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Chilean Population Study Sees Disease Risk Differences Tracking With Native American Ancestry

NEW YORK (GenomeWeb) – The Native American portion of the genome of individuals from Latin American populations may hold clues to their susceptibility for some conditions, new research suggests.

An international team led by investigators in Germany considered array-based genotyping profiles for thousands of individuals from Chile, teasing out Native American ancestry tracts associated with Mapuche and Aymara populations — that country's main Native American groups.

The findings, appearing online in PLOS Genetics, suggest that the risk of conditions such as gallbladder cancer and asthma tended to creep up along with higher levels of Mapuche ancestry, while diabetes mortality declined. In contrast, the team noted, Aymara ancestry appeared to coincide with rising risks of certain cancers such as skin cancer, bladder cancer, lung cancer, and cancers of the larynx or bronchus, but lower-than-usual circulatory system disease or gallbladder cancer risk.

"This study demonstrates that considering the origin of the Native American component of ancestry can be crucial to identify existing associations with human disease," co-first author Justo Lorenzo Bermejo, a statistical genetics researcher at the University of Heidelberg, said in a statement. "We plan to exploit this finding in future studies on Latin American health, in particular common cancers and infectious diseases in South America."

The team started by bringing together genotyping data for 1,805 individuals from Chile, looking at the relationships, if any, between Mapuche ancestry, Aymara ancestry, and disease-specific mortality rates reported for the same individuals between 2005 and 2011. It teased out those Native American ancestry tracts using clues from samples previously profiled for efforts such as the Human Genome Diversity Project.

After uncovering the apparent ties between Mapuche ancestry and gallbladder cancer, the researchers turned to samples from another 64 Chileans with that condition, and 170 unaffected population controls, to confirm that association.

The authors cautioned that "some of the identified associations between ancestry proportions and disease-specific mortality risks by geographical, socioeconomic, and cultural factors" could introduce confounding factors into the findings. For example, they noted, that high levels of arsenic and ultraviolet radiation have been documented in a region in northern Chile where there are individuals with enhanced levels of Aymara ancestry, perhaps explaining some of the bladder cancer, lung cancer, and skin cancer cases in this population.

Even so, Bermejo said, "[t]he identification of health disparities among ethnic groups may have important implications for personalized prevention and disease management."

"Future studies are needed to develop and validate risk prediction models which incorporate genetic ancestry and other risk factors in order to personalize gallbladder cancer prevention," he and his co-authors wrote.