Hereditary Ataxias in Cuba: A Nationwide Epidemiological and Clinical Study in 1001 Patients

The Cerebellum - The prevalence estimations of hereditary ataxias are biased since most epidemiological studies are confined to isolated geographical regions and few nationwide studies are...     

Unexpanded and intermediate CAG polymorphisms at the SCA2 locus (ATXN2) in the Cuban population: evidence about the origin of expanded SCA2 alleles

The role of short, large or intermediate normal alleles (ANs) of the ataxin-2 gene in generating expanded alleles (EAs) causing spinocerebellar ataxia type 2 (SCA2) is poorly understood. It has been postulated that SCA2 prevalence is related to the frequency of large ANs. SCA2 shows the highest worldwide prevalence in Cuban population, which is therefore a unique source for studying the relationship between the frequency of large and intermediate alleles and the frequency of SCA2 mutation. Through genetic polymorphism analyses in a comprehensive sample (~3000 chromosomes), we show that the frequency of large ANs in the ataxin-2 gene is the highest worldwide, although short ANs are also frequent. This highly polymorphic population displayed also high variability in the CAG sequence, featured by loss of the anchor CAA interruption(s). In addition, large ANs showed germinal and somatic instability. Our study also includes related genotypic, genealogical and haplotypic data and provides substantial evidence with regard to the role of large and intermediate alleles in the generation of pathological EAs.     

Testosterone Levels Are Decreased and Associated with Disease Duration in Male Spinocerebellar Ataxia Type 2 Patients

The Cerebellum - Spinocerebellar ataxia type 2 (SCA2) is a progressive neurodegenerative disorder due to an unstable expansion of a CAG repeat in the ATXN2 gene. Despite clinical and experimental...     

Uncommon features in Cuban families affected with Friedreich ataxia

This report describes two families who presented with autosomal recessive ataxia. By means of Polymerase Chain Reaction (PCR) molecular testing we identified expansions in the gene encoding Frataxin (FTX) that is diagnostic of Friedreich ataxia. A history of reproductive loss in the two families, prominent scoliosis deformity preceding the onset of ataxic gait, the presence of a sensitive axonal neuropathy, as well as the common origin of ancestors are unusual features of these families. These cases illustrate the importance of molecular diagnosis in patients with a recessive ataxia. The origin of the expanded gene and the GAA repeat size in the normal population are issues to be further investigated. The molecular diagnosis of Friedreich ataxia is now established in Cuba.     

Gene Therapy for Polyglutamine Spinocerebellar Ataxias: Advances,Challenges, and Perspectives

Polyglutamine spinocerebellar ataxias (SCAs) comprise a heterogeneous group of six autosomal dominant ataxias caused by cytosine–adenine–guanine repeat expansions in the coding region of single genes. Currently, there is no curative or disease-slowing treatment for these disorders, but their monogenic inheritance has informed rationales for development of gene therapy strategies. In fact, RNA interference strategies have shown promising findings in cellular and/or animal models of SCA1, SCA3, SCA6, and SCA7. In addition, antisense oligonucleotide therapy has provided encouraging proofs of concept in models of SCA1, SCA2, SCA3, and SCA7, but they have not yet progressed to clinical trials. On the contrary, the gene editing strategies, such as the clustered regularly interspaced short palindromic repeat (CRISPR/Cas9), have been introduced to a limited extent in these disorders. In this article, we review the available literature about gene therapy in polyglutamine SCAs and discuss the main technological and ethical challenges toward the prospect of their use in future clinical trials. Although antisense oligonucleotide therapies are further along the path to clinical phases, the recent failure of three clinical trials in Huntington's disease may delay their utilization for polyglutamine SCAs, but they offer lessons that could optimize the likelihood of success in potential future clinical studies. © 2021 International Parkinson and Movement Disorder Society     

Comprehensive Study of Early Features in Spinocerebellar Ataxia 2: Delineating the Prodromal Stage of the Disease

The prodromal phase of spinocerebellar ataxias (SCAs) has not been systematically studied. Main findings come from a homogeneous SCA type 2 (SCA2) population living in Cuba. The aim of this study was to characterize extensively the prodromal phase of SCA2 by several approaches. Thirty-seven non-ataxic SCA2 mutation carriers and its age- and sex-matched controls underwent clinical assessments, including standardized neurological exam, structured interviews and clinical scales, and looking for somatic and autonomic features, as well as a neuropsychological battery, antisaccadic recordings, and MRI scans. Main clinical somatic features of non-ataxic mutation carriers were cramps, sensory symptoms, sleep disorders, and hyperreflexia, whereas predominating autonomic symptoms were pollakiuria/nocturia, constipation, and frequent throat clearing. Cognitive impairments included early deficits of executive functions and visual memory, suggesting the involvement of cerebro-cerebellar-cerebral loops and/or reduced cholinergic basal forebrain input to the cortex. Antisaccadic task revealed impaired oculomotor inhibitory control but preserved ability for error correction. Cognitive and antisaccadic deficits were higher as carriers were closer to the estimated onset of ataxia, whereas higher Scale for the Assessment and Rating of Ataxia (SARA) scores were associated most notably to vermis atrophy. The recognition of early features of SCA2 offers novel insights into the prodromal phase and physiopathological base of the disease, allowing the assessment of its progression and the efficacy of treatments, in particular at early phases when therapeutical options should be most effective.     

Subtle rapid eye movement sleep abnormalities in presymptomatic spinocerebellar ataxia type 2 gene carriers

Rapid eye movement (REM) sleep disorders are commonly associated to patients with spinocerebellar ataxia type 2 (SCA2); however, these abnormalities have not been studied in presymptomatic gene carriers. To determine whether the REM sleep pathology is detectable before clinical manifestation of SCA2 and evaluate it as a preclinical biomarker, we studied 36 presymptomatic SCA2 individuals and 36 controls by video‐polysomnography (VPSG) and sleep questionnaires. Presymptomatic subjects showed significant decrease of REM sleep percentage, REMs density, total sleep time, and sleep efficiency. Aging effect on REM sleep percentage was significant in both groups. There was no correlation between cytosine‐adenine‐guanine (CAG) repeat length and REM sleep. Our findings identified the REM sleep pathology as a prominent herald sign of SCA2, conferring a special importance to VPSG as a sensitive neurophysiological tool to detect early changes associated with SCA2, which contributes to the understanding of disease pathophysiology and the development of therapeutic trials focused on the preclinical disease stage. © 2010 Movement Disorder Society.     

Early corticospinal tract damage in prodromal SCA2 revealed by EEG-EMG and EMG-EMG coherence

Objective

Clinical data suggest early involvement of the corticospinal tract (CST) in spinocerebellar ataxia type 2 (SCA2). Here we tested if early CST degeneration can be detected in prodromal SCA2 mutation carriers by electrophysiological markers of CST integrity.