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Gene chips detect differences in human and chimpanzee brains


Scientists have used gene chips to detect different patterns of gene expression in the brains of humans and chimpanzees. They did not find similar differences in gene expression for other parts of the body, including the liver and white blood cells. The findings suggest that human gene expression patterns have changed more in the brain than in the liver during recent evolution.

Faith, 16, lives at the Center for Captive Chimpanzee Care.

The results show that "large numbers of quantitative changes in gene expression can be detected between closely related mammals," the researchers write in Science. "They furthermore suggest that such changes have been particularly pronounced during recent evolution of the human brain."

Svante Pääbo, of the Max-Planck-Institute for Evolutionary Anthropology in Leipzig, Germany, and colleagues compared expression patterns in brain tissue from seven humans, four chimpanzees, and two macaques. The gene chips, or DNA microarrays, contained about 18,000 genes. The researchers say that no chimpanzees were harmed during this study; the brain tissue came from individuals who died of natural causes.

To gain perspective on their results, the researchers profiled tissue in three mouse species. They found 'substantial' gene expression differences between the mouse species, supporting the notion that "changes in gene expression levels in the brain may have been especially pronounced during recent human evolution."

Furthermore, the team analyzed proteins in human and chimpanzee brains and compared the results to two mouse species. They found that the human brain has probably experienced more evolutionary changes in gene expression at the protein level than mice.

Some researchers have said for decades that differences in gene expression—as much or more than differences at the protein level—contribute to the physical and mental differences between humans and chimpanzees, which have 98.7 percent of their DNA in common.

Comparative studies of human and chimpanzee genetics may ultimately reveal why some diseases affect chimpanzees and humans differently in frequency and severity, including AIDS, Alzheimer's, and malaria.

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Enard, W. et al. Intra- and interspecific variation in primate gene expression patterns. Science 296, 340-343 (April 12, 2002).

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