The Western and Eastern Roots of the Saami—the Story of Genetic “Outliers” Told by Mitochondrial DNA and Y Chromosomes

Abstract

The Saami are regarded as extreme genetic outliers among European populations. In this study, a high-resolution phylogenetic analysis of Saami genetic heritage was undertaken in a comprehensive context, through use of maternally inherited mitochondrial DNA (mtDNA) and paternally inherited Y-chromosomal variation. DNA variants present in the Saami were compared with those found in Europe and Siberia, through use of both new and previously published data from 445 Saami and 17,096 western Eurasian and Siberian mtDNA samples, as well as 127 Saami and 2,840 western Eurasian and Siberian Y-chromosome samples. It was shown that the "Saami motif" variant of mtDNA haplogroup U5b is present in a large area outside Scandinavia. A detailed phylogeographic analysis of one of the predominant Saami mtDNA haplogroups, U5b1b, which also includes the lineages of the "Saami motif," was undertaken in 31 populations. The results indicate that the origin of U5b1b, as for the other predominant Saami haplogroup, V, is most likely in western, rather than eastern, Europe. Furthermore, an additional haplogroup (H1) spread among the Saami was virtually absent in 781 Samoyed and Ob-Ugric Siberians but was present in western and central European populations. The Y-chromosomal variety in the Saami is also consistent with their European ancestry. It suggests that the large genetic separation of the Saami from other Europeans is best explained by assuming that the Saami are descendants of a narrow, distinctive subset of Europeans. In particular, no evidence of a significant directional gene flow from extant aboriginal Siberian populations into the haploid gene pools of the Saami was found.

Small effective population size and genetic homogeneity in the Val Borbera isolate

“…In contrast with nuclear estimates, there is higher variance among villages. The lowest mtN e is found in CAR, where mtN e is slightly above 2000, about three times smaller than Saami (a traditional isolated group 16 ). The second feature revealed by the EBSP analysis is a constant demography for villages, again in accordance with nuclear estimates.…”

“…Finally, we also included published mtDNA controlregion data from the Saami, a northern population known to be a genetic outlier among Europeans. 16 …”

A genome-wide association study for age-related hearing impairment in the Saami

“…14 Several genetic studies have been conducted to shed light on the genetic origin of the Saami. [15][16][17][18] These studies suggested that the Saami are descendants of Europeans who, several thousand years ago, reached northern Fennoscandia from both a western and an eastern route and subsequently got admixed. They also found a small East Asian contribution to the gene pool.…”

“…They also found a small East Asian contribution to the gene pool. 18,19 Several genetic studies have further suggested that the extent of linkage disequilibrium (LD) in the Saami is dramatically higher compared to that of outbred populations. [20][21][22][23] Higher levels of LD are observed in other population isolates as well.…”

Mitochondrial genes and schizophrenia

“…This mutation, previously observed by Thomas et al (1996) was found to be in connection with A12308G (a marker for mtDNA haplogroup U), T3197C (a marker for haplogroup U5), and T5814C (which was associated with mitochondrial encephalopathy; Manfredi et al, 1996) in a patient with limb myopathy (Sternberg et al, 1998). Indeed, it is now well known that a transition at position 5656 (which is located as a non-coding spacer between the tRNA Ala and tRNA Asn genes) is characteristic of a sub-haplogroup (now referred to as U5b1; Tambets et al, 2004) of the European haplogroup U5b (Finnilä et al, 1999(Finnilä et al, , 2001Herrnstadt et al, 2002). Phylogenetic information is thus a useful guide to the evaluation of pathogeneity of a particular mutation, especially since the database of complete mtDNA sequences is rapidly growing; e.g.…”