UCLA researchers discover single genetic change linked to IQ and brain size
By Aislinn Dunne
April 26, 2012 1:17 a.m.
A link between genetics and brain size has been established by a team led by neurology researchers at UCLA, working as part of an international collaborative research project, showing that single genetic changes play a role in determining brain volume and IQ.
The discovery could lead to better diagnosis and treatment of neurological diseases, experts say.
While it has been known for some time that genetics influence the structure of the brain, this study is the first to find the specific genetic variants associated with brain structure, said Jason Stein, a researcher in the Laboratory of Neuro Imaging at UCLA who led the project.
The study, which took about two years to complete, was the first project conducted through an international collaboration of scientists called Enhancing Neuro Imaging Genetics through Meta-Analysis, or ENIGMA.
“It’s a little bit like a social network,” said Paul Thompson, a professor of neurology at the UCLA David Geffen School of Medicine and one of the researchers in the study, who also described ENIGMA as “crowdsourcing.”
ENIGMA, which involves 207 scientists from more than 10 countries, invites hospitals and research institutions to electronically share their brain scans and DNA tests so that scientists have more data to work with, Stein said.
With more than 20,000 brain scans analyzed, this is the largest study of the brain in the world, Thompson said. Researchers were able to definitively link changes in brain structure to single letter changes in genes because of the large sample size of the study, Stein said.
By comparing brain scans with DNA samples, the study found that a single letter change on one human chromosome can affect both IQ and the relative age of the brain, Thompson said.
In one location on a gene in one chromosome, some people have a cytosine base while others have a thymine base, Thompson said. Individuals with a cytosine base scored, on average, slightly higher on an IQ test than those with a thymine base. Those with a cytosine base also had statistically larger brains, Thompson said.
A genetic change can also affect how old the brain appears to be in a brain scan. A single letter change in a gene can make the brain appear to be about three years older, Thompson said.
The research also has implications for the diagnosis and treatment of neurological illnesses. Once the genetics of brain disorders such as autism are understood, it may be possible to predict who will have the diseases, said Rita Cantor, a professor of human genetics at the UCLA David Geffen School of Medicine.
The study’s findings are also promising for the development of new drugs. Drug companies could test the genes of participants in clinical drug trials to pick those who are at a higher risk for a disease, allowing companies to target their drug development, Thompson said.
More research is still required, however, before the potential benefits of the ENIGMA study can materialize, Cantor said.
Future studies of ENIGMA will include examining other genetic variants and how different parts of the brain connect, Stein said.
