Gene Linking Intelligence to Brain Structure Identified

For the first time, British scientists have linked a gene associated with the thickness of the gray matter in the brain to intelligence. These new insights may help scientists better determine the biologic processes behind some forms of intellectual disability.

The study’s findings were published February 11, 2014, in the journal Molecular Psychiatry. The researchers, from King’s College London (UK) examined the cerebral cortex. Earlier research had shown that cortical thickness closely correlates with intellectual ability; however, at the time no genes had been identified.

An international team of scientists, led by King’s College London, analyzed DNA samples and MRI scans from 1,583 healthy 14 year old teenagers, part of the IMAGEN cohort. The teenagers also underwent a series of tests to determine their verbal and non-verbal intelligence.

Dr. Sylvane Desrivières, from the MRC (Medical Research Council) Social, Genetic, and Developmental Psychiatry Center at King’s College London’s Institute of Psychiatry, and lead author of the study, said, “We wanted to find out how structural differences in the brain relate to differences in intellectual ability. The genetic variation we identified is linked to synaptic plasticity—how neurons communicate. This may help us understand what happens at a neuronal level in certain forms of intellectual impairments, where the ability of the neurons to communicate effectively is somehow compromised. It’s important to point out that intelligence is influenced by many genetic and environmental factors. The gene we identified only explains a tiny proportion of the differences in intellectual ability, so it’s by no means a ‘gene for intelligence.’”

The researchers searched over 54,000 genetic variants that may be involved in brain development. They discovered that, on average, teenagers carrying a specific gene variant had a thinner cortex in the left cerebral hemisphere, in particular, in the frontal and temporal lobes, and performed less well on tests for intellectual ability. The genetic variation affects the expression of the NPTN gene, which encodes a protein that acts at the neuronal synapses and therefore affects how brain cells communicate.

The researchers, to validate their findings, studied the NPTN gene in mouse and human brain cells. The researchers found that the NPTN gene had a different activity in the left and right hemispheres of the brain, which may cause the left hemisphere to be more sensitive to the effects of NPTN mutations. Their findings suggest that some differences in intellectual abilities can result from the decreased function of the NPTN gene in particular regions of the left-brain hemisphere.

The genetic variation identified in this study only accounts for an estimated 0.5% of the total variation in intelligence. However, the findings may have important implications for the understanding of biologic processes underlying several psychiatric disorders, such as schizophrenia, autism, where impaired cognitive ability is a key characteristic of the disorder.

IMAGEN is a major European Commission (EU)-funded project on teenager risk taking and reinforcement-related behaviors. The project involves 2,000 14-year-old children and research teams from Ireland, England, France, and Germany. The project’s goal is to identify and learn more about biologic and environmental factors that might have an influence on normal brain function and mental health in teenagers. This data, according to the researchers, should in the future then help develop better prevention strategies and therapies.

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