The International HapMap Consortium today published a comprehensive catalog of human genetic variation, a landmark achievement that is already accelerating the search for genes involved in common diseases, such as asthma, diabetes, cancer and heart disease.
In a paper in the October 27 issue of the journal Nature , more than 200 researchers from Canada, China, Japan, Nigeria, the United Kingdom and the United States describe the initial results from their public-private effort to chart the patterns of genetic variation that are common in the world's population. The results provide overwhelming evidence that variation in the human genome is organized into local neighborhoods, called haplotypes, that usually are inherited as intact blocks of information.
"This represents a milestone for medical research. Built upon the foundation laid by the human genome sequence, the HapMap provides a powerful new tool for exploring the root causes of common diseases. Such understanding is required for researchers to develop new and much-needed approaches to prevent, diagnose and treat diseases, such as diabetes, bipolar disorder, cancer and many others, " said David Altshuler, M.D., Ph.D., of the Broad Institute of Harvard and MIT in Cambridge, Mass., who along with Peter Donnelly, Ph.D., of the University of Oxford in England are the paper's corresponding authors.
Any two unrelated people are 99.9 percent identical at the genetic level. However, it is important to understand the 0.1 percent difference because it can help explain why one person is more susceptible to a disease or responds differently to a drug or an environmental factor than another person.
"The HapMap is a phenomenal tool that is making possible research that was impractical, if not unimaginable, only a few years ago," said Yusuke Nakamura, M.D., Ph.D., director of the University of Tokyo's Human Genome Center, as well as leader of the RIKEN SNP Center and the Japanese group working on the HapMap. "It offers the scientific community an enormous savings, reducing the expense of searching the genome for hereditary factors in common disease by a factor of 10 to 20."
Gene hunters around the world have been quick to recognize the potential of the HapMap, tapping into its publicly available SNP datasets even before the first draft of the map was completed. For example, in studies published in March in the journal Science, scientists used HapMap data to uncover a genetic variation that substantially increases the risk of age-related macular degeneration, the leading cause of severe vision loss in the elderly. The discovery of this single spelling variant out of the 3 billion letter DNA instruction book for humans, which affects a gene that codes for a protein involved in inflammation, points the way for development of better diagnostic tests and treatments for this debilitating disease.
Many other discoveries lie on the horizon as the HapMap empowers studies of other common diseases, including diabetes, Alzheimer's disease, cancer, schizophrenia, asthma, hypertension and heart disease. In fact, more than 70 papers and presentations related to the HapMap are on the program for this week's meeting of the American Society of Human Genetics in Salt Lake City .
In addition to assisting in the identification of genetic factors involved in disease, the HapMap can help to pinpoint genetic variations that may affect the response of people to medications, toxic substances and environmental factors. Such information can be used to help doctors prescribe the right drug in the right dose for each patient, as well as recommend prevention strategies that take into account individuals' varying responses to environmental factors, such as diet. Also, the HapMap may be used to find genetic factors that contribute to good health, such as those protecting against infectious diseases or promoting longevity.
Researchers produced the HapMap using DNA from blood samples collected from 269 volunteers from widely distributed geographic regions. Specifically, the samples came from Yoruba in Ibadan, Nigeria; Japanese in Tokyo, Han Chinese in Beijing and Utah residents with ancestry from northern and western Europe. No medical or personal identifying information was obtained from the donors. However, the samples are identified by the population from which they were collected.
In addition to its intended function as a resource for studies of human health and disease, the Phase I HapMap has yielded fascinating clues into how our species evolved over time and specific forces that were important as the human population spread around the globe.
Genetic diversity in humans is increased by recombination, which is the swapping of DNA from the maternal and paternal lines. It has been recently realized that in humans, most such swapping occurs primarily at a limited number of "hotspots" in the genome. By analyzing the HapMap data, the researchers have produced a genome-wide inventory of where recombination takes place. This will enable more detailed studies of this fundamental property of inheritance, as well as serve to improve the design of genetic studies of disease.
Adapted from the following source: National Human Genome Research Institute