Macaque Genome Sequenced

THURSDAY, April 12 (HealthDay News) -- Researchers have sequenced the genome of the rhesus macaque, providing more precise data on how humans are genetically different from primates.

Sequencing the macaque genome not only benefits research in human health but expands the understanding of primate evolution. More than 170 scientists from 35 institutions worked on the macaque genome project, and they published their findings in several articles in the April 13 issue of Science, a special edition devoted to the discovery.

"The importance of doing the sequencing is, first, it enhances our study of evolution and what has made us different from primates," said lead researcher Richard A. Gibbs, director of the Medicine Human Genome Sequencing Center at Baylor College in Houston.

Although apes are genetically close to humans, that small percent of difference really makes all the difference, Gibbs said.

Gibbs noted that the chimpanzee genome has already been sequenced. "Like the macaque, there is a small percentage of error. The chimp is so close to the human that those errors make it very hard to see what is exactly the same and what is different from humans," he said. "The macaque is further away from humans, so it makes it a better mirror to look into."

The human genome was first sequenced in 2001. That feat was followed by the sequencing of the chimpanzee genome in 2005, allowing scientists to see which genes humans shared with chimps, from which humans diverged some 6 million years ago. The macaque is an older relative; it diverged 25 million years ago.

Macaque genes are about 97.5 percent similar to those of chimps and humans. Chimps and humans have 99 percent of the same gene sequences.

In addition, sequencing the macaque is important for biomedical research, where the macaque has been used extensively, Gibbs said.

"This will lead to more careful and thoughtful use of the macaque," he said. "For example, not much is known about the immune system of the macaque, but it is used in immunology research. With the gene sequence, we can see how they are different from humans."

Tests that are specific to macaques will lead to better understanding of human disease. Researchers have used human genome data for DNA testing, but macaque DNA chips are being developed that are more sensitive and accurate, Gibbs said.

Moreover, sequencing the macaque genome will show more about the animal itself, Gibbs said. There are about 200 genes that changed during evolution, making them candidates for determining the differences among primates, he noted.

One expert agreed that sequencing the macaque will help in understanding the evolutionary differences between apes and humans.

"When we looked at the chimpanzees, we saw difference between humans, but we did not know in which lineage a particular difference had occurred," said Tarjei Mikkelsen, who was a lead researcher in sequencing the chimpanzee genome and is on the faculty of the Broad Institute. "Now that we have another group, we can differentiate between changes that occur in the human lineage and changes that occur in the primate lineage."

Mikkelsen also thinks that having the macaque genome is important in seeing how humans differ from these primate relatives. "It's difficult to know what makes humans special having just the human genome and one primate genome -- you don't really know what's special about the human genome," he said. "The more primates you can compare yourself to, the more human-specific features you can find."

Mikkelsen also thinks that having the macaque genome will be an important resource for biomedical research.

More information

For more information on the human genome, visit the Human Genome Project.

SOURCES: Richard A. Gibbs, Ph.D., director, Baylor College of Medicine Human Genome Sequencing Center, Houston; Tarjei Mikkelsen, faculty, Broad Institute, Cambridge, Mass.; April 13, 2007, Science