Genetic variability in Amerindian populations of Northern Argentina

Fine-scale genomic analyses of admixed individuals reveal unrecognized genetic ancestry components in Argentina

Similarly to other populations across the Americas, Argentinean populations trace back their genetic ancestry into African, European and Native American ancestors, reflecting a complex demographic history with multiple migration and admixture events in pre- and post-colonial times. However, little is known about the sub-continental origins of these three main ancestries. We present new high-throughput genotyping data for 87 admixed individuals across Argentina. This data was combined to previously published data for admixed individuals in the region and then compared to different reference panels specifically built to perform population structure analyses at a sub-continental level. Concerning the Native American ancestry, we could identify four Native American components segregating in modern Argentinean populations. Three of them are also found in modern South American populations and are specifically represented in Central Andes, Central Chile/Patagonia, and Subtropical and Tropical Forests geographic areas. The fourth component might be specific to the Central Western region of Argentina, and it is not well represented in any genomic data from the literature. As for the European and African ancestries, we confirmed previous results about origins from Southern Europe, Western and Central Western Africa, and we provide evidences for the presence of Northern European and Eastern African ancestries.

Genetic structure of Mataco-Guaycurú speakers from Argentina and the extent of their genetic admixture with neighbouring urban populations

Argentina hosts more than 30 Native American groups, who are widely distributed throughout the country. Mataco-Guaycurú speakers settled in the ecoregion of Gran Chaco and represent 26.7% of the extant aboriginal population of the country. To further investigate the genetic attributes of these speakers, we focused our attention on four aboriginal groups, namely, Wichí, Toba, Pilagá and Mocoví, belonging to the Mataco-Guaycurú linguistic group. Our main goal was to evaluate the interrelationships among the groups and the relationships of these groups with admixed urban populations and to assess correspondences between molecular analysis and historical information. A total of 890 samples (282 Native Americans and 608 inhabitants of admixed urban areas) were analysed. Genetic information was gathered from 15 autosomal STRs, 17 Y-STRs, entire mtDNA control region sequences, 24 AIM-SNPs and 46 AIM-DIPs. Native American signatures were detected in 97.9% of mtDNA lineages, 89.1% of Y-haplotypes and 90.3% to 96.9% of autosomal markers. Wichí exhibited the genetic composition with the largest Native American contribution among the groups and a weak signal of gene flow. This work provides extended genetic information of potential interest in the fields of molecular anthropology and forensic genetics.

HLA-DRB1 alleles in four Amerindian populations from Argentina and Paraguay

The major histocompatibility complex (MHC) is one of the biological systems of major polymorphisms. The study of HLA class II variability has allowed the identification of several alleles that are characteristic to Amerindian populations, and it is an excellent tool to define the relations and biological affinities among them. In this work, we analyzed the allelic distribution of the HLA-DRB1 class II locus in four Amerindian populations: Mapuche (n = 34) and Tehuelche (n = 23) from the Patagonian region of Argentina, and Wichi SV (n = 24) and Lengua (n = 17) from the Argentinean and Paraguayan Chaco regions, respectively. In all of these groups, relatively high frequencies of Amerindian HLA-DRB1 alleles were observed (DRB1*0403, DRB1*0407, DRB1*0411, DRB1*0417, DRB1*0802, DRB1*0901, DRB1*1402, DRB1*1406 and DRB1*1602). However, we also detected the presence of non-Amerindian variants in Mapuche (35%) and Tehuelche (22%). We compared our data with those obtained in six indigenous groups of the Argentinean Chaco region and in a sample from Buenos Aires City. The genetic distance dendrogram showed a clear-cut division between the Patagonian and Chaco populations, which formed two different clusters. In spite of their linguistic differences, it can be inferred that the biological affinities observed are in concordance with the geographic distributions and interethnic relations established among the groups studied.

Autosomal STR genetic variability in the Gran Chaco native population: Homogeneity or heterogeneity?

To investigate the population structure and variation in Gran Chaco's Amerindian population, data from 15 short tandem repeats (STRs) were determined in 128 individuals from three tribes of the Argentinean part of this region. STR genotypic differences, structure analysis, and multidimensional plot for the D(A) distances indicated that (1) Wichí from the Chaco Province are genetically distinct from the other populations, but still preserve a fair amount of genetic similarity with Wichí from Formosa; (2) the Toba populations studied are genetically indistinguishable; and (3) Toba subjects from Formosa are similar to the Pilagá of the same linguistic group (Guaykurú) and to the Wichí from Formosa who speak a Mataco language. This similarity could be due to their past mobility and the custom of absorbing females taken as prisoners from groups raided by them. Language, geography, and genetics seem to play similar roles in determining the population structure of these groups. Analyses of molecular variance and G(ST)' values calculated considering three South American regions indicated that the Argentinean Chaco is genetically homogeneous; addition of the Ayoreo Amerindians of the Paraguayan Chaco, however, led to diversity values that are not much different from those of South Amerindians in general. The present data contribute to efforts that try to understand in what way groups with diverse sociocultural settings (tribal, agricultural, and industrial) differ in genetic structure.

Human colonization of the central territory of Argentina: Design matrix models and craniometric evidence

In this study we test several hypotheses about the peopling of the central territory of Argentina, archaeologically known as Sierras Centrales, by testing the association between four alternative models of the peopling of the area and cranial morphological variation through distance and matrix correlation analyses. Our results show that the ancient inhabitants of Sierras Centrales demonstrated close morphological similarities with the Patagonian and Tierra del Fuego populations. Moreover, the correlation and partial correlation analyses suggest that the peopling of the Sierras Centrales most likely took place as a migratory wave proceeding from the present area of Northeastern Argentina, and continued southward to Patagonia and Tierra del Fuego.

Allele and genotype frequencies of metabolic genes in Native Americans from Argentina and Paraguay

Interethnic differences in the allele frequencies of CYP2D6, NAT2, GSTM1 and GSTT1 deletions have been documented for Caucasians, Asians, and Africans population. On the other hand, data on Amerindians are scanty and limited to a few populations from southern areas of South America. In this report we analyze the frequencies of 11 allele variants of CYP2D6 and 4 allele variants of NAT2 genes, and the frequency of GSTM1 and GSTT1 homozygous deleted genotypes in a sample of 90 donors representing 8 Native American populations from Argentina and Paraguay, identified as Amerindians on the basis of their geographic location, genealogical data, mitochondrial- and Y-chromosome DNA markers. For CYP2D6, 88.6% of the total allele frequency corresponded to *1, *2, *4 and *10 variants. Average frequencies for NAT2 *4, *5, *6 and *7 alleles were 51.2%, 25%, 6.1%, and 20.1%, respectively. GSTM1 deletion ranged from 20% to 66%, while GSTT1 deletion was present in four populations in less than 50%. We assume that CYP2D6 *2, *4, *10, *14; NAT2 *5, *7 alleles and GSTM1 and GSTT1 *0/*0 genotypes are founder variants brought to America by the first Asian settlers.