Between the ages of 2-4, the human brain has an estimated one quadrillion synapses – the electrical connections between neurons. Pruning out extraneous synapses to enable existing ones to run more efficiently is just as important as forming new cellular connections. An imbalance between synapse formation and removal has been linked to psychiatric disorders, including autism and schizophrenia. Instead of focusing on the neurons themselves, Dr. Molofsky is interested in glial cells, such as astrocytes and microglia, which are commonly thought of as the support cells of the brain. Astrocytes have been shown to play a role in synapse formation, while microglia are implicated in pruning. Glial cells are also instrumental in the brain’s immune system, and immune signals communicate with the brain through receptors located on these cells.
Molofsky is currently researching the immune signal interleukin 33 (IL-33), which is expressed in astrocytes and correlates with synapse formation. She discovered that as the brain matures, IL-33 expression goes up, thereby enabling more pruning of synapses. “Their brain is incredibly plastic, more plastic than we would think,” she says. “Understanding how these developmental mechanisms either exist in adulthood or can be coaxed into working to help the brain to remodel could potentially be beneficial for psychiatric diseases.”