African Ancestry and Asthma
Kathleen C. Barnes, Ph.D.
Johns Hopkins Bloomberg School of Public Health
P01ES009606
In the first genome-wide association study focused on populations of African descent, a multi-institutional team of researchers identified 3 single nucleotide polymorphisms that are biologically relevant to asthma and may help to explain at least part of the profound disparities in asthma observed in different populations.
Asthma is a biologically complex disease. It is affected by many non-biological issues as well such as environmental, social, cultural and economic factors; however these factors have not proven to be the cause of the striking ethnic disparities. This study was designed to identify genes that might explain at least part of the racial disparity seen in the incidence of the disease.
A genome-wide association study, also known as whole genome association study, is an examination of genetic variation across a given genome, designed to identify genetic associations with observable traits. In human studies, this might include traits such as blood pressure or weight, or why some people get a disease or condition and others don’t. These studies normally require two groups of participants: people with the disease and similar people without. Participants are genotyped and a set of markers are usually identified that are said to be associated with the disease.
Two populations of African descent were combined in this study. One group consisted of 935 African-American and control subjects and the other consisted of 929 African Caribbean asthmatics and there family members from Barbados. The study yielded three highly statistically significant single nucleotide polymorphisms for genes that are biologically relevant to asthma. Additional studies on groups from the UK and Germany did not find the same associations. Similar associations were also not found in four other case-control studies in African Americans.
The authors conclude that additional studies of these three candidate genes are warranted to confirm the possible uniqueness of the observed associations to populations of African descent. Because of the difficulty in finding SNP-for-SNP replication in all of the African populations, they suggest conducting fine-mapping studies around these three genes.
Citation: Mathias RA, Grant AV, Rafaels N, Hand T, Gao L, Vergara C, Tsai YJ, Yang M, Campbell M, Foster C, Gao P, Togias A, Hansel NN, Diette G, Adkinson NF, Liu MC, Faruque M, Dunston GM, Watson HR, Bracken MB, Hoh J, Maul P, Maul T, Jedlicka AE, Murray T, Hetmanski JB, Ashworth R, Ongaco CM, Hetrick KN, Doheny KF, Pugh EW, Rotimi CN, Ford J, Eng C, Burchard EG, Sleiman PM, Hakonarson H, Forno E, Raby BA, Weiss ST, Scott AF, Kabesch M, Liang L, Abecasis G, Moffatt MF, Cookson WO, Ruczinski I, Beaty TH, Barnes KC. A genome-wide association study on African-ancestry populations for asthma. J Allergy Clin Immunol. 2010 Feb;125(2):336-346.e4.
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