02 September 2010

20,000 Genes Under the Brain: Genes->Brain->Man

This image from a gene chip shows the activity of thousands of genes from tissue taken from a section of the hippocampus. Each spot denotes activity from a separate, single gene; the brighter the spot, the more active that gene is in the tissue sample tested.
An online interactive atlas of the human brain can show the activity of over 20,000 genes. Genes make the brain -- in conjunction with the environment. The brain makes the man. If we can observe the ongoing interplay of brain genes with environment, we will have a much clearer concept of why certain brains (men) behave the way they do.
Scientists can now determine where in the brain genes that encode specific proteins are active—including proteins that are affected by medications. Such information may help predict a drug’s benefits and side effects.

Using the atlas, researchers can zoom in on brain structures thought to be altered in mental disorders such as schizophrenia to find the molecular footprint of these diseases.
The atlas may provide molecular clues to memory, attention, motor coordination, hunger, and perhaps emotions such as happiness or anxiety.

Scientists have long sought to understand the biological basis of thought. In the second century A.D., physician and philosopher Claudius Galen held that the brain was a gland that secreted fluids to the body via the nerves—a view that went unchallenged for centuries. In the late 1800s clinical researchers tied specific brain areas to dedicated functions by correlating anatomical abnormalities in the brain after death with behavioral or cognitive impairments. French surgeon Pierre Paul Broca, for example, found that a region on the brain’s left side controls speech. In the first half of the 20th century, neurosurgeon Wilder Penfield mapped the brain’s functions by electrically stimulating different places in conscious patients during neurosurgery, triggering vivid memories, localized body sensations, or movement of an arm or toe.

In recent years new noninvasive ways of viewing the human brain in action have helped neuroscientists trace the anatomy of thought and behavior. Using functional magnetic resonance imaging, for instance, researchers can see which areas of the brain “light up” when people perform simple movements such as lifting a finger or more complex mental leaps such as recognizing someone or making a moral judgment. These images reveal not only how the brain is divided functionally but also how the different areas work together while people go about their daily activities. Some investigators are using the technology in an attempt to detect lies and even to predict what kinds of items people will buy; others are seeking to understand the brain alterations that occur in disorders such as depression, schizophrenia, autism and dementia. _SciAm

To assess gene expression in each small bit of tissue, researchers expose its RNA to a gene chip, or DNA microarray. These small devices are coated with clusters of identical DNA molecules, called probes, within separate areas. Each probe binds to the RNA of a specific gene—the one that contains a complementary set of chemical units, or bases. In a DNA molecule, the base adenine (A) sticks to thymine (T), and guanine (G) pairs with cytosine (C). Thus, the sequence that would bind to the strand illustrated above is (from top to bottom): T, C, C, T, G, C, A. In this way, a chip records which genes are active, and to what extent they are active, in the tissue sample
We will need to be able to detect brain-gene activity without chopping up the brain first, of course. Most people -- except perhaps for conscientious members of the Voluntary Human Extinction Movement, perhaps -- would balk at volunteering for a brain-gene map, if they knew their brains would have to be removed and sliced into sheets.


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