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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.

Genome-wide association analyses of migraine and its subtypes identify new susceptibility loci, including rare variants with large effects implicating PRRT2, SCN11A and KCNK5.

Diagnosis and classification of peripheral neuropathy (PN) is facilitated by nerve conduction (NC) studies. Here, Bjornsdottir et al. find a low-frequency PRPH splice-donor variant that associates with NC amplitude and neurological assessment of recalled PRPH variant carriers reveals increased risk of a mild sensory-negative PN.

In this paper gene expression is treated as a quantitative trait in both blood and adipose tissue, and associations between specific genetic loci and body mass index are identified using a molecular network approach.

Analysis of long-read sequencing data from 3,622 Icelanders identifies a set of high-confidence structural variants and provides insights into their effect on human traits and diseases.

Bjarni Halldorsson, Kari Stefansson and colleagues analyze genomic data from 15,219 Icelanders to identify non-repetitive sequences that are missing from the reference genome. They describe 3,791 breakpoint-resolved sequence variants and find overlap with GWAS markers as well as the presence of a proportion of these variants in the chimpanzee genome.

Patrick Sulem, Hannes Helgason and colleagues identify homozygous and compound heterozygous loss-of-function variants of minor allele frequency <2% in 7.7% of the genotyped Icelandic population. Under transmission of some of these variants from heterozygous parents provides evidence that they are actually deleterious.

Ingileif Jonsdottir, Kari Stefansson and colleagues show that variants in the HLA class II region contribute to tuberculosis risk in populations of European ancestry. They propose that the associated variants influence disease risk by altering expression of HLA class II molecules presenting protective M. tuberculosis antigens to T cells.

Whole-genome sequencing of 78 Icelandic parent–offspring trios is used to study the de novo mutation rate at the genome-wide level; the rate is shown to increase by about two mutations a year as a function of the increasing age of the father at conception, highlighting the importance of father’s age on the risk of diseases such as autism and schizophrenia.

Analysis of whole-genome sequence data of Icelandic individuals has revealed a rare nonsense mutation within the LGR4 gene that is strongly associated with, among other things, low bone mineral density, late onset of menarche, and increased risk of biliary tract cancer.

Bjarni Halldorsson, Kari Stefansson and colleagues use SNP array and whole-genome sequencing data to estimate the meiotic gene conversion rate (G) in humans. They find that G for SNPs is 7.0 conversions/Mb per generation, is 2.17 greater in mothers than in fathers, and increases with maternal age.

The effect of sequence variants on phenotypes may depend on parental origin. Here, a method is developed that takes parental origin — the impact of which, to date, has largely been ignored — into account in genome-wide association studies. For 38,167 Icelanders genotyped, the parental origin of most alleles is determined; furthermore, a number of variants are found that show associations specific to parental origin, including three with type 2 diabetes.

Using a combination of whole-genome sequencing, haplotype sharing and the genealogies of the Icelandic population, Thorunn Rafnar, Kari Stefansson and colleagues identified a rare coding mutation in the gene of a BRCA1-interacting factor, BRIP1, that confers a high relative risk of ovarian cancer.

Solveig Gretarsdottir, Kari Stefansson and colleagues report a genome-wide association study for abdominal aortic aneurysm. They identified a variant located within the DAB2IP gene on 9q33 associated with risk of developing abdominal aortic aneurysm.

Here, human genome-wide single-nucleotide polymorphism (SNP) data from more than 15,000 parent–offspring pairs have been used to construct the first recombination maps that are based on directly observed recombination events. The data reveal interesting differences between the sexes: for instance, in males recombination tends to shuffle exons, whereas in females it generates new combinations of nearby genes. Comparison of these maps with others also reveals population differences.

While the consequences of homozygous loss of function variants have been studied, the effect of missense variants is less understood. Here, the authors identify pathogenic genotypes through an observed deficit of homozygous carriers of missense variants in a population, elucidating previously unexplained recessive disease and miscarriage.

Graphtyper is a fast and scalable method for variant genotyping that aligns short-read sequence data to a pangenome. Graphtyper was able to accurately genotype ∼90 million sequence variants in the whole genomes of ∼28,000 Icelanders, including those in six HLA genes.

Creatine kinase (CK) and lactate dehydrogenase (LDH) are biomarkers of tissue damages including myopathy and myocardial infarction. Here, Patrick Sulem and colleagues perform a genome-wide association study to identify common and rare genetic variants that associates with serum CK or LDH levels.

Intellectual disability (ID) is characterized by an intelligence quotient of below 70 and impaired adaptive skills. Here, analyzing whole genome sequences from 31,463 Icelanders, Walters et al. identify variants in MAP1B associated with ID and extensive brain-wide white matter deficits.

Mutations in genes encoding NAPDH oxidase subunits are known to be causative for the primary immunodeficiency chronic granulomatous disease (CGD). Here, the authors identify CYBC1 mutations in patients with CGD and show that CYBC1 is important for formation of the NADPH complex and respiratory burst.

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%.

The genetics of schizophrenia and other mental disorders are complex and poorly understood, and made even harder to study due to reduced reproduction resulting in negative selection pressure on risk alleles. Two independent large-scale genome wide studies of thousands of patients and controls by two international consortia confirm a previously identified locus, but also reveal novel associations. In this study, de novo (spontaneous) copy number variants are reported on chromosomes 1 and 15.

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.

A GWAS in Iceland reveals that variants in inner nuclear membrane proteins are associated with nuclear morphology of granulocytes and band neutrophil fraction.

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.

Gudmar Thorleifsson and colleagues report a genome-wide association study for primary open angle glaucoma, identifying a susceptibility locus near CAV1 and CAV2.

Gudjon Oskarsson et al. report a genome-wide association study of hemoglobin concentration in more than 680,000 individuals from Iceland and the UK. They identify six novel rare coding variants at the ACO1 locus that associate with either increased or decreased hemoglobin concentration, two of which have large and opposite effects.

Aimee Deaton et al. identify a rare missense variant in the bile acid receptor gene NR1H4, which is associated with lower levels of total cholesterol in the Icelandic population. Hepatocytes expressing the missense variant showed altered expression of a small number of genes, with enrichment in lipid-related pathways.

Julius Gudmundsson, Kari Stefansson and colleagues identify a low-frequency variant at 8q24 strongly associated with prostate cancer risk. They also confirm association of a recently reported risk variant in HOXB13 in samples from multiple European populations.

Patrick Sulem, Daniel Gudbjartsson, Bragi Walters and colleagues identify two low-frequency variants associated with serum uric acid levels and gout in the Icelandic population. The variants were discovered by whole-genome sequencing and are associated with two- to threefold differences in disease risk.

Hannes Helgason, Kari Stefansson and colleagues report an association study of gastric cancer susceptibility based on whole-genome sequencing in the Icelandic population. They find that loss-of-function variants in ATM confer risk of gastric cancer.