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INTRODUCTION: We evaluated differences in p-tau levels between Alzheimer's disease (AD), a condition with brain-specific changes in p-tau, and amyotrophic lateral sclerosis (ALS), a condition associated with increases in peripheral p-tau levels.

METHODS: Cerebrospinal fluid and plasma from 668 participants were analyzed using immunoassays specific for the low-molecular-weight (LMW) tau isoforms present in the brain (i.e., p-tau217Lilly, p-tau181Lilly) and those that detect both LMW- and high-molecular-weight (HMW) tau expressed in the peripheral nervous system (i.e., p-tau217AlzPath, p-tau181UGOT).

RESULTS: Increases in plasma p-tau in ALS versus controls were significantly smaller for the LMW-specific p-tau assays (15.9%–20.5%) compared with non-specific assays (92.0%–121.3%). The LMW-specific p-tau assays showed significantly larger plasma p-tau increases in AD versus ALS, discriminating AD from ALS with areas under the curve (AUCs; 0.890.93) higher than the AUCs of the non-specific assays (0.54–0.74).

DISCUSSION: LMW-specific p-tau assays could be more useful in the diagnostic workup of AD, especially in population-based communities where conditions causing peripheral neuropathy are frequent. 

Pathogenic variants in the superoxide dismutase 1 (SOD1) gene were the first identified genetic cause of amyotrophic lateral sclerosis (ALS), in 1993. This discovery enabled the development of transgenic rodent models for studying the biology of SOD1 ALS. The understanding that SOD1 ALS is driven by a toxic gain-of-function mutation has led to therapeutic strategies that aim to lower concentrations of SOD1 protein, an endeavour that has been complicated by the phenotypic heterogeneity of SOD1 ALS. The successful development of genetically targeted therapies to reduce SOD1 expression, together with a better understanding of pre-symptomatic disease and the discovery of neurofilament light protein as a susceptibility/risk biomarker that predicts phenoconversion, has ushered in a new era of trials that aim to prevent clinically manifest SOD1 ALS. The 30-year journey from gene discovery to gene therapy has not only uncovered the pathophysiology of SOD1 ALS, but has also facilitated the development of biomarkers that should aid therapy development for all forms of ALS.

Mutations in superoxide dismutase-1 (SOD1) are a common cause of amyotrophic lateral sclerosis (ALS). Inheritance is as a rule dominant, but in carriers of the most common mutation, D90A, disease can develop in both homozygous and, more rarely, in heterozygous individuals with unexplained differences in clinical presentation. There is mounting evidence that prion-like spread of SOD1 aggregation is the primary cause of the disease. Two different strains of aggregates have been found to arise in human SOD1 (hSOD1) transgenic mouse models of ALS. Strain A is formed by most mutants including hSOD1G85R and hSOD1WT, whereas hSOD1D90A transgenic mice form a distinct strain B in addition to A. To explore the effects of aggregate strain propensities when hSOD1 variants are coexpressed, we generated digenic hSOD1G85R/WT and hSOD1G85R/D90A mice. Coexpression of hSOD1WT considerably shortened the lifespan of hSOD1G85R mice to the extent expected from the neurotoxicities of the variants alone. In contrast, coexpression of hSOD1D90A had a minimal effect on survival, far smaller than expected. Moreover, time from onset to the end stage was markedly prolonged in the hSOD1G85R/D90A mice. Aggregation of hSOD1 developed concomitantly with motor neuron disease, and the aggregates contained large amounts of both coexpressed variants in both digenic models. Our findings suggest that hSOD1WT has high a capacity to coaggregate with mutants and enhance neurotoxicity. Such interactions may be restricted by differences in strain propensities, which may contribute to the primarily recessive inheritance associated with the hSOD1D90A mutation.

Introduction: The median time to diagnosis of amyotrophic lateral sclerosis (ALS) is approximately 12 months after the onset of first symptoms. This diagnostic delay is primarily due to the nonspecific nature of early symptoms and the clinical challenges in differentiating ALS from its mimics. Therefore, the discovery of reliable biomarkers for the early and accurate diagnosis of ALS represents a critical medical need.

Methods: A total of 330 participants will be recruited across six international study sites. The cohort will include (1) pre-symptomatic gene mutation carriers, (2) symptomatic individuals up to 12 months after symptom onset with either ALS, ALS mimics, or a pure motor syndrome with yet unclear assignment, and (3) healthy controls. Participants will engage in a one-year longitudinal study, consisting of an initial evaluation at baseline visit and a follow-up visit 12 months later. Assessments will include an environmental and medical history questionnaire, neurological examinations, olfactory testing, cognitive/behavioral evaluations, and the collection of biological samples (serum, plasma, urine, tear fluid, and cerebrospinal fluid). Proteomic, metabolomic, and lipidomic analyses will be performed using mass spectrometry and targeted immunoassays, with all samples processed under standardized protocols. The resulting multimodal dataset will be systematically integrated in an effort to uncover a presymptomatic and early ALS signature.

Perspective: The premodiALS study aim to identify a clinico-molecular signature characteristic of presymptomatic and early ALS. These findings may have relevance to early diagnosis and future clinical practice for ALS disease.

Amyotrophic lateral sclerosis (ALS) is a progressive motor neuron disease for which important subtypes are caused by variation in superoxide dismutase 1 (SOD1). Diagnosis based on SOD1 sequencing can not only be definitive but can also indicate specific therapies available for SOD1-associated ALS (SOD1-ALS). Unfortunately, SOD1-ALS diagnosis is limited by the fact that a substantial fraction (currently 26%) of ClinVar SOD1 missense variants are classified as “variants of uncertain significance” (VUSs). Although functional assays can provide strong evidence for clinical variant interpretation, SOD1 assay validation is challenging given the current incomplete and controversial understanding of SOD1-ALS disease mechanism. Using saturation mutagenesis and multiplexed cell-based assays, we measured the functional impact of over 2,000 SOD1 amino acid substitutions on both enzymatic function and protein abundance. The resulting “missense variant-effect maps” not only reflect prior biochemical knowledge of SOD1 but also provide sequence-structure-function insights. Importantly, our variant-abundance assay can discriminate pathogenic missense variation and provides new evidence for 41% of missense variants that had been previously reported as VUSs, offering the potential to identify additional people who would benefit from therapy approved for SOD1-ALS.

Background: Despite several studies suggesting a potential oligogenic risk model in amyotrophic lateral sclerosis (ALS), case-control statistical evidence implicating oligogenicity with disease risk or clinical outcomes is limited. Considering its direct clinical and therapeutic implications, we aim to perform a large-scale robust investigation of oligogenicity in ALS risk and in the disease clinical course. Methods: We leveraged Project MinE genome sequencing datasets (6711 cases and 2391 controls) to identify associations between oligogenicity in known ALS genes and disease risk, as well as clinical outcomes. Results: In both the discovery and replication cohorts, we observed that the risk imparted from carrying multiple ALS rare variants was significantly greater than the risk associated with carrying only a single rare variant, both in the presence and absence of variants in the most well-established ALS genes. However, in contrast to risk, the relationships between oligogenicity and ALS clinical outcomes, such as age of onset and survival, did not follow the same pattern. Conclusions: Our findings represent the first large-scale, case-control assessment of oligogenicity in ALS and show that oligogenic events involving known ALS risk genes are relevant for disease risk in ∼6% of ALS but not necessarily for disease onset and survival. This must be considered in genetic counselling and testing by ensuring to use comprehensive gene panels even when a pathogenic variant has already been identified. Moreover, in the age of stratified medication and gene therapy, it supports the need for a complete genetic profile for the correct choice of therapy in all ALS patients.

Background: Some 234 mutations in the small SOD1 gene have been reported to cause amyotrophic lateral sclerosis. However, the pathogenic mechanisms, particularly of those mutations affecting polypeptide length, are contested. It is presently unknown whether all reported nonsense mutations in SOD1 are causative for ALS. The emergence of promising new anti-SOD1 drugs has made it imperative to gain further insight into clinical–genetic aspects of ALS for deciding which patients to treat in clinical practice and include in drug trials.

Objective: This study is aimed at comprehensively analyzing the clinical phenotypes associated with ALS-causing SOD1 mutations that alter the polypeptide length. The specific focus is on the age at which symptoms manifest and the survival duration.

Methods: Data were collected from web databases, published reports, conference presentations, and personal communications up to November 2023. The clinical endpoints, including age at symptom onset and age at death, were subjected to survival analysis. Comparative analyses were performed between frameshift and nonframeshift variants.

Results: A cohort of 146 ALS patients harboring 38 different nonmissense SOD1 variants was analyzed. The mean age of disease onset was 46.9 years, with a mean survival duration of 49 months. Significant heterogeneity was observed in clinical outcomes, with earlier disease onset and reduced survival associated with specific mutations. Notably, frameshift mutations proximal to the N-terminus showed a higher risk of early ALS onset compared to more distal mutations.

Conclusions: The clinical phenotypes of ALS patients with nonmissense SOD1 mutations are highly variable and dependent on the specific mutation. These findings underscore the necessity of including diverse SOD1 mutation carriers in therapeutic trials and suggest that both loss-of-function and gain-of-function mechanisms may contribute to ALS pathology.

BACKGROUND AND OBJECTIVES: The presymptomatic stage of amyotrophic lateral sclerosis (ALS) is typically assumed to be clinically silent. Our previous work, however, has revealed evidence of a prodromal stage, termed mild motor impairment (MMI). In this study, we propose operational criteria for MMI, describe its frequency in a genetically diverse cohort, and examine the association between MMI and time to ALS phenoconversion.

METHODS: Pre-Symptomatic Familial ALS (Pre-fALS) study, initiated in 2007, is a longitudinal natural history and biomarker study of unaffected carriers of any ALS-associated pathogenic variant. Proposed research criteria for MMI were developed based on clinical review of case histories of ALS phenoconverters in the Pre-fALS study. These criteria were then systematically applied to the remaining Pre-fALS cohort. Among phenoconverters and presymptomatic carriers, cumulative probabilities of phenoconversion were estimated for those with and without MMI at baseline. Cox proportional hazard models evaluated associations between risk factors (MMI, age, genotype) and time from baseline to ALS phenoconversion.

RESULTS: The study cohort includes 49 controls (mean age 38.9, 61% female), 153 presymptomatic carriers (mean age 43.1, 61% female), and 31 ALS phenoconverters (mean age 54.4, 58% female). Seven criteria for MMI are proposed, each reflecting a different pattern of upper/lower motor neuron signs, without corresponding weakness, in 1 or more of 4 topographic regions. MMI, defined as meeting ≥1 of these criteria, was observed at 1 or more study visits in 17 of 31 phenoconverters (55%) before clinically manifest ALS, 66 of 153 presymptomatic carriers (43%) who had not yet phenoconverted, and 7 of 49 controls (14%). Among all mutation carriers, the 25th percentile (95% CI) of time to phenoconversion was, respectively, 3.7 (1.6-4.7) and 14.1 (8.9-∞) years for those with and without MMI at baseline, with a hazard ratio of 5.1 (95% CI 2.2-12.2, p < 0.0001). Moreover, the hazard rate of phenoconversion was 1.7 times higher for every 10-year increase in age and varied by genotype.

DISCUSSION: MMI is a recognizable syndrome. Although nonspecific, it identifies presymptomatic carriers at elevated risk of ALS phenoconversion. Combining MMI with emerging biomarkers of underlying pathology may help differentiate those who are prodromal from those who are not prodromal for ALS. Characterization and study of MMI, including replication in other studies, may empower early therapeutic intervention and ALS prevention efforts.

Gene silencing therapy is an effective treatment for amyotrophic lateral sclerosis (ALS) patients carrying mutations in the superoxide dismutase-1 (SOD1) gene aiming to reduce noxious forms of SOD1 in the central nervous system (CNS). The normal steady-state level of SOD1 protein in human CNS is therefore of interest but is contested. In this work we have analyzed SOD1 protein content, total protein content, and SOD1 enzymatic activity in six areas of the CNS as well as in four peripheral tissues from sporadic and familial ALS patients and non-ALS controls. Our results show that SOD1 in the human CNS constitutes around 100 μg/g wet weight corresponding to about 0.16% of the total protein in the studied areas. Of the peripheral tissues analyzed, kidney and erythrocytes contain roughly equal amounts, liver higher, and skeletal muscle lower levels of SOD1 compared to the CNS. This data shows SOD1 protein levels around 10 times lower compared to previously published figures. However, SOD1 can still be considered an abundant protein considering that > 12 000 proteins are expressed in human cells. There was no difference in SOD1 protein content between sporadic or familial ALS patients and control individuals. The level and activity of SOD1 are not deviating in the areas of the CNS that are most vulnerable to ALS. Instead, insufficient control of SOD1 structure and aggregation could be important factors behind the vulnerability of motor areas to SOD1 proteotoxicity. (Figure presented.).

When a parent is diagnosed with a progressive, fatal neurodegenerative disease, such as amyotrophic lateral sclerosis (ALS), it can have major effects on the family’s health. Parenthood itself may also be affected, potentially fueling an urgent need for support from healthcare. Research focusing on this group of parents is nevertheless limited. The aim of this study was to illuminate the meaning of parenthood when a parent has ALS, from the perspective of ill parents and co-parents. An interpretive qualitative study was conducted, using data gathered from interviewing 26 parents (13 ill parents and 13 co-parents) with children living at home in Sweden. Applying a phenomenological hermeneutical analysis, structural analyses depicted the burdensome, complex impact that ALS can have on parenthood, redefining its meaning while forcing parents to face the difficult challenges it brings. The interpreted whole revealed how navigating this transformed parenthood meant a profound struggle, as the parents strived to balance their own emotional pain from grief and worry with remaining stable and supportive for their children. To promote the health of families affected by ALS, more proactive, tailored support is needed within ALS nursing, along with early integration of a palliative approach and attention to the parental perspective.