GENETIC DRIFT AMONG NATIVE PEOPLE FROM SOUTH AMERICAN GRAN CHACO REGION AFFECTS INTERLEUKIN 1 RECEPTOR ANTAGONIST VARIATION

CATANESI C I; GLESMANN, LA

Natural Selection and Genetic Drift

Nova

Lugar: New York; Año: 2015; p. 101 - 118

Genetic variation is generally responsible for ethnic differences in certain diseases,including inflammatory processes. The antagonist of cytokine IL-1, IL-1Ra, hasbeen widely studied among Caucasian and African populations for geneticpolymorphisms, and interethnic differences have been documented.  However, thevariation and genotype distribution of polymorphisms from these genes amongSouth American Amerindians are thus far unknown. We present the results for aVNTR located in the IL-1Ra second intron, in a sample of 169 individualsbelonging to 5 Native American populations from Argentina and Paraguay,identified as native according to their self designation, and their geographiclocation. We also compare this data with the results obtained from a sample ofnon-native Argentinian people. Among the five known alleles of the VNTR, wefound only two (alleles 1 and 2) in the native populations from Gran Chaco, andheterozygosity was 19%. The allele 2 which is considered proinflammatory(IL-1Ra * 2) has been found in homozygosity at a considerable frequency among nativeindividuals. However, the association of this allele with inflammatory diseasepreviously demonstrated for other populations of the world, might not be actingin the same way for native people, probably due to local adaptation. This wouldindicate that the allele 2 will probably not have a negative influence onindividuals of native origin who have homozygous genotype 2-2. On the contrary, few records on inflammatory disease are available for the native people.  It seems that the increment on allele 2 is notrelated to any adaptive process but to genetic drift, that changes randomly theallele frequencies of different genetic regions along the genome. The effect ofgenetic drift has already been demonstrated with genetic markers located in Xand Y chromosomes. These results indicate that we must be very cautious whenstudying populations that passed a process of genetic drift, which can become aconfounding factor in epidemiological studies. This information will contributeto a future understanding of the association of this polymorphism with disease,and its incidence in different ethnic groups.