Genetics of amyotrophic lateral sclerosis: A review

Association between DPP6 gene rs10260404 polymorphism and increased risk of sporadic amyotrophic lateral sclerosis (sALS): a meta-analysis

BACKGROUND

Sporadic amyotrophic lateral sclerosis (sALS) is a severe neurodegenerative disease characterized by continuous diminution of motor neurons in the brain and spinal cord. Earlier studies indicated that the DPP6 gene variant has a role in the development of sALS. This meta-analysis was designed to uncover the role of rs10260404 polymorphism of the DPP6 gene and its association with sALS.

METHODS

All case-control articles published prior to October 2022 on the association between DPP6 (rs10260404) polymorphism and sALS risk were systematically extracted from different databases which include PubMed, PubMed Central, and Google Scholar. Overall odds ratios (ORs) and "95% confidence intervals (CIs)" were summarized for various genetic models. Subgroup and heterogeneity assessments were performed. Egger's and "Begg's tests were applied to evaluate publication bias. Trial sequential analysis (TSA) and false-positive report probability (FPRP) were performed.

RESULTS

Nine case-control studies containing 4202 sALS cases and 4444 healthy controls were included in the meta-analysis. A significant association of the DPP6 (rs10260404) variant with an increased sALS risk in overall pooled subjects under allelic model [C allele vs. T allele, OR = 1.149, 95% CI (1.010-1.307), p-value = 0.035], dominant model [CC + CT vs. TT, OR = 1.165, 95% CI (1.067-1.273), p-value = 0.001], and homozygote comparison [CC vs. TT, OR = 1.421, 95% CI (1.003-2.011), p-value = 0.048] were observed. Moreover, in subgroup analysis by nationality, remarkable associations were detected in Dutch, Irish, American, and Swedish under allelic, dominant, and homozygote models. Additionally, stratification analysis by ethnicity exhibited an association with sALS risk among Caucasians and Americans under different genetic models. Interestingly, none of the models found any significant association with Asians.

CONCLUSION

The present meta-analysis indicates that DPP6 (rs10260404) polymorphism could be a candidate risk factor for sALS predisposition.

Current therapy in amyotrophic lateral sclerosis (ALS): A review on past and future therapeutic strategies

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease that affects the first and second motoneurons (MNs), associated with muscle weakness, paralysis and finally death. The exact etiology of the disease still remains unclear. Currently, efforts to develop novel ALS treatments which target specific pathomechanisms are being studied. The mechanisms of ALS pathogenesis involve multiple factors, such as protein aggregation, glutamate excitotoxicity, oxidative stress, mitochondrial dysfunction, apoptosis, inflammation etc. Unfortunately, to date, there are only two FDA-approved drugs for ALS, riluzole and edavarone, without curative treatment for ALS. Herein, we give an overview of the many pathways and review the recent discovery and preclinical characterization of neuroprotective compounds. Meanwhile, drug combination and other therapeutic approaches are also reviewed. In the last part, we analyze the reasons of clinical failure and propose perspective on the treatment of ALS in the future.

Clinical and genetic factors affecting diagnostic timeline of amyotrophic lateral sclerosis: a 15-year retrospective study

OBJECTIVES

Amyotrophic Lateral Sclerosis (ALS) diagnosis can take 10-16 months from symptom onset, leading to delays in treatment and patient counselling. We studied the impact of clinical and genetic risk factors on the diagnostic timeline of ALS.

METHODS

Baseline characteristics, family history, gene testing, onset location, time from symptom onset to diagnosis, and time from first doctor visit to suspected ALS was collected. We used multiple regression to assess the interaction of these factors on ALS diagnostic timeline. We analysed a subgroup of patients with genetic testing and compared positive or negative tests, sporadic or familial and ALS-related genes to time for diagnosis.

RESULTS

Four hundred and forty-eight patients diagnosed with ALS at the University of Massachusetts Chan Medical Center between January 2007 and December 2021 were analysed. The median time to ALS diagnosis was 12 months and remained unchanged from 2007 to 2021 (p = 0.20). Diagnosis was delayed in patients with sporadic compared with familial ALS (mean months [standard deviation], 16.5[13.5] and 11.2[8.5], p < 0.001); cognitive onset (41[21.26]) had longer time to diagnosis than bulbar (11.9[8.2]), limb (15.9[13.2]), respiratory (19.7[13.9]) and ALS with multiple onset locations (20.77[15.71], p < 0.001). One hundred and thirty-four patients had gene testing and 32 tested positive (23.8%). Gene testing (p = 0.23), a positive genetic test (p = 0.16), different ALS genes (p = 0.25) and sporadic (p = 0.92) or familial (p = 0.85) ALS testing positive for ALS genes did not influence time to diagnosis.

DISCUSSION

Time for ALS diagnosis remained unchanged from 2007 to 2021, bulbar-onset and familial ALS made for faster diagnosis.

The various forms of hereditary motor neuron disorders and their historical descriptions

Motor neuron disorders comprise a clinically and pathologically heterogeneous group of neurologic diseases characterized by progressive degeneration of motor neurons (including both sporadic and hereditary diseases), affecting the upper motor neurons, lower motor neurons, or both. Hereditary motor neuron disorders themselves represent a vast and heterogeneous group, with numerous clinical and genetic overlaps that can be a source of error. This narrative review aims at providing an overview of the main types of inherited motor neuron disorders by recounting the stages in their historical descriptions. For practical purposes, this review of the literature sets out their various clinical characteristics and updates the list of all the genes involved in the various forms of inherited motor neuron disorders, including spinal muscular atrophy, familial amyotrophic lateral sclerosis, hereditary spastic paraplegia, distal hereditary motor neuropathies/neuronopathies, Kennedy's disease, riboflavin transporter deficiencies, VCPopathy and the neurogenic scapuloperoneal syndrome.

Increased incidence of motor neuron disease in Sweden: a population-based study during 2002-2021

BACKGROUND

Motor neuron diseases (MND), with amyotrophic lateral sclerosis constituting most cases, are rare conditions of unknown etiology. There have been reports of an increase in incidence during the latter half of the twentieth century in various Western countries, including Sweden. This study provides updated data on the incidence of MND in Sweden during the last 20 years.

METHODS

Data was obtained from the Swedish National Patient Register on individuals diagnosed with MND from 2002 to 2021 and analysed in relation to group level data for the entire Swedish population. Incidence rates were calculated and presented in relation to year, age, sex, and region.

RESULTS

In the early 2000s, there was a crude incidence rate of 3.5-3.7 per 100,000 person-years, which then increased to 4.0-4.6 from 2008 onward. Age standardization to the starting year (2002) partially mitigated this increase. The incidence rate was greater among men compared to women and was highest within the age range of 70 to 84 years. There were indications of a higher incidence rate in the northernmost parts of the country, although the difference was not statistically significant.

CONCLUSIONS

The incidence rate of MND in Sweden now seems to have surpassed 4 cases per 100,000 person-years. This is higher when compared to both other European countries and previous Swedish studies. It remains to be determined if this increase reflects an actual increasing incidence of MND in Sweden or is due to other factors such as better registry coverage.

The clinical practice guideline for the management of amyotrophic lateral sclerosis in Japan-update 2023

Amyotrophic lateral sclerosis (ALS) is an adult-onset intractable motor neuron disease characterized by selective degeneration of cortical neurons in the frontotemporal lobe and motor neurons in the brainstem and spinal cord. Impairment of these neural networks causes progressive muscle atrophy and weakness that spreads throughout the body, resulting in life-threatening bulbar palsy and respiratory muscle paralysis. However, no therapeutic strategy has yet been established to halt ALS progression. Although evidence for clinical practice in ALS remains insufficient, novel research findings have steadily accumulated in recent years. To provide updated evidence-based or expert consensus recommendations for the diagnosis and management of ALS, the ALS Clinical Practice Guideline Development Committee, approved by the Japanese Society of Neurology, revised and published the Japanese clinical practice guidelines for the management of ALS in 2023. In this guideline, disease-modifying therapies that have accumulated evidence from randomized controlled trials were defined as "Clinical Questions," in which the level of evidence was determined by systematic reviews. In contrast, "Questions and Answers" were defined as issues of clinically important but insufficient evidence, according to reports of a small number of cases, observational studies, and expert opinions. Based on a literature search performed in February 2022, recommendations were reached by consensus, determined by an independent panel, reviewed by external reviewers, and submitted for public comments by Japanese Society of Neurology members before publication. In this article, we summarize the revised Japanese guidelines for ALS, highlighting the regional and cultural diversity of care processes and decision-making. The guidelines cover a broad range of essential topics such as etiology, diagnostic criteria, disease monitoring and treatments, management of symptoms, respiration, rehabilitation, nutrition, metabolism, patient instructions, and various types of care support. We believe that this summary will help improve the daily clinical practice for individuals living with ALS and their caregivers.

AAV-mediated upregulation of VDAC1 rescues the mitochondrial respiration and sirtuins expression in a SOD1 mouse model of inherited ALS

Mitochondrial dysfunction represents one of the most common molecular hallmarks of both sporadic and familial forms of amyotrophic lateral sclerosis (ALS), a neurodegenerative disorder caused by the selective degeneration and death of motor neurons. The accumulation of misfolded proteins on and within mitochondria, as observed for SOD1 G93A mutant, correlates with a drastic reduction of mitochondrial respiration and the inhibition of metabolites exchanges, including ADP/ATP and NAD+/NADH, across the Voltage-Dependent Anion-selective Channel 1 (VDAC1), the most abundant channel protein of the outer mitochondrial membrane. Here, we show that the AAV-mediated upregulation of VDAC1 in the spinal cord of transgenic mice expressing SOD1 G93A completely rescues the mitochondrial respiratory profile. This correlates with the increased activity and levels of key regulators of mitochondrial functions and maintenance, namely the respiratory chain Complex I and the sirtuins (Sirt), especially Sirt3. Furthermore, the selective increase of these mitochondrial proteins is associated with an increase in Tom20 levels, the receptor subunit of the TOM complex. Overall, our results indicate that the overexpression of VDAC1 has beneficial effects on ALS-affected tissue by stabilizing the Complex I-Sirt3 axis.

The multifaceted role of the CXC chemokines and receptors signaling axes in ALS pathophysiology

Amyotrophic lateral sclerosis (ALS) is a late-onset motor neuron disease with complex genetic basis and still no clear etiology. Multiple intertwined layers of immune system-related dysfunctions and neuroinflammatory mechanisms are emerging as substantial determinants in ALS onset and progression. In this review, we collect the increasingly arising evidence implicating four main CXC chemokines/cognate receptors signaling axes (CXCR1/2-CXCL1/2/8; CXCR3-CXCL9/10/11; CXCR4/7-CXCL12; CXCR5-CXCL13) in the pathophysiology of ALS. Findings in preclinical models implicate these signaling pathways in motor neuron toxicity and neuroprotection, while in ALS patients dysregulation of CXCLs/CXCRs has been shown at both central and peripheral levels. Immunological monitoring of CXC-ligands in ALS may allow tracking of disease progression, while pharmacological modulation of CXC-receptors provides a novel therapeutic strategy. A deeper understanding of the interplay between CXC-mediated neuroinflammation and ALS is crucial to advance research into treatments for this debilitating uncurable disorder.

Repeat expansions in AR, ATXN1, ATXN2 and HTT in Norwegian patients diagnosed with amyotrophic lateral sclerosis

Genetic repeat expansions cause neuronal degeneration in amyotrophic lateral sclerosis as well as other neurodegenerative disorders such as spinocerebellar ataxia, Huntington's disease and Kennedy's disease. Repeat expansions in the same gene can cause multiple clinical phenotypes. We aimed to characterize repeat expansions in a Norwegian amyotrophic lateral sclerosis cohort. Norwegian amyotrophic lateral sclerosis patients (n = 414) and neurologically healthy controls adjusted for age and gender (n = 713) were investigated for repeat expansions in AR, ATXN1, ATXN2 and HTT using short read exome sequencing and the ExpansionHunter software. Five amyotrophic lateral sclerosis patients (1.2%) and two controls (0.3%) carried ≥36 repeats in HTT (P = 0.032), and seven amyotrophic lateral sclerosis patients (1.7%) and three controls (0.4%) carried ≥29 repeats in ATXN2 (P = 0.038). One male diagnosed with amyotrophic lateral sclerosis carried a pathogenic repeat expansion in AR, and his diagnosis was revised to Kennedy's disease. In ATXN1, 50 amyotrophic lateral sclerosis patients (12.1%) and 96 controls (13.5%) carried ≥33 repeats (P = 0.753). None of the patients with repeat expansions in ATXN2 or HTT had signs of Huntington's disease or spinocerebellar ataxia type 2, based on a re-evaluation of medical records. The diagnosis of amyotrophic lateral sclerosis was confirmed in all patients, with the exception of one patient who had primary lateral sclerosis. Our findings indicate that repeat expansions in HTT and ATXN2 are associated with increased likelihood of developing amyotrophic lateral sclerosis. Further studies are required to investigate the potential relationship between HTT repeat expansions and amyotrophic lateral sclerosis.

Genetic and in silico analysis of Indian sporadic young onset patient with amyotrophic lateral sclerosis

Background: Amyotrophic lateral sclerosis (ALS) is an old onset devastating neurodegenerative disorder. Young-onset ALS cases especially sporadic ones who are between 25 and 45 years are rarely affected by the disease. Despite the identification of numerous candidate genes associated with ALS, the etiology of the disease remains elusive due to extreme genetic and phenotypic variability. The advent of affordable whole exome sequencing (WES) has opened new avenues for unraveling the disease's pathophysiology better. Methods and results: We aimed to determine the genetic basis of an Indian-origin, young onset sporadic ALS patient with very rapid deterioration of the disease course without any cognitive decline who was screened for mutations in major ALS candidate genes by WES. Variants detected were reconfirmed by Sanger sequencing. The clinicopathological features were investigated and two heterozygous missense variants were identified: R452W, not previously associated with ALS, present in one of the four conserved C terminal domains in ANXA11 and R208W in SIGMAR1, respectively. Both of these variants were predicted to be damaging by pathogenicity prediction tools and various in silico methods. Conclusion: Our study revealed two potentially pathogenic variants in two ALS candidate genes. The genetic makeup of ALS patients from India has been the subject of a few prior studies, but none of them examined ANXA11 and SIGMAR1 genes so far. These results establish the framework for additional research into the pathogenic processes behind these variations that result in sporadic ALS disease and further our understanding of the genetic makeup of Indian ALS patients.

Structural insights into the modulation Of SOD1 aggregation By a fungal metabolite Phialomustin-B: Therapeutic potential in ALS

Amyotrophic lateral sclerosis (ALS) is a fatal human motor neuron disease leading to muscle atrophy and paralysis. Mutations in superoxide dismutase 1 (SOD1) are associated with familial ALS (fALS). The SOD1 mutants in ALS have a toxic-gain of function by destabilizing the functional SOD1 homodimer, consequently inducing fibril-like aggregation with a cytotoxic non-native trimer intermediate. Therefore, reducing SOD1 oligomerization via chemical modulators is an optimal therapy in ALS. Here, we report the discovery of Phialomustin-B, an unsaturated secondary metabolite from the endophytic fungus Phialophora mustea, as a modulator of SOD1 aggregation. The crystal structure of the SOD1-Phialomustin complex refined to 1.90 Å resolution demonstrated for the first time that the ligand binds to the dimer interface and the lateral region near the electrostatic loop. The aggregation analyses of SOD1WT and the disease mutant SOD1A4V revealed that Phialomustin-B reduces cytotoxic trimerization. We propose that Phialomustin-B is a potent lead molecule with therapeutic potential in fALS.

Genetic overlap between ALS and other neurodegenerative or neuromuscular disorders

OBJECTIVE

In Norway, 89% of patients with Amyotrophic lateral sclerosis (ALS) lacks a genetic diagnose. ALS genes and genes that cause other neuromuscular or neurodegenerative disorders extensively overlap. This population-based study examined whether patients with ALS have a family history of neurological disorders and explored the occurrence of rare genetic variants associated with other neurodegenerative or neuromuscular disorders.

METHODS

During a two-year period, blood samples and clinical data from patients with ALS were collected from all 17 neurological departments in Norway. Our genetic analysis involved exome sequencing and bioinformatics filtering of 510 genes associated with neurodegenerative and neuromuscular disorders. The variants were interpreted using genotype-phenotype correlations and bioinformatics tools.

RESULTS

A total of 279 patients from a Norwegian population-based ALS cohort participated in this study. Thirty-one percent of the patients had first- or second-degree relatives with other neurodegenerative disorders, most commonly dementia and Parkinson's disease. The genetic analysis identified 20 possible pathogenic variants, in ATL3, AFG3L2, ATP7A, BICD2, HARS1, KIF1A, LRRK2, MSTO1, NEK1, NEFH, and SORL1, in 25 patients. NEK1 risk variants were present in 2.5% of this ALS cohort. Only four of the 25 patients reported relatives with other neurodegenerative or neuromuscular disorders.

CONCLUSION

Gene variants known to cause other neurodegenerative or neuromuscular disorders, most frequently in NEK1, were identified in 9% of the patients with ALS. Most of these patients had no family history of other neurodegenerative or neuromuscular disorders. Our findings indicated that AFG3L2, ATP7A, BICD2, KIF1A, and MSTO1 should be further explored as potential ALS-causing genes.

SOD1-Related Cerebellar Ataxia and Motor Neuron Disease: Cp Variant as Functional Modifier?

We describe a novel superoxide dismutase (SOD1) mutation-associated clinical phenotype of cerebellar ataxia and motor neuron disease with a variant in the ceruloplasmin (Cp) gene, which may have possibly contributed to a multi-factorial phenotype, supported by genetic and protein structure analyses.

An optogenetic cell therapy to restore control of target muscles in an aggressive mouse model of amyotrophic lateral sclerosis

Breakdown of neuromuscular junctions (NMJs) is an early pathological hallmark of amyotrophic lateral sclerosis (ALS) that blocks neuromuscular transmission, leading to muscle weakness, paralysis and, ultimately, premature death. Currently, no therapies exist that can prevent progressive motor neuron degeneration, muscle denervation, or paralysis in ALS. Here, we report important advances in the development of an optogenetic, neural replacement strategy that can effectively restore innervation of severely affected skeletal muscles in the aggressive SOD1G93A mouse model of ALS, thus providing an interface to selectively control the function of targeted muscles using optical stimulation. We also identify a specific approach to confer complete survival of allogeneic replacement motor neurons. Furthermore, we demonstrate that an optical stimulation training paradigm can prevent atrophy of reinnervated muscle fibers and results in a tenfold increase in optically evoked contractile force. Together, these advances pave the way for an assistive therapy that could benefit all ALS patients.

Exploring the cuproptosis-related molecular clusters in the peripheral blood of patients with amyotrophic lateral sclerosis

BACKGROUND

Amyotrophic lateral sclerosis (ALS) is a progressive and lethal neurodegenerative disease. Several studies have suggested the involvement of cuproptosis in its pathogenesis. In this research, we intend to explore the cuproptosis-related molecular clusters in ALS and develop a novel cuproptosis-related genes prediction model.

METHODS

The peripheral blood gene expression data was downloaded from the Gene Expression Omnibus (GEO) online database. Based on the GSE112681 dataset, we investigated the critical cuproptosis-related genes (CuRGs) and pathological clustering of ALS. The immune microenvironment features of the peripheral blood in ALS patients were also examined using the CIBERSORT algorithm. Cluster-specific hub genes were determined by the WGCNA. The most accurate prediction model was selected by comparing the performance of four machine learning techniques. ROC curves and two independent datasets were applied to validate the prediction accuracy. The available compounds targeting these hub genes were filtered to investigate their efficacy in treating ALS.

RESULTS

We successfully determined four critical cuproptosis-related genes and two pathological clusters with various immune profiles and biological characteristics in ALS. Functional analysis showed that genes in Cluster1 were primarily enriched in pathways closely associated with immunity. The Support Vector Machine (SVM) model exhibited the best discrimination properties with a large area under the curve (AUC = 0.862). Five hub prediction genes (BAP1, SMG1, BCLAF1, DHX15, EIF4G2) were selected to establish a nomogram model, suggesting significant risk prediction potential for ALS. The accuracy of this model in predicting ALS incidence was also demonstrated through calibration curves, nomograms, and decision curve analysis. Finally, three drugs targeting BAP1 were determined through drug-gene interactions.

CONCLUSION

This study elucidated the complex associations between cuproptosis and ALS and constructed a satisfactory predictive model to explore the pathological characteristics of different clusters in ALS patients.

IFNγ protects motor neurons from oxidative stress via enhanced global protein synthesis in FUS-associated amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis type 6 (ALS6) is a familial subtype of ALS linked to Fused in Sarcoma (FUS) gene mutation. FUS mutations lead to decreased global protein synthesis, but the mechanism that drives this has not been established. Here, we used ALS6 patient-derived induced pluripotent stem cells (hIPSCs) to study the effect of the ALS6 FUSR521H mutation on the translation machinery in motor neurons (MNs). We find, in agreement with findings of others, that protein synthesis is decreased in FUSR521H MNs. Furthermore, FUSR521H MNs are more sensitive to oxidative stress and display reduced expression of TGF-β and mTORC gene pathways when stressed. Finally, we show that IFNγ treatment reduces apoptosis of FUSR521H MNs exposed to oxidative stress and partially restores the translation rates in FUSR521H MNs. Overall, these findings suggest that a functional IFNγ response is important for FUS-mediated protein synthesis, possibly by FUS nuclear translocation in ALS6.

Preferential potentiation of AMPA-mediated currents in brainstem hypoglossal motoneurons by subchronic exposure of mice expressing the human superoxide dismutase 1 G93A gene mutation to neurotoxicant methylmercury in vivo

The exact causes of Amyotrophic lateral sclerosis (ALS), a progressive and fatal neurological disorder due to loss of upper and/or lower motoneurons, remain elusive. Gene-environment interactions are believed to be an important factor in the development of ALS. We previously showed that in vivo exposure of mice overexpressing the human superoxide dismutase 1 (hSOD1) gene mutation (hSOD1G93A; G93A), a mouse model for ALS, to environmental neurotoxicant methylmercury (MeHg) accelerated the onset of ALS-like phenotype. Here we examined the time-course of effects of MeHg on AMPA receptor (AMPAR)-mediated currents in hypoglossal motoneurons in brainstem slices prepared from G93A, hSOD1wild-type (hWT) and non-carrier WT mice following in vivo exposure to MeHg. Mice were exposed daily to 3 ppm (approximately 0.7 mg/kg/day) MeHg via drinking water beginning at postnatal day 28 (P28) and continued until P47, 64 or 84, then acute brainstem slices were prepared, and spontaneous excitatory postsynaptic currents (sEPSCs) or AMPA-evoked currents were examined using whole cell patch-clamp recording technique. Brainstem slices of untreated littermates were prepared at the same time points to serve as control. MeHg exposure had no significant effect on either sEPSCs or AMPA-evoked currents in slices from hWT or WT mice during any of those exposure time periods under our experimental conditions. MeHg also did not cause any significant effect on sEPSCs or AMPA-currents in G93A hypoglossal motoneurons at P47 and P64. However, at P84, MeHg significantly increased amplitudes of both sEPSCs and AMPA-evoked currents in hypoglossal motineurons from G93A mice (p < 0.05), but not the sEPSC frequency, suggesting a postsynaptic action on AMPARs. MeHg exposure did not cause any significant effect on GABAergic spontaneous inhibitory postsynaptic currents (sIPSCs). Therefore, MeHg exposure in vivo caused differential effects on AMPARs in hypoglossal motoneurons from mice with different genetic backgrounds. MeHg appears to preferentially stimulate the AMPAR-mediated currents in G93A hypoglossal motoneurons in an exposure time-dependent manner, which may contribute to the AMPAR-mediated motoneuron excitotoxicity, thereby facilitating development of ALS-like phenotype.

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.

Muscle Involvement in Amyotrophic Lateral Sclerosis: Understanding the Pathogenesis and Advancing Therapeutics

Amyotrophic lateral sclerosis (ALS) is a fatal condition characterized by the selective loss of motor neurons in the motor cortex, brainstem, and spinal cord. Muscle involvement, muscle atrophy, and subsequent paralysis are among the main features of this disease, which is defined as a neuromuscular disorder. ALS is a persistently progressive disease, and as motor neurons continue to degenerate, individuals with ALS experience a gradual decline in their ability to perform daily activities. Ultimately, muscle function loss may result in paralysis, presenting significant challenges in mobility, communication, and self-care. While the majority of ALS research has traditionally focused on pathogenic pathways in the central nervous system, there has been a great interest in muscle research. These studies were carried out on patients and animal models in order to better understand the molecular mechanisms involved and to develop therapies aimed at improving muscle function. This review summarizes the features of ALS and discusses the role of muscle, as well as examines recent studies in the development of treatments.

The Key Role of Astrocytes in Amyotrophic Lateral Sclerosis and Their Commitment to Glutamate Excitotoxicity

In the last two decades, there has been increasing evidence supporting non-neuronal cells as active contributors to neurodegenerative disorders. Among glial cells, astrocytes play a pivotal role in driving amyotrophic lateral sclerosis (ALS) progression, leading the scientific community to focus on the "astrocytic signature" in ALS. Here, we summarized the main pathological mechanisms characterizing astrocyte contribution to MN damage and ALS progression, such as neuroinflammation, mitochondrial dysfunction, oxidative stress, energy metabolism impairment, miRNAs and extracellular vesicles contribution, autophagy dysfunction, protein misfolding, and altered neurotrophic factor release. Since glutamate excitotoxicity is one of the most relevant ALS features, we focused on the specific contribution of ALS astrocytes in this aspect, highlighting the known or potential molecular mechanisms by which astrocytes participate in increasing the extracellular glutamate level in ALS and, conversely, undergo the toxic effect of the excessive glutamate. In this scenario, astrocytes can behave as "producers" and "targets" of the high extracellular glutamate levels, going through changes that can affect themselves and, in turn, the neuronal and non-neuronal surrounding cells, thus actively impacting the ALS course. Moreover, this review aims to point out knowledge gaps that deserve further investigation.

Endophytic fungi: a potential source for drugs against central nervous system disorders

Neuroprotection is one of the important protection methods against neuronal cells and tissue damage caused by neurodegenerative diseases such as Alzheimer's, Parkinson's, Huntington's, and multiple sclerosis. Various bioactive compounds produced by medicinal plants can potentially treat central nervous system (CNS) disorders. Apart from these resources, endophytes also produce diverse secondary metabolites capable of protecting the CNS. The bioactive compounds produced by endophytes play essential roles in enhancing the growth factors, antioxidant defence functions, diminishing neuroinflammatory, and apoptotic pathways. The efficacy of compounds produced by endophytic fungi was also evaluated by enzymes, cell lines, and in vivo models. Acetylcholine esterase (AChE) inhibition is frequently used to assess in vitro neuroprotective activity along with cytotoxicity-induced neuronal cell lines. Some of drugs, such as tacrine, donepezil, rivastigmine, galantamine, and other compounds, are generally used as reference standards. Furthermore, clinical trials are required to confirm the role of these natural compounds in neuroprotection efficacy and evaluate their safety profile. This review illustrates the production of various bioactive compounds produced by endophytic fungi and their role in preventing neurodegeneration.

The ε-Isozyme of Protein Kinase C (PKCε) Is Impaired in ALS Motor Cortex and Its Pulse Activation by Bryostatin-1 Produces Long Term Survival in Degenerating SOD1-G93A Motor Neuron-like Cells

Amyotrophic lateral sclerosis (ALS) is a rapidly progressive and ultimately fatal neurodegenerative disease, characterized by a progressive depletion of upper and lower motor neurons (MNs) in the brain and spinal cord. The aberrant regulation of several PKC-mediated signal transduction pathways in ALS has been characterized so far, describing either impaired expression or altered activity of single PKC isozymes (α, β, ζ and δ). Here, we detailed the distribution and cellular localization of the ε-isozyme of protein kinase C (PKCε) in human postmortem motor cortex specimens and reported a significant decrease in both PKCε mRNA (PRKCE) and protein immunoreactivity in a subset of sporadic ALS patients. We furthermore investigated the steady-state levels of both pan and phosphorylated PKCε in doxycycline-activated NSC-34 cell lines carrying the human wild-type (WT) or mutant G93A SOD1 and the biological long-term effect of its transient agonism by Bryostatin-1. The G93A-SOD1 cells showed a significant reduction of the phosphoPKCε/panPKCε ratio compared to the WT. Moreover, a brief pulse activation of PKCε by Bryostatin-1 produced long-term survival in activated G93A-SOD1 degenerating cells in two different cell death paradigms (serum starvation and chemokines-induced toxicity). Altogether, the data support the implication of PKCε in ALS pathophysiology and suggests its pharmacological modulation as a potential neuroprotective strategy, at least in a subgroup of sporadic ALS patients.

Definitions, phenomenology, diagnosis, and management of the disorders of laughter and crying in amyotrophic lateral sclerosis (ALS): Consensus from ALS and Motor Neuron Disease Scientific Department of the Brazilian Academy of Neurology

The spectrum of neuropsychiatric phenomena observed in amyotrophic lateral sclerosis (ALS) is wide and not fully understood. Disorders of laughter and crying stand among the most common manifestations. The aim of this study is to report the results of an educational consensus organized by the Brazilian Academy of Neurology to evaluate the definitions, phenomenology, diagnosis, and management of the disorders of laughter and crying in ALS patients. Twelve members of the Brazilian Academy of Neurology - considered to be experts in the field - were recruited to answer 12 questions about the subject. After exchanging revisions, a first draft was prepared. A face-to-face meeting was held in Fortaleza, Brazil on 9.23.22 to discuss it. The revised version was subsequently emailed to all members of the ALS Scientific Department from the Brazilian Academy of Neurology and the final revised version submitted for publication. The prevalence of pseudobulbar affect/pathological laughter and crying (PBA/PLC) in ALS patients from 15 combined studies and 3906 patients was 27.4% (N = 1070), ranging from 11.4% to 71%. Bulbar onset is a risk factor but there are limited studies evaluating the differences in prevalence among the different motor neuron diseases subtypes, including patients with and without frontotemporal dementia. Antidepressants and a combination of dextromethorphan and quinidine (not available in Brazil) are possible therapeutic options. This group of panelists acknowledge the multiple gaps in the current literature and reinforces the need for further studies.

Targeting Protein Aggregates with Natural Products: An Optional Strategy for Neurodegenerative Diseases

Protein aggregation is one of the hallmarks of aging and aging-related diseases, especially for the neurodegenerative diseases (NDs) such as Alzheimer's disease (AD), Parkinson's disease (PD), Huntington's disease (HD), Amyotrophic lateral sclerosis (ALS), and others. In these diseases, many pathogenic proteins, such as amyloid-β, tau, α-Syn, Htt, and FUS, form aggregates that disrupt the normal physiological function of cells and lead to associated neuronal lesions. Protein aggregates in NDs are widely recognized as one of the important targets for the treatment of these diseases. Natural products, with their diverse biological activities and rich medical history, represent a great treasure trove for the development of therapeutic strategies to combat disease. A number of in vitro and in vivo studies have shown that natural products, by virtue of their complex molecular scaffolds that specifically bind to pathogenic proteins and their aggregates, can inhibit the formation of aggregates, disrupt the structure of aggregates and destabilize them, thereby alleviating conditions associated with NDs. Here, we systematically reviewed studies using natural products to improve disease-related symptoms by reducing or inhibiting the formation of five pathogenic protein aggregates associated with NDs. This information should provide valuable insights into new directions and ideas for the treatment of neurodegenerative diseases.

CXCR2 Is Deregulated in ALS Spinal Cord and Its Activation Triggers Apoptosis in Motor Neuron-Like Cells Overexpressing hSOD1-G93A

Amyotrophic lateral sclerosis (ALS) is a multifactorial neurodegenerative disease characterized by progressive depletion of motor neurons (MNs). Recent evidence suggests a role in ALS pathology for the C-X-C motif chemokine receptor 2 (CXCR2), whose expression was found increased at both mRNA and protein level in cortical neurons of sporadic ALS patients. Previous findings also showed that the receptor inhibition is able to prevent iPSC-derived MNs degeneration in vitro and improve neuromuscular function in SOD1-G93A mice. Here, by performing transcriptional analysis and immunofluorescence studies, we detailed the increased expression and localization of CXCR2 and its main ligand CXCL8 in the human lumbar spinal cord of sporadic ALS patients. We further investigated the functional role of CXCR2/ligands axis in NSC-34 motor neuron-like cells expressing human wild-type (WT) or mutant (G93A) SOD1. A significant expression of CXCR2 was found in doxycycline-induced G93A-SOD1-expressing cells, but not in WT cells. In vitro assays showed CXCR2 activation by GROα and MIP2α, two murine endogenous ligands and functional homologs of CXCL8, reduces cellular viability and triggers apoptosis in a dose dependent manner, while treatment with reparixin, a non-competitive allosteric CXCR2 inhibitor, effectively counteracts GROα and MIP2α toxicity, significantly inhibiting the chemokine-induced cell death. Altogether, data further support a role of CXCR2 axis in ALS etiopathogenesis and confirm its pharmacological modulation as a candidate therapeutic strategy.

Myocilin misfolding and glaucoma: A 20-year update

Mutations in the gene MYOC account for approximately 5% of cases of primary open angle glaucoma (POAG). MYOC encodes for the protein myocilin, a multimeric secreted glycoprotein composed of N-terminal coiled-coil (CC) and leucine zipper (LZ) domains that are connected via a disordered linker to a 30 kDa olfactomedin (OLF) domain. More than 90% of glaucoma-causing mutations are localized to the OLF domain. While myocilin is expressed in numerous tissues, mutant myocilin is only associated with disease in the anterior segment of the eye, in the trabecular meshwork. The prevailing pathogenic mechanism involves a gain of toxic function whereby mutant myocilin aggregates intracellularly instead of being secreted, which causes cell stress and an early timeline for TM cell death, elevated intraocular pressure, and subsequent glaucoma-associated retinal degeneration. In this review, we focus on the work our lab has conducted over the past ∼15 years to enhance our molecular understanding of myocilin-associated glaucoma, which includes details of the molecular structure and the nature of the aggregates formed by mutant myocilin. We conclude by discussing open questions, such as predicting phenotype from genotype alone, the elusive native function of myocilin, and translational directions enabled by our work.

Intranasal administration of edaravone nanoparticles improves its stability and brain bioavailability

The clinical application of EDV, a potent antioxidant drug approved for amyotrophic lateral sclerosis (ALS), is limited by its short biological half-life and poor water solubility necessitating hospitalization during intravenous infusion. Nanotechnology-based drug delivery constitutes a powerful tool through inferring drug stability and targeted drug delivery improving drug bioavailability at the diseased site. Nose-to-brain drug delivery offers direct access to the brain bypassing the blood brain barrier and reducing systemic biodistribution. In this study, we designed EDV-loaded poly(lactic-co-glycolic acid) (PLGA)-based polymeric nanoparticles (NP-EDV) for intranasal administration. NPs were formulated by the nanoprecipitation method. Morphology, EDV loading, physicochemical properties, shelf-life stability, in vitro release and pharmacokinetic assessment in mice were conducted. EDV was efficiently loaded into ∼90 nm NPs, stable up to 30 days of storage, at ∼3% drug loading. NP-EDV reduced H2O2-induced oxidative stress toxicity in mouse microglial cell line BV-2. Optical imaging and ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) showed that intranasal delivery of NP-EDV offered higher and more sustained brain uptake of EDV compared to intravenous administration. This study is the first of its kind to develop an ALS drug in a nanoparticulate formulation for nose-to-brain delivery raising hope to ALS patients where currently treatment options are limited to two clinically approved drugs only.

The landscape of cognitive impairment in superoxide dismutase 1-amyotrophic lateral sclerosis

Although mutations in the superoxide dismutase 1 gene account for only a minority of total amyotrophic lateral sclerosis cases, the discovery of this gene has been crucial for amyotrophic lateral sclerosis research. Since the identification of superoxide dismutase 1 in 1993, the field of amyotrophic lateral sclerosis genetics has considerably widened, improving our understanding of the diverse pathogenic basis of amyotrophic lateral sclerosis. In this review, we focus on cognitive impairment in superoxide dismutase 1-amyotrophic lateral sclerosis patients. Literature has mostly reported that cognition remains intact in superoxide dismutase 1-amyotrophic lateral sclerosis patients, but recent reports highlight frontal lobe function frailty in patients carrying different superoxide dismutase 1-amyotrophic lateral sclerosis mutations. We thoroughly reviewed all the various mutations reported in the literature to contribute to a comprehensive database of superoxide dismutase 1-amyotrophic lateral sclerosis genotype-phenotype correlation. Such a resource could ultimately improve our mechanistic understanding of amyotrophic lateral sclerosis, enabling a more robust assessment of how the amyotrophic lateral sclerosis phenotype responds to different variants across genes, which is important for the therapeutic strategy targeting genetic mutations. Cognition in superoxide dismutase 1-amyotrophic lateral sclerosis deserves further longitudinal research since this peculiar frailty in patients with similar mutations can be conditioned by external factors, including environment and other unidentified agents including modifier genes.

Harnessing deep learning into hidden mutations of neurological disorders for therapeutic challenges

The relevant study of transcriptome-wide variations and neurological disorders in the evolved field of genomic data science is on the rise. Deep learning has been highlighted utilizing algorithms on massive amounts of data in a human-like manner, and is expected to predict the dependency or druggability of hidden mutations within the genome. Enormous mutational variants in coding and noncoding transcripts have been discovered along the genome by far, despite of the fine-tuned genetic proofreading machinery. These variants could be capable of inducing various pathological conditions, including neurological disorders, which require lifelong care. Several limitations and questions emerge, including the use of conventional processes via limited patient-driven sequence acquisitions and decoding-based inferences as well as how rare variants can be deduced as a population-specific etiology. These puzzles require harnessing of advanced systems for precise disease prediction, drug development and drug applications. In this review, we summarize the pathophysiological discoveries of pathogenic variants in both coding and noncoding transcripts in neurological disorders, and the current advantage of deep learning applications. In addition, we discuss the challenges encountered and how to outperform them with advancing interpretation.

Integrated Omic Analysis Delineates Pathways Modulating Toxic TDP-43 Protein Aggregates in Amyotrophic Lateral Sclerosis

Amyotrophic lateral sclerosis (ALS) is a multi-systemic, incurable, amyloid disease affecting the motor neurons, resulting in the death of patients. The disease is either sporadic or familial with SOD1, C9orf72, FUS, and TDP-43 constituting the majority of familial ALS. Multi-omics studies on patients and model systems like mice and yeast have helped in understanding the association of various signaling and metabolic pathways with the disease. The yeast model system has played a pivotal role in elucidating the gene amyloid interactions. We carried out an integrated transcriptomic and metabolomic analysis of the TDP-43 expressing yeast model to elucidate deregulated pathways associated with the disease. The analysis shows the deregulation of the TCA cycle, single carbon metabolism, glutathione metabolism, and fatty acid metabolism. Transcriptomic analysis of GEO datasets of TDP-43 expressing motor neurons from mice models of ALS and ALS patients shows considerable overlap with experimental results. Furthermore, a yeast model was used to validate the obtained results using metabolite addition and gene knock-out experiments. Taken together, our result shows a potential role for the TCA cycle, cellular redox pathway, NAD metabolism, and fatty acid metabolism in disease. Supplementation of reduced glutathione, nicotinate, and the keto diet might help to manage the disease.

Brain metabolic signatures in patients with genetic and nongenetic amyotrophic lateral sclerosis

AIMS

To study the brain metabolic signature in Chinese amyotrophic lateral sclerosis (ALS) patients and compare the difference in brain metabolic patterns between ALS with and without genetic variants.

METHODS

We included 146 patients with ALS and 128 healthy controls (HCs). All patients with ALS underwent genetic testing to screen for ALS related genetic variants and were then divided into genetic (n = 22) and nongenetic ALS (n = 93) subgroups. All participants underwent brain 18 F-FDG-PET scans. Group comparisons were performed using the two-sample t-test model of SPM12.

RESULTS

We identified a large of hypometabolic clusters in ALS patients as compared with HCs, especially in the bilateral basal ganglia, midbrain, and cerebellum. Moreover, hypometabolism in the bilateral temporal lobe, precentral gyrus and hypermetabolism in the left anterior cingulate, occipital lobe, and bilateral frontal lobe were also found in ALS patients as compared with HCs. Compared with nongenetic ALS patients, genetic ALS patients showed hypometabolism in the right postcentral gyrus, precuneus, and middle occipital gyrus. The incidence of sensory disturbance in patients with genetic ALS was higher than that in patients with nongenetic ALS (5 of 22 [22.72%] vs. 7 of 93 [7.52%], p = 0.036).

CONCLUSIONS

Our investigation provided unprecedented evidence of relative hypometabolism in the midbrain and cerebellum in ALS patients. Genetic ALS patients showed a specific signature of brain metabolism and a higher incidence of sensory disturbance, indicating that genetic factors may be an underlying cause affecting the brain metabolism and increasing the risk of sensory disturbance in ALS.

Differences in Cerebral Glucose Metabolism in ALS Patients with and without C9orf72 and SOD1 Mutations

Amyotrophic lateral sclerosis (ALS) is characterized by progressive loss of upper and lower motor neurons. In 10% of patients, the disorder runs in the family. Our aim was to study the impact of ALS-causing gene mutations on cerebral glucose metabolism. Between October 2010 and October 2022, 538 patients underwent genetic testing for mutations with strong evidence of causality for ALS and 18F-2-fluoro-2-deoxy-D-glucose-PET (FDG PET), at University Hospitals Leuven. We identified 48 C9orf72-ALS and 22 SOD1-ALS patients. After propensity score matching, two cohorts of 48 and 21 matched sporadic ALS patients, as well as 20 healthy controls were included. FDG PET images were assessed using a voxel-based and volume-of-interest approach. We observed widespread frontotemporal involvement in all ALS groups, in comparison to healthy controls. The degree of relative glucose metabolism in SOD1-ALS in motor and extra-motor regions did not differ significantly from matched sporadic ALS patients. In C9orf72-ALS, we found more pronounced hypometabolism in the peri-rolandic region and thalamus, and hypermetabolism in the medulla extending to the pons, in comparison to matched sporadic ALS patients. Our study revealed C9orf72-dependent differences in glucose metabolism in the peri-rolandic region, thalamus, and brainstem (i.e., medulla, extending to the pons) in relation to matched sporadic ALS patients.

Cytoplasmic TDP-43 accumulation drives changes in C-bouton number and size in a mouse model of sporadic Amyotrophic Lateral Sclerosis

An altered neuronal excitability of spinal motoneurones has consistently been implicated in Amyotrophic Lateral Sclerosis (ALS) leading to several investigations of synaptic input to these motoneurones. One such input that has repeatedly been shown to be affected is a population of large cholinergic synapses terminating mainly on the soma of the motoneurones referred to as C-boutons. Most research on these synapses during disease progression has used transgenic Superoxide Dismutase 1 (SOD1) mouse models of the disease which have not only produced conflicting findings, but also fail to recapitulate the key pathological feature seen in ALS; cytoplasmic accumulations of TAR DNA-binding protein 43 (TDP-43). Additionally, they fail to distinguish between slow and fast motoneurones, the latter of which have more C-boutons, but are lost earlier in the disease. To circumvent these issues, we quantified the frequency and volume of C-boutons on traced soleus and gastrocnemius motoneurones, representing predominantly slow and fast motor pools respectively. Experiments were performed using the TDP-43ΔNLS mouse model that carries a transgenic construct of TDP-43 devoid of its nuclear localization signal, preventing its nuclear import. This results in the emergence of pathological TDP-43 inclusions in the cytoplasm, modelling the main pathology seen in this disorder, accompanied by a severe and lethal ALS phenotype. Our results confirmed changes in both the number and volume of C-boutons with a decrease in number on the more vulnerable, predominantly fast gastrocnemius motoneurones and an increase in number on the less vulnerable, predominantly slow soleus motoneurones. Importantly, these changes were only found in male mice. However, both sexes and motor pools showed a decrease in C-bouton volume. Our experiments confirm that cytoplasmic TDP-43 accumulation is sufficient to drive C-bouton changes.

Genetics of amyotrophic lateral sclerosis: seeking therapeutic targets in the era of gene therapy

Amyotrophic lateral sclerosis (ALS) is an intractable disease that causes respiratory failure leading to mortality. The main locus of ALS is motor neurons. The success of antisense oligonucleotide (ASO) therapy in spinal muscular atrophy (SMA), a motor neuron disease, has triggered a paradigm shift in developing ALS therapies. The causative genes of ALS and disease-modifying genes, including those of sporadic ALS, have been identified one after another. Thus, the freedom of target choice for gene therapy has expanded by ASO strategy, leading to new avenues for therapeutic development. Tofersen for superoxide dismutase 1 (SOD1) was a pioneer in developing ASO for ALS. Improving protocols and devising early interventions for the disease are vital. In this review, we updated the knowledge of causative genes in ALS. We summarized the genetic mutations identified in familial ALS and their clinical features, focusing on SOD1, fused in sarcoma (FUS), and transacting response DNA-binding protein. The frequency of the C9ORF72 mutation is low in Japan, unlike in Europe and the United States, while SOD1 and FUS are more common, indicating that the target mutations for gene therapy vary by ethnicity. A genome-wide association study has revealed disease-modifying genes, which could be the novel target of gene therapy. The current status and prospects of gene therapy development were discussed, including ethical issues. Furthermore, we discussed the potential of axonal pathology as new therapeutic targets of ALS from the perspective of early intervention, including intra-axonal transcription factors, neuromuscular junction disconnection, dysregulated local translation, abnormal protein degradation, mitochondrial pathology, impaired axonal transport, aberrant cytoskeleton, and axon branching. We simultaneously discuss important pathological states of cell bodies: persistent stress granules, disrupted nucleocytoplasmic transport, and cryptic splicing. The development of gene therapy based on the elucidation of disease-modifying genes and early intervention in molecular pathology is expected to become an important therapeutic strategy in ALS.

Current State and Future Directions in the Diagnosis of Amyotrophic Lateral Sclerosis

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease characterized by loss of upper and lower motor neurons, resulting in progressive weakness of all voluntary muscles and eventual respiratory failure. Non-motor symptoms, such as cognitive and behavioral changes, frequently occur over the course of the disease. Considering its poor prognosis with a median survival time of 2 to 4 years and limited causal treatment options, an early diagnosis of ALS plays an essential role. In the past, diagnosis has primarily been determined by clinical findings supported by electrophysiological and laboratory measurements. To increase diagnostic accuracy, reduce diagnostic delay, optimize stratification in clinical trials and provide quantitative monitoring of disease progression and treatment responsivity, research on disease-specific and feasible fluid biomarkers, such as neurofilaments, has been intensely pursued. Advances in imaging techniques have additionally yielded diagnostic benefits. Growing perception and greater availability of genetic testing facilitate early identification of pathogenic ALS-related gene mutations, predictive testing and access to novel therapeutic agents in clinical trials addressing disease-modified therapies before the advent of the first clinical symptoms. Lately, personalized survival prediction models have been proposed to offer a more detailed disclosure of the prognosis for the patient. In this review, the established procedures and future directions in the diagnostics of ALS are summarized to serve as a practical guideline and to improve the diagnostic pathway of this burdensome disease.

The Impact of Dysregulated microRNA Biogenesis Machinery and microRNA Sorting on Neurodegenerative Diseases

MicroRNAs (miRNAs) are 22-nucleotide noncoding RNAs involved in the differentiation, development, and function of cells in the body by targeting the 3'- untranslated regions (UTR) of mRNAs for degradation or translational inhibition. miRNAs not only affect gene expression inside the cells but also, when sorted into exosomes, systemically mediate the communication between different types of cells. Neurodegenerative diseases (NDs) are age-associated, chronic neurological diseases characterized by the aggregation of misfolded proteins, which results in the progressive degeneration of selected neuronal population(s). The dysregulation of biogenesis and/or sorting of miRNAs into exosomes was reported in several NDs, including Huntington's disease (HD), Parkinson's disease (PD), amyotrophic lateral sclerosis (ALS), and Alzheimer's disease (AD). Many studies support the possible roles of dysregulated miRNAs in NDs as biomarkers and therapeutic treatments. Understanding the molecular mechanisms underlying the dysregulated miRNAs in NDs is therefore timely and important for the development of diagnostic and therapeutic interventions. In this review, we focus on the dysregulated miRNA machinery and the role of RNA-binding proteins (RBPs) in NDs. The tools that are available to identify the target miRNA-mRNA axes in NDs in an unbiased manner are also discussed.

Gene targeting in amyotrophic lateral sclerosis using causality-based feature selection and machine learning

BACKGROUND

Amyotrophic lateral sclerosis (ALS) is a rare progressive neurodegenerative disease that affects upper and lower motor neurons. As the molecular basis of the disease is still elusive, the development of high-throughput sequencing technologies, combined with data mining techniques and machine learning methods, could provide remarkable results in identifying pathogenetic mechanisms. High dimensionality is a major problem when applying machine learning techniques in biomedical data analysis, since a huge number of features is available for a limited number of samples. The aim of this study was to develop a methodology for training interpretable machine learning models in the classification of ALS and ALS-subtypes samples, using gene expression datasets.

METHODS

We performed dimensionality reduction in gene expression data using a semi-automated preprocessing systematic gene selection procedure using Statistically Equivalent Signature (SES), a causality-based feature selection algorithm, followed by Boosted Regression Trees (XGBoost) and Random Forest to train the machine learning classifiers. The SHapley Additive exPlanations (SHAP values) were used for interpretation of the machine learning classifiers. The methodology was developed and tested using two distinct publicly available ALS RNA-seq datasets. We evaluated the performance of SES as a dimensionality reduction method against: (a) Least Absolute Shrinkage and Selection Operator (LASSO), and (b) Local Outlier Factor (LOF).

RESULTS

The proposed methodology achieved 85.18% accuracy for the classification of cerebellum or frontal cortex samples as C9orf72-related familial ALS, sporadic ALS or healthy samples. Importantly, the genes identified as the most determinative have also been reported as disease-associated in ALS literature. When tested in the evaluation dataset, the methodology achieved 88.89% accuracy for the classification of sporadic ALS motor neuron samples. When LASSO was used as feature selection method instead of SES, the accuracy of the machine learning classifiers ranged from 74.07 to 96.30%, depending on tissue assessed, while LOF underperformed significantly (77.78% accuracy for the classification of pooled cerebellum and frontal cortex samples).

CONCLUSIONS

Using SES, we addressed the challenge of high dimensionality in gene expression data analysis, and we trained accurate machine learning ALS classifiers, specific for the gene expression patterns of different disease subtypes and tissue samples, while identifying disease-associated genes.

Leveraging Computational Intelligence Techniques for Diagnosing Degenerative Nerve Diseases: A Comprehensive Review, Open Challenges, and Future Research Directions

Degenerative nerve diseases such as Alzheimer's and Parkinson's diseases have always been a global issue of concern. Approximately 1/6th of the world's population suffers from these disorders, yet there are no definitive solutions to cure these diseases after the symptoms set in. The best way to treat these disorders is to detect them at an earlier stage. Many of these diseases are genetic; this enables machine learning algorithms to give inferences based on the patient's medical records and history. Machine learning algorithms such as deep neural networks are also critical for the early identification of degenerative nerve diseases. The significant applications of machine learning and deep learning in early diagnosis and establishing potential therapies for degenerative nerve diseases have motivated us to work on this review paper. Through this review, we covered various machine learning and deep learning algorithms and their application in the diagnosis of degenerative nerve diseases, such as Alzheimer's disease and Parkinson's disease. Furthermore, we also included the recent advancements in each of these models, which improved their capabilities for classifying degenerative nerve diseases. The limitations of each of these methods are also discussed. In the conclusion, we mention open research challenges and various alternative technologies, such as virtual reality and Big data analytics, which can be useful for the diagnosis of degenerative nerve diseases.

The paradigm of amyloid precursor protein in amyotrophic lateral sclerosis: The potential role of the 682YENPTY687 motif

Neurodegenerative diseases are characterized by the progressive decline of neuronal function in several brain areas, and are always associated with cognitive, psychiatric, or motor deficits due to the atrophy of certain neuronal populations. Most neurodegenerative diseases share common pathological mechanisms, such as neurotoxic protein misfolding, oxidative stress, and impairment of autophagy machinery. Amyotrophic lateral sclerosis (ALS) is one of the most common adult-onset motor neuron disorders worldwide. It is clinically characterized by the selective and progressive loss of motor neurons in the motor cortex, brain stem, and spinal cord, ultimately leading to muscle atrophy and rapidly progressive paralysis. Multiple recent studies have indicated that the amyloid precursor protein (APP) and its proteolytic fragments are not only drivers of Alzheimer's disease (AD) but also one of the earliest signatures in ALS, preceding or anticipating neuromuscular junction instability and denervation. Indeed, altered levels of APP peptides have been found in the brain, muscles, skin, and cerebrospinal fluid of ALS patients. In this short review, we discuss the nature and extent of research evidence on the role of APP peptides in ALS, focusing on the intracellular C-terminal peptide and its regulatory motif ₆₈₂YENPTY₆₈₇, with the overall aim of providing new frameworks and perspectives for intervention and identifying key questions for future investigations.

Case report: p.Glu134del SOD1 mutation in two apparently unrelated ALS patients with mirrored phenotype

With upcoming personalized approaches based on genetics, it is important to report new mutations in amyotrophic lateral sclerosis (ALS) genes in order to understand their pathogenicity and possible patient responses to specific therapies. SOD1 mutations are the second most frequent genetic cause of ALS in European populations. Here, we describe two seemingly unrelated Italian patients with ALS carrying the same SOD1 heterozygous c.400_402 deletion (p.Glu134del). Both patients had spinal onset in their lower limbs, progressive muscular weakness with respiratory involvement, and sparing bulbar function. In addition to the clinical picture, we discuss the possible pathogenic role of this unfamiliar SOD1 mutation.

Case report: Flail leg syndrome in familial amyotrophic lateral sclerosis with L144S SOD1 mutation

We observed a Polish family with familial amyotrophic lateral sclerosis with heterozygous L144S SOD1 mutation, which manifested clinically as flail leg syndrome. Flail leg syndrome is a rare phenotype of amyotrophic lateral sclerosis, with slow progression, long survival, and predominance of lower motor neuron signs at onset, as a triad of distal paresis, muscle atrophy, and hyporeflexia/areflexia, confined to the lower limbs for an extended period of time. Although familial amyotrophic lateral sclerosis is usually associated with a worse prognosis than the sporadic form of the disease, the clinical course of the disease in patients with L144S SOD1 mutation is benign, with slow progression and long survival. This unique case report provides an in-depth clinical analysis of all of the symptomatic members of a family, who were diagnosed with amyotrophic lateral sclerosis in our clinic, including three siblings (two brothers and a deceased sister) with flail leg syndrome and their fraternal aunt, who has been previously misdiagnosed with cervical myelopathy and is living with symptoms of the disease for 15 years. Sanger sequencing of the SOD1 gene was performed in all of the living patients, revealing an L144S (c.434T>C, p.Leu145Ser) heterozygous mutation. The aim of this case report is to increase the physician's awareness of the atypical phenotypes of amyotrophic lateral sclerosis and hopefully, to encourage further research on the factors responsible for delayed disease progression in patients with L144S SOD1 mutation.

Amyotrophic Lateral Sclerosis Risk Genes and Suppressor

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease that leads to death by progressive paralysis and respiratory failure within 2-4 years of onset. About 90-95% of ALS cases are sporadic (sALS), and 5-10% are inherited through family (fALS). Though the mechanisms of the disease are still poorly understood, so far, approximately 40 genes have been reported as ALS causative genes. The mutations in some crucial genes, like SOD1, C9ORF72, FUS, and TDP-43, are majorly associated with ALS, resulting in ROS-associated oxidative stress, excitotoxicity, protein aggregation, altered RNA processing, axonal and vesicular trafficking dysregulation, and mitochondrial dysfunction. Recent studies show that dysfunctional cellular pathways get restored as a result of the repair of a single pathway in ALS. In this review article, our aim is to identify putative targets for therapeutic development and the importance of a single suppressor to reduce multiple symptoms by focusing on important mutations and the phenotypic suppressors of dysfunctional cellular pathways in crucial genes as reported by other studies.

Molecular Investigations of Protein Aggregation in the Pathogenesis of Amyotrophic Lateral Sclerosis

Amyotrophic lateral sclerosis (ALS) is a devastating progressive neurodegenerative disorder characterized by selective loss of lower and upper motor neurons (MNs) in the brain and spinal cord, resulting in paralysis and eventually death due to respiratory insufficiency. Although the fundamental physiological mechanisms underlying ALS are not completely understood, the key neuropathological hallmarks of ALS pathology are the aggregation and accumulation of ubiquitinated protein inclusions within the cytoplasm of degenerating MNs. Herein, we discuss recent insights into the molecular mechanisms that lead to the accumulation of protein aggregates in ALS. This will contribute to a better understanding of the pathophysiology of the disease and may open novel avenues for the development of therapeutic strategies.

Amyotrophic Lateral Sclerosis, FUS and Protein Synthesis Defects

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease that mainly affects the motor system. It is a very heterogeneous disorder, so far more than 40 genes have been described as responsible for ALS. The cause of motor neuron degeneration is not yet fully understood, but there is consensus in the literature that it is the result of a complex interplay of several pathogenic processes, which include alterations in nucleocytoplasmic transport, defects in transcription and splicing, altered formation and/or disassembly of stress granules and impaired proteostasis. These defects result in protein aggregation, impaired DNA repair, mitochondrial dysfunction and oxidative stress, neuroinflammation, impaired axonal transport, impaired vesicular transport, excitotoxicity, as well as impaired calcium influx. We argue here that all the above functions ultimately lead to defects in protein synthesis. Fused in Sarcoma (FUS) is one of the genes associated with ALS. It causes ALS type 6 when mutated and is found mislocalized to the cytoplasm in the motor neurons of sporadic ALS patients (without FUS mutations). In addition, FUS plays a role in all cellular functions that are impaired in degenerating motor neurons. Moreover, ALS patients with FUS mutations present the first symptoms significantly earlier than in other forms of the disease. Therefore, the aim of this review is to further discuss ALS6, detail the cellular functions of FUS, and suggest that the localization of FUS, as well as protein synthesis rates, could be hallmarks of the ALS phenotype and thus good therapeutic targets.

Sensory Involvement in Amyotrophic Lateral Sclerosis

Although amyotrophic lateral sclerosis (ALS) is pre-eminently a motor disease, the existence of non-motor manifestations, including sensory involvement, has been described in the last few years. Although from a clinical perspective, sensory symptoms are overshadowed by their motor manifestations, this does not mean that their pathological significance is not relevant. In this review, we have made an extensive description of the involvement of sensory and autonomic systems described to date in ALS, from clinical, neurophysiological, neuroimaging, neuropathological, functional, and molecular perspectives.

Integrated network pharmacology approach shows a potential role of Ginseng catechins and ginsenosides in modulating protein aggregation in Amyotrophic Lateral Sclerosis

Amyotrophic lateral Sclerosis is an incurable, progressive neurodegenerative motor neuron disease. The disease is characterized by protein aggregates. The symptoms include weakness, denervation of muscles, atrophy and progressive paralysis of bulbar and respiratory muscles and dysphagia. Various secondary metabolites are evaluated for their ability to improve symptoms in ALS. Ginseng has been traditionally used for treating several neurodegenerative diseases. Several studies using model systems have shown a potential role of Ginseng catechins and Ginsenosides in clearing protein aggregation associated with ALS. We focus on Network pharmacology approach to understand the effect of Ginseng catechins or ginsenosides on protein aggregation associated with ALS. A catechin/ginsenoside-protein interaction network was generated and the pathways obtained were compared with those obtained from transcriptomic datasets of ALS from GEO database. Knock out of MAPK14, AKT and GSK from Catechin and BACE 1 from ginsenoside modulated pathways inhibited protein aggregation. Catechins and ginsenosides have potential as therapeutic agents in the management of ALS.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13205-022-03401-1.

Characterisation of retrotransposon insertion polymorphisms in whole genome sequencing data from individuals with amyotrophic lateral sclerosis

The genetics of an individual is a crucial factor in understanding the risk of developing the neurodegenerative disease amyotrophic lateral sclerosis (ALS). There is still a large proportion of the heritability of ALS, particularly in sporadic cases, to be understood. Among others, active transposable elements drive inter-individual variability, and in humans long interspersed element 1 (LINE1, L1), Alu and SINE-VNTR-Alu (SVA) retrotransposons are a source of polymorphic insertions in the population. We undertook a pilot study to characterise the landscape of non-reference retrotransposon insertion polymorphisms (non-ref RIPs) in 15 control and 15 ALS individuals' whole genomes from Project MinE, an international project to identify potential genetic causes of ALS. The combination of two bioinformatics tools (mobile element locator tool (MELT) and TEBreak) identified on average 1250 Alu, 232 L1 and 77 SVA non-ref RIPs per genome across the 30 analysed. Further PCR validation of individual polymorphic retrotransposon insertions showed a similar level of accuracy for MELT and TEBreak. Our preliminary study did not identify a specific RIP or a significant difference in the total number of non-ref RIPs in ALS compared to control genomes. The use of multiple bioinformatic tools improved the accuracy of non-ref RIP detection and our study highlights the potential importance of studying these elements further in ALS.

Interrogating the Metabolomic Profile of Amyotrophic Lateral Sclerosis in the Post-Mortem Human Brain by Infrared Matrix-Assisted Laser Desorption Electrospray Ionization (IR-MALDESI) Mass Spectrometry Imaging (MSI)

Amyotrophic lateral sclerosis (ALS) is an idiopathic, fatal neurodegenerative disease characterized by progressive loss of motor function with an average survival time of 2-5 years after diagnosis. Due to the lack of signature biomarkers and heterogenous disease phenotypes, a definitive diagnosis of ALS can be challenging. Comprehensive investigation of this disease is imperative to discovering unique features to expedite the diagnostic process and improve diagnostic accuracy. Here, we present untargeted metabolomics by mass spectrometry imaging (MSI) for comparing sporadic ALS (sALS) and C9orf72 positive (C9Pos) post-mortem frontal cortex human brain tissues against a control cohort. The spatial distribution and relative abundance of metabolites were measured by infrared matrix-assisted laser desorption electrospray ionization (IR-MALDESI) MSI for association to biological pathways. Proteomic studies on the same patients were completed via LC-MS/MS in a previous study, and results were integrated with imaging metabolomics results to enhance the breadth of molecular coverage. Utilizing METASPACE annotation platform and MSiPeakfinder, nearly 300 metabolites were identified across the sixteen samples, where 25 were identified as dysregulated between disease cohorts. The dysregulated metabolites were further examined for their relevance to alanine, aspartate, and glutamate metabolism, glutathione metabolism, and arginine and proline metabolism. The dysregulated pathways discussed are consistent with reports from other ALS studies. To our knowledge, this work is the first of its kind, reporting on the investigation of ALS post-mortem human brain tissue analyzed by multiomic MSI.

Biomarkers and molecular mechanisms of Amyotrophic Lateral Sclerosis

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease in adults involving non-demyelinating motor disorders. About 90% of ALS cases are sporadic, while 10-12% of cases are due to some genetic reasons. Mutations in superoxide dismutase 1 (SOD1), TAR, c9orf72 (chromosome 9 open reading frame 72) and VAPB genes are commonly found in ALS patients. Therefore, the mechanism of ALS development involves oxidative stress, endoplasmic reticulum stress, glutamate excitotoxicity and aggregation of proteins, neuro-inflammation and defective RNA function. Cholesterol and LDL/HDL levels are also associated with ALS development. As a result, sterols could be a suitable biomarker for this ailment. The main mechanisms of ALS development are reticulum stress, neuroinflammation and RNA metabolism. The multi-nature development of ALS makes it more challenging to pinpoint a treatment.

A novel TFG variant of uncertain significance in amyotrophic lateral sclerosis: A case report and review of literature

Introduction

Amyotrophic lateral sclerosis is a neurodegenerative disease with wide variation of genetics associated with it. Among the different genes described, mutation in TFG is a rare finding in amyotrophic lateral sclerosis.

Case presentation

A 35 years old right-handed male presenting with ipsilateral weakness was diagnosed with amyotrophic lateral sclerosis. He was found to have missense variant of TFG with uncertain significance on exome sequencing.

Clinical discussion

The genetics involved in amyotrophic lateral sclerosis is ever-evolving. The identification of new TFG variant in this disease adds another evidence to the role of TFG in neurodegenerative disease.

Conclusions

The finding of TFG variant of uncertain significance is a rare finding in amyotrophic lateral sclerosis. And with the identification of new TFG variant, it leads to further understanding of spectrum of TFG and its pathophysiology in amyotrophic lateral sclerosis.