Brain complexity: microglia prune synapses (Introduction)

by David Turell , Wednesday, October 28, 2015, 23:30 (3314 days ago) @ David Turell

Microglia are the immune cells of the brain, but they have many other functions:-http://www.scientificamerican.com/article/rise-of-the-microglia/?WT.mc_id=SA_WR_20151028-"The discovery that microglia were active in the healthy brain jump-started the exploration into their underlying mechanisms: Why do these cells hang around synapses? And what are they doing?-"For reasons scientists don't yet understand, the brain begins with more synapses than it needs. “As the brain is making its [connections], it's also eliminating them,” says Cornelius Gross, a neuroscientist at the European Molecular Biology Laboratory. Microglia are critical to this process, called pruning: they gobble up synapses, thus helping to sculpt the brain by eliminating unwanted connections.* But how do microglia know which synapses to get rid of and which to leave alone?-"New evidence suggests that a protective tag that keeps healthy cells from being eaten by the body's immune system may also shield against microglial activity in the brain. Emily Lehrman, a doctoral candidate in neuroscientist Beth Stevens's laboratory at Boston's Children's Hospital, presented these unpublished findings at this year's SfN. “The [protective tag]'s receptor is highly expressed in microglia during peak pruning,” Lehrman says. Without an abundance of this receptor, the tag is unable to protect the cells, leading to excess engulfment by microglia and overpruning of neuronal connections.* -"But pruning is not always a bad thing. Other molecules work to ensure that microglia remove weak connections, which can be detrimental to brain function. Cornelius Gross, a neuroscientist at the European Molecular Biology Laboratory, and his research group have been investigating the activity of fractalkine, a key molecule in neuron-microglia signaling whose receptors are found exclusively on microglia. “Microglia mature in a way that matches synaptogenesis, which sets up the hypothesis that neurons are calling out to microglia during this period,” Gross says."-Comment: Show me a computer that cannibalizes itself? Again high complexity beyond the abilities of random evolution.