Scientist Spot Brain Protein that May Cause Autism When Disrupted

Scientists have taken a closer look at synapses in the human brain and now, they may have discovered a mechanism linked to autism. They've identified a protein that, when disrupted, could lead to the development of autism.

When a child is first born, neurons in the newborn brain compete with one another to form lasting connections, called neurons. In this case, the researchers examined the brains of newborn mice with a technique known as three-dimensional electron microscopy. More specifically, the scientists focused on tiny protrusions of the neuron called spines that harbor synaptic connections.

The researchers found that initially, some of the spines received two or more inputs. As the brain matured, the spines then received one.

Yet more interesting was that the scientists found that mice that were missing a gene that coded for the protein, hevin, retained more of these multiple synapses compared with normal mice. As the developing brain pruned away synapses to become more efficient, this could become a problem.

Hevin was first identified in the miniscule space between synapses in 1990. Yet gene expression studies revealed that it's actually churned out by non-neuronal cells called astrocytes. In this latest study, the researchers found that in the cortex of the brain, hevin encourages inputs from the thalamus, a part of the brain that acts as a relay center for sensory and motor information, while it discourages inputs from local neurons within the cortex.

The researchers also discovered that the spines that receive multiple synapses tend to be occupied by both cortical and thalamic connections at the same time, suggesting that these spines are sites for synaptic competition.

What's interesting is that the balance of these two types of connections in the cortex can go awry in neurological diseases, such as autism and depression. This means that the findings could go a long way in terms of finding out ways to better treat these diseases. Currently, the researchers are studying the molecular mechanisms of hevin and its potential contribution to health and disease.

The findings are published in the journal eLife.

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