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Consanguinity around the world: what do the genomic data of the HGDP-CEPH diversity panel tell us?

ABSTRACT: Inbreeding coefficients and consanguineous mating types are usually inferred from population surveys or pedigree studies. Here, we present a method to estimate them from dense genome-wide single-nucleotide polymorphism genotypes and apply it to 940 unrelated individuals from the Human Genome Diversity Panel (HGDP-CEPH). Inbreeding is observed in almost all populations of the panel, and the highest inbreeding levels and frequencies of inbred individuals are found in populations of the Middle East, Central South Asia and the Americas. In these regions, first cousin (1C) marriages are the most frequent, but we also observed marriages between double first cousins (2 × 1C) and between avuncular (AV) pairs. Interestingly, if 2 × 1C marriages are preferred to AV marriages in Central South Asia and the Middle East, the contrary is found in the Americas. There are thus some regional trends but there are also some important differences between populations within a region. Individual results can be found on the CEPH website at ftp://ftp.cephb.fr/hgdp_hbd/.

SUBMITTER: Leutenegger AL

PROVIDER: S-EPMC3083608 | biostudies-literature | 2011 May

REPOSITORIES: biostudies-literature

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Consanguinity around the world: what do the genomic data of the HGDP-CEPH diversity panel tell us?

Leutenegger Anne-Louise AL Sahbatou Mourad M Gazal Steven S Cann Howard H Génin Emmanuelle E

European journal of human genetics : EJHG 20110302 5

Inbreeding coefficients and consanguineous mating types are usually inferred from population surveys or pedigree studies. Here, we present a method to estimate them from dense genome-wide single-nucleotide polymorphism genotypes and apply it to 940 unrelated individuals from the Human Genome Diversity Panel (HGDP-CEPH). Inbreeding is observed in almost all populations of the panel, and the highest inbreeding levels and frequencies of inbred individuals are found in populations of the Middle East ...[more]

PMID: 21364699

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Project description:BackgroundIt is well known that the pattern of linkage disequilibrium varies between human populations, with remarkable geographical stratification. Indirect association studies routinely exploit linkage disequilibrium around genes, particularly in isolated populations where it is assumed to be higher. Here, we explore both the amount and the decay of linkage disequilibrium with physical distance along 211 gene regions, most of them related to complex diseases, across 39 HGDP-CEPH population samples, focusing particularly on the populations defined as isolates. Within each gene region and population we use r2 between all possible single nucleotide polymorphism (SNP) pairs as a measure of linkage disequilibrium and focus on the proportion of SNP pairs with r2 greater than 0.8.ResultsAlthough the average r2 was found to be significantly different both between and within continental regions, a much higher proportion of r2 variance could be attributed to differences between continental regions (2.8% vs. 0.5%, respectively). Similarly, while the proportion of SNP pairs with r2 > 0.8 was significantly different across continents for all distance classes, it was generally much more homogenous within continents, except in the case of Africa and the Americas. The only isolated populations with consistently higher LD in all distance classes with respect to their continent are the Kalash (Central South Asia) and the Surui (America). Moreover, isolated populations showed only slightly higher proportions of SNP pairs with r2 > 0.8 per gene region than non-isolated populations in the same continent. Thus, the number of SNPs in isolated populations that need to be genotyped may be only slightly less than in non-isolates.ConclusionThe "isolated population" label by itself does not guarantee a greater genotyping efficiency in association studies, and properties other than increased linkage disequilibrium may make these populations interesting in genetic epidemiology.

Project description:Wheat blast is an emerging threat to wheat production, due to its recent migration to South Asia and Sub-Saharan Africa. Because genomic selection (GS) has emerged as a promising breeding strategy, the key objective of this study was to evaluate it for wheat blast phenotyped at precision phenotyping platforms in Quirusillas (Bolivia), Okinawa (Bolivia) and Jashore (Bangladesh) using three panels: (i) a diversity panel comprising 172 diverse spring wheat genotypes, (ii) a breeding panel comprising 248 elite breeding lines, and (iii) a full-sibs panel comprising 298 full-sibs. We evaluated two genomic prediction models (the genomic best linear unbiased prediction or GBLUP model and the Bayes B model) and compared the genomic prediction accuracies with accuracies from a fixed effects model (with selected blast-associated markers as fixed effects), a GBLUP + fixed effects model and a pedigree relationships-based model (ABLUP). On average, across all the panels and environments analyzed, the GBLUP + fixed effects model (0.63 ± 0.13) and the fixed effects model (0.62 ± 0.13) gave the highest prediction accuracies, followed by the Bayes B (0.59 ± 0.11), GBLUP (0.55 ± 0.1), and ABLUP (0.48 ± 0.06) models. The high prediction accuracies from the fixed effects model resulted from the markers tagging the 2NS translocation that had a large effect on blast in all the panels. This implies that in environments where the 2NS translocation-based blast resistance is effective, genotyping one to few markers tagging the translocation is sufficient to predict the blast response and genome-wide markers may not be needed. We also observed that marker-assisted selection (MAS) based on a few blast-associated markers outperformed GS as it selected the highest mean percentage (88.5%) of lines also selected by phenotypic selection and discarded the highest mean percentage of lines (91.8%) also discarded by phenotypic selection, across all panels. In conclusion, while this study demonstrates that MAS might be a powerful strategy to select for the 2NS translocation-based blast resistance, we emphasize that further efforts to use genomic tools to identify non-2NS translocation-based blast resistance are critical.

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Consanguinity around the world: what do the genomic data of the HGDP-CEPH diversity panel tell us?

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Consanguinity around the world: what do the genomic data of the HGDP-CEPH diversity panel tell us?

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