The human brain has about 90 billion neurons, interconnected through junctions called synapses. Our brains form synapses to organize new knowledge and memories; malfunctioning synapses, on the other hand, are linked to such disorders as mental retardation and Alzheimer disease.
Yale scientists reported in the journal Neuron in December that a molecule called synaptic cell adhesion molecule 1 (SynCAM 1) is essential for both synapse formation and maintenance. When the SynCAM 1 gene was activated in mice, more synaptic connections were formed. Mice without the molecule produced fewer synapses. So far, so good.
The team’s next finding, however, was not so clear-cut. Mice with high levels of SynCAM 1 failed at spatial learning, while mice lacking SynCAM 1 learned better. Too much of a good thing?
“It appears that SynCAM 1 ties synapses together; some of this molecule is needed to promote contact, but too much glues down the synapse and inhibits its function,” said senior author Thomas Biederer, Ph.D., associate professor of molecular biophysics and biochemistry.