title: mtDNA haplogroup X: An ancient link between Europe/Western Asia and North America?
abstract: On the basis of comprehensive RFLP analysis, it has been inferred that approximately 97% of Native American mtDNAs belong to one of four major founding mtDNA lineages, designated haplogroups "A"-"D." It has been proposed that a fifth mtDNA haplogroup (haplogroup X) represents a minor founding lineage in Native Americans. Unlike haplogroups A-D, haplogroup X is also found at low frequencies in modern European populations. To investigate the origins, diversity, and continental relationships of this haplogroup, we performed mtDNA high-resolution RFLP and complete control region (CR) sequence analysis on 22 putative Native American haplogroup X and 14 putative European haplogroup X mtDNAs. The results identified a consensus haplogroup X motif that characterizes our European and Native American samples. Among Native Americans, haplogroup X appears to be essentially restricted to northern Amerindian groups, including the Ojibwa, the Nuu-Chah-Nulth, the Sioux, and the Yakima, although we also observed this haplogroup in the Na-Dene-speaking Navajo. Median network analysis indicated that European and Native American haplogroup X mtDNAs, although distinct, nevertheless are distantly related to each other. Time estimates for the arrival of X in North America are 12,000-36,000 years ago, depending on the number of assumed founders, thus supporting the conclusion that the peoples harboring haplogroup X were among the original founders of Native American populations. To date, haplogroup X has not been unambiguously identified in Asia, raising the possibility that some Native American founders were of Caucasian ancestry.
authors.affiliation: Center for Molecular Medicine, Emory University School of Medicine, Atlanta, GA, USA. mdbrown@gmm.gen.emory.edu
authors.forename: M D
authors.initials: MD
authors.lastname: Brown
authors.forename: S H
authors.initials: SH
authors.lastname: Hosseini
authors.forename: A
authors.initials: A
authors.lastname: Torroni
authors.forename: H J
authors.initials: HJ
authors.lastname: Bandelt
authors.forename: J C
authors.initials: JC
authors.lastname: Allen
authors.forename: T G
authors.initials: TG
authors.lastname: Schurr
authors.forename: R
authors.initials: R
authors.lastname: Scozzari
authors.forename: F
authors.initials: F
authors.lastname: Cruciani
authors.forename: D C
authors.initials: DC
authors.lastname: Wallace
mesh_terms: D001211:Asia, Western / Q000208:ethnology; D044466:Asian People / Q000235:genetics*; D001483:Base Sequence; D016384:Consensus Sequence; D004272:DNA, Mitochondrial / Q000235:genetics*; D005060:Europe / Q000208:ethnology; D005787:Gene Frequency; D006239:Haplotypes / Q000235:genetics*; D006801:Humans; D007198:Indians, North American / Q000145:classification / Q000235:genetics*; D019901:Locus Control Region / Q000235:genetics; D009656:North America; D010802:Phylogeny; D012150:Polymorphism, Restriction Fragment Length; D017422:Sequence Analysis, DNA; D044465:White People / Q000145:classification / Q000235:genetics*
chemical_list: D004272:DNA, Mitochondrial