Scientists have long known that microglia are responsible for helping synapses grow and rearrange as part of a brains normal development, but Laetitia Weinhard, from the Gross group at EMBL Rome has been the first to capture the process occurring in a brain. Surprisingly, the findings in collaboration with the Schwab team at EMBL Heidelberg have found that the process makes synapses stronger, rather than weaker.
The cells are similar to macrophages, acting as the first and predominant immune defence, and form approximately one in ten of the cells that comprise your brain tissue. Scientists had hypothesized that they acted as ‘clippers’ to prone the connections between brain cells during early circuit refinement. The researchers have observed that the synapse sends out thin arm-like projections to greet the microglia after it has initiated contact.
The research paper will be published this month in Nature Communications, and explains the five years of development that culminated in combining light and electron microscopy (CLEM) with light sheet fluorescence microscopy to make the film form of them eating synapses.
“This is what neuroscientists fantasised about for years, but nobody had ever seen before,” says Cornelius Gross. “These findings allow us to propose a mechanism for the role of microglia in the remodeling and evolution of brain circuits during development.”
Image: Multiple synapse heads send out filopodia (green) converging on one microglia (red), as seen by focused ion beam scanning electron microscopy (FIBSEM) – L. Weinhard, EMBL Rome.
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