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The objective was to test the hypothesis that a described association between homozygosity for a 50bp deletion in the SOD1 promoter 1684bp upstream of the SOD1 ATG and an increased age of onset in SALS can be replicated in additional SALS and control sample sets from other populations. Our second objective was to examine whether this deletion attenuates expression of the SOD1 gene. Genomic DNA from more than 1200 SALS cases from Ireland, Scotland, Quebec and the USA was genotyped for the 50bp SOD1 promoter deletion. Reporter gene expression analysis, electrophoretic mobility shift assays and chromatin immunoprecipitation studies were utilized to examine the functional effects of the deletion. The genetic association for homozygosity for the promoter deletion with an increased age of symptom onset was confirmed overall in this further study (p=0.032), although it was only statistically significant in the Irish subset, and remained highly significant in the combined set of all cohorts (p=0.001). Functional studies demonstrated that this polymorphism reduces the activity of the SOD1 promoter by approximately 50%. In addition we revealed that the transcription factor SP1 binds within the 50bp deletion region in vitro and in vivo. Our findings suggest the hypothesis that this deletion reduces expression of the SOD1 gene and that levels of the SOD1 protein may modify the phenotype of SALS within selected populations.

We report a patient with autosomal-dominant amyotrophic lateral sclerosis (ALS) and a sequence variation in the SOD1 promoter region, located in the conserved TATA box motif (TATAAA→TGTAAA). Functional promoter studies of this variant in an in vitro system showed moderate reduction in transcriptional activity of SOD1. This variant was present in only two of 301 individuals with sporadic amyotrophic lateral sclerosis, was not detected in 396 matched controls, and was recently reported in dbSNP (rs7277748). Our data suggest that this TATA box defect is not a disease-causing mutation or susceptibility factor for ALS but rather a rare polymorphism with a potential effect on SOD1 gene expression. Muscle Nerve, 2007

Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative condition that results in the death of the large motor neurons of the brain and spinal cord. Familial ALS accounts for 10% of all ALS cases. Approximately 25% of these cases are due to mutations in the SOD1 gene. Several lines of evidence argue that mutant SOD1 causes ALS by a toxic gain of function. We therefore anticipate that measures that reduce the levels of mutant SOD1 expression should be beneficial in mutant SOD1-associated ALS patients. Mitomycin C (MC) is an antitumor antibiotic previously demonstrated to reduce SOD1 expression in a reporter gene system. We investigated whether MC reduces endogenous SOD1 expression levels both in vitro and in vivo. MC reduced human and rat SOD1 protein levels in vitro, with a concomitant decrease in actin and increase in p53 protein levels, as detected by Western blotting. However, this decrease in SOD1 protein levels was paralleled by a similar decrease in cell viability. In contrast, intracerebroventricular administration of MC to rats and mice failed to produce any effect on brain or spinal cord SOD1 protein levels. Our data indicate the apparent inhibition of SOD1 expression by MC is a non-specific consequence of MC-induced cellular toxicity.

Familial amyotrophic lateral sclerosis (ALS) accounts for 10% of all ALS cases; 12-23% are associated with mutations in the Cu/Zn superoxide dismutase gene (SOD1). All ALS-linked SOD1 mutations present with a dominant pattern of inheritance apart from the aspartate to alanine mutation in exon 4 (D90A). This mutation has been observed in dominant, recessive and apparently sporadically cases. SOD1(D90A/D90A) ALS cases have a very slow disease progression (>10 years), raising the hypothesis that modifier genes linked to SOD1 ameliorate the phenotype of recessively inherited SOD1(D90A/D90A) mutations. Previous sequence analysis of a conserved haplotype region around the SOD1 gene did not reveal any functional polymorphisms within known coding or putative regulatory regions. In the current study we expanded the previous analyses by sequencing the entire SOD1 conserved haplotypic region. Although many polymorphisms were identified, none of these variants explain the slowly progressive phenotype observed in patients with recessive SOD1(D90A) mutations. This study disproves the hypothesis that there is a tightly linked genetic protective factor specifically located close to the SOD1 gene in SOD1(D90A) mediated ALS.

Amyotrophic lateral sclerosis (ALS) is a spontaneous, relentlessly progressive motor neuron disease, usually resulting in death from respiratory failure within 3 years. Variation in the genes SOD1 and TARDBP accounts for a small percentage of cases, and other genes have shown association in both candidate gene and genome-wide studies, but the genetic causes remain largely unknown. We have performed two independent parallel studies, both implicating the RNA polymerase II component, ELP3, in axonal biology and neuronal degeneration. In the first, an association study of 1884 microsatellite markers, allelic variants of ELP3 were associated with ALS in three human populations comprising 1483 people (P = 1.96 x 10(-9)). In the second, an independent mutagenesis screen in Drosophila for genes important in neuronal communication and survival identified two different loss of function mutations, both in ELP3 (R475K and R456K). Furthermore, knock down of ELP3 protein levels using antisense morpholinos in zebrafish embryos resulted in dose-dependent motor axonal abnormalities [Pearson correlation: -0.49, P = 1.83 x 10(-12) (start codon morpholino) and -0.46, P = 4.05 x 10(-9) (splice-site morpholino), and in humans, risk-associated ELP3 genotypes correlated with reduced brain ELP3 expression (P = 0.01). These findings add to the growing body of evidence implicating the RNA processing pathway in neurodegeneration and suggest a critical role for ELP3 in neuron biology and of ELP3 variants in ALS.

Familial amyotrophic lateral sclerosis (ALS) accounts for 10% of all ALS. Approximately 20% of cases are due to mutations in the Cu/Zn superoxide dismutase gene (SOD1). In North America, SOD1(A4V) is the most common SOD1 mutation. Carriers of the SOD1(A4V) mutation share a common phenotype with rapid disease progression and death on average occurring at 1.4 years (versus 3-5 years with other dominant SOD1 mutations). Previous studies of SOD1(A4V) carriers identified a common haplotype around the SOD1 locus, suggesting a common founder for most SOD1(A4V) patients. In the current study we sequenced the entire common haplotypic region around SOD1 to test the hypothesis that polymorphisms in either previously undescribed coding regions or non-coding regions around SOD1 are responsible for the more aggressive phenotype in SOD1(A4V)-mediated ALS. We narrowed the conserved region around the SOD1 gene in SOD1(A4V) ALS to 2.8Kb and identified five novel SNPs therein. None of these variants was specifically found in all SOD1(A4V) patients. It therefore appears likely that the aggressive nature of the SOD1(A4V) mutation is not a result of a modifying factor within the region around the SOD1 gene. Founder analysis estimates that the A4V mutation occurred 540 generations (approximately 12,000 years) ago (95% CI 480-700). The conserved minimal haplotype is statistically more similar to Asian than European population DNA sets, suggesting that the A4V mutation arose in native Asian-Americans who reached the Americas through the Bering Strait.

Mutations in the copper zinc superoxide dismutase gene (SOD1) are found in 20% of familial and 3% of sporadic ALS patients. SOD1 protein aggregation can be detected in motor neurons of mutation-negative sporadic cases but a pathogenic role for wild-type SOD1 in ALS has not been demonstrated. In this study of 233 ALS cases and 248 controls the authors found no significant association between four individual single nucleotide polymorphisms and a deletion spanning the SOD1 locus (or their combined haplotypes), and disease susceptibility, or phenotype.

More than 100 different heterozygous mutations in copper/zinc superoxide dismutase (SOD1) have been found in patients with amyotrophic lateral sclerosis (ALS), a fatal neurodegenerative disease. Uniquely, D90A-SOD1 has been identified in recessive, dominant and apparently sporadic pedigrees. The phenotype of homozygotes is stereotyped with an extended survival, whereas that of affected heterozygotes varies. The frequency of D90A-SOD1 is 50 times higher in Scandinavia (2.5%) than elsewhere, though ALS prevalence is not raised there. Our earlier study indicated separate founders for recessive and dominant/sporadic ALS and we proposed a disease-modifying factor linked to the recessive mutation. Here we have doubled our sample set and employed novel markers to characterise the mutation's origin and localise any modifying factor. Linkage disequilibrium analysis indicates that D90A homozygotes and heterozygotes share a rare haplotype and are all descended from a single ancient founder (alpha 0.974) c.895 generations ago. Homozygotes arose subsequently only c.63 generations ago (alpha 0.878). Recombination has reduced the region shared by recessive kindreds to 97-265 kb around SOD1, excluding all neighbouring genes. We propose that a cis-acting regulatory polymorphism has arisen close to D90A-SOD1 in the recessive founder, which decreases ALS susceptibility in heterozygotes and slows disease progression.