Phenotypic heterogeneity in a SOD1 G93D Italian ALS family: an example of human model to study a complex disease

A Neglected Gene: The Role of the ANG Gene in the Pathogenesis of Amyotrophic Lateral Sclerosis

Amyotrophic lateral sclerosis (ALS) is a rapidly progressive neurodegenerative disease with a poor prognosis. To date, more than 40 ALS-related genes have been identified. However, there is still a lack of targeted therapeutic drugs for the treatment of ALS, especially for patients with acute onset and severe disease. A series of studies reported missense heterozygous mutations with loss of function in the coding region of the ANG gene in ALS patients. ANG deficiency is related to the pathogenesis of ALS, but the underlying mechanism has not been determined. This article aimed to synthesize and consolidate the knowledge of the pathological mechanism of ALS induced by ANG mutation and provide a theoretical basis for ALS diagnosis and targeted therapy. This article further delves into the mechanisms underlying the current understanding of the structure and function of the ANG gene, the association between ANG and ALS, and its pathogenesis. Mutations in ANG may lead to the development of ALS through the loss of neuroprotective function, induction of oxidative stress, or inhibition of rRNA synthesis. ANG mutations and genetic and environmental factors may cause disease heterogeneity and more severe disease than in ALS patients with the wild-type gene. Exploring this mechanism is expected to provide a new approach for ALS treatment through increasing ANG expression or angiogenin activity. However, the related study is still in its infancy; therefore, this article also highlights the need for further exploration of the application of ANG gene mutations in clinical trials and animal experiments is needed to achieve improved early diagnosis and treatment of ALS.

Clinical and molecular features of patients with amyotrophic lateral sclerosis and SOD1 mutations: a monocentric study

Introduction

SOD1 was the first gene associated with both familial and sporadic forms of amyotrophic lateral sclerosis (ALS) and is the second most mutated gene in Caucasian ALS patients. Given their high clinical and molecular heterogeneity, a detailed characterization of SOD1-ALS patients could improve knowledge about the natural history of this disease. Here, the authors aimed to provide a clinical and molecular description of a monocentric cohort of SOD1-ALS patients.

Methods

Amyotrophic lateral sclerosis (ALS) patients referring to the neurology unit of our center between 2008 and 2021 were clinically assessed and underwent molecular testing for SOD1. Segregation studies in available family members and in silico analysis were performed to sustain the pathogenicity of the identified SOD1 variants.

Results

Among the 576 patients in our cohort, we identified 19 individuals harboring a mutation in SOD1 (3.3%), including 15 (78.9%) with a familial and four (21.1%) with a sporadic form. The spinal onset of the disease was observed in all patients, and survival was extremely variable, ranging from 8 months to over 30 years. Twelve different SOD1 missense variants were identified in our cohort, including one novel mutation (p.Pro67Leu).

Discussion

In the present series, we provided the first description of an Italian monocentric cohort of SOD1-ALS patients, and we expanded the repertoire of SOD1 mutations. Our cohort presents several remarkable features, including variable expressivity in the same family, atypical presentation (ataxia, cognitive impairment, and other extra-motor symptoms), and different modes of inheritance of a given mutation in the same family. Given the recent authorization of SOD1-directed antisense oligonucleotide for use in SOD1-ALS patients, we recommend prompt screening for SOD1 mutations in novel ALS patients with familiar or sporadic presentations.

Gene Therapy in Amyotrophic Lateral Sclerosis

Since the discovery of Cu/Zn superoxide dismutase (SOD1) gene mutation, in 1993, as the first genetic abnormality in amyotrophic lateral sclerosis (ALS), over 50 genes have been identified as either cause or modifier in ALS and ALS/frontotemporal dementia (FTD) spectrum disease. Mutations in C9orf72, SOD1, TAR DNA binding protein 43 (TARDBP), and fused in sarcoma (FUS) genes are the four most common ones. During the last three decades, tremendous effort has been made worldwide to reveal biological pathways underlying the pathogenesis of these gene mutations in ALS/FTD. Accordingly, targeting etiologic genes (i.e., gene therapies) to suppress their toxic effects have been investigated widely. It includes four major strategies: (i) removal or inhibition of abnormal transcribed RNA using microRNA or antisense oligonucleotides (ASOs), (ii) degradation of abnormal mRNA using RNA interference (RNAi), (iii) decrease or inhibition of mutant proteins (e.g., using antibodies against misfolded proteins), and (iv) DNA genome editing with methods such as clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein (CRISPR/Cas). The promising results of these studies have led to the application of some of these strategies into ALS clinical trials, especially for C9orf72 and SOD1. In this paper, we will overview advances in gene therapy in ALS/FTD, focusing on C9orf72, SOD1, TARDBP, and FUS genes.

Boosting the peripheral immune response in the skeletal muscles improved motor function in ALS transgenic mice

Monocyte chemoattractant protein-1 (MCP1) is one of the most powerful pro-inflammatory chemokines. However, its signalling is pivotal in driving injured axon and muscle regeneration.

Focus on the heterogeneity of amyotrophic lateral sclerosis

The clinical manifestations of amyotrophic lateral sclerosis (ALS) are variable in terms of age at disease onset, site of onset, progression of symptoms, motor neuron involvement, and the occurrence of cognitive and behavioral changes. Genetic background is a key determinant of the ALS phenotype. The mortality of the disease also varies with the ancestral origin of the affected population and environmental factors are likely to be associated with ALS at least within some cohorts. Disease heterogeneity is likely underpinned by the presence of different pathogenic mechanisms. A variety of ALS animal models can be informative about the heterogeneity of the neuropathological or genetic aspects of the disease and can support the development of new therapeutic intervention. Evolving biomarkers can contribute to the identification of differing genotypes and phenotypes, and can be used to explore whether genotypic and phenotypic differences in animal models might help to provide a better definition of the heterogeneity of ALS in humans. These include neurofilaments, peripheral blood mononuclear cells, extracellular vesicles, microRNA and imaging findings. These biomarkers might predict not only the development of the disease, but also the variability in progression, although robust validation is required. A promising area of progress in modeling the heterogeneity of human ALS is represented by the use of human induced pluripotent stem cell (iPSCs)-derived motor neurons. Although the translational value of iPSCs remains unclear, this model is attractive in the perspective of replicating the heterogeneity of sporadic ALS as a first step toward a personalized medicine strategy.

A novel D90_K91insN mutation in exon 4 of the SOD1 gene caused familial amyotrophic lateral sclerosis in a Chinese pedigree

We reported a novel heterozygous duplication mutation (c.272_274dupACA, D90_K91insN) in exon 4 of the SOD1 gene in a Chinese pedigree. This pedigree demonstrates an autosomal dominant pattern of inheritance, with potentially reduced penetrance. The clinical phenotype was rather uniform with a distal lower extremity onset, predominant involvement of lower motor neurons (LMNs), and a relatively short survival time (mean 2.6 years) compared with other mutations in the loop V structure of SOD1. We also detected that the average SOD1 activity in D90_K91insN mutation carriers is 68.5% of wild-type controls. In conclusion, we identified the first non-frameshift duplication mutation in loop V of the human SOD1 in the Chinese population, suggesting the importance of the loop V structure in the pathogenicity of FALS.

Increase in DNA methylation in patients with amyotrophic lateral sclerosis carriers of not fully penetrant SOD1 mutations

OBJECTIVE

More than 180 different superoxide dismutase 1 (SOD1) mutations have been described to date in amyotrophic lateral sclerosis (ALS) patients, including not completely penetrant ones leading to phenotypic heterogeneity among carriers. We collected DNA samples from five ALS families with not fully penetrant SOD1 mutations (p.Asn65Ser, p.Gly72Ser, p.Gly93Asp, and p.Gly130_Glu133del) searching for epigenetic differences among ALS patients, asymptomatic/paucisymptomatic carriers and non-carrier family members.

METHODS

Global DNA methylation levels (5-methylcytosine levels) were determined in blood DNA samples with an enzyme-linked immunosorbent assay (ELISA), and the methylation analysis of SOD1, FUS, TARDBP and C9orf72 genes was performed using Methylation-Sensitive High-Resolution Melting (MS-HRM) technique.

RESULTS

Global DNA methylation levels were significantly higher in blood DNA of ALS patients than in asymptomatic/paucisymptomatic carriers or family members non-carriers of SOD1 mutations, and a positive correlation between global DNA methylation levels and disease duration (months) was observed. SOD1, FUS, TARDBP and C9orf72 gene promoters were demethylated in all subjects.

CONCLUSIONS

The present study suggests that global changes in DNA methylation might contribute to the ALS phenotype in carriers of not fully penetrant SOD1 mutations, thus reinforcing the role of epigenetic factors in modulating the phenotypic expression of the disease.

The tyrosine kinase receptor Tyro3 enhances lifespan and neuropeptide Y (Npy) neuron survival in the mouse anorexia (anx) mutation

Severe appetite and weight loss define the eating disorder anorexia nervosa, and can also accompany the progression of some neurodegenerative disorders such as amyotrophic lateral sclerosis (ALS). Although acute loss of hypothalamic neurons that produce appetite-stimulating neuropeptide Y (Npy) and agouti-related peptide (Agrp) in adult mice or in mice homozygous for the anorexia (anx) mutation causes aphagia, our understanding of the factors that help maintain appetite regulatory circuitry is limited. Here we identify a mutation (C19T) that converts an arginine to a tryptophan (R7W) in the TYRO3 protein tyrosine kinase 3 (Tyro3) gene, which resides within the anx critical interval, as contributing to the severity of anx phenotypes. Our observation that, like Tyro3-/- mice, anx/anx mice exhibit abnormal secondary platelet aggregation suggested that the C19T Tyro3 variant might have functional consequences. Tyro3 is expressed in the hypothalamus and other brain regions affected by the anx mutation, and its mRNA localization appeared abnormal in anx/anx brains by postnatal day 19 (P19). The presence of wild-type Tyro3 transgenes, but not an R7W-Tyro3 transgene, doubled the weight and lifespans of anx/anx mice and near-normal numbers of hypothalamic Npy-expressing neurons were present in Tyro3-transgenic anx/anx mice at P19. Although no differences in R7W-Tyro3 signal sequence function or protein localization were discernible in vitro, distribution of R7W-Tyro3 protein differed from that of Tyro3 protein in the cerebellum of transgenic wild-type mice. Thus, R7W-Tyro3 protein localization deficits are only detectable in vivo Further analyses revealed that the C19T Tyro3 mutation is present in a few other mouse strains, and hence is not the causative anx mutation, but rather an anx modifier. Our work shows that Tyro3 has prosurvival roles in the appetite regulatory circuitry and could also provide useful insights towards the development of interventions targeting detrimental weight loss.

Locomotor analysis identifies early compensatory changes during disease progression and subgroup classification in a mouse model of amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis is a motoneuron degenerative disease that is challenging to diagnose and presents with considerable variability in survival. Early identification and enhanced understanding of symptomatic patterns could aid in diagnosis and provide an avenue for monitoring disease progression. Use of the mSOD1G93A mouse model provides control of the confounding environmental factors and genetic heterogeneity seen in amyotrophic lateral sclerosis patients, while investigating underlying disease-induced changes. In the present study, we performed a longitudinal behavioral assessment paradigm and identified an early hindlimb symptom, resembling the common gait abnormality foot drop, along with an accompanying forelimb compensatory mechanism in the mSOD1G93A mouse. Following these initial changes, mSOD1 mice displayed a temporary hindlimb compensatory mechanism resembling an exaggerated steppage gait. As the disease progressed, these compensatory mechanisms were not sufficient to sustain fundamental locomotor parameters and more severe deficits appeared. We next applied these initial findings to investigate the inherent variability in B6SJL mSOD1G93A survival. We identified four behavioral variables that, when combined in a cluster analysis, identified two subpopulations with different disease progression rates: a fast progression group and a slow progression group. This behavioral assessment paradigm, with its analytical approaches, provides a method for monitoring disease progression and detecting mSOD1 subgroups with different disease severities. This affords researchers an opportunity to search for genetic modifiers or other factors that likely enhance or slow disease progression. Such factors are possible therapeutic targets with the potential to slow disease progression and provide insight into the underlying pathology and disease mechanisms.

Serum metal evaluation in a small cohort of Amyotrophic Lateral Sclerosis patients reveals high levels of thiophylic species

Amyotrophic Lateral Sclerosis (ALS) has often been associated with improper/altered metal metabolism. Analysis of thiophylic metals in serum from a small and geographically restricted cohort of ALS patients indicates contents of Pb and Ni much higher in patients than in controls (Ni, 5-fold; Pb, 2-fold). Se levels are also higher in the patients’ group, which has instead lower As levels than controls. Thiophylic metals may impair biogenesis of FeS clusters or substitute for iron, even in folded proteins; Se may non-functionally replace S. Thus, improper assembly/ function of FeS proteins could represent another possible issue to be considered in ALS pathogenesis.

The phenotypic variability of amyotrophic lateral sclerosis

Classic textbook neurology teaches that amyotrophic lateral sclerosis (ALS) is a degenerative disease that selectively affects upper and lower motor neurons and is fatal 3-5 years after onset--a description which suggests that the clinical presentation of ALS is very homogenous. However, clinical and postmortem observations, as well as genetic studies, demonstrate that there is considerable variability in the phenotypic expression of ALS. Here, we review the phenotypic variability of ALS and how it is reflected in familial and sporadic ALS, in the degree of upper and lower motor neuron involvement, in motor and extramotor involvement, and in the spectrum of ALS and frontotemporal dementia. Furthermore, we discuss some unusual clinical characteristics regarding presentation, age at onset and disease progression. Finally, we address the importance of this variability for understanding the pathogenesis of ALS and for the development of therapeutic strategies.

Amyotrophic lateral sclerosis in pregnancy is associated with a vascular endothelial growth factor promoter genotype

BACKGROUND AND PURPOSE

The occurrence of amyotrophic lateral sclerosis (ALS) during pregnancy is uncommon and the effect of one on the other is not well described.

METHODS

The clinical and genetic features of five cases of ALS are reported with an onset during pregnancy or within 1 month from delivery. Charts from 239 women with a diagnosis of ALS attending the neuromuscular clinics at the Neuromuscular Omnicentre (NEMO) and at IRCCS Policlinico San Donato from 2008 to 2011 were reviewed.

RESULTS

Of these, 12.8% of the women in child-bearing age had a diagnosis of ALS during pregnancy or immediately after delivery. Genetic screening of the major causative genes revealed two mutations in superoxide dismutase 1 (SOD1) gene; the analysis of vascular endothelial growth factor (VEGF) promoter variation showed a segregation of the haplotype CA/AG (-2578C/A; -1190A/G) in patients developing ALS related to pregnancy. No effects on foetal development or neonatal course were observed.

CONCLUSIONS

Pregnancy may unmask ALS but whether this is coincidental is unclear. Hormonal and inflammatory modifications might trigger ALS in subjects with increased susceptibility to oxidative stress related to the toxic function of SOD1 or in subjects with a reduction of neuroprotective molecules such as VEGF.

EPHA4 is a disease modifier of amyotrophic lateral sclerosis in animal models and in humans

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease affecting motor neurons. Disease onset and progression are variable, with survival ranging from months to decades. Factors underlying this variability may represent targets for therapeutic intervention. Here, we have screened a zebrafish model of ALS and identified Epha4, a receptor in the ephrin axonal repellent system, as a modifier of the disease phenotype in fish, rodents and humans. Genetic as well as pharmacological inhibition of Epha4 signaling rescues the mutant SOD1 phenotype in zebrafish and increases survival in mouse and rat models of ALS. Motor neurons that are most vulnerable to degeneration in ALS express higher levels of Epha4, and neuromuscular re-innervation by axotomized motor neurons is inhibited by the presence of Epha4. In humans with ALS, EPHA4 expression inversely correlates with disease onset and survival, and loss-of-function mutations in EPHA4 are associated with long survival. Furthermore, we found that knockdown of Epha4 also rescues the axonopathy induced by expression of mutant TAR DNA-binding protein 43 (TDP-43), another protein causing familial ALS, and the axonopathy induced by knockdown of survival of motor neuron 1, a model for spinomuscular atrophy. This suggests that Epha4 generically modulates the vulnerability of (motor) neurons to axonal degeneration and may represent a new target for therapeutic intervention.

Identification of a novel missense mutation in angiogenin in a Chinese amyotrophic lateral sclerosis cohort

Abstract Angiogenin (ANG) gene mutations have been identified in both familial and sporadic amyotrophic lateral sclerosis (ALS) patients from multiple European and North American populations. However, no ANG mutation has yet been reported in Asian ALS populations. Here, we screened for ANG mutations in a Chinese ALS cohort. The entire coding region of the ANG gene was sequenced in 10 familial ALS pedigrees, 202 sporadic ALS patients, and 151 healthy controls. All patients were negative for SOD1, FUS, and TARDBP mutations. We identified a novel missense mutation, c.379G > A (p.V103I), in one sporadic ALS patient, but not in the controls. No mutations were found in the familial ALS patients. A novel missense variant, c.323A > G (p.H84R), was detected in one healthy individual. We identified the presence of the known single nucleotide polymorphism, rs11701 (T/G), in both ALS cases and controls. However, no significant association of the G allele with ALS susceptibility was demonstrated. In conclusion, ANG mutations accounted for 0.5% of our SOD1-, FUS-, TARDBP- mutation-negative ALS cohort. Our findings highlight that the genetic background of ALS differs between different populations, and suggest that ANG mutation may be involved in the aetiology of ALS in the Han Chinese population.

SOD1 G93D sporadic amyotrophic lateral sclerosis (SALS) patient with rapid progression and concomitant novel ANG variant

SOD1 G93D mutation has been described in amyotrophic lateral sclerosis (ALS) patients with slowly progressive disease. We describe an Italian patient affected by sporadic ALS with the SOD1 G93D mutation that disclosed an unusual rapid progression with death occurring after 30 months from the symptom onset. Considering the atypical clinical course further genes associated with ALS or known to be causative were studied including ANG, PGRN, TARDBP, FUS, VCP, CHRNA3, CHRNA4, and CHRNB4. A novel heterozygous ANG missense variant (c.433 C>T, p.R145C) was identified which is neither reported in controls nor in 1000 genomes and single nucleotide polymorphism (SNP) databases. This report confirms that clinical course of SOD1-related ALS may be modulated by other causative or associated genes, including ANG and suggests that extensive screening of ALS-associated genes in patients with an already identified mutation may be helpful for better knowledge of genetic architecture of ALS.