Monday, July 24, 2006

Gibbon Genome Sequence To Be Added To Primate Tree

The National Human Genome Research Institute (NHGRI), one of the National Institutes of Health (NIH), today announced several new sequencing targets including the Northern white-cheeked gibbon (Nomascus leucogenys), setting the stage for completing a quest to sequence the genome of at least one non-human primate genome from each of the major positions along the evolutionary primate tree and making available an essential resource for researchers unraveling the genetic factors involved in human health and disease. Comparing the genomes of other species to humans is an exceptionally powerful tool to help researchers understand the working parts of the human genome in both health and illness.

NHGRI's Large-Scale Sequencing Research Network and their international partners have already sequenced - or have been approved to sequence - at high-density coverage the genomes of several non-human primates including the chimpanzee (Pan troglodytes), the rhesus macaque (Macaca mulatta), the orangutan (Pongo pygmaeus), marmoset (Callithrix jacchus) and the gorilla (Gorilla gorilla).

"The gibbon genome sequence will provide researchers with crucial information when comparing it to the human genome sequence and other primate genomes, shedding light on molecular mechanisms implicated in human health and disease - from infectious diseases and neurological disorders to mental illness and cancer," said NHGRI Director Francis S. Collins, M.D., Ph.D.

The gibbon genome is unique because it carries an extraordinary high number of chromosome rearrangements, even when compared to other primates. These rearrangements occur when small or large segments of a chromosome become detached and reattach to the same chromosome or another chromosome. Such chromosomal rearrangements can wreak havoc on a cell, and can contribute to birth defects or cancer in humans. The gibbon genome will also help scientists better understand rearrangements called segmental duplications, which are large, almost identical copies of DNA present in at least two locations in the human genome. A number of diseases are known to be associated with mutations in segmental duplicated regions, including a form of mental retardation and other neurological and birth defects.

Segmental duplications cover 5.3 percent of the human genome, significantly more than in the rat genome, which has about 3 percent, or the mouse genome, which has between 1 and 2 percent. Segmental duplications provide a window into understanding how the human genome evolved and how it may still be changing. The high proportion of segmental duplications in the human genome shows how human genes have undergone rapid functional innovation and structural change during the last 40 million years, presumably contributing to unique characteristics that separate humans from non-human primate ancestors.

With the sequencing of major primate genomes, researchers are able to more precisely study the differences between primates and humans. For instance, an analysis of the chimpanzee genome sequence has revealed that three key genes involved in inflammation have been deleted in the chimpanzee genome, possibly explaining some of the known differences between immune and inflammatory responses of chimps and humans. Identifying these genes gives researchers a more precise starting point for understanding molecular pathways and developing better diagnostics and therapies involved in immune and inflammatory diseases.

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