Genome-wide SNP analysis reveals no gain in power for association studies of common variants in the Finnish Saami

Huyghe, Jeroen R.; Fransén, Erik; Hannula, Samuli; Laer, Lut Van; Eyken, Els Van; Mäki‐Torkko, Elina; Lysholm-Bernacchi, Alana; Aikio, Pekka; Stephan, Dietrich A.; Sorri, Martti; Huentelman, Matthew J.; Camp, Guy Van

doi:10.1038/ejhg.2009.210

Cited by 3 publications

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“…22 We have published elsewhere the results of an elaborate genome-wide evaluation of the relative power for GWAS in the Saami. 43 A possible limitation of this study is the limited sample size. Recent studies indicate that several thousand subjects need to be recruited in order to obtain sufficient power to detect the effect sizes typically expected for complex phenotypes (with each contributing variant explaining as little as 0.1-1.3% of the variation), 44,45 although successful GWAS have been conducted using only 96 cases and 50 controls.…”

Section: Discussionmentioning

confidence: 99%

A genome-wide association study for age-related hearing impairment in the Saami

et al. 2010

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This study aimed at contributing to the elucidation of the genetic basis of age-related hearing impairment (ARHI), a common multifactorial disease with an important genetic contribution as demonstrated by heritability studies. We conducted a genomewide association study (GWAS) in the Finnish Saami, a small, ancient, genetically isolated population without evidence of demographic expansion. The choice of this study population was motivated by its anticipated higher extent of LD, potentially offering a substantial power advantage for association mapping. DNA samples and audiometric measurements were collected from 352 Finnish Saami individuals, aged between 50 and 75 years. To reduce the burden of multiple testing, we applied principal component (PC) analysis to the multivariate audiometric phenotype. The first three PCs captured 80% of the variation in hearing thresholds, while maintaining biologically important audiometric features. All subjects were genotyped with the Affymetrix 100 K chip. To account for multiple levels of relatedness among subjects, as well as for population stratification, association testing was performed using a mixed model. We summarised the top-ranking association signals for the three traits under study. The top-ranked SNP, rs457717 (P-value 3.55Â10 À7 ), was associated with PC3 and was localised in an intron of the IQ motif-containing GTPase-activating-like protein (IQGAP2). Intriguingly, the SNP rs161927 (P-value 0.000149), seventhranked for PC1, was positioned immediately downstream from the metabotropic glutamate receptor-7 gene (GRM7). As a previous GWAS of a European and Finnish sample set already suggested a role for GRM7 in ARHI, this study provides further evidence for the involvement of this gene.

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Section: Discussionmentioning

confidence: 99%

A genome-wide association study for age-related hearing impairment in the Saami

et al. 2010

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A genome-wide analysis of population structure in the Finnish Saami with implications for genetic association studies

et al. 2010

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The understanding of patterns of genetic variation within and among human populations is a prerequisite for successful genetic association mapping studies of complex diseases and traits. Some populations are more favorable for association mapping studies than others. The Saami from northern Scandinavia and the Kola Peninsula represent a population isolate that, among European populations, has been less extensively sampled, despite some early interest for association mapping studies. In this paper, we report the results of a first genome-wide SNP-based study of genetic population structure in the Finnish Saami. Using data from the HapMap and the human genome diversity project (HGDP-CEPH) and recently developed statistical methods, we studied individual genetic ancestry. We quantified genetic differentiation between the Saami population and the HGDP-CEPH populations by calculating pair-wise F(ST) statistics and by characterizing identity-by-state sharing for pair-wise population comparisons. This study affirms an east Asian contribution to the predominantly European-derived Saami gene pool. Using model-based individual ancestry analysis, the median estimated percentage of the genome with east Asian ancestry was 6% (first and third quartiles: 5 and 8%, respectively). We found that genetic similarity between population pairs roughly correlated with geographic distance. Among the European HGDP-CEPH populations, F(ST) was smallest for the comparison with the Russians (F(ST)=0.0098), and estimates for the other population comparisons ranged from 0.0129 to 0.0263. Our analysis also revealed fine-scale substructure within the Finnish Saami and warns against the confounding effects of both hidden population structure and undocumented relatedness in genetic association studies of isolated populations.

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Similarity in recombination rate and linkage disequilibrium at CYP2C and CYP2D cytochrome P450 gene regions among Europeans indicates signs of selection and no advantage of using tagSNPs in population isolates

Pimenoff

Laval

Comas

et al. 2012

Pharmacogenetics and Genomics

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The CEPH sample representing the general European population as such in the HapMap project seems to be the optimal population sample for the LD mapping of common complex traits among Europeans. Nevertheless, it is still argued that the unique pattern of LD in the Sami may offer an advantage for further association mapping, especially if multiple rare variants play a role in disease etiology. However, besides the activity-altering CYP2C9*3 (rs1057910) and CYP2C19*2 (rs4244285) variants, the high derived allele frequencies of novel recently identified acenocoumarol genome-wide associated SNPs at CYP2C9 (rs4086116) and CYP2C18 (rs12772169, rs1998591, rs2104543, rs1042194) loci variants indicated that the CYP2C region may have been influenced by selection. Thus, this fine-scale haplotype map of the CYP2C and CYP2D regions may help to choose markers for further association mapping of complex pharmacogenetic traits at these loci.

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Genome-wide SNP analysis reveals no gain in power for association studies of common variants in the Finnish Saami

Cited by 3 publications

References 33 publications

A genome-wide association study for age-related hearing impairment in the Saami

A genome-wide association study for age-related hearing impairment in the Saami

A genome-wide analysis of population structure in the Finnish Saami with implications for genetic association studies

Similarity in recombination rate and linkage disequilibrium at CYP2C and CYP2D cytochrome P450 gene regions among Europeans indicates signs of selection and no advantage of using tagSNPs in population isolates

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