Spinocerebellar ataxias (SCAs) are a genetically heterogeneous group of autosomal dominant movement disorders. Among the SCAs associated with impaired ion channel function, SCA19/22 is caused by pathogenic variants in KCND3, which encodes the voltage-gated potassium channel Kv4.3. SCA19/22 is clinically characterized by ataxia, dysarthria and oculomotor dysfunction in combination with other signs and symptoms, including mild cognitive impairment, peripheral neuropathy and pyramidal signs. The known KCND3 pathogenic variants are localized either in the transmembrane segments, the connecting loops, or the C-terminal region of Kv4.3. We have identified a novel pathogenic variant, c.455A>G (p.D152G), localized in the N-terminus of Kv4.3. It is located in the immediate neighbourhood of the T1 domain, which is responsible for multimerization with the β-subunit KChIP2b and thus for the formation of functional heterooctamers. Electrophysiological studies showed that p.D152G does not affect channel gating, but reduces the ionic current in Kv4.3, even though the variant is not located in the transmembrane domains. Impaired channel trafficking to the plasma membrane may contribute to this effect. In a patient with a clinical picture corresponding to SCA19/22, p.D152G is the first pathogenic variant in the N-terminus of Kv4.3 to be described to date with an effect on ion channel activity.

OBJECTIVE: Brain MRI abnormalities and increases in neurofilament light chain (NfL) have mostly been observed in cross-sectional studies before ataxia onset in polyglutamine spinocerebellar ataxias. Our study aimed to identify longitudinal changes in biological, clinical, and/or imaging biomarkers in spinocerebellar ataxia (SCA) 2 and SCA7 carriers over 1 year.
METHODS: We studied SCA2 and SCA7 carriers and controls (expansion-negative relatives) at the Paris Brain Institute. Inclusion criteria included Scale for the Assessment and Rating of Ataxia (SARA) scores between 0 and 15. Assessments at baseline, 6 months, and 12 months comprised neurologic, quality of life, orofacial motor, neuropsychological, and ophthalmologic examinations, along with gait and oculomotor recordings, brain MRI, CSF, and blood sampling. The primary outcome was the longitudinal change in these assessments over 1 year.
RESULTS: We included 15 SCA2 carriers, 15 SCA7 carriers, and 10 controls between May 2020 and April 2021. At baseline, the ages were similar (41 [37, 46] for SCA2, 38 [28.5, 39.8] for SCA7, and 39.5 [31, 54.5] for controls, p = 0.78), as well the sex (p = 0.61); SARA scores were low but different (4 [1.25, 6.5] in SCA2, 2 [0, 11.5] in SCA7, and 0 in controls, p < 0.01). Pons and medulla volumes were smaller in SCAs (p < 0.05) and cerebellum volume only in SCA2 (p = 0.01). Plasma NfL levels were higher in SCA participants (SCA2: 14.2 pg/mL [11.52, 15.89], SCA7: 15.53 [13.27, 23.23]) than in controls (4.88 [3.56, 6.17], p < 0.001). After 1-year follow-up, in SCA2, there was significant pons (-144 ± 60 mm3) and cerebellum (-1,508 ± 580 mm3) volume loss and a worsening of gait assessment; in SCA7, SARA score significantly increased (+1.3 ± 0.4) and outer retinal nuclear layer thickness decreased (-15.4 ± 1.6 μm); for both SCA groups, the orofacial motor assessment significantly worsened. For preataxic and early ataxic carriers, the strongest longitudinal deterioration on outcome measures was orofacial motility in SCA2 and retinal thickness in SCA7.
CONCLUSIONS: Despite the limitation of the small sample size, we detected annual changes in preataxic and early ataxic SCA individuals across brain MRI imaging, clinical scores, gait parameters, and retinal thickness. These parameters could serve as potential end points for future therapeutic trials in the preataxic phase.
UNASSIGNED: ClinicalTrials.gov NCT04288128.

Since 1991, several genetic disorders caused by unstable trinucleotide repeats (TNRs) have been identified, collectively referred to as triplet repeat diseases (TREDs). They share a common mutation mechanism: the expansion of repeats (dynamic mutations) due to the propensity of repeated sequences to form unusual DNA structures during replication. TREDs are characterized as neurodegenerative diseases or complex syndromes with significant neurological components. Spinocerebellar ataxia type 17 (SCA17) falls into the former category and is caused by the expansion of mixed CAA/CAG repeats in the TBP gene. To date, a five-unit organization of this region [(CAG)3 (CAA)3] [(CAG)n] [CAA CAG CAA] [(CAG)n] [CAA CAG], with expansion in the second [(CAG)n] unit being the most common, has been proposed. In this study, we propose an alternative organization scheme for the repeats. A search of the PubMed database was conducted to identify articles reporting both the number and composition of GAC/CAA repeats in TBP alleles. Nineteen reports were selected. The sequences of all identified CAG/CAA repeats in the TBP locus, including 67 cases (probands and b relatives), were analyzed in terms of their repetition structure and stability in inheritance, if possible. Based on the analysis of three units [(CAG)3 (CAA)2] [CAA (CAG)n CAA CAG] [CAA (CAG)n CAA CAG], the organization of repeats is proposed. Detailed analysis of the CAG/CAA repeat structure, not just the number of repeats, in TBP-expanded alleles should be performed, as it may have a prognostic value in the prediction of stability/instability during transmission and the possible anticipation of the disease.

BACKGROUND: Recently, an exonic GGC repeat expansion (RE) was identified by long-read genome sequencing in the ZFHX3 gen, causing spinocerebellar ataxia type 4 (SCA4), a dominant form of ataxia with sensory neuropathy. However, the analysis of larger cohorts of patients remained demanding, resulting in a challenge to diagnose patients and leaving the question of anticipation in SCA4 unanswered.
OBJECTIVE: We aimed to develop a GGC repeat test for clinical SCA4 screening and to apply this test to screen two large German SCA pedigrees and samples of unrelated patients collected over the last 25 years.
METHODS: We modulated a commercial GGC-RE kit (Bio-Techne AmplideX® Asuragen® PCR/CE FMR1 Reagents) with ZFHX3-specific primers and adapted PCR conditions. The test was applied to patients and 50 healthy controls to determine the exact repeat number. Clinical data were revised and correlated with the expanded allele sizes and an exploratory analysis of structural MRI was performed.
RESULTS: Repeat size, determined by our protocol for (GGC)n RE analysis shows a strong inverse correlation between repeat length and age at onset and anticipation in subsequent generations. The phenotype also appears to be more strongly expressed in carriers of longer RE. Clinical red flags were slowed saccades, sensory neuropathy and autonomic dysfunction.
CONCLUSIONS: Our protocol enables cost-effective and robust screening for the causative SCA4 RE within ZFHX3. Furthermore, detailed clinical data of our patients gives a more precise view on SCA4, which seems to be more common among patients with ataxia than expected.

BACKGROUND: Autosomal recessive spastic ataxia ofCharlevoix-Saguenay (ARSACS) is a rare neurodegenerative disorder characterizedby early-onset cerebellar ataxia, peripheral sensorimotor neuropathy, and lowerlimb spasticity. We present clinical andgenetic data of the first Bulgarian patients diagnosed with ARSACS by wholeexome sequencing (WES).
METHODS: Variant filtering was performed usinglocally established pipeline and the selected variants were analysed by Sangersequencing. All patients underwent clinical examination and testingincluding the standard rating scales for spastic paraplegia and ataxia.
RESULTS: Five different SACS gene variants, three of which novel, have been identified inpatients from three different ethnic groups. In addition to the classicalclinical triad, brain MRI revealed cerebellar atrophy, linear pontineT2-hypointensities, and hyperintense rim lateral tothalamus combined with retinal nerve fiber layer thickening on opticcoherence tomography (OCT).
CONCLUSIONS: We expand the mutation, geographic, and phenotypic spectrum of ARSACS, adding Bulgaria to the world map of the disease, and drawing attention to the fact that it is still misdiagnosed. We demonstrated that brain MRI and OCT are necessary clinical tests for ARSACS diagnosis, even if one of the cardinal clinical features is lacking.

We evaluated the efficacy and safety of 1-year treatment with nilotinib (Tasigna®) in patients with autosomal dominant spinocerebellar ataxia (ADSCA) and the factors associated with responsiveness. From an institutional cohort, patients with ADSCA who completed a 1-year treatment with nilotinib (150-300 mg/day) were included. Ataxia severity was assessed using the Scale for the Rating and Assessment of Ataxia (SARA), scores at baseline and 1, 3, 6, and 12 months. A subject was categorized \'responsive\' when the SARA score reduction at 12 M was > 0. Pretreatment serum proteomic analysis included subjects with the highest (n = 5) and lowest (n = 5) SARA score change at 12 months and five non-ataxia controls. Thirty-two subjects (18 [56.2%] females, median age 42 [30-49.5] years) were included. Although SARA score at 12 M did not significantly improve in overall population, 20 (62.5%) subjects were categorized as responsive. Serum proteomic analysis identified 4 differentially expressed proteins, leucine-rich alpha-2-glycoprotein (LRG1), vitamin-D binding protein (DBP), and C4b-binding protein (C4BP) beta and alpha chain, which are involved in the autophagy process. This preliminary data suggests that nilotinib might improve ataxia severity in some patients with ADSCA. Serum protein markers might be a clue to predict the response to nilotinib.Trial Registration Information: Effect of Nilotinib in Cerebellar Ataxia Patients (NCT03932669, date of submission 01/05/2019).

Hereditary ataxias are one of the «anticipation diseases» types. Spinocerebral ataxia type 2 occurs when the number of CAG repeats in the coding region of the ATXN2 gene exceeds 34 or more. In healthy people, the CAG repeat region in the ATXN2 gene usually consists of 22-23 CAG trinucleotides. Mutations that increase the length of CAG repeats can cause severe neurodegenerative and neuromuscular disorders known as trinucleotide repeat expansion diseases. The mechanisms causing such diseases are associated with non-canonical configurations that can be formed in the CAG repeat region during replication, transcription or repair. This makes it relevant to study the zones of open states that arise in the region of CAG repeats under torque. The purpose of this work is to study, using mathematical modeling, zones of open states in the region of CAG repeats of the ATXN2 gene, caused by torque. It has been established that the torque effect on the 1st exon of the ATXN2 gene, in addition to the formation of open states in the promoter region, can lead to the formation of additional various sizes open states zones in the CAG repeats region. Moreover, the frequency of additional large zones genesis increases with increasing number of CAG repeats. The inverse of this frequency correlates with the dependence of the disease onset average age on the CAG repeats length. The obtained results will allow us to get closer to understanding the genetic mechanisms that cause trinucleotide repeat diseases.

BACKGROUND: Spinocerebellar ataxia 4 (SCA4), characterized in 1996, features adult-onset ataxia, polyneuropathy, and linkage to chromosome 16q22.1; its underlying mutation has remained elusive.
OBJECTIVE: To explore the radiological and neuropathological abnormalities in the entire neuroaxis in SCA4 and search for its mutation.
METHODS: Three Swedish families with undiagnosed ataxia went through clinical, neurophysiological, and neuroimaging tests, including PET studies and genetic investigations. In four cases, neuropathological assessments of the neuroaxis were performed. Genetic testing included short read whole genome sequencing, short tandem repeat analysis with ExpansionHunter de novo, and long read sequencing.
RESULTS: Novel features for SCA4 include dysautonomia, motor neuron affection, and abnormal eye movements. We found evidence of anticipation; neuroimaging demonstrated atrophy in the cerebellum, brainstem, and spinal cord. [18F]FDG-PET demonstrated brain hypometabolism and [11C]Flumazenil-PET reduced binding in several brain lobes, insula, thalamus, hypothalamus, and cerebellum. Moderate to severe loss of Purkinje cells in the cerebellum and of motor neurons in the anterior horns of the spinal cord along with pronounced degeneration of posterior tracts was also found. Intranuclear, mainly neuronal, inclusions positive for p62 and ubiquitin were sparse but widespread in the CNS. This finding prompted assessment for nucleotide expansions. A polyglycine stretch encoding GGC expansions in the last exon of the zink finger homeobox 3 gene was identified segregating with disease and not found in 1000 controls.
CONCLUSIONS: SCA4 is a neurodegenerative disease caused by a novel GGC expansion in the coding region of ZFHX3, and its spectrum is expanded to include dysautonomia and neuromuscular manifestations.

BACKGROUND:  Cerebellar ataxias comprise sporadic and genetic etiologies. Ataxia may also be a presenting feature in hereditary spastic paraplegias (HSPs).
OBJECTIVE:  To report a descriptive analysis of the frequency of different forms of cerebellar ataxia evaluated over 17 years in the Ataxia Unit of Universidade Federal de São Paulo, Brazil.
METHODS:  Charts of patients who were being followed from January 2007 to December 2023 were reviewed. We used descriptive statistics to present our results as frequencies and percentages of the overall analysis. Diagnosed patients were classified according to the following 9 groups: sporadic ataxia, spinocerebellar ataxias (SCAs), other autosomal dominant cerebellar ataxias, autosomal recessive cerebellar ataxias (ARCAs), mitochondrial ataxias, congenital ataxias, X-linked ataxias, HSPs, and others.
RESULTS:  There were 1,332 patients with ataxias or spastic paraplegias. Overall, 744 (55.85%) of all cases were successfully diagnosed: 101 sporadic ataxia, 326 SCAs, 20 of other autosomal dominant cerebellar ataxias, 186 ARCAs, 6 X-linked ataxias, 2 mitochondrial ataxias, 4 congenital ataxias, and 51 HSPs.
CONCLUSIONS:  This study describes the frequency of cerebellar ataxias in a large group of patients followed for the past 17 years, of whom 55% obtained a definitive clinical or molecular diagnosis. Future demographic surveys in Brazil or Latin American remain necessary.
BACKGROUND:  Ataxias cerebelares compreendem as etiologias esporádicas e genéticas. Ataxia também pode ser uma característica das paraplegias espásticas hereditárias (HSPs).
OBJECTIVE:  Relatar uma análise descritiva da frequência das diferentes formas de ataxias cerebelares avaliadas ao longo de 17 anos no Setor da Ataxias da Universidade Federal de São Paulo, Brasil. MéTODOS:  Prontuários de pacientes acompanhados de janeiro de 2007 a dezembro de 2023 foram revisados. Usamos análise descritiva para apresentar nossos resultados como frequências e percentuais. Os pacientes foram classificados de acordo com os 9 grupos seguintes: ataxias esporádicas, ataxias espinocerebelares (SCA), outras ataxias cerebelares autossômicas dominantes, ataxias cerebelares autossômicas recessivas (ARCA), ataxias mitocondriais, ataxias congênitas, ataxias ligadas ao X, PEH e outros.
RESULTS:  Foram avaliados 1.332 pacientes. Desse total, 744 tiveram um diagnóstico definitivo: 101 ataxias esporádicas, 326 SCA, 20 outras ataxias cerebelares autossômicas dominantes, 186 (ARCA), 6 ataxias ligadas ao X, 2 ataxias mitocondriais, 4 ataxias congênitas e 51 HSP. CONCLUSãO:  Esse estudo descreve a frequência e a etiologia das ataxias em um grande grupo de pacientes acompanhados nos últimos 17 anos, dos quais 55% obtiveram diagnóstico clínico ou molecular definitivos. Estudos demográficos futuros do Brasil ou da América Latina continuam sendo necessários.

OBJECTIVE: Spinocerebellar ataxia SCA1 and SCA2 are adult-onset hereditary disorders, due to triplet CAG expansion in their respective causative genes. The pathophysiology of SCA1 and SCA2 suggests alterations of cerebello-thalamo-cortical pathway and its connections to the basal ganglia. In this framework, thalamic integrity is crucial for shaping efficient whole-brain dynamics and functions. The aims of the study are to identify structural changes in thalamic nuclei in presymptomatic and symptomatic SCA1 and SCA2 patients and to assess disease progression within a 1-year interval.
METHODS: A prospective 1-year clinical and MRI assessment was conducted in 27 presymptomatic and 23 clinically manifest mutation carriers for SCA1 and SCA2 expansions. Cross-sectional and longitudinal changes of thalamic nuclei volume were investigated in SCA1 and SCA2 individuals and in healthy participants (n = 20).
RESULTS: Both SCA1 and SCA2 patients had significant atrophy in the majority of thalamic nuclei, except for the posterior and partly medial nuclei. The 1-year longitudinal evaluation showed a specific pattern of atrophy in ventral and posterior thalamus, detectable even at the presymptomatic stage of the disease.
CONCLUSIONS: For the first time in vivo, our exploratory study has shown that different thalamic nuclei are involved at different stages of the degenerative process in both SCA1 and SCA2. It is therefore possible that thalamic alterations might significantly contribute to the progression of the disease years before overt clinical manifestations occur.