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13 pages, 5262 KiB

Open AccessArticle

Superior Cerebellar Atrophy: An Imaging Clue to Diagnose ITPR1-Related Disorders

by Romina Romaniello, Ludovica Pasca, Elena Panzeri, Fulvio D’Abrusco, Lorena Travaglini, Valentina Serpieri, Sabrina Signorini, Chiara Aiello, Enrico Bertini, Maria Teresa Bassi, Enza Maria Valente, Ginevra Zanni, Renato Borgatti and Filippo Arrigoni

Int. J. Mol. Sci. 2022, 23(12), 6723; https://doi.org/10.3390/ijms23126723 - 16 Jun 2022

Cited by 8 | Viewed by 4311

Abstract

The inositol 1,4,5-triphosphate receptor type 1 (ITPR1) gene encodes an InsP₃-gated calcium channel that modulates intracellular Ca²⁺ release and is particularly expressed in cerebellar Purkinje cells. Pathogenic variants in the ITPR1 gene are associated with different types of [...] Read more.

The inositol 1,4,5-triphosphate receptor type 1 (ITPR1) gene encodes an InsP₃-gated calcium channel that modulates intracellular Ca²⁺ release and is particularly expressed in cerebellar Purkinje cells. Pathogenic variants in the ITPR1 gene are associated with different types of autosomal dominant spinocerebellar ataxia: SCA15 (adult onset), SCA29 (early-onset), and Gillespie syndrome. Cerebellar atrophy/hypoplasia is invariably detected, but a recognizable neuroradiological pattern has not been identified yet. With the aim of describing ITPR1-related neuroimaging findings, the brain MRI of 14 patients with ITPR1 variants (11 SCA29, 1 SCA15, and 2 Gillespie) were reviewed by expert neuroradiologists. To further evaluate the role of superior vermian and hemispheric cerebellar atrophy as a clue for the diagnosis of ITPR1-related conditions, the ITPR1 gene was sequenced in 5 patients with similar MRI pattern, detecting pathogenic variants in 4 of them. Considering the whole cohort, a distinctive neuroradiological pattern consisting in superior vermian and hemispheric cerebellar atrophy was identified in 83% patients with causative ITPR1 variants, suggesting this MRI finding could represent a hallmark for ITPR1-related disorders. Full article

(This article belongs to the Special Issue Cerebellar Ataxia)

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10 pages, 22697 KiB

Open AccessCommunication

Hsp90 Inhibition: A Promising Therapeutic Approach for ARSACS

by Suran Nethisinghe, Rosella Abeti, Maheswaran Kesavan, W. Christian Wigley and Paola Giunti

Int. J. Mol. Sci. 2021, 22(21), 11722; https://doi.org/10.3390/ijms222111722 - 29 Oct 2021

Cited by 5 | Viewed by 4394

Abstract

Autosomal recessive spastic ataxia of Charlevoix-Saguenay (ARSACS) is a neurodegenerative disease caused by mutations in the SACS gene, encoding the 520 kDa modular protein sacsin, which comprises multiple functional sequence domains that suggest a role either as a scaffold in protein folding or [...] Read more.

Autosomal recessive spastic ataxia of Charlevoix-Saguenay (ARSACS) is a neurodegenerative disease caused by mutations in the SACS gene, encoding the 520 kDa modular protein sacsin, which comprises multiple functional sequence domains that suggest a role either as a scaffold in protein folding or in proteostasis. Cells from patients with ARSACS display a distinct phenotype including altered organisation of the intermediate filament cytoskeleton and a hyperfused mitochondrial network where mitochondrial respiration is compromised. Here, we used vimentin bundling as a biomarker of sacsin function to test the therapeutic potential of Hsp90 inhibition with the C-terminal-domain-targeted compound KU-32, which has demonstrated mitochondrial activity. This study shows that ARSACS patient cells have significantly increased vimentin bundling compared to control, and this was also present in ARSACS carriers despite them being asymptomatic. We found that KU-32 treatment significantly reduced vimentin bundling in carrier and patient cells. We also found that cells from patients with ARSACS were unable to maintain mitochondrial membrane potential upon challenge with mitotoxins, and that the electron transport chain function was restored upon KU-32 treatment. Our preliminary findings presented here suggest that targeting the heat-shock response by Hsp90 inhibition alleviates vimentin bundling and may represent a promising area for the development of therapeutics for ARSACS. Full article

(This article belongs to the Special Issue Cerebellar Ataxia)

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16 pages, 3887 KiB

Open AccessArticle

A Novel KCNA2 Variant in a Patient with Non-Progressive Congenital Ataxia and Epilepsy: Functional Characterization and Sensitivity to 4-Aminopyridine

by Paola Imbrici, Elena Conte, Rikard Blunck, Fabrizia Stregapede, Antonella Liantonio, Michele Tosi, Maria Cristina D’Adamo, Annamaria De Luca, Vesna Brankovic and Ginevra Zanni

Int. J. Mol. Sci. 2021, 22(18), 9913; https://doi.org/10.3390/ijms22189913 - 14 Sep 2021

Cited by 13 | Viewed by 3540

Abstract

Kv1.2 channels, encoded by the KCNA2 gene, are localized in the central and peripheral nervous system, where they regulate neuronal excitability. Recently, heterozygous mutations in KCNA2 have been associated with a spectrum of symptoms extending from epileptic encephalopathy, intellectual disability, and cerebellar ataxia. [...] Read more.

Kv1.2 channels, encoded by the KCNA2 gene, are localized in the central and peripheral nervous system, where they regulate neuronal excitability. Recently, heterozygous mutations in KCNA2 have been associated with a spectrum of symptoms extending from epileptic encephalopathy, intellectual disability, and cerebellar ataxia. Patients are treated with a combination of antiepileptic drugs and 4-aminopyridine (4-AP) has been recently trialed in specific cases. We identified a novel variant in KCNA2, E236K, in a Serbian proband with non-progressive congenital ataxia and early onset epilepsy, treated with sodium valproate. To ascertain the pathogenicity of E236K mutation and to verify its sensitivity to 4-AP, we transfected HEK 293 cells with Kv1.2 WT or E236K cDNAs and recorded potassium currents through the whole-cell patch-clamp. In silico analysis supported the electrophysiological data. E236K channels showed voltage-dependent activation shifted towards negative potentials and slower kinetics of deactivation and activation compared with Kv1.2 WT. Heteromeric Kv1.2 WT+E236K channels, resembling the condition of the heterozygous patient, confirmed a mixed gain- and loss-of-function (GoF/LoF) biophysical phenotype. 4-AP inhibited both Kv1.2 and E236K channels with similar potency. Homology modeling studies of mutant channels suggested a reduced interaction between the residue K236 in the S2 segment and the gating charges at S4. Overall, the biophysical phenotype of E236K channels correlates with the mild end of the clinical spectrum reported in patients with GoF/LoF defects. The response to 4-AP corroborates existing evidence that KCNA2-disorders could benefit from variant-tailored therapeutic approaches, based on functional studies. Full article

(This article belongs to the Special Issue Cerebellar Ataxia)

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23 pages, 1606 KiB

Open AccessArticle

NGS in Hereditary Ataxia: When Rare Becomes Frequent

by Daniele Galatolo, Giovanna De Michele, Gabriella Silvestri, Vincenzo Leuzzi, Carlo Casali, Olimpia Musumeci, Antonella Antenora, Guja Astrea, Melissa Barghigiani, Roberta Battini, Carla Battisti, Caterina Caputi, Ettore Cioffi, Giuseppe De Michele, Maria Teresa Dotti, Tommasina Fico, Chiara Fiorillo, Serena Galosi, Maria Lieto, Alessandro Malandrini, Marina A. B. Melone, Andrea Mignarri, Gemma Natale, Elena Pegoraro, Antonio Petrucci, Ivana Ricca, Vittorio Riso, Salvatore Rossi, Anna Rubegni, Arianna Scarlatti, Francesca Tinelli, Rosanna Trovato, Gioacchino Tedeschi, Alessandra Tessa, Alessandro Filla and Filippo Maria Santorelli Show full author list Hide full author list

Int. J. Mol. Sci. 2021, 22(16), 8490; https://doi.org/10.3390/ijms22168490 - 6 Aug 2021

Cited by 18 | Viewed by 5257

Abstract

The term hereditary ataxia (HA) refers to a heterogeneous group of neurological disorders with multiple genetic etiologies and a wide spectrum of ataxia-dominated phenotypes. Massive gene analysis in next-generation sequencing has entered the HA scenario, broadening our genetic and clinical knowledge of these [...] Read more.

The term hereditary ataxia (HA) refers to a heterogeneous group of neurological disorders with multiple genetic etiologies and a wide spectrum of ataxia-dominated phenotypes. Massive gene analysis in next-generation sequencing has entered the HA scenario, broadening our genetic and clinical knowledge of these conditions. In this study, we employed a targeted resequencing panel (TRP) in a large and highly heterogeneous cohort of 377 patients with a clinical diagnosis of HA, but no molecular diagnosis on routine genetic tests. We obtained a positive result (genetic diagnosis) in 33.2% of the patients, a rate significantly higher than those reported in similar studies employing TRP (average 19.4%), and in line with those performed using exome sequencing (ES, average 34.6%). Moreover, 15.6% of the patients had an uncertain molecular diagnosis. STUB1, PRKCG, and SPG7 were the most common causative genes. A comparison with published literature data showed that our panel would have identified 97% of the positive cases reported in previous TRP-based studies and 92% of those diagnosed by ES. Proper use of multigene panels, when combined with detailed phenotypic data, seems to be even more efficient than ES in clinical practice. Full article

(This article belongs to the Special Issue Cerebellar Ataxia)

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13 pages, 8887 KiB

Open AccessArticle

Interruptions of the FXN GAA Repeat Tract Delay the Age at Onset of Friedreich’s Ataxia in a Location Dependent Manner

by Suran Nethisinghe, Maheswaran Kesavan, Heather Ging, Robyn Labrum, James M. Polke, Saiful Islam, Hector Garcia-Moreno, Martina F. Callaghan, Francesca Cavalcanti, Mark A. Pook and Paola Giunti

Int. J. Mol. Sci. 2021, 22(14), 7507; https://doi.org/10.3390/ijms22147507 - 13 Jul 2021

Cited by 13 | Viewed by 4158

Abstract

Friedreich’s ataxia (FRDA) is a comparatively rare autosomal recessive neurological disorder primarily caused by the homozygous expansion of a GAA trinucleotide repeat in intron 1 of the FXN gene. The repeat expansion causes gene silencing that results in deficiency of the frataxin protein [...] Read more.

Friedreich’s ataxia (FRDA) is a comparatively rare autosomal recessive neurological disorder primarily caused by the homozygous expansion of a GAA trinucleotide repeat in intron 1 of the FXN gene. The repeat expansion causes gene silencing that results in deficiency of the frataxin protein leading to mitochondrial dysfunction, oxidative stress and cell death. The GAA repeat tract in some cases may be impure with sequence variations called interruptions. It has previously been observed that large interruptions of the GAA repeat tract, determined by abnormal MboII digestion, are very rare. Here we have used triplet repeat primed PCR (TP PCR) assays to identify small interruptions at the 5′ and 3′ ends of the GAA repeat tract through alterations in the electropherogram trace signal. We found that contrary to large interruptions, small interruptions are more common, with 3′ interruptions being most frequent. Based on detection of interruptions by TP PCR assay, the patient cohort (n = 101) was stratified into four groups: 5′ interruption, 3′ interruption, both 5′ and 3′ interruptions or lacking interruption. Those patients with 3′ interruptions were associated with shorter GAA1 repeat tracts and later ages at disease onset. The age at disease onset was modelled by a group-specific exponential decay model. Based on this modelling, a 3′ interruption is predicted to delay disease onset by approximately 9 years relative to those lacking 5′ and 3′ interruptions. This highlights the key role of interruptions at the 3′ end of the GAA repeat tract in modulating the disease phenotype and its impact on prognosis for the patient. Full article

(This article belongs to the Special Issue Cerebellar Ataxia)

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11 pages, 1414 KiB

Open AccessArticle

Genetic Dominant Variants in STUB1, Segregating in Families with SCA48, Display In Vitro Functional Impairments Indistinctive from Recessive Variants Associated with SCAR16

by Yasaman Pakdaman, Siren Berland, Helene J. Bustad, Sigrid Erdal, Bryony A. Thompson, Paul A. James, Kjersti N. Power, Ståle Ellingsen, Martin Krooni, Line I. Berge, Adrienne Sexton, Laurence A. Bindoff, Per M. Knappskog, Stefan Johansson and Ingvild Aukrust

Int. J. Mol. Sci. 2021, 22(11), 5870; https://doi.org/10.3390/ijms22115870 - 30 May 2021

Cited by 11 | Viewed by 4382

Abstract

Variants in STUB1 cause both autosomal recessive (SCAR16) and dominant (SCA48) spinocerebellar ataxia. Reports from 18 STUB1 variants causing SCA48 show that the clinical picture includes later-onset ataxia with a cerebellar cognitive affective syndrome and varying clinical overlap with SCAR16. However, little is [...] Read more.

Variants in STUB1 cause both autosomal recessive (SCAR16) and dominant (SCA48) spinocerebellar ataxia. Reports from 18 STUB1 variants causing SCA48 show that the clinical picture includes later-onset ataxia with a cerebellar cognitive affective syndrome and varying clinical overlap with SCAR16. However, little is known about the molecular properties of dominant STUB1 variants. Here, we describe three SCA48 families with novel, dominantly inherited STUB1 variants (p.Arg51_Ile53delinsProAla, p.Lys143_Trp147del, and p.Gly249Val). All the patients developed symptoms from 30 years of age or later, all had cerebellar atrophy, and 4 had cognitive/psychiatric phenotypes. Investigation of the structural and functional consequences of the recombinant C-terminus of HSC70-interacting protein (CHIP) variants was performed in vitro using ubiquitin ligase activity assay, circular dichroism assay and native polyacrylamide gel electrophoresis. These studies revealed that dominantly and recessively inherited STUB1 variants showed similar biochemical defects, including impaired ubiquitin ligase activity and altered oligomerization properties of the CHIP. Our findings expand the molecular understanding of SCA48 but also mean that assumptions concerning unaffected carriers of recessive STUB1 variants in SCAR16 families must be re-evaluated. More investigations are needed to verify the disease status of SCAR16 heterozygotes and elucidate the molecular relationship between SCA48 and SCAR16 diseases. Full article

(This article belongs to the Special Issue Cerebellar Ataxia)

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14 pages, 2176 KiB

Open AccessArticle

CACNA1A Mutations Causing Early Onset Ataxia: Profiling Clinical, Dysmorphic and Structural-Functional Findings

by Antonio F. Martínez-Monseny, Albert Edo, Dídac Casas-Alba, Mercè Izquierdo-Serra, Mercè Bolasell, David Conejo, Loreto Martorell, Jordi Muchart, Laura Carrera, Carlos I. Ortez, Andrés Nascimento, Baldo Oliva, José M. Fernández-Fernández and Mercedes Serrano

Int. J. Mol. Sci. 2021, 22(10), 5180; https://doi.org/10.3390/ijms22105180 - 13 May 2021

Cited by 6 | Viewed by 5642

Abstract

The CACNA1A gene encodes the pore-forming α_1A subunit of the voltage-gated Ca_V2.1 Ca²⁺ channel, essential in neurotransmission, especially in Purkinje cells. Mutations in CACNA1A result in great clinical heterogeneity with progressive symptoms, paroxysmal events or both. During infancy, clinical [...] Read more.

The CACNA1A gene encodes the pore-forming α_1A subunit of the voltage-gated Ca_V2.1 Ca²⁺ channel, essential in neurotransmission, especially in Purkinje cells. Mutations in CACNA1A result in great clinical heterogeneity with progressive symptoms, paroxysmal events or both. During infancy, clinical and neuroimaging findings may be unspecific, and no dysmorphic features have been reported. We present the clinical, radiological and evolutionary features of three patients with congenital ataxia, one of them carrying a new variant. We report the structural localization of variants and their expected functional consequences. There was an improvement in cerebellar syndrome over time despite a cerebellar atrophy progression, inconsistent response to acetazolamide and positive response to methylphenidate. The patients shared distinctive facial gestalt: oval face, prominent forehead, hypertelorism, downslanting palpebral fissures and narrow nasal bridge. The two α_1A affected residues are fully conserved throughout evolution and among the whole human Ca_V channel family. They contribute to the channel pore and the voltage sensor segment. According to structural data analysis and available functional characterization, they are expected to exert gain- (F1394L) and loss-of-function (R1664Q/R1669Q) effect, respectively. Among the CACNA1A-related phenotypes, our results suggest that non-progressive congenital ataxia is associated with developmental delay and dysmorphic features, constituting a recognizable syndromic neurodevelopmental disorder. Full article

(This article belongs to the Special Issue Cerebellar Ataxia)

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11 pages, 2370 KiB

Open AccessArticle

Novel KCND3 Variant Underlying Nonprogressive Congenital Ataxia or SCA19/22 Disrupt K_V4.3 Protein Expression and K+ Currents with Variable Effects on Channel Properties

by Ginevra Zanni, Cheng-Tsung Hsiao, Ssu-Ju Fu, Chih-Yung Tang, Alessandro Capuano, Luca Bosco, Federica Graziola, Emanuele Bellacchio, Serenella Servidei, Guido Primiano, Bing-Wen Soong and Chung-Jiuan Jeng

Int. J. Mol. Sci. 2021, 22(9), 4986; https://doi.org/10.3390/ijms22094986 - 7 May 2021

Cited by 14 | Viewed by 3407

Abstract

KCND3 encodes the voltage-gated potassium channel K_V4.3 that is highly expressed in the cerebellum, where it regulates dendritic excitability and calcium influx. Loss-of-function K_V4.3 mutations have been associated with dominant spinocerebellar ataxia (SCA19/22). By targeted NGS sequencing, we identified [...] Read more.

KCND3 encodes the voltage-gated potassium channel K_V4.3 that is highly expressed in the cerebellum, where it regulates dendritic excitability and calcium influx. Loss-of-function K_V4.3 mutations have been associated with dominant spinocerebellar ataxia (SCA19/22). By targeted NGS sequencing, we identified two novel KCND3 missense variants of the K_V4.3 channel: p.S347W identified in a patient with adult-onset pure cerebellar syndrome and p.W359G detected in a child with congenital nonprogressive ataxia. Neuroimaging showed mild cerebellar atrophy in both patients. We performed a two-electrode voltage-clamp recording of K_V4.3 currents in Xenopus oocytes: both the p.G345V (previously reported in a SCA19/22 family) and p.S347W mutants exhibited reduced peak currents by 50%, while no K+ current was detectable for the p.W359G mutant. We assessed the effect of the mutations on channel gating by measuring steady-state voltage-dependent activation and inactivation properties: no significant alterations were detected in p.G345V and p.S347W disease-associated variants, compared to controls. K_V4.3 expression studies in HEK293T cells showed 53% (p.G345V), 45% (p.S347W) and 75% (p.W359G) reductions in mutant protein levels compared with the wildtype. The present study broadens the spectrum of the known phenotypes and identifies additional variants for KCND3-related disorders, outlining the importance of SCA gene screening in early-onset and congenital ataxia. Full article

(This article belongs to the Special Issue Cerebellar Ataxia)

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11 pages, 2771 KiB

Open AccessArticle

Expanding the β-III Spectrin-Associated Phenotypes toward Non-Progressive Congenital Ataxias with Neurodegeneration

by Paula Sancho, Amparo Andrés-Bordería, Nerea Gorría-Redondo, Katia Llano, Dolores Martínez-Rubio, María Eugenia Yoldi-Petri, Luba Blumkin, Pablo Rodríguez de la Fuente, Fernando Gil-Ortiz, Leonor Fernández-Murga, Ana Sánchez-Monteagudo, Vincenzo Lupo, Belén Pérez-Dueñas, Carmen Espinós and Sergio Aguilera-Albesa

Int. J. Mol. Sci. 2021, 22(5), 2505; https://doi.org/10.3390/ijms22052505 - 2 Mar 2021

Cited by 11 | Viewed by 2785

Abstract

(1) Background: A non-progressive congenital ataxia (NPCA) phenotype caused by β-III spectrin (SPTBN2) mutations has emerged, mimicking spinocerebellar ataxia, autosomal recessive type 14 (SCAR14). The pattern of inheritance, however, resembles that of autosomal dominant classical spinocerebellar ataxia type 5 (SCA5). (2) [...] Read more.

(1) Background: A non-progressive congenital ataxia (NPCA) phenotype caused by β-III spectrin (SPTBN2) mutations has emerged, mimicking spinocerebellar ataxia, autosomal recessive type 14 (SCAR14). The pattern of inheritance, however, resembles that of autosomal dominant classical spinocerebellar ataxia type 5 (SCA5). (2) Methods: In-depth phenotyping of two boys studied by a customized gene panel. Candidate variants were sought by structural modeling and protein expression. An extensive review of the literature was conducted in order to better characterize the SPTBN2-associated NPCA. (3) Results: Patients exhibited an NPCA with hypotonia, developmental delay, cerebellar syndrome, and cognitive deficits. Both probands presented with progressive global cerebellar volume loss in consecutive cerebral magnetic resonance imaging studies, characterized by decreasing midsagittal vermis relative diameter measurements. Cortical hyperintensities were observed on fluid-attenuated inversion recovery (FLAIR) images, suggesting a neurodegenerative process. Each patient carried a novel de novo SPTBN2 substitution: c.193A > G (p.K65E) or c.764A > G (p.D255G). Modeling and protein expression revealed that both mutations might be deleterious. (4) Conclusions: The reported findings contribute to a better understanding of the SPTBN2-associated phenotype. The mutations may preclude proper structural organization of the actin spectrin-based membrane skeleton, which, in turn, is responsible for the underlying disease mechanism. Full article

(This article belongs to the Special Issue Cerebellar Ataxia)

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15 pages, 1019 KiB

Open AccessReview

Physiology of Cerebellar Reserve: Redundancy and Plasticity of a Modular Machine

by Hiroshi Mitoma, Shinji Kakei, Kazuhiko Yamaguchi and Mario Manto

Int. J. Mol. Sci. 2021, 22(9), 4777; https://doi.org/10.3390/ijms22094777 - 30 Apr 2021

Cited by 21 | Viewed by 3945

Abstract

The cerebellum is endowed with the capacity for compensation and restoration after pathological injury, a property known as cerebellar reserve. Such capacity is attributed to two unique morphological and physiological features of the cerebellum. First, mossy fibers that convey peripheral and central information [...] Read more.

The cerebellum is endowed with the capacity for compensation and restoration after pathological injury, a property known as cerebellar reserve. Such capacity is attributed to two unique morphological and physiological features of the cerebellum. First, mossy fibers that convey peripheral and central information run mediolaterally over a wide area of the cerebellum, resulting in the innervation of multiple microzones, commonly known as cerebellar functional units. Thus, a single microzone receives redundant information that can be used in pathological conditions. Secondly, the circuitry is characterized by a co-operative interplay among various forms of synaptic plasticity. Recent progress in understanding the mechanisms of redundant information and synaptic plasticity has allowed outlining therapeutic strategies potentiating these neural substrates to enhance the cerebellar reserve, taking advantage of the unique physiological properties of the cerebellum which appears as a modular and potentially reconfiguring brain structure. Full article

(This article belongs to the Special Issue Cerebellar Ataxia)

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