HLA class II diversity in seven Amerindian populations. Clues about the origins of the Aché

Abstract

The study of the HLA variability of Native American populations revealed several alleles specific to one or more of the Latin American indigenous populations. The analysis of Amerindian groups distributed all over the continent might inform about the area of origin and the dispersal of these alleles and shed light on the evolution of this remarkable polymorphism. Moreover, HLA alleles and haplotypes are excellent markers to understand the genetic relationships between populations. For these reasons, we characterized the HLA class II polymorphism in seven South American Amerindian populations and compared the results with those previously reported for other Amerindian groups. The Guarani-Kaiowá (n = 160) and Guarani-Nandeva (n = 87) were from the Brazilian state of Mato Grosso do Sul, the Guarani-M'byá (n = 93) and Kaingang (n = 235) from Paraná state, the Aché (n = 89) from eastern Paraguay, the Quechua (n = 44) from Andean Peru. From Amazonia, a heterogeneous group was analyzed (n = 45). The most frequent alleles and haplotypes are common also in other Amerindian populations. Each HLA-DRB1 allele was typically found in combination with just one DQA1-DQB1 haplotype, most likely as a result of some form of random genetic drift and reduced gene flow from non-Amerindians. The frequency distribution differed significantly among all populations, although differences were less pronounced between the Guarani subgroups. Marker alleles allowed an estimate of European and sub-Saharan African gene flow into these populations: Quechua 23%, Guarani-Nandeva 14%, Kaingang 7%, Guarani-M'byá 4%, Guarani-Kaiowá, Amazonia, and Aché 0%. Interestingly, the DRB1*1413 allele, previously found only among the Guarani-M'byá (frequency 15%), appeared in the Aché (8%). The relationship of the Aché to other Amerindian populations is unclear, and this finding reveals a link with the Guarani. On the basis of genetic distance and the HLA allele/haplotype set, we propose that the Aché are differentiated Tupi-Guarani group, most closely related to the Guarani-M'byá.

Butyrylcholinesterase genetic variability in Guarani Amerindians from the Brazilian state of Mato Grosso do Sul

“…Alcântara et al (1995) have reported that the Guarani-M'byá sub-group from Rio das Cobras, in the Brazilian state of Paraná, has a CHE2 C5+ frequency of 45.93% ± 3.80% and when this was compared with the present data (14.40% ± 2.22%), a statistically significant difference was found (c 2 = 51.10; p < 0.0001%). The present data on CHE2 C5+ phenotype frequencies are in the same direction as data previously obtained on the basis of HLA-DRB1 allele frequencies which led to estimates of genetic distances between the M'byá and Kaiowá (0.0410), M'byá and Ñandeva (0.0307) and Kaiowá and Ñandeva (0.0165) (Tsuneto et al, 2003;Petzl-Erler, 2005, pers. comm.).…”

“…The degree of non-Amerindian admixture was estimated as 17% in the Guarani-Ñandeva and 3% in the Guarani-Kaiowá sub-groups (Tsuneto, 2003) on the basis of the frequency of HLA haplotypes present in Europeans and Africans and only found in Amerindians as due to admixture. Considering the ethnic composition of the 250 Amerindians examined for the D70G variant (64% GuaraniKaiowá and 36% Guarani-Ñandeva), the respective degrees of admixture of these sub-groups and the frequency of 1.5% of this variant in Euro-Brazilians (Chautard-Freire- Maia et al, 1984), the expected frequency for the D70G variant in this Guarani sample (0.12%) due only to European admixture is statistically lower than the one found (c 2 = 9.61; p < 0.01).…”

“…The hypothesis of absence of the A539T allele in the ancient South American Amerindians and of its present occurrence due to admixture with individuals of European and African origin was tested using the degree of admixture Furtado et al 11 (17% in the Guarani-Ñandeva and 3% in the Guarani-Kaiowá sub-groups) reported by Tsuneto (2003). Considering that the A539T allele frequency is 17.80% in Euro-and Afro-Brazilians (Souza et al, 1998), the expected frequency due only to admixture for the A539T variant in this Guarani sample would be 1.38% and is statistically lower (c 2 = 19.14, p < 0.001) than the 3.69% found in the present study.…”

High frequencies of alleles MICA*020 and MICA*027 in Amerindians and evidence of positive selection on exon 3

“…The distinctiveness of the Guarani and Kaingang populations is in line with the results of earlier studies. 25,26 Among the Amerindians, Guarani Ñ andeva had the highest genetic diversity, which agrees with the relatively high amount of gene flow (14%) from nonAmerindians into this population. 25 On the other hand, Guarani M'byá had a lower diversity and the highest levels of LD, possibly reflecting their genetic isolation and the effect of random genetic drift.…”

“…Guarani and Kaingang live close to each other but have remarkable genetic and cultural differences. 24,25 Another important feature of these populations is that gene flow from non-Amerindian and other Amerindian populations is low, with the exception of Guarani Ñ andeva, whose admixture was estimated as 14%. 25,26 The aim of this study was to describe STR_MICA and MICA allelic frequencies and MICA-HLA-B-HLA-C associations in the Guarani and Kaingang populations from Brazil, to compare the diversity found with that of other populations and to extract information about the evolution of MICA polymorphism.…”