Ancestral heterogeneity in a biethnic stroke population

Area of Science:

• Population Genetics
• Human Ancestry
• Genomic Studies

Background:

• Stroke and transient ischemic attack (TIA) research often relies on self-reported race-ethnicity.
• Genetic homogeneity is frequently assumed within self-identified racial or ethnic groups.

Purpose of the Study:

• To investigate and quantify the heterogeneity of ancestral contributions in Mexican American (MA) and non-Hispanic white (NHW) individuals within a stroke/TIA cohort.
• To assess the validity of using self-reported race-ethnicity as a proxy for genetic homogeneity in multi-ethnic populations.

Main Methods:

• Utilized data from a community-based stroke surveillance study in South Texas (2004-2006).
• Genotyped 33 ancestry-informative markers in 154 self-identified MAs and 84 self-identified NHWs.
• Estimated individual genetic admixture using maximum likelihood methods and likelihood ratio tests.

Main Results:

• Mexican Americans exhibited significant European ancestry variation (0.26-0.98, average 0.59), rejecting 100% Native American or 100% European ancestry hypotheses for most.
• Forty percent of MAs showed European ancestry proportions deviating from the average (59%).
• Non-Hispanic whites also displayed heterogeneity, with European ancestry ranging from 0.83-1.0 (average 0.97).

Conclusions:

• Self-identified Mexican Americans and, to a lesser extent, non-Hispanic whites in this bi-ethnic community demonstrate considerable genetic admixture heterogeneity.
• Researchers must exercise caution and avoid using simple race-ethnic categories as proxies for genetically homogeneous populations in gene mapping and disease association studies.