Distribution of mtDNA haplogroup X among Native North Americans

Mitochondrial DNA (mtDNA) samples of 70 Native Americans, most of whom had been found not to belong to any of the four common Native American haplogro ups (A, B, C, and D), were analyzed for the presence of Dde I site losses a t np 1715 and np 10394. These two mutations are characteristic of haplogrou p X which might be of European origin. The first hypervariable segment (HVS I) of the non-coding control region (CR) of mtDNA of a representative selec tion of samples exhibiting these mutations was sequenced to confirm their a ssignment to haplogroup X, Thirty-two of the samples exhibited the restrict ion site losses characteristic of haplogroup X and, when sequenced, a repre sentative selection (n = 11) of these exhibited the CR mutations commonly a ssociated with haplogroup X, C --> T transitions at np 16278 and 16223, in addition to as many as three other HVSI mutations. The wide distribution of this haplogroup throughout North America, and its prehistoric presence the re, are consistent with its being a fifth founding haplogroup exhibited by about 3% of modern Native Americans. Its markedly nonrandom distribution wi th high frequency in certain regions, as for the other four major mtDNA hap logroups, should facilitate establishing ancestor/descendant relationships between modern and prehistoric groups of Native Americans. The low frequenc y of haplogroups other than A, B, C, D, and X among the samples studied sug gests a paucity of both recent non-Native American maternal admixture in al leged fullblood Native Americans and mutations at the restriction sites tha t characterize the five haplogroups as well as the absence of additional (u ndiscovered) founding haplogroups. (C) 1999 Wiley-Liss, Inc.