Hereditary Amyotrophic Lateral Sclerosis Research Articles

Optogenetic control of GGGGCC repeat-containing RNA phase transition

The GGGGCC (G4C2) hexanucleotide repeat expansion in the C9ORF72 gene is a major cause of both hereditary amyotrophic lateral sclerosis and familial frontotemporal dementia. Recent studies have shown that G4C2 hexanucleotide repeat-containing RNA transcripts ((G4C2)n RNA) could go through liquid-liquid phase separation to form RNA foci, which may elicit neurodegeneration. However, the direct causality between these abnormal RNA foci and neuronal toxicity remains to be demonstrated. Here we introduce an optogenetic control system that can induce the assembly and phase separation of (G4C2)n RNA foci with blue light illumination in human cells, by fusing a specific (G4C2)n RNA binding protein as the linker domain to Cry2, a protein that oligomerizes in response to blue light. Our results demonstrate that a higher number of G4C2 repeats have the potential to be induced into more RNA foci in the cells. Both spontaneous and induced RNA foci display liquid-like properties according to FRAP measurements. Computational simulation shows strong consistency with the experimental results and supports the effect of our system to promote the propensity of (G4C2)n RNA towards phase separation. This system can thus be used to investigate whether (G4C2)n RNA foci would disrupt normal cellular processes and lead to pathological phenotypes relevant to repeat expansion disorders.

Bisperoxovanadium promotes motor neuron survival in models of amyotrophic lateral sclerosis

The objective of our study was to test the therapeutic efficacy of a small molecule, bisperoxovanadium (bpV), in cell culture and animal models of the motor neuron (MN) disease, amyotrophic lateral sclerosis (ALS). A common cause of hereditary ALS, a mutation in the superoxide dismutase 1 protein (mSOD1G93A), is well studied and available models recapitulate human disease progression and MN loss. BpV is a known inhibitor of the phosphatase and tensin homolog, PTEN, and we have shown that bpV promotes MN survival in traumatic nervous system injury models. PTEN is well known as a negative regulator of phosphatidylinositol-3-kinase (PI3K)/Akt signaling, and this signaling pathway is linked to bpV's neuroprotective effects. We hypothesized that bpV treatment of both a mSOD1G93A MN cell line and mouse model ofALS would prevent MN degeneration and death. To test this hypothesis, we administered 400 μg/kg bpV intraperitoneally daily to mSOD1G93A mice between 70 and 90 days of age, which is a period of lumbar spinal cord MN death in these mice. After treatment, we collected tissue and examined immunolabeling of MNs in cryosections of the lumbar spinal cord and microglial reactivity, which can contribute to neuroinflammation and exacerbate MN loss. For our in vitro model, we cultured motor neuron-like NSC-34 cells transfected with a plasmid to overexpress mutant SOD1G93A, differentiated these cells for four days, and starved them in a serum-free medium for 24 hours both with and without bpV. Furthermore, we administered an inhibitor of PI3K/Akt signaling, LY294002, in the cell culture model to determine bpV's influence on PTEN and elucidate a potential mechanism of its action. We found that 20 days of bpV therapy significantly reduced lumbar ventral horn MN loss (p<0.05) but did not significantly influence microglial reactivity in mSOD1G93A mice. BpV improved neuron viability in vitro, and PI3K/Akt signaling inhibition reversed this effect (both p<0.05). In conclusion, our study indicates that bpV treatment could be a useful neuroprotective therapy for ALS.

Homeostatic plasticity can be induced and expressed to restore synaptic strength at neuromuscular junctions undergoing ALS-related degeneration.

Amyotrophic lateral sclerosis (ALS) is debilitating neurodegenerative disease characterized by motor neuron dysfunction and progressive weakening of the neuromuscular junction (NMJ). Hereditary ALS is strongly associated with variants in the human C9orf72 gene. We have characterized C9orf72 pathology at the Drosophila NMJ and utilized several approaches to restore synaptic strength in this model. First, we demonstrate a dramatic reduction in synaptic arborization and active zone number at NMJs following C9orf72 transgenic expression in motor neurons. Further, neurotransmission is similarly reduced at these synapses, consistent with severe degradation. However, despite these defects, C9orf72 synapses still retain the ability to express presynaptic homeostatic plasticity, a fundamental and adaptive form of NMJ plasticity in which perturbation to postsynaptic neurotransmitter receptors leads to a retrograde enhancement in presynaptic release. Next, we show that these endogenous but dormant homeostatic mechanisms can be harnessed to restore synaptic strength despite C9orf72 pathogenesis. Finally, activation of regenerative signaling is not neuroprotective in motor neurons undergoing C9orf72 toxicity. Together, these experiments define synaptic dysfunction at NMJs experiencing ALS-related degradation and demonstrate the potential to activate latent plasticity as a novel therapeutic strategy to restore synaptic strength.

IN VIVO TAU IMAGING BY POSITRON EMISSION TOMOGRAPHY IN PATIENTS WITH C9ORF72 HEXANUCLEOTIDE REPEAT EXPANSIONS

C9orf72 repeat-related disease is the most common cause of hereditary amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). Similar to Alzheimer's disease (AD), some C9orf72 expansion carriers who are cognitively impaired have been shown to have increases in tau neurofibrillary tangles at autopsy. Recently developed tau positron emission tomography (PET) imaging could potentially be an in vivo method to assess tau accumulation in C9orf72-related disease. We evaluated AV-1451 PET as a diagnostic and prognostic biomarker for disease caused by C9orf72 repeat expansions. Eight C9orf72 expansion carriers (mean age: 63.4 ± 4.1 years) and sixteen age and gender matched cognitively normal individuals (mean age: 63.6 ± 5.0 years) underwent tau PET imaging. Regional AV-1451 SUVR normalized to brainstem intensity from various brain regions was used to assess tau deposition between groups and corrected for multiple comparisons using a false discovery rate of 1%. Pearson correlation was used to evaluate tau deposition SUVR values and clinical characteristics including ALS-FRS (ALS functional ratting scale), disease duration, neuropsychiatric measures, as well as AD markers in CSF. Symptomatic C9orf72 expansion carriers had an ALS-FRS of 26 ± 10 (range 13–39), a disease duration of 2.59 ± 1.16 years (range 1.21–4.19 years), and MMSE score of 27.0 ± 3.1. Three quarters of the patients were symptomatic. C9orf72 expansion carriers had increased AV-1451 uptake in the entorhinal cortex compared to a reference population of cognitively normal controls (C9: 1.09±0.29, control: 0.73±0.11, p=0.0002). The entorhinal AV-1451 SUVR exceeds an a priori cutoff for tau deposition of 1.00 for brainstem-normalized values in 75% of C9orf72 subjects and in none of the controls. AV-1451 uptake within entorhinal, limbic, and cortical areas, corresponding to regional progression of tau pathology by Braak staging, did not correlate with clinical measures of severity (ALS-FRS and disease duration), neurocognitive performance defined by MMSE, executive, and visuospatial measures, or CSF markers of disease (Ab, total tau, and phospho-tau). C9orf72 expansion carriers exhibited increased AV-1451 uptake in entorhinal cortex compared to controls suggesting that tau deposition may contribute to development of mild cognitive impairment in this condition.

Mutant HSPB1 causes loss of translational repression by binding to PCBP1, an RNA binding protein with a possible role in neurodegenerative disease

The small heat shock protein HSPB1 (Hsp27) is an ubiquitously expressed molecular chaperone able to regulate various cellular functions like actin dynamics, oxidative stress regulation and anti-apoptosis. So far disease causing mutations in HSPB1 have been associated with neurodegenerative diseases such as distal hereditary motor neuropathy, Charcot-Marie-Tooth disease and amyotrophic lateral sclerosis. Most mutations in HSPB1 target its highly conserved α-crystallin domain, while other mutations affect the C- or N-terminal regions or its promotor. Mutations inside the α-crystallin domain have been shown to enhance the chaperone activity of HSPB1 and increase the binding to client proteins. However, the HSPB1-P182L mutation, located outside and downstream of the α-crystallin domain, behaves differently. This specific HSPB1 mutation results in a severe neuropathy phenotype affecting exclusively the motor neurons of the peripheral nervous system. We identified that the HSPB1-P182L mutant protein has a specifically increased interaction with the RNA binding protein poly(C)binding protein 1 (PCBP1) and results in a reduction of its translational repressive activity. RNA immunoprecipitation followed by RNA sequencing on mouse brain lead to the identification of PCBP1 mRNA targets. These targets contain larger 3′- and 5′-UTRs than average and are enriched in an RNA motif consisting of the CTCCTCCTCCTCC consensus sequence. Interestingly, next to the clear presence of neuronal transcripts among the identified PCBP1 targets we identified known genes associated with hereditary peripheral neuropathies and hereditary spastic paraplegias. We therefore conclude that HSPB1 can mediate translational repression through interaction with an RNA binding protein further supporting its role in neurodegenerative disease.

Genotype-phenotype correlations of amyotrophic lateral sclerosis.

Amyotrophic lateral sclerosis (ALS) is a devastating neurodegenerative disease characterized by progressive neuronal loss and degeneration of upper motor neuron (UMN) and lower motor neuron (LMN). The clinical presentations of ALS are heterogeneous and there is no single test or procedure to establish the diagnosis of ALS. Most cases are diagnosed based on symptoms, physical signs, progression, EMG, and tests to exclude the overlapping conditions. Familial ALS represents about 5 ~ 10 % of ALS cases, whereas the vast majority of patients are sporadic. To date, more than 20 causative genes have been identified in hereditary ALS. Detecting the pathogenic mutations or risk variants for each ALS individual is challenging. However, ALS patients carrying some specific mutations or variant may exhibit subtly distinct clinical features. Unraveling the respective genotype-phenotype correlation has important implications for the genetic explanations. In this review, we will delineate the clinical features of ALS, outline the major ALS-related genes, and summarize the possible genotype-phenotype correlations of ALS.

Genotype-phenotype relationship in hereditary amyotrophic lateral sclerosis.

Amyotrophic lateral sclerosis (ALS) is the most common adult-onset motor neuron disease. It is characterized by neuronal loss and degeneration of the upper motor neurons (UMNs) and lower motor neurons (LMNs), and is usually fatal due to respiratory failure within 3–5 years of onset. Although approximately 5–10 % of patients with ALS have an inherited form of the disease, the distinction between hereditary and apparently sporadic ALS (SALS) seems to be artificial. Thus, genetic factors play a role in all types of ALS, to a greater or lesser extent. During the decade of upheaval, the evolution of molecular genetics technology has rapidly advanced our genetic knowledge about the causes of ALS, and the relationship between the genetic subtypes and clinical phenotype. In this review, we will focus on the possible genotype-phenotype correlation in hereditary ALS. Uncovering the identity of the genetic factors in ALS will not only improve the accuracy of ALS diagnosis, but may also provide new approaches for preventing and treating the disease.Electronic supplementary materialThe online version of this article (doi:10.1186/s40035-015-0036-y) contains supplementary material, which is available to authorized users.

Genetisk sammenheng mellom amyotrofisk lateral sklerose og frontotemporal demens

Amyotrophic lateral sclerosis (ALS) has traditionally been considered purely as a motor condition with a progressive loss of upper and lower motor neurons, and without cognitive or behavioural impairment. In 2011 a new genetic mutation that may cause both ALS and frontotemporal dementia (FTD) was detected. In light of this discovery, the article describes genetic and clinical characteristics of ALS and frontotemporal dementia. The article is based on a literature search in PubMed. Up to 50% of ALS patients develop some cognitive impairment, while 3-15% develop frontotemporal dementia. The recently discovered C9ORF72 mutation accounts for 20-50% of hereditary ALS and possibly up to 25% of sporadic cases. The mutation is the most common cause of ALS. Patients with C9ORF72 mutation are characterised by earlier disease onset, reduced survival after diagnosis, more frequent cognitive and behavioural dysfunction, and familial disposition for ALS and frontotemporal dementia. Cognitive and behavioural changes in amyotrophic lateral sclerosis are common, and can appear along a clinical continuum with development of frontotemporal dementia over time. Detection of the C9ORF72 mutation poses a challenge to our knowledge and management of patients with both hereditary and sporadic ALS.

Nuclear factor ? B expression in patients with sporadic amyotrophic lateral sclerosis and hereditary amyotrophic lateral sclerosis with optineurin mutations

Nuclear factor κ B (NF-κB) is involved in the pathogenesis of a number of neurodegenerative disorders with neuroinflammation. In order to clarify the role of NF-κB in ALS, immunohistochemical studies with an antibody that recognizes the p65 subunit of NF-κB were performed on the spinal anterior horn of 4 patients with sporadic ALS (sALS), 1 patient with optineurin-mutated ALS (OPTN-ALS), and 3 normal controls (NC). In patients with sALS or OPTN-ALS, the expression pattern of NF-κB was altered when compared to that of NC; NF-κB immunoreactivity tended to be absent from neuronal nucleus and was increased in microglia. The down-regulation of NF-κB in neuronal nucleus might contribute to a loss of neuroprotection, or neurons with nuclear NF-κB might be lost immediately after its activation. The microglial induction of NF-κB might contribute to neuroinflammation. In conclusion, NF-κB signaling pathway could have a key role in the pathomechanism of ALS.

Hereditary motor neuron disease in a large Norwegian family with a “H46R” substitution in the superoxide dismutase 1 gene

Mutant genes associated with Charcot Marie Tooth type 2, distal hereditary motor neuropathy and familial amyotrophic lateral sclerosis may cause overlapping clinical phenotypes. We performed whole genome linkage analysis, haplotype analysis, sequencing and detailed clinical and neurophysiological investigations in a large Norwegian kindred with a condition that clinically had been classified as Charcot Marie Tooth type 2. The mutation c.140A>G, p.His47Arg (alias p.His46Arg or H46R) in the superoxide dismutase 1 gene (SOD1) segregated with the disease. The patients present a hereditary motor neuropathy-like clinical picture and long survival (mean 29years). To our knowledge, this is the first extensive report describing a large non-Japanese kindred. The prognostic implications of the condition seen in this family have little in common with what is normally associated with sporadic amyotrophic lateral sclerosis and illustrates the complexity of the genetic etiology of lower motor neuron disease.

Clinical genetics of amyotrophic lateral sclerosis: what do we really know?

Hereditary amyotrophic lateral sclerosis (ALS) encompasses a group of genetic disorders characterized by adult-onset loss of the lower and upper motor neuron systems, often with involvement of other parts of the nervous system. Cases of hereditary ALS have been attributed to mutations in 12 different genes, the most common being SOD1, FUS and TARDBP-mutations in the other genes are rare. The identified genes explain 25-35% of cases of familial ALS, but identifying the remaining genes has proved difficult. Only a few genes seem to account for significant numbers of ALS cases, with many others causing a few cases each. Hereditary ALS can be inherited in an autosomal dominant, autosomal recessive or X-linked manner, and families with low disease penetrance are frequently observed. In such families, the genetic predisposition may remain unnoticed, so many patients carry a diagnosis of isolated or sporadic ALS. The only clinical feature that distinguishes recognized hereditary from apparently sporadic ALS is a lower mean age of onset in the former. All the clinical features reported in hereditary cases (including signs of extrapyramidal, cerebellar or cognitive involvement) have also been observed in sporadic cases. Genetic counseling and risk assessment in relatives depend on establishing the specific gene defect and the disease penetrance in the particular family.

Sensorimotor and cognitive functions in a SOD1 G37R transgenic mouse model of amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a neurological disorder involving degeneration of motor neurons in brain and spinal cord, leading to progressive atrophy of skeletal muscles and, ultimately, paralysis and death. Copper-mediated oxidative damage is proposed to play a critical role in the pathogenesis of Cu/Zn superoxide dismutase (SOD1) – linked hereditary amyotrophic lateral sclerosis. To understand more clearly the pathogenesis of sensorimotor dysfunction and to find the most appropriate methods for early detection of symptoms and for monitoring them across time, a murine model was assessed at three time points (5, 8, and 11 months). Transgenic mice with the G37R mutation of human SOD1 exhibited earliest signs of dysfunction at 8 months in terms of a pathological hindpaw clasping reflex, as well as slowed movement time on a suspended bar, anomalies in footprint patterns, weaker grip strength, raised somatosensory thresholds, and deficits in passive avoidance learning, yielding a margin of 3–4 months before death to test experimental therapies.

Photo-Induced Cross-Linking of Unmodified Proteins (PICUP) Applied to Amyloidogenic Peptides

The assembly of amyloidogenic proteins into toxic oligomers is a seminal event in the pathogenesis of protein misfolding diseases, including Alzheimer's, Parkinson's, and Huntington's diseases, hereditary amyotrophic lateral sclerosis, and type 2 diabetes. Owing to the metastable nature of these protein assemblies, it is difficult to assess their oligomer size distribution quantitatively using classical methods, such as electrophoresis, chromatography, fluorescence, or dynamic light scattering. Oligomers of amyloidogenic proteins exist as metastable mixtures, in which the oligomers dissociate into monomers and associate into larger assemblies simultaneously. PICUP stabilizes oligomer populations by covalent cross-linking and when combined with fractionation methods, such as sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) or size-exclusion chromatography (SEC), PICUP provides snapshots of the oligomer size distributions that existed before cross-linking. Hence, PICUP enables visualization and quantitative analysis of metastable protein populations and can be used to monitor assembly and decipher relationships between sequence modifications and oligomerization(1). Mechanistically, PICUP involves photo-oxidation of Ru(2+) in a tris(bipyridyl)Ru(II) complex (RuBpy) to Ru(3+) by irradiation with visible light in the presence of an electron acceptor. Ru(3+) is a strong one-electron oxidizer capable of abstracting an electron from a neighboring protein molecule, generating a protein radical(1,2). Radicals are unstable, highly-reactive species and therefore disappear rapidly through a variety of intra- and intermolecular reactions. A radical may utilize the high energy of an unpaired electron to react with another protein monomer forming a dimeric radical, which subsequently loses a hydrogen atom and forms a stable, covalently-linked dimer. The dimer may then react further through a similar mechanism with monomers or other dimers to form higher-order oligomers. Advantages of PICUP relative to other photo- or chemical cross-linking methods(3,4) include short (<or=1 s) exposure to non-destructive visible light, no need for pre facto modification of the native sequence, and zero-length covalent cross-linking. In addition, PICUP enables cross-linking of proteins within wide pH and temperature ranges, including physiologic parameters. Here, we demonstrate application of PICUP to cross-linking of three amyloidogenic proteins the 40- and 42-residue amyloid beta-protein variants (Abeta40 and Abeta42), and calcitonin, and a control protein, growth-hormone releasing factor (GRF).

Photo-Induced Cross-Linking of Unmodified Proteins (PICUP) Applied to Amyloidogenic Peptides

The assembly of amyloidogenic proteins into toxic oligomers is a seminal event in the pathogenesis of protein misfolding diseases, including Alzheimer's, Parkinson's, and Huntington's diseases, hereditary amyotrophic lateral sclerosis, and type 2 diabetes. Owing to the metastable nature of these protein assemblies, it is difficult to assess their oligomer size distribution quantitatively using classical methods, such as electrophoresis, chromatography, fluorescence, or dynamic light scattering. Oligomers of amyloidogenic proteins exist as metastable mixtures, in which the oligomers dissociate into monomers and associate into larger assemblies simultaneously. PICUP stabilizes oligomer populations by covalent cross-linking and when combined with fractionation methods, such as sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) or size-exclusion chromatography (SEC), PICUP provides snapshots of the oligomer size distributions that existed before cross-linking. Hence, PICUP enables visualization and quantitative analysis of metastable protein populations and can be used to monitor assembly and decipher relationships between sequence modifications and oligomerization1. Mechanistically, PICUP involves photo-oxidation of Ru2+ in a tris(bipyridyl)Ru(II) complex (RuBpy) to Ru3+ by irradiation with visible light in the presence of an electron acceptor. Ru3+ is a strong one-electron oxidizer capable of abstracting an electron from a neighboring protein molecule, generating a protein radical1,2. Radicals are unstable, highly-reactive species and therefore disappear rapidly through a variety of intra- and intermolecular reactions. A radical may utilize the high energy of an unpaired electron to react with another protein monomer forming a dimeric radical, which subsequently loses a hydrogen atom and forms a stable, covalently-linked dimer. The dimer may then react further through a similar mechanism with monomers or other dimers to form higher-order oligomers. Advantages of PICUP relative to other photo- or chemical cross-linking methods3,4 include short (≤1 s) exposure to non-destructive visible light, no need for pre facto modification of the native sequence, and zero-length covalent cross-linking. In addition, PICUP enables cross-linking of proteins within wide pH and temperature ranges, including physiologic parameters. Here, we demonstrate application of PICUP to cross-linking of three amyloidogenic proteins the 40- and 42-residue amyloid β-protein variants (Aβ40 and Aβ42), and calcitonin, and a control protein, growth-hormone releasing factor (GRF).

Designing siRNA That Distinguish between Genes That Differ by a Single Nucleotide

Small interfering RNAs (siRNAs), the guides that direct RNA interference (RNAi), provide a powerful tool to reduce the expression of a single gene in human cells. Ideally, dominant, gain-of-function human diseases could be treated using siRNAs that specifically silence the mutant disease allele, while leaving expression of the wild-type allele unperturbed. Previous reports suggest that siRNAs can be designed with single nucleotide specificity, but no rational basis for the design of siRNAs with single nucleotide discrimination has been proposed. We systematically identified siRNAs that discriminate between the wild-type and mutant alleles of two disease genes: the human Cu, Zn superoxide dismutase (SOD1) gene, which contributes to the progression of hereditary amyotrophic lateral sclerosis through the gain of a toxic property, and the huntingtin (HTT) gene, which causes Huntington disease when its CAG-repeat region expands beyond approximately 35 repeats. Using cell-free RNAi reactions in Drosophila embryo lysate and reporter assays and microarray analysis of off-target effects in cultured human cells, we identified positions within an siRNA that are most sensitive to mismatches. We also show that purine:purine mismatches imbue an siRNA with greater discriminatory power than other types of base mismatches. siRNAs in which either a G:U wobble or a mismatch is located in the “seed” sequence, the specialized siRNA guide region responsible for target binding, displayed lower levels of selectivity than those in which the mismatch was located 3′ to the seed; this region of an siRNA is critical for target cleavage but not siRNA binding. Our data suggest that siRNAs can be designed to discriminate between the wild-type and mutant alleles of many genes that differ by just a single nucleotide.

Effects of overexpression of the cytoplasmic copper-zinc superoxide dismutase on the survival of neurons in vitro.

The cytoplasmic copper-zinc superoxide dismutase (Cu, Zn SOD; SOD-1) is an abundant and well-conserved intracellular antioxidant enzyme which has been implicated in a number of oxidative stress mediated phenomena, especially Down Syndrome, in which SOD-1 activity is increased due to triplication of chromosome 21 containing the gene and, in hereditary amyotrophic lateral sclerosis, in which the gene is mutated. Overexpression of SOD-1 could theoretically, therefore, lead to increased vulnerability to oxidative stress in two distinct manners: increasing steady-state hydrogen peroxide levels or increasing toxic side reactions. We used two mouse neuronal culture systems--one in which the murine chromosome containing SOD-1 is triplicated and one in which human SOD-1 is a transgene--to test the effect of overexpression of this enzyme on antioxidant status in general and specifically on glutamate mediated oxidative stress. We found that SOD-1 overexpression increases antioxidant status at the same time it decreases vulnerability to glutamate.

Apoptosis in neurodegenerative disorders: potential for therapy by modifying gene transcription.

Apoptotic, rather than necrotic, nerve cell death now appears as likely to underlie a number of common neurological conditions including stroke, Alzheimer's disease, Parkinson's disease, hereditary retinal dystrophies and Amyotrophic Lateral Sclerosis. Apoptotic neuronal death is a delayed, multistep process and therefore offers a therapeutic opportunity if one or more of these steps can be interrupted or reversed. Research is beginning to show how specific macromolecules play a role in determining the apoptotic death process. We are particularly interested in the critical nature of gradual mitochondrial failure in the apoptotic process and propose that a maintenance of mitochondrial function through the pharmacological modulation of gene expression offers an opportunity for the effective treatment of some types of neurological dysfunction. Our research into the development of small diffusible molecules that reduce apoptosis has grown from studies of the irreversible MAO-B inhibitor (-)-deprenyl. (-)-Deprenyl can reduce neuronal death independently of MAO-B inhibition even after neurons have sustained seemingly lethal damage. (-)-Deprenyl can also influence the process outgrowth of some glial and neuronal populations and can reduce the concentrations of oxidative radicals in damaged cells at concentrations too small to inhibit MAO. In accord with earlier work of others, we showed that (-)-deprenyl alters the expression of a number of mRNAs or of proteins in nerve and glial cells and that the alterations in gene expression/protein synthesis are the result of a selective action on transcription. The alterations in gene expression/protein synthesis are accompanied by a decrease in DNA fragmentation characteristic of apoptosis and the death of responsive cells. The onco-proteins Bcl-2 and Bax and the scavenger proteins Cu/Zn superoxide dismutase (SOD1) and Mn superoxide dismutase (SOD-2) are among the 40-50 proteins whose synthesis is altered by (-)-deprenyl. Since mitochondrial membrane potential correlates with mitochondrial ATP production, we have used confocal laser imaging techniques in living cells to show that the transcriptional changes induced by (-)-deprenyl result in a maintenance of mitochondrial membrane potential, a decrease in intramitochondrial calcium and a decrease in cytoplasmic oxidative radical levels. We therefore propose that (-)-deprenyl acts on gene expression to maintain mitochondrial function and decrease cytoplasmic oxidative radical levels and thereby reduces apoptosis. An understanding of the molecular steps by which (-)-deprenyl selectively alters transcription may lead to the development of new therapies for neurodegenerative diseases.

Neuroscientists seek answers to brain function and disease. Faulty protein linked to ALS.

Washington, D.C.—Neuroscientists gathered here late last month for their largest annual meeting ever. The presentations covered a wide range of topics, from spinal cord injury. and obesity (Science, 29 November, p. 1466) to learning and neurodegenerative disease. While neuroscientists have identified the gene at fault in some cases of hereditary amyotrophic lateral sclerosis (also known as ALS or Lou Gehrig9s disease), the cause of the much larger number of sporadic (nonhereditary) cases is unknown. Now researchers have found that synthesis of a protein needed for normal handling of the neurotransmitter glutamate is defective in half of sporadic ALS patients. If confirmed, the discovery might help explain what causes the neurodegeneration of the patients, because the defect could lead to a buildup of glutamate, which can be toxic to neurons in high concentrations.

Phenotypic and genotypic heterogeneity of dominantly inherited amyotrophic lateral sclerosis.

Twenty-seven cases of hereditary amyotrophic lateral sclerosis (ALS), belonging to 8 families, are reported. The analysis of the pedigrees suggests an autosomal dominant transmission, apparently with incomplete penetration. The mean age at onset of symptoms was 50.3 (SD 12.4) years. The mean duration of the disease was 31.2 (SD 20.4) months, ranging from 9 to 86. The median survival time was 24 months. The degree of variation of some quantitative characters, both within and among families, was statistically analyzed. The results support the hypothesis of a phenotypic and genetic heterogeneity of autosomal dominant transmitted ALS.

Hereditary amyotrophic lateral sclerosis

A Spanish family transmits, as an autosomal dominant trait, a form of amyotrophic lateral sclerosis characterized by an unusually prolonged evolution of the disease in all affected members. Precocity and persistence of muscle cramps, presence of unilateral proximal segmental myoclonus and early abolition of ankle jerks are other clinical features conspicuous in this family. This type of hereditary ALS of non-Chamorro origin and prolonged evolution is rare.