Publications by authors named "Gardar Sveinbjornsson"

49 Publications

Distinction between the effects of parental and fetal genomes on fetal growth.

Nat Genet 2021 08 19;53(8):1135-1142. Epub 2021 Jul 19.

deCODE genetics/Amgen, Reykjavik, Iceland.

Birth weight is a common measure of fetal growth that is associated with a range of health outcomes. It is directly affected by the fetal genome and indirectly by the maternal genome. We performed genome-wide association studies on birth weight in the genomes of the child and parents and further analyzed birth length and ponderal index, yielding a total of 243 fetal growth variants. We clustered those variants based on the effects of transmitted and nontransmitted alleles on birth weight. Out of 141 clustered variants, 22 were consistent with parent-of-origin-specific effects. We further used haplotype-specific polygenic risk scores to directly test the relationship between adult traits and birth weight. Our results indicate that the maternal genome contributes to increased birth weight through blood-glucose-raising alleles while blood-pressure-raising alleles reduce birth weight largely through the fetal genome.
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http://dx.doi.org/10.1038/s41588-021-00896-xDOI Listing
August 2021

Molecular benchmarks of a SARS-CoV-2 epidemic.

Nat Commun 2021 06 15;12(1):3633. Epub 2021 Jun 15.

deCODE genetics/Amgen, Inc., Reykjavik, Iceland.

A pressing concern in the SARS-CoV-2 epidemic and other viral outbreaks, is the extent to which the containment measures are halting the viral spread. A straightforward way to assess this is to tally the active cases and the recovered ones throughout the epidemic. Here, we show how epidemic control can be assessed with molecular information during a well characterized epidemic in Iceland. We demonstrate how the viral concentration decreased in those newly diagnosed as the epidemic transitioned from exponential growth phase to containment phase. The viral concentration in the cases identified in population screening decreased faster than in those symptomatic and considered at high risk and that were targeted by the healthcare system. The viral concentration persists in recovering individuals as we found that half of the cases are still positive after two weeks. We demonstrate that accumulation of mutations in SARS-CoV-2 genome can be exploited to track the rate of new viral generations throughout the different phases of the epidemic, where the accumulation of mutations decreases as the transmission rate decreases in the containment phase. Overall, the molecular signatures of SARS-CoV-2 infections contain valuable epidemiological information that can be used to assess the effectiveness of containment measures.
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http://dx.doi.org/10.1038/s41467-021-23883-6DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8206085PMC
June 2021

The genetic architecture of age-related hearing impairment revealed by genome-wide association analysis.

Commun Biol 2021 06 9;4(1):706. Epub 2021 Jun 9.

deCODE Genetics/Amgen, Reykjavik, Iceland.

Age-related hearing impairment (ARHI) is the most common sensory disorder in older adults. We conducted a genome-wide association meta-analysis of 121,934 ARHI cases and 591,699 controls from Iceland and the UK. We identified 21 novel sequence variants, of which 13 are rare, under either additive or recessive models. Of special interest are a missense variant in LOXHD1 (MAF = 1.96%) and a tandem duplication in FBF1 covering 4 exons (MAF = 0.22%) associating with ARHI (OR = 3.7 for homozygotes, P = 1.7 × 10 and OR = 4.2 for heterozygotes, P = 5.7 × 10, respectively). We constructed an ARHI genetic risk score (GRS) using common variants and showed that a common variant GRS can identify individuals at risk comparable to carriers of rare high penetrance variants. Furthermore, we found that ARHI and tinnitus share genetic causes. This study sheds a new light on the genetic architecture of ARHI, through several rare variants in both Mendelian deafness genes and genes not previously linked to hearing.
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http://dx.doi.org/10.1038/s42003-021-02224-9DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8190123PMC
June 2021

A meta-analysis uncovers the first sequence variant conferring risk of Bell's palsy.

Sci Rep 2021 Feb 18;11(1):4188. Epub 2021 Feb 18.

Rigshospitalet, Kobenhavn, Denmark.

Bell's palsy is the most common cause of unilateral facial paralysis and is defined as an idiopathic and acute inability to control movements of the facial muscles on the affected side. While the pathogenesis remains unknown, previous studies have implicated post-viral inflammation and resulting compression of the facial nerve. Reported heritability estimates of 4-14% suggest a genetic component in the etiology and an autosomal dominant inheritance has been proposed. Here, we report findings from a meta-analysis of genome-wide association studies uncovering the first unequivocal association with Bell's palsy (rs9357446-A; P = 6.79 × 10, OR = 1.23; N = 4714, N = 1,011,520). The variant also confers risk of intervertebral disc disorders (P = 2.99 × 10, OR = 1.04) suggesting a common pathogenesis in part or a true pleiotropy.
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http://dx.doi.org/10.1038/s41598-021-82736-wDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7893061PMC
February 2021

Loss-of-Function Variants in the Tumor-Suppressor Gene Confer Increased Cancer Risk.

Cancer Res 2021 04 18;81(8):1954-1964. Epub 2021 Feb 18.

deCODE Genetics/Amgen, Reykjavik, Iceland.

The success of genome-wide association studies (GWAS) in identifying common, low-penetrance variant-cancer associations for the past decade is undisputed. However, discovering additional high-penetrance cancer mutations in unknown cancer predisposing genes requires detection of variant-cancer association of ultra-rare coding variants. Consequently, large-scale next-generation sequence data with associated phenotype information are needed. Here, we used genotype data on 166,281 Icelanders, of which, 49,708 were whole-genome sequenced and 408,595 individuals from the UK Biobank, of which, 41,147 were whole-exome sequenced, to test for association between loss-of-function burden in autosomal genes and basal cell carcinoma (BCC), the most common cancer in Caucasians. A total of 25,205 BCC cases and 683,058 controls were tested. Rare germline loss-of-function variants in conferred substantial risks of BCC (OR, 8.0; = 1.9 × 10), with a quarter of carriers getting BCC before age 70 and over half in their lifetime. Furthermore, common variants at the locus were associated with BCC, suggesting as a new, high-impact BCC predisposition gene. A follow-up investigation of 24 cancers and three benign tumor types showed that loss-of-function variants are associated with high risk of cervical cancer (OR, 12.7, = 1.6 × 10) and low age at diagnosis. Our findings, using power-increasing methods with high-quality rare variant genotypes, highlight future prospects for new discoveries on carcinogenesis. SIGNIFICANCE: This study identifies the tumor-suppressor gene as a high-impact BCC predisposition gene and indicates that inactivation of by germline sequence variants may also lead to increased risk of cervical cancer.
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http://dx.doi.org/10.1158/0008-5472.CAN-20-3065DOI Listing
April 2021

Genetic insight into sick sinus syndrome.

Eur Heart J 2021 05;42(20):1959-1971

deCODE genetics/Amgen, Inc., Sturlugata 8, Reykjavik 101, Iceland.

Aims: The aim of this study was to use human genetics to investigate the pathogenesis of sick sinus syndrome (SSS) and the role of risk factors in its development.

Methods And Results: We performed a genome-wide association study of 6469 SSS cases and 1 000 187 controls from deCODE genetics, the Copenhagen Hospital Biobank, UK Biobank, and the HUNT study. Variants at six loci associated with SSS, a reported missense variant in MYH6, known atrial fibrillation (AF)/electrocardiogram variants at PITX2, ZFHX3, TTN/CCDC141, and SCN10A and a low-frequency (MAF = 1.1-1.8%) missense variant, p.Gly62Cys in KRT8 encoding the intermediate filament protein keratin 8. A full genotypic model best described the p.Gly62Cys association (P = 1.6 × 10-20), with an odds ratio (OR) of 1.44 for heterozygotes and a disproportionally large OR of 13.99 for homozygotes. All the SSS variants increased the risk of pacemaker implantation. Their association with AF varied and p.Gly62Cys was the only variant not associating with any other arrhythmia or cardiovascular disease. We tested 17 exposure phenotypes in polygenic score (PGS) and Mendelian randomization analyses. Only two associated with the risk of SSS in Mendelian randomization, AF, and lower heart rate, suggesting causality. Powerful PGS analyses provided convincing evidence against causal associations for body mass index, cholesterol, triglycerides, and type 2 diabetes (P > 0.05).

Conclusion: We report the associations of variants at six loci with SSS, including a missense variant in KRT8 that confers high risk in homozygotes and points to a mechanism specific to SSS development. Mendelian randomization supports a causal role for AF in the development of SSS.
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http://dx.doi.org/10.1093/eurheartj/ehaa1108DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8140484PMC
May 2021

Lifelong Reduction in LDL (Low-Density Lipoprotein) Cholesterol due to a Gain-of-Function Mutation in .

Circ Genom Precis Med 2021 02 14;14(1):e003029. Epub 2020 Dec 14.

deCODE genetics/Amgen, Inc (E.B., K.G., G.H.H., A.S., G.A.A., H.J., G.S., S.G., A.H., G. Thorleifsson, J.S., I.J., O.T.M., G.M., H.S., D.F.G., G. Thorgeirsson, H.H., B.V.H., P.M., G.L.N., P.S., U.T., K.S.), University of Iceland.

Background: Loss-of-function mutations in the LDL (low-density lipoprotein) receptor gene () cause elevated levels of LDL cholesterol and premature cardiovascular disease. To date, a gain-of-function mutation in with a large effect on LDL cholesterol levels has not been described. Here, we searched for sequence variants in that have a large effect on LDL cholesterol levels.

Methods: We analyzed whole-genome sequencing data from 43 202 Icelanders. Single-nucleotide polymorphisms and structural variants including deletions, insertions, and duplications were genotyped using whole-genome sequencing-based data. LDL cholesterol associations were carried out in a sample of >100 000 Icelanders with genetic information (imputed or whole-genome sequencing). Molecular analyses were performed using RNA sequencing and protein expression assays in Epstein-Barr virus-transformed lymphocytes.

Results: We discovered a 2.5-kb deletion (del2.5) overlapping the 3' untranslated region of in 7 heterozygous carriers from a single family. Mean level of LDL cholesterol was 74% lower in del2.5 carriers than in 101 851 noncarriers, a difference of 2.48 mmol/L (96 mg/dL; =8.4×10). Del2.5 results in production of an alternative mRNA isoform with a truncated 3' untranslated region. The truncation leads to a loss of target sites for microRNAs known to repress translation of . In Epstein-Barr virus-transformed lymphocytes derived from del2.5 carriers, expression of alternative mRNA isoform was 1.84-fold higher than the wild-type isoform (=0.0013), and there was 1.79-fold higher surface expression of the LDL receptor than in noncarriers (=0.0086). We did not find a highly penetrant detrimental impact of lifelong very low levels of LDL cholesterol due to del2.5 on health of the carriers.

Conclusions: Del2.5 is the first reported gain-of-function mutation in causing a large reduction in LDL cholesterol. These data point to a role for alternative polyadenylation of mRNA as a potent regulator of LDL receptor expression in humans.
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http://dx.doi.org/10.1161/CIRCGEN.120.003029DOI Listing
February 2021

Sequence Variants in TAAR5 and Other Loci Affect Human Odor Perception and Naming.

Curr Biol 2020 12 8;30(23):4643-4653.e3. Epub 2020 Oct 8.

deCODE Genetics/Amgen Inc., Sturlugata 8, 101 Reykjavik, Iceland; Faculty of Medicine, University of Iceland, Vatnsmyrarvegur 16, 101 Reykjavik, Iceland. Electronic address:

Olfactory receptor (OR) genes in humans form a special class characterized by unusually high DNA sequence diversity, which should give rise to differences in perception and behavior. In the largest genome-wide association study to date based on olfactory testing, we investigated odor perception and naming with smell tasks performed by 9,122 Icelanders, with replication in a separate sample of 2,204 individuals. We discovered an association between a low-frequency missense variant in TAAR5 and reduced intensity rating of fish odor containing trimethylamine (p.Ser95Pro, p = 5.6 × 10). We demonstrate that TAAR5 genotype affects aversion to fish odor, reflected by linguistic descriptions of the odor and pleasantness ratings. We also discovered common sequence variants in two canonical olfactory receptor loci that associate with increased intensity and naming of licorice odor (trans-anethole: lead variant p.Lys233Asn in OR6C70, p = 8.8 × 10 and p = 1.4 × 10) and enhanced naming of cinnamon (trans-cinnamaldehyde; intergenic variant rs317787-T, p = 5.0 × 10). Together, our results show that TAAR5 genotype variation influences human odor responses and highlight that sequence diversity in canonical OR genes can lead to enhanced olfactory ability, in contrast to the view that greater tolerance for mutations in the human OR repertoire leads to diminished function.
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http://dx.doi.org/10.1016/j.cub.2020.09.012DOI Listing
December 2020

Humoral Immune Response to SARS-CoV-2 in Iceland.

N Engl J Med 2020 10 1;383(18):1724-1734. Epub 2020 Sep 1.

From deCODE Genetics/Amgen (D.F.G., G.L.N., P.M., K.G., H.H., A.O.A., K. Bjarnadottir, B. Thorsteinsdottir, S.K., K. Birgisdottir, A.M.K., G.A.A., E.V.I., M.A., F.J., A.B.A., J.B., B.E., R.F., E.E.G., S.G., K.R.G., A.G., A.H., B.O.J., A.J., H.J., T.K., D.N.M., O.T.M., S.R., L.R., A.S., G. Sveinbjornsson, K.E.S., E.A.T., B. Thorbjornsson, J.S., G.M., G.G., U.T., I.J., P.S., K.S.), the School of Engineering and Natural Sciences (D.F.G., P.M.), the Department of Anthropology (A.H.), the BioMedical Center (K.G.K.), and the Faculty of Medicine, School of Health Sciences (M.I.S., M.G., K.G.K., R.P., U.T., I.J., K.S.), University of Iceland, Internal Medicine and Rehabilitation Services (E.E., D.H., R.F.I., M.G., L.B.O., M.K., R.P.), the Division of Anesthesia and Intensive Care Medicine (M.I.S.), and the Department of Clinical Microbiology (O.S.G., T.R.G., K.G.K., M.S.), Landspitali-the National University Hospital, and the Directorate of Health (G. Sigmundsdottir, M.T., K.S.J., A.M., T.G.), Reykjavik, and the Health Care Institution of South Iceland, Selfoss (S.H.K.) - all in Iceland.

Background: Little is known about the nature and durability of the humoral immune response to infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2).

Methods: We measured antibodies in serum samples from 30,576 persons in Iceland, using six assays (including two pan-immunoglobulin [pan-Ig] assays), and we determined that the appropriate measure of seropositivity was a positive result with both pan-Ig assays. We tested 2102 samples collected from 1237 persons up to 4 months after diagnosis by a quantitative polymerase-chain-reaction (qPCR) assay. We measured antibodies in 4222 quarantined persons who had been exposed to SARS-CoV-2 and in 23,452 persons not known to have been exposed.

Results: Of the 1797 persons who had recovered from SARS-CoV-2 infection, 1107 of the 1215 who were tested (91.1%) were seropositive; antiviral antibody titers assayed by two pan-Ig assays increased during 2 months after diagnosis by qPCR and remained on a plateau for the remainder of the study. Of quarantined persons, 2.3% were seropositive; of those with unknown exposure, 0.3% were positive. We estimate that 0.9% of Icelanders were infected with SARS-CoV-2 and that the infection was fatal in 0.3%. We also estimate that 56% of all SARS-CoV-2 infections in Iceland had been diagnosed with qPCR, 14% had occurred in quarantined persons who had not been tested with qPCR (or who had not received a positive result, if tested), and 30% had occurred in persons outside quarantine and not tested with qPCR.

Conclusions: Our results indicate that antiviral antibodies against SARS-CoV-2 did not decline within 4 months after diagnosis. We estimate that the risk of death from infection was 0.3% and that 44% of persons infected with SARS-CoV-2 in Iceland were not diagnosed by qPCR.
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http://dx.doi.org/10.1056/NEJMoa2026116DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7494247PMC
October 2020

Genetic variability in the absorption of dietary sterols affects the risk of coronary artery disease.

Eur Heart J 2020 07;41(28):2618-2628

Laekning, Medical Clinics, Lágmúli 5, 108 Reykjavik, Iceland.

Aims: To explore whether variability in dietary cholesterol and phytosterol absorption impacts the risk of coronary artery disease (CAD) using as instruments sequence variants in the ABCG5/8 genes, key regulators of intestinal absorption of dietary sterols.

Methods And Results: We examined the effects of ABCG5/8 variants on non-high-density lipoprotein (non-HDL) cholesterol (N up to 610 532) and phytosterol levels (N = 3039) and the risk of CAD in Iceland, Denmark, and the UK Biobank (105 490 cases and 844 025 controls). We used genetic scores for non-HDL cholesterol to determine whether ABCG5/8 variants confer greater risk of CAD than predicted by their effect on non-HDL cholesterol. We identified nine rare ABCG5/8 coding variants with substantial impact on non-HDL cholesterol. Carriers have elevated phytosterol levels and are at increased risk of CAD. Consistent with impact on ABCG5/8 transporter function in hepatocytes, eight rare ABCG5/8 variants associate with gallstones. A genetic score of ABCG5/8 variants predicting 1 mmol/L increase in non-HDL cholesterol associates with two-fold increase in CAD risk [odds ratio (OR) = 2.01, 95% confidence interval (CI) 1.75-2.31, P = 9.8 × 10-23] compared with a 54% increase in CAD risk (OR = 1.54, 95% CI 1.49-1.59, P = 1.1 × 10-154) associated with a score of other non-HDL cholesterol variants predicting the same increase in non-HDL cholesterol (P for difference in effects = 2.4 × 10-4).

Conclusions: Genetic variation in cholesterol absorption affects levels of circulating non-HDL cholesterol and risk of CAD. Our results indicate that both dietary cholesterol and phytosterols contribute directly to atherogenesis.
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http://dx.doi.org/10.1093/eurheartj/ehaa531DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7377579PMC
July 2020

Multi-ancestry GWAS of the electrocardiographic PR interval identifies 202 loci underlying cardiac conduction.

Nat Commun 2020 05 21;11(1):2542. Epub 2020 May 21.

Wellcome Centre for Human Genetics, University of Oxford, Oxford, UK.

The electrocardiographic PR interval reflects atrioventricular conduction, and is associated with conduction abnormalities, pacemaker implantation, atrial fibrillation (AF), and cardiovascular mortality. Here we report a multi-ancestry (N = 293,051) genome-wide association meta-analysis for the PR interval, discovering 202 loci of which 141 have not previously been reported. Variants at identified loci increase the percentage of heritability explained, from 33.5% to 62.6%. We observe enrichment for cardiac muscle developmental/contractile and cytoskeletal genes, highlighting key regulation processes for atrioventricular conduction. Additionally, 8 loci not previously reported harbor genes underlying inherited arrhythmic syndromes and/or cardiomyopathies suggesting a role for these genes in cardiovascular pathology in the general population. We show that polygenic predisposition to PR interval duration is an endophenotype for cardiovascular disease, including distal conduction disease, AF, and atrioventricular pre-excitation. These findings advance our understanding of the polygenic basis of cardiac conduction, and the genetic relationship between PR interval duration and cardiovascular disease.
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http://dx.doi.org/10.1038/s41467-020-15706-xDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7242331PMC
May 2020

Predicted loss and gain of function mutations in ACO1 are associated with erythropoiesis.

Commun Biol 2020 04 23;3(1):189. Epub 2020 Apr 23.

deCODE genetics/Amgen Inc., Reykjavik, Iceland.

Hemoglobin is the essential oxygen-carrying molecule in humans and is regulated by cellular iron and oxygen sensing mechanisms. To search for novel variants associated with hemoglobin concentration, we performed genome-wide association studies of hemoglobin concentration using a combined set of 684,122 individuals from Iceland and the UK. Notably, we found seven novel variants, six rare coding and one common, at the ACO1 locus associating with either decreased or increased hemoglobin concentration. Of these variants, the missense Cys506Ser and the stop-gained Lys334Ter mutations are specific to eight and ten generation pedigrees, respectively, and have the two largest effects in the study (Effect = -1.61 SD, CI = [-1.98, -1.35]; Effect = 0.63 SD, CI = [0.36, 0.91]). We also find Cys506Ser to associate with increased risk of persistent anemia (OR = 17.1, P = 2 × 10). The strong bidirectional effects seen in this study implicate ACO1, a known iron sensing molecule, as a major homeostatic regulator of hemoglobin concentration.
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http://dx.doi.org/10.1038/s42003-020-0921-5DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7181819PMC
April 2020

Spread of SARS-CoV-2 in the Icelandic Population.

N Engl J Med 2020 06 14;382(24):2302-2315. Epub 2020 Apr 14.

From deCODE Genetics-Amgen (D.F.G., A.H., H.J., O.T.M., P.M., G.L.N., J.S., A.S., P.S., A.B.A., B.E., R.F., E.E.G., G.G., K.R.G., A.G., H.H., B.O.J., A.J., F.J., T.K., D.N.M., L.R., G. Sveinbjornsson, K.E.S., E.A.T., B.T., G.M., I.J., U.T., K.S.), the School of Engineering and Natural Sciences (D.F.G., P.M.), the Department of Anthropology (A.H.), the Faculty of Medicine, School of Health Sciences (A.L., I.J., K.G.K., U.T., K.S.), and the BioMedical Center of the University of Iceland (K.G.K.), University of Iceland, the Department of Clinical Microbiology, Landspitali-National University Hospital (O.S.G., T.R.G., M.S., A.L., K.G.K.) and the Directorate of Health (K.S.J., G. Sigmundsdottir, A.D.M., T.G.) - all in Reykjavik, Iceland.

Background: During the current worldwide pandemic, coronavirus disease 2019 (Covid-19) was first diagnosed in Iceland at the end of February. However, data are limited on how SARS-CoV-2, the virus that causes Covid-19, enters and spreads in a population.

Methods: We targeted testing to persons living in Iceland who were at high risk for infection (mainly those who were symptomatic, had recently traveled to high-risk countries, or had contact with infected persons). We also carried out population screening using two strategies: issuing an open invitation to 10,797 persons and sending random invitations to 2283 persons. We sequenced SARS-CoV-2 from 643 samples.

Results: As of April 4, a total of 1221 of 9199 persons (13.3%) who were recruited for targeted testing had positive results for infection with SARS-CoV-2. Of those tested in the general population, 87 (0.8%) in the open-invitation screening and 13 (0.6%) in the random-population screening tested positive for the virus. In total, 6% of the population was screened. Most persons in the targeted-testing group who received positive tests early in the study had recently traveled internationally, in contrast to those who tested positive later in the study. Children under 10 years of age were less likely to receive a positive result than were persons 10 years of age or older, with percentages of 6.7% and 13.7%, respectively, for targeted testing; in the population screening, no child under 10 years of age had a positive result, as compared with 0.8% of those 10 years of age or older. Fewer females than males received positive results both in targeted testing (11.0% vs. 16.7%) and in population screening (0.6% vs. 0.9%). The haplotypes of the sequenced SARS-CoV-2 viruses were diverse and changed over time. The percentage of infected participants that was determined through population screening remained stable for the 20-day duration of screening.

Conclusions: In a population-based study in Iceland, children under 10 years of age and females had a lower incidence of SARS-CoV-2 infection than adolescents or adults and males. The proportion of infected persons identified through population screening did not change substantially during the screening period, which was consistent with a beneficial effect of containment efforts. (Funded by deCODE Genetics-Amgen.).
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http://dx.doi.org/10.1056/NEJMoa2006100DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7175425PMC
June 2020

Eighty-eight variants highlight the role of T cell regulation and airway remodeling in asthma pathogenesis.

Nat Commun 2020 01 20;11(1):393. Epub 2020 Jan 20.

deCODE genetics/Amgen, Inc., Reykjavik, Iceland.

Asthma is one of the most common chronic diseases affecting both children and adults. We report a genome-wide association meta-analysis of 69,189 cases and 702,199 controls from Iceland and UK biobank. We find 88 asthma risk variants at 56 loci, 19 previously unreported, and evaluate their effect on other asthma and allergic phenotypes. Of special interest are two low frequency variants associated with protection against asthma; a missense variant in TNFRSF8 and 3' UTR variant in TGFBR1. Functional studies show that the TNFRSF8 variant reduces TNFRSF8 expression both on cell surface and in soluble form, acting as loss of function. eQTL analysis suggests that the TGFBR1 variant acts through gain of function and together with an intronic variant in a downstream gene, SMAD3, points to defective TGFβR1 signaling as one of the biological perturbations increasing asthma risk. Our results increase the number of asthma variants and implicate genes with known role in T cell regulation, inflammation and airway remodeling in asthma pathogenesis.
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http://dx.doi.org/10.1038/s41467-019-14144-8DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6971247PMC
January 2020

Associations of autozygosity with a broad range of human phenotypes.

Nat Commun 2019 10 31;10(1):4957. Epub 2019 Oct 31.

Department of Neurology, Brain Centre Rudolf Magnus, University Medical Centre Utrecht, Utrecht University, Utrecht, 3584 CX, The Netherlands.

In many species, the offspring of related parents suffer reduced reproductive success, a phenomenon known as inbreeding depression. In humans, the importance of this effect has remained unclear, partly because reproduction between close relatives is both rare and frequently associated with confounding social factors. Here, using genomic inbreeding coefficients (F) for >1.4 million individuals, we show that F is significantly associated (p < 0.0005) with apparently deleterious changes in 32 out of 100 traits analysed. These changes are associated with runs of homozygosity (ROH), but not with common variant homozygosity, suggesting that genetic variants associated with inbreeding depression are predominantly rare. The effect on fertility is striking: F equivalent to the offspring of first cousins is associated with a 55% decrease [95% CI 44-66%] in the odds of having children. Finally, the effects of F are confirmed within full-sibling pairs, where the variation in F is independent of all environmental confounding.
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http://dx.doi.org/10.1038/s41467-019-12283-6DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6823371PMC
October 2019

Common and Rare Sequence Variants Influencing Tumor Biomarkers in Blood.

Cancer Epidemiol Biomarkers Prev 2020 01 30;29(1):225-235. Epub 2019 Oct 30.

deCODE genetics/AMGEN, Reykjavik, Iceland.

Background: Alpha-fetoprotein (AFP), cancer antigens 15.3, 19.9, and 125, carcinoembryonic antigen, and alkaline phosphatase (ALP) are widely measured in attempts to detect cancer and to monitor treatment response. However, due to lack of sensitivity and specificity, their utility is debated. The serum levels of these markers are affected by a number of nonmalignant factors, including genotype. Thus, it may be possible to improve both sensitivity and specificity by adjusting test results for genetic effects.

Methods: We performed genome-wide association studies of serum levels of AFP ( = 22,686), carcinoembryonic antigen ( = 22,309), cancer antigens 15.3 ( = 7,107), 19.9 ( = 9,945), and 125 ( = 9,824), and ALP ( = 162,774). We also examined the correlations between levels of these biomarkers and the presence of cancer, using data from a nationwide cancer registry.

Results: We report a total of 84 associations of 79 sequence variants with levels of the six biomarkers, explaining between 2.3% and 42.3% of the phenotypic variance. Among the 79 variants, 22 are cis (in- or near the gene encoding the biomarker), 18 have minor allele frequency less than 1%, 31 are coding variants, and 7 are associated with gene expression in whole blood. We also find multiple conditions associated with higher biomarker levels.

Conclusions: Our results provide insights into the genetic contribution to diversity in concentration of tumor biomarkers in blood.

Impact: Genetic correction of biomarker values could improve prediction algorithms and decision-making based on these biomarkers.
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http://dx.doi.org/10.1158/1055-9965.EPI-18-1060DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6954334PMC
January 2020

Sequence variants with large effects on cardiac electrophysiology and disease.

Nat Commun 2019 10 22;10(1):4803. Epub 2019 Oct 22.

deCODE genetics/Amgen Inc., Reykjavik, Iceland.

Features of the QRS complex of the electrocardiogram, reflecting ventricular depolarisation, associate with various physiologic functions and several pathologic conditions. We test 32.5 million variants for association with ten measures of the QRS complex in 12 leads, using 405,732 electrocardiograms from 81,192 Icelanders. We identify 190 associations at 130 loci, the majority of which have not been reported before, including associations with 21 rare or low-frequency coding variants. Assessment of genes expressed in the heart yields an additional 13 rare QRS coding variants at 12 loci. We find 51 unreported associations between the QRS variants and echocardiographic traits and cardiovascular diseases, including atrial fibrillation, complete AV block, heart failure and supraventricular tachycardia. We demonstrate the advantage of in-depth analysis of the QRS complex in conjunction with other cardiovascular phenotypes to enhance our understanding of the genetic basis of myocardial mass, cardiac conduction and disease.
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http://dx.doi.org/10.1038/s41467-019-12682-9DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6805929PMC
October 2019

Target genes, variants, tissues and transcriptional pathways influencing human serum urate levels.

Nat Genet 2019 10 2;51(10):1459-1474. Epub 2019 Oct 2.

Department of Neurobiology, Care Sciences and Society, Division of Family Medicine and Primary Care, Karolinska Institutet, Stockholm, Sweden.

Elevated serum urate levels cause gout and correlate with cardiometabolic diseases via poorly understood mechanisms. We performed a trans-ancestry genome-wide association study of serum urate in 457,690 individuals, identifying 183 loci (147 previously unknown) that improve the prediction of gout in an independent cohort of 334,880 individuals. Serum urate showed significant genetic correlations with many cardiometabolic traits, with genetic causality analyses supporting a substantial role for pleiotropy. Enrichment analysis, fine-mapping of urate-associated loci and colocalization with gene expression in 47 tissues implicated the kidney and liver as the main target organs and prioritized potentially causal genes and variants, including the transcriptional master regulators in the liver and kidney, HNF1A and HNF4A. Experimental validation showed that HNF4A transactivated the promoter of ABCG2, encoding a major urate transporter, in kidney cells, and that HNF4A p.Thr139Ile is a functional variant. Transcriptional coregulation within and across organs may be a general mechanism underlying the observed pleiotropy between urate and cardiometabolic traits.
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http://dx.doi.org/10.1038/s41588-019-0504-xDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6858555PMC
October 2019

Genome-wide association meta-analyses and fine-mapping elucidate pathways influencing albuminuria.

Nat Commun 2019 09 11;10(1):4130. Epub 2019 Sep 11.

Department of Medicine, Division of Nephrology and Hypertension, University of Utah, Salt Lake City, UT, USA.

Increased levels of the urinary albumin-to-creatinine ratio (UACR) are associated with higher risk of kidney disease progression and cardiovascular events, but underlying mechanisms are incompletely understood. Here, we conduct trans-ethnic (n = 564,257) and European-ancestry specific meta-analyses of genome-wide association studies of UACR, including ancestry- and diabetes-specific analyses, and identify 68 UACR-associated loci. Genetic correlation analyses and risk score associations in an independent electronic medical records database (n = 192,868) reveal connections with proteinuria, hyperlipidemia, gout, and hypertension. Fine-mapping and trans-Omics analyses with gene expression in 47 tissues and plasma protein levels implicate genes potentially operating through differential expression in kidney (including TGFB1, MUC1, PRKCI, and OAF), and allow coupling of UACR associations to altered plasma OAF concentrations. Knockdown of OAF and PRKCI orthologs in Drosophila nephrocytes reduces albumin endocytosis. Silencing fly PRKCI further impairs slit diaphragm formation. These results generate a priority list of genes and pathways for translational research to reduce albuminuria.
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http://dx.doi.org/10.1038/s41467-019-11576-0DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6739370PMC
September 2019

A catalog of genetic loci associated with kidney function from analyses of a million individuals.

Nat Genet 2019 06 31;51(6):957-972. Epub 2019 May 31.

Diabetes and Cardiovascular Disease-Genetic Epidemiology, Department of Clincial Sciences in Malmö, Lund University, Malmö, Sweden.

Chronic kidney disease (CKD) is responsible for a public health burden with multi-systemic complications. Through trans-ancestry meta-analysis of genome-wide association studies of estimated glomerular filtration rate (eGFR) and independent replication (n = 1,046,070), we identified 264 associated loci (166 new). Of these, 147 were likely to be relevant for kidney function on the basis of associations with the alternative kidney function marker blood urea nitrogen (n = 416,178). Pathway and enrichment analyses, including mouse models with renal phenotypes, support the kidney as the main target organ. A genetic risk score for lower eGFR was associated with clinically diagnosed CKD in 452,264 independent individuals. Colocalization analyses of associations with eGFR among 783,978 European-ancestry individuals and gene expression across 46 human tissues, including tubulo-interstitial and glomerular kidney compartments, identified 17 genes differentially expressed in kidney. Fine-mapping highlighted missense driver variants in 11 genes and kidney-specific regulatory variants. These results provide a comprehensive priority list of molecular targets for translational research.
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http://dx.doi.org/10.1038/s41588-019-0407-xDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6698888PMC
June 2019

Genome-wide association meta-analysis yields 20 loci associated with gallstone disease.

Nat Commun 2018 11 30;9(1):5101. Epub 2018 Nov 30.

deCODE Genetics/Amgen, Inc., Reykjavik, 101, Iceland.

Gallstones are responsible for one of the most common diseases in the Western world and are commonly treated with cholecystectomy. We perform a meta-analysis of two genome-wide association studies of gallstone disease in Iceland and the UK, totaling 27,174 cases and 736,838 controls, uncovering 21 novel gallstone-associated variants at 20 loci. Two distinct low frequency missense variants in SLC10A2, encoding the apical sodium-dependent bile acid transporter (ASBT), associate with an increased risk of gallstone disease (Pro290Ser: OR = 1.36 [1.25-1.49], P = 2.1 × 10, MAF = 1%; Val98Ile: OR = 1.15 [1.10-1.20], P = 1.8 × 10, MAF = 4%). We demonstrate that lower bile acid transport by ASBT is accompanied by greater risk of gallstone disease and highlight the role of the intestinal compartment of the enterohepatic circulation of bile acids in gallstone disease susceptibility. Additionally, two low frequency missense variants in SERPINA1 and HNF4A and 17 common variants represent novel associations with gallstone disease.
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http://dx.doi.org/10.1038/s41467-018-07460-yDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6269469PMC
November 2018

Sequence variants associating with urinary biomarkers.

Hum Mol Genet 2019 04;28(7):1199-1211

Faculty of Medicine, University of Iceland, Reykjavik, Iceland.

Urine dipstick tests are widely used in routine medical care to diagnose kidney and urinary tract and metabolic diseases. Several environmental factors are known to affect the test results, whereas the effects of genetic diversity are largely unknown. We tested 32.5 million sequence variants for association with urinary biomarkers in a set of 150 274 Icelanders with urine dipstick measurements. We detected 20 association signals, of which 14 are novel, associating with at least one of five clinical entities defined by the urine dipstick: glucosuria, ketonuria, proteinuria, hematuria and urine pH. These include three independent glucosuria variants at SLC5A2, the gene encoding the sodium-dependent glucose transporter (SGLT2), a protein targeted pharmacologically to increase urinary glucose excretion in the treatment of diabetes. Two variants associating with proteinuria are in LRP2 and CUBN, encoding the co-transporters megalin and cubilin, respectively, that mediate proximal tubule protein uptake. One of the hematuria-associated variants is a rare, previously unreported 2.5 kb exonic deletion in COL4A3. Of the four signals associated with urine pH, we note that the pH-increasing alleles of two variants (POU2AF1, WDR72) associate significantly with increased risk of kidney stones. Our results reveal that genetic factors affect variability in urinary biomarkers, in both a disease dependent and independent context.
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http://dx.doi.org/10.1093/hmg/ddy409DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6423415PMC
April 2019

Meta-analysis of Icelandic and UK data sets identifies missense variants in SMO, IL11, COL11A1 and 13 more new loci associated with osteoarthritis.

Nat Genet 2018 12 29;50(12):1681-1687. Epub 2018 Oct 29.

deCODE genetics/Amgen, Inc., Reykjavik, Iceland.

Osteoarthritis has a highly negative impact on quality of life because of the associated pain and loss of joint function. Here we describe the largest meta-analysis so far of osteoarthritis of the hip and the knee in samples from Iceland and the UK Biobank (including 17,151 hip osteoarthritis patients, 23,877 knee osteoarthritis patients, and more than 562,000 controls). We found 23 independent associations at 22 loci in the additive meta-analyses, of which 16 of the loci were novel: 12 for hip and 4 for knee osteoarthritis. Two associations are between rare or low-frequency missense variants and hip osteoarthritis, affecting the genes SMO (rs143083812, frequency 0.11%, odds ratio (OR) = 2.8, P = 7.9 × 10, p.Arg173Cys) and IL11 (rs4252548, frequency 2.08%, OR = 1.30, P = 2.1 × 10, p.Arg112His). A common missense variant in the COL11A1 gene also associates with hip osteoarthritis (rs3753841, frequency 61%, P = 5.2 × 10, OR = 1.08, p.Pro1284Leu). In addition, using a recessive model, we confirm an association between hip osteoarthritis and a variant of CHADL (rs117018441, P = 1.8 × 10, OR = 5.9). Furthermore, we observe a complex relationship between height and risk of osteoarthritis.
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http://dx.doi.org/10.1038/s41588-018-0247-0DOI Listing
December 2018

Variants in NKX2-5 and FLNC Cause Dilated Cardiomyopathy and Sudden Cardiac Death.

Circ Genom Precis Med 2018 08;11(8):e002151

Adalbjorg Jonasdottir, Aslaug Jonasdottir, E.B., B.O.J., G.A.A., D.O.A., I.J., U.T., P.S., G.T., D.F.G., H.H., K.S.).

Background: Dilated cardiomyopathy (DCM) is an important cause of heart failure. Variants in >50 genes have been reported to cause DCM, but causative variants have been found in less than half of familial cases. Variants causing DCM in Iceland have not been reported before.

Methods: We performed a genome-wide association study on DCM based on whole genome sequencing. We tested the association of 32.5 million sequence variants in 424 cases and 337 689 population controls in Iceland.

Results: We identified 2 DCM variants in established cardiomyopathy genes, a missense variant p.Phe145Leu in NKX2-5 carried by 1 in 7100 Icelanders ( P=7.0×10) and a frameshift variant p.Phe1626Serfs*40 in FLNC carried by 1 in 3600 Icelanders ( P=2.1×10). Both variants associate with heart failure and sudden cardiac death. Additionally, p.Phe145Leu in NKX2-5 associates with high degree atrioventricular block and atrial septal defect ( P<1.4×10). The penetrance of serious heart disease among carriers of the NKX2-5 variant is high and higher than that of the FLNC variant.

Conclusions: Two rare variants in NKX2-5 and FLNC, carried by 1 in 2400 Icelanders, cause familial DCM in Iceland. These genes have recently been associated with DCM. Given the serious consequences of these variants, we suggest screening for them in individuals with DCM and their family members, with subsequent monitoring of carriers, offering early intervention.
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http://dx.doi.org/10.1161/CIRCGEN.117.002151DOI Listing
August 2018

Coding variants in and increase risk of atrial fibrillation.

Commun Biol 2018 12;1:68. Epub 2018 Jun 12.

HUNT Research Centre, Department of Public Health and General Practice, Norwegian University of Science and Technology, Levanger, Norway.

Most sequence variants identified hitherto in genome-wide association studies (GWAS) of atrial fibrillation are common, non-coding variants associated with risk through unknown mechanisms. We performed a meta-analysis of GWAS of atrial fibrillation among 29,502 cases and 767,760 controls from Iceland and the UK Biobank with follow-up in samples from Norway and the US, focusing on low-frequency coding and splice variants aiming to identify causal genes. We observe associations with one missense (OR = 1.20) and one splice-donor variant (OR = 1.50) in , the first ribosomal gene implicated in atrial fibrillation to our knowledge. Analysis of 167 RNA samples from the right atrium reveals that the splice-donor variant in results in exon skipping. We also observe an association with a missense variant in (OR = 1.38), encoding a component of the intercalated discs of cardiomyocytes. Both discoveries emphasize the close relationship between the mechanical and electrical function of the heart.
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http://dx.doi.org/10.1038/s42003-018-0068-9DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6123807PMC
June 2018

A truncating mutation in EPOR leads to hypo-responsiveness to erythropoietin with normal haemoglobin.

Commun Biol 2018 17;1:49. Epub 2018 May 17.

deCODE genetics/Amgen, Inc, 101, Reykjavik, Iceland.

The cytokine erythropoietin (EPO), signalling through the EPO receptor (EPO-R), is essential for the formation of red blood cells. We performed a genome-wide association study (GWAS) testing 32.5 million sequence variants for association with serum EPO levels in a set of 4187 individuals. We detect an association between a rare and well imputed stop-gained variant rs370865377[A] (p.Gln82Ter) in , carried by 1 in 550 Icelanders, and increased serum EPO levels (MAF = 0.09%, Effect = 1.47 SD,  = 3.3 × 10). We validated these findings by measuring serum EPO levels in 34 additional pairs of carriers and matched controls and found carriers to have 3.23-fold higher EPO levels than controls ( = 1.7 × 10;  = 1.6 × 10). In contrast to previously reported EPOR mutations, p.Gln82Ter does not associate with haemoglobin levels (Effect = -0.045 SD,  = 0.32,  = 273,160), probably due to a compensatory EPO upregulation in response to EPO-R hypo-responsiveness.
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http://dx.doi.org/10.1038/s42003-018-0053-3DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6123817PMC
May 2018

Variants associating with uterine leiomyoma highlight genetic background shared by various cancers and hormone-related traits.

Nat Commun 2018 09 7;9(1):3636. Epub 2018 Sep 7.

deCODE Genetics/Amgen, Sturlugata 8, 101, Reykjavik, Iceland.

Uterine leiomyomas are common benign tumors of the myometrium. We performed a meta-analysis of two genome-wide association studies of leiomyoma in European women (16,595 cases and 523,330 controls), uncovering 21 variants at 16 loci that associate with the disease. Five variants were previously reported to confer risk of various malignant or benign tumors (rs78378222 in TP53, rs10069690 in TERT, rs1800057 and rs1801516 in ATM, and rs7907606 at OBFC1) and four signals are located at established risk loci for hormone-related traits (endometriosis and breast cancer) at 1q36.12 (CDC42/WNT4), 2p25.1 (GREB1), 20p12.3 (MCM8), and 6q26.2 (SYNE1/ESR1). Polygenic score for leiomyoma, computed using UKB data, is significantly correlated with risk of cancer in the Icelandic population. Functional annotation suggests that the non-coding risk variants affect multiple genes, including ESR1. Our results provide insights into the genetic background of leiomyoma that are shared by other benign and malignant tumors and highlight the role of hormones in leiomyoma growth.
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http://dx.doi.org/10.1038/s41467-018-05428-6DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6128903PMC
September 2018

MAP1B mutations cause intellectual disability and extensive white matter deficit.

Nat Commun 2018 08 27;9(1):3456. Epub 2018 Aug 27.

deCODE genetics/Amgen, Reykjavik, 101, Iceland.

Discovery of coding variants in genes that confer risk of neurodevelopmental disorders is an important step towards understanding the pathophysiology of these disorders. Whole-genome sequencing of 31,463 Icelanders uncovers a frameshift variant (E712KfsTer10) in microtubule-associated protein 1B (MAP1B) that associates with ID/low IQ in a large pedigree (genome-wide corrected P = 0.022). Additional stop-gain variants in MAP1B (E1032Ter and R1664Ter) validate the association with ID and IQ. Carriers have 24% less white matter (WM) volume (β = -2.1SD, P = 5.1 × 10), 47% less corpus callosum (CC) volume (β = -2.4SD, P = 5.5 × 10) and lower brain-wide fractional anisotropy (P = 6.7 × 10). In summary, we show that loss of MAP1B function affects general cognitive ability through a profound, brain-wide WM deficit with likely disordered or compromised axons.
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http://dx.doi.org/10.1038/s41467-018-05595-6DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6110722PMC
August 2018

Author Correction: Genome-wide association and HLA fine-mapping studies identify risk loci and genetic pathways underlying allergic rhinitis.

Nat Genet 2018 09;50(9):1343

Allergy and Lung Health Unit, Melbourne School of Population and Global Health, University of Melbourne, Melbourne, Victoria, Australia.

In the version of this article initially published, in Fig. 3, the y-axis numbering did not match the log scale indicated in the axis label. The error has been corrected in the HTML and PDF version of the article.
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http://dx.doi.org/10.1038/s41588-018-0197-6DOI Listing
September 2018

Biobank-driven genomic discovery yields new insight into atrial fibrillation biology.

Nat Genet 2018 09 30;50(9):1234-1239. Epub 2018 Jul 30.

Department of Biostatistics, Center for Statistical Genetics, University of Michigan, Ann Arbor, MI, USA.

To identify genetic variation underlying atrial fibrillation, the most common cardiac arrhythmia, we performed a genome-wide association study of >1,000,000 people, including 60,620 atrial fibrillation cases and 970,216 controls. We identified 142 independent risk variants at 111 loci and prioritized 151 functional candidate genes likely to be involved in atrial fibrillation. Many of the identified risk variants fall near genes where more deleterious mutations have been reported to cause serious heart defects in humans (GATA4, MYH6, NKX2-5, PITX2, TBX5), or near genes important for striated muscle function and integrity (for example, CFL2, MYH7, PKP2, RBM20, SGCG, SSPN). Pathway and functional enrichment analyses also suggested that many of the putative atrial fibrillation genes act via cardiac structural remodeling, potentially in the form of an 'atrial cardiomyopathy', either during fetal heart development or as a response to stress in the adult heart.
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http://dx.doi.org/10.1038/s41588-018-0171-3DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6530775PMC
September 2018
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