The genetic basis of early-onset hereditary ataxia in Iran: results of a national registry of a heterogeneous population.

BACKGROUND: To investigate the genetics of early-onset progressive cerebellar ataxia in Iran, we conducted a study at the Children's Medical Center (CMC), the primary referral center for pediatric disorders in the country, over a three-year period from 2019 to 2022. In this report, we provide the initial findings from the national registry. METHODS: We selected all early-onset patients with an autosomal recessive mode of inheritance to assess their phenotype, paraclinical tests, and genotypes. The clinical data encompassed clinical features, the Scale for the Assessment and Rating of Ataxia (SARA) scores, Magnetic Resonance Imaging (MRI) results, Electrodiagnostic exams (EDX), and biomarker features. Our genetic investigations included single-gene testing, Whole Exome Sequencing (WES), and Whole Genome Sequencing (WGS). RESULTS: Our study enrolled 162 patients from various geographic regions of our country. Among our subpopulations, we identified known and novel pathogenic variants in 42 genes in 97 families. The overall genetic diagnostic rate was 59.9%. Notably, we observed PLA2G6, ATM, SACS, and SCA variants in 19, 14, 12, and 10 families, respectively. Remarkably, more than 59% of the cases were attributed to pathogenic variants in these genes. CONCLUSIONS: Iran, being at the crossroad of the Middle East, exhibits a highly diverse genetic etiology for autosomal recessive hereditary ataxia. In light of this heterogeneity, the development of preventive strategies and targeted molecular therapeutics becomes crucial. A national guideline for the diagnosis and management of patients with these conditions could significantly aid in advancing healthcare approaches and improving patient outcomes.

TPP1 Variants in Iranian patients: A Novel Pathogenic Homozygous Variant Causing Neuronal Ceroid Lipofuscinosis 2.

Introduction: TPP1 variants have been identified as a causative agent of neuronal ceroid lipofuscinosis 2 disease, that ataxia is one of its clinical features. Therefore, here, molecular study of TPP1 variants is presented in an Iranian cohort and a novel pathogenic variant is described. Methods: This investigation was conducted as a cross-sectional study in a tertiary referral hospital, Children's Medical Center, Pediatrics Center of Excellence. Clinical presentations and pedigrees were documented. Patients with cerebellar ataxia were enrolled in this study. Next-generation sequencing was applied to confirm the diagnosis. Segregation and bioinformatics analyses were also done for the variants using Sanger sequencing. Results: Forty-five patients were included in our study. The mean age of onset was 104 (+55.60) months (minimum = 31 months, maximum = 216 months). The majority of cases (73.3%) were born to consanguineous parents and only 1 patient (2.2%) had an affected sibling. Of the 45 patients, only 1 patient with a novel pathogenic variant (c.1425_1425+1delinsAT, p.A476Cfs*15) in the TPP1 gene was identified. Discussion: The main strength of current study is the relatively large sample size. Besides, a novel pathogenic variant could be important toward the diagnosis and management of this condition. With significant advances in various therapies, early diagnosis could improve the treatments using personalized-based medicine.

Ataxia-associated DNA repair genes protect the Drosophila mushroom body and locomotor function against glutamate signaling-associated damage.

The precise control of motor movements is of fundamental importance to all behaviors in the animal kingdom. Efficient motor behavior depends on dedicated neuronal circuits - such as those in the cerebellum - that are controlled by extensive genetic programs. Autosomal recessive cerebellar ataxias (ARCAs) provide a valuable entry point into how interactions between genetic programs maintain cerebellar motor circuits. We previously identified a striking enrichment of DNA repair genes in ARCAs. How dysfunction of ARCA-associated DNA repair genes leads to preferential cerebellar dysfunction and impaired motor function is however unknown. The expression of ARCA DNA repair genes is not specific to the cerebellum. Only a limited number of animal models for DNA repair ARCAs exist, and, even for these, the interconnection between DNA repair defects, cerebellar circuit dysfunction, and motor behavior is barely established. We used Drosophila melanogaster to characterize the function of ARCA-associated DNA repair genes in the mushroom body (MB), a structure in the Drosophila central brain that shares structural features with the cerebellum. Here, we demonstrate that the MB is required for efficient startle-induced and spontaneous motor behaviors. Inhibition of synaptic transmission and loss-of-function of ARCA-associated DNA repair genes in the MB affected motor behavior in several assays. These motor deficits correlated with increased levels of MB DNA damage, MB Kenyon cell apoptosis and/or alterations in MB morphology. We further show that expression of genes involved in glutamate signaling pathways are highly, specifically, and persistently elevated in the postnatal human cerebellum. Manipulation of glutamate signaling in the MB induced motor defects, Kenyon cell DNA damage and apoptosis. Importantly, pharmacological reduction of glutamate signaling in the ARCA DNA repair models rescued the identified motor deficits, suggesting a role for aberrant glutamate signaling in ARCA-DNA repair disorders. In conclusion, our data highlight the importance of ARCA-associated DNA repair genes and glutamate signaling pathways to the cerebellum, the Drosophila MB and motor behavior. We propose that glutamate signaling may confer preferential cerebellar vulnerability in ARCA-associated DNA repair disorders. Targeting glutamate signaling could provide an exciting therapeutic entry point in this large group of so far untreatable disorders.

Novel Compound Heterozygous Mutations in the SYNE1 Gene in a Taiwanese Family: A Case Report and Literature Review.

Mutations in the synaptic nuclear envelope protein 1 (SYNE1) gene are associated with substantial clinical heterogeneity. Here, we report the first case of SYNE1 ataxia in Taiwan due to two novel truncating mutations. Our patient, a 53-year-old female, exhibited pure cerebellar ataxia with c.1922del in exon 18 and c. C3883T mutations in exon 31. Previous studies have indicated that the prevalence of SYNE1 ataxia among East Asian populations is low. In this study, we identified 27 cases of SYNE1 ataxia from 22 families in East Asia. Of the 28 patients recruited in this study (including our patient), 10 exhibited pure cerebellar ataxia, and 18 exhibited ataxia plus syndromes. We could not find an exact correlation between genotypes and phenotypes. Additionally, we established a precise molecular diagnosis in our patient's family and extended the findings on the ethnic, phenotypic, and genotypic diversity of the SYNE1 mutational spectrum.

Heterozygous pathogenic variants in CWF19L1 in a Chinese family with spinocerebellar ataxia, autosomal recessive 17.

BACKGROUND: CWF19L1 is responsible for spinocerebellar ataxia, autosomal recessive 17, which presents with cerebellar ataxia, and atrophy. Here, we report novel compound heterozygous variants of CWF19L1 in a Chinese family with progressive ataxia and mental retardation of unknown etiology by analyzing clinical characteristics and genetic variations. METHODS: Clinical profiles and genomic DNA extracts of family members were collected. Whole-exome and Sanger sequencing were performed to detect associated genetic variants. Pathogenicity prediction and conservation analysis of the identified variants were performed using bioinformatics tools. RESULTS: We identified heterozygous variants at the invariant +2 position (c.1555_c.1557delGAG in exon 14 and c.1070G > T in exon 11) of the CWF19L1 gene. Two novel heterozygous variants of the CWF19L1 gene were identified in the CWF19L1 gene associated with autosomal recessive cerebellar ataxia. CONCLUSION: Our results suggest that CWF19L1 variants may be a novel cause of recessive ataxia with developmental delay. Whole-exome sequencing is an efficient tool for screening variants associated with the disease. This case report may help diagnose and identify the causes of other ataxias, leading to novel therapies, especially in China. This finding enriches the variant spectrum of the CWF19L1 gene and lays the foundation for future studies on the correlation between genotype and phenotype.

Discovery of Therapeutics Targeting Oxidative Stress in Autosomal Recessive Cerebellar Ataxia: A Systematic Review.

Autosomal recessive cerebellar ataxias (ARCAs) are a heterogeneous group of rare neurodegenerative inherited disorders. The resulting motor incoordination and progressive functional disabilities lead to reduced lifespan. There is currently no cure for ARCAs, likely attributed to the lack of understanding of the multifaceted roles of antioxidant defense and the underlying mechanisms. This systematic review aims to evaluate the extant literature on the current developments of therapeutic strategies that target oxidative stress for the management of ARCAs. We searched PubMed, Web of Science, and Science Direct Scopus for relevant peer-reviewed articles published from 1 January 2016 onwards. A total of 28 preclinical studies fulfilled the eligibility criteria for inclusion in this systematic review. We first evaluated the altered cellular processes, abnormal signaling cascades, and disrupted protein quality control underlying the pathogenesis of ARCA. We then examined the current potential therapeutic strategies for ARCAs, including aromatic, organic and pharmacological compounds, gene therapy, natural products, and nanotechnology, as well as their associated antioxidant pathways and modes of action. We then discussed their potential as antioxidant therapeutics for ARCAs, with the long-term view toward their possible translation to clinical practice. In conclusion, our current understanding is that these antioxidant therapies show promise in improving or halting the progression of ARCAs. Tailoring the therapies to specific disease stages could greatly facilitate the management of ARCAs.

Case Report: Late-Onset Autosomal Recessive Cerebellar Ataxia Associated With SYNE1 Mutation in a Chinese Family.

Autosomal recessive cerebellar ataxia type 1 (ARCA-1), also known as autosomal recessive spinocerebellar ataxia type 8 (SCAR8), is caused by spectrin repeat containing nuclear envelope protein 1 (SYNE1) gene mutation. Nesprin-1, encoded by SYNE1, is widely expressed in various tissues, especially in the striated muscle and cerebellum. The destruction of Nesprin-1 is related to neuronal and neuromuscular lesions. It has been reported that SYNE1 gene variation is associated with Emery-Dreifuss muscular dystrophy type 4, arthrogryposis multiplex congenita, SCAR8, and dilated cardiomyopathy. The clinical manifestations of SCAR8 are mainly characterized by relatively pure cerebellar ataxia and may be accompanied by upper and/or lower motor neuron dysfunction. Some affected people may also display cerebellar cognitive affective syndrome. It is conventionally held that the age at the onset of SCAR8 is between 6 and 42 years (the median age is 17 years). Here, we report a pedigree with SCAR8 where the onset age in the proband is 48 years. This case report extends the genetic profile and clinical features of SCAR8. A new pathogenic site (c.7578del; p.S2526Sfs*8) located in SYNE1, which is the genetic cause of the patient, was identified via whole exome sequencing (WES).

History of Ataxias and Paraplegias with an Annotation on the First Description of Striatonigral Degeneration.

The aim of this paper is to carry out a historical overview of the evolution of the knowledge on degenerative cerebellar disorders and hereditary spastic paraplegias, over the last century and a half. Original descriptions of the main pathological subtypes, including Friedreich's ataxia, hereditary spastic paraplegia, olivopontocerebellar atrophy and cortical cerebellar atrophy, are revised. Special attention is given to the first accurate description of striatonigral degeneration by Hans Joachim Scherer, his personal and scientific trajectory being clarified. Pathological classifications of ataxia are critically analysed. The current clinical-genetic classification of ataxia is updated by taking into account recent molecular discoveries. We conclude that there has been an enormous progress in the knowledge of the nosology of hereditary ataxias and paraplegias, currently encompassing around 200 genetic subtypes.

Expanding the phenotype of AFG3L2 mutations: Late-onset autosomal recessive spinocerebellar ataxia.

The AFG3L2 gene encodes AFG3-like protein 2, which is a subunit of human mitochondrial ATPases associated with various cellular protease activities (m-AAA). The clinical spectrum of AFG3L2 mutations is broad. Dominant AFG3L2 mutations can cause autosomal dominant spinocerebellar ataxia type 28 (SCA28), whereas biallelic AFG3L2 mutations may lead to spastic ataxia 5 (SPAX5). However, the role of AFG3L2 mutations in autosomal recessive spinocerebellar ataxia (SCAR) remains elusive. The aim of this study is to delineate the clinical features and spectrum of AFG3L2 mutations in a Taiwanese cohort with cerebellar ataxia. Mutational analyses of AFG3L2 were carried out by targeted resequencing in a cohort of 133 unrelated patients with molecularly undetermined cerebellar ataxia. We identified one single patient carrying compound heterozygous mutations in AFG3L2, p.[R632*];[V723M] (c.[1894C > T];[2167G > A]). The patient has suffered from apparently sporadic and slowly progressive cerebellar ataxia, ptosis, and ophthalmoparesis since age 55 years. These findings expand the clinical spectrum of AFG3L2 mutations and suggest a new subtype of late-onset SCAR caused by biallelic AFG3L2 mutations.

Autosomal Recessive Cerebellar Ataxia 1: First Case Report Depicting a Variant in SYNE1 Gene in a Chilean Patient.

Autosomal recessive cerebellar ataxia type 1 (ARCA-1) or spinocerebellar ataxia autosomal recessive type 8 (SCAR8) is a slowly progressive neurodegenerative disorder that occurs due to mutations in the spectrin repeat containing nuclear envelope protein 1 (SYNE1) gene. Previously considered a rare cause of ARCA, related to French-Canadian patients from Beauce, Quebec, Canada, SYNE1 ataxia is now known to be of worldwide distribution. We present the case report of a 54-year-old male patient with the genetic diagnosis of SYNE1 ataxia, presenting with a SYNE1 gene mutation never described in Chilean population before.

A Novel Variant in CWF19L1 Gene in a Family with Late-Onset Autosomal Recessive Cerebellar Ataxia 17.

INTRODUCTION: Previously published studies demonstrated that mutations in CWF19L1 cause early-onset autosomal recessive cerebellar ataxia 17. In this article, we report a novel homozygous missense variant in CWF19L1 in two sisters who had late-onset cerebellar ataxia with epilepsy and describe their clinical and neuroradiological findings. METHODS: We included two female patients with typical symptoms of cerebellar ataxia supported by the MRI findings. Whole exome sequencing (WES) data analysis was performed to identify the underlying genetic defect in the proband. Sanger sequencing was used to confirm the variant in other family members. RESULTS: WES revealed a homozygous missense variant in CWF19-like protein 1; CWF19L1 gene c.395A>G; p.(Asp132Gly) (RefSeq NM_018294.4). This variant has not been described previously in the literature. Mutations in this gene are known to cause an autosomal recessive disorder, spinocerebellar ataxia, autosomal recessive 17 (OMIM #616127). CONCLUSION: In conclusion, we report a novel variant in CWF19L1 as a candidate causal variant in two sisters with autosomal recessive cerebellar ataxia. This is the first report coming from Arab countries. Additional reports in patients with a progressive course and adult-onset are needed, but this could be the first report of this disease diagnosed in adulthood since it is a disease of children and adolescents. In addition, our patients had epileptic seizures, which were not previously documented in patients with CWF19L1 mutations. We postulate that mutations in this gene have widespread functional and structural changes in multiple levels of the neuraxis rather than being a pure cerebellar disorder.

Autosomal Recessive Cerebellar Ataxia Type 1: Phenotypic and Genetic Correlation in a Cohort of Chinese Patients with SYNE1 Variants.

Mutations in the synaptic nuclear envelope protein 1 (SYNE1) gene have been reported to cause autosomal recessive cerebellar ataxia (ARCA) type 1 with highly variable clinical phenotypes. The aim of this study was to describe the phenotypic-genetic spectrum of SYNE1-related ARCA1 patients in the Chinese population. We screened 158 unrelated patients with autosomal recessive or sporadic ataxia for variants in SYNE1 using next-generation sequencing. Pathogenicity assessment of SYNE1 variants was interpreted according to the American College of Medical Genetics standards and guidelines. We identified eight truncating variants and two missense variants spreading throughout the SYNE1 gene from six unrelated families, including nine novel variants and one reported variant. Of the six index patients, two patients showed the classical pure cerebellar ataxia, while four patients exhibited non-cerebellar phenotypes, including motor neuron symptoms, cognitive impairment, or mental retardation. The variants associated with motor neuron or cognition involvement tend to be located in the C-terminal region of SYNE1 protein, compared with the variants related to pure cerebellar ataxia. Our data indicating SYNE1 mutation is one of the more common causes of recessive ataxia in the Chinese population. The use of next-generation sequencing has enabled the rapid analysis of recessive ataxia and further expanded our understanding of genotype-phenotype correlation.

Synaptic Nuclear Envelope Protein 1 (SYNE 1) Ataxia with Amyotrophic Lateral Sclerosis-like Presentation: A Novel Synaptic Nuclear Envelope Protein 1 (SYNE 1) Gene Deletion Mutation from India.

A 24-year-old female presented with wasting and weakness of both hands and fasciculations over the chin since 12 years, followed by imbalance while walking and speech changes since 10 years. Her 12-year-old sister also had a similar clinical presentation. There were fasciculations over the chin, tongue, hands, back, thighs with wasting and weakness in tongue, and C7, C8, T1 segments in both upper limbs along with bipyramidal signs. There was limb and gait ataxia. Magnetic resonance imaging brain showed pancerebellar atrophy, and electromyography was suggestive of anterior horn cell involvement in bulbar, cervical, thoracic, and lumbar segments. Next-generation sequencing identified a novel likely pathogenic deletion mutation: chr6:152527389_152527399del, c.22711_22721del, and p.Ala7571ArgfsTer4 in exon 125 of synaptic nuclear envelope protein 1 (SYNE1) gene. This mutation leads to frameshift and premature termination of the protein 'Nesprin 1'. Amyotrophic lateral sclerosis-like presentation followed by cerebellar ataxia have been described with SYNE1 ataxia. This unique phenotype and novel deletion mutation of SYNE1 gene is the first case reported from India.

Late-onset autosomal recessive cerebellar ataxia and neuropathy with a novel splicing mutation in the ATM gene.

Autosomal recessive cerebellar ataxias comprise many types of diseases. The most frequent autosomal recessive cerebellar ataxias are Friedreich ataxia, but other types are relatively rare. We encountered a consanguineous family with two cases of late-onset cerebellar ataxia with neuropathy. We performed whole-exome sequencing in one patient and confirmed by Sanger sequencing in other family members. Neurological examination revealed cerebellar ataxia, hand tremor, and neck dystonia, distal muscle wasting, and diminished tendon reflexes. The patients had no conjunctival telangiectasia or immunodeficiency. Blood examination revealed slightly elevated α-fetoprotein. Brain MRI demonstrated marked cerebellar atrophy and mild brainstem atrophy. The electrophysiologic study and nerve biopsy showed axonal neuropathy. Whole-exome sequencing revealed a novel homozygous missense variant (NM_000051.3: c.496G > C) in the ataxia-telangiectasia mutated gene. This homozygous variant was found in another patient, co-segregated within the family members-this variant results in aberrant splicing (skipping exon 5) on RT-PCR analysis. We identified the ataxia-telangiectasia mutated variant in an adult, late-onset autosomal recessive cerebellar ataxias family. We should consider ataxia-telangiectasia even in late-onset autosomal recessive cerebellar ataxias without telangiectasia or immunodeficiency.

Concurrence of multiple sclerosis, oligodendroglioma, and autosomal recessive cerebellar ataxia with spasticity in the same patient: A challenging diagnosis.

Multiple sclerosis (MS) has been described in several case reports to coexist with brain tumors. This unusual concurrence has been the subject of research projects with a common question of whether these pathological entities share common roots. However, no clear association has proved that either of them could provoke the other, and mere chance is the only acceptable explanation. Along all reported cases, oligodendroglioma has been rarely reported to coexist with MS. In this paper, we report a unique case with a triad of MS, oligodendroglioma, and autosomal recessive cerebellar ataxia with spasticity and discuss possible theories that might have attributed to these three conditions. To our knowledge, this is the first case ever to have these three conditions present in one patient. The most likely explanation is believed to be that this patient was unfortunate to have three unrelated diseases.

Whole exome and targeted gene sequencing to detect pathogenic recessive variants in early onset cerebellar ataxia.

Over 100 genetically distinct causal known loci for hereditary ataxia phenotype poses a challenge for diagnostic work-up for ataxia patients in a clinically relevant time and precision. In the present study using next-generation sequencing, we have investigated pathogenic variants in early-onset cerebellar ataxia cases using whole exome sequencing in singleton/family-designed and targeted gene-panel sequencing. A total of 98 index patients were clinically and genetically (whole exome sequencing (WES) in 16 patients and targeted gene panel of 41 ataxia causing genes in 82 patients) evaluated. Four families underwent WES in family based design. Overall, we have identified 24 variants comprising 20 pathogenic and four likely-pathogenic both rare/novel, variations in 21 early onset cerebellar ataxia patients. Among the identified variations, SACS (n = 7) and SETX (n = 6) were frequent, while ATM (n = 2), TTPA (n = 2) and other rare loci were observed. We have prioritized novel pathogenic variants in RARS2 and FA2H loci through family based design in two out of four families.

Exome sequencing found a novel homozygous deletion in ADCK3 gene involved in autosomal recessive spinocerebellar ataxia.

Autosomal recessive cerebellar ataxia is heterogeneous inherited neurodegenerative disorders with more than 70 involved genes. The development of next generation sequencing opens a new window in rapid diagnosis of such heterogeneous condition in medical genetics laboratories. Here, we present ADCK3; del.CD (229-230) mutation in an Iranian consanguineous family with three cerebellar ataxic boys using whole exome sequencing. The mutation was predicted pathogenic and all the affected individuals were homozygous for the variant. Although, the ADCK3 was previously reported as one of the master genes of ARSC, our mutation was novel as has been not previously reported in dbSNP or literature.

A new MRI marker of ataxia with oculomotor apraxia.

PURPOSE: Evaluate the specificity and sensitivity of disappearance of susceptibility weighted imaging (SWI) dentate nuclei (DN) hypointensity in oculomotor apraxia patients (AOA). METHOD: In this prospective study, 27 patients with autosomal genetic ataxia (AOA (n = 11), Friedreich ataxia and ataxia with vitamin E deficit (n = 4), and dominant genetic ataxia (n = 12)) were included along with fifteen healthy controls. MRIs were qualitatively classified for the presence or absence of DN hypointensity on FLAIR and SWI sequences. The MRIs were then quantitatively studied, with measurement of a ratio of DN over brainstem white matter signal intensity through manual delineation. The institutional review board approved this study, and written informed consent was obtained. In the cross-sectional analysis, the Mann-Whitney test was applied. RESULTS: Qualitatively, the eleven AOA patients presented absence of both DN SWI and FLAIR hyposignals; three dominant genetic ataxia patients had moderate SWI DN hyposignal and absent FLAIR hyposignal; the thirteen remaining subjects presented normal SWI and FLAIR DN hyposignal. Absence of DN SWI hypointensity was 100% sensitive and specific to AOA. Quantitative signal intensity ratio (mean ± standard deviation) of the AOA group (98·96 ± 5·37%) was significantly higher than in control subjects group (76.40 ± 8.34%; p < 0.001), dominant genetic ataxia group (81·15 ± 9·94%; p < 0·001), and Friedreich ataxia and ataxia with vitamin E deficit group (87·56 ± 2·78%; p < 0·02). CONCLUSION: This small study shows that loss of the normal hypointensity in the dentate nucleus on both SWI and FLAIR imaging at 3 T is a highly sensitive and specific biomarker for AOA.