A de novo c.1509dupA:p.R503fs mutation of FUS: report of a girl with sporadic juvenile amyotrophic lateral sclerosis

Modeling sporadic juvenile ALS in iPSC-derived motor neurons explores the pathogenesis of FUSR503fs mutation

Introduction

Fused in sarcoma (FUS) mutations represent the most common genetic etiology of juvenile amyotrophic lateral sclerosis (JALS), for which effective treatments are lacking. In a prior report, we identified a novel FUS mutation, c.1509dupA: p. R503fs (FUSR503fs), in a sporadic JALS patient.

Methods

The physicochemical properties and structure of FUSR503fs protein were analyzed by software: Multi-electrode array (MEA) assay, calcium activity imaging assay and transcriptome analysis were used to explore the pathophysiological mechanism of iPSC derived motor neurons.

Results

Structural analysis and predictions regarding physical and chemical properties of this mutation suggest that the reduction of phosphorylation and glycosylation sites, along with alterations in the amino acid sequence, may contribute to abnormal FUS accumulation within the cytoplasm and nucleus of induced pluripotent stem cell- derived motor neurons (MNs). Multi-electrode array and calcium activity imaging indicate diminished spontaneous electrical and calcium activity signals in MNs harboring the FUSR503fs mutation. Transcriptomic analysis reveals upregulation of genes associated with viral infection and downregulation of genes involved in neural function maintenance, such as the ATP6V1C2 gene. Treatment with ropinirole marginally mitigates the electrophysiological decline in FUSR503fs MNs, suggesting the utility of this cell model for mechanistic exploration and drug screening.

Discussion

iPSCs-derived motor neurons from JALS patients are promising tools for drug screening. The pathological changes in motor neurons of FUSR503fs may occur earlier than in other known mutation types that have been reported.

FUS gene mutation in amyotrophic lateral sclerosis: a new case report and systematic review

OBJECTIVE

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease associated with upper and lower motor neuron degeneration and necrosis, characterized by progressive muscle weakness, atrophy, and paralysis. The FUS mutation-associated ALS has been classified as ALS6. We reported a case of ALS6 with de novo mutation and investigated retrospectively the characteristics of cases with FUS mutation.

METHODS

We reported a male patient with a new heterozygous variant of the FUS gene and comprehensively reviewed 173 ALS cases with FUS mutation. The literature was reviewed from the PubMed MEDLINE electronic database (https://www.ncbi.nlm.nih.gov/pubmed) using "Amyotrophic Lateral Sclerosis and Fus mutation" or "Fus mutation" as key words from 1 January 2009 to 1 January 2022.

RESULTS

We report a case of ALS6 with a new mutation point (c.1225-1227delGGA) and comprehensively review 173 ALS cases with FUS mutation. Though ALS6 is all with FUS mutation, it is still a highly heterogenous subtype. The average onset age of ALS6 is 35.2 ± 1.3 years, which is much lower than the average onset age of ALS (60 years old). Juvenile FUS mutations have an aggressive progression of disease, with an average time from onset to death or tracheostomy of 18.2 ± 0.5 months. FUS gene has the characteristics of early onset, faster progress, and shorter survival, especially in deletion mutation p.G504Wfs *12 and missense mutation of p.P525L.

CONCLUSIONS

ALS6 is a highly heterogenous subtype. Our study could allow clinicians to better understand the non-ALS typical symptoms, phenotypes, and pathophysiology of ALS6.

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.

A de novo c.113 T > C: p.L38R mutation of SPTLC1: case report of a girl with sporadic juvenile amyotrophic lateral sclerosis

SPTLC1 has been implicated in hereditary sensory and autonomic neuropathy type 1 (HSAN1) and macular telangiectasia type2. Recent studies have reported mutations in SPLTC1 may cause juvenile amyotrophic lateral sclerosis (JALS), especially in the first transmembrane domain of SPTLC1(exon 2). In this study, we identified a novel heterozygous variant in exon 2, c.113 T > C: p. Leu38Arg, of SPTLC1 in a 12-year-old girl with sporadic JALS who experienced early-childhood-onset lower extremity spasticity followed by slowly progressive lower motor weakness and atrophy without sensory symptoms or signs. SPLTC1 is the first monogenic lipid metabolic disturbance that has been linked to ALS. The variant in exon 2 may impact on negative regulation of sphingolipid biosynthesis.

FUS mutations in Asian amyotrophic lateral sclerosis patients: a case report and literature review of genotype-phenotype correlations

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease characterized by progressive weakness and muscular atrophy in the upper or lower limbs, ultimately leading to paralysis and death. Genetic studies have demonstrated that mutation in the gene encoding fused in sarcoma (FUS) is an uncommon cause of ALS. Here, we report a case of a 31-year-old Asian man with ALS with rare onset of dropped-head syndrome. Symptoms, including asymmetric proximal weakness of the upper limbs, hoarseness, dysphagia, and nocturnal dyspnea, emerged over a period of 5 months. After genetic testing, the patient was confirmed to harbor a novel pathogenic heterozygous mutation, c.1558C > T (p.R520C). We summarize the genotype-clinical phenotype relationships in 42 Asian patients with ALS-FUS.

Juvenile Amyotrophic Lateral Sclerosis: A Review

Juvenile amyotrophic lateral sclerosis (JALS) is a rare group of motor neuron disorders with gene association in 40% of cases. JALS is defined as onset before age 25. We conducted a literature review of JALS and gene mutations associated with JALS. Results of the literature review show that the most common gene mutations associated with JALS are FUS, SETX, and ALS2. In familial cases, the gene mutations are mostly inherited in an autosomal recessive pattern and mutations in SETX are inherited in an autosomal dominant fashion. Disease prognosis varies from rapidly progressive to an indolent course. Distinct clinical features may emerge with specific gene mutations in addition to the clinical finding of combined upper and lower motor neuron degeneration. In conclusion, patients presenting with combined upper and lower motor neuron disorders before age 25 should be carefully examined for genetic mutations. Hereditary patterns and coexisting features may be useful in determining prognosis.

A case of juvenile-onset amyotrophic lateral sclerosis with a de novo frameshift FUS gene mutation presenting with bilateral abducens palsy

Fused in sarcoma (FUS) is the most common causative gene in juvenile-onset amyotrophic lateral sclerosis (jALS). We presented a case of a 15-year-old Chinese girl with atypical and extremely rare bilateral abducens palsy was caused by a heterozygous c.1520del (p.Gly507Alafs*22) pathogenic frameshift mutation in the FUS gene revealed by whole-exome sequencing. This is the first jALS case presenting with bilateral abducens palsy and carrying de novo FUS genetic variant.

Sensitivity of Awaji Criteria and Revised El Escorial Criteria in the Diagnosis of Amyotrophic Lateral Sclerosis (ALS) at First Visit in a Tunisian Cohort

Background

Amyotrophic lateral sclerosis (ALS) is a fatal disease whose diagnosis and early management can improve survival. The most used diagnostic criteria are the revised El Escorial criteria (rEEC) and Awaji criteria (AC). The comparison of their sensitivities showed contradictory results. Our study aimed to compare the sensitivities of these two criteria in the diagnosis of definite ALS, at first visit, in a Tunisian hospital cohort.

Materials and Methods

This was a retrospective study including 173 patients diagnosed with ALS at the Department of Neurology of the Razi Hospital between January 2003 and April 2018.After studying the clinical features of the disease in our study population,each patient was categorized according to the rEEC and AC based on data collected in his medical record during his first visit to our department. Then, we compared the sensitivities of these two criteria in the diagnosis of definite ALS.

Results

Our Tunisian cohort was characterized by a slower disease progression. The sensitivity of the AC (69.4%) was significantly higher than that of the rEEC (40.5%) (p < 0.001). When the clinical signs evolved for less than 6 months, the sensitivities were 61% for AC and 12% for rEEC (p < 0.001). After 24 months of disease progression, the sensitivities were 78.2% for AC and 69.1% for rEEC (p = 0.063). It was impossible to categorize seventeen patients by the two criteria.

Conclusion

Our study demonstrated that patients in AC are more sensitive than rEEC in the early diagnosis of ALS in our Tunisian cohort. However, this superiority is gradually reduced during the evolution of the disease.

A Human iPSC Line Carrying a de novo Pathogenic FUS Mutation Identified in a Patient With Juvenile ALS Differentiated Into Motor Neurons With Pathological Characteristics

Human-induced pluripotent stem cells (hiPSCs) are used to establish patient-specific cell lines and are ideal models to mirror the pathological features of diseases and investigate their underlying mechanisms in vitro, especially for rare genic diseases. Here, a de novo mutation c.1509dupA (p.R503fs) in fused in sarcoma (FUS) was detected in a patient with sporadic juvenile amyotrophic lateral sclerosis (JALS). JALS is a rare and severe form of ALS with unclear pathogenesis and no effective cure. An induced pluripotent stem cell (iPSC) line carrying the de novo mutation was established, and it represents a good tool to study JALS pathogenesis and gene therapy strategies for the treatment of this condition. The established human iPSC line carrying the de novoFUS mutation strongly expressed pluripotency markers and could be differentiated into three embryonic germ layers with no gross chromosomal aberrations. Furthermore, the iPSCs could be successfully differentiated into motor neurons exhibiting the pathological characteristics of ALS. Our results indicate that this line may be useful for uncovering the pathogenesis of sporadic JALS and screen for drugs to treat this disorder.

High-Throughput Genetic Testing in ALS: The Challenging Path of Variant Classification Considering the ACMG Guidelines

The development of high-throughput sequencing technologies and screening of big patient cohorts with familial and sporadic amyotrophic lateral sclerosis (ALS) led to the identification of a significant number of genetic variants, which are sometimes difficult to interpret. The American College of Medical Genetics and Genomics (ACMG) provided guidelines to help molecular geneticists and pathologists to interpret variants found in laboratory testing. We assessed the application of the ACMG criteria to ALS-related variants, combining data from literature with our experience. We analyzed a cohort of 498 ALS patients using massive parallel sequencing of ALS-associated genes and identified 280 variants with a minor allele frequency < 1%. Examining all variants using the ACMG criteria, thus considering the type of variant, inheritance, familial segregation, and possible functional studies, we classified 20 variants as “pathogenic”. In conclusion, ALS’s genetic complexity, such as oligogenic inheritance, presence of genes acting as risk factors, and reduced penetrance, needs to be considered when interpreting variants. The goal of this work is to provide helpful suggestions to geneticists and clinicians dealing with ALS.