Predictors for progression in amyotrophic lateral sclerosis associated to SOD1 mutation: insight from two population-based registries.

BACKGROUND: Uncovering distinct features and trajectories of amyotrophic lateral sclerosis (ALS) associated with SOD1 mutations (SOD1-ALS) can provide valuable insights for patient' counseling and stratification for trials, and interventions timing. Our study aims to pinpoint distinct clinical characteristics of SOD1-ALS by delving into genotype-phenotype correlations and factors that potentially impact disease progression. METHODS: This is a retrospective observational study of a SOD1-ALS cohort from two Italian registers situated in the regions of Emilia-Romagna, Piedmont and Valle d'Aosta. RESULTS: Out of 2204 genotyped ALS patients, 2.5% carried SOD1 mutations, with a M:F ratio of 0.83. SOD1-ALS patients were younger, and more frequently reported a family history of ALS and/or FTD. SOD1-ALS had a longer survival compared to patients without ALS-associated gene mutations. However, here was considerable variability in survival across distinct SOD1 mutations, with an average survival of less than a year for the L39V, G42S, G73S, D91N mutations. Among SOD1-ALS, multivariate analysis showed that, alongside established clinical prognostic factors such as advanced age at onset and high progression rate at diagnosis, mutations located in exon 2 or within highly conserved gene positions predicted worse survival. Conversely, among comorbidities, cancer history was independently associated with longer survival. INTERPRETATION: Within the context of an overall slower disease, SOD1-ALS exhibits some degree of heterogeneity linked to the considerable genetic diversity arising from the multitude of potential mutations sites and specific clinical prognostic factors, including cancer history. Revealing the factors that modulate the phenotypic heterogeneity of SOD1-ALS could prove advantageous in improving the efficacy of upcoming therapeutic approaches.

Association of Copresence of Pathogenic Variants Related to Amyotrophic Lateral Sclerosis and Prognosis.

BACKGROUND AND OBJECTIVES: Despite recent advances, it is not clear whether the various genes/genetic variants related to amyotrophic lateral sclerosis (ALS) interact in modifying patients' phenotype. The aim of this study was to determine whether the copresence of genetic variants related to ALS has interactive effects on the course of the disease. METHODS: The study population includes 1,245 patients with ALS identified through the Piemonte Register for ALS between 2007 and 2016 and not carrying superoxide dismutase type 1, TAR DNA binding protein, and fused in sarcoma pathogenic variants. Controls were 766 Italian participants age-matched, sex-matched, and geographically matched to cases. We considered Unc-13 homolog A (UNC13A) (rs12608932), calmodulin binding transcription activator 1 (CAMTA1) (rs2412208), solute carrier family 11 member 2 (SLC11A2) (rs407135), and zinc finger protein 512B (ZNF512B) (rs2275294) variants, as well as ataxin-2 (ATXN2) polyQ intermediate repeats (≥31) and chromosome 9 open reading frame 72 (C9orf72) GGGGCC intronic expansions (≥30). RESULTS: The median survival time of the whole cohort was 2.67 years (interquartile range [IQR] 1.67-5.25). In univariate analysis, only C9orf72 (2.51 years, IQR 1.74-3.82; p = 0.016), ATXN2 (1.82 years, IQR 1.08-2.33; p < 0.001), and UNC13A C/C (2.3 years, IQR 1.3-3.9; p < 0.001) significantly reduced survival. In Cox multivariable analysis, CAMTA1 also emerged to be independently related to survival (hazard ratio 1.13, 95% CI 1.001-1.30, p = 0.048). The copresence of 2 detrimental alleles/expansions was correlated with shorter survival. In particular, the median survival of patients with CAMTA1 G/G+G/T and UNC13A C/C alleles was 1.67 years (1.16-3.08) compared with 2.75 years (1.67-5.26) of the patients not carrying these variants (p < 0.001); the survival of patients with CAMTA1 G/G+G/T alleles and ATXN2 ≥31 intermediate polyQ repeats was 1.75 years (0.84-2.18) (p < 0.001); the survival of patients with ATXN2 ≥31 polyQ repeats and UNC13A C/C allele was 1.33 years (0.84-1.75) (p < 0.001); the survival of patients with C9ORF72 ≥30 and UNC13A C/C allele was 1.66 years (1.41-2.16). Each pair of detrimental alleles/expansions was associated to specific clinical phenotypes. DISCUSSION: We showed that gene variants acting as modifiers of ALS survival or phenotype can act on their own or in unison. Overall, 54% of patients carried at least 1 detrimental common variant or repeat expansion, emphasizing the clinical impact of our findings. In addition, the identification of the interactive effects of modifier genes represents a crucial clue for explaining ALS clinical heterogeneity and should be considered when designing and interpreting clinical trials results.

Integrative genetic analysis illuminates ALS heritability and identifies risk genes.

Amyotrophic lateral sclerosis (ALS) has substantial heritability, in part shared with fronto-temporal dementia (FTD). We show that ALS heritability is enriched in splicing variants and in binding sites of 6 RNA-binding proteins including TDP-43 and FUS. A transcriptome wide association study (TWAS) identified 6 loci associated with ALS, including in NUP50 encoding for the nucleopore basket protein NUP50. Independently, rare variants in NUP50 were associated with ALS risk (P = 3.71.10-03; odds ratio = 3.29; 95%CI, 1.37 to 7.87) in a cohort of 9,390 ALS/FTD patients and 4,594 controls. Cells from one patient carrying a NUP50 frameshift mutation displayed a decreased level of NUP50. Loss of NUP50 leads to death of cultured neurons, and motor defects in Drosophila and zebrafish. Thus, our study identifies alterations in splicing in neurons as critical in ALS and provides genetic evidence linking nuclear pore defects to ALS.

Exposure to electromagnetic fields does not modify neither the age of onset nor the disease progression in ALS patients.

Being exposed to electromagnetic fields has been suggested to increase the risk of developing Amyotrophic Lateral Sclerosis (ALS). Here, we investigated the effect of exposure to electromagnetic fields on ALS onset age and progression rate (ΔALSFRS-r). A large cohort of ALS patients (n = 1098) was geolocalized at the time of their diagnosis. Concomitantly, data on the distribution of power lines and repeater antennas (extremely low frequency electromagnetic fields) during the same period were retrieved. Exposure to each repeater antenna was calculated as the sum of 1/(distance from each antenna)^2. Exposure to power lines was calculated assuming each patient's address as the center of several circles of variable radius (100, 250, 500, 1000, and 2000 m). For each radius, the exposure was calculated as the length of the power lines included in the circle. Finally, patients were divided into low- and high-exposed based on the median of the exposure and compared using the Mann-Whitney test. A regression model (one for each radius) was also performed. Neither the onset age nor the ΔALSFRS-r differed among patients' low- and high-exposed to electromagnetic fields. Similarly, we could not find any significant relationship using the regression models. Our findings suggest that electromagnetic fields do not modify the ALS phenotype or progression.

Phenotype Analysis of Fused in Sarcoma Mutations in Amyotrophic Lateral Sclerosis.

Background and Objectives: Pathogenic variations in fused in sarcoma (FUS) are among the most common genetic causes of amyotrophic lateral sclerosis (ALS) worldwide. They are supposedly characterized by a homogeneous pure motor phenotype with early-onset and short disease duration. However, a few FUS-mutated cases with a very late disease onset and slow progression have been reported. To analyze genotype-phenotype correlations and identify the prognostic factors in FUS-ALS cases. Methods: We identified and cross-sectionally analyzed 22 FUS-ALS patient histories from a single-center cohort of 2,615 genetically tested patients and reviewed 289 previously published FUS-ALS cases. Survival analysis was performed by Kaplan-Meier survival curves, followed by the log-rank test and multivariate Cox analysis. Results: Survival of FUS-ALS is age-dependent: In our cohort, early-onset cases had a rapid disease progression and short survival (p = 0.000003) while the outcome of FUS-mutated patients with mid-to-late onset did not differ from non-FUS-ALS patients (p = 0.437). Meta-analysis of literature data confirmed this trend (p = 0.00003). This survival pattern is not observed in other ALS-related genes in our series. We clustered FUS-ALS patients in 3 phenotypes: (1) axial ALS, with upper cervical and dropped-head onset in mid-to-late adulthood; (2) benign ALS, usually with a late-onset and slow disease progression; and (3) juvenile ALS, often with bulbar onset and preceded by learning disability or mild mental retardation. Those phenotypes arise from different mutations. Discussion: We observed specific genotype-phenotype correlations of FUS-ALS and identified age at onset as the most critical prognostic factor. Our results demonstrated that FUS mutations underlie a specific subtype of ALS and enable a careful stratification of newly diagnosed FUS-ALS cases for clinical course and potential therapeutic windows. This will be crucial in the light of incoming gene-specific therapy.

Effects of intracellular calcium accumulation on proteins encoded by the major genes underlying amyotrophic lateral sclerosis.

The aetiology of Amyotrophic Lateral Sclerosis (ALS) is still poorly understood. The discovery of genetic forms of ALS pointed out the mechanisms underlying this pathology, but also showed how complex these mechanisms are. Excitotoxicity is strongly suspected to play a role in ALS pathogenesis. Excitotoxicity is defined as neuron damage due to excessive intake of calcium ions (Ca2+) by the cell. This study aims to find a relationship between the proteins coded by the most relevant genes associated with ALS and intracellular Ca2+ accumulation. In detail, the profile of eight proteins (TDP-43, C9orf72, p62/sequestosome-1, matrin-3, VCP, FUS, SOD1 and profilin-1), was analysed in three different cell types induced to raise their cytoplasmic amount of Ca2+. Intracellular Ca2+ accumulation causes a decrease in the levels of TDP-43, C9orf72, matrin3, VCP, FUS, SOD1 and profilin-1 and an increase in those of p62/sequestosome-1. These events are associated with the proteolytic action of two proteases, calpains and caspases, as well as with the activation of autophagy. Interestingly, Ca2+ appears to both favour and hinder autophagy. Understanding how and why calpain-mediated proteolysis and autophagy, which are physiological processes, become pathological may elucidate the mechanisms responsible for ALS and help discover new therapeutic targets.

A novel splice site FUS mutation in a familial ALS case: effects on protein expression.

Objective: To investigate the impact of a novel heterozygous FUS mutation in the acceptor splice site of intron 14 (c.1542 - 1 g > t) on protein expression in Peripheral Blood Mononuclear Cells (PBMC) from a familial ALS patient. Methods: PBMC were isolated for mRNA analysis (cDNA synthesis, sequencing and one-step RT-PCR), Western Immunoblot (WI), and Immunofluorescence (IF). Results: cDNA analysis revealed the skipping of exon 15 and a premature stop codon at c.228. RT-PCR showed reduced FUS mRNA by more than half compared to a healthy control (HC) and an ALS patient without genetic mutations (wtALS). In WI FUS band intensity in the proband was 30-50% compared to HC and wtALS. An antibody expected to detect only the wild-type protein did not reveal any reduction of FUS band intensity compared to the other antibodies. IF showed no difference among HC, wtALS, and the proband. Discussion: The reduction of FUS mRNA and protein in PBMC suggests the absence of the truncated protein, probably due to nonsense-mediated decay, leading to loss of function.

Genome sequencing analysis identifies new loci associated with Lewy body dementia and provides insights into its genetic architecture.

The genetic basis of Lewy body dementia (LBD) is not well understood. Here, we performed whole-genome sequencing in large cohorts of LBD cases and neurologically healthy controls to study the genetic architecture of this understudied form of dementia, and to generate a resource for the scientific community. Genome-wide association analysis identified five independent risk loci, whereas genome-wide gene-aggregation tests implicated mutations in the gene GBA. Genetic risk scores demonstrate that LBD shares risk profiles and pathways with Alzheimer's disease and Parkinson's disease, providing a deeper molecular understanding of the complex genetic architecture of this age-related neurodegenerative condition.