Mauricio Moraga

Mitochondrial DNA polymorphisms in Chilean aboriginal populations: Implications for the peopling of the southern cone of the continent

The mitochondrial DNAs (mtDNAs) from individuals belonging to three Chilean tribes, the Mapuche, the Pehuenche, and the Yaghan, were studied both by RFLP analysis and D-loop (control region) sequencing. RFLP analysis showed that 3 individuals (1.3%) belonged to haplogroup A, 19 (8%) to haplogroup B, 102 (43%) to haplogroup C, and 113 (47.7%) to haplogroup D. Among the 73 individuals analyzed by D-loop sequencing, we observed 37 different haplotypes defined by 52 polymorphic sites. Joint analysis of data obtained by RFLP and sequencing methods demonstrated that, regardless of the method of analysis, the mtDNA haplotypes of these three contemporary South American aborigine groups clustered into four main haplogroups, in a way similar to those previously described for other Amerindians. These results further revealed the absence of haplogroup A in both the Mapuche and Yaghan as well as the absence of haplogroup B in the Yaghan. These results suggest that the people of Tierra del Fuego are related to tribes from south-central South America.

Composición genética de la población chilena. Distribución de polimorfismos de DNA mitocondrial en grupos originarios y en la población mixta de Santiago

BACKGROUND The analysis of mitochondrial DNA restriction site polymorphisms assigns most Latin American aborgines to four haplogroups. These are characterized by determined polymorphic restriction sites and a deletion of 9 base pairs in the intergenic region V. AIM To study the distribution of mitochondrial DNA haplogroups in Chilean aboriginal groups, as well as in the mixed population of Santiago. MATERIAL AND METHODS One hundred twenty Aymara subjects and 23 Atacameño subjects from the Northern part of Chile and 162 randomly chosen subjects residing in Santiago were studied. DNA was extracted from peripheral lymphocytes. Mitochondrial DNA was amplified by means of polymerase chain reaction. RESULTS The frequency of haplogroup B decreases from north to south. Aymaras in the north have the highest frequency (64%) and it is absent among the Yamanas (previously studied) in the extreme South. Haplogroups C and D show an inverse tendency. It is noteworthy that 84% of mitochondrial haplogroups of the mixed population of Santiago are of Amerindian origin whereas the Y-chromosomes are mainly European. CONCLUSIONS The peculiar distribution of haplotypes indicate that the population of Santiago is the result of an asymmetric mating system in which the females ancestors were mainly Amerindian and the male ancestors mainly European.

Genotypic interaction between DRD4 and DAT1 loci is a high risk factor for attention-deficit/hyperactivity disorder in Chilean families.

Attention‐deficit/hyperactivity disorder, ADHD [MIM 126452], is a common, highly heritable neurobiological disorder of childhood onset, characterized by hyperactivity, impulsiveness, and/or inattentiveness. As part of an ongoing study of ADHD, we carried out a family‐based discordant sib‐pair analysis to detect possible associations between dopamine receptor D4 (DRD4) and dopamine transporter 1 (DAT1) polymorphisms and ADHD in Chilean families. Both loci individually classified as homozygotes or heterozygotes for the DRD4 7‐repeat and DAT1 10‐repeat alleles, did not exhibit genotype frequency differences between affected children and their healthy siblings (Fishers exact test P > 0.25 in both cases). However, the simultaneous presence of both DRD4 7‐repeat heterozygosity and DAT1 10 allele homozygosity were significantly higher (34.6%) in cases (26), compared with their unaffected siblings (25) (4%; Fishers exact test P = 0.0096; odds‐ratio, OR = 12.71). Increased density of dopamine transporter in ADHD brains, along with abundance of 7‐repeat D4 receptors in prefrontal cortex, which is impaired in ADHD patients, make the observed gene–gene interaction worthy of further incisive studies.

An alternative model for the early peopling of southern South America revealed by analyses of three mitochondrial DNA haplogroups.

After several years of research, there is now a consensus that America was populated from Asia through Beringia, probably at the end of the Pleistocene. But many details such as the timing, route(s), and origin of the first settlers remain uncertain. In the last decade genetic evidence has taken on a major role in elucidating the peopling of the Americas. To study the early peopling of South America, we sequenced the control region of mitochondrial DNA from 300 individuals belonging to indigenous populations of Chile and Argentina, and also obtained seven complete mitochondrial DNA sequences. We identified two novel mtDNA monophyletic clades, preliminarily designated B2l and C1b13, which together with the recently described D1g sub-haplogroup have locally high frequencies and are basically restricted to populations from the extreme south of South America. The estimated ages of D1g and B2l, about ∼15,000 years BP, together with their similar population dynamics and the high haplotype diversity shown by the networks, suggests that they probably appeared soon after the arrival of the first settlers and agrees with the dating of the earliest archaeological sites in South America (Monte Verde, Chile, 14,500 BP). One further sub-haplogroup, D4h3a5, appears to be restricted to Fuegian-Patagonian populations and reinforces our hypothesis of the continuity of the current Patagonian populations with the initial founders. Our results indicate that the extant native populations inhabiting South Chile and Argentina are a group which had a common origin, and suggest a population break between the extreme south of South America and the more northern part of the continent. Thus the early colonization process was not just an expansion from north to south, but also included movements across the Andes.

Arrival of Paleo-Indians to the Southern Cone of South America: New Clues from Mitogenomes

With analyses of entire mitogenomes, studies of Native American mitochondrial DNA (mtDNA) variation have entered the final phase of phylogenetic refinement: the dissection of the founding haplogroups into clades that arose in America during and after human arrival and spread. Ages and geographic distributions of these clades could provide novel clues on the colonization processes of the different regions of the double continent. As for the Southern Cone of South America, this approach has recently allowed the identification of two local clades (D1g and D1j) whose age estimates agree with the dating of the earliest archaeological sites in South America, indicating that Paleo-Indians might have reached that region from Beringia in less than 2000 years. In this study, we sequenced 46 mitogenomes belonging to two additional clades, termed B2i2 (former B2l) and C1b13, which were recently identified on the basis of mtDNA control-region data and whose geographical distributions appear to be restricted to Chile and Argentina. We confirm that their mutational motifs most likely arose in the Southern Cone region. However, the age estimate for B2i2 and C1b13 (11–13,000 years) appears to be younger than those of other local clades. The difference could reflect the different evolutionary origins of the distinct South American-specific sub-haplogroups, with some being already present, at different times and locations, at the very front of the expansion wave in South America, and others originating later in situ, when the tribalization process had already begun. A delayed origin of a few thousand years in one of the locally derived populations, possibly in the central part of Chile, would have limited the geographical and ethnic diffusion of B2i2 and explain the present-day occurrence that appears to be mainly confined to the Tehuelche and Araucanian-speaking groups.

Análisis de Adn Mitocondrial en Momias del Norte de Chile avala Hipótesis de Orígen Amazónico de Poblaciones Andinas

La hipotesis del origen amazonico de las poblaciones andinas basada en el analisis de marcadores geneticos nucleares es contrastada haciendo uso de ADN mitocondrial antiguo aislado de restos esqueletales de poblaciones prehistoricas del Valle de Azapa, Arica, Chile. Se analizaron 42 muestras de las cuales 32 rindieron amplificados para los cuatro marcadores amerindios permitiendo su tipificacion. La distribucion de haplogrupos (A: 31,2 %, B: 21,9 %, C: 31,2 %, D: 3,1 % y otros 12,5 %) relaciona geneticamente a las poblaciones estudiadas con grupos amazonicos y andinos actuales. El numero de muestras analizadas no permite aun una subdivision por fases cronologicas con el objeto de poner a prueba las hipotesis planteadas por arqueologos y bioantropologos para explicar la microevolucion biocultural de las poblaciones estudiadas

Origin and evolutionary relationships of native Andean populations.

This paper represents an effort to explore the origin and the evolutionary relationships of native Andean populations using a multidisciplinary approach. Archeological and linguistic evidence is briefly reviewed. A genetic distance analysis among major linguistic groupings and among Andean and Amazonian native populations, together with information obtained from archaeological and linguistic sources was used to generate a migration model. It is suggested that in the late Pleistocene a group of nomadic hunters entered South America through the Isthmus of Panama and split afterwards into two groups, one moving southward into the central and south Andean areas and after crossing the Colombian, Equador and Peruvian highlands to people northwestern Argentina, the open park country of east Brazil and the Argentine Pampas. The second group migrated eastwards into Venezuela and Guyana and later southward, peopling the Brazilian Amazon. Following available waterways the Amazonian Indians expanded east and west arriving probably at the eastern slopes of the Andes some 3,500 years ago. It is hypothesized that present day Andean natives are descendants of the Amazonian groups that migrated eastwards.

Craniofacial chronological microdifferentiation of human prehistoric populations of the Azapa valley, northern Chile

Los desarrollos culturales ocurridos en el altiplano en el area circumtiticaca en los Andes centrales, ejercieron influencia sobre las elaboraciones culturales de los grupos humanos que poblaban el Valle de Azapa cercano a la ciudad de Arica y la costa del norte de Chile. En esta comunicacion presentamos un analisis de distancias que demostro que una diferenciacion craniofacial acompano en el valle el proceso de evolucion cultural. La influencia biologica de Tiwanaku se refleja parcialmente en la morfologia craniofacial, proporcionando evidencia preliminar de que los cambios culturales en el valle se realizaron acompanados de flujo genico intermitente desde el altiplano, especialmente durante las fases Alto Ramirez y San Miguel

Morphometric and mtDNA analyses of archaic skeletal remains from southwestern South America

Durante decadas los antropologos han discutido como y cuando America fue poblada. El punto de vista predominante al respecto plantea que los primeros paleoindios, poblacion amerindia ancestral, llego en una epoca pre-Clovis desde Asia y Beringia utilizando como ruta la costa pacifica del continente. En el presente trabajo se analizan mediante morfometria geometrica y tecnicas de ADNmt antiguo restos esqueletales de 9.000-4.000 anos a.p., excavados de sitios arqueologicos del Norte, Centro y Sur de Chile. Nuestros resultados muestran que el material craneano arcaico del suroeste de America exhibe un amplio rango de variacion de la forma de la boveda, la cual es independiente de la cronologia de los craneos. El analisis del ADNmt realizado en los mismos restos esqueletales revela la presencia solo de los cuatro haplogrupos fundadores (A, B, C y D) desde los 9.000 a.p. Los resultados obtenidos a partir de datos morfometricos y de mtDNA muestran que, considerando los rasgos analizados, las poblaciones humanas que habitaron America durante la epoca arcaica no constituyen dos grupos diferentes. Estos resultados son consistentes con los analisis de secuencias completas de DNA mitocondrial recientemente obtenidos.

ANÁLISIS DE ADNmt DE RESTOS ESQUELETALES DEL SITIO ARQUEOLÓGICO DE TIWANAKU Y SU RELACIÓN CON EL ORIGEN DE SUS CONSTRUCTORES

Resumen es: Las hipotesis sobre el origen de las poblaciones que construyeron Tiwanaku basadas en informacion linguistica y etnohistorica son contrastadas haciendo ...