Abstract
Communities with increased shared ancestry represent invaluable tools for genetic studies of complex traits. ‘1001 Dalmatians’ research program collects biomedical information for genetic epidemiological research from multiple small isolated populations (‘metapopulation’) in the islands of Dalmatia, Croatia. Random samples of 100 individuals from 10 small island settlements (n<2000 inhabitants) were collected in 2002 and 2003. These island communities were carefully chosen to represent a wide range of distinct and well-documented demographic histories. Here, we analysed their genetic make-up using 26 short tandem repeat (STR) markers, at least 5 cM apart. We found a very high level of differentiation between most of these island communities based on Wright's fixation indexes, even within the same island. The model-based clustering algorithm, implemented in STRUCTURE, defined six clusters with very distinct genetic signatures, four of which corresponded to single villages. The extent of background LD, assessed with eight linked markers on Xq13-21, paralleled the extent of differentiation and was also very high in most of the populations under study. For each population, demographic history was characterised and 12 ‘demographic history’ variables were tentatively defined. Following stepwise regression, the demographic history variable that most significantly predicted the extent of LD was the proportion of locally born grandparents. Strong isolation and endogamy are likely to be the main forces maintaining this highly structured overall population.
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Acknowledgements
The authors are indebted to the study participants and to many students of the faculty of Medicine, University of Zagreb, local general practitioners and nurses, employees of the University of Rijeka and Split, the Croatian Institute of Public Health and the Institutes of Public Health in Split and Dubrovnik, for their help in the field work. We thank HGU MRC staff, Susan Fitzsimmons and Isla Campbell for help in genotyping, and Douglas Stuart for figure reproduction. We also thank Jim Wilson for critical reading of the manuscript. VV holds an MRC Special Training Fellowship in Bioinformatics. This work was supported by the British Scholarship Trust (IR and ZB), the University of Zagreb (‘Miroslav Cackoviç’ fellowship, ZB), Overseas Research Scheme (IR), the University of Edinburgh (scholarships, IR and OP), the Croatian Ministry of Science (Grant no 0108330 to IR), the British Council, the Wellcome Trust, the Royal Society (HC and IR), and the MRC.
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Vitart, V., Biloglav, Z., Hayward, C. et al. 3000 years of solitude: extreme differentiation in the island isolates of Dalmatia, Croatia. Eur J Hum Genet 14, 478–487 (2006). https://doi.org/10.1038/sj.ejhg.5201589
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DOI: https://doi.org/10.1038/sj.ejhg.5201589
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