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 notable differences.
'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 the brain.
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.