Mutation analysis and immunopathological studies of PFN1 in familial and sporadic amyotrophic lateral sclerosis

Mutations in PFN1, a gene encoding the actin monomer-binding protein profilin 1, were recently reported in 1% to 2% of familial amyotrophic lateral sclerosis (ALS) patients. In vitro functional studies suggested that PFN1 mutations lead to ubiquitin-positive inclusions and impairment of cytoskeletal pathways. In the present study, mutation analysis of PFN1 was performed in an Australian cohort of 110 ALS families and 715 sporadic ALS patients. No PFN1 mutations were identified in familial ALS patients. Two rare non-synonymous variants (E117D and E117G) were found in sporadic ALS patients at similar incidences to that reported in public SNP databases. Immunostaining of PFN1 in sporadic ALS and familial ALS patients, including those with mutations in SOD1, FUS, UBQLN2 and C9ORF72, found no PFN1-positive inclusions in spinal motor neurons. Our data suggest that PFN1 mutations and pathology are not common in an Australian ALS cohort of predominantly European ancestry.     

Screening of CHCHD10 in a French cohort confirms the involvement of this gene in frontotemporal dementia with amyotrophic lateral sclerosis patients

Mutations in the CHCHD10 gene have been recently identified in a large family with a complex phenotype variably associating frontotemporal dementia (FTD) with amyotrophic lateral sclerosis (ALS), cerebellar ataxia, myopathy, and hearing impairment. CHCHD10 encodes a protein located in the mitochondrial intermembrane space and is likely involved in mitochondrial genome stability and maintenance of cristae junctions. However, the exact contribution of CHCHD10 in FTD and ALS diseases spectrum remains unknown. In this study, we evaluated the frequency of CHCHD10 mutations in 115 patients with FTD and FTD-ALS phenotypes. We identified 2 heterozygous variants in 3 unrelated probands presenting FTD and ALS, characterized by early and predominant bulbar symptoms. This study demonstrates the implication of CHCHD10 in FTD and ALS spectrum. Although the frequency of mutations is low in this series (2.6%), our work suggests that CHCHD10 mutations should be searched particularly when bulbar symptoms are present at onset.     

Screening of the TARDBP gene in familial and sporadic amyotrophic lateral sclerosis patients of Chinese origin

TAR DNA-binding protein (TARDBP) mutations have been reported in patients with amyotrophic lateral sclerosis (ALS) in different populations. Only a few studies have screened for TARDBP mutations in Chinese populations. Here, we sequenced the coding region of all five TARDBP exons for mutations in 13 familial ALS (FALS) pedigrees and 312 sporadic ALS (SALS) patients of Chinese origin, as well as 245 healthy control subjects. Two heterozygous missense mutations, c.875G>A (p.S292N) and c.1043G>T (p.G348V), were identified in two and one SALS patients, respectively. One synonymous substitution, c.1098C>G (p.A366A), was identified in two SALS patients. None of the substitutions were found in healthy control subjects. In Chinese populations, the estimated frequency of TARDBP mutations in SALS patients (0.73%) is higher than Japanese and lower than White populations, whereas the estimated mutation frequency in superoxide dismutase 1 (SOD1)-negative FALS patients (15.2%) is higher than both Japanese and White populations. Our findings provide an overview of the occurrence of TARDBP mutations in Chinese ALS patients and highlight the importance of TARDBP mutation screening in Chinese ALS patients.     

Genetic analysis of matrin 3 gene in French amyotrophic lateral sclerosis patients and frontotemporal lobar degeneration with amyotrophic lateral sclerosis patients

Amyotrophic lateral sclerosis (ALS) and frontotemporal lobar degeneration (FTLD) are adult-onset neurodegenerative diseases with overlapping clinical characteristics. They share common genetic causes and pathologic hallmarks such as TDP-43 neuronal accumulations. Recently, exome analysis identified mutations in matrin 3 (MATR3) gene in patients with familial ALS, suggesting a role for this gene in the pathogenesis of the disease. MATR3 is a nuclear matrix protein with DNA and RNA binding domains that interacts with TDP-43. To confirm the contribution of MATR3 to ALS, we studied a French cohort of 153 familial ALS or ALS/FTLD patients, without finding any variant. We conclude that mutations in MATR3 are rare in French familial ALS and ALS with FTLD patients.     

VCP mutations in familial and sporadic amyotrophic lateral sclerosis

Mutations in the valosin-containing protein (VCP) gene were recently reported to be the cause of 1%-2% of familial amyotrophic lateral sclerosis (ALS) cases. VCP mutations are known to cause inclusion body myopathy (IBM) with Paget's disease (PDB) and frontotemporal dementia (FTD). The presence of VCP mutations in patients with sporadic ALS, sporadic ALS-FTD, and progressive muscular atrophy (PMA), a known clinical mimic of inclusion body myopathy, is not known. To determine the identity and frequency of VCP mutations we screened a cohort of 93 familial ALS, 754 sporadic ALS, 58 sporadic ALS-FTD, and 264 progressive muscular atrophy patients for mutations in the VCP gene. Two nonsynonymous mutations were detected; 1 known mutation (p.R159H) in a patient with familial ALS with several family members suffering from FTD, and 1 mutation (p.I114V) in a patient with sporadic ALS. Conservation analysis and protein prediction software indicate the p.I114V mutation to be a rare benign polymorphism. VCP mutations are a rare cause of familial ALS. The role of VCP mutations in sporadic ALS, if present, appears limited.     

Novel optineurin mutations in sporadic amyotrophic lateral sclerosis patients

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.     

Analysis of the SORT1 gene in familial amyotrophic lateral sclerosis

Background

Substantial efforts have been deployed in the past decade to identify the genetic causes of amyotrophic lateral sclerosis (ALS), and we hypothesized here that mutations in SORT1 or aberrant SORT1 splicing reduce progranulin level and promote neurodegeneration.

Methods

We sequenced the coding exons of SORT1 in a cohort of 112 unrelated individuals with familial ALS. We also tested for aberrant SORT1 splicing by RT-PCR using RNA samples from cell lines expressing six different ALS-associated TARDBP mutations.

Results

We identified one unique missense and two unique silent mutations in our cohort. None are predicted to have functional effects. No aberrant SORT1 splicing event was observed.

Conclusions

SORT1 mutations are not a common cause of familial ALS, and the influence of TARDBP mutations on SORT1 splicing still needs to be clarified.     

Mutation analysis of VCP in familial and sporadic amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disorder characterized by the progressive loss of motor neurons in the motor cortex, brain stem and spinal cord. Mutations in the valosin-containing protein gene (VCP) were recently described in ALS families. Some of these families included diagnoses of other clinical features including frontotemporal dementia, Paget's disease, inclusion body myopathy, Parkinsonism and limb weakness. We sought to determine the prevalence of VCP mutations in Australian familial (n = 131) and sporadic (n = 48) ALS cohorts diagnosed with classic ALS. No mutations were identified indicating that VCP mutations are not a common cause of classic ALS among Australian cases with predominantly European ancestry.     

TARDBP gene mutations among Chinese patients with sporadic amyotrophic lateral sclerosis

Recently, several TARDBP mutations have been identified in sporadic amyotrophic lateral sclerosis (SALS) patients among different ethnicities. Our study aims to analyze the clinical features and mutations in the TARDBP gene among Chinese patients with SALS. One hundred sixty-five patients were studied. The mean age of onset was 50.8±12.0 years. The mean diagnostic delay was 18.8±17.1 months. A novel missense mutation (p.N378S) and a novel silent change (p.A321A) were detected in 2 male patients, respectively. A new variant of c.1098C>G in exon 6 and 2 reported variants, g.IVS1+85C>T in intron 1 and c.57A>G in exon 2, were found. The frequency of the “G” variant of c.57A>G in exon 2 and the “G” variant of c.1098C>G in exon 6 were significantly lower in the patient group than in the control (p=0.001 and p=0.024, respectively). Our findings provide first evidence that the frequency of TARDBP gene mutations is rare among Chinese SALS patients (0.61%). Several polymorphisms may influence susceptibility to amyotrophic lateral sclerosis.     

Familial amyotrophic lateral sclerosis,dementia, and psychosis

Reports of amyotrophic lateral sclerosis (ALS) associated with dementia in families outside the Western Pacific have been rare. The authors present a neuropsychiatric survey of three generations of a family with adult-onset ALS with dementia and psychosis in each generation. Among the interesting findings were possible genetic links due to regional inbreeding and a consanguineous marriage     

Association of the hOGG1 Ser326Cys polymorphism with sporadic amyotrophic lateral sclerosis

Amyotropic lateral sclerosis (ALS) is a fatal and progressive neurodegenerative disease causing the loss of motoneurons of the brain and the spinal cord. The etiology of ALS is still uncertain, but males are at increased risk for the disease than females. Several studies have suggested that motoneurons in ALS might be subjected to the double insult of increased DNA oxidative damage and deficiencies in DNA repair systems. Particularly, increased levels of 8-oxoguanine and impairments of the DNA base excision repair system have been observed in neurons of ALS patients. There is evidence that the Ser326Cys polymorphism of the human 8-oxoguanine DNA glycosylase 1 (hOGG1) gene is associated with a reduced DNA repair activity. To evaluate the role of the hOGG1 Ser326Cys polymorphism in sporadic ALS (sALS), we screened 136 patients and 129 matched controls. In the total population, we observed association between both the Cys326 allele (p=0.02) and the combined Ser326Cys+Cys326Cys genotype (OR=1.65, 95% CI=1.06-2.88) and increased risk of disease. After stratification by gender, the Cys326 allele (p=0.01), both the Ser326Cys genotype (OR=2.14, 95% CI=1.09-4.19) and the combined Ser326Cys+Cys326Cys genotype (OR=2.15, 95% CI=1.16-4.01) were associated with sALS risk only in males. No significant association between the Ser326Cys polymorphism and disease phenotype, including age and site of onset and disease progression, was observed. Present results suggest a possible involvement of the hOGG1 Ser326Cys polymorphism in sALS pathogenesis.     

De novo truncating FUS gene mutation as a cause of sporadic amyotrophic lateral sclerosis

Mutations in the gene encoding fused in sarcoma (FUS) were recently identified as a novel cause of amyotrophic lateral sclerosis (ALS), emphasizing the genetic heterogeneity of ALS. We sequenced the genes encoding superoxide dismutase (SOD1), TAR DNA‐binding protein 43 (TARDBP) and FUS in 99 sporadic and 17 familial ALS patients ascertained at Mayo Clinic. We identified two novel mutations in FUS in two out of 99 (2.0%) sporadic ALS patients and established the de novo occurrence of one FUS mutation. In familial patients, we identified three (17.6%) SOD1 mutations, while FUS and TARDBP mutations were excluded. The de novo FUS mutation (g.10747A>G; IVS13‐2A>G) affects the splice‐acceptor site of FUS intron 13 and was shown to induce skipping of FUS exon 14 leading to the C‐terminal truncation of FUS (p.G466VfsX14). Subcellular localization studies showed a dramatic increase in the cytoplasmic localization of FUS and a reduction of normal nuclear expression in cells transfected with truncated compared to wild‐type FUS. We further identified a novel in‐frame insertion/deletion mutation in FUS exon 12 (p.S402_P411delinsGGGG) which is predicted to expand a conserved poly‐glycine motif. Our findings extend the mutation spectrum in FUS leading to ALS and describe the first de novo mutation in FUS. © 2010 Wiley‐Liss, Inc.     

Mutations in the HFE gene and sporadic amyotrophic lateral sclerosis risk: a meta-analysis of observational studies

Iron homeostasis dysregulation has been regarded as an important mechanism in neurodegenerative diseases. The H63D and C282Y polymorphisms in the HFE gene may be involved in the development of sporadic amyotrophic lateral sclerosis (ALS) through the disruption of iron homeostasis. However, studies investigating the relationship between ALS and these two polymorphisms have yielded contradictory outcomes. We performed a meta-analysis to assess the roles of the H63D and C282Y polymorphisms of HFE in ALS susceptibility. PubMed, MEDLINE, EMBASE, and Cochrane Library databases were systematically searched to identify relevant studies. Strict selection criteria and exclusion criteria were applied. Odds ratios (ORs) with 95% confidence intervals (CIs) were used to assess the strength of associations. A fixed- or random-effect model was selected, depending on the results of the heterogeneity test. Fourteen studies were included in the meta-analysis (six studies with 1692 cases and 8359 controls for C282Y; 14 studies with 5849 cases and 13,710 controls for H63D). For the C282Y polymorphism, significant associations were observed in the allele model (Y vs C: OR=0.76, 95%CI=0.62-0.92, P=0.005) and the dominant model (YY+CY vs CC: OR=0.75, 95%CI=0.61-0.92, P=0.006). No associations were found for any genetic model for the H63D polymorphism. The C282Y polymorphism in HFE could be a potential protective factor for ALS in Caucasians. However, the H63D polymorphism does not appear to be associated with ALS.     

An explanation for the changes in collagen in sporadic amyotrophic lateral sclerosis

There is evidence showing abnormalities in collagen from the skin of patients with sporadic Amyotrophic Lateral Sclerosis (sALS) both from Guam and elsewhere. The non-proteinogenic amino acid beta-N-methylamino-l-alanine (BMAA) was first associated with the high incidence of Amyotrophic Lateral Sclerosis/Parkinsonism Dementia Complex (ALS/PDC) in Guam, and has been implicated as a potential environmental factor in ALS and other neurodegenerative diseases. BMAA has a number of toxic effects on motor neurons including direct agonist action on NMDA and AMPA receptors, induction of oxidative stress, and depletion of glutathione. As a non-proteinogenic amino acid, there is also the strong possibility that BMAA could cause intraneuronal protein misfolding, the hallmark of neurodegeneration. While an animal model for BMAA-induced ALS is lacking, there is substantial evidence to support a link between this toxin and ALS. We hypothesize that the abnormalities seen in sALS collagen may result from the misincorporation of BMAA and subsequent misfolding of the collagen protein.     

Screening of OPTN in French familial amyotrophic lateral sclerosis

Mutations in OPTN gene encoding optineurin have recently been identified at the homozygote and heterozygote state in Japanese families with slowly progressive amyotrophic lateral sclerosis (ALS). OPTN had previously been involved in adult primary open angle glaucoma (POAG). We sequenced the coding exons of OPTN in 126 French patients with familial ALS (FALS). We identified, at the heterozygote state, the nonsense c.382_383insAG variant (also called 691_692insAG), alternatively reported as a causative mutation for primary open angle glaucoma (POAG) or a rare polymorphism and the new p.Arg96Leu variant in a family with dominant ALS. Western blot experiments on the patients' lymphoblasts showed that the former variant led to a loss of function and the latter did not cause protein accumulation. Our results do not confirm the contribution of OPTN in ALS.     

Valosin-containing protein (VCP) mutations in sporadic amyotrophic lateral sclerosis

We recently reported that mutations in the valosin-containing protein (VCP) gene are a cause of 1%-2% of familial amyotrophic lateral sclerosis (ALS) cases, but their role in the pathogenesis of sporadic ALS is unclear. We undertook mutational screening of VCP in 701 sporadic ALS cases. Three pathogenic variants (p.Arg159Cys, p.Asn387Thr, and p.R662C) were found in three U.S. cases, each of whom presented with progressive upper and lower motor neuron signs consistent with definite ALS by El Escorial diagnostic criteria. Our data indicate that VCP mutations may underlie apparently sporadic ALS but account for <1% of this form of disease.     

FUS mutations in sporadic amyotrophic lateral sclerosis: clinical and genetic analysis

Fused in sarcoma (FUS) or translocation in liposarcoma (TLS), a DNA/RNA-binding protein, causes a dominant autosomal inherited form of amyotrophic lateral sclerosis (ALS), ALS 6. Its main role in neurodegeneration is highlighted by the presence of cytoplasmic accumulation of its mutant protein form in ALS patients. To further define the frequency and spectrum of FUS gene mutations, we have performed a molecular screening of a cohort of 327 Italian patients from Southern Italy with sporadic ALS (SALS). We identified 4 patients carrying 3 different missense mutations and several polymorphisms. Two different substitutions occurring in the same amino acidic position have been observed in 2 patients: R521G and R521C respectively; P525L mutation has been found in 2 additional cases. Most of the patients with FUS mutations showed early symptom onset and had short disease survival. We also detected 4 different polymorphic variants (3'-untranslated region [UTR] variant, c.*41G>A; c.523+3ins[GAGGTG]; c.335-15del[TTTT]; and rs13331793) in 9 patients from within our cohort. This study underlines the importance of population-based mutation screening of newly identified genes.