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Daniel Gudbjartsson, Kari Stefansson and colleagues assess the effect of variants associated with mean fasting glucose levels on the variance in fasting glucose levels. They find that variants that increase both the levels and variance of fasting glucose increase type 2 diabetes risk, whereas those that increase the levels but reduce the variance do not.

Daniel Gudbjartsson and colleagues report a genome-wide association study for atrial fibrillation, a condition associated with increased risk of stroke. They report a variant in ZFHX3 associated with atrial fibrillation as well as ischemic stroke.

Daniel Gudbjartsson, Kari Stefansson and colleagues propose a new weighted Bonferroni approach for determining significance thresholds for human genome-wide association studies (GWAS). They demonstrate that the weighted approach, which is based on sequence annotation enrichments, improves power over standard GWAS methods.

Whole-genome sequencing data of 14,688 Icelanders, including 1,548 parent–offspring trios, show how the age and sex of parents affect the rate and spectrum of de novo mutations.

Daniel Gudbjartsson and colleagues report results of a genome-wide association study for loci influencing eosinophil counts. Follow-up studies showed that a subset of the variants identified in this screen were associated with risk of asthma or myocardial infarction.

Whole-genome sequencing of monozygotic twins, along with their parents, spouses and children, identifies postzygotic mutations present in the somatic tissue of one twin, but not the other, and characterizes differences in the number and timing of these mutations.

Aberrant morphology of the QRS complex in an electrocardiogram can be associated with cardiac morbidity and mortality. Here, the authors perform genome-wide association studies for ten measures of the QRS complex in 81,192 individuals and find 86 previously unreported loci that associate with at least one parameter.

This is an issue edsumm for 13. Identification of the Palaeocene/Eocene thermal maximum in a marine sedimentary sequence shows that sea surface temperatures near the North Pole increased from roughly 18 degrees Celsius to over 23 degrees Celsius — such warm values imply the absence of ice and thus exclude the influence of ice-albedo feedbacks on this Arctic warming.

Kari Stefansson and colleagues report the whole-genome sequencing of 2,636 individuals from Iceland to a median of 20× coverage, providing a valuable genomic resource for this population isolate. They characterize patterns of genetic variation and population structure and demonstrate the usefulness of this resource for genetic discovery for several disease phenotypes.

Sulem et al. report two previously unknown loci associated with variation in pigmentation in Northern Europeans. In two separate studies, Brown et al. and Gudbjartsson et al. report that some variants affecting human pigmentation, including variants on 20q11.22 near ASIP, also confer risk of cutaneous melanoma and basal cell carcinoma.

As the most common cardiac arrythmia, atrial fibrillation is of interest to physicians, and has recently been shown to have genetic components. Gudjbartsson et al. have conducted a genome-wide association scan in populations from around the globe, and find a strong link to a gene involved in early heart development. This gene, PITX2, could be a candidate for therapeutic intervention.

Analysis of 1,007 sibling pairs from 251 families identifies 878 de novo mutations shared by siblings at 448 sites. Recurrence probability based on parental somatic mosaicism, sibling sharing, parent of origin, mutation type and genomic position can range from 0.011% to 28.5%.

Gudbjartsson et al. report that variants near two genes, ASIP and TYR, are associated with risk of cutaneous melanoma and basal cell carcinoma. These loci are among several loci initially discovered for their role in human pigmentation, as reported by Sulem et al. In a separate study, Brown et al. independently discover an association between variants near ASIP and melanoma risk.

Erna Ivarsdottir et al. report a genome-wide association meta-analysis for age-related hearing loss in the Icelandic and UK populations. They identify 21 novel variants, 13 of which are rare, and reveal a genetic correlation between age-related hearing loss and tinnitus.