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Amyotrophic lateral sclerosis is characterised by the progressive loss of motor neurons in the brain and spinal cord. This neurodegenerative syndrome shares pathobiological features with frontotemporal dementia and, indeed, many patients show features of both diseases. Many different genes and pathophysiological processes contribute to the disease, and it will be necessary to understand this heterogeneity to find effective treatments. In this Seminar, we discuss clinical and diagnostic approaches as well as scientific advances in the research fields of genetics, disease modelling, biomarkers, and therapeutic strategies., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

To identify genetic factors contributing to amyotrophic lateral sclerosis (ALS), we conducted whole-exome analyses of 1,022 index familial ALS (FALS) cases and 7,315 controls. In a new screening strategy, we performed gene-burden analyses trained with established ALS genes and identified a significant association between loss-of-function (LOF) NEK1 variants and FALS risk. Independently, autozygosity mapping for an isolated community in the Netherlands identified a NEK1 p.Arg261His variant as a candidate risk factor. Replication analyses of sporadic ALS (SALS) cases and independent control cohorts confirmed significant disease association for both p.Arg261His (10,589 samples analyzed) and NEK1 LOF variants (3,362 samples analyzed). In total, we observed NEK1 risk variants in nearly 3% of ALS cases. NEK1 has been linked to several cellular functions, including cilia formation, DNA-damage response, microtubule stability, neuronal morphology and axonal polarity. Our results provide new and important insights into ALS etiopathogenesis and genetic etiology.

To elucidate the genetic architecture of amyotrophic lateral sclerosis (ALS) and find associated loci, we assembled a custom imputation reference panel from whole-genome-sequenced patients with ALS and matched controls (n = 1,861). Through imputation and mixed-model association analysis in 12,577 cases and 23,475 controls, combined with 2,579 cases and 2,767 controls in an independent replication cohort, we fine-mapped a new risk locus on chromosome 21 and identified C21orf2 as a gene associated with ALS risk. In addition, we identified MOBP and SCFD1 as new associated risk loci. We established evidence of ALS being a complex genetic trait with a polygenic architecture. Furthermore, we estimated the SNP-based heritability at 8.5%, with a distinct and important role for low-frequency variants (frequency 1-10%). This study motivates the interrogation of larger samples with full genome coverage to identify rare causal variants that underpin ALS risk.

The H63D polymorphism in HFE has frequently been associated with susceptibility to amyotrophic lateral sclerosis (ALS). Regarding the role of HFE in iron homeostasis, iron accumulation is considered an important process in ALS. Furthermore, novel therapeutic strategies are being developed targeting this process. Evidence for this genetic association is, however, limited to several small studies. For this reason we studied the H63D polymorphism in a large European cohort including 3962 ALS patients and 5072 control subjects from 7 countries. After meta-analysis of previous studies and current findings we conclude that the H63D polymorphism in HFE is not associated with susceptibility to ALS, age at disease onset, or survival., (Copyright © 2013 Elsevier Inc. All rights reserved.)

Mutations in TAR DNA-binding protein (TARDBP) are associated with heterogenic phenotypes, including amyotrophic lateral sclerosis, frontotemporal dementia, and Parkinson's disease. In this study, we investigated the presence of TARDBP mutations in a cohort of 429 Dutch patients with Parkinson's disease. Though we detected 1 silent mutation, p.S332S, no missense mutations were present in our cohort. Our findings, therefore, demonstrate that TARDBP mutations do not appear to contribute to the pathogenesis of Parkinson's disease in The Netherlands., (Copyright © 2013 Elsevier Inc. All rights reserved.)

Amyotrophic lateral sclerosis (ALS) is a severe neurodegenerative disease that causes progressive muscle weakness, eventually resulting in death because of respiratory failure. Genetic variants are thought to predispose to the disease. A recent, large, genome-wide association study identified 2 loci that increase susceptibility to ALS. These 2 loci on chromosomes 9 and 19 consist of 4 genes: UNC13a, IFNK, MOBKL2b, and C9ORF72. A hexanucleotide repeat expansion in the noncoding region of C9ORF72 was recently identified as the cause of chromosome 9-linked ALS-FTD (frontotemporal dementia). In this study, our aim was to determine whether the coding regions of these genes harbor rare, nonsynonymous variants that play a role in ALS pathogenesis. In DNA from 1019 sporadic ALS patients and 1103 control subjects of Dutch descent, we performed a mutation screening analysis in the coding region of these 4 genes by resequencing the exons. A total of 16 amino acid-changing rare variations were identified, 11 in UNC13a and 5 on chromosome 9. Some of these were unique to ALS, but were detected in a single patient. None of the genes showed significant enrichment of rare variants in the coding sequence. Rare variants in the coding region of UNC13a, IFNK, MOBKL2b, and C9ORF72 are unlikely to be a genetic cause of ALS., (Copyright © 2013 Elsevier Inc. All rights reserved.)

Amyotrophic lateral sclerosis (ALS) is the third most common adult-onset neurodegenerative disease. Individuals with ALS rapidly progress to paralysis and die from respiratory failure within 3 to 5 years after symptom onset. Epidemiological factors explain only a modest amount of the risk for ALS. However, there is growing evidence of a strong genetic component to both familial and sporadic ALS risk. The International Consortium on Amyotrophic Lateral Sclerosis Genetics was established to bring together existing genome-wide association cohorts and identify sporadic ALS susceptibility and age at symptom onset loci. Here, we report the results of a meta-analysis of the International Consortium on Amyotrophic Lateral Sclerosis Genetics genome-wide association samples, consisting of 4243 ALS cases and 5112 controls from 13 European ancestry cohorts from across the United States and Europe. Eight genomic regions provided evidence of association with ALS, including 9p21.2 (rs3849942, odds ratio [OR] = 1.21; p = 4.41 × 10(-7)), 17p11.2 (rs7477, OR = 1.30; p = 2.89 × 10(-7)), and 19p13 (rs12608932, OR = 1.37, p = 1.29 × 10(-7)). Six genomic regions were associated with age at onset of ALS. The strongest evidence for an age of onset locus was observed at 1p34.1, with comparable evidence at rs3011225 (R(2)(partial) = 0.0061; p = 6.59 × 10(-8)) and rs803675 (R(2)(partial) = 0.0060; p = 6.96 × 10(-8)). These associations were consistent across all 13 cohorts. For rs3011225, individuals with at least 1 copy of the minor allele had an earlier average age of onset of over 2 years. Identifying the underlying pathways influencing susceptibility to and age at onset of ALS may provide insight into the pathogenic mechanisms and motivate new pharmacologic targets for this fatal neurodegenerative disease., (Copyright © 2013 Elsevier Inc. All rights reserved.)

Previously, we have reported amyotrophic lateral sclerosis (ALS) families with multiple mutations in major ALS-associated genes. These findings provided evidence for an oligogenic basis of ALS. In our present study, we screened a cohort of 755 sporadic ALS patients, 111 familial ALS patients (97 families), and 765 control subjects of Dutch descent for mutations in vesicle-associated membrane protein B (VAPB). We have identified 1 novel VAPB mutation (p.V234I) in a familial ALS patient known to have a chromosome 9 open reading frame 72 (C9orf72) repeat expansion. This p.V234I mutation was absent in control subjects, located in a region with high evolutionary conservation, and predicted to have damaging effects. Taken together, these findings provide additional evidence for an oligogenic basis of ALS., (Copyright © 2012 Elsevier Inc. All rights reserved.)

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disorder with a substantial heritable component. In pedigrees affected by its familial form, incomplete penetrance is often observed. We hypothesized that this could be caused by a complex inheritance of risk variants in multiple genes. Therefore, we screened 111 familial ALS (FALS) patients from 97 families, and large cohorts of sporadic ALS (SALS) patients and control subjects for mutations in TAR DNA-binding protein (TARDBP), fused in sarcoma/translated in liposarcoma (FUS/TLS), superoxide dismutase-1 (SOD1), angiogenin (ANG) and chromosome 9 open reading frame 72 (C9orf72). Mutations were identified in 48% of FALS families, 8% of SALS patients and 0.5% of control subjects. In five of the FALS families, we identified multiple mutations in ALS-associated genes. We detected FUS/TLS and TARDBP mutations in combination with ANG mutations, and C9orf72 repeat expansions with TARDBP, SOD1 and FUS/TLS mutations. Statistical analysis demonstrated that the presence of multiple mutations in FALS is in excess of what is to be expected by chance (P = 1.57 × 10(-7)). The most compelling evidence for an oligogenic basis was found in individuals with a p.N352S mutation in TARDBP, detected in five FALS families and three apparently SALS patients. Genealogical and haplotype analyses revealed that these individuals shared a common ancestor. We obtained DNA of 14 patients with this TARDBP mutation, 50% of whom had an additional mutation (ANG, C9orf72 or homozygous TARDBP). Hereby, we provide evidence for an oligogenic aetiology of ALS. This may have important implications for the interpretation of whole exome/genome experiments designed to identify new ALS-associated genes and for genetic counselling, especially of unaffected family members.

Polymorphisms in the paraoxonase family (PON) have been reported in patients with amyotrophic lateral sclerosis (ALS), but a recent meta-analysis did not show a clear association. Recently, PON mutations have also been identified in ALS patients. In this study, we assessed the frequency of PON variants in 1118 sporadic ALS patients, 93 familial ALS patients, and 1240 control subjects of Dutch descent. We identified PON mutations in 1.4% of sporadic ALS patients, 2.1% of familial ALS patients, and 2.5% of control subjects. There were no significant differences in mutational burden for rare variants or in allele frequencies of polymorphisms between patients and control subjects. Thus, this study does not support the premise that mutations or polymorphisms in PON contribute to ALS susceptibility., (Copyright © 2012 Elsevier Inc. All rights reserved.)

Optineurin (OPTN) mutations have been reported in a cohort of Japanese patients with familial (FALS) and sporadic (SALS) amyotrophic lateral sclerosis. In Caucasian patients, OPTN mutations have been identified in FALS patients, but were not detected in a cohort of 95 SALS patients. Moreover, single nucleotide polymorphisms (SNPs) in OPTN that could raise amyotrophic lateral sclerosis (ALS) susceptibility have not been investigated. Therefore, we screened a large Dutch cohort of 1191 patients with SALS, 94 patients with FALS, and 1415 control subjects for mutations and SNPs in OPTN. We identified 1 novel nonsense mutation (Q165X) and 1 unreported missense mutation (Q454E) in individual SALS patients. These patients demonstrated rapid disease progression with an average survival of 24.5 months. No heterozygous or homozygous OPTN mutations were identified in our cohort of FALS patients. SNP analysis did not reveal significant differences between ALS patients and control subjects. Therefore, variations in OPTN appear to be a rare cause of rapidly progressive SALS in the Netherlands., (Copyright © 2012. Published by Elsevier Inc.)

A large genome-wide screen in patients with sporadic amyotrophic lateral sclerosis (ALS) showed that the common variant rs12608932 in gene UNC13A was associated with disease susceptibility. UNC13A regulates the release of neurotransmitters, including glutamate. Genetic risk factors that, in addition, modify survival, provide promising therapeutic targets in ALS, a disease whose etiology remains largely elusive. We examined whether UNC13A was associated with survival of ALS patients in a cohort of 450 sporadic ALS patients and 524 unaffected controls from a population-based study of ALS in The Netherlands. Additionally, survival data were collected from individuals of Dutch, Belgian, or Swedish descent (1767 cases, 1817 controls) who had participated in a previously published genome-wide association study of ALS. We related survival to rs12608932 genotype. In both cohorts, the minor allele of rs12608932 in UNC13A was not only associated with susceptibility but also with shorter survival of ALS patients. Our results further corroborate the role of UNC13A in ALS pathogenesis., (Copyright © 2012 Elsevier Inc. All rights reserved.)

Excitotoxicity is thought to play a pathogenic role in amyotrophic lateral sclerosis (ALS). Excitotoxic motor neuron death is mediated through the Ca(2+)-permeable α-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA)-type of glutamate receptors and Ca(2+) permeability is determined by the GluR2 subunit. We investigated whether polymorphisms or mutations in the GluR2 gene (GRIA2) predispose patients to ALS. Upon sequencing 24 patients and 24 controls no nonsynonymous coding variants were observed but 24 polymorphisms were identified, 9 of which were novel. In a screening set of 310 Belgian ALS cases and 794 healthy controls and a replication set of 3157 cases and 5397 controls from 6 additional populations no association with susceptibility, age at onset, or disease duration was observed. We conclude that polymorphisms in the GluR2 gene (GRIA2) are not a major contributory factor in the pathogenesis of ALS., (Copyright © 2012 Elsevier Inc. All rights reserved.)

Objective: Several studies have suggested an increased frequency of variants in the gene encoding angiogenin (ANG) in patients with amyotrophic lateral sclerosis (ALS). Interestingly, a few ALS patients carrying ANG variants also showed signs of Parkinson disease (PD). Furthermore, relatives of ALS patients have an increased risk to develop PD, and the prevalence of concomitant motor neuron disease in PD is higher than expected based on chance occurrence. We therefore investigated whether ANG variants could predispose to both ALS and PD., Methods: We reviewed all previous studies on ANG in ALS and performed sequence experiments on additional samples, which allowed us to analyze data from 6,471 ALS patients and 7,668 controls from 15 centers (13 from Europe and 2 from the USA). We sequenced DNA samples from 3,146 PD patients from 6 centers (5 from Europe and 1 from the USA). Statistical analysis was performed using the variable threshold test, and the Mantel-Haenszel procedure was used to estimate odds ratios., Results: Analysis of sequence data from 17,258 individuals demonstrated a significantly higher frequency of ANG variants in both ALS and PD patients compared to control subjects (p = 9.3 × 10(-6) for ALS and p = 4.3 × 10(-5) for PD). The odds ratio for any ANG variant in patients versus controls was 9.2 for ALS and 6.7 for PD., Interpretation: The data from this multicenter study demonstrate that there is a strong association between PD, ALS, and ANG variants. ANG is a genetic link between ALS and PD., (Copyright © 2011 American Neurological Association.)

Previously, we reported germline DNA variants associated with risk of urinary bladder cancer (UBC) in Dutch and Icelandic subjects. Here we expanded the Icelandic sample set and tested the top 20 markers from the combined analysis in several European case-control sample sets, with a total of 4,739 cases and 45,549 controls. The T allele of rs798766 on 4p16.3 was found to associate with UBC (odds ratio = 1.24, P = 9.9 x 10(-12)). rs798766 is located in an intron of TACC3, 70 kb from FGFR3, which often harbors activating somatic mutations in low-grade, noninvasive UBC. Notably, rs798766[T] shows stronger association with low-grade and low-stage UBC than with more aggressive forms of the disease and is associated with higher risk of recurrence in low-grade stage Ta tumors. The frequency of rs798766[T] is higher in Ta tumors that carry an activating mutation in FGFR3 than in Ta tumors with wild-type FGFR3. Our results show a link between germline variants, somatic mutations of FGFR3 and risk of UBC.

Objectives: To assess the frequency of FUS mutations in 52 probands with familial amyotrophic lateral sclerosis (FALS) and to provide careful documentation of clinical characteristics., Design: FUS mutation analysis was performed using capillary sequencing on all coding regions of the gene in a cohort of patients with FALS. The clinical characteristics of patients carrying FUS mutations were described in detail., Setting: Three university hospitals in the Netherlands (referral centers for neuromuscular diseases)., Patients: Fifty-two probands from unrelated pedigrees with FALS., Main Outcome Measure: FUS mutations., Results: We identified 3 mutations in 4 of 52 probands. We observed 2 previously identified mutations (p.Arg521Cys and p.Arg521His) and 1 novel mutation (p.Ser462Phe). In addition, a p.Gln210His polymorphism was identified in 1 proband and 3 healthy control subjects. Phenotypic analysis demonstrated that patients may lack upper motor neuron signs, which was confirmed at autopsy, and disease survival was short (<36 months for 8 of 10 patients)., Conclusions: We discovered FUS mutations in Dutch patients with FALS and the occurrence of benign variations in the gene. Therefore, caution is warranted when interpreting results in a clinical setting. Although the phenotype associated with FUS mutations is variable, most patients predominantly demonstrate loss of lower motor neurons and have short disease survival.

A genome-wide association study (GWAS) using pooled DNA samples from 386 sporadic ALS patients and 542 controls from the USA, identified genetic variation in FGGY (FLJ10986) as a risk factor, as well as 66 additional candidate SNPs. Considering the large number of hypotheses that are tested in GWAS, independent replication of associations is crucial for identifying true-positive genetic risk factors for disease. The primary aim of this study was to study the association between FGGY and sporadic ALS in large, homogeneous populations from northern Europe. Genotyping experiments were performed using Illumina Beadchips, Sequenom iPLEX assays and Taqman technology on large case-control series from The Netherlands, Belgium, Sweden and Ireland (total: 1883 sporadic ALS patients and 2063 controls). No significant association between sporadic ALS and the six previously reported associated SNPs in FGGY was observed: rs6700125 (p =0.56), rs6690993 (p =0.30), rs10493256 (p =0.68), rs6587852 (p =0.64), rs1470407 (p =0.28) and rs333662 (p =0.44). Screening of the additional candidate loci did not yield significant associations either, with the lowest p-value in joint analysis for rs7772593 (p =0.14). We concluded that common genetic variation in FGGY is not associated with susceptibility to sporadic ALS in genetically homogeneous populations from northern Europe.

The recent identification of copy-number variation in the human genome has opened up new avenues for the discovery of positional candidate genes underlying complex genetic disorders, especially in the field of psychiatric disease. One major challenge that remains is pinpointing the susceptibility genes in the multitude of disease-associated loci. This challenge may be tackled by reconstruction of functional gene-networks from the genes residing in these loci. We applied this approach to autism spectrum disorder (ASD), and identified the copy-number changes in the DNA of 105 ASD patients and 267 healthy individuals with Illumina Humanhap300 Beadchips. Subsequently, we used a human reconstructed gene-network, Prioritizer, to rank candidate genes in the segmental gains and losses in our autism cohort. This analysis highlighted several candidate genes already known to be mutated in cognitive and neuropsychiatric disorders, including RAI1, BRD1, and LARGE. In addition, the LARGE gene was part of a sub-network of seven genes functioning in glycobiology, present in seven copy-number changes specifically identified in autism patients with limited co-morbidity. Three of these seven copy-number changes were de novo in the patients. In autism patients with a complex phenotype and healthy controls no such sub-network was identified. An independent systematic analysis of 13 published autism susceptibility loci supports the involvement of genes related to glycobiology as we also identified the same or similar genes from those loci. Our findings suggest that the occurrence of genomic gains and losses of genes associated with glycobiology are important contributors to the development of ASD.

We identified a SNP in the DPP6 gene that is consistently strongly associated with susceptibility to amyotrophic lateral sclerosis (ALS) in different populations of European ancestry, with an overall P value of 5.04 x 10(-8) in 1,767 cases and 1,916 healthy controls and with an odds ratio of 1.30 (95% confidence interval (CI) of 1.18-1.43). Our finding is the first report of a genome-wide significant association with sporadic ALS and may be a target for future functional studies.

Background: Amyotrophic lateral sclerosis (ALS) is a devastating disease characterised by progressive degeneration of motor neurons in the brain and spinal cord. ALS is thought to be multifactorial, with both environmental and genetic causes. Our aim was to identify genetic variants that predispose for sporadic ALS., Methods: We did a three-stage genome-wide association study in 461 patients with ALS and 450 controls from The Netherlands, using Illumina 300K single-nucleotide polymorphism (SNP) chips. The SNPs that were most strongly associated with ALS were analysed in a further 876 patients and 906 controls in independent sample series from The Netherlands, Belgium, and Sweden. We also investigated the possible pathological functions of associated genes using expression data from whole blood of patients with sporadic ALS and of control individuals who were included in the genome-wide association study., Findings: A genetic variant in the inositol 1,4,5-triphosphate receptor 2 gene (ITPR2) was associated with ALS (p=0.012 after Bonferroni correction). Combined analysis of all samples (1337 patients and 1356 controls) confirmed this association (p=3.28x10(-6), odds ratio 1.58, 95% CI 1.30-1.91). ITPR2 expression was greater in the peripheral blood of 126 ALS patients than in that of 126 healthy controls (p=0.00016)., Interpretation: Genetic variation in ITPR2 is a susceptibility factor for ALS. ITPR2 is a strong candidate susceptibility gene for ALS because it is involved in glutamate-mediated neurotransmission, is one of the main regulators of intracellular calcium concentrations, and has an important role in apoptosis.

Genome-wide association studies have been successful in identifying common variants that influence the susceptibility to complex diseases. From these studies, it has emerged that there is substantial overlap in susceptibility loci between diseases. In line with those findings, we hypothesized that shared genetic pathways may exist between multiple sclerosis (MS) and amyotrophic lateral sclerosis (ALS). While both diseases may have inflammatory and neurodegenerative features, epidemiological studies have indicated an increased co-occurrence within individuals and families. To this purpose, we combined genome-wide data from 4088 MS patients, 3762 ALS patients and 12 030 healthy control individuals in whom 5 440 446 single-nucleotide polymorphisms (SNPs) were successfully genotyped or imputed. We tested these SNPs for the excess association shared between MS and ALS and also explored whether polygenic models of SNPs below genome-wide significance could explain some of the observed trait variance between diseases. Genome-wide association meta-analysis of SNPs as well as polygenic analyses fails to provide evidence in favor of an overlap in genetic susceptibility between MS and ALS. Hence, our findings do not support a shared genetic background of common risk variants in MS and ALS.

Amyotrophic lateral sclerosis (ALS) is a progressive, neurodegenerative disease characterized by loss of upper and lower motor neurons. ALS is considered to be a complex trait and genome-wide association studies (GWAS) have implicated a few susceptibility loci. However, many more causal loci remain to be discovered. Since it has been shown that genetic variants associated with complex traits are more likely to be eQTLs than frequency-matched variants from GWAS platforms, we conducted a two-stage genome-wide screening for eQTLs associated with ALS. In addition, we applied an eQTL analysis to finemap association loci. Expression profiles using peripheral blood of 323 sporadic ALS patients and 413 controls were mapped to genome-wide genotyping data. Subsequently, data from a two-stage GWAS (3,568 patients and 10,163 controls) were used to prioritize eQTLs identified in the first stage (162 ALS, 207 controls). These prioritized eQTLs were carried forward to the second sample with both gene-expression and genotyping data (161 ALS, 206 controls). Replicated eQTL SNPs were then tested for association in the second-stage GWAS data to find SNPs associated with disease, that survived correction for multiple testing. We thus identified twelve cis eQTLs with nominally significant associations in the second-stage GWAS data. Eight SNP-transcript pairs of highest significance (lowest p = 1.27 × 10(-51)) withstood multiple-testing correction in the second stage and modulated CYP27A1 gene expression. Additionally, we show that C9orf72 appears to be the only gene in the 9p21.2 locus that is regulated in cis, showing the potential of this approach in identifying causative genes in association loci in ALS. This study has identified candidate genes for sporadic ALS, most notably CYP27A1. Mutations in CYP27A1 are causal to cerebrotendinous xanthomatosis which can present as a clinical mimic of ALS with progressive upper motor neuron loss, making it a plausible susceptibility gene for ALS.