medical School and member of the F. M. Kirby Neurobiology Center at Boston Children’s Hospital, was among this year’s class of 24 fellows. Each fellowship comes with a five-year, $625,000 unrestricted grant. The so-called “genius awards” are given to exceptionally creative people, across a range of fields, with a strong track record of accomplishment and great promise to advance their work.
“I’m honored to receive this award, and I’m eager to continue our work in this emerging and important field,” said Stevens, BPH’93.
I think this pruning pathway has relevance not just for one disease but for many.
— Beth Stevens, BPH’93
The brain’s wiring
Synapses are the junction points across which neurons communicate with each other via chemicals called neurotransmitters. That communication enables the brain to perform all its functions. Stevens’ work has shown that at birth, the brain has an excess of synaptic connections and that through this normal “pruning” process weaker synapses are gobbled up while the stronger synapses are ignored, thus ensuring that the most efficient “wiring” remains.
Stevens is interested in further studying how microglial cells know which synapses to prune and which to leave alone. But she also wants to know how a better understanding of this phenomenon could lead to breakthroughs in treating neurodegenerative conditions like Alzheimer’s disease. She said a hallmark of these diseases is the early loss of synaptic connections, and that her lab’s recent work suggests that the normal “pruning” that takes place early in development is somehow reactivated to drive synapse loss in the adult brain in these diseases. Impaired microglial function may also play a role in diseases such as autism and schizophrenia.
“I think this pruning pathway has relevance not just for one disease but for many,” Stevens said. She noted that learning how to protect the synapses eliminated in adults with diseases and disorders could lead to novel therapeutic treatments.
Northeastern co-ops spark passion for discovery
Stevens said she’s drawn to under-researched areas, so microglia was the perfect fit. Her passion for discovery, she said, was forged as an undergraduate at Northeastern—particularly during her co-op experiences. One memory stands out from her co-op in a microbiology lab at New England Medical Center: when the doctors would do their rounds, they would present patient information as case studies to Stevens and her other young colleagues.
“They’d come in and say, ‘Here are the patient’s symptoms.’ It was a big ‘whodunit,’” Stevens recalled. “I found that really fascinating, this idea of trying to figure out a problem.”
All three of Stevens’ co-ops were in the clinical lab setting, including an international co-op at Sahlgrenska University Hospital, in Sweden, where she worked in a hematology lab doing blood sample analysis. She said co-op ultimately helped her realize that she preferred not to work in a clinical lab and would rather pursue a career track in biomedical research to explore scientific questions with disease and translational relevance.
“All of these experiences when you’re 20 years old, it can change your life,” she said. “It opened my eyes to what was out there.”
All of these experiences when you’re 20 years old, it can change your life. It opened my eyes to what was out there.
— Beth Stevens, on the impact of co-op
Then, now, and beyond
Stevens explained that while neurons are the more commonly known brain cell, far less was known about microglia up until 10 years ago. So it’s a small wonder that after graduating from Northeastern she began studying glial cells while working as a research assistant with Douglas Fields at the National Institutes of Health, where her passion for neuroscience blossomed. That work continued while she earned her doctorate and worked as a postdoctoral fellow with Ben Barres at Stanford University, and then at Boston Children’s Hospital, where she launched her own lab in 2008.
So, what will Stevens do with her MacArthur award? “There’s still time to think about it, but that’s the fun part,” she said. Whatever she chooses, Stevens hopes it will not only support exciting projects her lab hasn’t yet had the opportunity to tackle, but also raise awareness of microglia in the scientific community and attract more people to this emerging field of study.