Jana
08-07-2020, 01:37 PM
The PCA shows the presence of a genetic gradient within Estonia with the main differentiation observed between South-East and North-East of the country in agreement with previous studies [2, 11, 12]. This differentiation reflects a broader-scale South-North gradient in Eastern Europe (Fig. 1b) with Estonians from the North-East being closer to Finns while South-East Estonians projected closer to Latvians and Lithuanians.
IBD-based analysis (Fig. 2) reinforces previous observations [2, 11, 12] and our PCA results, namely the strong differentiation between South-East and the rest of Estonia, and provides a deeper insight into Estonian genetic structure, showing that most of the revealed clusters are highly geographically localized.
The results for the two length bins generally agree with each other, suggesting higher levels of gene flow in the North along with a barrier separating South-East Estonia (Supplementary text 2.4). A second barrier, separating the islands, especially Hiiumaa, from the mainland is also evident. This observation suggests that the population ancestral to modern South-East Estonians was partially isolated from the rest of the country at least since 50 generations ago. Interestingly, this genetic differentiation is consistent with linguistic data suggesting that the deepest split within the Finnic languages separates Southern Estonian from the other branches of the phylum that includes Northern Estonian
Admixture signals in Fig.3 show clear geographic pat-terns that match known historical evidence of external migration to Estonia, including Swedish settlements on the western coast and islands in fourteenth to fifteenth centuries and Finnish immigration to North-East Estonia in the seventeenth century [19]. In the latter case the genetic gradient in Estonia is consistent with the broader European trend (Fig.1b) and thus higher affinity of North-East Estonians to Finns is likely to have a more complex origin....These results suggest that admixture with non-Estonian groups can only partially explain the fine genetic structure observed in Fig. 2.
We ran IBDNe [15] on the four most distinct clusters from Fig. 4a, representing four regions of Estonia: North-West, North-East, South-West and South-East and observed rather distinct Ne trajectories (Fig. 4c, Supplementary text 4.2). In particular, all clusters (except for eSE_5) show evidence of an effective population size decline between 10 and 20 generations ago, which is not detected when the entire dataset is analyzed
South-West and North West Estonia are characterized by an overall high level of gene flow (Supplementary text 2.4), leading to similar Ne trajectories that deviate only during the last 20 generations (Fig. 4c, Supplementary text 4.2). This also brings about the idea that the strong bottleneck in South-West could contribute to the observed population structure, in particular leading to differentiation of South-West and its subgroups. On the other hand, South-East Estonia has the most distinct Ne trajectory according to Fig. 4c, having a substantially lower long-term Ne compared to other regions.
All the analyses performed so far speak for South-East Estonia showing relatively strong genetic differentiation from the rest of the country and having a partially independent demographic history...thus indicating a suggestive instance of polygenic selection specific to South-East Estonia. To conclude, here we show evidence of potential very recent and geographically localized selection providing an important case for our understanding of ongoing natural selection in humans.
Here we describe a dataset of more than 2300 high coverage Estonian genomes making it one of the smallest populations to date with such high-resolution data available. We show that the Estonian population, despite occupying a small area with no strong geographic barriers, is genetically structured and exhibits rather pronounced inter regional differences with respect to recent admixture with neighbouring groups, population dynamics and potential action of natural selection.
Link to paper: https://www.nature.com/articles/s41431-020-0699-4.epdf?sharing_token=O-fipjjPqnEtyR7yadlPctRgN0jAjWel9jnR3ZoTv0OIN6ZnOkUj TZGn8IWjCBW_YEC4Iprryqd2KEzHN63TyUOdtfcpp8ho1270BW HfkYiOPW8q3uq3PIQuxtmcv-IjN70DYO47F2vbnPR9js7pI4f4iNQB2qPMtcfOtlmmfyI%3D
IBD-based analysis (Fig. 2) reinforces previous observations [2, 11, 12] and our PCA results, namely the strong differentiation between South-East and the rest of Estonia, and provides a deeper insight into Estonian genetic structure, showing that most of the revealed clusters are highly geographically localized.
The results for the two length bins generally agree with each other, suggesting higher levels of gene flow in the North along with a barrier separating South-East Estonia (Supplementary text 2.4). A second barrier, separating the islands, especially Hiiumaa, from the mainland is also evident. This observation suggests that the population ancestral to modern South-East Estonians was partially isolated from the rest of the country at least since 50 generations ago. Interestingly, this genetic differentiation is consistent with linguistic data suggesting that the deepest split within the Finnic languages separates Southern Estonian from the other branches of the phylum that includes Northern Estonian
Admixture signals in Fig.3 show clear geographic pat-terns that match known historical evidence of external migration to Estonia, including Swedish settlements on the western coast and islands in fourteenth to fifteenth centuries and Finnish immigration to North-East Estonia in the seventeenth century [19]. In the latter case the genetic gradient in Estonia is consistent with the broader European trend (Fig.1b) and thus higher affinity of North-East Estonians to Finns is likely to have a more complex origin....These results suggest that admixture with non-Estonian groups can only partially explain the fine genetic structure observed in Fig. 2.
We ran IBDNe [15] on the four most distinct clusters from Fig. 4a, representing four regions of Estonia: North-West, North-East, South-West and South-East and observed rather distinct Ne trajectories (Fig. 4c, Supplementary text 4.2). In particular, all clusters (except for eSE_5) show evidence of an effective population size decline between 10 and 20 generations ago, which is not detected when the entire dataset is analyzed
South-West and North West Estonia are characterized by an overall high level of gene flow (Supplementary text 2.4), leading to similar Ne trajectories that deviate only during the last 20 generations (Fig. 4c, Supplementary text 4.2). This also brings about the idea that the strong bottleneck in South-West could contribute to the observed population structure, in particular leading to differentiation of South-West and its subgroups. On the other hand, South-East Estonia has the most distinct Ne trajectory according to Fig. 4c, having a substantially lower long-term Ne compared to other regions.
All the analyses performed so far speak for South-East Estonia showing relatively strong genetic differentiation from the rest of the country and having a partially independent demographic history...thus indicating a suggestive instance of polygenic selection specific to South-East Estonia. To conclude, here we show evidence of potential very recent and geographically localized selection providing an important case for our understanding of ongoing natural selection in humans.
Here we describe a dataset of more than 2300 high coverage Estonian genomes making it one of the smallest populations to date with such high-resolution data available. We show that the Estonian population, despite occupying a small area with no strong geographic barriers, is genetically structured and exhibits rather pronounced inter regional differences with respect to recent admixture with neighbouring groups, population dynamics and potential action of natural selection.
Link to paper: https://www.nature.com/articles/s41431-020-0699-4.epdf?sharing_token=O-fipjjPqnEtyR7yadlPctRgN0jAjWel9jnR3ZoTv0OIN6ZnOkUj TZGn8IWjCBW_YEC4Iprryqd2KEzHN63TyUOdtfcpp8ho1270BW HfkYiOPW8q3uq3PIQuxtmcv-IjN70DYO47F2vbnPR9js7pI4f4iNQB2qPMtcfOtlmmfyI%3D