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Kivisild T, Saag L, Hui R, Biagini SA, Pankratov V, D'Atanasio E, Pagani L, Saag L, Rootsi S, Mägi R, Metspalu E, Valk H, Malve M, Irdt K, Reisberg T, Solnik A, Scheib CL, Seidman DN, Williams AL, Tambets K, Metspalu M. Patterns of genetic connectedness between modern and medieval Estonian genomes reveal the origins of a major ancestry component of the Finnish population. Am J Hum Genet 2021; 108:1792-1806. [PMID: 34411538 DOI: 10.1016/j.ajhg.2021.07.012] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2021] [Accepted: 07/23/2021] [Indexed: 11/20/2022] Open
Abstract
The Finnish population is a unique example of a genetic isolate affected by a recent founder event. Previous studies have suggested that the ancestors of Finnic-speaking Finns and Estonians reached the circum-Baltic region by the 1st millennium BC. However, high linguistic similarity points to a more recent split of their languages. To study genetic connectedness between Finns and Estonians directly, we first assessed the efficacy of imputation of low-coverage ancient genomes by sequencing a medieval Estonian genome to high depth (23×) and evaluated the performance of its down-sampled replicas. We find that ancient genomes imputed from >0.1× coverage can be reliably used in principal-component analyses without projection. By searching for long shared allele intervals (LSAIs; similar to identity-by-descent segments) in unphased data for >143,000 present-day Estonians, 99 Finns, and 14 imputed ancient genomes from Estonia, we find unexpectedly high levels of individual connectedness between Estonians and Finns for the last eight centuries in contrast to their clear differentiation by allele frequencies. High levels of sharing of these segments between Estonians and Finns predate the demographic expansion and late settlement process of Finland. One plausible source of this extensive sharing is the 8th-10th centuries AD migration event from North Estonia to Finland that has been proposed to explain uniquely shared linguistic features between the Finnish language and the northern dialect of Estonian and shared Christianity-related loanwords from Slavic. These results suggest that LSAI detection provides a computationally tractable way to detect fine-scale structure in large cohorts.
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Affiliation(s)
- Toomas Kivisild
- Department of Human Genetics, KU Leuven, Leuven 3000, Belgium; Estonian Biocentre, Institute of Genomics, University of Tartu, Tartu 51010, Estonia; McDonald Institute for Archaeological Research, University of Cambridge, Cambridge CB2 3ER, UK.
| | - Lehti Saag
- Estonian Biocentre, Institute of Genomics, University of Tartu, Tartu 51010, Estonia; Research Department of Genetics, Evolution, and Environment, University College London, London WC1E 6BT, UK
| | - Ruoyun Hui
- McDonald Institute for Archaeological Research, University of Cambridge, Cambridge CB2 3ER, UK; The Alan Turing Institute, British Library, 96 Euston Road, London NW1 2DB, UK
| | | | - Vasili Pankratov
- Estonian Biocentre, Institute of Genomics, University of Tartu, Tartu 51010, Estonia
| | - Eugenia D'Atanasio
- Instituto di Biologia e Patologia Molecolari, Consiglio Nazionale delle Ricerche, Rome, Italy
| | - Luca Pagani
- Estonian Biocentre, Institute of Genomics, University of Tartu, Tartu 51010, Estonia; Department of Biology, University of Padova, 35131 Padova, Italy
| | - Lauri Saag
- Estonian Biocentre, Institute of Genomics, University of Tartu, Tartu 51010, Estonia
| | - Siiri Rootsi
- Estonian Biocentre, Institute of Genomics, University of Tartu, Tartu 51010, Estonia
| | - Reedik Mägi
- Estonian Biocentre, Institute of Genomics, University of Tartu, Tartu 51010, Estonia
| | - Ene Metspalu
- Estonian Biocentre, Institute of Genomics, University of Tartu, Tartu 51010, Estonia
| | - Heiki Valk
- Department of Archaeology, Institute of History and Archaeology, University of Tartu, Tartu 51014, Estonia
| | - Martin Malve
- Department of Archaeology, Institute of History and Archaeology, University of Tartu, Tartu 51014, Estonia
| | - Kadri Irdt
- Estonian Biocentre, Institute of Genomics, University of Tartu, Tartu 51010, Estonia
| | - Tuuli Reisberg
- Core Facility, Institute of Genomics, University of Tartu, Tartu 51010, Estonia
| | - Anu Solnik
- Core Facility, Institute of Genomics, University of Tartu, Tartu 51010, Estonia
| | - Christiana L Scheib
- Estonian Biocentre, Institute of Genomics, University of Tartu, Tartu 51010, Estonia; McDonald Institute for Archaeological Research, University of Cambridge, Cambridge CB2 3ER, UK; St John's College, University of Cambridge, Cambridge CB2 1TP, UK
| | - Daniel N Seidman
- Department of Computational Biology, Cornell University, Ithaca, NY 14853, USA
| | - Amy L Williams
- Department of Computational Biology, Cornell University, Ithaca, NY 14853, USA
| | - Kristiina Tambets
- Estonian Biocentre, Institute of Genomics, University of Tartu, Tartu 51010, Estonia
| | - Mait Metspalu
- Estonian Biocentre, Institute of Genomics, University of Tartu, Tartu 51010, Estonia
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