The Hindu
Map reveals the activity of genes across the entire brain to help shed light on neurological and psychiatric conditions
A comprehensive atlas of the adult human brain that
reveals the activity of genes across the entire organ has been created
by scientists.
The map was created from genetic
analyses of about 900 specific parts of two “clinically unremarkable”
brains donated by a 24-year-old and 39-year-old man, and half a brain
from a third man.
Baseline
Researchers at
the Allen Institute for Brain Science in Seattle said the atlas would
serve as a baseline against which they and others can compare the
genetic activity of diseased brains, and so shed light on factors that
underlie neurological and psychiatric conditions.
“The human brain is the most complex structure known to mankind and one
of the greatest challenges in modern biology is to understand how it is
built and organised,” said Seth Grant, a professor of molecular
neuroscience at Edinburgh University who worked on the map. “This allows
us for the first time to overlay the human genome on to the human
brain. It gives us essentially the Rosetta stone for understanding the
link between the genome and the brain, and gives us a path forward to
decoding how genetic disorders impact and produce brain disease.” The
power of the brain arises from its neural wiring, its variety of cells
and structures, and ultimately where and when different genes are
switched on and off throughout the 1.9kg lump of tissue.
Detailed analysis
From more than 100 million measurements on brain pieces, some only a
few cubic millimetres, the scientists found 84% of all genes are turned
on in some part of the organ. Gene activity in next door regions of the
cortex, the large wrinkly surface of the brain, was similar but distinct
from that in lower parts, such as the brain stem.
More detailed analysis of the cortex revealed patterns in gene activity
that corresponded to regions with specific roles in the brain, such as
movement and sensory functions. The atlas revealed no major divide in
gene activity on the left and right sides of the brain, suggesting that
expertise generally handled by one hemisphere, such as language, comes
from more subtle differences than the study could spot.
Although
the brains came from men of similar age and ethnicity, the pattern of
gene activity was so similar that researchers suspect there may be a
common blueprint.
Greater challenge
Scientists
have constructed similar genetic atlases for rodents in the past, but
the shortage of donated human brains, their size and the destructive
nature of the tests meant a human equivalent was more of a challenge.
Writing in the journal Nature,
the scientists describe how they scanned the donated brains and then
chopped them into tiny pieces. For each piece, they measured activity
levels for all of the 20,000 or so genes in the human genome.
The atlas, which overlays the genetic results on to a 3D image of the brain, is freely available for researchers to use online.
Grant said that future studies would look to connect the genetic brain
atlas with other genetic studies or brain scans of abnormal or diseased
brains. That could highlight genes that play a role in brain conditions
and point the way to drug treatments.
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