Developing brain cells called microglia prune the connections between neurons, shaping how the brain is wired, scientists at the European Molecular Biology Laboratory (EMBL) in Monterotondo, Italy, have discovered.
"We're very excited, because our data shows microglia are critical to get the connectivity right in the brain," said Cornelius Gross, who led the work: "they 'eat up' synapses to make space for the most effective contacts between neurons to grow strong."
Microglia are related to the white blood cells that engulf pathogens and cellular debris. Looking at the developing mouse brain under the microscope, Gross and colleagues found proteins from synapses - the connections between neurons - inside microglia, indicating that microglia are able to engulf synapses too.
To probe further, the scientists introduced a mutation that reduced the number of microglia in the developing mouse brain.
"What we saw was similar to what others have seen in at least some cases of autism in humans: many more connections between neurons," Gross said.
"So we should be aware that changes in how microglia work might be a major factor in neurodevelopmental disorders that have altered brain wiring," added Gross.