To characterize the haplotype patterns of the MHC, the researchers analyzed the variability in its DNA sequence in more than 350 individuals from diverse geographic regions, including Africa, Europe, China and Japan. Specifically, the researchers "read" ~7,500 single-letter changes in the genetic code called single nucleotide polymorphisms (SNPs) together with short segments of DNA sequence from a set of highly variable genes within the MHC, called "HLA genes." These genes form a distinctive fingerprint that is recognized by an individual's immune system to distinguish foreign tissues from "self" tissues and the genes' DNA sequences are frequently analyzed (a process called "HLA typing") in patients who receive organ transplants or suffer from autoimmune disease.
Importantly, the researchers' data and analyses, which are made available online to the entire scientific community, provide the tools needed to begin the initial efforts toward identifying genetic risk factors in the MHC for common immune-mediated diseases. Such endeavors, involving researchers at the Montreal Heart Institute, the University of California, San Francisco and the Broad Institute of MIT and Harvard, are now underway for several immune system diseases.
In addition, the results offer insights into the evolutionary history of the MHC region -- its early origins and the evolutionary forces that have helped to shape it over time. The findings also suggest that analyzing select SNPs within the HLA genes may offer a more economical alternative for characterizing the most common genetic variants in the region than standard HLA typing methods.
Nearly three-quarters of the DNA samples that the scientists analyzed had been previously examined as part of the International Haplotype Map ("HapMap") Project, a worldwide scientific collaboration to catalogue human
Source:University of Montreal