Autosomal and uniparental portraits of the native populations of Sakha (Yakutia): implications for the peopling of Northeast Eurasia

BACKGROUND

Sakha--an area connecting South and Northeast Siberia--is significant for understanding the history of peopling of Northeast Eurasia and the Americas. Previous studies have shown a genetic contiguity between Siberia and East Asia and the key role of South Siberia in the colonization of Siberia.

RESULTS

We report the results of a high-resolution phylogenetic analysis of 701 mtDNAs and 318 Y chromosomes from five native populations of Sakha (Yakuts, Evenks, Evens, Yukaghirs and Dolgans) and of the analysis of more than 500,000 autosomal SNPs of 758 individuals from 55 populations, including 40 previously unpublished samples from Siberia. Phylogenetically terminal clades of East Asian mtDNA haplogroups C and D and Y-chromosome haplogroups N1c, N1b and C3, constituting the core of the gene pool of the native populations from Sakha, connect Sakha and South Siberia. Analysis of autosomal SNP data confirms the genetic continuity between Sakha and South Siberia. Maternal lineages D5a2a2, C4a1c, C4a2, C5b1b and the Yakut-specific STR sub-clade of Y-chromosome haplogroup N1c can be linked to a migration of Yakut ancestors, while the paternal lineage C3c was most likely carried to Sakha by the expansion of the Tungusic people. MtDNA haplogroups Z1a1b and Z1a3, present in Yukaghirs, Evens and Dolgans, show traces of different and probably more ancient migration(s). Analysis of both haploid loci and autosomal SNP data revealed only minor genetic components shared between Sakha and the extreme Northeast Siberia. Although the major part of West Eurasian maternal and paternal lineages in Sakha could originate from recent admixture with East Europeans, mtDNA haplogroups H8, H20a and HV1a1a, as well as Y-chromosome haplogroup J, more probably reflect an ancient gene flow from West Eurasia through Central Asia and South Siberia.

CONCLUSIONS

Our high-resolution phylogenetic dissection of mtDNA and Y-chromosome haplogroups as well as analysis of autosomal SNP data suggests that Sakha was colonized by repeated expansions from South Siberia with minor gene flow from the Lower Amur/Southern Okhotsk region and/or Kamchatka. The minor West Eurasian component in Sakha attests to both recent and ongoing admixture with East Europeans and an ancient gene flow from West Eurasia.

Variants in scavenger receptor class B type I gene are associated with HDL cholesterol levels in younger women

OBJECTIVE

Variants within the scavenger receptor class B type I (SCARB1) receptor gene have been previously associated with lipid levels, especially in women, with some studies reporting the association to be stronger in the presence of diabetes or post-menopausal estrogen use. Based on the reported gender-specific association and modification effect of estrogen on lipid levels according to SCARB1 variants, we explored the relationship between SCARBI single nucleotide polymorphisms (SNPs) and lipid levels in an Amish population to assess sex and age differences.

METHODS

Eight SCARB1 SNPs, identified from public databases, were genotyped in 919 subjects.

RESULTS

Rs5888 and rs3782287 were in high linkage disequilibrium (LD), with r(2) > 0.8. None of the SNPs were significantly associated with lipid levels in men; however in women, rs5888 (p = 0.04) and rs5891 (p < 0.001) were significantly associated with higher HDL-C levels. Rs5891 had an allele frequency of 3% and predicts a missense mutation (Ile135Val), which may be functional. Moreover, rs3782287 (p = 0.023) and rs5888 (p = 0.003) were significantly associated with higher HDL-C levels in women younger than 50 years but not in women aged 50 years or older (p for interaction between age and rs5888 = 0.045). None of the SNP effects on HDL-C were modified in the presence of diabetes, in either men or women.

CONCLUSIONS

SCARB1 SNPs influence HDL-C levels in women, particularly in those less than 50 years old.

CONDENSED ABSTRACT

We assessed associations between SCARB1 SNPs and lipid traits in 919 Amish men and women. Two SNPs, rs3782287 and rs5888, were significantly associated with higher HDL-C levels in women younger than 50 years but not in women aged 50 years or older, supporting an interaction between common sequence variants in SCARB1 and estrogen on HDL-C.