Home Uncategorized Scientists identify the gene that makes our brains bigger

Scientists identify the gene that makes our brains bigger

Mouse embryos have developed massive, fast-growing brains after
receiving a dose of human DNA in the womb. Scientists suspect that the
gene encoded by this DNA is what separates us from all other animals. 

would be nothing without our remarkable brains. Despite sharing 98
percent of our DNA with chimpanzees, we’ve got much bigger brains, and
they undergo a massive white matter growth explosion in the first two years of life,
which means a super-fast proliferation of neural connections.
Researchers have pinned this to why we’re so much more intelligent than
our primate brethren, but it’s not actually clear where in our genetic
make-up the instructions to make all this occur. 
To investigate, researchers at Duke University in the US picked over and compared areas of human and chimp DNA, focussing on ‘enhancer’ sequences,
which are short bits of DNA that regulate the activity and expression
of neighbouring genes. Several thousand enhancers are found in every
genome, but in previous research, no one had found any that were
specific to humans and linked directly to brain growth. 
In their
initial screening, the team identified 106 enhancers that could be
related to the difference in chimp and human brain growth. A closer
analysis revealed that six of these sequences were located near genes
thought to be involved in brain development. The group called them
‘human-accelerated regulatory enhancers,’ or HARE, and numbered them one
through six. 
HARE5, in particular, was looking particularly
special. When they inserted the sequence into mouse embryos, the mice
grew brains that were 12 percent bigger than those of mouse embryos that
received HARE5 sequences from chimpanzees. Which is pretty surprising,
seeing as these enhancers only differ between chimps and humans by 16
letters in their genetic code.
While the difference in brain
growth between the two groups of mouse embryos was initially very
subtle, near the end of gestation, the burgeoning size of the brains
enhanced by human DNA was noticeable to the naked eye. 
Debra Silver, the lead study author and an assistant professor of molecular genetics and microbiology at Duke, explained the results to Rachel Feltman at The Washington Post: 

discovered that the human DNA sequence, which only had 16 changes in it
compared to the chimp sequence, was being expressed differently in
mice. The human DNA was really able to accelerate the way the stem cells
divide, and as a result, the mice were able to produce more neurons.
HARE5 seems to promote the ability to create more neurons and increase
brain size, which allows human brain development to take advantage of

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Interestingly, the team reports in Current Biology
that the region that was most affected by this hyper-growth in the
mouse brains was the cerebral cortex, which is thought to be involved in
language and reasoning skills.
“We’re seeing differences in brain development, particularly in the structure of the brain that becomes the cerebral cortex,” Silver told The Washington Post. “The
cerebral cortex has an important function in decision making and
thought in humans. We’re definitely interested in testing whether it
might affect memory or socialisation in mice.”
The question of how
we got to be as intelligent as we are remains open, but we now have a
fascinating little piece of DNA with which to investigate. And a
potential army of malevolent rodent geniuses:


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