Spotlight on European American DNA
Genome mapping - the creation of a genetic map assigning DNA fragments to chromosomes - rose to the surface in the 1970s when scientists first understood how to isolate and interpret gene or DNA sequences. Scientists the world over are working on a variety of genomes, including those of humans, yeast and animals. A team of researchers recently sought to uncover the genetic diversity of Europeans who immigrated to the United States. Their work, which provides the first genetic dissection of the population structure, was published in the Open Access journal PLoS Genetics in January. US census categories show that European Americans are the single most populous ethnic group found on the other side of the pond, and they are typically sampled in genetic association studies. The 'Discerning the Ancestry of European Americans in Genetic Association Studies' focused on identifying the contributions from different genetic ancestries that play a key role in disease gene mapping. According to the researchers, it is important to understand and explain the population subculture that exists within European American populations. This will ensure that genetic association studies yield correct findings if disease cases are compared to healthy controls, which on average have different ancestry. The research team evaluated data obtained from four disease associations studies in European Americans so as to describe and characterise the majority of population substructures in European Americans that could result in false-positive associations. 'Although our work is far from a complete description of European American population history, for the purpose of disease gene mapping studies it is adequate to measure how closely each person's genetic ancestry resembles three populations that can be roughly described as northwest European, southeast European, or Ashkenazi Jewish,' explains Harvard Medical School's Dr David Reich, who is a senior author of the study. 'With this approach, we can avoid most false-positive associations due to population substructure in European American disease gene mapping studies. Our previous work has addressed related challenges in studies of African Americans and Latino Americans.' By evaluating published data sets to key out places in the genome where common DNA sequence variants differ considerably in frequency among the three ancestral populations, the research team was able to confirm the effectiveness of these genetic variants by testing them in DNA samples collected from Greece, Italy, Poland, Spain, Sweden, UK and US. 'We identified 300 common genetic variants that have unusually different frequencies in the three ancestral populations: they are about 10 times more informative for predicting the ancestry of European Americans than random genetic variants,' says Dr Alkes Price, the lead author of the study. 'We can thus correct for population substructure in European American disease association studies using just these 300 markers.' Dr Joel Hirschhorn, also a senior author of the study, remarks that despite the fact that the 300 markers 'give a reasonable estimate of the major components of genetic ancestry in European Americans, self-described ethnicity can still reflect environmental, social and cultural factors that may not be captured by estimating genetic ancestry'. Dr Hirschhorn goes on to say that this study will prove instrumental in raising awareness and heightening understanding of human biology in health and disease. The upshot of this would be better healthcare for patients in the long run.
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