Tiny gene change affects brain size, IQ
16 April 2012, 16:24
Paris - An international team of scientists said on Sunday the largest
brain study of its kind had found a gene linked to intelligence, a small
piece in the puzzle as to why some people are smarter than others.
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.
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 blueprint for life, comprises four basic chemicals called A (for
adenine), C (cytosine), T (thymine) and G (guanine), strung together in
different combinations along a double helix.
In this case, 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.
Study of brain scans
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
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 last quarter of people, with no Cs, scored another 1.3 points lower.
effect is small," said Thompson, but "would be noticeable on a [IQ]
test ... [it] may mean you get a couple more questions correct.
"It wouldn't be an enormous change. Even so, it would help our brain resist cognitive decline later in life."
It is generally accepted that genes, a good education and environmental factors combine to determine our intelligence.
people wanted to change their genetic destiny they could either
increase their exercise or improve their diet and education," said
Thompson. "Most other ways we know of improving brain function more than
outweigh this gene."
He added there were ethical safeguards and laws in place to guard against the abuse of genetic information.
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.
Small genetic changes
team found that every T in place of a C represented a 0.6% 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.
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
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.
importance of the hippocampus in disorders such as Alzheimer's disease
these could turn out to be very significant findings," said Hartley.
Williams, head of neuroscience and mental health at the Wellcome Trust,
a British charitable foundation which backs biomedical research, said
the findings paved the way for further research into "structural
changes" which occur in disorders such as dementia, autism and