De Novo Mutations in Y-Chromosome STR Loci Revealed in Paternal Lineages of Siberian Tundra Nentsi Population

摘要

Y-chromosome short tandem repeats (STR) markers are widely used in human population genetic studies and forensic applications. Estimation of Y-STR mutation rate has a key role for dating the origin of Y chromosome lineages and for paternity tests. Previous studies demonstrated significant interlocus difference in mutation rate and the positive correlation to STR repeat length. The different ethnic groups and various Y-chromosome haplogroups defined by single-nucleotide polymorphisms were characterized by different Y-STR mutation rates. To date no Y-STR pedigree mutation studies were reported in native Siberian populations. Siberian Tundra Nentsi population possesses many unique genetic features and represents a good model for genealogical studies because of large family sizes, available ancestry information and relatively isolated life style in the extreme north environment. We thoroughly selected 50 paternal lineages with deep genealogical depth from 2 to 6 generations with the total number of 330 males. The number of descendants varied from 2 to 25 per paternal lineage, in average seven males per lineage. We also included in our analysis six Komi, three Russian and one Khant families who lived in the same villages. Totally 34 STR loci from non-recombining part of Y-chromosome were studied: DYS 19, DYS390, DYS391, DYS393, DYS385A, DYS385B, DYS426, DYS388, DYS392, DYS439, DYS389-1, DYS389-2, DYS458, DYS447, DYS449, DYS459, DYS454, DYS464, DYS455, DYS457, DYS448, H4, DYS607, CDY-1, CDY-2, DYS460, YCA-1, YCA-2, DYS576, DYS570, DYS438, DYS456, DYS442, and C4. Eleven males (4%) had different alleles in six or seven STR loci compared to their paternal ancestors. We believe that those men were born out-of-wedlock or were adopted. Traditionally native Siberian people adopt and raise all children who lost their parents. Mutations were observed in 21 out of 34 Y-STR loci. We found relatively higher number of mutation gains (60%) versus losses. Our study has thus shown that the chosen Y-STR loci represent a powerful tool to estimate mutation rates for forensic and population genetic purposes.