Mutations generate sequence diversity and provide a substrate for selection. The rate of de novo mutations is therefore of major importance to evolution. Here we conduct a study of genome-wide ...mutation rates by sequencing the entire genomes of 78 Icelandic parent-offspring trios at high coverage. We show that in our samples, with an average father's age of 29.7, the average de novo mutation rate is 1.20 × 10(-8) per nucleotide per generation. Most notably, the diversity in mutation rate of single nucleotide polymorphisms is dominated by the age of the father at conception of the child. The effect is an increase of about two mutations per year. An exponential model estimates paternal mutations doubling every 16.5 years. After accounting for random Poisson variation, father's age is estimated to explain nearly all of the remaining variation in the de novo mutation counts. These observations shed light on the importance of the father's age on the risk of diseases such as schizophrenia and autism.
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DOBA, IJS, IZUM, KILJ, KISLJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Mutation of the DNA molecule is one of the most fundamental processes in biology. In this study, we use 283 parent-offspring trios to estimate the rate of mutation for both single nucleotide variants ...(SNVs) and short length variants (indels) in humans and examine the mutation process. We found 17812 SNVs, corresponding to a mutation rate of 1.29 × 10-8 per position per generation (PPPG) and 1282 indels corresponding to a rate of 9.29 × 10-10 PPPG. We estimate that around 3% of human de novo SNVs are part of a multi-nucleotide mutation (MNM), with 558 (3.1%) of mutations positioned less than 20kb from another mutation in the same individual (median distance of 525bp). The rate of de novo mutations is greater in late replicating regions (p = 8.29 × 10-19) and nearer recombination events (p = 0.0038) than elsewhere in the genome.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Loss-of-function mutations cause many mendelian diseases. Here we aimed to create a catalog of autosomal genes that are completely knocked out in humans by rare loss-of-function mutations. We ...sequenced the whole genomes of 2,636 Icelanders and imputed the sequence variants identified in this set into 101,584 additional chip-genotyped and phased Icelanders. We found a total of 6,795 autosomal loss-of-function SNPs and indels in 4,924 genes. Of the genotyped Icelanders, 7.7% are homozygotes or compound heterozygotes for loss-of-function mutations with a minor allele frequency (MAF) below 2% in 1,171 genes (complete knockouts). Genes that are highly expressed in the brain are less often completely knocked out than other genes. Homozygous loss-of-function offspring of two heterozygous parents occurred less frequently than expected (deficit of 136 per 10,000 transmissions for variants with MAF <2%, 95% confidence interval (CI) = 10-261).
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DOBA, IJS, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
Meiotic recombinations contribute to genetic diversity by yielding new combinations of alleles. Recently, high-resolution recombination maps were inferred from high-density single-nucleotide ...polymorphism (SNP) data using linkage disequilibrium (LD) patterns that capture historical recombination events. The use of these maps has been demonstrated by the identification of recombination hotspots and associated motifs, and the discovery that the PRDM9 gene affects the proportion of recombinations occurring at hotspots. However, these maps provide no information about individual or sex differences. Moreover, locus-specific demographic factors like natural selection can bias LD-based estimates of recombination rate. Existing genetic maps based on family data avoid these shortcomings, but their resolution is limited by relatively few meioses and a low density of markers. Here we used genome-wide SNP data from 15,257 parent-offspring pairs to construct the first recombination maps based on directly observed recombinations with a resolution that is effective down to 10 kilobases (kb). Comparing male and female maps reveals that about 15% of hotspots in one sex are specific to that sex. Although male recombinations result in more shuffling of exons within genes, female recombinations generate more new combinations of nearby genes. We discover novel associations between recombination characteristics of individuals and variants in the PRDM9 gene and we identify new recombination hotspots. Comparisons of our maps with two LD-based maps inferred from data of HapMap populations of Utah residents with ancestry from northern and western Europe (CEU) and Yoruba in Ibadan, Nigeria (YRI) reveal population differences previously masked by noise and map differences at regions previously described as targets of natural selection.
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DOBA, IJS, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Meiotic recombination involves a combination of gene conversion and crossover events that, along with mutations, produce germline genetic diversity. Here we report the discovery of 3,176 SNP and 61 ...indel gene conversions. Our estimate of the non-crossover (NCO) gene conversion rate (G) is 7.0 for SNPs and 5.8 for indels per megabase per generation, and the GC bias is 67.6%. For indels, we demonstrate a 65.6% preference for the shorter allele. NCO gene conversions from mothers are longer than those from fathers, and G is 2.17 times greater in mothers. Notably, G increases with the age of mothers, but not the age of fathers. A disproportionate number of NCO gene conversions in older mothers occur outside double-strand break (DSB) regions and in regions with relatively low GC content. This points to age-related changes in the mechanisms of meiotic gene conversion in oocytes.
Electrocardiographic measures are indicative of the function of the cardiac conduction system. To search for sequence variants that modulate heart rate, PR interval and QRS duration in individuals of ...European descent, we performed a genome-wide association study in approximately 10,000 individuals and followed up the top signals in an additional approximately 10,000 individuals. We identified several genome-wide significant associations (with P < 1.6 x 10(-7)). We identified one locus for heart rate (MYH6), four for PR interval (TBX5, SCN10A, CAV1 and ARHGAP24) and four for QRS duration (TBX5, SCN10A, 6p21 and 10q21). We tested for association between these loci and subjects with selected arrhythmias in Icelandic and Norwegian case-control sample sets. We observed correlations between TBX5 and CAV1 and atrial fibrillation (P = 4.0 x 10(-5) and P = 0.00032, respectively), between TBX5 and advanced atrioventricular block (P = 0.0067), and between SCN10A and pacemaker implantation (P = 0.0029). We also replicated previously described associations with the QT interval.
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DOBA, IJS, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
Creatine kinase (CK) and lactate dehydrogenase (LDH) are widely used markers of tissue damage. To search for sequence variants influencing serum levels of CK and LDH, 28.3 million sequence variants ...identified through whole-genome sequencing of 2,636 Icelanders were imputed into 63,159 and 98,585 people with CK and LDH measurements, respectively. Here we describe 13 variants associating with serum CK and 16 with LDH levels, including four that associate with both. Among those, 15 are non-synonymous variants and 12 have a minor allele frequency below 5%. We report sequence variants in genes encoding the enzymes being measured (CKM and LDHA), as well as in genes linked to muscular (ANO5) and immune/inflammatory function (CD163/CD163L1, CSF1, CFH, HLA-DQB1, LILRB5, NINJ1 and STAB1). A number of the genes are linked to the mononuclear/phagocyte system and clearance of enzymes from the serum. This highlights the variety in the sources of normal diversity in serum levels of enzymes.
Malignant hyperthermia (MH) susceptibility is a rare life-threatening disorder that occurs upon exposure to a triggering agent. MH is commonly due to protein-altering variants in RYR1 and CACNA1S. ...The American College of Medical Genetics and Genomics recommends that when pathogenic and likely pathogenic variants in RYR1 and CACNA1S are incidentally found, they should be reported to the carriers. The detection of actionable variants allows the avoidance of exposure to triggering agents during anesthesia. First, we report a 10-year-old Icelandic proband with a suspected MH event, harboring a heterozygous missense variant NM_000540.2:c.6710G>A r.(6710g>a) p.(Cys2237Tyr) in the RYR1 gene that is likely pathogenic. The variant is private to four individuals within a three-generation family and absent from 62,240 whole-genome sequenced (WGS) Icelanders. Haplotype sharing and WGS revealed that the variant occurred as a somatic mosaicism also present in germline of the proband's paternal grandmother. Second, using a set of 62,240 Icelanders with WGS, we assessed the carrier frequency of actionable pathogenic and likely pathogenic variants in RYR1 and CACNA1S. We observed 13 actionable variants in RYR1, based on ClinVar classifications, carried by 43 Icelanders, and no actionable variant in CACNA1S. One in 1450 Icelanders carries an actionable variant for MH. Extensive sequencing allows for better classification and precise dating of variants, and WGS of a large fraction of the population has led to incidental findings of actionable MH genotypes.
Rare missense mutations in the gene encoding coatomer subunit alpha (COPA) have recently been shown to cause autoimmune interstitial lung, joint and kidney disease, also known as COPA syndrome, under ...a dominant mode of inheritance.
Here we describe an Icelandic family with three affected individuals over two generations with a rare clinical presentation of lung and joint disease and a histological diagnosis of follicular bronchiolitis. We performed whole-genome sequencing (WGS) of the three affected as well as three unaffected members of the family, and searched for rare genotypes associated with disease using 30,067 sequenced Icelanders as a reference population. We assessed all coding and splicing variants, prioritizing variants in genes known to cause interstitial lung disease. We detected a heterozygous missense mutation, p.Glu241Lys, in the COPA gene, private to the affected family members. The mutation occurred de novo in the paternal germline of the index case and was absent from 30,067 Icelandic genomes and 141,353 individuals from the genome Aggregation Database (gnomAD). The mutation occurs within the conserved and functionally important WD40 domain of the COPA protein.
This is the second report of the p.Glu241Lys mutation in COPA, indicating the recurrent nature of the mutation. The mutation was reported to co-segregate with COPA syndrome in a large family from the USA with five affected members, and classified as pathogenic. The two separate occurrences of the p.Glu241Lys mutation in cases and its absence from a large number of sequenced genomes confirms its role in the pathogenesis of the COPA syndrome.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Epileptic encephalopathies are a group of childhood epilepsies that display high phenotypic and genetic heterogeneity. The recent, extensive use of next-generation sequencing has identified a large ...number of genes in epileptic encephalopathies, including UBA5 in which biallelic mutations were first described as pathogenic in 2016 (Colin E et al., Am J Hum Genet 99(3):695-703, 2016. Muona M et al., Am J Hum Genet 99(3):683-694, 2016). UBA5 encodes an activating enzyme for a post-translational modification mechanism known as ufmylation, and is the first gene from the ufmylation pathway that is linked to disease.
We sequenced the genomes of two sisters with early-onset epileptic encephalopathy along with their unaffected parents in an attempt to find a genetic cause for their condition. The sisters, born in 2004 and 2006, presented with infantile spasms at six months of age, which later progressed to recurrent, treatment-resistant seizures. We detected a compound heterozygous genotype in UBA5 in the sisters, a genotype not seen elsewhere in an Icelandic reference set of 30,067 individuals nor in public databases. One of the mutations, c.684G > A, is a paternally inherited exonic splicing mutation, occuring at the last nucleotide of exon 7 of UBA5. The mutation is predicted to disrupt the splice site, resulting in loss-of-function of one allele of UBA5. The second mutation is a maternally inherited missense mutation, p.Ala371Thr, previously reported as pathogenic when in compound heterozygosity with a loss-of-function mutation in UBA5 and is believed to produce a hypomorphic allele. Supportive of this, we have identified three adult Icelanders homozygous for the p.Ala371Thr mutation who show no signs of neurological disease.
We describe compound heterozygous mutations in the UBA5 gene in two sisters with early-onset epileptic encephalopathy. To our knowledge, this is the first description of mutations in UBA5 since the initial discovery that pathogenic biallelic variants in the gene cause early-onset epileptic encephalopathy. We further provide confirmatory evidence that p.Ala371Thr is a hypomorphic mutation, by presenting three adult homozygotes who show no signs of neurological disease.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
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