For the first time, the scientists have mapped that a group of genes that turn-on jointly in the human brain, revealing a kind of Rosetta Stone of its molecular organization. The Researchers say that these not-seen-before patterns of co-expressed genes hold a promise for the implicating genetic mechanisms conferring risk for sickness through "guilt by association".

National Institute of Mental Health (NIMH) grantee Daniel Geschwind, M.D., Ph.D., Michael Oldham, and colleagues at the University of California Los Angeles (UCLA), have reported on their findings in the this month issue of Nature Neuroscience.

Because all cells in the brain begin with the same genes, it's the meticulous set of genes that gets turned on - or expressed - that determines the type of cell it becomes. So the set of genes that turn on together, is called a "transcriptome," holds clues to the molecular commands fundamental the brain's different cell and tissue types. Using the methods developed by Steve Horvath, Ph.D., the UCLA researchers were able to see a gene's pattern in relation to those of all other genes. They compared samples of different brain regions like cortex, cerebellum caudate and nucleus, from many deceased individuals, looking for genes that turned on and off together.

The researchers were surprised to find many telltale patterns of genes being expressed jointly that held up across various brain regions, individuals, and experimental methods. These "modules" of co-expressed genes corresponded to brain components with different functions-such as neurons and other types of brain cells.

Researchers say that many of the modules reveal the brain's "cellular building blocks". Among all other things, they can be used to obtain the genetic and functional information to a specific cell type from whole brain tissue without having to separate just these cells from intertwining thickets of circuitry. Because genes articulates in the same module likely to share similar underlying functions, these modules also provide a shortcut to discovery of the genetic underpinnings of disease through what the researchers call "the principle of guilt by association." They provide clues to the functions of previously unknown genes that are part of the module. Also, if gene expression patterns from disease-affected individuals differ from the predicted norm, it could mean that those genes or cells are implicated in disease pathways. This could advance understanding of the human brain's complexity and of the underlying events that contribute to disease processes.