Genetic Chaos

Monday, May 01, 2006

Y Chromosome and Mitochondrial DNA Variation in Lithuanians

The genetic composition of the Lithuanian population was investigated by analysing mitochondrial DNA hypervariable region 1, RFLP polymorphisms and Y chromosomal biallelic and STR markers in six ethnolinguistic groups of Lithuanians, to address questions about the origin and genetic structure of the present day population. There were no significant genetic differences among ethnolinguistic groups, and an analysis of molecular variance confirmed the homogeneity of the Lithuanian population. MtDNA diversity revealed that Lithuanians are close to both Slavic (Indo-European) and Finno-Ugric speaking populations of Northern and Eastern Europe. Y-chromosome SNP haplogroup analysis showed Lithuanians to be closest to Latvians and Estonians. Significant differences between Lithuanian and Estonian Y chromosome STR haplotypes suggested that these populations have had different demographic histories. We suggest that the observed pattern of Y chromosome diversity in Lithuanians may be explained by a population bottleneck associated with Indo-European contact. Different Y chromosome STR distributions in Lithuanians and Estonians might be explained by different origins or, alternatively, be the result of some period of isolation and genetic drift after the population split.

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Mitochondrial DNA Sequence Analysis in the Lithuanian Population

Analysis of mitochondrial DNA (mtDNA) diversity has proved to be a useful tool in our understanding of the origin and history of human populations and also provided insights into the pathophysiology of mitochondrial disease. In order to investigate the genetic composition of the Lithuanian population, we have analysed mtDNA variation in 180 individuals from six Lithuanian ethnolinguistic subgroups. The sequencing of the first hypervariable segment (HV1) in the control region of the mtDNA and restriction fragment length polymorphism typing allowed us to classify mtDNA molecules to previously described haplogroups. This analysis revealed the presence of all major European mtDNA haplogroups (H, V, U, K, J, T, I, W, X) in the Lithuanian sample. Haplogroup H was the most common in Lithuanians, comprising 46% of all sequences. The frequencies of the rest haplogroups ranged from 1% to 20%. No significant differences, which could indicate influence of different Baltic tribes, were detected among ethnolinguistic subgroups of Lithuanians. The analysis of molecular variance (AMOVA) further confirmed the absence of internal genetic structuring in the Lithuanian population. Comparisons with other European populations demonstrated that the Lithuanian mtDNA gene pool is more closely related to the mtDNA gene pool of Northern European populations, while molecular diversity indices (gene diversity 0.971 ± 0.008, nucleotide diversity 0.012 ± 0.007 and the mean number of pairwise differences between sequences 4.41 ± 2.19) indicate that the Lithuanians are among the more diverse populations in Europe.

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The Balts and the Finns in historical perspective: a multidisciplinary approach

Introduction. Ethnic history of human populations is a too complicated phenomenon to elucidate it on the basis of several gene frequencies. It is obligatory to compile all data on molecular genetics and serology, to add new ones, to request services of paleopopulation comparisons, facts of anthropological odontology, craniology, and anthropology of the modern population of the area as well as linguistic and archaeological information. A multidisciplinary approach to elucidating historical relations between the Balts and the Finns is the goal of the present report. Materials and methods. Approx. 800 blood samples from Lithuania were examined in order to investigate Lithuanian population according to different genetic markers. Discrete cranial traits of 6,426 skulls from Lithuania and adjacent territories as well as 3,734 skulls belonging to the Neolithic, Bronze Age, 2,000 YBP and 1,000 YBP were investigated. We disposed of data on the ethnic odontology of 4,993 modern Lithuanians as well as of 1446 skulls dated to 2,000 YBP and 1,000 YBP. Results. Two separate clusters consisting consequently of four Baltic and two Finnish groups emerged in the dendrogram (Fig. 1).The mesocranial Mesolithic population in Lithuania might be related to the Middle-European kernel of mesocranes. The Middle-European orientation of the Neolithic and Bronze Age Lithuanian population is evident. The influx from the eastern part of the ancient Baltic area was detected in the 2,000 YBP population. The Lithuanian 1,000 YBP population was more homogeneous than the inhabitants of Latvia (Fig. 2). The Y chromosome haplogroups 1 and 9 show complementary clines from southeast to northwest of Europe, the Baltic peoples (Latvians and Lithuanians) demonstrating a mixture of western and eastern genetic traits (Fig. 3). In Northern Europe, strong geographical, linguistic and cultural barriers can be identified. Three main migration directions could have a real influence on the formation of the Lithuanian gene pool. Conclusions. Anthropological, archaeological and linguistic data demonstrate that there was no common ancestry of the Balts and the Finns. Genetic and phenetical similarities might occur due to gene exchange between adjacent populations on the northern and eastern borderlines of the ancient Baltic area that took place from the Mesolithic time. It is impossible to date the emergence of some genetic and anthropological similarities between the Balts and the Finns.

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Regional differences among the Finns: A Y-chromosomal perspective

Twenty-two Y-chromosomal markers, consisting of fourteen biallelic markers (YAP/DYS287, M170, M253, P37, M223, 12f2, M9, P43, Tat, 92R7, P36, SRY-1532, M17, P25) and eight STRs (DYS19, DYS385a/b, DYS388, DYS389I/II, DYS390, DYS391, DYS392, DYS393), were analyzed in 536 unrelated Finnish males from eastern and western subpopulations of Finland. The aim of the study was to analyze regional differences in genetic variation within the country, and to analyze the population history of the Finns. Our results gave further support to the existence of a sharp genetic border between eastern and western Finns so far observed exclusively in Y-chromosomal variation. Both biallelic haplogroup and STR haplotype networks showed bifurcated structures, and similar clustering was evident in haplogroup and haplotype frequencies and genetic distances. These results suggest that the western and eastern parts of the country have been subject to partly different population histories, which is also supported by earlier archaeological, historical and genetic data. It seems probable that early migrations from Finno-Ugric sources affected the whole country, whereas subsequent migrations from Scandinavia had an impact mainly on the western parts of the country. The contacts between Finland and neighboring Finno-Ugric, Scandinavian and Baltic regions are evident. However, there is no support for recent migrations from Siberia and Central Europe. Our results emphasize the importance of incorporating Y-chromosomal data to reveal the population substructure which is often left undetected in mitochondrial DNA variation. Early assumptions of the homogeneity of the isolated Finnish population have now proven to be false, which may also have implications for future association studies.

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