title: Human adaptation to arsenic in Andean populations of the Atacama Desert.
abstract: Quebrada Camarones, in the Atacama Desert, has the highest arsenic levels in the Americas (>1,000 µg/L). However, the Camarones people have subsisted in this adverse environment during the last 7,000 years and have not presented any epidemiological emergencies. Therefore, to solve this conundrum we compared the frequencies of four protective genetic variants of the AS3MT gene associated with efficient arsenic metabolization, between the living populations of Camarones and two other populations historically exposed to lower levels of arsenic.
  
  
  
  The Chilean selected population samples come from Quebrada Camarones (n = 50) and the Azapa Valley (n = 47) in the north and San Juan de la Costa (n = 45) in southern Chile. The genotyping was conducted using PCR-RFLP. We compared the genotypic and allelic frequencies, and estimated the haplotype frequencies in the AS3MT gene.
  
  
  
  We found higher frequencies of the protective variants in those people from Camarones than in the other two populations. The haplotype estimation showed that the combination of protective variants of CTTA is very frequent in Camarones (68%) and Azapa (48%), but extremely low in San Juan de la Costa (8%). Also, the C variant associated with toxicity risks in the SNP Met287Thr had a lower frequency in Camarones (1%) and is higher in the other populations.
  
  
  
  The higher frequency of protective variants in both northern Chilean populations indicates a long exposure to naturally arsenic-contaminated water sources. Our data suggest that a high arsenic metabolization capacity has been selected as an adaptive mechanism in these populations in order to survive in an arsenic-laden environment.
authors.affiliation: Programa de Genética Humana, ICBM, Facultad de Medicina, Universidad de Chile, Santiago, Chile.
authors.forename: Mario
authors.initials: M
authors.lastname: Apata
authors.affiliation: Instituto de Alta Investigación, Universidad de Tarapacá, Arica, Chile.
authors.forename: Bernado
authors.initials: B
authors.lastname: Arriaza
authors.affiliation: Programa de Genética Humana, ICBM, Facultad de Medicina, Universidad de Chile, Santiago, Chile.
authors.forename: Elena
authors.initials: E
authors.lastname: Llop
authors.affiliation: Programa de Genética Humana, ICBM, Facultad de Medicina, Universidad de Chile, Santiago, Chile.|Departamento de Antropología, Facultad de Ciencias Sociales, Universidad de Chile, Santiago, Chile.
authors.forename: Mauricio
authors.identifier: 0000-0002-8217-9950
authors.initials: M
authors.lastname: Moraga
mesh_terms: D000220:Adaptation, Biological / Q000235:genetics*; D000328:Adult; D000885:Anthropology, Physical; D001151:Arsenic; D002677:Chile; D003430:Cross-Sectional Studies; D005260:Female; D005787:Gene Frequency / Q000235:genetics*; D006239:Haplotypes / Q000235:genetics*; D006801:Humans; D007199:Indians, South American / Q000208:ethnology / Q000235:genetics*; D008297:Male; D008780:Methyltransferases / Q000235:genetics; D008875:Middle Aged; D012641:Selection, Genetic / Q000235:genetics
chemical_list: D008780:Methyltransferases; C505756:AS3MT protein, human; D001151:Arsenic
keywords: AS3MT gene; Quebrada Camarones; natural selection; protective haplotype