Showing papers on "Amyotrophic lateral sclerosis published in 2010"

Mutations of optineurin in amyotrophic lateral sclerosis

Abstract: Amyotrophic lateral sclerosis (ALS) has its onset in middle age and is a progressive disorder characterized by degeneration of motor neurons of the primary motor cortex, brainstem and spinal cord. Most cases of ALS are sporadic, but about 10% are familial. Genes known to cause classic familial ALS (FALS) are superoxide dismutase 1 (SOD1), ANG encoding angiogenin, TARDP encoding transactive response (TAR) DNA-binding protein TDP-43 (ref. 4) and fused in sarcoma/translated in liposarcoma (FUS, also known as TLS). However, these genetic defects occur in only about 20-30% of cases of FALS, and most genes causing FALS are unknown. Here we show that there are mutations in the gene encoding optineurin (OPTN), earlier reported to be a causative gene of primary open-angle glaucoma (POAG), in patients with ALS. We found three types of mutation of OPTN: a homozygous deletion of exon 5, a homozygous Q398X nonsense mutation and a heterozygous E478G missense mutation within its ubiquitin-binding domain. Analysis of cell transfection showed that the nonsense and missense mutations of OPTN abolished the inhibition of activation of nuclear factor kappa B (NF-kappaB), and the E478G mutation revealed a cytoplasmic distribution different from that of the wild type or a POAG mutation. A case with the E478G mutation showed OPTN-immunoreactive cytoplasmic inclusions. Furthermore, TDP-43- or SOD1-positive inclusions of sporadic and SOD1 cases of ALS were also noticeably immunolabelled by anti-OPTN antibodies. Our findings strongly suggest that OPTN is involved in the pathogenesis of ALS. They also indicate that NF-kappaB inhibitors could be used to treat ALS and that transgenic mice bearing various mutations of OPTN will be relevant in developing new drugs for this disorder.

Ataxin-2 intermediate-length polyglutamine expansions are associated with increased risk for ALS

Abstract: The causes of amyotrophic lateral sclerosis (ALS), a devastating human neurodegenerative disease, are poorly understood, although the protein TDP-43 has been suggested to have a critical role in disease pathogenesis. Here we show that ataxin 2 (ATXN2), a polyglutamine (polyQ) protein mutated in spinocerebellar ataxia type 2, is a potent modifier of TDP-43 toxicity in animal and cellular models. ATXN2 and TDP-43 associate in a complex that depends on RNA. In spinal cord neurons of ALS patients, ATXN2 is abnormally localized; likewise, TDP-43 shows mislocalization in spinocerebellar ataxia type 2. To assess the involvement of ATXN2 in ALS, we analysed the length of the polyQ repeat in the ATXN2 gene in 915 ALS patients. We found that intermediate-length polyQ expansions (27-33 glutamines) in ATXN2 were significantly associated with ALS. These data establish ATXN2 as a relatively common ALS susceptibility gene. Furthermore, these findings indicate that the TDP-43-ATXN2 interaction may be a promising target for therapeutic intervention in ALS and other TDP-43 proteinopathies.

TDP-43 and FUS in amyotrophic lateral sclerosis and frontotemporal dementia

Abstract: Abnormal intracellular protein aggregates comprise a key characteristic in most neurodegenerative diseases, including amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). The seminal discoveries of accumulation of TDP-43 in most cases of ALS and the most frequent form of FTD, frontotemporal lobar degeneration with ubiquitinated inclusions, followed by identification of FUS as the novel pathological protein in a small subset of patients with ALS and various FTD subtypes provide clear evidence that these disorders are related. The creation of a novel molecular classification of ALS and FTD based on the identity of the predominant protein abnormality has, therefore, been possible. The striking functional and structural similarities of TDP-43 and FUS, which are both DNA/RNA binding proteins, imply that abnormal RNA metabolism is a pivotal event, but the mechanisms leading to TDP-43 and FUS accumulation and the resulting neurodegeneration are currently unknown. Nonetheless, TDP-43 and FUS are promising candidates for the development of novel biomarker assays and targeted therapies.

TDP-43 Proteinopathy and Motor Neuron Disease in Chronic Traumatic Encephalopathy

Abstract: Epidemiological evidence suggests that the incidence of amyotrophic lateral sclerosis is increased in association with head injury. Repetitive head injury is also associated with the development of chronic traumatic encephalopathy (CTE), a tauopathy characterized by neurofibrillary tangles throughout the brain in the relative absence of β-amyloid deposits. We examined 12 cases of CTE and, in 10, found a widespread TAR DNA-binding protein of approximately 43kd (TDP-43) proteinopathy affecting the frontal and temporal cortices, medial temporal lobe, basal ganglia, diencephalon, and brainstem. Three athletes with CTE also developed a progressive motor neuron disease with profound weakness, atrophy, spasticity, and fasciculations several years before death. In these 3 cases, there were abundant TDP-43-positive inclusions and neurites in the spinal cord in addition to tau neurofibrillary changes, motor neuron loss, and corticospinal tract degeneration. The TDP-43 proteinopathy associated with CTE is similar to that found in frontotemporal lobar degeneration with TDP-43 inclusions, in that widespread regions of the brain are affected. Akin to frontotemporal lobar degeneration with TDP-43 inclusions, in some individuals with CTE, the TDP-43 proteinopathy extends to involve the spinal cord and is associated with motor neuron disease. This is the first pathological evidence that repetitive head trauma experienced in collision sports might be associated with the development of a motor neuron disease.

TDP-43 transgenic mice develop spastic paralysis and neuronal inclusions characteristic of ALS and frontotemporal lobar degeneration

Abstract: Neuronal cytoplasmic and intranuclear aggregates of RNA-binding protein TDP-43 are a hallmark feature of neurodegenerative diseases such as amyotrophic lateral sclerosis (ALS) and frontotemporal lobar degeneration (FTLD). ALS and FTLD show a considerable clinical and pathological overlap and occur as both familial and sporadic forms. Though missense mutations in TDP-43 cause rare forms of familial ALS, it is not yet known whether this is due to loss of TDP-43 function or gain of aberrant function. Moreover, the role of wild-type (WT) TDP-43, associated with the majority of familial and sporadic ALS/FTLD patients, is also currently unknown. Generating homozygous and hemizygous WT human TDP-43 transgenic mouse lines, we show here a dose-dependent degeneration of cortical and spinal motor neurons and development of spastic quadriplegia reminiscent of ALS. A dose-dependent degeneration of nonmotor cortical and subcortical neurons characteristic of FTLD was also observed. Neurons in the affected spinal cord and brain regions showed accumulation of TDP-43 nuclear and cytoplasmic aggregates that were both ubiquitinated and phosphorylated as observed in ALS/FTLD patients. Moreover, the characteristic ≈25-kDa C-terminal fragments (CTFs) were also recovered from nuclear fractions and correlated with disease development and progression in WT TDP-43 mice. These findings suggest that ≈25-kDa TDP-43 CTFs are noxious to neurons by a gain of aberrant nuclear function.

Mutant FUS proteins that cause amyotrophic lateral sclerosis incorporate into stress granules.

Abstract: Mutations in the RNA-binding protein FUS (fused in sarcoma) are linked to amyotrophic lateral sclerosis (ALS), but the mechanism by which these mutants cause motor neuron degeneration is not known. We report a novel ALS truncation mutant (R495X) that leads to a relatively severe ALS clinical phenotype compared with FUS missense mutations. Expression of R495X FUS, which abrogates a putative nuclear localization signal at the C-terminus of FUS, in HEK-293 cells and in the zebrafish spinal cord caused a striking cytoplasmic accumulation of the protein to a greater extent than that observed for recessive (H517Q) and dominant (R521G) missense mutants. Furthermore, in response to oxidative stress or heat shock conditions in cultures and in vivo, the ALS-linked FUS mutants, but not wild-type FUS, assembled into perinuclear stress granules in proportion to their cytoplasmic expression levels. These findings demonstrate a potential link between FUS mutations and cellular pathways involved in stress responses that may be relevant to altered motor neuron homeostasis in ALS.

Cytoplasmic Mislocalization of TDP-43 Is Toxic to Neurons and Enhanced by a Mutation Associated with Familial Amyotrophic Lateral Sclerosis

Abstract: Mutations in the gene encoding TDP-43—the major protein component of neuronal aggregates characteristic of amyotrophic lateral sclerosis (ALS) and frontotemporal lobar degeneration (FTLD) with ubiquitin-positive inclusion bodies—have been linked to familial forms of both disorders. Aggregates of TDP-43 in cortical and spinal motorneurons in ALS, or in neurons of the frontal and temporal cortices in FTLD, are closely linked to neuron loss and atrophy in these areas. However, the mechanism by which TDP-43 mutations lead to neurodegeneration is unclear. To investigate the pathogenic role of TDP-43 mutations, we established a model of TDP-43 proteinopathies by expressing fluorescently tagged wild-type and mutant TDP-43 in primary rat cortical neurons. Expression of mutant TDP-43 was toxic to neurons, and mutant-specific toxicity was associated with increased cytoplasmic mislocalization of TDP-43. Inclusion bodies were not necessary for the toxicity and did not affect the risk of cell death. Cellular survival was unaffected by the total amount of exogenous TDP-43 in the nucleus, but the amount of cytoplasmic TDP-43 was a strong and independent predictor of neuronal death. These results suggest that mutant TDP-43 is mislocalized to the cytoplasm, where it exhibits a toxic gain-of-function and induces cell death.

Motor Neuron Diversity in Development and Disease

Abstract: Although often considered as a group, spinal motor neurons are highly diverse in terms of their morphology, connectivity, and functional properties and differ significantly in their response to disease. Recent studies of motor neuron diversity have clarified developmental mechanisms and provided novel insights into neurodegeneration in amyotrophic lateral sclerosis (ALS). Motor neurons of different classes and subtypes--fast/slow, alpha/gamma--are grouped together into motor pools, each of which innervates a single skeletal muscle. Distinct mechanisms regulate their development. For example, glial cell line-derived neurotrophic factor (GDNF) has effects that are pool-specific on motor neuron connectivity, column-specific on axonal growth, and subtype-specific on survival. In multiple degenerative contexts including ALS, spinal muscular atrophy (SMA), and aging, fast-fatigable (FF) motor units degenerate early, whereas motor neurons innervating slow muscles and those involved in eye movement and pelvic sphincter control are strikingly preserved. Extrinsic and intrinsic mechanisms that confer resistance represent promising therapeutic targets in these currently incurable diseases.

TAR DNA-binding protein 43 in neurodegenerative disease

Abstract: In 2006, TAR DNA-binding protein 43 (TDP-43), a highly conserved nuclear protein, was identified as the major disease protein in amyotrophic lateral sclerosis (ALS) and in the most common variant of frontotemporal lobar degeneration (FTLD), FTLD-U, which is characterized by cytoplasmic inclusions that stain positive for ubiquitin but negative for tau and α-synuclein. Since then, rapid advances have been made in our understanding of the physiological function of TDP-43 and the role of this protein in neurodegeneration. These advances link ALS and FTLD-U (now designated FTLD-TDP) to a shared mechanism of disease. In this Review, we summarize the current evidence regarding the normal function of TDP-43 and the TDP-43 pathology observed in FTLD-TDP, ALS, and other neurodegenerative diseases wherein TDP-43 pathology co-occurs with other disease-specific lesions (for example, with amyloid plaques and neurofibrillary tangles in Alzheimer disease). Moreover, we discuss the accumulating data that support our view that FTLD-TDP and ALS represent two ends of a spectrum of primary TDP-43 proteinopathies. Finally, we comment on the importance of recent advances in TDP-43-related research to neurological practice, including the new opportunities to develop better diagnostics and disease-modifying therapies for ALS, FTLD-TDP, and related disorders exhibiting TDP-43 pathology.

Gain and loss of function of ALS-related mutations of TARDBP (TDP-43) cause motor deficits in vivo.

Abstract: TDP-43 has been found in inclusion bodies of multiple neurological disorders, including amyotrophic lateral sclerosis, frontotemporal dementia, Parkinson's disease and Alzheimer's disease. Mutations in the TDP-43 encoding gene, TARDBP, have been subsequently reported in sporadic and familial ALS patients. In order to investigate the pathogenic nature of these mutants, the effects of three consistently reported TARDBP mutations (A315T, G348C and A382T) were tested in cell lines, primary cultured motor neurons and living zebrafish embryos. Each of the three mutants and wild-type (WT) human TDP-43 localized to nuclei when expressed in COS1 and Neuro2A cells by transient transfection. However, when expressed in motor neurons from dissociated spinal cord cultures these mutant TARDBP alleles, but less so for WT TARDBP, were neurotoxic, concomitant with perinuclear localization and aggregation of TDP-43. Finally, overexpression of mutant, but less so of WT, human TARDBP caused a motor phenotype in zebrafish (Danio rerio) embryos consisting of shorter motor neuronal axons, premature and excessive branching as well as swimming deficits. Interestingly, knock-down of zebrafisfh tardbp led to a similar phenotype, which was rescued by co-expressing WT but not mutant human TARDBP. Together these approaches showed that TARDBP mutations cause motor neuron defects and toxicity, suggesting that both a toxic gain of function as well as a novel loss of function may be involved in the molecular mechanism by which mutant TDP-43 contributes to disease pathogenesis.

Deficits in axonal transport precede ALS symptoms in vivo.

Abstract: ALS is a fatal neurodegenerative disease characterized by selective motor neuron death resulting in muscle paralysis. Mutations in superoxide dismutase 1 (SOD1) are responsible for a subset of familial cases of ALS. Although evidence from transgenic mice expressing human mutant SOD1G93A suggests that axonal transport defects may contribute to ALS pathogenesis, our understanding of how these relate to disease progression remains unclear. Using an in vivo assay that allows the characterization of axonal transport in single axons in the intact sciatic nerve, we have identified clear axonal transport deficits in presymptomatic mutant mice. An impairment of axonal retrograde transport may therefore represent one of the earliest axonal pathologies in SOD1G93A mice, which worsens at an early symptomatic stage. A deficit in axonal transport may therefore be a key pathogenic event in ALS and an early disease indicator of motor neuron degeneration.

FUS‐immunoreactive inclusions are a common feature in sporadic and non‐SOD1 familial amyotrophic lateral sclerosis

Abstract: Objective: Amyotrophic lateral sclerosis (ALS) is a fatal disorder of motor neuron degeneration. Most cases of ALS are sporadic (SALS), but about 5 to 10% of ALS cases are familial (FALS). Recent studies have shown that mutations in FUS are causal in approximately 4 to 5% of FALS and some apparent SALS cases. The pathogenic mechanism of the mutant FUS-mediated ALS and potential roles of FUS in non-FUS ALS remain to be investigated. Methods: Immunostaining was performed on postmortem spinal cords from 78 ALS cases, including SALS (n 52), ALS with dementia (ALS/dementia, n 10), and FALS (n 16). In addition, postmortem brains or spinal cords from 22 cases with or without frontotemporal lobar degeneration were also studied. In total, 100 cases were studied. Results: FUS-immunoreactive inclusions were observed in spinal anterior horn neurons in all SALS and FALS cases, except for those with SOD1 mutations. The FUS-containing inclusions were also immunoreactive with antibodies to TDP43, p62, and ubiquitin. A fraction of tested FUS antibodies recognized FUS inclusions, and specific antigen retrieval protocol appeared to be important for detection of the skein-like FUS inclusions. Interpretation: Although mutations in FUS account for only a small fraction of FALS and SALS, our data suggest that FUS protein may be a common component of the cellular inclusions in non-SOD1 ALS and some other neurodegenerative conditions, implying a shared pathogenic pathway underlying SALS, non-SOD1 FALS, ALS/ dementia, and related disorders. Our data also indicate that SOD1-linked ALS may have a pathogenic pathway distinct from SALS and other types of FALS. ANN NEUROL 2010;67:739 –748

Loss of murine TDP-43 disrupts motor function and plays an essential role in embryogenesis

Abstract: Abnormal TDP-43 aggregation is a prominent feature in the neuropathology of amyotrophic lateral sclerosis (ALS) and frontotemporal lobar degeneration. Mutations in TARDBP, the gene encoding TDP-43, cause some cases of ALS. The normal function of TDP-43 remains incompletely understood. To better understand TDP-43 biology, we generated mutant mice carrying a genetrap disruption of Tardbp. Mice homozygous for loss of TDP-43 are not viable. TDP-43 deficient embryos die about day 7.5 of embryonic development thereby demonstrating that TDP-43 protein is essential for normal prenatal development and survival. However, heterozygous Tardbp mutant mice exhibit signs of motor disturbance and muscle weakness. Compared with wild type control littermates, Tardbp+/− animals have significantly decreased forelimb grip strength and display deficits in a standard inverted grid test despite no evidence of pathologic changes in motor neurons. Thus, TDP-43 is essential for viability, and mild reduction in TDP-43 function is sufficient to cause motor deficits without degeneration of motor neurons.

Novel Antibodies Reveal Inclusions Containing Non-Native SOD1 in Sporadic ALS Patients

Abstract: Mutations in CuZn-superoxide dismutase (SOD1) cause amyotrophic lateral sclerosis (ALS) and are found in 6% of ALS patients. Non-native and aggregation-prone forms of mutant SOD1s are thought to trigger the disease. Two sets of novel antibodies, raised in rabbits and chicken, against peptides spaced along the human SOD1 sequence, were by enzyme-linked immunosorbent assay and an immunocapture method shown to be specific for denatured SOD1. These were used to examine SOD1 in spinal cords of ALS patients lacking mutations in the enzyme. Small granular SOD1-immunoreactive inclusions were found in spinal motoneurons of all 37 sporadic and familial ALS patients studied, but only sparsely in 3 of 28 neurodegenerative and 2 of 19 non-neurological control patients. The granular inclusions were by confocal microscopy found to partly colocalize with markers for lysosomes but not with inclusions containing TAR DNA binding protein-43, ubiquitin or markers for endoplasmic reticulum, autophagosomes or mitochondria. Granular inclusions were also found in carriers of SOD1 mutations and in spinobulbar muscular atrophy (SBMA) patients and they were the major type of inclusion detected in ALS patients homozygous for the wild type-like D90A mutation. The findings suggest that SOD1 may be involved in ALS pathogenesis in patients lacking mutations in the enzyme.

The small heat shock protein B8 (HspB8) promotes autophagic removal of misfolded proteins involved in amyotrophic lateral sclerosis (ALS)

Abstract: Several neurodegenerative diseases, including amyotrophic lateral sclerosis (ALS), are characterized by the presence of misfolded proteins, thought to trigger neurotoxicity. Some familial forms of ALS (fALS), clinically indistinguishable from sporadic ALS (sALS), are linked to superoxide dismutase 1 (SOD1) gene mutations. It has been shown that the mutant SOD1 misfolds, forms insoluble aggregates and impairs the proteasome. Using transgenic G93A-SOD1 mice, we found that spinal cord motor neurons, accumulating mutant SOD1 also over-express the small heat shock protein HspB8. Using motor neuronal fALS models, we demonstrated that HspB8 decreases aggregation and increases mutant SOD1 solubility and clearance, without affecting wild-type SOD1 turnover. Notably, HspB8 acts on mutant SOD1 even when the proteasome activity is specifically blocked. The pharmacological blockage of autophagy resulted in a dramatic increase of mutant SOD1 aggregates. Immunoprecipitation studies, performed during autophagic flux blockage, demonstrated that mutant SOD1 interacts with the HspB8/Bag3/Hsc70/CHIP multiheteromeric complex, known to selectively activate autophagic removal of misfolded proteins. Thus, HspB8 increases mutant SOD1 clearance via autophagy. Autophagy activation was also observed in lumbar spinal cord of transgenic G93A-SOD1 mice since several autophago-lysosomal structures were present in affected surviving motor neurons. Finally, we extended our observation to a different ALS model and demonstrated that HspB8 exerts similar effects on a truncated version of TDP-43, another protein involved both in fALS and in sALS. Overall, these results indicate that the pharmacological modulation of HspB8 expression in motor neurons may have important implications to unravel the molecular mechanisms involved both in fALS and in sALS.

Skeletal muscle-restricted expression of human SOD1 causes motor neuron degeneration in transgenic mice

Abstract: Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease of motor neurons (MNs) that causes skeletal muscle paralysis. Familial forms of ALS are linked to mutations in the superoxide dismutase-1 (SOD1) gene. The mechanisms of human SOD1 (hSOD1) toxicity to MNs are unknown. We hypothesized that skeletal muscle is a primary site of pathogenesis in ALS that triggers MN degeneration. We created transgenic (tg) mice expressing wild-type-, G37R- and G93A-hSOD1 gene variants only in skeletal muscle. These tg mice developed age-related neurologic and pathologic phenotypes consistent with ALS. Affected mice showed limb weakness and paresis with motor deficits. Skeletal muscles developed severe pathology involving oxidative damage, protein nitration, myofiber cell death and marked neuromuscular junction (NMJ) abnormalities. Spinal MNs developed distal axonopathy and formed ubiquitinated inclusions and degenerated through an apoptotic-like pathway involving capsase-3. Mice expressing wild-type and mutant forms of hSOD1 developed MN pathology. These results demonstrate that human SOD1 in skeletal muscle has a causal role in ALS and identify a new non-autonomous mechanism for MN degeneration explaining their selective vulnerability. The discovery of instigating molecular toxicities or disease progression determinants within skeletal muscle could be very valuable for the development of new effective therapies for the treatment and cure of ALS.

Chromosome 9p21 in amyotrophic lateral sclerosis in Finland: a genome-wide association study.

Abstract: Summary Background The genetic cause of amyotrophic lateral sclerosis (ALS) is not well understood. Finland is a well suited location for a genome-wide association study of ALS because the incidence of the disease is one of the highest in the world, and because the genetic homogeneity of the Finnish population enhances the ability to detect risk loci. We aimed to identify genetic risk factors for ALS in the Finnish population. Methods We did a genome-wide association study of Finnish patients with ALS and control individuals by use of Illumina genome-wide genotyping arrays. DNA was collected from patients who attended an ALS specialty clinic that receives referrals from neurologists throughout Finland. Control samples were from a population-based study of elderly Finnish individuals. Patients known to carry D90A alleles of the SOD1 gene (n=40) were included in the final analysis as positive controls to assess whether our genome-wide association study was able to detect an association signal at this locus. Findings We obtained samples from 442 patients with ALS and 521 control individuals. After quality control filters were applied, 318 167 single nucleotide polymorphisms (SNPs) from 405 people with ALS and 497 control individuals were available for analysis. We identified two association peaks that exceeded genome-wide significance. One was located on chromosome 21q22 (rs13048019, p=2·58×10 −8 ), which corresponds to the autosomal recessive D90A allele of the SOD1 gene. The other was detected in a 232 kb block of linkage disequilibrium (rs3849942, p=9·11×10 −11 ) in a region of chromosome 9p that was previously identified in linkage studies of families with ALS. Within this region, we defined a 42-SNP haplotype that was associated with significantly increased risk of ALS (p=7·47×10 −33 when people with familial ALS were compared with controls, odds ratio 21·0, 95% CI 11·2–39·1) and which overlapped with an association locus recently reported for frontotemporal dementia. For the 93 patients with familial ALS, the population attributable risk for the chromosome 9p21 locus was 37·9% (95% CI 27·7–48·1) and that for D90A homozygosity was 25·5% (16·9–34·1). Interpretation The chromosome 9p21 locus is a major cause of familial ALS in the Finnish population. Our data suggest the presence of a founder mutation for chromosome 9p21-linked ALS. Furthermore, the overlap with the risk haplotype recently reported for frontotemporal dementia provides further evidence of a shared genetic cause for these two neurodegenerative diseases. Funding National Institutes of Health and National Institute on Aging, Microsoft Research, ALS Association, Helsinki University Central Hospital, Finnish Academy, Finnish Medical Society Duodecim, and Kuopio University.

A Drosophila model for TDP-43 proteinopathy

Abstract: Neuropathology involving TAR DNA binding protein-43 (TDP-43) has been identified in a wide spectrum of neurodegenerative diseases collectively named as TDP-43 proteinopathy, including amyotrophic lateral sclerosis (ALS) and frontotemporal lobar dementia (FTLD). To test whether increased expression of wide-type human TDP-43 (hTDP-43) may cause neurotoxicity in vivo, we generated transgenic flies expressing hTDP-43 in various neuronal subpopulations. Expression in the fly eyes of the full-length hTDP-43, but not a mutant lacking its amino-terminal domain, led to progressive loss of ommatidia with remarkable signs of neurodegeneration. Expressing hTDP-43 in mushroom bodies (MBs) resulted in dramatic axon losses and neuronal death. Furthermore, hTDP-43 expression in motor neurons led to axon swelling, reduction in axon branches and bouton numbers, and motor neuron loss together with functional deficits. Thus, our transgenic flies expressing hTDP-43 recapitulate important neuropathological and clinical features of human TDP-43 proteinopathy, providing a powerful animal model for this group of devastating diseases. Our study indicates that simply increasing hTDP-43 expression is sufficient to cause neurotoxicity in vivo, suggesting that aberrant regulation of TDP-43 expression or decreased clearance of hTDP-43 may contribute to the pathogenesis of TDP-43 proteinopathy.

Corpus callosum involvement is a consistent feature of amyotrophic lateral sclerosis

Abstract: Objective: While the hallmark of amyotrophic lateral sclerosis (ALS) is corticospinal tract in combination with lower motor neuron degeneration, the clinical involvement of both compartments is characteristically variable and the site of onset debated. We sought to establish whether there is a consistent signature of cerebral white matter abnormalities in heterogeneous ALS cases. Methods: In this observational study, diffusion tensor imaging was applied in a whole-brain analysis of 24 heterogeneous patients with ALS and well-matched healthy controls. Tract-based spatial statistics were used, with optimized voxel-based morphometry of T1 images to determine any associated gray matter involvement. Results: A consistent reduction in fractional anisotropy was demonstrated in the corpus callosum of the ALS group, extending rostrally and bilaterally to the region of the primary motor cortices, independent of the degree of clinical upper motor neuron involvement. Matched regional radial diffusivity increase supported the concept of anterograde degeneration of callosal fibers observed pathologically. Gray matter reductions were observed bilaterally in primary motor and supplementary motor regions, and also in the anterior cingulate and temporal lobe regions. A post hoc group comparison model incorporating significant values for fractional anisotropy, radial diffusivity, and gray matter was 92% sensitive, 88% specific, with an accuracy of 90%. Conclusion: Callosal involvement is a consistent feature of ALS, independent of clinical upper motor neuron involvement, and may reflect independent bilateral cortical involvement or interhemispheric spread of pathology. The predominantly rostral corticospinal tract involvement further supports the concept of independent cortical degeneration even in those patients with ALS with predominantly lower motor neuron involvement clinically. Neurology ® 2010;75:1645–1652

Familial amyotrophic lateral sclerosis is associated with a mutation in D-amino acid oxidase

Abstract: We report a unique mutation in the D-amino acid oxidase gene (R199W DAO) associated with classical adult onset familial amyotrophic lateral sclerosis (FALS) in a three generational FALS kindred, after candidate gene screening in a 14.52 cM region on chromosome 12q22-23 linked to disease. Neuronal cell lines expressing R199W DAO showed decreased viability and increased ubiquitinated aggregates compared with cells expressing the wild-type protein. Similarly, lentiviral-mediated expression of R199W DAO in primary motor neuron cultures caused increased TUNEL labeling. This effect was also observed when motor neurons were cocultured on transduced astrocytes expressing R199W, indicating that the motor neuron cell death induced by this mutation is mediated by both cell autonomous and noncell autonomous processes. DAO controls the level of D-serine, which accumulates in the spinal cord in cases of sporadic ALS and in a mouse model of ALS, indicating that this abnormality may represent a fundamental component of ALS pathogenesis.

Mutations in CHMP2B in lower motor neuron predominant amyotrophic lateral sclerosis (ALS).

Abstract: Background: Amyotrophic lateral sclerosis (ALS), a common late-onset neurodegenerative disease, is associated with fronto-temporal dementia (FTD) in 3-10% of patients. A mutation in CHMP2B was recently identified in a Danish pedigree with autosomal dominant FTD. Subsequently, two unrelated patients with familial ALS, one of whom also showed features of FTD, were shown to carry missense mutations in CHMP2B. The initial aim of this study was to determine whether mutations in CHMP2B contribute more broadly to ALS pathogenesis. Methodology/Principal Findings: Sequencing of CHMP2B in 433 ALS cases from the North of England identified 4 cases carrying 3 missense mutations, including one novel mutation, p. Thr104Asn, none of which were present in 500 neurologically normal controls. Analysis of clinical and neuropathological data of these 4 cases showed a phenotype consistent with the lower motor neuron predominant (progressive muscular atrophy (PMA)) variant of ALS. Only one had a recognised family history of ALS and none had clinically apparent dementia. Microarray analysis of motor neurons from CHMP2B cases, compared to controls, showed a distinct gene expression signature with significant differential expression predicting disassembly of cell structure; increased calcium concentration in the ER lumen; decrease in the availability of ATP; down-regulation of the classical and p38 MAPK signalling pathways, reduction in autophagy initiation and a global repression of translation. Transfection of mutant CHMP2B into HEK-293 and COS-7 cells resulted in the formation of large cytoplasmic vacuoles, aberrant lysosomal localisation demonstrated by CD63 staining and impairment of autophagy indicated by increased levels of LC3-II protein. These changes were absent in control cells transfected with wild-type CHMP2B. Conclusions/Significance: We conclude that in a population drawn from North of England pathogenic CHMP2B mutations are found in approximately 1% of cases of ALS and 10% of those with lower motor neuron predominant ALS. We provide a body of evidence indicating the likely pathogenicity of the reported gene alterations. However, absolute confirmation of pathogenicity requires further evidence, including documentation of familial transmission in ALS pedigrees which might be most fruitfully explored in cases with a LMN predominant phenotype.

Chromosome 9p21 in sporadic amyotrophic lateral sclerosis in the UK and seven other countries: a genome-wide association study

Abstract: Summary Background Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease of motor neurons that results in progressive weakness and death from respiratory failure, commonly within about 3 years. Previous studies have shown association of a locus on chromosome 9p with ALS and linkage with ALS–frontotemporal dementia. We aimed to test whether this genomic region is also associated with ALS in an independent set of UK samples, and to identify risk factors associated with ALS in a further genome-wide association study that combined data from the independent analysis with those from other countries. Methods We collected samples from patients with sporadic ALS from 20 UK hospitals and obtained UK control samples from the control groups of the Depression Case Control study, the Bipolar Affective Case Control Study, and the British 1958 birth cohort DNA collection. Genotyping of DNA in this independent analysis was done with Illumina HumanHap550 BeadChips. We then undertook a joint genome-wide analysis that combined data from the independent set with published data from the UK, USA, Netherlands, Ireland, Italy, France, Sweden, and Belgium. The threshold for significance was p=0·05 in the independent analysis, because we were interested in replicating a small number of previously reported associations, whereas the Bonferroni-corrected threshold for significance in the joint analysis was p=2·20×10 −7 Findings After quality control, samples were available from 599 patients and 4144 control individuals in the independent set. In this analysis, two single nucleotide polymorphisms in a locus on chromosome 9p21.2 were associated with ALS: rs3849942 (p=2·22×10 −6 ; odds ratio [OR] 1·39, 95% CI 1·21–1·59) and rs2814707 (p=3·32×10 −6 ; 1·38, 1·20–1·58). In the joint analysis, which included samples from 4312 patients with ALS and 8425 control individuals, rs3849942 (p=4·64×10 −10 ; OR 1·22, 95% CI 1·15–1·30) and rs2814707 (p=4·72×10 −10 ; 1·22, 1·15–1·30) were associated with ALS. Interpretation We have found strong evidence of a genetic association of two single nucleotide polymorphisms on chromosome 9 with sporadic ALS, in line with findings from previous independent GWAS of ALS and linkage studies of ALS–frontotemporal dementia. Our findings together with these earlier findings suggest that genetic variation at this locus on chromosome 9 causes sporadic ALS and familial ALS–frontotemporal dementia. Resequencing studies and then functional analysis should be done to identify the defective gene. Funding ALS Therapy Alliance, the Angel Fund, the Medical Research Council, the Motor Neurone Disease Association of Great Britain and Northern Ireland, the Wellcome Trust, and the National Institute for Health Research Dementias and Neurodegenerative Diseases Research Network (DeNDRoN).

SPATACSIN mutations cause autosomal recessive juvenile amyotrophic lateral sclerosis

Abstract: The mutation of the spatacsin gene is the single most common cause of autosomal recessive hereditary spastic paraplegia with thin corpus callosum. Common clinical, pathological and genetic features between amyotrophic lateral sclerosis and hereditary spastic paraplegia motivated us to investigate 25 families with autosomal recessive juvenile amyotrophic lateral sclerosis and long-term survival for mutations in the spatascin gene. The inclusion criterion was a diagnosis of clinically definite amyotrophic lateral sclerosis according to the revised El Escorial criteria. The exclusion criterion was a diagnosis of hereditary spastic paraplegia with thin corpus callosum in line with an established protocol. Additional pathological and genetic evaluations were also performed. Surprisingly, 12 sequence alterations in the spatacsin gene (one of which is novel, IVS30 + 1 G > A) were identified in 10 unrelated pedigrees with autosomal recessive juvenile amyotrophic lateral sclerosis and long-term survival. The countries of origin of these families were Italy, Brazil, Canada, Japan and Turkey. The variants seemed to be pathogenic since they co-segregated with the disease in all pedigrees, were absent in controls and were associated with amyotrophic lateral sclerosis neuropathology in one member of one of these families for whom central nervous system tissue was available. Our study indicates that mutations in the spatascin gene could cause a much wider spectrum of clinical features than previously recognized, including autosomal recessive juvenile amyotrophic lateral sclerosis.

Riluzole, Neuroprotection and Amyotrophic Lateral Sclerosis

Abstract: Amyotrophic lateral sclerosis (ALS) is a universally fatal neurodegenerative disease of the human motor system. Aetiological mechanisms implicated in the development of ALS have been linked to the glutamatergic neurotransmitter system, with destruction of motor neurons triggered through excessive activation of glutamate receptors at the synaptic cleft. This 'excitotoxicity' theory of ALS gave rise to the development of therapeutic approaches and ultimately clinical trials involving riluzole, initially thought to act solely as an inhibitor of glutamate release. Subsequent effects of riluzole have been postulated to include indirect antagonism of glutamate receptors, in addition to inactivation of neuronal voltage-gated Na+ channels. Riluzole remains the only disease-modifying therapy available to patients with ALS. Despite having been clinically available since the mid-1990 s, the in vivo pharmacological targets of riluzole have been poorly defined. An improved understanding concerning the potential neuroprotective mechanisms of riluzole may unearth pathophysiological processes that mediate neurodegeneration in ALS. The present review summarises the known chemical and pharmacological properties of riluzole. The failure of other putative neuroprotective therapies to demonstrate positive treatment outcomes in this intractable disease will be reviewed. Finally, the hypothesis that Na+ conductances may be involved in the processes of neuronal and axonal degeneration in ALS will be explored.