Scientists have identified a genetic variant which increases susceptibility to tuberculosis (TB) in African populations using a technique known as a genome-wide association (GWA) study. This is the first novel disease variant to be identified using this technique in Africans and demonstrates that such studies are viable in African populations, which have a high degree of genetic diversity.
Over the past few years, GWA studies, such as the Wellcome Trust Case Control Consortium, have been increasingly effective at identifying genetic variants which increase susceptibility to diseases. The studies involve analysing hundreds of thousands of genetic markers across the human genomes in search of variants found in patients ('cases') but not in healthy volunteers ('controls').
So far, over 150 different studies have successfully identified genetic variants using this technique, but the vast majority - between 95-98% - have been only in people of European ancestry. The genetic diversity of African populations makes GWA studies far more complicated and had even led some researchers to question whether these studies would work in such populations.
Researchers carried out a GWA study, and replicated their findings, using over 11,000 samples - 3,699 cases and 7,726 controls - from Ghana, The Gambia and Malawi as part of the African TB Genetics Consortium and the Wellcome Trust Case Control Consortium in search of genetic variants that increase susceptibility to TB.
TB is one of the world's most deadly diseases, caused by the bacterium Mycobacterium tuberculosis. One third of the world's population are believed to be infected with M. tuberculosis. Each year, at least nine million people are in need of treatment for TB, and more than two million people die from the disease.
The results of the study, led by Professor Adrian Hill from the University of Oxford, UK, and Professor Rolf Horstmann from the Bernhard Nocht Institute for Tropical Medicine in Hamburg, Germany, are published in the journal Nature Genetics.
Dr Fredrik Vannberg from the Wellcome Trust Centre for Human Genetics at the University of Oxford says: "Our challenges here were two-fold. We were looking for human genetic variants affecting susceptibility to a pathogen which itself differs genetically from region-to-region, and we were searching for these variants in African populations, which are genetically very diverse."
The researchers identified a genetic variant on chromosome 18, located in a 'gene desert', a region composed mainly of so-called 'junk DNA', which suggested that the variant itself was not a gene, but was possibly involved in gene regulation. The surrounding area appears to be highly conserved - in other words, it is relatively unchanged across a number of species - which implies that the region plays an important role in the body's function.
Article Date: 09 Aug 2010
http://www.medicalnewstoday.com/articles/197226.php
