HMGA2 New Gene Candidate for Higher IQ

More 16 April 2012: 3 related studies in Nature Genetics

Joshua C Bis et al. Common variants at 12q14 and 12q24 are associated with hippocampal volume. Nature Genetics, 2012; DOI: 10.1038/ng.2237

M Arfan Ikram et al. Common variants at 6q22 and 17q21 are associated with intracranial volume. Nature Genetics, 2012; DOI: 10.1038/ng.2245

Jason L Stein et al. Identification of common variants associated with human hippocampal and intracranial volumes. Nature Genetics, 2012; DOI: 10.1038/ng.2250

_Source: Sciencedaily

An international team of scientists, including reasearchers from the US and the UK, have discovered a gene that is linked to both larger brain size and higher IQ.

A variant of this gene "can tilt the scales in favour of a higher intelligence", study leader Paul Thompson told AFP, stressing though that genetic blessings were not the only factor in brainpower.

Searching for a genetic explanation for brain disease, the scientists stumbled upon a minute variant in a gene called HMGA2 among people who had larger brains and scored higher on standardised IQ tests.

Thompson dubbed it "an intelligence gene" and said it was likely that many more such genes were yet to be discovered.

The variant occurs on HMGA2 where there is just a single change in the permutation of the four "letters" of the genetic code.

... the researchers found that people with a double "C" and no "T" in a specific section of the HMGA2 gene had bigger brains on average.

"It is a strange result, you wouldn't think that something as simple as one small change in the genetic code could explain differences in intelligence worldwide," said Thompson, a neurologist at the University of California at Los Angeles.

The discovery came in a study of brain scans and DNA samples from more than 20,000 people from North America, Europe and Australia, of European ancestry.

People who received two Cs from their parents, a quarter of the population, scored on average 1.3 points higher than the next group -- half of the population with only one C in this section of the gene.

The last quarter of people, with no Cs, scored another 1.3 points lower. "The effect is small," said Thompson, but "would be noticeable on a (IQ) test ... (it) may mean you get a couple more questions correct.

The research, published in Nature Genetics, was conducted by more than 200 scientists from 100 institutions worldwide, working together on a project called Enigma.

Thompson said other studies have implicated some genes in IQ, but this was the first to link a common gene to brain size.

The team found that every T in place of a C represented a 0.6 percent smaller brain -- equal to more than a year's worth of brain loss through the normal ageing process.

Asked to comment on the research, Tom Hartley, a psychologist at Britain's University of York said he was "a little wary of thinking in terms of a gene for intelligence.

"There are undoubtedly a lot of things that have to work properly in order to get a good score on an IQ test, if any of these go wrong the score will be worse." But he said it was "fascinating" to find that such small genetic changes could affect the size of critical structures such as the hippocampus, the brain's memory centre.

"Given the importance of the hippocampus in disorders such as Alzheimer's disease these could turn out to be very significant findings," said Hartley._AFP

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In other IQ news, high IQ has been linked to high levels of worry.

No one expects human intelligence to be controlled by only one, or just a few, genes. But the anatomy of the brain as well as the physiological processes in the brain that underlie intelligence, are all at least partially determined and controlled by genetic factors. The wealth of discoveries over the past half century, which tie differences in genes to differences in intelligence, are likely to grow richer as the tools of exploration and discovery become more powerful and specific.