Compound Heterozygous Mutations of SACS in a Korean Cohort Study of Charcot-Marie-Tooth Disease Concurrent Cerebellar Ataxia and Spasticity.

Mutations in the SACS gene are associated with autosomal recessive spastic ataxia of Charlevoix-Saguenay disease (ARSACS) or complex clinical phenotypes of Charcot-Marie-Tooth disease (CMT). This study aimed to identify SACS mutations in a Korean CMT cohort with cerebellar ataxia and spasticity by whole exome sequencing (WES). As a result, eight pathogenic SACS mutations in four families were identified as the underlying causes of these complex phenotypes. The prevalence of CMT families with SACS mutations was determined to be 0.3%. All the patients showed sensory, motor, and gait disturbances with increased deep tendon reflexes. Lower limb magnetic resonance imaging (MRI) was performed in four patients and all had fatty replacements. Of note, they all had similar fatty infiltrations between the proximal and distal lower limb muscles, different from the neuromuscular imaging feature in most CMT patients without SACS mutations who had distal dominant fatty involvement. Therefore, these findings were considered a characteristic feature in CMT patients with SACS mutations. Although further studies with more cases are needed, our results highlight lower extremity MRI findings in CMT patients with SACS mutations and broaden the clinical spectrum. We suggest screening for SACS in recessive CMT patients with complex phenotypes of ataxia and spasticity.

Retinal Architecture in Autosomal Recessive Spastic Ataxia of Charlevoix-Saguenay (ARSACS): Insights into Disease Pathogenesis and Biomarkers.

BACKGROUND: Autosomal recessive spastic ataxia of Charlevoix-Saguenay (ARSACS) causes unique retinal abnormalities, which have not been systematically investigated. OBJECTIVE: To deeply phenotype the retina in ARSACS in order to better understand its pathogenesis and identify potential biomarkers. METHODS: We evaluated 29 patients with ARSACS, 66 with spinocerebellar ataxia (SCA), 38 with autosomal recessive cerebellar ataxia (ATX), 22 with hereditary spastic paraplegia (SPG), 21 cases of papilledema, and 20 healthy controls (total n = 196 subjects). Participants underwent visual acuity assessment, intraocular pressure measurement, fundoscopy, and macular and peripapillary optical coherence tomography (OCT). Macular layers thicknesses in ARSACS were compared with those of age-matched healthy controls. Ophthalmologists analyzed the scans for abnormal signs in the different patient groups. Linear regression analysis was conducted to look for associations between retinal changes and age, age at onset, disease duration, and Scale for the Assessment and Rating of Ataxia (SARA) scores in ARSACS. RESULTS: Only patients with ARSACS exhibited peripapillary retinal striations (82%) on fundoscopy, and their OCT scans revealed foveal hypoplasia (100%), sawtooth appearance (89%), papillomacular fold (86%), and macular microcysts (18%). Average peripapillary retinal nerve fiber layer (pRNFL) was thicker in ARSACS than in SCA, ATX, SPG, and controls; a cut-off of 121 µm was 100% accurate in diagnosing ARSACS. All macular layers were thicker in ARSACS when compared to healthy controls. RNFL thickness in the inferior sector of the macula positively correlated with SARA scores. CONCLUSIONS: Retinal abnormalities are highly specific for ARSACS, and suggest retinal hyperplasia due to abnormal retinal development. OCT may provide potential biomarkers for future clinical trials. © 2021 International Parkinson and Movement Disorder Society.

A novel SACS p.Pro4154GlnfsTer20 mutation in a family with autosomal recessive spastic ataxia of Charlevoix-Saguenay.

Loss-of-function mutations in the sacsin (SACS) gene lead to autosomal recessive spastic ataxia of Charlevoix-Saguenay (ARSACS), impairing the function of sacsin. Genotype-phenotype correlations are still unclear for the different mutations reported in ARSACS. Here, we present a Turkish ARSACS family in whom the novel homozygous frameshift mutation in SACS c.12461delC (p.Pro4154GlnfsTer20) was detected by next-generation sequencing (NGS). The index patient was admitted with progressive spastic ataxia and dysarthria. Since no common mutation in autosomal recessive (AR) cerebellar ataxias, whole gene sequencing provide an advantage to detect novel mutations and may be more effective for clinical diagnosis.

Proteomics and lipidomic analysis reveal dysregulated pathways associated with loss of sacsin.

Introduction: Autosomal recessive spastic ataxia of Charlevoix-Saguenay (ARSACS) is a rare incurable neurodegenerative disease caused by mutations in the SACS gene, which codes for sacsin, a large protein involved in protein homeostasis, mitochondrial function, cytoskeletal dynamics, autophagy, cell adhesion and vesicle trafficking. However, the pathogenic mechanisms underlying sacsin dysfunction are still largely uncharacterized, and so attempts to develop therapies are still in the early stages. Methods: To achieve further understanding of how processes are altered by loss of sacsin, we used untargeted proteomics to compare protein profiles in ARSACS fibroblasts versus controls. Results: Our analyses confirmed the involvement of known biological pathways and also implicated calcium and lipid homeostasis in ARSACS skin fibroblasts, a finding further verified in SH-SY5Y SACS -/- cells. Validation through mass spectrometry-based analysis and comparative quantification of lipids by LC-MS in fibroblasts revealed increased levels of ceramides coupled with a reduction of diacylglycerols. Discussion: In addition to confirming aberrant Ca2+ homeostasis in ARSACS, this study described abnormal lipid levels associated with loss of sacsin.

Thickened Retinal Nerve Fiber Layer Without Hypermyelination in Autosomal Recessive Spastic Ataxia of Charlevoix-Saguenay.

Purpose: To report the retinal findings in a patient with autosomal recessive spastic ataxia of Charlevoix-Saguenay. Methods: A case was evaluated. Results: A 16-year-old male patient with a known diagnosis of autosomal recessive spastic ataxia of Charlevoix-Saguenay was referred for evaluation of retinal hypermyelination given its frequent association with the condition. The patient was asymptomatic with a best-corrected visual acuity of 20/20. Optical coherence tomography of the peripapillary retinal nerve fiber layer (RNFL) showed bilateral thickening in each eye (average thicknesses: 180 µm, right eye; 177 µm, left eye). An examination showed no myelinization of the RNFL. Conclusions: Most studies to date describe RNFL thickening secondary to hypermyelination as a characteristic finding in autosomal recessive spastic ataxia of Charlevoix-Saguenay. This case provides evidence that this thickening may be a result of hypertrophy rather than hypermyelination. Further investigation is needed to define the pathophysiologic cause of RNFL thickening in autosomal recessive spastic ataxia of Charlevoix-Saguenay.

A Novel SACS Variant Identified in a Chinese Patient: Case Report and Review of the Literature.

Mutations in the SACS gene have been linked to autosomal recessive spastic ataxia of Charlevoix Saguenay (ARSACS). It is a clinically and genetically heterogeneous disease characterized by slow progressive ataxia, spasticity, sensorimotor neuropathy, and a combination of other manifestations, such as lack of spasticity, hearing loss, and epileptic seizures. Currently, there have been very few case reports regarding the SACS gene mutation in Chinese patients. Here, we describe a 35-year-old Chinese patient carrying a novel variant in SACS (c.11486C>T) presenting with progressive ataxia and demyelinating peripheral neuropathy. We then reviewed 22 Chinese cases carrying SACS gene mutations, including our patient. All of them had a cerebellar ataxia gait and showed cerebellar atrophy on brain magnetic resonance imaging (MRI). A total of 28 SACS mutations were identified in these patients. Our study further expands the mutation spectrum of the SACS gene and contributes to the evaluation of genotype-phenotype correlations.

A novel single-point mutation of NEFH and biallelic SACS mutation presenting as intermediate form Charcot-Marie-Tooth: A case report in Vietnam.

Background: Charcot-Marie-Tooth disease (CMT) is among the most common group of inherited neuromuscular diseases. SACS mutations were demonstrated to cause autosomal recessive spastic ataxia of Charlevoix-Saguenay (ARSACS). However, there have been few case reports regarding to NEFH and SACS gene mutation to CMT in Vietnamese patients, and the diagnosis of CMT and ARSACS in the clinical setting still overlapped. Case Description: We report two patients presenting with sensorimotor neuropathy without cerebellar ataxia, spasticity and other neurological features, being diagnosed with intermediate form CMT by electrophysiological and clinical examination and neuroimaging. By whole-exome sequencing panel of two affected members, and PCR Sanger on NEFH and SACS genes to confirm the presence of selected variants on their parents, we identified a novel missense variant NEFH c.1925C>T (inherited from the mother) in an autosomal dominant heterozygous state, and two recessive SACS variants (SACS c.13174C>T, causing missense variant, and SACS c.11343del, causing frameshift variant) (inherited one from the mother and another from the father) in these two patients. Clinical and electrophysiological findings on these patients did not match classical ARSACS. To the best of our knowledge, this is the first case report of two affected siblings diagnosed with CMT carrying both a novel NEFH variant and biallelic SACS variants. Conclusion: We concluded that this novel NEFH variant is likely benign, and biallelic SACS mutation (c.13174C>T and c.11343del) is likely pathogenic for intermediate form CMT. This study is also expected to emphasize the current knowledge of intermediate form CMT, ARSACS, and the phenotypic spectrum of NEFH-related and SACS-related disorders. We expect to give a new understanding of CMT; however, further research should be conducted to provide a more thorough knowledge of the pathogenesis of CMT in the future.

Autosomal Recessive Spastic Ataxia of Charlevoix-Saguenay due to Novel Mutations in the SACS Gene.

Autosomal recessive spastic ataxia of Charlevoix-Saguenay (ARSACS) is characterized by triad of progressive cerebellar ataxia, progressive spasticity, and axonal/demyelinating peripheral neuropathy. Other manifestations include dysarthria, weakness in lower extremities and distal muscle wasting, foot deformities, retinal striation, prolapse of the mitral valve and rarely intellectual disability, hearing loss, and myoclonic epilepsy. We describe a patient who developed peripheral sensorimotor neuropathy in the absence of spasticity on initial presentation. He had nerve root enhancement on magnetic resonance imaging (MRI) lumbar spine, and nerve conduction studies were suggestive of demyelinating polyneuropathy. Patient had mild cerebellar atrophy on MRI and some delay of motor milestones. Over the course of several months, he developed spasticity, and genetic analysis together with clinical presentation was consistent with ARSACS. He was noted to have a pathogenic mutation c.8108G>A (p. Arg2703His) inherited from mother and a variant of uncertain significance c.7216T>C (p. Ser2406Pro) inherited from his father in SACS gene. Atypical cases may present later in life or in absence of one of the classical features at the time of presentation, which may make diagnosis difficult. Our patient had such an atypical presentation of ARSACS. Young patients with neuropathy and concomitant cerebellar atrophy on MRI should raise suspicion for hereditary spastic ataxia syndrome. Follow-up examination can often reveal additional findings to aid the diagnosis.

Autosomal recessive spastic ataxia of Charlevoix-Saguenay caused by novel mutations in SACS gene: A report of two Chinese families.

Autosomal recessive spastic ataxia of Charlevoix-Saguenay (ARSACS) is a rare hereditary disease characterized by cerebellar ataxia, pyramidal signs in lower limbs, and sensorimotor neuropathy. The disease is caused by bi-allelic mutations of the SACS gene encoding the sacsin protein. Over 200 mutations have been reported worldwide. Here, we report two unrelated Chinese ARSACS patients with novel mutations revealed by whole-exome sequencing (WES). One 36-year-old female patient exhibited classical ARSACS characteristics including cerebellar ataxia, pyramidal tract signs in the lower limbs and sensorimotor neuropathy, while the other 9-year-old male showed cerebellar ataxia and peripheral neuropathy. WES identified a compound heterozygous variant in the SACS gene (c.5692 G > T, p.E1898X; c.12673-12677 del TATCA, p.Y4225D fs*6) in the female patient and another compound heterozygous variant (c.1773C > A, p.S578X; c.8088-8089 in. CA, p.M2697Q fs*43) in the male patient. All of these novel mutations were predicted to be loss-of-function which affect the expression of the two important C-terminal domains (DnaJ and HEPN). These findings add new insights into the mutational and clinical spectrum of ARSACS.

Autosomal Recessive Spastic Ataxia of Charlevoix-Saguenay (ARSACS) in a Thai Patient: The Classic Clinical Manifestations, Funduscopic Feature, and Brain Imaging Findings with a Novel Mutation in the SACS Gene.

Background: A 38-year-old woman was diagnosed autosomal recessive spastic ataxia of Charlevoix-Saguenay (ARSACS) with a novel pathogenic variant in the SACS gene presented with gradually progressive spastic ataxia since the age of 2 years; then, she became wheelchair-bound at the age of 28 years. Phenomenology: The patient presented a combination of cerebellar dysfunctions e.g., gaze-evoked nystagmus, scanning speech, finger dysmetria, and wide-based gait, lower limb spasticity, and typical funduscopic examination which was a hypermyelinated nerve fibers radiating from the optic disc. Educational value: At present, ARSACS is recognized as a rare, worldwide, inherited movement disorder in which we should to aware of a diagnosis of this disorder in the patient who is presented with FXN gene negative early-onset spastic ataxia.

Complicated paroxysmal kinesigenic dyskinesia associated with SACS mutations.

BACKGROUND: Autosomal recessive spastic ataxia of Charlevoix-Saguenay (ARSACS) is caused by pathogenic variants in the SACS gene and is characterized by ataxia, peripheral neuropathy, pyramidal impairment and episodic conditions such as epilepsy. Paroxysmal kinesigenic dyskinesia (PKD) had not been previously described in ARSACS. METHODS: We analyzed clinical manifestations and performed whole-exome sequencing (WES) in two independent patients with ARSACS and PKD. Both patients' parents were unaffected. Genetic data were filtered for potential pathogenic variants, searching for de novo mutations suggestive of a dominant disease model or homozygous and compound heterozygous variants of a recessive model. Potential mutations that existed in both patients were generated and subjected to Sanger sequencing. The WES results of 163 PKD patients without additional symptoms from previous experiments were also reviewed. RESULTS: Novel compound heterozygous mutations in the SACS gene were identified in Patient 1 (p.P3007S and p.H3392fs), and a novel homozygous truncating mutation (p.W1376X) was identified in Patient 2. In both patients, each mutant allele was inherited from one of his or her unaffected parents. All 3 mutations were absent in 196 ethnic-matched control chromosomes or in data from the 1000 Genomes Project. No pathogenic variants associated with paroxysmal diseases, especially PKD and episodic ataxia, were identified. In PKD patients without additional symptoms, no homozygous or compound heterozygous variants in the SACS gene were detected. CONCLUSIONS: This study expands the clinical phenotype of ARSACS and suggests the inclusion of SACS screening in patients with PKD plus ARSACS.

Novel frameshift mutation in the SACS gene causing spastic ataxia of charlevoix-saguenay in a consanguineous family from the Arabian Peninsula: A case report and review of literature.

BACKGROUND: Familial cases of autosomal recessive spastic ataxia of charlevoix-saguenay have not been reported in the Arabian Peninsula, although the consanguineous marriage rate is very high. We report the first family from the Arabian Peninsula harboring a novel frameshift mutation in the SACS gene. CASE SUMMARY: A 33-year-old man presented to our neurology clinic with balance problems and weakness of distal upper and lower limbs. He was previously clinically diagnosed with Friedreich's ataxia. However, the severity of polyneuropathy and the electrodiagnostic studies (EDX) findings are atypical features of Friedreich's ataxia, and the deterioration was attributed to diabetic neuropathy. Close examination of other family members identified cerebellar ataxia, lower-limb pyramidal signs, peripheral neuropathy, and magnetic resonance imaging findings characterized by pontine linear hypointensities. Genetic testing for Friedreich's ataxia did not yield a diagnosis. Whole exome sequencing identified a novel frameshift germline mutation in the SACS gene termed c.5824_5827delTACT using the transcript NM_014363.5, which is predicted to cause premature termination of the sacsin protein at amino acid position 1942 (p.Tyr1942Metfs*9) and disrupts the sacsin SRR3 and domains downstream from it. The mutation segregated with the disease in the family. CONCLUSION: Our data add to the spectrum of mutations in the SACS gene and argues for a need to implement suitably integrated clinical and diagnostic services, including next generation sequencing technology, to better classify ataxia in this area of the world.

A novel homozygous SACS mutation identified by whole exome sequencing-genotype phenotype correlations of all published cases.

ARSACS is an autosomal recessive disorder characterized by ataxia, spasticity, and polyneuropathy. A plethora of worldwide distributed mutations have been described so far. Here, we report two brothers, born to non-consanguineous parents, presenting with cerebellar ataxia and peripheral neuropathy. Whole-exome sequencing revealed the presence of a novel homozygous variant in the SACS gene. The variant was confirmed by Sanger sequencing and found at heterozygous state in both parents. This is the first reported mutation in this gene, in Greek population. This case report further highlights the growing trend of identifying genetic diseases previously restricted to single, ethnically isolated regions in many different ethnic groups worldwide. Additionally, we performed a systematic review of all published cases with SACs mutations. ARSACS seems to be an important cause of ataxia and many different types of mutations have been identified, mainly located in exon 10. We evaluated the mutation pathogenicity in all previously reported cases to investigate possible phenotype-genotype correlations. We managed to find a correlation between the pathogenicity of mutations, severity of the phenotype, and age of onset of ARSACS. Greater mutation numbers in different populations will be important and mutation-specific functional studies will be essential to identify the pathogenicity of the various ARSACS variants.

Autosomal-Recessive Spastic Ataxia of Charlevoix-Saguenay: A Turkish Child.

Autosomal-recessive spastic ataxia of Charlevoix-Saguenay (ARSACS) is caused by mutations of the SACS gene, characterized by late-infantile-onset spastic ataxia and other neurological features. ARSACS has a high prevalence in northeastern Quebec, Canada. Recently, several ARSACS cases have been reported from outside Canada. We report typical clinical and neuroimaging features in a Turkish child, which confirmed genetic diagnosis of ARSACS.

Spastic ataxias.

The presence of spasticity and pyramidal features is a hallmark of some of hereditary ataxias, such as autosomal-recessive spastic ataxia of Charlevoix-Saguenay, other primary spastic ataxias, Friedreich ataxia, or ataxia with isolated vitamin E deficiency. Certain spastic paraplegias, such as spastic paraplegia 7, may present as an ataxic phenotype and often share common pathophysiologic pathways with cerebellar ataxias. Because of the rarity and genetic heterogeneity of these conditions, their molecular diagnosis remains challenging and time consuming. Herein we review the clinical, epidemiologic, and genetic features of the best-defined spastic ataxias with a focus on autosomal-recessive spastic ataxia of Charlevoix-Saguenay, one of the most frequent ataxias worldwide, which presents with a unique early-onset spastic ataxia phenotype. We briefly discuss other genetic and metabolic multisystem disorders where spastic ataxia is a secondary feature. Emphasis is placed on their typical age of onset and key clinical and imaging features that enable discrimination between these complex diseases.

Current and Promising Therapies in Autosomal Recessive Ataxias.

BACKGROUND & OBJECTIVE: Ataxia is clinically characterized by unsteady gait and imbalance. Cerebellar disorders may arise from many causes such as metabolic diseases, stroke or genetic mutations. The genetic causes are classified by mode of inheritance and include autosomal dominant, X-linked and autosomal recessive ataxias. Many years have passed since the description of the Friedreich's ataxia, the most common autosomal recessive ataxia, and mutations in many other genes have now been described. The genetic mutations mostly result in the accumulation of toxic metabolites which causes Purkinje neuron lost and eventual cerebellar dysfunction. Unfortunately, the recessive ataxias remain a poorly known group of diseases and most of them are yet untreatable. CONCLUSION: The aim of this review is to provide a comprehensive clinical profile and to review the currently available therapies. We overview the physiopathology, neurological features and diagnostic approach of the common recessive ataxias. The emphasis is also made on potential drugs currently or soon-to-be in clinical trials. For instance, promising gene therapies raise the possibility of treating differently Friedreich's ataxia, Ataxia-telangiectasia, Wilson's disease and Niemann-Pick disease in the next few years.

Inner Retinal Dysfunction in the Autosomal Recessive Spastic Ataxia of Charlevoix-Saguenay.

The autosomal recessive spastic ataxia of Charlevoix-Saguenay (ARSACS) is associated with structural retinal abnormalities either directly visible on funduscopy or revealed by optical coherence tomography (OCT). Most patients with ARSACS have a whitish peripapillary appearance corresponding to a thickening of the peripapillary retinal nerve fiber layer. OCT has also shown an absence of the physiological foveal depression. Abnormal electroretinography (ERG) has previously been reported in only two cases, without further details. This report describes a patient with ARSACS in whom careful full-field ERG revealed dysfunction of the retinal On- bipolar cells with sparing of photoreceptor function. This is the first report of inner retinal dysfunction in ARSACS.

A novel hemizygous SACS mutation identified by whole exome sequencing and SNP array analysis in a Chinese ARSACS patient.

The array of autosomal recessive spastic ataxia of Charlevoix-Saguenay (ARSACS) has expanded worldwide after the first description in the Charlevoix-Saguenay region of Québec. Here, we report a Chinese ARSACS patient presenting progressive peripheral neuropathy (CMTNS2=15) with horizontal gaze nystagmus and mild spastic gait. Genetic studies including whole exome sequencing (WES), Sanger sequencing and single nucleotide polymorphism (SNP) array analysis revealed a novel hemizygous nonsense mutation (c.11803C>T, p.Gln3935X) of SACS and a 1.33Mb deletion involved in SACS on chromosome 13q12.12 in the patient. Our findings highlight the necessity of SACS mutation screening in the gene panel of inherited peripheral neuropathies, and stress the need of testing copy number variation (CNV) in SACS mutation screening.

Autosomal recessive spastic ataxia of Charlevoix-Saguenay (ARSACS): typical clinical and neuroimaging features in a Brazilian family / Ataxia espástica autossômica recessiva de Charlevoix-Saguenay (ARSACS): aspectos clínicos e de neuroimagem típicos em uma família brasileira

Autosomal recessive spastic ataxia of Charlevoix-Saguenay (ARSACS) is a neurodegenerative disorder characterized by late-infantile onset spastic ataxia and other neurological features. ARSACS has a high prevalence in northeastern Quebec, Canada. Several ARSACS cases have been reported outside Canada in recent decades. This is the first report of typical clinical and neuroimaging features in a Brazilian family with probable diagnosis of ARSACS.

A ataxia espástica autossômica recessiva de Charlevoix-Saguenay (ARSACS) é doença degenerativa do sistema nervoso, caracterizada por ataxia associada a espasticidade, entre outras manifestações neurológicas, de início na infância. A doença tem alta prevalência na região de Quebec, no Canadá. Muitos relatos de ARSACS têm sido descritos fora do Canadá nas últimas décadas. Nesse artigo, relatamos a primeira descrição dos aspectos clínicos e de neuroimagem típicos em uma família brasileira com provável diagnóstico de ARSACS.