Genetic Spectrum and Variability in Chinese Patients with Amyotrophic Lateral Sclerosis

Protein Structure-based FUS Mutational Subtypes Are Associated With Protein Mislocalization in Amyotrophic Lateral Sclerosis Patients

The mislocalization of RNA-binding proteins (RBPs) from nucleus to cytoplasm and the formation of aggregates are hallmarks of neurodegeneration. Amyotrophic lateral sclerosis (ALS) disease-causing mutations in the fused in sarcoma (FUS) gene, encoding an RNA-binding protein, cluster at the C-terminal proline/tyrosine-nuclear localization signal (PY-NLS) domain, which is crucial for mediating nucleus-cytoplasm translocation by binding to Transportin-1. However, the mechanisms underlying heterogeneous protein mislocalization and age at onset (AAO) of ALS cases carrying FUS PY-NLS mutations remain unclear. Here, we screened FUS mutations in 416 ALS patients, and identified 12 patients carrying four FUS mutations at the p.R521 locus of PY-NLS domain (p.R521P, p.R521C, p.R521G, p.R521H), exhibiting highly variable AAO (20-56 years). AlphaFold-2 predicted protein structures classified FUS p.R521 mutants into alpha-helix containing (p.R521C, p.R521H) and alpha-helix disrupted (p.R521P, p.R521G) subgroups. Isothermal titration calorimetry experiment showed that the FUS alpha-helix disrupted subgroup had a reduced binding affinity with transportin-1, which is essential for mediating the nucleus-cytoplasm translocation. Furthermore, immunofluorescence in HEK-293 T and SH-SY5Y cells revealed more protein mislocalization in the FUS alpha-helix disrupted subgroup compared to the alpha-helix containing subgroup. FUS mislocalization status is also significantly associated with ALS AAO. Finally, the alpha-helix structure based FUS-ALS subgroups exhibited significantly different AAO (P = 0.036) in our cohort, but not in a Chinese cohort including published dataset. In summary, we showed highly diverse phenotypes in ALS patients with FUS R521 mutants, and implicated a link between genetic mutation related C-terminal structure with the status of FUS protein mislocalization.

Multiple Roles for Neuregulins and Their ERBB Receptors in Neurodegenerative Disease Pathogenesis and Therapy

The role that neurotrophins, such as nerve growth factor, play in the pathogenesis of neurodegenerative diseases has long been appreciated. However, the neuregulin (NRG) family of growth factors and/or their v-erb-B2 avian erythroblastic leukemia viral oncogene homolog (ERBB) receptors have also been implicated in the pathogenesis of conditions, such as Alzheimer disease (AD), frontotemporal lobar degeneration (FTLD), and amyotrophic lateral sclerosis (ALS). In this review, we consider i) the structural variability of NRG isoforms generated by alternative RNA splicing, the use of multiple promoters and proteolysis, and the impact that this structural variability has on neuronal and glial physiology during development and adulthood. We discuss ii) the NRG receptors ERBB2, ERBB3, and ERBB4, how activation of each of these receptors further diversifies NRG actions in the central nervous system, and how dementia-related proteins, such as γ-secretase modulate the action of NRGs and their ERBB receptors. We then iii) turn to the abnormalities in NRG and ERBB expression and function evident in human AD and mouse AD models, how these abnormalities affect brain function, and attempts to use NRGs to treat AD. Finally, iv) we discuss NRG effects on the survival and function of neurons relevant to FTLD and ALS, alterations in NRG/ERBB signaling identified in these conditions, and the recent discovery of multiple human pedigrees in which autosomal dominant FTLD/ALS potentially results from point mutations in ERBB4.

Clinical characterization and founder effect analysis in Chinese amyotrophic lateral sclerosis patients with SOD1 common variants

OBJECTIVE

In the Asian population, SOD1 variants are the most common cause of amyotrophic lateral sclerosis (ALS). To date, more than 200 variants have been reported in SOD1. This study aimed to summarize the genotype-phenotype correlation and determine whether the patients carrying common variants derive from a common ancestor.

METHODS

A total of 103 sporadic ALS (SALS) and 11 familial ALS (FALS) probands were included and variants were screened by whole exome sequencing. Functional analyses were performed on fibroblasts derived from patients with SOD1 p.V48A and control. Haplotype analysis was performed in the probands with p.H47R or p.V48A and their familial members.

RESULTS

A total of 25 SOD1 variants were identified in 44 probands, in which p.H47R, p.V48A and p.C112Y variants were the most common variants. 94.3% and 60% of patients with p.H47R or p.V48A had lower limb onset with predominant lower motor neurons (LMNs) involvement. Patients with p.H47R had a slow progression and prolonged survival time, while patients with p.V48A exhibited a duration of 2-5 years. Patients with p.C112Y variant showed remarkable phenotypic variation in age at onset and disease course. SOD1V48A fibroblasts showed mutant SOD1 aggregate formation, enhanced intracellular reactive oxygen species level, and decreased mitochondrial membrane potential compared to the control fibroblast. Haplotype analysis showed that seven families had two different haplotypes. p.H47R and p.V48A variants did not originate from a common founder.

CONCLUSIONS

Our study expanded the understanding of the genotype-phenotype correlation of ALS with SOD1 variants and revealed that the common p.H47R or p.V48A variant did not have a founder effect.

Exploring the impact of circular RNA on ALS progression: A systematic review

Amyotrophic lateral sclerosis is a neurodegenerative disease that damages motor neurons and causes gradual muscular weakening and paralysis. Although studies have linked a number of genetic and environmental factors to ALS, the specific causes and mechanisms of the disease are still unclear. The pivotal role of circular RNA in the pathogenesis of ALS is a newly emerging area of research. The term "circular RNA" describes a particular class of RNA molecule that, in contrast to most RNA molecules, has a closed-loop structure. According to recent research, circular RNA might be essential for the development and progression of ALS. It has been discovered that these circular RNAs support important cellular functions related to ALS, including protein turnover, mitochondrial function, RNA processing, and cellular transport. Gaining knowledge about the precise roles and processes of circular RNA in the development of ALS could assist in understanding the pathophysiology of the disease and possibly pave the way for the development of targeted therapies. However, the understanding of circular RNA in ALS is still limited, and more research is needed to fully elucidate its role. In order to gain a comprehensive understanding of the role of circRNAs in ALS, it is imperative to delve into the various mechanisms through which circRNAs may contribute to the development and progression of the disease. Examining the current status of circRNA research in ALS and offering insights into their potential as therapeutic targets and diagnostic markers are the primary objectives of this review.

Genotype-phenotype association and functional analysis of hnRNPA1 mutations in amyotrophic lateral sclerosis

BACKGROUND

Pathogenic variants in hnRNPA1 have been reported in amyotrophic lateral sclerosis (ALS) patients. However, studies on hnRNPA1 mutant spectrum and pathogenicity of variants were rare.

METHODS

We performed whole exome sequencing of ALS-associated genes and subsequent verification of rare variants in hnRNPA1 in our ALS patients. The hnRNPA1 mutations reported in literature were reviewed and combined with our results to determine the genotype-phenotype relationship. Functional analysis of the novel variant p.G195A was performed in vitro by transfection of mutant hnRNPA1 into 293T cell.

RESULTS

Among 207 ALS patients recruited, 3 rare hnRNPA1 variants were identified (mutant frequency 1.45%), including two recurrent mutations (p.P340S and p.G283R), and a novel rare variant p.G195A. In combination with previous reports, there are 27 ALS patients with 15 hnRNPA1 mutations identified. Disease onset age was 47.90 ± 1.52 years with predominant limb onset. The p.P340S mutation caused flail arm syndrome (FAS) in two independent families with extended life expectancy. The newly identified p.G195A mutation, lying at the start of the PrLD ("prion-like" domain)/LCD (low-complexity domain), causes local structural changes in 3D protein prediction. Upon sodium arsenite exposure, mutant hnRNPA1 retained in the nucleus but deficit of cytoplasmic G3BP1-positive stress granule clearance was observed. This is different from the p.P340S mutation which caused both cytoplasmic translocation and stress granule formation. No cytoplasmic TDP-43 translocation was observed.

CONCLUSION

Mutations in hnRNPA1 are overall minor in ALS patients. The p.P340S mutation is associated with manifestation of FAS. Mutations in LCD of hnRNPA1 cause stress granule misprocessing.

Variability in SOD1-associated amyotrophic lateral sclerosis: geographic patterns, clinical heterogeneity, molecular alterations, and therapeutic implications

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease characterized by progressive loss of motor neurons, resulting in global health burden and limited post-diagnosis life expectancy. Although primarily sporadic, familial ALS (fALS) cases suggest a genetic basis. This review focuses on SOD1, the first gene found to be associated with fALS, which has been more recently confirmed by genome sequencing. While informative, databases such as ALSoD and STRENGTH exhibit regional biases. Through a systematic global examination of SOD1 mutations from 1993 to 2023, we found different geographic distributions and clinical presentations. Even though different SOD1 variants are expressed at different protein levels and have different half-lives and dismutase activities, these alterations lead to loss of function that is not consistently correlated with disease severity. Gain of function of toxic aggregates of SOD1 resulting from mutated SOD1 has emerged as one of the key contributors to ALS. Therapeutic interventions specifically targeting toxic gain of function of mutant SOD1, including RNA interference and antibodies, show promise, but a cure remains elusive. This review provides a comprehensive perspective on SOD1-associated ALS and describes molecular features and the complex genetic landscape of SOD1, highlighting its importance in determining diverse clinical manifestations observed in ALS patients and emphasizing the need for personalized therapeutic strategies.

Ebselen analogues delay disease onset and its course in fALS by on-target SOD-1 engagement

Amyotrophic lateral sclerosis (ALS) selectively affects motor neurons. SOD1 is the first causative gene to be identified for ALS and accounts for at least 20% of the familial (fALS) and up to 4% of sporadic (sALS) cases globally with some geographical variability. The destabilisation of the SOD1 dimer is a key driving force in fALS and sALS. Protein aggregation resulting from the destabilised SOD1 is arrested by the clinical drug ebselen and its analogues (MR6-8-2 and MR6-26-2) by redeeming the stability of the SOD1 dimer. The in vitro target engagement of these compounds is demonstrated using the bimolecular fluorescence complementation assay with protein-ligand binding directly visualised by co-crystallography in G93A SOD1. MR6-26-2 offers neuroprotection slowing disease onset of SOD1G93A mice by approximately 15 days. It also protected neuromuscular junction from muscle denervation in SOD1G93A mice clearly indicating functional improvement.

The prognostic value of systematic genetic screening in amyotrophic lateral sclerosis patients

BACKGROUND

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease with complex genetic architecture. Emerging evidence has indicated comorbidity between ALS and autoimmune conditions, suggesting a potential shared genetic basis. The objective of this study is to assess the prognostic value of systematic screening for rare deleterious mutations in genes associated with ALS and aberrant inflammatory responses.

METHODS

A discovery cohort of 494 patients and a validation cohort of 69 patients were analyzed in this study, with population-matched healthy subjects (n = 4961) served as controls. Whole exome sequencing (WES) was performed to identify rare deleterious variants in 50 ALS genes and 1177 genes associated with abnormal inflammatory responses. Genotype-phenotype correlation was assessed, and an integrative prognostic model incorporating genetic and clinical factors was constructed.

RESULTS

In the discovery cohort, 8.1% of patients carried confirmed ALS variants, and an additional 15.2% of patients carried novel ALS variants. Gene burden analysis revealed 303 immune-implicated genes with enriched rare variants, and 13.4% of patients harbored rare deleterious variants in these genes. Patients with ALS variants exhibited a more rapid disease progression (HR 2.87 [95% CI 2.03-4.07], p < 0.0001), while no significant effect was observed for immune-implicated variants. The nomogram model incorporating genetic and clinical information demonstrated improved accuracy in predicting disease outcomes (C-index, 0.749).

CONCLUSION

Our findings enhance the comprehension of the genetic basis of ALS within the Chinese population. It also appears that rare deleterious mutations occurring in immune-implicated genes exert minimal influence on the clinical trajectories of ALS patients.

Unveiling the SOD1-mediated ALS phenotype: insights from a comprehensive meta-analysis

BACKGROUND AND OBJECTIVES

Amyotrophic lateral sclerosis associated with mutations in SOD1 (SOD1-ALS) might be susceptible to specific treatment. The aim of the study is to outline the clinical features of SOD1-ALS patients by comparing them to patients without ALS major gene variants and patients with variants in other major ALS genes. Defining SOD1-ALS phenotype may assist clinicians in identifying patients who should be prioritized for genetic testing.

METHODS

We performed an extensive literature research including original studies which reported the clinical features of SOD1-ALS and at least one of the following patient groups: C9ORF72 hexanucleotide repeat expansion (C9-ALS), TARDBP (TARDBP-ALS), FUS (FUS-ALS) or patients without a positive test for a major-ALS gene (N-ALS). A random effects meta-analytic model was applied to clinical data extracted encompassing sex, site and age of onset. To reconstruct individual patient survival data, the published Kaplan-Meier curves were digitized. Data were measured as odds ratio (OR) or standardized mean difference (SMD) as appropriate. Median survival was compared between groups.

RESULTS

Twenty studies met the inclusion criteria. We identified 721 SOD1-ALS, 470 C9-ALS, 183 TARDBP-ALS, 113 FUS-ALS and 2824 N-ALS. SOD1-ALS showed a higher rate of spinal onset compared with N-ALS and C9-ALS (OR = 4.85, 95% CI = 3.04-7.76; OR = 10.47, 95% CI = 4.32-27.87) and an earlier onset compared with N-ALS (SMD = - 0.45, 95% CI = - 0.72 to - 0.18). SOD1-ALS had a similar survival compared with N-ALS (p = 0.14), a longer survival compared with C9-ALS (p < 0.01) and FUS-ALS (p = 0.019) and a shorter survival compared with TARDBP-ALS (p < 0.01).

DISCUSSION

This study indicates the presence of a specific SOD1-ALS phenotype. Insights in SOD1-ALS clinical features are important in genetic counseling, disease prognosis and support patients' stratification in clinical trials.

Variability in Clinical Phenotype in TARDBP Mutations: Amyotrophic Lateral Sclerosis Case Description and Literature Review

Mutations in the 43 kDa transactive-response (TAR)-DNA-binding protein (TARDBP) are associated with 2-5% of familial Amyotrophic Lateral Sclerosis (ALS) cases. TAR DNA-Binding Protein 43 (TDP-43) is an RNA/DNA-binding protein involved in several cellular mechanisms (e.g., transcription, pre-mRNA processing, and splicing). Many ALS-linked TARDBP mutations have been described in the literature, but few phenotypic data on monogenic TARDBP-mutated ALS are available. In this paper, (1) we describe the clinical features of ALS patients carrying mutations in the TARDBP gene evaluated at the Tertiary ALS Center at Maggiore della Carità University Hospital, Novara, Italy, from 2010 to 2020 and (2) present the results of our review of the literature on this topic, analyzing data obtained for 267 patients and highlighting their main clinical and demographic features.

Clinical, genetic, and molecular characteristics in a central-southern Chinese cohort of genetic leukodystrophies

OBJECTIVE

Leukodystrophies are a diverse group of rare inherited disorders that affect the white matter of the central nervous system with a wide phenotypic spectrum. We aimed to characterize the clinical and genetic features of leukodystrophies in a central-southern Chinese cohort.

METHODS

A cohort of 16 Chinese probands with leukodystrophy was recruited and performed genetic analysis by targeted panels or whole-exome sequencing. Further functional analysis of identified mutations in the colony stimulating factor 1 receptor (CSF1R) gene was explored.

RESULTS

A total of eight pathogenic variants (3 novel, 5 documented) were identified in genes including AARS2, ABCD1, CSF1R, and GALC. Common symptoms of leukodystrophy such as cognitive decline, behavioral symptoms, bradykinesia, and spasticity were observed in mutation carriers as well as other rare features (e.g., seizure, dysarthric, and vision impairment). Overexpressing CSF1R mutants p.M875I and p.F971Sfs*7 in vitro showed pronounced cleavage CSF1R and suppressed protein expression, respectively, and reduced transcripts of both mutants were observed. CSF1 treatment revealed deficient and suppressed CSF1R phospho-activation with the mutants. In contrast to the plasma membrane and endoplasmic reticulum (ER) localized wild-type CSF1R, M875I mutant showed much less membrane association and greater detainment in the ER, whereas F971Sfs*7 mutation led to aberrant non-ER localization. Both mutations caused suppressed cell viability, which was partially resulted from deficient/suppressed CSF1R-ERK signaling.

INTERPRETATION

In summary, our findings expand the mutation spectrum of these genes in leukodystrophies. Supported by in vitro validation of the pathogenicity of heterozygous CSF1R mutations, our data also provide insights into the pathogenic mechanisms of CSF1R-related leukodystrophy.

Spectrum and frequency of genetic variants in sporadic amyotrophic lateral sclerosis

Therapy of motoneuron diseases entered a new phase with the use of intrathecal antisense oligonucleotide therapies treating patients with specific gene mutations predominantly in the context of familial amyotrophic lateral sclerosis. With the majority of cases being sporadic, we conducted a cohort study to describe the mutational landscape of sporadic amyotrophic lateral sclerosis. We analysed genetic variants in amyotrophic lateral sclerosis-associated genes to assess and potentially increase the number of patients eligible for gene-specific therapies. We screened 2340 sporadic amyotrophic lateral sclerosis patients from the German Network for motor neuron diseases for variants in 36 amyotrophic lateral sclerosis-associated genes using targeted next-generation sequencing and for the C9orf72 hexanucleotide repeat expansion. The genetic analysis could be completed on 2267 patients. Clinical data included age at onset, disease progression rate and survival. In this study, we found 79 likely pathogenic Class 4 variants and 10 pathogenic Class 5 variants (without the C9orf72 hexanucleotide repeat expansion) according to the American College of Medical Genetics and Genomics guidelines, of which 31 variants are novel. Thus, including C9orf72 hexanucleotide repeat expansion, Class 4, and Class 5 variants, 296 patients, corresponding to ∼13% of our cohort, could be genetically resolved. We detected 437 variants of unknown significance of which 103 are novel. Corroborating the theory of oligogenic causation in amyotrophic lateral sclerosis, we found a co-occurrence of pathogenic variants in 10 patients (0.4%) with 7 being C9orf72 hexanucleotide repeat expansion carriers. In a gene-wise survival analysis, we found a higher hazard ratio of 1.47 (95% confidence interval 1.02-2.1) for death from any cause for patients with the C9orf72 hexanucleotide repeat expansion and a lower hazard ratio of 0.33 (95% confidence interval 0.12-0.9) for patients with pathogenic SOD1 variants than for patients without a causal gene mutation. In summary, the high yield of 296 patients (∼13%) harbouring a pathogenic variant and oncoming gene-specific therapies for SOD1/FUS/C9orf72, which would apply to 227 patients (∼10%) in this cohort, corroborates that genetic testing should be made available to all sporadic amyotrophic lateral sclerosis patients after respective counselling.

Clinical and genetic characteristics in a central-southern Chinese cohort of early-onset Alzheimer's disease

Background

Mutations in the presenilin-1 (PSEN1), presenilin-2 (PSEN2), and amyloid precursor protein (APP) genes have been commonly identified in early-onset Alzheimer's disease (EOAD). Some of the mutations in the three causative genes, especially the PSEN1 gene, result in variable phenotypes and exhibit clinical heterogeneity among EOAD families.

Methods

Using next-generation sequencing (NGS), we performed genetic screening in a Chinese cohort of 18 patients with EOAD, consisting of five familial EOAD and 13 sporadic cases.

Results

We identified two likely pathogenic PSEN1 mutations (one novel) and a novel APP mutation in three cases of EOAD, where two are familial and one is sporadic, respectively. In addition, we detected a few variants of uncertain significance (VUS) in several genes, including not only the two known variants in PSEN2 (p.H169N and p.V214L) but also genes causal of other types of dementia or previously identified as risk factors for AD, suggesting the possible involvement of multiple genes in the etiopathology of AD. The patients carrying PSEN1 mutations had an earlier mean age at the onset than those with PSEN2 or APP variants. The initial symptoms varied greatly among patients in the EOAD cohort, from progressive memory impairment and epilepsy to uncommon motor symptoms such as involuntary tremors in the upper extremities.

Conclusions

In conclusion, our study provides further evidence of the genetic profile of patients with EOAD from China and expands the mutation spectrum of both PSEN1 and APP. In addition, our results highlight the clinical heterogeneity in patients with EOAD and mutations in PSEN1, PSEN2, and APP and suggest strong effects of genetic variants on clinical phenotypes. Future functional studies are needed to clarify the interaction between AD-causative gene mutations and phenotypic heterogeneity.

Pathogenicity classification of SOD1 variants of uncertain significance by in vitro aggregation propensity

Deposition of insoluble SOD1 aggregates in motor neurons is the hallmark of SOD1-associated ALS. Mutant SOD1 protein promotes structural instability that leads to misfolded SOD1 protein aggregates, which can be recapitulated in vitro. Therefore, aggregation propensity in cell lines can be a reliable indicator for the pathogenicity classification of SOD1 variants. Herein, we performed in vitro experiment to classify the pathogenicity of 34 SOD1 variants of uncertain significance (VUS) from 215 variants reported previously. The clinical features of 234 ALS patients with 31 SOD1 likely pathogenic (LP) variants were summarized. 31 VUS variants formed aggregates spontaneously, indicating LP variants. Missense variants were mainly located in the C-terminal of SOD1. Among patients with 31 SOD1 LP variants, 75% of patients had lower limb onset. The onset of familial ALS patients (45.7±14.0 years) is earlier than sporadic ALS patients (50.6±13.1 years). Our results expand the spectrum of SOD1 mutations and highlight the natural history of SOD1-positive ALS patients for further clinical trials in SOD1-related ALS.

Genetic and clinical characteristics of ALS patients with NEK1 gene variants

NIMA-related kinase 1(NEK1) gene was related to amyotrophic lateral sclerosis (ALS). However, genetic spectrum and clinical characteristics of ALS patients with NEK1 variants was largely unknown. We conducted genetic analysis on 1587 Chinese ALS patients and used software to predict the pathogenicity of NEK1 missense variant. We searched the literatures in PubMed, Embase, and Web of Science. In our ALS cohort, 42 ALS patients (2.6%) carried NEK1 variants, including 10 novel loss-of-function (LoF) variant carriers and 32 missense variant carriers. 90% of the NEK1 LoF variant carriers had upper limbs onset. The median survival time of LoF variant carriers tend to be shorter than that of probably pathogenic variant carriers (23.80 vs. 42.77 months). In 16 related studies, 167 different NEK1 variants, including 62 LoF and 105 missense variants, were found in 237 reported ALS patients. It was found that the survival time of LoF variant carriers was significantly shorter than that of missense variant carriers. Our study expanded the genotype and phenotype spectrum of ALS patients with NEK1 variants.

Clinical feature difference between juvenile amyotrophic lateral sclerosis with SPTLC1 and FUS mutations

BACKGROUND

Juvenile amyotrophic lateral sclerosis (JALS) is an uncommon form of amyotrophic lateral sclerosis whose age at onset (AAO) is defined as prior to 25 years. FUS mutations are the most common cause of JALS. SPTLC1 was recently identified as a disease-causative gene for JALS, which has rarely been reported in Asian populations. Little is known regarding the difference in clinical features between JALS patients carrying FUS and SPTLC1 mutations. This study aimed to screen mutations in JALS patients and to compare the clinical features between JALS patients with FUS and SPTLC1 mutations.

METHODS

Sixteen JALS patients were enrolled, including three newly recruited patients between July 2015 and August 2018 from the Second Affiliated Hospital, Zhejiang University School of Medicine. Mutations were screened by whole-exome sequencing. In addition, clinical features such as AAO, onset site and disease duration were extracted and compared between JALS patients carrying FUS and SPTLC1 mutations through a literature review.

RESULTS

A novel and de novo SPTLC1 mutation (c.58G>A, p.A20T) was identified in a sporadic patient. Among 16 JALS patients, 7/16 carried FUS mutations and 5/16 carried respective SPTLC1 , SETX , NEFH , DCTN1 , and TARDBP mutations. Compared with FUS mutation patients, those with SPTLC1 mutations had an earlier AAO (7.9 ± 4.6 years vs. 18.1 ± 3.9 years, P  < 0.01), much longer disease duration (512.0 [416.7-607.3] months vs. 33.4 [21.6-45.1] months, P  < 0.01), and no onset of bulbar.

CONCLUSION

Our findings expand the genetic and phenotypic spectrum of JALS and help to better understand the genotype-phenotype correlation of JALS.

Two novel heterozygote mutations of ATM in a Chinese family with dystonia-dominant ataxia telangiectasia and literature review

Background

Ataxia-telangiectasia (A-T) is an autosomal recessive disorder with high clinical heterogeneity. A-T may present in complicated variable forms, including classic A-T and milder form of AT. Contrary to the classic A-T, the milder form does not present the cardinal features of A-T such as ataxia and telangiectasia. A few ATM mutations have been reported in variant A-T cases manifesting isolated generalized or segmental dystonia without any signs of classical A-T.

Methods

An A-T pedigree with predominant dystonia was collected. Genetic testing was performed by targeted panel of genes involved in movement disorders. The candidate variants were further confirmed by Sanger sequencing. We then reviewed previously published literatures of genetically confirmed A-T cases with predominant dystonia and summarized the clinical characteristics of dystonia-dominant A-T.

Results

Two novel ATM mutations, p.I2683T and p.S2860P, were identified in the family. The proband presented isolated segmental dystonia without any signs of ataxia and telangiectasias. We reviewed the literatures and found that the patients with dystonia-dominant A-T tend to have a later-onset and slower progression of the disease.

Conclusion

To our knowledge, this is the first report of A-T patient with predominant dystonia in China. Dystonia may appear as one of the predominant manifestations or initial symptom of A-T. Early ATM genetic testing should be considered for those patients with predominant dystonia, despite without accompanying ataxia or telangiectasia.

Clinical and genetic study of a Chinese family affected by both amyotrophic lateral sclerosis and autosomal dominant polycystic kidney disease

Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disorder characterized by loss of the upper and lower motor neurons from the motor cortex, brainstem, and spinal cord. Most ALS cases are sporadic, with 5–10% having a positive family history. Autosomal dominant polycystic kidney disease (ADPKD) is a heritable renal disease that eventually results in end-stage kidney disease. PKD1 is the most prevalent causative gene for ADPKD, accounting for ~85% of cases. Both diseases are currently considered untreatable. In this study, we report a large family that includes 10 patients with ALS phenotype, 3 asymptomatic SOD1-H47R carriers, and 6 with the ADPKD phenotype. Using whole exome sequencing, we found a novel likely pathogenic variant (p.R2787P) in PKD1 among patients with ADPKD, and a pathogenic variant (p.H47R) in SOD1 among patients with ALS. This study highlights the possibility that two different autosomal dominantly inherited diseases can co-exist independently within the same family. Phenotype—genotype correlations among these patients are also described. This research contributes novel phenotype and genotype characteristics of ALS with SOD1 mutations and ADPKD with PKD1 mutations.

Novel mutations in GJB1 trigger intracellular aggregation and stress granule formation in X-linked Charcot-Marie-Tooth Disease

X-linked Charcot-Marie-Tooth Disease type 1(CMT1X) is the second most common form of inherited peripheral neuropathy that is caused by mutations in the gap junction beta-1 (GJB1) gene. Using targeted exome-sequencing, we investigated four CMT families from central-southern China and identified two novel missense variants (p.F31S and p.W44G) and two previously reported variants (p.R220Pfs*23 and p.R164Q) of GJB1. All four probands presented typical early-onset peripheral neuropathy, of which the R220Pfs*23 carrier also had neurologic manifestations in the central nervous system. We then constructed GJB1 expression vectors and performed cell biological analysis in vitro. Expression of FLAG-tagged GJB1 at various time points after transfection revealed evident protein aggregation with both wild-type and mutant forms, indicated with immunostaining and immunoblotting. Detergent-based sequential fractionation confirmed that all mutants were higher expressed and more prone to aggregate than the wild-type, whereas the R220Pfs*23 mutant showed the greatest amount of SDS-soluble multimers and monomers among groups. Moreover, intracellular aggregation probably occurs in the endoplasmic reticulum compartment rather than the Golgi apparatus. Gap junction plaques were present in all groups and were only compromised in frameshift mutant. Further evidence reveals significant intracellular stress granule formation induced by mutated GJB1 and impaired cell viability indicative of cytotoxicity of self-aggregates. Together, our findings demonstrate novel GJB1 variants-induced cell stress and dysfunction and provide insights into understanding the pathomechanisms of GJB1-CMTX1 and other related disorders.

Functional and structural consequences of TBK1 missense variants in frontotemporal lobar degeneration and amyotrophic lateral sclerosis

Mutations in the Tank-binding kinase 1 (TBK1) gene were identified in 2015 in individuals with frontotemporal lobar degeneration (FTLD) and amyotrophic lateral sclerosis (ALS). They account for ∼3-4% of cases. To date, over 100 distinct mutations, including missense, nonsense, deletion, insertion, duplication, and splice-site mutations have been reported. While nonsense mutations are predicted to cause disease via haploinsufficiency, the mechanisms underlying disease pathogenesis with missense mutations is not fully elucidated. TBK1 is a kinase involved in neuroinflammation, which is commonly observed in these diseases. TBK1 also phosphorylates key autophagy mediators, thereby regulating proteostasis, a pathway that is dysregulated in ALS-FTLD. Recently, several groups have characterised various missense mutations with respect to their effects on the phosphorylation of known TBK1 substrates, TBK1 homodimerization, interaction with optineurin, and the regulation of autophagy and neuroinflammatory pathways. Further, the effects of either global or conditional heterozygous knock-out of Tbk1, or the heterozygous or homozygous knock-in of ALS-FTLD associated mutations, alone or when crossed with the SOD1^G93A classical ALS mouse model or a TDP-43 mouse model, have been reported. In this review we summarise the known functional effects of TBK1 missense mutations. We also present novel modelling data that predicts the structural effects of missense mutations and discuss how they correlate with the known functional effects of these mutations.

Identification of TARDBP Gly298Ser as a founder mutation for amyotrophic lateral sclerosis in Southern China

BACKGROUND

Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disease characterized by predominant impairment of upper and lower motor neurons. Over 50 TARDBP mutations have been reported in both familial (FALS) and sporadic ALS (SALS). Some mutations in TARDBP, e.g. A382T and G294V, have genetic founder effects in certain geographic regions. However, such prevalence and founder effect have not been reported in Chinese.

METHODS

Whole-exome sequencing (WES) was performed in 16 Chinese FALS patients, followed by Sanger sequencing for the TARDBP p.Gly298Ser mutation (G298S) in 798 SALS patients and 1,325 controls. Haplotype analysis using microsatellites flanking TARDBP was conducted in the G298S-carrying patients and noncarriers. The geographic distribution and phenotypic correlation of the TARDBP mutations reported worldwide were reviewed.

RESULTS

WES detected the TARDBP G298S mutation in 8 FALS patients, and Sanger sequencing found additional 8 SALS cases, but no controls, carrying this mutation. All the 16 cases came from Southern China, and 7 of these patients shared the 117-286-257-145-246-270 allele for the D1S2736-D1S1151-D1S2667-D1S489-D1S434-D1S2697 markers, which was not found in the 92 non-carrier patients (0/92) (p < 0.0001) and 65 age-matched and neurologically normal individuals (0/65) (p < 0.0001). The A382T and G298S mutations were prevalent in Europeans and Eastern Asians, respectively. Additionally, carriers for the M337V mutation are dominated by bulbar onset with a long survival, whereas those for G298S are dominated by limb onset with a short survival.

CONCLUSIONS

Some prevalent TARDBP mutations are distributed in a geographic pattern and related to clinical profiles. TARDBP G298S mutation is a founder mutation in the Southern Chinese ALS population.

Analysis of ERBB4 Variants in Amyotrophic Lateral Sclerosis Within a Chinese Cohort

ERBB4 is related to amyotrophic lateral sclerosis (ALS) in patients with a family history and is thought to cause ALS-19. We screened 448 ALS patients, including 364 sporadic ALS (sALS) and 84 familial ALS (fALS) patients with ERBB4 variants, in a Chinese cohort. In total, 12 missense variants were identified in this study. Of these, 3 (p.Arg106His, p.Gln164Pro, and p.Val212Leu) were absent from the in-house healthy control cohort and population databases and predicted to be likely pathogenic. Genetic burden analysis did not reveal an increase in damaging variants of the ERBB4 gene. We considered that most of the missense variants in ERBB4 were not pathogenic, but certain variants, such as p.Arg106His, p.Gln164Pro, and p.Val212Leu, were likely pathogenic. The phenotype of these three patients carrying ERBB4 variants revealed the typical clinical manifestations of ALS without cognitive dysfunction. We concluded that ERBB4 likely pathogenic variants account for ~0.67% of ALS patients in China. It is necessary to interpret the relationship between the disease and variants carefully for ALS patients with ERBB4 gene variants.

SOD1 in ALS: Taking Stock in Pathogenic Mechanisms and the Role of Glial and Muscle Cells

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disorder characterized by the loss of motor neurons in the brain and spinal cord. While the exact causes of ALS are still unclear, the discovery that familial cases of ALS are related to mutations in the Cu/Zn superoxide dismutase (SOD1), a key antioxidant enzyme protecting cells from the deleterious effects of superoxide radicals, suggested that alterations in SOD1 functionality and/or aberrant SOD1 aggregation strongly contribute to ALS pathogenesis. A new scenario was opened in which, thanks to the generation of SOD1 related models, different mechanisms crucial for ALS progression were identified. These include excitotoxicity, oxidative stress, mitochondrial dysfunctions, and non-cell autonomous toxicity, also implicating altered Ca2+ metabolism. While most of the literature considers motor neurons as primary target of SOD1-mediated effects, here we mainly discuss the effects of SOD1 mutations in non-neuronal cells, such as glial and skeletal muscle cells, in ALS. Attention is given to the altered redox balance and Ca2+ homeostasis, two processes that are strictly related with each other. We also provide original data obtained in primary myocytes derived from hSOD1(G93A) transgenic mice, showing perturbed expression of Ca2+ transporters that may be responsible for altered mitochondrial Ca2+ fluxes. ALS-related SOD1 mutants are also responsible for early alterations of fundamental biological processes in skeletal myocytes that may impinge on skeletal muscle functions and the cross-talk between muscle cells and motor neurons during disease progression.

Genotype-phenotype association of TARDBP mutations in Chinese patients with amyotrophic lateral sclerosis: a single-center study and systematic review of published literature

BACKGROUND

This study aims to determine the genetic and clinical features of TARDBP-mutated patients in our cohort of Chinese patients with amyotrophic lateral sclerosis (ALS) combined with data in the literature.

METHODS

We performed TARDBP mutation screening in 1258 Chinese ALS patients, including 1204 sporadic ALS (sALS) and 54 familial ALS (fALS) patients. A systematic literature review was conducted by searching TARDBP-mutated patients from China in the online databases.

RESULTS

In our cohort, the mutant frequency of TARDBP variants was 0.3% (4/1258), with two recurrent variants (p.G294V, p.G298V) and one novel variant (p.S332G) identified. Combining with data in the literature review, the TARDBP-mutant frequency in the Chinese population was 1.4% (83/5998), with 0.8% (46/5470) in sALS and 7.0% (37/528) in fALS. Most patients had limb onset (63.0%), with an average life expectancy of 4.3 years (range 0.5-13). Disease durations significantly differed (p = 0.002), with p.M337V showing the longest duration (80 months) and p.N378D showing the shortest duration (16.7 months).

CONCLUSION

Our study found that TARDBP mutation was not rare in Chinese fALS patients. Different TARDBP mutations were associated with specific features in phenotypes.

Survival analysis of clinical and genetic factors in an amyotrophic lateral sclerosis cohort from China

OBJECTIVES

To investigate the clinical and genetic factors influencing the survival of amyotrophic lateral sclerosis (ALS) patients in China.

METHODS

Patients were enrolled in the study between December 2013 and December 2018. Clinical variables were recorded upon patient diagnosis. Causative genes related to ALS were screened by whole-exome sequencing and validated by Sanger sequencing. Each patient was followed up every 3-6 months until the endpoint (death or tracheotomy) or the last connection time on 31 December 2020. Propensity score matching analysis was performed to match the genetic and non-genetic ALS patients. The Kaplan-Meier method and multivariable Cox regression were performed for survival analysis.

RESULTS

A total of 337 patients, including 32 with genetic ALS and 305 with non-genetic ALS, were enrolled in the study. Before matching, in univariate analysis, age of onset (P < 0.001), site of onset (P = 0.036), diagnostic delay (P < 0.001), ALSFRS-R score at diagnosis (P < 0.001), ΔALSFRS-R (P < 0.001), and causative mutations (P  = 0.020) were significant prognostic factors. These factors remained statistically significant after multivariate analysis. After matching, in the multivariate analysis, age of onset (P = 0.003), site of onset (P = 0.014), diagnostic delay (P = 0.007), ALSFRS-R score at diagnosis (P = 0.010), ΔALSFRS-R (P = 0.007), and causative mutations (P = 0.003) were found to be significant prognostic factors.

CONCLUSION

Both clinical factors and genetic factors influenced survival in our ALS cohort. Clarifying of the underlying mechanisms is crucial for the development of future therapies.

The G41D mutation in SOD1-related amyotrophic lateral sclerosis exhibits phenotypic heterogeneity among individuals: A case report and literature review

RATIONALE

Amyotrophic lateral sclerosis (ALS) is a progressive and fatal neurodegenerative disease. However, the misdiagnosis of ALS always occurs because of atypical clinical manifestations. Since mutations in Cu/Zn superoxide dismutase 1 (SOD1) have been implicated as causative and account for 20% of fALS cases, early genetic sequencing of suspected individuals in ALS pedigrees could be helpful.

PATIENT CONCERNS

Here we report a Chinese family spanning three generations with fALS. A heterozygous c.125G>A (p.Gly42Asp) missense mutation in exon 2 of SOD1 gene was detected in our proband as well as her 2 siblings and next generation. Phenotypic diversity was also reported among symptomatic individuals.

DIAGNOSES

Peripheral blood samples from the proband were collected and sent for polymerase chain reaction (PCR) and Sanger sequencing of the SOD1 gene at Sanvalley Diagnostics. The other 11 members in the studied family then underwent locus verification.

INTERVENTIONS

Butylphthalide, Vitamin B12, Coenzyme Q10 and mouse nerve growth factor is given to the symptomatic members.

OUTCOMES

The symptoms of our proband was not improved by treatments at a late stage. She passed away the fourth year of the disease due to respiratory failure. Two siblings of the proband were given active treatments once verified as carrier. Their symptoms are still limited to limb weakness.

LESSONS

This study suggests genetic sequencing is a powerful tool for the diagnosis of familial ALS. Phenotypic heterogeneity exists among G41D-mutated individuals, which further highlights the importance of genomic strategies for early diagnosis.

Phenotype of VCP Mutations in Chinese Amyotrophic Lateral Sclerosis Patients

Mutations in the valosin-containing protein (VCP) gene have been linked to amyotrophic lateral sclerosis (ALS) in the Caucasian populations. However, the phenotype of VCP mutations in Chinese patients with (ALS) remains unclear. Targeted next-generation sequencing covered 28 ALS-related genes including the VCP gene was undertaken to screen in a Chinese cohort of 275 sporadic ALS cases and 15 familial ALS pedigrees. An extensive literature review was performed to identify all patients with ALS carrying VCP mutations previously reported. The clinical characteristics and genetic features of ALS patients with VCP mutations were reviewed. One known p.R155C mutation in the VCP gene was detected in two siblings from a familial ALS pedigree and two sporadic individuals. In addition, the same VCP p.R155C mutation was detected in an additional patient with ALS referred in 2021. Three patients with VCP p.R155C mutation presented with muscular weakness starting from proximal extremities to distal extremities. The other patient developed a phenotype of Paget's disease of bone in addition to the progressive muscular atrophy. We reported the first VCP mutation carrier manifesting ALS with Paget's disease of bone in the Chinese population. Our findings expand the phenotypic spectrum of the VCP mutations in Chinese patients with ALS and suggest that ALS patients with VCP p.R155C mutations tend to present with relatively young onset, symmetrical involvement of proximal muscles weakness of arms or legs, and then progressed to distal muscles of limbs.

SOD1 Mutation Spectrum and Natural History of ALS Patients in a 15-Year Cohort in Southeastern China

Background: Mutations in superoxide dismutase 1 gene (SOD1) are the most frequent high penetrant genetic cause for amyotrophic lateral sclerosis (ALS) in the Chinese population. A detailed natural history of SOD1-mutated ALS patients will provide key information for ongoing genetic clinical trials.

Methods: We screened for SOD1 mutations using whole exome sequencing (WES) in Chinese ALS cases from 2017 to 2021. Functional studies were then performed to confirm the pathogenicity of novel variants. In addition, we enrolled previously reported SOD1 mutations in our centers from 2007 to 2017. The SOD1 mutation spectrum, age at onset (AAO), diagnostic delay, and survival duration were analyzed.

Results: We found two novel SOD1 variants (p.G17H and p.E134*) that exerted both gain-of-function and loss-of-function effects in vitro. Combined with our previous SOD1-mutated patients, 32 probands with 21 SOD1 mutations were included with the four most frequently occurring mutations of p.V48A, p.H47R, p.C112Y, and p.G148D. SOD1 mutations account for 58.9% of familial ALS (FALS) cases. The mean (SD) AAO was 46 ± 11.4 years with a significant difference between patients carrying mutations in exon 1 [n = 5, 34.6 (12.4) years] and exon 2 [n = 8, 51.4 (8.2) years] (p = 0.038). The mean of the diagnostic delay of FALS patients is significantly earlier than the sporadic ALS (SALS) patients [9.5 (4.8) vs. 20.3 (9.3) years, p = 0.0026]. In addition, male patients survived longer than female patients (40 vs. 16 months, p = 0.05).

Conclusion: Our results expanded the spectrum of SOD1 mutations, highlighted the mutation distribution, and summarized the natural history of SOD1-mutated patients in southeastern China. Male patients were found to have better survival, and FALS patients received an earlier diagnosis. Our findings assist in providing a detailed clinical picture, which is important for ongoing genetic clinical trials.

FTD-PSP is an Unusual Clinical Phenotype in A Frontotemporal Dementia Patient with A Novel Progranulin Mutation

Progranulin (GRN) mutations are a major cause of frontotemporal dementia (FTD); the spectrum of clinical phenotypes of FTD is much more extensive than previously reported. The frequency and locations of GRN mutations in Chinese patients with FTD remain uncertain. We performed cDNA sequencing in one sporadic male patient who initially presented FTD symptoms. Brain magnetic resonance imaging (MRI) and positron emission computed tomography/computed tomography (PET/CT) were applied to further confirm the diagnosis of FTD from this patient. Cellular apoptosis and survival test were performed to identify the function of GRN. We identified one novel missense GRN mutation (c.1498G>A, p.V500I) in this patient, who initially presented typical behavioral-variant frontotemporal dementia (bvFTD) features but then presented progressive supranuclear palsy (PSP) clinical characteristics 5 years after onset. Besides, WT GRN protein showed an adequate trophic stimulus to preserve the survival of SH-SY5Y cells in the medium free of serum, while GRN mutation (c.1498G>A, p.V500I) may impair the ability of supporting cell survival. This study owns significant implications for genetic counseling and clinical heterogeneity. We illustrate the fact that FTD presenting features of bvFTD and PSP in one patient could be considered as a specific phenotype in patients with GRN mutations. GRN p.V500I led to the neuronal degeneration in vitro; this finding provides a significant evidence that this mutation may be a new causative mutation in patients with FTD.

An identical DCTN1 mutation in two Chinese siblings manifest as dHMN and ALS respectively: a case report

Mutations in the DCTN1 gene have been found in patients with various neurodegenerative diseases, and the spectrum is still expanding. Here, we report a mutation in DCTN1 (c.175G > C, p.G59R) identified in two patients, who manifested dHMN and ALS, respectively, in an affected family. The clinical manifestations and eightyear follow-up suggested that this mutation is pathogenic. The phenomena observed in this family with the same DCTN1 mutation illustrate the clinical heterogeneity of DCTN1 gene mutations and expand our understanding of their genotype-phenotype relationships. Further research and functional experiments, especially mutation at amino acid position 59 of DCTN1, are required.

Genetic analysis in Chinese patients with familial or young-onset amyotrophic lateral sclerosis

OBJECTIVE

The aim of our study was to investigate the genetic characteristics in patients with familial or young-onset amyotrophic lateral sclerosis (ALS) in a Chinese center.

METHODS

Patients with familial or young-onset (age of onset < 45 years old) ALS were reviewed. The clinical data was collected. Whole-exome sequencing was performed to identify the disease-associated variants. Single-nucleotide variants and small insertions/deletions were further predicted with silico tools and compared to the Single Nucleotide Polymorphism Database, Exome Aggregation Consortium, and the 1000 Genomes Project. The evolutionary conservations were estimated, and the structures of proteins were constructed by Swiss-Model server. Immunohistochemistry was used to confirm the misfolded SOD1 protein.

RESULTS

Three familial ALS and 5 young-onset ALS were enrolled. Genetic analysis identified related variants of SOD1 (4/6, 66.7%), FUS (1/6, 16.7%), and NEK1 (1/6, 16.7%) in 6 patients. Three of them were familial probands (3/3, 100%), and the others were sporadic young-onset patients (3/5, 60%). NEK1 c.290G > A mutation (NM_012224.2 exon4) in a patient with familial ALS and SOD1 c.362A > G mutation (NM_000454 exon5) in a young-onset ALS patient were novel. The novel mutations were predicted to be deleterious, affected evolutionarily highly conserved amino acid residue and the formation of hydrogen bonds between the mutated site and its surrounding amino acid residues. Misfolded SOD1 protein was identified in patient with SOD1 c.362A > G mutation.

CONCLUSIONS

Two novel mutations were detected in our patients. Patients with familial or young-onset ALS often carried related gene mutations, and genetic sequencing should be thus routinely performed.

Role of genetics in amyotrophic lateral sclerosis: a large cohort study in Chinese mainland population

Background

A large number of new causative and risk genes for amyotrophic lateral sclerosis (ALS) have been identified mostly in patients of European ancestry. In contrast, we know relatively little regarding the genetics of ALS in other ethnic populations. This study aims to provide a comprehensive analysis of the genetics of ALS in an unprecedented large cohort of Chinese mainland population and correlate with the clinical features of rare variants carriers.

Methods

A total of 1587 patients, including 64 familial ALS (FALS) and 1523 sporadic ALS (SALS), and 1866 in-house controls were analysed by whole-exome sequencing and/or testing for G4C2 repeats in C9orf72. Forty-one ALS-associated genes were analysed.

Findings

155 patients, including 26 (40.6%) FALS and 129 (8.5%) SALS, carrying rare pathogenic/likely pathogenic (P/LP) variants of ALS causative genes were identified. SOD1 was the most common mutated gene, followed by C9orf72, FUS, NEK1, TARDBP and TBK1. By burden analysis, rare variants in SOD1, FUS and TARDBP contributed to the collective risk for ALS (p<2.5e-6) at the gene level, but at the allelic level TARDBP p.Gly294Val and FUS p.Arg521Cys and p.Arg521His were the most important single variants causing ALS. Clinically, P/LP variants in TARDBP and C9orf72 were associated with poor prognosis, in FUS linked with younger age of onset, and C9orf72 repeats tended to affect cognition.

Conclusions

Our data provide essential information for understanding the genetic and clinical features of ALS in China and for optimal design of genetic testing and evaluation of disease prognosis.

Sequencing of neurofilament genes identified NEFH Ser787Arg as a novel risk variant of sporadic amyotrophic lateral sclerosis in Chinese subjects

BACKGROUND

Amyotrophic lateral sclerosis (ALS) is a devastating neurodegenerative disease with neuronal cell inclusions composed of neurofilaments and other abnormal aggregative proteins as pathological hallmarks. Approximately 90% of patients have sporadic cases (sALS), and at least 4 genes, i.e. C9orf72, SOD1, FUS and TARDBP, have been identified as the main causative genes, while many others have been proposed as potential risk genes. However, these mutations could explain only ~ 10% of sALS cases. The neurofilament polypeptides encoded by NEFH, NEFM, and NEFL are promising protein biomarkers for ALS and other degenerative diseases. However, whether the genetic variants of these genes were associated with ALS remain ambiguous.

METHODS

Here, we used PCR-Sanger to sequence the exons of these three genes in a cohort of 371 sALS patients and 711 healthy controls (Phase I) and validated the risk variant in another 300 sALS patients and 1076 controls (Phase II).

RESULTS

A total of 92 variants were identified, including 36 rare heterozygous variants in NEFH, 27 in NEFM, and 16 in NEFL, and only rs568759161 (p.Ser787Arg) in NEFH reached nominal statistical power (P = 0.02 at Phase I, P = 0.009 at Phase II) in the case-control comparison. Together, the Phase I and II studies showed the significantly higher frequency of the variant in cases (9/1342, 0.67%) than in controls (2/3574, 0.07%) (OR 12.06; 95% CI 2.60-55.88; P = 0.0003). No variants passed multiple testing in the discovery cohort, but rs568759161 was associated with ALS in a replication cohort.

CONCLUSIONS

Our results confirmed that NEFH Ser787Arg is a novel sALS risk variant in Chinese subjects, but NEFM and NEFL were not associated with sALS. These data may have implications for genetic counselling and for understanding the pathogenesis of sALS.

Genotype-phenotype correlations in a chinese population with familial amyotrophic lateral sclerosis

Objective: This study aimed to determine the distribution of the most commonly mutated genes (SOD1, TARDBP, FUS/TLS, and C9ORF72) associated with familial amyotrophic lateral sclerosis (FALS) and the association between genotype and phenotype in 242 Chinese patients.Methods: A total of 58 families were screened for ALS-associated mutations in SOD1，TARDBP, FUS, and C9ORF72 hexanucleotide repeat expansion. These mutations were analyzed to evaluate the relationship between genotype and phenotype in Chinese FALS patients.Results: Partial clinical data were obtained for 242 relatives of the 58 analyzed families, with a male-to-female ratio of 1.2:1 and a mean age of disease onset of 45.9±12.0 (13-80) years. 26 mutations associated with pathogenesis were identified in 32 probands from 58 different families. Mutations in SOD1, FUS, TARDBP, and C9ORF72 accounted for 32.8%, 12.1%, 8.6%, and 1.7% of FALS, respectively. FALS patients showed longer survival times; however, bulbar-onset ALS and the male-to-female ratio for them were lower than those reported previously. The site of onset, age of onset, and lifespan differed in FALS patients with SOD1, TARDBP, and FUS mutations.Discussion: In this study, patients with SOD1 mutations exhibited heterogeneous survival times that showed a bimodal distribution, while patients with FUS mutations showed rapid disease progression. Our results showed the relative contributions of the different types of mutations associated with ALS and provided phenotype-genotype correlations with clinical features in Chinese patients.

Genetic and clinical features of Chinese sporadic amyotrophic lateral sclerosis patients with TARDBP mutations

OBJECTIVES

To investigate the genetic and clinical features of Chinese sporadic amyotrophic lateral sclerosis (SALS) patients with TARDBP mutations, we carried out a genetic analysis in a cohort of 391 SALS patients and explored the clinical manifestations of patients with TARDBP variants.

MATERIALS AND METHODS

The coding region of all five coding exons of TARDBP, exons 2-6, were sequenced for mutations in 391 Chinese SALS patients. The clinical features of patients with TARDBP mutations were described and compared with cases in literatures.

RESULTS

Two missense mutations in TARDBP gene, c.1132A > G (p.N378D) and c.1147A > G (p.I383V), were detected in three cases, showing a low frequency (0.77%, 3/391) of TARDBP missense mutations in Chinese SALS patients. Based on a retrospective analysis of literatures, p.N378D mutation mainly presents a phenotype of early onset, whereas p.I383V mutation presents pure ALS or ALS alongside semantic variant primary progressive aphasia (svPPA), a type of frontotemporal dementia (FTD).

CONCLUSIONS

Our results demonstrate that TARDBP mutation is a rare cause of Chinese SALS patients and expand the spectrum of phenotype. It is implied that genetic analysis of SALS patients plays a crucial role in uncovering the cause of disease, especially for cases developing early onset or alongside FTD.

Mutation spectrum of amyotrophic lateral sclerosis in Central South China

To analyze the mutational spectrum of known ALS causative genes in China ALS patients. We comprehensively analyzed 51 ALS causative genes by combining different sequencing technologies in 753 unrelated ALS patients from Central South China. The mean age at onset (AAO) was 53.7±11.4 years. The AAO was earlier in the autosomal dominant (AD) ALS patients than in the sporadic ALS (sALS) patients. Bulbar onset was more frequent in females than in males. SOD1 was the most frequently mutated gene in the AD-ALS and the sALS patients, followed by the ATXN2 and FUS genes in the AD-ALS patients and the NEK1 and CACNA1H genes in the sALS patients. Patients with RDVs in the SOD1 or FUS genes had an earlier AAO than the mean AAO of all the patients, while the patients with RDVs in the NEK1 gene showed later onset. SOD1 gene was the most commonly mutated gene in ALS patients in China, followed by ATXN2 and NEK1. The phenotype might be determined synergistically by sex and genetic variants.

The investigation of genetic and clinical features in patients with hereditary spastic paraplegia in central-Southern China

Objective

Hereditary spastic paraplegias (HSP) is a clinically and genetically heterogeneous group of neurodegenerative disorders. We describe the genetic and clinical features of a cohort of five HSP families from central‐southern China.

Methods

Using targeted exome‐sequencing technology, we investigated the genetic and clinical features in five HSP families. We reviewed the clinical histories of these patients as well as the molecular and functional characterization of the associated gene variants. We also performed functional analysis of an intron variant of SPAST in vitro.

Results

We identified a known SPAST mutation (p.Pro435Leu) in a family with autosomal dominant HSP (AD‐HSP) and four novel variants in two HSP families and a sporadic case. These identified four novel variants included a variant in SPG11 (p.Val1979Ter), two variants in B4GALNT1 (p.Ser475Phe and c.1002 + 2 T > G), and a splicing site variant in SPAST (c.1245+5G>A). Minigene analysis of the splicing variant in SPAST (c.1245+5G>A) revealed that the mutation resulted in mRNAs with a loss of exon 9. The SPG4 family carrying c.1245+5G>A variant in SPAST exhibited genetic anticipation, with a decreased age at onset and increased severity in successive generations. The proband with p.Val1979Ter variant in SPG11 showed characteristic clinical features of early‐onset, severe spasticity, and corpus callosum atrophy which were highly suggestive of the diagnosis of SPG11‐associated HSP.

Conclusions

Our findings strongly support variable phenotype of B4GALNT1‐related SPG26 and also expand the clinical and mutation spectrum of HSP caused by mutations in SPAST, SPG11, and B4GALNT1. These results will help to improve the efficiency of early diagnosis in patients clinically suspected of HSP.

We investigated the genetic and clinical features in five families with HSP from central‐southern China using targeted exome‐sequencing technology. We identified a known mutation (p.Pro435Leu) in SPAST in a family with autosomal dominant HSP (AD‐HSP) and four novel variants in three independent HSP families and a sporadic case. These identified four novel variants include a nonsense variant (p.Val1979Ter) in SPG11, two variants (p.Ser475Phe and c.1002 + 2 T > G) in B4GALNT1, and a splicing site variants in SPAST (c.1245 + 5G>A). Minigene analysis of the splicing variant (c.1245 + 5G>A) in SPAST revealed that the mutation resulted in mRNAs with a loss of exon 9

Novel variants and cellular studies on patients' primary fibroblasts support a role for NEK1 missense variants in ALS pathogenesis

In the last few years, NEK1 has been identified as a new gene related to amyotrophic lateral sclerosis (ALS). Loss-of-function variants have been mostly described, although several missense variants exist, which pathogenic relevance remains to be established. We attempted to determine the contribution of NEK1 gene in an Italian cohort of 531 sporadic and familial amyotrophic lateral sclerosis (ALS) patients applying massive parallel sequencing technologies. We filtered results of NEK1 gene and identified 20 NEK1 rare variants (MAF < 0.01) in 22 patients. In particular, we found two novel frameshift variants (p.Glu929Asnfs*12 and p.Val1030Ilefs*23), 18 missense variants, including the p.Arg261His in three patients, and a novel variant in the start codon, the p.Met1?, which most likely impairs translation initiation. To clarify the role of NEK1 missense variants we investigated NEK1 expression in primary fibroblast cultures. We obtained skin biopsies from four patients with NEK1 variants and we assessed NEK1 expression by western blot and immunofluorescence. We detected a decrease in NEK1 expression in fibroblasts from patients with NEK1 variants, suggesting that missense variants in NEK1 gene may have a pathogenic role. Moreover, we observed additional variants in ALS related genes in seven patients with NEK1 variants (32%), further supporting an oligogenic ALS model.

Promoting identification of amyotrophic lateral sclerosis based on label-free plasma spectroscopy

Objective

Amyotrophic lateral sclerosis (ALS) is an adult‐onset fatal neurodegenerative disease which lacks identified biological markers. A label‐free plasma surface‐enhanced Raman spectroscopy (SERS) method was developed to explore a simple and noninvasive test for ALS.

Methods

ALS patients were enrolled serially and plasma samples were collected at the time of diagnosis prior to the start of ALS treatment. SERS spectra were recorded using a Renishaw micro‐Raman system.

Results

To exclude the interference by varying disease severity, we enrolled three groups of ALS patients, including ALS‐1 (n = 60; ALSFRS‐R ≥ 42 and time interval ≤ 12 months), ALS‐2 (n = 61; ALSFRS‐R < 42 and time interval ≤ 12 months), and ALS‐3 (n = 61; ALSFRS‐R ≥ 38 and time interval> 12 months). The SERS spectra were analyzed using principal component analysis (PCA), which showed that ALS‐1, ALS‐2, ALS‐3, and control groups were separated significantly. Then, decision tree (DT) models and receiver operating characteristic curves were employed and identified that bands at 722 and 739 cm⁻¹, and ratios of 635–722 cm⁻¹ and 635–739 cm⁻¹ were able to distinguish ALS from controls significantly. Finally, we highlighted six metabolism pathways correlated with ALS, including phenylalanine‐tyrosine‐tryptophan biosynthesis, aminoacyl‐tRNA biosynthesis, phenylalanine metabolism, pantothenate and CoA biosynthesis, porphyrin and chlorophyll metabolism, and pyrimidine metabolism.

Interpretation:

Plasma SERS could be a promising tool for the detection of ALS. The bands at 722 and 739 cm⁻¹, and the ratios of 635–722 cm⁻¹ and 635–739 cm⁻¹ could serve as potential indicator for ALS.

A Systematic Review of Genotype-Phenotype Correlation across Cohorts Having Causal Mutations of Different Genes in ALS

Amyotrophic lateral sclerosis is a rare and fatal neurodegenerative disease characterised by progressive deterioration of upper and lower motor neurons that eventually culminates in severe muscle atrophy, respiratory failure and death. There is a concerning lack of understanding regarding the mechanisms that lead to the onset of ALS and as a result there are no reliable biomarkers that aid in the early detection of the disease nor is there an effective treatment. This review first considers the clinical phenotypes associated with ALS, and discusses the broad categorisation of ALS and ALS-mimic diseases into upper and lower motor neuron diseases, before focusing on the genetic aetiology of ALS and considering the potential relationship of mutations of different genes to variations in phenotype. For this purpose, a systematic review is conducted collating data from 107 original published clinical studies on monogenic forms of the disease, surveying the age and site of onset, disease duration and motor neuron involvement. The collected data highlight the complexity of the disease's genotype-phenotype relationship, and thus the need for a nuanced approach to the development of clinical assays and therapeutics.