title: Young Alu insertions within the MHC class I region in native American populations: insights into the origin of the MHC-Alu repeats.
abstract: OBJECTIVE
  Genetic heterogeneity of two Amerindian populations (Jujuy province, Argentina, and Waorani tribe, Ecuador) was characterized by analyzing data on polymorphic Alu insertions within the human major histocompatibility complex (MHC) class I region (6p21.31), which are completely nonexistent in Native Americans. We further evaluated the haplotype distribution and genetic diversity among continental ancestry groups and their potential implications for the dating of the origin of MHC-Alus.
  
  
  METHODS
  Five MHC-Alu elements (AluMicB, AluTF, AluHJ, AluHG, and AluHF) were typed in samples from Jujuy (N = 108) and Waorani (N = 36). Allele and haplotype frequency data on worldwide populations were compiled to explore spatial structuring of the MHC-Alu diversity through AMOVA tests. We utilized the median-joining network approach to illustrate the continental distribution of the MHC-Alu haplotypes and their phylogenetic relationships.
  
  
  RESULTS
  Allele and haplotype distributions differed significantly between Jujuy and Waorani. The Waorani featured a low average heterozygosity attributable to strong population isolation. Overall, Alu markers showed great genetic heterogeneity both within and among populations. The haplotype distribution was distinctive of each continental ancestry group. Contrary to expectations, Africans showed the lowest MHC-Alu diversity.
  
  
  CONCLUSIONS
  Genetic drift mainly associated to population bottlenecks seems to be reflected in the low MHC-Alu diversity of the Amerindians, mainly in Waorani. Geographical structuring of the haplotype distribution supports the efficiency of the MHC-Alu loci as lineage (ancestry) markers. The markedly low Alu diversity of African populations relative to other continental clusters suggests that these MHC-Alus might have arisen after the anatomically modern humans expanded out of Africa.
authors.affiliation: Departamento de Genética y Antropología Física, Facultad de Ciencia y Tecnología, Universidad del País Vasco (UPV/EHU), Bilbao, Spain.
authors.forename: Luis
authors.initials: L
authors.lastname: Gómez-Pérez
authors.forename: Miguel A
authors.initials: MA
authors.lastname: Alfonso-Sánchez
authors.forename: José E
authors.initials: JE
authors.lastname: Dipierri
authors.forename: Dora
authors.initials: D
authors.lastname: Sánchez
authors.forename: Ibone
authors.initials: I
authors.lastname: Espinosa
authors.forename: Marian M
authors.initials: MM
authors.lastname: De Pancorbo
authors.forename: José A
authors.initials: JA
authors.lastname: Peña
mesh_terms: D020087:Alu Elements / Q000235:genetics*; D001118:Argentina; D004484:Ecuador; D005787:Gene Frequency; D005805:Genes, MHC Class I / Q000235:genetics*; D040961:Genetic Drift; D014644:Genetic Variation / Q000235:genetics; D005828:Genetics, Population; D006239:Haplotypes; D006801:Humans; D007199:Indians, South American / Q000235:genetics*