Alkes Price and colleagues report estimates of the narrow-sense heritability (h2) explained for 23 complex phenotypes, including 11 quantitative and 12 dichotomous traits (PLoS Genet. 9, e1003520, 2013). They analyzed 300,000 SNPs genotyped in 38,167 individuals from Iceland, including long-range phasing, combined with an extensive genealogical database. Their heritability estimates were smaller than those previously reported, which have often been based on comparisons between closely related individuals. In contrast, the authors developed a new identity by descent (IBD)-based approach that allows for heritability estimation using data from both closely and distantly related pairs of individuals. Their linear mixed-model approach allows for joint estimation of h2 and the fraction of heritability explained by SNPs genotyped in genome-wide association studies (GWAS), facilitating a direct comparison of these estimates using the same data sets. The authors also examined the effects of shared environment, dominance and epistasis and found that shared environment was the major contributor to the inflation of h2 estimates observed in data sets including closely related individuals. The authors are also more optimistic than those of previous reports in terms of expectations for the fraction of heritability explained by common variation, noting that over half of h2 may be explained by SNPs on genotyping platforms used in GWAS.
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Bahcall, O. Heritability estimates. Nat Genet 45, 722 (2013). https://doi.org/10.1038/ng.2691