In September, 2011, the Consortium on Asthma among African-ancestry Populations in the Americas (CAAPA) received support from the National Institutes of Health, National Heart, Lung and Blood Institute, to achieve two broad goals:
discovery of genes conferring risk to asthma among individuals of African ancestry
catalog genetic diversity in populations of African descent, especially those whose ancestry reflects the African Diaspora in the Americas.
To achieve these goals, CAAPA investigators are integrated publicly available databases (i.e., 1000 Genomes Project, genomic and exomic sequence data generated as part of NIH-supported ARRA projects), with whole genome sequencing data, generated on ~1,000 asthmatics and non-asthmatics, all of African ancestry, selected across North & South America, the Caribbean, and continental Africa, to represent a large spectrum of African ancestry. In the second phase of CAAPA, we developed a custom, gene-centric SNP genotyping array of up to 1M variants, appropriate for individuals of African descent to complement current, commercially available genomewide chips, which provide sub-optimal tagging of known genes among individuals of African descent. This “African Power Chip” can be used to build upon GWAS studies in populations of African descent. Once developed, This SNP chip was genotyped on >12,000 DNA samples representing African American and African Caribbean asthmatics and non-asthmatics. Genotype data from this SNP chip was combined with existing GWAS data to test for association to identify candidate genes for asthma in populations of African descent. CAAPA involves a well-established group of experienced investigators, representing 10 national and 5 international academic institutions, with diverse but integrated areas of expertise.
Asthma is a complex chronic lung disease that affects the airways. Asthma has striking disparities across racial and ethnic groups.
Asthma in African ancestry
Asthmatics of African descent tend to have more severe asthma and more severe clinical symptoms than individuals of European ancestry. See CDC annual report and National Institute on Minority Health and Health disparities.
Advances in genetic and genomic technologies have revolutionized gene discovery for several complex diseases, but going to the next step in gene discovery for asthma among populations of African descent requires considering unique characteristics of this ethnic group, including adequate sample sizes, population stratification due to (European and African) admixture, and perhaps most importantly, an approach that recognizes the current coverage of common genetic markers both in public databases and commercially available SNP chips, which have been inadequate to detect and measure genetic associations among African admixed populations.
The Consortium on Asthma among African-ancestry Populations in the Americas (CAAPA) is funded by the National Institutes of Health, National Heart, Lung and Blood Institute (NHLBI) to investigate the genetics of asthma in African ancestry populations.
Developing ADPC (The African diaspora Power Chip) is a genotyping array consisting of tagging SNPs, useful in comprehensively identifying African specific genetic variation. The paper from Johnston et.al highlights the significance of ADPC.
The MEGA (Multi Ethnic Genotyping Array) from Illumina leverages the CAAPA and Population Architechture in Genomics and Epidemiology (PAGE) studies, to produce arrays with comprehensive multi-ethnic coverage and updated functional and exome content.
CAAPA genomes are available as a reference panel on the michigan imputation server.
CAAPA data is available to download on dbGAP with Accession ID:phs001123.v1.p1.
population genetics point of view: Tales of African American History found in DNA