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.

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.

An Atypical Presentation of Upper Motor Neuron Predominant Juvenile Amyotrophic Lateral Sclerosis Associated with TARDBP Gene: A Case Report and Review of the Literature

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease that can rarely affect young individuals. Juvenile ALS (JALS) is defined for individuals with an onset of the disease before the age of 25. The contribution of genetics to ALS pathology is a field of growing interest. One of the differences between adult-onset ALS and JALS is their genetic background, with a higher contribution of genetic causes in JALS. We report a patient with JALS and a pathogenic variant in the TARDBP gene (c.1035C > G; p.Asn345Lys), previously reported only in adult-onset ALS, and with an atypical phenotype of marked upper motor neuron predominance. In addition, the proband presented an additional variant in the NEK1 gene, c.2961C > G (p.Phe987Leu), which is classified as a variant of unknown significance. Segregation studies showed a paternal origin of the TARDBP variant, while the variant in NEK1 was inherited from the mother. We hypothesize that the NEK1 variant acts as a disease modifier and suggests the possibility of a functional interaction between both genes in our case. This hypothesis could explain the peculiarities of the phenotype, penetrance, and the age of onset. This report highlights the heterogeneity of the phenotypic presentation of ALS associated with diverse pathogenic genetic variants.

A rare case of juvenile amyotrophic lateral sclerosis

BACKGROUND

Amyotrophic lateral sclerosis (ALS) is a chronic motor neuron disease characterised by progressive weakness in striated muscles resulting from the destruction of neuronal cells. The term juvenile ALS (JALS) is used for patients whose symptoms start before 25 years of age. JALS may be sporadic or familial.

CASE

Here, we present a sporadic case of JALS because of its rarity in children. The heterozygous p.Pro525Leu (c.1574C > T) variation was identified in the fused in sarcoma (FUS) gene.

CONCLUSION

The p.Pro525Leu mutation in the FUS gene has been detected in patients with ALS, characterised by early onset and a severely progressive course.

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.

The ALS-related σ1R E102Q Mutant Eludes Ligand Control and Exhibits Anomalous Response to Calcium

Sigma receptor type 1 (σ1R) is a transmembrane protein expressed throughout the central nervous system and in certain peripheral tissues. The human σ1R E102Q mutation causes juvenile amyotrophic lateral sclerosis (ALS), likely by inducing a series of alterations in calcium efflux from the endoplasmic reticulum (ER) to mitochondria that affects calcium homeostasis and cellular survival. Here, we report the influence of calcium on σ1R E102Q associations with glutamate N-methyl-D-aspartate receptors (NMDARs), binding immunoglobulin protein (BiP), and transient receptor potential calcium channels A1, V1, and M8. The mutant protein inhibited the binding of calmodulin to these calcium channels and interacted less with BiP than wild-type σ1R, thereby contributing to calcium homeostasis dysfunction. Mutant σ1R, but not wild-type σ1R, strongly bound to histidine triad nucleotide binding protein 1, which regulates neuromuscular synaptic organization and target selection through teneurin 1. While ligands regulated the association of σ1R wild-type with NMDARs and BiP, they failed to modulate the interaction between these proteins and the σ1R E102Q mutant. Thus, the σ1R E102Q mutant exhibited an anomalous response to cytosolic calcium levels, altered affinity for target proteins, and a loss of response to regulatory ligands. We believe that these modifications may contribute to the onset of juvenile ALS.

Description of combined ARHSP/JALS phenotype in some patients with SPG11 mutations

Background

SPG11 mutations can cause autosomal recessive hereditary spastic paraplegia (ARHSP) and juvenile amyotrophic lateral sclerosis (JALS). Because these diseases share some clinical presentations and both can be caused by SPG11 mutations, it was considered that definitive diagnosis may not be straight forward.

Methods

The DNAs of referred ARHSP and JALS patients were exome sequenced. Clinical data of patients with SPG11 mutations were gathered by interviews and neurological examinations including electrodiagnosis (EDX) and magnetic resonance imaging (MRI).

Results

Eight probands with SPG11 mutations were identified. Two mutations are novel. Among seven Iranian probands, six carried the p.Glu1026Argfs*4‐causing mutation. All eight patients had features known to be present in both ARHSP and JALS. Additionally and surprisingly, presence of both thin corpus callosum (TCC) on MRI and motor neuronopathy were also observed in seven patients. These presentations are, respectively, key suggestive features of ARHSP and JALS.

Conclusion

We suggest that rather than ARHSP or JALS, combined ARHSP/JALS is the appropriate description of seven patients studied. Criteria for ARHSP, JALS, and combined ARHSP/JALS designations among patients with SPG11 mutations are suggested. The importance of performing both EDX and MRI is emphasized. Initial screening for p.Glu1026Argfs*4 may facilitate SPG11 screenings in Iranian patients.

A novel SETX gene mutation associated with Juvenile amyotrophic lateral sclerosis

OBJECTS

This study aimed to report a novel point mutation associated with juvenile amyotrophic lateral sclerosis (JALS) in a Chinese Han family.

METHODS

Detailed clinical assessment was applied to two patients, including proband (II-2) and his mother (I-2). Next-generation sequencing (NGS), also known as high-throughput sequencing in whole exon sequence, was performed in the proband to reach the target region. Sanger sequencing was also used to detect DNA sequence variants of the proband and other three members of his family.

RESULTS

The proband (II-2) and his mother (I-2) were successfully diagnosed according to the clinical manifestations and physical examination. A novel point mutation c.1157T > C in the exon 10 of the SETX gene was identified in II-2 and I-2, resulting in a substitution of methionine (ATG) to threonine (ACG). However, we ultimately did not find the same variant in the other two normal members of his family in addition to 100 unrelated normal subjects.

CONCLUSION

We presented a novel probably pathogenic missense mutation in exon 10 of SETX gene in a Chinese Han family with JALS.

The investigation of genetic and clinical features in Chinese patients with juvenile amyotrophic lateral sclerosis

Juvenile amyotrophic lateral sclerosis (JALS) occurs at an age of onset below 25 years with a heterogeneous disease onset location, variable progression and survival time. To investigate whether an ALS gene profile could resolve any aspects of clinical symptom heterogeneity, we have used targeted sequencing technology in a cohort of 12 JALS patients of Chinese descent. We detected 5 likely pathogenic mutations, 2 in familial probands and 3 in sporadic patients. One was a known TARDBP mutation (p.G348V) and 4 were FUS frameshift mutations including a known p.Gln519Ilefs*9 mutation and 3 novel mutations, p.Gly515Valfs*14, p.Gly486Profs*30, and p.Arg498Alafs*32. Of the 4 FUS mutations, 2 were able to be confirmed as de novo mutations. The TARDBP mutation carrier showed a classic ALS phenotype. All patients with FUS mutations experienced limb weakness at an early age and developed bulbar symptoms during the disease course. FUS mutations have previously been associated with increased JALS disease progression, however, we found a large range 12 to 84 months in disease survival (mean 58.2 months). Our results justify future screening for variants in FUS as it remains the most frequent genetic determinant of early onset, JALS (found in 30% of our patients).

Juvenile amyotrophic lateral sclerosis: Classical wine glass sign on magnetic resonance imaging

Amyotrophic lateral sclerosis (ALS), also known as Lou Gehrig disease, is a chronic degenerative neurologic disease and is characterized by the selective involvement of the motor system. Usually, patients present with upper motor neuron (UMN) and lower motor neuron compromise. Degeneration of the UMN in the cerebral cortex is one of the main pathologic changes in ALS. These changes usually affect corticospinal tracts leading to degeneration of the fibers which show characteristic hyperintensities along the tracts leading to the “wine glass sign.” Patients with ALS usually present in the sixth decade of life; presentation in pediatric age in the form of juvenile ALS being rare.