Amyotrophic lateral sclerosis (ALS) is a fatal degenerative motor neuron disorder. Ten percent of cases are inherited; most involve unidentified genes. We report here 13 mutations in the fused in sarcoma/translated in liposarcoma (FUS/TLS) gene on chromosome 16 that were specific for familial ALS. The FUS/TLS protein binds to RNA, functions in diverse processes, and is normally located predominantly in the nucleus. In contrast, the mutant forms of FUS/TLS accumulated in the cytoplasm of neurons, a pathology that is similar to that of the gene TAR DNA-binding protein 43 (TDP43), whose mutations also cause ALS. Neuronal cytoplasmic protein aggregation and defective RNA metabolism thus appear to be common pathogenic mechanisms involved in ALS and possibly in other neurodegenerative disorders.

Spinocerebellar ataxia type 1 (SCA1) is an autosomal dominant disorder characterized by neurodegeneration of the cerebellum, spinal cord and brainstem. A 1.2-Megabase stretch of DNA from the short arm of chromosome 6 containing the SCA1 locus was isolated in a yeast artificial chromosome contig and subcloned into cosmids. A highly polymorphic CAG repeat was identified in this region and was found to be unstable and expanded in individuals with SCA1. There is a direct correlation between the size of the (CAG)n repeat expansion and the age-of-onset of SCA1, with larger alleles occurring in juvenile cases. We also show that the repeat is present in a 10 kilobase mRNA transcript. SCA1 is therefore the fifth genetic disorder to display a mutational mechanism involving an unstable trinucleotide repeat.

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.

Amyotrophic lateral sclerosis 2 (ALS2) is an autosomal recessive form of juvenile ALS and has been mapped to human chromosome 2q33. Here we report the identification of two independent deletion mutations linked to ALS2 in the coding exons of the new gene ALS2. These deletion mutations result in frameshifts that generate premature stop codons. ALS2 is expressed in various tissues and cells, including neurons throughout the brain and spinal cord, and encodes a protein containing multiple domains that have homology to RanGEF as well as RhoGEF. Deletion mutations are predicted to cause a loss of protein function, providing strong evidence that ALS2 is the causative gene underlying this form of ALS.

Spinocerebellar ataxia type 1 (SCA1) is a neurodegenerative disorder caused by expansion of a CAG trinucleotide repeat. In this study, we describe the identification and characterization of the gene harbouring this repeat. The SCA1 transcript is 10,660 bases and is transcribed from both the wild type and SCA1 alleles. The CAG repeat, coding for a polyglutamine tract, lies within the coding region. The gene spans 450 kb of genomic DNA and is organized in nine exons. The first seven fall in the 5' untranslated region and the last two contain the coding region, and a 7,277 basepairs 3' untranslated region. The first four non-coding exons undergo alternative splicing in several tissues. These features suggest that the transcriptional and translational regulation of ataxin-1, the SCA1 encoded protein, may be complex.

Objective: Mutations in the FUS gene on chromosome 16 have been recently discovered as a cause of familial amyotrophic lateral sclerosis (FALS). This study determined the frequency and identities of FUS gene mutations in a cohort of Italian patients with FALS. Methods:We screened all 15 coding exons of FUS for mutations in 94 Italian patients with FALS. Results:We identified 4 distinct missense mutations in 5 patients; 2 were novel. The mutations were not present in 376 healthy Italian controls and thus are likely to be pathogenic. Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease of adult life characterized by a selective loss of upper motor neurons (UMN) and lower motor neurons (LMN). The cause of the disease is largely unknown. Approximately 10% of all ALS cases are familial (FALS), of which ϳ20% are caused by mutations in the SOD1 gene. Conclusions:1 Variants in TARDBP, which encodes the DNA/RNA binding protein TDP-43, account for an additional ϳ5% of cases. 2-4Pathogenic mutations in 5 other genes (ALS2, SETX, VAPB, DNCT1, and ANG) have also been associated with atypical ALS phenotypes in isolated families. 5,6 Recently, mutations in the FUS gene, which also encodes a DNA/RNA binding protein, have been identified in ϳ5% of patients with FALS who tested negative for SOD1 and TARDBP mutations. 7,8 The similarities between TARDBP and FUS suggest that alterations in RNA processing may play an important role in ALS pathogenesis. The FUS gene was initially isolated analyzing chromosomal translocations in myxoid liposarcoma 9 and subsequently found in a variety of cancer-associated fusion genes. The protein plays a role in transcription, splicing, 10 and shuttling of RNA from the nucleus to the cytoplasm.11 FUS also acts as a transcriptional regulatory sensor of DNA damage signals and thus is required in maintaining the integrity of the genome.12 FUS is diffusely expressed in the CNS where it regulates the morphology of hippocampal dendritic spines and stabilizes the structure of the synapse. 13 To further define the frequency and spectrum of FUS mutations, we have screened a cohort of Italian patients with FALS.

Amyotrophic lateral sclerosis is a degenerative disorder of motor neurons that typically develops in the 6th decade and is uniformly fatal, usually within 5 years. To identify genetic variants associated with susceptibility and phenotypes in sporadic ALS, we performed a genome-wide SNP analysis in sporadic ALS cases and controls. A total of 288,357 SNPs were screened in a set of 1,821 sporadic ALS cases and 2,258 controls from the U.S. and Europe. Survival analysis was performed using 1,014 deceased sporadic cases. Top results for susceptibility were further screened in an independent sample set of 538 ALS cases and 556 controls. SNP rs1541160 within the KIFAP3 gene (encoding a kinesin-associated protein) yielded a genomewide significant result (P ‫؍‬ 1.84 ؋ 10 ؊8 ) that withstood Bonferroni correction for association with survival. Homozygosity for the favorable allele (CC) conferred a 14.0 months survival advantage. Sequence, genotypic and functional analyses revealed that there is linkage disequilibrium between rs1541160 and SNP rs522444 within the KIFAP3 promoter and that the favorable alleles of rs1541160 and rs522444 correlate with reduced KIFAP3 expression. No SNPs were associated with risk of sporadic ALS, site of onset, or age of onset. We have identified a variant within the KIFAP3 gene that is associated with decreased KIFAP3 expression and increased survival in sporadic ALS. These findings support the view that genetic factors modify phenotypes in this disease and that cellular motor proteins are determinants of motor neuron viability.genome-wide association study ͉ single nucleotide polymorphism A myotrophic lateral sclerosis (ALS) is an age-dependent, degenerative disorder of motor neurons (1) that typically develops in the 6th decade and is uniformly fatal, usually within 5 years (2). Approximately 10% of ALS cases are dominantly inherited (3); 20% of these are caused by mutations in the gene encoding copper/zinc superoxide dismutase 1 (SOD1) (4); mutations in the TARDBP gene (5, 6) account for Ϸ5% of cases. Rare familial cases arise from mutations in genes encoding the vesicle-associated membrane associated protein B (7), alsin (a RAB5-guanine nucleotide exchange factor) (8, 9), senataxin (10) or dynactin (11). Recently, we reported that Ϸ5% of familial ALS cases are due to mutations in the FUS/TLS gene (12, 13) whose product binds DNA and RNA, as does TARDBP. The cause of sporadic ALS is thought to be multifactorial, with environmental, infectious and genetic etiologies. Reported associations with variants in diverse genes (14-25) have proven difficult to replicate. Advances in the technology for large-scale genotyping of single nucleotide polymorphisms (SNPs) have facilitated unbiased, genome-wide association studies. Examples include the identification of IL2RA and IL7RA variants as risk factors for multiple sclerosis (26-28) and the recent reports of 6 new gene regions associated with type 2 diabetes (29)(30)(31)(32)(33)(34)(35). To test the hypothesis that commonly occurring genetic

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