The first detailed maps of genetic
activity in the human brain have been published online by scientists. This freely
accessible resource shows that the expression of genes across adult human
brains is largely similar from one individual to the next, with only a few
'This study demonstrates the
value of a global analysis of gene expression throughout the entire brain and
has implications for understanding brain function, development, evolution and
disease', said Dr Ed Lein, who was involved in the study carried out at the
Allen Institute for Brain Science, Seattle.
Comprehensive maps of the genetic
activity of mouse brains have been available for a few years and proven useful
to researchers using mice as their model organism for investigation. However
the human brain, being a thousand times larger, has up until now only had rough
maps of its gene expression recorded.
'The fact that so many of the
brain-expressed genes have not been well-characterised means that there are
huge voids in our understanding of how genes relate to proper brain function',
said Dr Lein. 'This map we have created can provide functional predictions to
catalyse a wave of new research in molecular brain research'.
Researchers used functional
magnetic resonance imaging to accurately map the complete brains of two
men and half the brain of a third man. Each brain half was then divided into
400 to 500 distinct regions that were analysed using microarrays to detect
levels of messenger RNA - a read-out of gene expression.
Results showed there was little
variation in gene activity between the different brains. In addition, the outer layer of each brain (cortex),
which controls a large variety of functions including thought, memory and vision,
showed similar gene expression throughout. A comparison of the left and right
hemispheres also showed only slight differences, despite certain
functions such as language being predominantly processed by just one side of
Although differences in genetic
activity were in the minority, the small differences in gene
expression that did occur were enough for scientists to accurately pinpoint
which brain region a nerve cell belonged to. Previously uncharacterised genes
were also mapped and found to express in distinct brain regions, shedding light
on their particular roles within the brain.
The study continues to add more
data to the online resource, with the aim of uncovering the genetic differences
between healthy and diseased brains, in the hope that this will help research
into medical treatments.
'These results only scratch the surface
of what can be learned from this immense data set. We look forward to seeing
what others will discover', says Dr Lein.
The study was published in Nature.