Research Focuses on Gut Microbes and Synaptic Pruning in the Brain
University of Oregon researchers recently published a study that is the first to demonstrate that microglia are required for pruning neural connections in zebrafish larvae. This study also showed that an intact microbiota is necessary for routine pruning and typical fish social behavior. Additionally, these authors discovered a critical developmental window during the first week of larval development, during which the microbiota stimulates microglial localization to the forebrain, where they prune neural connections. Pruning is a normal part of healthy brain development. Superfluous neural connections in the brain can get in the way of critical connections, causing congestion and obstruction that may result in muddled messages. To conduct this research, the authors found a pathway linking microbes in the gut to neurons in the brain that are required for social interaction. The team then worked with two sets of zebrafish. One group had healthy gut microbes, and the other was missing those same beneficial gut microbes. In the healthy fish set, gut microbes spurred microglia to prune back extra links between neurons. However, in the zebrafish group without those gut microbes, the pruning didn’t occur, and the fish showed social deficits. Co-author Philip Washbourne is excited about the study’s findings. He states, “We’ve known for a while that the microbiome influences a lot of things during development. But there hasn’t been a lot of concrete data about how the microbiome is influencing the brain. We’ve done quite a bit to push the boundary there.” Co-author Judith Eisen agrees and says, “This is a big step forward. It also sheds light on things that are going on in larger, furrier animals.”
