Variance of age at onset in a Japanese family with amyotrophic lateral sclerosis associated with a novel Cu/Zn superoxide dismutase mutation

Profiling tofersen as a treatment of superoxide dismutase 1 amyotrophic lateral sclerosis

INTRODUCTION

Amyotrophic lateral sclerosis (ALS) is a rapidly progressive motor neuron disorder with a fatal outcome 3-5 years after disease onset due to respiratory complications. Superoxide dismutase 1 (SOD1) mutations are found in about 2% of all patients. Tofersen is a novel oligonucleotide antisense drug specifically developed to treat SOD1-ALS patients.

AREAS COVERED

Our review covers and discusses tofersen pharmacological properties and its phase I/II and III clinical trials results. Other available drugs and their limitations are also addressed.

EXPERT OPINION

VALOR study failed to meet the primary endpoint (change in the revised Amyotrophic Lateral Sclerosis Functional Rating Scale score from baseline to week 28, tofersen arm vs. placebo), but a significant reduction in plasma neurofilament light chain (NfL) levels was observed in tofersen arm (60% vs. 20%). PrefALS study has proposed plasma NfL has a potential biomarker for presymptomatic treatment, since it increases 6-12 months before phenoconversion. There is probably a delay between plasma NfL reduction and the clinical benefit. ATLAS study will allow more insights regarding tofersen clinical efficacy in disease progression rate, survival, and even disease onset delay in presymptomatic SOD1 carriers.

Yeast Models of Amyotrophic Lateral Sclerosis Type 8 Mimic Phenotypes Seen in Mammalian Cells Expressing Mutant VAPBP56S

Amyotrophic lateral sclerosis (ALS) is a complex neurodegenerative disease that results in the loss of motor neurons and can occur sporadically or due to genetic mutations. Among the 30 genes linked to familial ALS, a P56S mutation in VAPB, an ER-resident protein that functions at membrane contact sites, causes ALS type 8. Mammalian cells expressing VAPBP56S have distinctive phenotypes, including ER collapse, protein and/or membrane-containing inclusions, and sensitivity to ER stress. VAPB is conserved through evolution and has two homologs in budding yeast, SCS2 and SCS22. Previously, a humanized version of SCS2 bearing disease-linked mutations was described, and it caused Scs2-containing inclusions when overexpressed in yeast. Here, we describe a yeast model for ALS8 in which the two SCS genes are deleted and replaced with a single chromosomal copy of either wild-type or mutant yeast SCS2 or human VAPB expressed from the SCS2 promoter. These cells display ER collapse, the formation of inclusion-like structures, and sensitivity to tunicamycin, an ER stress-inducing drug. Based on the phenotypic similarity to mammalian cells expressing VAPBP56S, we propose that these models can be used to study the molecular basis of cell death or dysfunction in ALS8. Moreover, other conserved ALS-linked genes may create opportunities for the generation of yeast models of disease.

Genetics of amyotrophic lateral sclerosis: seeking therapeutic targets in the era of gene therapy

Amyotrophic lateral sclerosis (ALS) is an intractable disease that causes respiratory failure leading to mortality. The main locus of ALS is motor neurons. The success of antisense oligonucleotide (ASO) therapy in spinal muscular atrophy (SMA), a motor neuron disease, has triggered a paradigm shift in developing ALS therapies. The causative genes of ALS and disease-modifying genes, including those of sporadic ALS, have been identified one after another. Thus, the freedom of target choice for gene therapy has expanded by ASO strategy, leading to new avenues for therapeutic development. Tofersen for superoxide dismutase 1 (SOD1) was a pioneer in developing ASO for ALS. Improving protocols and devising early interventions for the disease are vital. In this review, we updated the knowledge of causative genes in ALS. We summarized the genetic mutations identified in familial ALS and their clinical features, focusing on SOD1, fused in sarcoma (FUS), and transacting response DNA-binding protein. The frequency of the C9ORF72 mutation is low in Japan, unlike in Europe and the United States, while SOD1 and FUS are more common, indicating that the target mutations for gene therapy vary by ethnicity. A genome-wide association study has revealed disease-modifying genes, which could be the novel target of gene therapy. The current status and prospects of gene therapy development were discussed, including ethical issues. Furthermore, we discussed the potential of axonal pathology as new therapeutic targets of ALS from the perspective of early intervention, including intra-axonal transcription factors, neuromuscular junction disconnection, dysregulated local translation, abnormal protein degradation, mitochondrial pathology, impaired axonal transport, aberrant cytoskeleton, and axon branching. We simultaneously discuss important pathological states of cell bodies: persistent stress granules, disrupted nucleocytoplasmic transport, and cryptic splicing. The development of gene therapy based on the elucidation of disease-modifying genes and early intervention in molecular pathology is expected to become an important therapeutic strategy in ALS.

Missense Mutations of Codon 116 in the SOD1 Gene Cause Rapid Progressive Familial ALS and Predict Short Viability With PMA Phenotype

Amyotrophic lateral sclerosis (ALS) is the most common form of motor neuron disease, characterized by a great variety of both clinical presentations and genetic causes. Previous studies had identified two different missense mutations in SOD1 (p.R116C and p.R116G) causing familial ALS. In this study, we report a novel heterozygous missense mutation in the SOD1 gene (p.R116S) in a family with inherited ALS manifested as fast-deteriorating pure lower motor neuron symptoms. The patient displayed similar clinical picture and prognostic value to previous reported cases with different R116 substitution mutations. Modeling of all R116 substitutions in the resolved SOD1 protein structure revealed a shared mechanism with destroyed hydrogen bonds between R116 and other two residues, which might lead to protein unfolding and oligomer formation, ultimately conferring neurotoxicity.

SOD1-related ALS with anticipation in a large family from Martinique

Amyotrophic Lateral Sclerosis (ALS) is a rare neurological disorder that causes degeneration of upper and lower motor neurons and their axons. ALS is mostly sporadic, but there are familial forms. In more than half of the familial forms, a pathogenic variant is found in one of the following genes: C9ORF72, SOD1, TDP-43, FUS, and VCP. SOD1 is the 2nd most common gene involved in genetic forms of ALS. Genotype-phenotype relationships are occasionally established in genetic forms of ALS associated with SOD1 mutations pathogenic variants. The c.281G > T (p.[G93V]) variant in SOD1 is associated with a rarely described and unexplained anticipation phenomenon. We report a large family from Martinique in whom ALS is associated with a c.281G > T (p.[G93V]) pathogenic variant in SOD1 and a statistically suggested anticipation. A whole-exome study and detection of CNVs (CoDESeq) from 3 affected members of this family revealed the presence of variants of uncertain signification (VUS) in other ALS genes. VUS in DCTN1 and NEFH were present in patients of the 2nd generation, and CNVs involving UBQLN2 and C21orf2 were found in the youngest case of the family.

Single copy/knock-in models of ALS SOD1 in C. elegans suggest loss and gain of function have different contributions to cholinergic and glutamatergic neurodegeneration

Mutations in Cu/Zn superoxide dismutase 1 (SOD1) lead to Amyotrophic Lateral Sclerosis (ALS), a neurodegenerative disease that disproportionately affects glutamatergic and cholinergic motor neurons. Previous work with SOD1 overexpression models supports a role for SOD1 toxic gain of function in ALS pathogenesis. However, the impact of SOD1 loss of function in ALS cannot be directly examined in overexpression models. In addition, overexpression may obscure the contribution of SOD1 loss of function in the degeneration of different neuronal populations. Here, we report the first single-copy, ALS knock-in models in C. elegans generated by transposon- or CRISPR/Cas9- mediated genome editing of the endogenous sod-1 gene. Introduction of ALS patient amino acid changes A4V, H71Y, L84V, G85R or G93A into the C. elegans sod-1 gene yielded single-copy/knock-in ALS SOD1 models. These differ from previously reported overexpression models in multiple assays. In single-copy/knock-in models, we observed differential impact of sod-1 ALS alleles on glutamatergic and cholinergic neurodegeneration. A4V, H71Y, G85R, and G93A animals showed increased SOD1 protein accumulation and oxidative stress induced degeneration, consistent with a toxic gain of function in cholinergic motor neurons. By contrast, H71Y, L84V, and G85R lead to glutamatergic neuron degeneration due to sod-1 loss of function after oxidative stress. However, dopaminergic and serotonergic neuronal populations were spared in single-copy ALS models, suggesting a neuronal-subtype specificity previously not reported in invertebrate ALS SOD1 models. Combined, these results suggest that knock-in models may reproduce the neurotransmitter-type specificity of ALS and that both SOD1 loss and gain of toxic function differentially contribute to ALS pathogenesis in different neuronal populations.

In all SOD1 ALS patients, cholinergic spinal motor neurons degenerate, but degeneration of cortical glutamatergic neurons is less common. Despite decades of work, it remains unclear why some disease alleles (e.g. A4V) primarily affect cholinergic spinal neurons, while other alleles affect both cholinergic and glutamatergic neurons. New genome editing techniques allowed us to create the first C. elegans knock-in/single-copy models for SOD1 ALS by directly editing the C. elegans sod-1 gene to recreate SOD1 amino acid changes that cause ALS in patients. These new models are complementary to previously described overexpression models, which revealed mutant SOD1 toxic gain of function properties. By contrast, in the new C. elegans knock-in models, we find that both loss and gain of sod-1 function contribute to neurodegeneration. C. elegans cholinergic motor neuron loss is primarily driven by toxic gain of function, but glutamatergic neuron loss is primarily driven by loss of function. Only cholinergic and glutamatergic neurons degenerate in C. elegans knock-in models; dopaminergic, serotoninergic and GABAergic neurons do not. This pattern of neuronal loss is reminiscent of the pattern of neuronal loss seen in SOD1 ALS patients. Strikingly, in the C. elegans A4V model, only cholinergic neurons are lost. Our results suggest that an underlying premise of the ALS field–that identical pathological mechanisms lead to degeneration of cholinergic and glutamatergic neurons–should be reconsidered. Mechanisms that predominantly drive glutamatergic and cholinergic neuron degeneration in ALS may not be identical.

Molecular epidemiological study of familial amyotrophic lateral sclerosis in Japanese population by whole-exome sequencing and identification of novel HNRNPA1 mutation

To elucidate the genetic epidemiology of familial amyotrophic lateral sclerosis (FALS) in the Japanese population, we conducted whole-exome sequencing analysis of 30 FALS families in whom causative mutations have not been identified in previous studies. Consequently, whole-exome sequencing analysis revealed novel mutations in HNRNPA1, TBK1, and VCP. Taken together with our previous results of mutational analyses by direct nucleotide sequencing analysis, a microarray-based resequencing method, or repeat-primed PCR analysis, causative mutations were identified in 41 of the 68 families (60.3%) with SOD1 being the most frequent cause of FALS (39.7%). Of the mutations identified in this study, a novel c.862/1018C>G (p.P288A/340A) mutation in HNRNPA1 located in the nuclear localization signal domain of hnRNPA1, enhances the recruitment of mutant hnRNPA1 into stress granules, indicating that an altered nuclear localization signal activity plays an essential role in amyotrophic lateral sclerosis pathogenesis.

Familial amyotrophic lateral sclerosis with an I104F mutation in the SOD1 gene: Multisystem degeneration with neurofilamentous aggregates and SOD1 inclusions

We previously reported familial amyotrophic lateral sclerosis (FALS) of 11 years duration in a 57-year-old woman, who received artificial ventilation for 5 years prior to death and exhibited widespread multisystem degeneration and neurofilamentous aggregates, so-called conglomerate inclusions (CIs). In the present study, we re-evaluated this autopsied patient (proband) with further immunohistochemical observation as well as mutational analysis of the superoxide dismutase 1 (SOD1) gene. A review of the clinical features of the proband's family revealed five affected members (including the proband) over two successive generations who showed marked variability in clinical presentation, such as the age at onset. The proband was found to harbor a heterozygous missense mutation in exon 4 (I104F) of the SOD1 gene. In the brain and spinal cord, SOD1-positive neuronal cytoplasmic inclusions (NCIs) were found to be more widely distributed than CIs, the latter being weakly positive for SOD1. No Lewy body-like hyaline inclusions were found. This is considered to be the first description of an autopsy case of FALS with an I104F SOD1 gene mutation, suggesting that combination of marked intra-familial clinical variability and multisystem degeneration with occurrence of CIs and SOD1-positive NCIs is a characteristic feature of FALS with this SOD1 gene mutation.

From animal models to human disease: a genetic approach for personalized medicine in ALS

Amyotrophic Lateral Sclerosis (ALS) is the most frequent motor neuron disease in adults. Classical ALS is characterized by the death of upper and lower motor neurons leading to progressive paralysis. Approximately 10 % of ALS patients have familial form of the disease. Numerous different gene mutations have been found in familial cases of ALS, such as mutations in superoxide dismutase 1 (SOD1), TAR DNA-binding protein 43 (TDP-43), fused in sarcoma (FUS), C9ORF72, ubiquilin-2 (UBQLN2), optineurin (OPTN) and others. Multiple animal models were generated to mimic the disease and to test future treatments. However, no animal model fully replicates the spectrum of phenotypes in the human disease and it is difficult to assess how a therapeutic effect in disease models can predict efficacy in humans. Importantly, the genetic and phenotypic heterogeneity of ALS leads to a variety of responses to similar treatment regimens. From this has emerged the concept of personalized medicine (PM), which is a medical scheme that combines study of genetic, environmental and clinical diagnostic testing, including biomarkers, to individualized patient care. In this perspective, we used subgroups of specific ALS-linked gene mutations to go through existing animal models and to provide a comprehensive profile of the differences and similarities between animal models of disease and human disease. Finally, we reviewed application of biomarkers and gene therapies relevant in personalized medicine approach. For instance, this includes viral delivering of antisense oligonucleotide and small interfering RNA in SOD1, TDP-43 and C9orf72 mice models. Promising gene therapies raised possibilities for treating differently the major mutations in familial ALS cases.

Familial clustering of ALS in a population-based resource

OBJECTIVE

To determine the extent of an inherited contribution to amyotrophic lateral sclerosis (ALS) mortality.

METHODS

Death certificates (DCs) from 1904 to 2009 were analyzed from patients with at least 3 generations recorded in the Utah Population Database, a genealogic and medical database of more than 2 million Utah residents. Among probands whose DCs listed ALS, the relative risk (RR) of death with ALS was determined among spouses and first- through fifth-degree relatives, using birth year-, sex-, and birthplace-matched cohorts.

RESULTS

Eight hundred seventy-three patients with ALS met the inclusion criteria. Among 3,531 deceased first-degree relatives of probands, the RR of dying with ALS was increased compared with control cohorts (RR = 4.91, 95% confidence interval 3.36, 6.94). The RR of dying with ALS was also increased among 9,386 deceased second-degree relatives (RR = 2.85, 95% confidence interval 2.06, 3.84). The RR of dying with ALS was not increased among third- through fifth-degree relatives. More affected first-degree relatives were male (p = 0.014). No cases of conjugal ALS were observed.

CONCLUSIONS

This study is suggestive of familial clustering in excess of expected for ALS. Our results confirm the results of prior studies of familial ALS, suggesting applicability of our findings to other mixed European populations. Furthermore, this work expands on previous studies by quantifying the RR of ALS among more distant relatives. The use of mortality data obtained from DCs reduces the ascertainment and recall bias of many previous studies. Finally, the excess of ALS among second-degree relatives and lack of conjugal ALS are strongly supportive of a genetic contribution.

Clinical features and Cu/Zn superoxide dismutase gene mutations in two mainland Chinese families with amyotrophic lateral sclerosis

Clinical information of two families with amyotrophic lateral sclerosis (ALS) was studied and a mutation analysis of the SOD1 gene was performed using direct DNA sequencing. Two previously reported mutations of the SOD1 gene, G20T (Cys6Phe substitution), and G255C (Leu84Phe substitution), were identified and cosegregated with the disease in the two families. Patients with a Cys6Phe mutation demonstrated rapid disease progression with severe clinical phenotypes, and the patients with a Leu84Phe mutation had a variety of different clinical phenotypes. This is the third report of SOD1 gene mutations in Mainland Chinese patients with different ALS phenotypes. This supports the hypothesis that the clinical course of ALS may vary depending on the specific genetic mutation.

Neuronal NOS is dislocated during muscle atrophy in amyotrophic lateral sclerosis

Previously, we demonstrated that neuronal nitric oxide synthase (nNOS) is activated and promotes muscle atrophy in skeletal muscle during tail suspension, a model of unloading and denervation. Here, we examined patients with amyotrophic lateral sclerosis (ALS) and mutant (H46R) SOD1 transgenic (Tg) mice model using immunohistochemistry, Western blotting and real time PCR. We found cytoplasmic nNOS staining of angulated muscle fibers in patients with ALS. We also examined mutant SOD1 Tg mice and found cytoplasmic nNOS staining even before the onset of clinical muscle atrophy. In the Tg mice, nNOS was largely extracted with 100 mM NaCl and barely detected in the pellet fraction, suggesting fragile anchoring of nNOS to the sarcolemma. We also showed an elevated expression of atrogin-1, key molecules in muscle atrophy at the end stage. A common nNOS dislocation/atrogin-1/muscle atrophy pathway among tail suspension, denervation and ALS is suggested. nNOS modulation therapy may be beneficial in several types of muscle atrophy.

Immature copper-zinc superoxide dismutase and familial amyotrophic lateral sclerosis

Mutations in human copper-zinc superoxide dismutase (SOD1) cause an inherited form of amyotrophic lateral sclerosis (ALS, Lou Gehrig's disease, motor neuron disease). Insoluble forms of mutant SOD1 accumulate in neural tissues of human ALS patients and in spinal cords of transgenic mice expressing these polypeptides, suggesting that SOD1-linked ALS is a protein misfolding disorder. Understanding the molecular basis for how the pathogenic mutations give rise to SOD1 folding intermediates, which may themselves be toxic, is therefore of keen interest. A critical step on the SOD1 folding pathway occurs when the copper chaperone for SOD1 (CCS) modifies the nascent SOD1 polypeptide by inserting the catalytic copper cofactor and oxidizing its intrasubunit disulfide bond. Recent studies reveal that pathogenic SOD1 proteins coming from cultured cells and from the spinal cords of transgenic mice tend to be metal-deficient and/or lacking the disulfide bond, raising the possibility that the disease-causing mutations may enhance levels of SOD1-folding intermediates by preventing or hindering CCS-mediated SOD1 maturation. This mini-review explores this hypothesis by highlighting the structural and biophysical properties of the pathogenic SOD1 mutants in the context of what is currently known about CCS structure and action. Other hypotheses as to the nature of toxicity inherent in pathogenic SOD1 proteins are not covered.

Hoarseness due to bilateral vocal cord paralysis as an initial manifestation of familial amyotrophic lateral sclerosis

Bulbar palsy is unusual as an initial manifestation of amyotrophic lateral sclerosis (ALS), although common in the advanced stages. In terms of bulbar palsy as a presenting symptom, dysarthria and dysphagia are of common features. Hoarseness, however, is an initial symptom of ALS in only a small number of patients. We report a 43-year-old female with hoarseness due to bilateral vocal cord paralysis as the first manifestation of ALS. Gene analysis revealed a heterozygous missense mutation in the SOD1 gene, which resulted in an amino acid substitution of isoleucine 149 by threonine. Hoarseness can be the initial symptom of ALS. Therefore, in cases of bilateral vocal cord paralysis of unknown etiology, ALS should be taken into consideration.

[Amyotrophic lateral sclerosis with the SOD1 mutations]

Mutations in Cu/Zn superoxide dismutase (SOD1) have been linked to some familial cases of amyotrophic lateral sclerosis (ALS). In familial ALS kinders with mutations in the SOD1 gene, the age of onset of weakness varies greatly but the duration of illness appears to be characteristic to each mutation. For example, in patients with the L84V mutation, the average life expectancy is less than 1.5 year after the onset of symptoms, whereas patients harboring the H46R mutation have an average life expectancy of 18 years after the disease onset. In view of the evidence supporting the idea that familial ALS variants of SOD1 enzymes acquire toxic properties, the variations in the duration of illness in the different kinders might arise because each mutation imparts different degrees of toxicity to the mutant protein. We developed rats that express a human SOD1 transgene with two different ALS-associated mutations (G93A and H46R) develop striking motor neuron degeneration and paralysis. The larger size of this rat model as compared with the ALS mice will facilitate studies involving manipulations of spinal fluid (implantation of intrathecal catheters for chronic therapeutic studies; CSF sampling) and spinal cord (e.g., direct administration of viral- and cell-mediated therapies). Hepatocyte growth factor (HGF) is one of the most potent survival-promoting factors for motor neurons. To examine its both protective effect on motor neurons and therapeutic potential, we administered human recombinant HGF (hrHGF) by continuous intrathecal delivery to G93A transgenic (Tg) rats at onset of paralysis for 4 weeks. Intrathecal administration of hrHGF attenuates motor neuron degeneration and prolonged the duration of the disease by 63%. Our results indicated the therapeutic efficacy of continuous intrathecal administration of hrHGF in Tg rats. The results should prompt further clinical trials in ALS using continuous intrathecal administration of hrHGF.

[Massive bleeding from tracheoarterial fistula in an amyotrophic lateral sclerosis patient treated with long-term invasive ventilation: an autopsy case report]

We report a 43-year-old woman with familial amyotrophic lateral sclerosis (FALS) who died of massive bleeding from a tracheoarterial fistula. Four years after the onset of the disease, she received invasive ventilation by tracheostomy because of respiratory failure. Four years and 7 months later, she showed an abrupt hemorrhage from the tracheostomy and died. The postmortem examination revealed a fistulous tract between the tracheal mucosal ulcer and the brachiocephalic trunk. The ulcer was in close proximity to the tracheostomy tube. In order to avoid such unexpected complications, we should observe the contact site between the tracheal mucosa and the tracheal tube in chronic tracheostomy patients.

An in vitro model for Lewy body-like hyaline inclusion/astrocytic hyaline inclusion: induction by ER stress with an ALS-linked SOD1 mutation

Neuronal Lewy body-like hyaline inclusions (LBHI) and astrocytic hyaline inclusions (Ast-HI) containing mutant Cu/Zn superoxide dismutase 1 (SOD1) are morphological hallmarks of familial amyotrophic lateral sclerosis (FALS) associated with mutant SOD1. However, the mechanisms by which mutant SOD1 contributes to formation of LBHI/Ast-HI in FALS remain poorly defined. Here, we report induction of LBHI/Ast-HI-like hyaline inclusions (LHIs) in vitro by ER stress in neuroblastoma cells. These LHI closely resemble LBHI/Ast-HI in patients with SOD1-linked FALS. LHI and LBHI/Ast-HI share the following features: 1) eosinophilic staining with a pale core, 2) SOD1, ubiquitin and ER resident protein (KDEL) positivity and 3) the presence of approximately 15–25 nm granule-coated fibrils, which are morphological hallmark of mutant SOD1-linked FALS. Moreover, in spinal cord neurons of L84V SOD1 transgenic mice at presymptomatic stage, we observed aberrant aggregation of ER and numerous free ribosomes associated with abnormal inclusion-like structures, presumably early stage neuronal LBHI. We conclude that the LBHI/Ast-HI seen in human patients with mutant SOD1-linked FALS may arise from ER dysfunction.

Novel SOD1 N86K mutation is associated with a severe phenotype in familial ALS

Familial amyotrophic lateral sclerosis (ALS) is frequently associated with mutations in the SOD1 gene. We identified a rapidly progressive disease in a patient with an inherited ALS. The identified heterozygous T>A exchange in position 1067 in the SOD1 gene results in an amino acid substitution of lysine for asparagine at position 86 (N86K) of the SOD1 protein. The family history suggested that this autosomal dominantly inherited mutation may be associated with rapidly progressive disease.

Clinical characteristics of familial amyotrophic lateral sclerosis with a Phe20Cys mutation in the SOD1 gene in a Korean family

Familial ALS (FALS) is mostly inherited as an age-dependent autosomal dominant trait. Since the discovery of mutations in the gene encoding Cu/Zn superoxide dismutase (SOD1), testing for SOD1 gene mutations has become a routine part of the investigation into ALS patients with a family history. This study reports the results of mutation evaluation and clinical features examination in a Korean family with ALS. The clinical symptoms, signs and neurological findings of a four-generation pedigree with 34 members were collected. Five exons of the Cu/Zn SOD gene were analyzed by polymerase chain reaction. The clinical signs and symptoms of ALS patients began in the lower extremities and spread to the upper extremities and bulbar muscles. The mode of transmission was determined to be autosomal dominant, and low penetrance was seen in females. The age at onset varied from 37 to 77 years. ALSFRS-R testing showed variability in the clinical progression of the disease. A point mutation in exon 1 of the SOD1 gene, resulting in an amino acid change from phenylalanine 20 to cysteine (F20C), was identified. This is the first report of clinical features resulting from the Phe20Cys mutation in the SOD1 gene.

Anticipation and phenotypic heterogeneity in korean familial amyotrophic lateral sclerosis with superoxide dismutase 1 gene mutation

Background and purpose

Different mutations in the Cu/Zn superoxide dismutase 1 (SOD1) gene have been reported in approximately 10% of cases of familial amyotrophic lateral sclerosis (ALS). The aim of this study was to analyze for mutations in the SOD1 gene and clinical characteristics in Korean family of ALS.

Methods

A subpopulation of the family reported here has been described previously. In the present study, we analyzed the SOD1 gene in the proband and his immediate family members, who were not reported on previously. Genomic DNA was isolated from the leukocytes of whole blood samples and the coding region of the SOD1 gene was analyzed by PCR and direct sequencing.

Results

The genetic alterations were a GGC-to-GTT transition at codon 10 in exon 1 and [IVS4+15_16insA; IVS4+42delG; IVS4+59_60insT] in intron 4. Patients with these mutations exhibit diverse clinical onset symptoms and acceleration of the age at onset in successive generations, which is called anticipation.

Conclusions

We have described a family with familial ALS that showed autosomal-dominant inheritance and two distinct genetic alterations in Cu/Zn-SOD1. The affected family members had different phenotypes and anticipation.

Development of a rat model of amyotrophic lateral sclerosis expressing a human SOD1 transgene

Mutations in copper-zinc superoxide dismutase gene (SOD1) have been linked to some familial cases of ALS. We report here that rats that express a human SOD1 transgene with two different ALS-associated mutations (G93A and H46R) develop striking motor neuron degeneration and paralysis. By comparing the two transgenic rats with different SOD1 mutations, we demonstrate that the time course in these rats was similar to human SOD1-mediated familial ALS. As in the human disease and transgenic ALS mice, pathological analysis shows selective loss of motor neurons in the spinal cords of these transgenic rats. In addition, typical neuronal Lewy body-like hyaline inclusions as well as astrocytic hyaline inclusions identical to those in human familial ALS are observed in the spinal cords. The larger size of this rat model as compared with the ALS mice will facilitate studies involving manipulations of spinal fluid (implantation of intrathecal catheters for chronic therapeutic studies; CSF sampling) and spinal cord (e.g., direct administration of viral- and cell-mediated therapies).

Familial amyotrophic lateral sclerosis with His46Arg mutation in Cu/Zn superoxide dismutase presenting characteristic clinical features and Lewy body-like hyaline inclusions

We evaluated the characteristic clinical features of one family of familial amyotrophic sclerosis (FALS) with a His46Arg mutation in the enzyme Cu/Zn superoxide dismutase (SOD1). Codon 46 encodes the binding site for copper and the His46Arg mutation may result in decreased copper binding and copper toxicity. The disease duration of this family was 17.8+/-13.2 years (mean+/-S.D.) with the age at onset being 42.9+/-4.7 years old (mean+/-S.D.). The initial sign was distal weakness of the unilateral lower limb, extending to the other lower limb. An autopsy was performed on a 62-year-old female member of the family who had the mutation. Her disease duration was 23 years, and she died of tonsillar herniation caused by metastasis of colon cancer in the cerebellum. Neuropathological findings showed marked loss of large anterior horn cells and very mild degeneration of corticospinal tracts as well as posterior columns. The number of nuclei of Clark's column was reduced. Lewy body-like hyaline inclusion bodies (LBHIs) were frequently seen in the remaining anterior horn cells. Astrocytic hyaline inclusions (Ast-HIs) were also seen. This is the first autopsy report of FALS with a His46Arg mutation presenting neuronal LBHIs and Ast-HIs. The formation of LBHIs and Ast-HIs may be dependent on the phenotype of the preferential lower motor neuron involvement in FALS with a SOD mutation and long disease duration.

Genetic epidemiology of amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a late onset, rapidly progressive and ultimately fatal neurological disorder, caused by the loss of motor neurons in the brain and spinal cord. Familial aggregation of ALS, with an age-dependent but high penetrance, is a major risk factor for ALS. Familial ALS (FALS) is clinically and genetically heterogeneous. Three genes and linkage to four additional gene loci have been identified so far and may either predominantly lead to ALS (ALSI-ALS6) or cause multisystem neurodegeneration with ALS as an occasional symptom (tauopathies, ALS-dementia complex). This review presents a tentative classification of the "major" ALS genes and ALS "susceptibility" genes, that may act as susceptibility factors for neurodegeneration in interaction with other genetic or environmental risk factors. Considering that mutations in ALS genes explain approximately 10% of familial as well as sporadic ALS, and most remaining cases of the discase are thought to result form the interaction of several genes and environmental factors, ALS is a paradigm for multifactorial discases.

Fibrillar inclusions and motor neuron degeneration in transgenic mice expressing superoxide dismutase 1 with a disrupted copper-binding site

Mutations in Cu/Zn superoxide dismutase 1 (SOD1) have been linked to dominantly inherited forms of amyotrophic lateral sclerosis (FALS). To test the hypothesis that the toxicity of mutant SOD1 originates in Cu(2+)-mediated formation of toxic radicals, we generated transgenic mice that express human SOD1 that encodes disease-linked mutations at two of the four histidine residues that are crucial for the coordinated binding of copper (H46R/H48Q). We demonstrate that mice expressing this mutant, which possesses little or no superoxide scavenging activity, develop motor neuron disease. Hence, mutations in SOD1 that disrupt the copper-binding site do not eliminate toxicity. We note that the pathology of the H46R/H48Q mice is dominated by fibrillar (Thioflavin-S-positive) inclusions and that similar inclusions were evident in mouse models that express the G37R, G85R, and G93A variants of human SOD1. Overall, our data are consistent with the hypothesis that the aberrant folding/aggregation of mutant SOD1 is a prominent feature in the pathogenesis of motor neuron disease.

Clinical features and neuropathological findings of familial amyotrophic lateral sclerosis with a His46Arg mutation in Cu/Zn superoxide dismutase

We examined the characteristic clinical features of one family of familial amyotrophic lateral sclerosis (FALS) with a His46Arg mutation in the enzyme Cu/Zn superoxide dismutase-1 (SOD1). The disease duration for this family was 18.1 +/- 13.2 (mean +/- S.D.) years, with the age at onset being 39.7 +/- 10.5 years old (mean +/- S.D.). The initial sign was distal weakness of the unilateral lower limb, extending to the lower limb of the other side. A wheel chair became necessary at 9.8 +/- 3.2 years after the onset. Upper limb weakness started at 15.5 +/- 8.9 years following from the onset. An autopsy was performed on a 71-year-old woman of the family with the mutation. Her disease duration was 47 years, and she died of pneumonia. She had no clear upper motor neuron involvement. Bulbar sign and respiratory muscle weakness had developed 2 years before her death. Neuropathological findings showed degeneration of corticospinal tracts, anterior/posterior spinocerebellar tracts, posterior columns, and Clarke's columns. There were few anterior horn cells in the lumbar spinal cord and no Lewy body-like hyaline inclusion bodies in these remaining anterior horn neurons. This is the first autopsy report of FALS with a His46Arg mutation in the SOD1 enzyme.

A novel SOD1 gene mutation in familial ALS with low penetrance in females

We identified a novel missense mutation in the Cu/Zn superoxide dismutase gene in a family with amyotrophic lateral sclerosis (ALS). The mutation was a transition of T to C, resulting in a substitution of leucine 126 to serine in exon 5. The family had very unique clinical features of extremely mild severity only in the legs of two male patients with onset of 42 and 52 years old, and their mothers did not develop any symptom even after reaching the age of 80 and carrying the same mutation. The present study suggests that there are other factors that delay or prevent the disease.

Impaired retrograde axonal transport of adenovirus-mediated E. coli LacZ gene in the mice carrying mutant SOD1 gene

A replication-defective recombinant adenoviral vector containing E. coli lacZ gene was injected into the gastrocnemius muscles of transgenic mice carrying mutant Cu/Zn superoxide dismutase (SOD1) gene and non-transgenic wild-type mice at 40 weeks of age. After 60 and 90 h of the injection, lacZ staining was observed at the distal ends of the sciatic nerves in both mice groups, with the number and the distances greatly reduced in the transgenic mice. Mean velocities of retrograde transport for lacZ was estimated to be 2.1 and 0.05 mm/24 h in non-transgenic and transgenic mice, respectively. These results indicate that the retrograde axonal transport of foreign gene product is impaired in the mice model for familial amyotrophic lateral sclerosis.

Lack of SOD1 gene mutations and activity alterations in two Italian families with amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a progressive fatal disorder, which results from the degeneration of motor neurons in the brain and spinal cord. Approximately 20% of the inherited autosomal dominant cases are due to mutations within the gene coding for Cu/Zn superoxide dismutase 1 (SOD1), a cytosolic homodimeric enzyme that catalyzes the dismutation of toxic superoxide anion. We investigated the presence of SOD1 gene mutations and activity alterations in two unrelated families of ALS patients from Elba, an island of central Italy. No mutation in SOD1 exon 1 to 5 and no activity alteration were observed in all members of the two analyzed ALS families (FALS). These data show an apparent heterogeneous distribution of ALS patients with SOD1 gene mutations among different populations and suggest that another genetic locus could be involved in the disease.

Amyotrophic lateral sclerosis: copper/zinc superoxide dismutase (SOD1) gene mutations

Mutations of the SOD1 gene, encoding the enzyme copper/zinc superoxide dismutase, have been identified in around 20% of patients with familial amyotrophic lateral sclerosis (ALS), and also in patients with apparently sporadic ALS. The table documents the mutations identified and published to date, and references clinical and pathological descriptions of the patients and families with individual mutations. The table includes 63 different mutations of SOD1 at 43 codons, three intronic sites, and two in the 3' untranslated region. Most of the mutations are heterozygotes, with autosomal dominant inheritance, but a small number of individuals appear to be sporadic, or are homozygotes with autosomal dominant recessive inheritance.

Remarkable increase in cerebrospinal fluid 3-nitrotyrosine in patients with sporadic amyotrophic lateral sclerosis

To investigate the significance of peroxynitrite-mediated oxidative damage in the pathogenesis of sporadic amyotrophic lateral sclerosis (SALS), the concentrations of 3-nitrotyrosine and tyrosine in the cerebrospinal fluid (CSF) of patients with SALS were determined. The concentration of 3-nitrotyrosine and the 3-nitrotyrosine/ tyrosine ratio in patients with SALS were approximately seven times those of controls. Thus, the present findings in living patients provide in vivo evidence for a possible role of peroxynitrite, a mediator of oxidative stress, and increased nitration of tyrosine residues in the pathogenesis of SALS.

Increase in oxidized NO products and reduction in oxidized glutathione in cerebrospinal fluid from patients with sporadic form of amyotrophic lateral sclerosis

To determine the role of free radical mechanisms in the pathogenesis of amyotrophic lateral sclerosis (ALS), cerebrospinal fluid concentrations of oxidized nitric oxide (NO) products (nitrite and nitrate) and reduced and oxidized forms of glutathione (GSH and GSSG, respectively) were compared between patients with the sporadic form of ALS (SALS) and controls. In the SALS patients, the nitrate levels were significantly higher (by 73%) in contrast to remarkably lower GSSG/GSH ratio, approximately 3-fold, compared to controls. These results suggest that NO production or oxidation is activated in SALS patients, leading to a decrease in superoxide radicals to oxidize GSH. The subsequent generation of a highly reactive anion, peroxynitrite, may play a causal role in the pathogenesis of SALS.

Molecular analyses of the Cu/Zn superoxide dismutase gene in patients with familial amyotrophic lateral sclerosis (ALS) in Japan

1. Amyotrophic lateral sclerosis (ALS) is a degenerative disorder characterized by selective damage to the neural system that mediates voluntary movement. Although the pathophysiologic process of ALS remains unknown, about 5 to 10% of cases are familial. According to genetic linkage studies, the familial ALS (FALS) gene has been mapped on chromosome 21 in some families and recent work identified some different missense mutations in the Cu/Zn superoxide dismutase gene in FALS families. 2. We recently identified five mutations in six FALS families. The mutations identified in our FALS families are H46R, L84V, I104F, S134N, and V148I. The H46R mutation that locates in the active site of Cu/Zn SOD gene is associated with two Japanese families with very slow progression of ALS. On the other hand, the L84V mutation associated with a rapidly progressive loss of motor function with predominant lower motor neuron manifestations. 3. In the family with the V148I, the phenotype of the patient varied very much among the affected members. One case had weakness of the lower extremities at first and died without bulbar paresis. The second case first noticed wasting of the upper limbs with bulbar symptoms, but the third had weakness of upper extremities without developing dysarthria nor dysphagia until death. These mutations account for 50% of all FALS families screened, although Cu/Zn SOD gene mutations are responsible for less than about 13-21% in the Western population. 4. Our results indicate that the progression of disease with mutations of Cu/Zn SOD is well correlated with each mutation. The exact mechanism by which the abnormal Cu/Zn SOD molecules selectively affect the function of motor neurons is still unknown.

Limited corticospinal tract involvement in amyotrophic lateral sclerosis subjects with the A4V mutation in the copper/zinc superoxide dismutase gene

We examined 11 subjects with inherited amyotrophic lateral sclerosis (familial amyotrophic lateral sclerosis, FALS) associated with the most common copper/zinc superoxide dismutase 1 (SOD1) mutation, an alanine for valine substitution in codon 4 (A4V). Autopsies were performed on 5 subjects. The clinical and pathological findings are described and compared with those of 9 sporadic ALS (SALS) subjects. There was no clinical evidence of upper motor neuron (UMN) involvement in 10 FALS A4V subjects. All subjects had lower motor neuron (LMN) signs and electrophysiological evidence of denervation in at least three limbs. All SALS subjects had signs of both UMN and LMN involvement. Pathological studies found severe abnormalities of LMNs in all FALS and SALS subjects. UMN involvement was either absent or mild in the A4V SOD1 FALS subjects and severe in the SALS subjects. Pathological abnormalities in systems other than the motor neurons were more frequent in the FALS A4V subjects. This information suggests that current diagnostic criteria for ALS, requiring dinical evidence for both upper and lower motor neuron involvement, should be modified; ie, the diagnosis should be deemed established when there is evidence of denervation in three or more limbs and a mutation in the gene for SOD1, even without dinical signs of UMN involvement.

Oxidative stress and superoxide dismutase in development, aging and gene regulation

Free radicals and other reactive oxygen species are produced in the metabolic pathways of aerobic cells and affect a number of biological processes. Oxidation reactions have been postulated to play a role in aging, a number of degenerative diseases, differentiation and development as well as serving as subcellular messengers in gene regulatory and signal transduction pathways. The discovery of the activity of superoxide dismutase is a seminal work in free radical biology, because it established that free radicals were generated by cells and because it made removal of a specific free radical substance possible for the first time, which greatly accelerated research in this area. In this review, the role of reactive oxygen in aging, amyotrophic lateral sclerosis (a neurodegenerative disease), development, differentiation, and signal transduction are discussed. Emphasis is also given to the role of superoxide dismutases in these phenomena.

Familial ALS is associated with mutations in all exons of SOD1: a novel mutation in exon 3 (Gly72Ser)

Mutations of the SOD1 gene, which encodes the enzyme copper/zinc superoxide dismutase, are associated with familial amyotrophic lateral sclerosis (ALS). SOD1 consists of five exons, and over 50 different mutations have been described involving exons 1,2,4 and 5. The absence of mutations in exon 3 has been attributed to a critical function of this exon, its integrity being necessary for the toxic effect of mutant SOD1, and it has been suggested that such mutations may be lethal rather than leading to adult onset disease. We identified the heterozygote mutation Gly72Ser (exon 3) in a family with two individuals affected by ALS. SOD enzyme activity was reduced by 45% when measured in erythrocytes indicating reduced enzyme activity, or reduced stability of the mutant protein. These findings indicate that exon 3 is not a privileged region from mutation; that all five exons should be investigated when seeking SOD1 mutations in human disease; and may help in a better understanding of the pathogenicity of these mutations in ALS.

Prominent sensory and autonomic disturbances in familial amyotrophic lateral sclerosis with a Gly93Ser mutation in the SOD1 gene

A missense mutation (Gly93-->Ser) was identified in exon 4 of the Cu/Zn superoxide dismutase (SOD1) gene of a 48-year-old Japanese man with familial amyotrophic lateral sclerosis (FALS). The SOD1 activities in the fibroblasts and in a lysate of erythrocytes of the patient did not differ from those of healthy controls. The clinical characteristics of the patient were fairly slow progression of the illness, prominent sensory impairment, urinary disturbance and blood pressure fluctuation due to sympathetic hyperactivity. The severe sensory and autonomic disturbances, association of which with FALS has not been previously reported, may represent specific clinical features associated with the Gly93Ser mutation or may indicate the variability of clinical findings even in patients with the same mutation.

Genetic transfer of the wobbler gene to a C57BL/6J x NZB hybrid stock: natural history of the motor neuron disease and response to CNTF and BDNF cotreatment

Preclinical diagnosis of motor neuron disease (MND) in the wobbler mouse (wr/wr) has been impossible until recently. However, with the development of a new hybrid, the C57BL/6J x New Zealand Black (B6NZB) wr/wr mouse, the polymerase chain reaction (PCR) can be used to establish the preclinical diagnosis. We compared the clinical and histological features of MND and the effects of neurotrophic factor cotreatment between the hybrid B6NZB-wr/wr and the congenic C57BL/6J-wr/wr mice. Clinical assessments of body weight, grip strength, running speed, paw position, and walking pattern were made weekly from age 2 weeks through 8 weeks (n = 10, B6NZB-wr/wr; n = 15, C57BL/6J-wr/wr). Survival was analyzed (n = 7, each strain) as was C5 and C6 spinal cord motoneuron morphology and ventral root histometry (n = 7, each strain). For cotreatment, 8 B6NZB-wr/wr and 7 C57BL/6J-wr/wr mice received subcutaneous ciliary neurotrophic factor (1 mg/kg) and brain-derived neurotrophic factor (5 mg/kg) on alternate days, 6 days/week for 4 weeks. B6NZB-wr/wr mice could be distinguished from C57BL/6J-wr/wr mice at age 3 weeks by a more abnormal paw position (P < 0.01) and walking pattern (P < 0.05) and lower grip strength (P < 0.001) and running speed (P < 0.001). After 3 weeks, the changes continued to be greater in B6NZB-wr/wr mice. Although B6NZB-wr/wr mice were more severely affected early in the disease, their survival was comparable to C57BL/6J-wr/wr mice. Anterior horn cell vacuolar degeneration and myelinated fiber histometry were similar in both strains. The clinical response to CNTF/BDNF cotreatment was marked in both groups although it was weaker in B6NZB-wr/wr mice. Thus, the hybrid B6NZB-wr/wr mice have a more severe clinical phenotype and offer a unique opportunity to study the mechanisms of presymptomatic motor neuron degeneration and the effects of therapeutic agents for human MND.

Epidemiology of mutations in superoxide dismutase in amyotrophic lateral sclerosis

We registered 366 families in a study of dominantly inherited amyotrophic lateral sclerosis. Two hundred ninety families were screened for mutations in the gene encoding copper-zinc cytosolic superoxide dismutase (SOD1). Mutations were detected in 68 families. The most common SOD1 mutation is an alanine for valine substitution in codon 4 (50%). We present clinical and genetic data concerning 112 families with 395 affected individuals. The clinical characteristics of patients with familial amyotrophic lateral sclerosis arising from SOD1 mutations are similar to those lacking SOD1 defects. Mean age at onset was earlier (Wilcoxon test, p = 0.004) in the SOD1 group (46.9 years [standard deviation, 12.5] vs 50.5 years [11.5] in the non-SOD1 group). Bulbar onset was associated with a later onset age. The presence of either of two mutations, G37R and L38V, predicted an earlier age at onset. Kaplan-Meier plots demonstrated shorter survival in the SOD1 group compared with the non-SOD1 group at early survival times (Wilcoxon test, p = 0.0007). The presence of one mutation, A4V, correlated with shorter survival. G37R, G41D, and G93C mutations predicted longer survival. This information suggests it will be productive to investigate other genetic determinants in amyotrophic lateral sclerosis and to use epidemiological characteristics of the disease to help discern molecular mechanisms of motor neuron cell death.

Three novel mutations and two variants in the gene for Cu/Zn superoxide dismutase in familial amyotrophic lateral sclerosis

Autosomal dominant inheritance is exhibited by about 10% of cases of amyotrophic lateral sclerosis (ALS), a paralytic disorder characterized by the death of motor neurons in the brain and spinal cord. A subgroup of these familial cases are linked to mutations in the gene which codes for Cu/Zn superoxide dismutase (SOD1). We report three additional mutations occurring in the SOD1 gene in ALS patients and two single base pair variant changes. The single base pair change in an ALS family causes a glycine 93 to valine substitution, which is the fifth distinct amino acid change reported for the glycine 93 residue. One missense mutation in exon 5 would substitute neutral valine for the negatively-charged aspartate 124 (aspartate 124 to valine). An individual with an apparently sporadic case of ALS carries a three base pair deletion in exon 5 of the SOD1 gene. These three mutations bring to 38 the total number of distinct SOD1 mutations associated with familial ALS.

Genetics of amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a paralytic disorder caused by degeneration of motor neurons in the brain and spinal cord. Identification of mutations in the gene for Cu,Zn superoxide dismutase (SOD1) in a subset of ALS families made it possible to develop a transgenic mouse model of ALS and to investigate its pathogenesis. These investigations suggest that mutant SOD1 acts through a toxic gain of function which may involve generation of free radicals. Conformational change in the mutant SOD1 protein, especially the distortion of the 'rim' of the electrostatic guidance channel may be central to this toxic gain of function and to the pathogenesis of ALS.

alpha-Tocopherol quinone level is remarkably low in the cerebrospinal fluid of patients with sporadic amyotrophic lateral sclerosis

In order to investigate the role of free radicals in the pathogenesis of sporadic amyotrophic lateral sclerosis (SALS), the concentrations of alpha-tocopherol (alpha-TOH) and its oxidized form alpha-tocopherol quinone (alpha-TQ) in the cerebrospinal fluid (CSF) of SALS patients were determined. The alpha-TOH level was 31% lower (P < 0.05) and the alpha-TQ level was 75% lower (P < 0.001) in SALS patients than in normal subjects. The results of the present study do not support the hypothesis that activated lipid peroxidation accelerates oxidation of alpha-TOH into alpha-TQ in SALS patients.

A novel two-base mutation in the Cu/Zn superoxide dismutase gene associated with familial amyotrophic lateral sclerosis in Japan

We have identified a novel two-base mutation in exon 1 of the Cu/Zn superoxide dismutase (SOD1) gene (TGC to TTT), which resulted in Cys6 to Phe substitution in a Japanese family with amyotrophic lateral sclerosis (ALS). This is the first case of familial ALS-associated two-base change of the SOD1 gene. Similar to several mutations in exon 1 of the SOD1 gene such as Ala4 to Val, Ala4 to Thr and Val14 to Met, affected members of the present family showed a rapid progression of motor dysfunction. Although Ala4, Cys6 and Val7 reside in the middle of the first beta-strand of the SOD1, a family with a mutation of Val7 to Glu associates with slow progression of the disease. These findings suggest that clinical courses are variable with each mutation, even in the same exon.