African Americans and Afro-Africans
The assessment of the genetic risk of diseases for African Americans cannot be applied to residents of sub-Saharan Africa
Natalia Kulygina, PCR.news
Studies of the genetic risk of lipid metabolism disorders are carried out mainly on people of European and Asian origin. Their results cannot be used for African populations. An international team of scientists has shown that polygenic risk indices calculated for African Americans generally work better, but their predictive value varies greatly for different African ethnic groups.
Assessment of the polygenic risk of diseases is a promising and developing direction in human genetics. However, the information on genetic risks obtained for European and Asian populations cannot be used for the African population. The authors of the new work suggested that this gap can be filled by data on Americans of African descent. They tested this assumption with the help of the Million Veterans program of the US Department of Veterans Affairs, a large—scale cohort study launched in 2011. Now the biobank of the program contains samples and data of hundreds of thousands of individuals.
The researchers focused on the signs of lipid metabolism disorders, including low- and high-density lipoprotein cholesterol (LDL-C and HDL-C), triglycerides (TG) and total cholesterol (TC). Based on the summary statistics of the Million Veterans program, they calculated the polygenic risk index for people of African and European descent, as well as for mixed populations. The obtained indices were applied to two cohorts from sub—Saharan Africa: one included Ugandans, the second - Zulus.
Indeed, estimates of the genetic risks of lipid metabolism disorders based on data on African Americans work better for populations from Africa than estimates calculated for Americans of European or mixed origin. However, there are significant differences between the Ugandan and Zulu cohorts. For Zulus, the assessment of genetic risks explains 8.14% of the deviations in LDL-C levels in the blood, for Ugandans — only 0.026%. The same pattern was observed for other indicators. According to the authors, this may be due to the different allelic frequency of risk variants in these two cohorts, as well as environmental factors: the Zulu cohort consisted of urban residents, and the Ugandan cohort consisted mainly of rural residents.
The authors believe that the assessment of genetic risks of diseases for residents of sub-Saharan Africa, calculated on the basis of data on Americans of African descent, cannot be applied in the clinic. It doesn't work well for different ethnic groups. Further optimization of polygenic risk assessment in African populations is needed.
Article by Kamiza et al. Transferability of genetic risk scores in African populations is published in the journal Nature Medicine.
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