The genomics of ethnicity

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Researchers have assembled the first-ever map of copy number variants (CNV)-- duplications, deletions or rearrangements in the genome that result in different gene copy numbers -- in African Americans. The study, appearing in linkurl:__BMC Genetics__;http://www.biomedcentral.com/bmcgenet/ today, also identified two CNVs that differed in frequency between African American genomes and those in people of European descent. linkurl:Joseph McElroy,;http://www.msgenes.ucsf.edu/fellows_Joseph_McElroy_Ph.D.html a postdoc in the lab of neurologist linkurl:Jorge Oksenberg;http://www.msgenes.ucsf.edu/faculty.html at the University of California, San Francisco, and lead author, said that the study will provide a baseline informing his lab's future investigations into the genetic underpinnings of multiple sclerosis in African Americans. "The reason we wanted to [compare CNVs in African Americans and whites] is because most of the literature on this has been done in whites," he said. "On a genome-wide level, African Americans haven't been studied for diseases that are present in African American populations." McElroy and his colleagues screened the genomes of 385 healthy African Americans, and 435 healthy white people primarily from Europe or North America. The researchers found a total of 1972 CNVs in white subjects and 1362 CNVs in African Americans - overall, a statistically insignificant difference. They did pull out two significant differences: a duplication on chromosome 17 that was nearly six times more frequent in whites and another on chromosome 15 that was almost twice as common in whites than in African Americans. "What they found was not surprising in the sense that African Americans are as variable as Caucasians," said linkurl:Bob Ferrell,;http://www.hgen.pitt.edu/show_faculty.php?id=37 a human geneticist at the University of Pittsburgh who was not involved with the study. "It'll only become important if it turns out that one or more of these regions where blacks and whites differ is related to susceptibility to some disease or genotype." Unsurprising as they may be, the findings might lay the groundwork for individual or ethnicity-based disease treatments that target unique genetic signatures in patients. Much work remains to be done, however, before such personalized or ethnicity-based therapies become a reality, McElroy said. "I can see that in the far future as being a goal," he said, "but our basic goal is to understand the mechanisms that are causing disease." CNVs have already been linked to a few complex diseases, such as linkurl:Crohn's disease,;http://www.cell.com/AJHG/abstract/S0002-9297(07)62743-8 linkurl:rheumatoid arthritis;http://ard.bmj.com/cgi/content/abstract/67/3/409 and linkurl:diabetes.;http://www.ncbi.nlm.nih.gov/pubmed/19276887?ordinalpos=1&itool=EntrezSystem2.PEntrez.Pubmed.Pubmed_ResultsPanel.Pubmed_DefaultReportPanel.Pubmed_RVDocSum "It's being recognized that an increasing number of diseases have some contribution from CNVs," noted Ferrell. "I would not be surprised to find out that susceptibility to certain diseases is due to copy number variation, but we don't have a lot of examples." Ferrell added that another of the study's findings may be more important in the short-term for researchers. McElroy and his group screened DNA from both whole blood and transformed lymphoblastoid cell lines in their subjects and found significant differences in CNV frequencies between the two. "There may be many studies that are flawed or have errors in their conclusions because of this," Ferrell said, noting that the HapMap project, for one, relied only on DNA derived from transformed cell lines. "It would make me very cautious about the use of cell lines." McElroy said that he is now examining CNV frequency in African Americans with multiple sclerosis and healthy subjects to look for a difference between the two groups. He added that African Americans tend to have a more aggressive form of the disease, even though the overall frequency of MS is lower in the African American population.
**__Related stories:__***linkurl:Restructuring Human Variation;http://www.the-scientist.com/article/display/54856/
[August 2008]*linkurl:Genomic Alterations 2.0;http://www.the-scientist.com/article/display/53607/
[October 2007]*linkurl:Copy number linked to autism;http://www.the-scientist.com/news/display/52940/
[15th March 2007]

The genomics of ethnicity

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