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Neurology. Genetics Jun 2024Exome sequencing (ES) demonstrates a 20-50 percent diagnostic yield for patients with a suspected monogenic neurologic disease. Despite the proven efficacy in achieving...
BACKGROUND AND OBJECTIVES
Exome sequencing (ES) demonstrates a 20-50 percent diagnostic yield for patients with a suspected monogenic neurologic disease. Despite the proven efficacy in achieving a diagnosis for such patients, multiple barriers for obtaining exome sequencing remain. This study set out to assess the efficacy of ES in patients with primary neurologic phenotypes who were appropriate candidates for testing but had been unable to pursue clinical testing.
METHODS
A total of 297 patients were identified from the UCLA Clinical Neurogenomics Research Center Biobank, and ES was performed, including bioinformatic assessment of copy number variation and repeat expansions. Information regarding demographics, clinical indication for ES, and reason for not pursuing ES clinically were recorded. To assess diagnostic efficacy, variants were interpreted by a multidisciplinary team of clinicians, bioinformaticians, and genetic counselors in accordance with the American College of Medical Genetics and Genomics variant classification guidelines. We next examined the specific barriers to testing for these patients, including how frequently insurance-related barriers such as coverage denials and inadequate coverage of cost were obstacles to pursuing exome sequencing.
RESULTS
The cohort primarily consisted of patients with sporadic conditions (n = 126, 42.4%) of adult-onset (n = 239, 80.5%). Cerebellar ataxia (n = 225, 75.8%) was the most common presenting neurologic phenotype. Our study found that in this population of mostly adult patients with primary neurologic phenotypes that were unable to pursue exome sequencing clinically, 47 (15.8%) had diagnostic results while an additional 24 patients (8.1%) had uncertain results. Of the 297 patients, 206 were initially recommended for clinical exome but 88 (42.7%) could not pursue ES because of insurance barriers, of whom 14 (15.9%) had diagnostic findings, representing 29.8% of all patients with diagnostic findings. In addition, the incorporation of bioinformatic repeat expansion testing was valuable, identifying a total of 8 pathogenic repeat expansions (17.0% of all diagnostic findings) including 3 of the common spinocerebellar ataxias and 2 patients with Huntington disease.
DISCUSSION
These findings underscore the importance and value of clinical ES as a diagnostic tool for neurogenetic disease and highlight key barriers that prevent patients from receiving important clinical information with potential treatment and psychosocial implications for patients and family members.
PubMed: 38617022
DOI: 10.1212/NXG.0000000000200133 -
International Journal of Molecular... Apr 2024The spinocerebellar ataxias (SCA) comprise a group of inherited neurodegenerative diseases. Machado-Joseph Disease (MJD) or spinocerebellar ataxia 3 (SCA3) is the most... (Review)
Review
The spinocerebellar ataxias (SCA) comprise a group of inherited neurodegenerative diseases. Machado-Joseph Disease (MJD) or spinocerebellar ataxia 3 (SCA3) is the most common autosomal dominant form, caused by the expansion of CAG repeats within the ataxin-3 (ATXN3) gene. This mutation results in the expression of an abnormal protein containing long polyglutamine (polyQ) stretches that confers a toxic gain of function and leads to misfolding and aggregation of ATXN3 in neurons. As a result of the neurodegenerative process, SCA3 patients are severely disabled and die prematurely. Several screening approaches, e.g., druggable genome-wide and drug library screenings have been performed, focussing on the reduction in stably overexpressed ATXN3(polyQ) protein and improvement in the resultant toxicity. Transgenic overexpression models of toxic ATXN3, however, missed potential modulators of endogenous ATXN3 regulation. In another approach to identify modifiers of endogenous expression using a CRISPR/Cas9-modified SK-N-SH wild-type cell line with a -- () cassette under the control of the endogenous promotor, four statins were identified as potential activators of expression. We here provide an overview of the high throughput screening approaches yet performed to find compounds or genomic modifiers of ATXN3(polyQ) toxicity in different SCA3 model organisms and cell lines to ameliorate and halt SCA3 progression in patients. Furthermore, the putative role of cholesterol in neurodegenerative diseases (NDDs) in general and SCA3 in particular is discussed.
Topics: Humans; Animals; Machado-Joseph Disease; Translational Research, Biomedical; Spinocerebellar Ataxias; Translational Science, Biomedical; Animals, Genetically Modified
PubMed: 38612794
DOI: 10.3390/ijms25073984 -
Revue Neurologique May 2024Genetic cerebellar ataxias are still a diagnostic challenge, and yet not all of them have been identified. Very recently, in early 2023, a new cause of late-onset... (Review)
Review
Genetic cerebellar ataxias are still a diagnostic challenge, and yet not all of them have been identified. Very recently, in early 2023, a new cause of late-onset cerebellar ataxia (LOCA) was identified, spinocerebellar ataxia 27B (SCA27B). This is an autosomal dominant ataxia due to a GAA expansion in intron 1 of the FGF14 gene. Thanks to the many studies carried out since its discovery, it is now possible to define the clinical phenotype, its particularities, and the progression of SCA27B. It has also been established that it is one of the most frequent causes of LOCA. The core phenotype of the disease consists of slowly progressive late-onset ataxia with cerebellar syndrome, oculomotor disorders including downbeat nystagmus, and episodic symptoms such as diplopia. Therapeutic approaches have been proposed, including acetazolamide, and 4-aminopyridine, the latter with a better benefit/tolerance profile.
Topics: Humans; Spinocerebellar Ataxias; Age of Onset; Cerebellar Ataxia; Fibroblast Growth Factors; Spinocerebellar Degenerations
PubMed: 38609751
DOI: 10.1016/j.neurol.2024.03.007 -
Scientific Reports Apr 2024This study emphasizes the benefits of open-source software such as DeepLabCut (DLC) and R to automate, customize and enhance data analysis of motor behavior. We recorded...
This study emphasizes the benefits of open-source software such as DeepLabCut (DLC) and R to automate, customize and enhance data analysis of motor behavior. We recorded 2 different spinocerebellar ataxia type 6 mouse models while performing the classic beamwalk test, tracked multiple body parts using the markerless pose-estimation software DLC and analyzed the tracked data using self-written scripts in the programming language R. The beamwalk analysis script (BAS) counts and classifies minor and major hindpaw slips with an 83% accuracy compared to manual scoring. Nose, belly and tail positions relative to the beam, as well as the angle at the tail base relative to the nose and tail tip were determined to characterize motor deficits in greater detail. Our results found distinct ataxic abnormalities such as an increase in major left hindpaw slips and a lower belly and tail position in both SCA6 ataxic mouse models compared to control mice at 18 months of age. Furthermore, a more detailed analysis of various body parts relative to the beam revealed an overall lower body position in the SCA6 compared to the CT-longQ27 mouse line at 18 months of age, indicating a more severe ataxic deficit in the SCA6 group.
Topics: Animals; Mice; Ataxia; Spinocerebellar Ataxias; Data Analysis; Disease Models, Animal; Nose
PubMed: 38609436
DOI: 10.1038/s41598-024-59187-0 -
Heliyon Apr 2024The differentiation of spinocerebellar ataxia type II (SCA 2) from idiopathic multiple systemic atrophy of the cerebellar type (MSA-C) is often difficult in patients...
BACKGROUND AND OBJECTIVES
The differentiation of spinocerebellar ataxia type II (SCA 2) from idiopathic multiple systemic atrophy of the cerebellar type (MSA-C) is often difficult in patients with cerebellar ataxia when molecular testing is not available. Besides genetic testing, magnetic resonance imagining (MRI) and magnetic resonance spectroscopy (MRS) prove to be beneficial. Nevertheless, the characteristics observed through radiology change as the disease advances. Different radiological criteria may be needed across different stages of the disease. This study aimed to assess the radiological characteristics of MSA-C or SCA 2 patients across various stages of the disease and to identify potential distinguishing factors.
METHODS
Between January 2000 and January 2020, a total of 390 patients, diagnosed with probable MSA-C according to the second consensus on MSA (317 cases) or with molecularly confirmed SCA 2 (73 cases), who had undergone at least one brain MRI and MRS targeting the cerebellar hemispheres, were enrolled in the study. The clinical parameters and neuroimaging features between these two diseases were compared and analyzed.
RESULTS
A greater occurrence of a pontine hot cross bun sign (HCBS), higher scores on the scale for the assessment and rating of ataxia, and reduced levels of cerebellar N-acetyl aspartate (NAA)/creatine (Cr), and cerebellar choline (Cho)/Cr were found in MSA-C patients as compared with SCA 2 patients at similar disease durations. For the patients with an HCBS, a cerebellar Cho/Cr level of <0.53 was indicative of the potential presence of MSA-C, with significant level of specificity (85.96%).
DISCUSSION
Discerning SCA2 from MSA-C using MRI and MRS appears to be plausible at various disease stages.
PubMed: 38601670
DOI: 10.1016/j.heliyon.2024.e29265 -
Communications Biology Apr 2024Better understanding of the earliest molecular pathologies of all neurodegenerative diseases is expected to improve human therapeutics. We investigated the earliest...
Better understanding of the earliest molecular pathologies of all neurodegenerative diseases is expected to improve human therapeutics. We investigated the earliest molecular pathology of spinocerebellar ataxia type 1 (SCA1), a rare familial neurodegenerative disease that primarily induces death and dysfunction of cerebellum Purkinje cells. Extensive prior studies have identified involvement of transcription or RNA-splicing factors in the molecular pathology of SCA1. However, the regulatory network of SCA1 pathology, especially central regulators of the earliest developmental stages and inflammatory events, remains incompletely understood. Here, we elucidated the earliest developmental pathology of SCA1 using originally developed dynamic molecular network analyses of sequentially acquired RNA-seq data during differentiation of SCA1 patient-derived induced pluripotent stem cells (iPSCs) to Purkinje cells. Dynamic molecular network analysis implicated histone genes and cytokine-relevant immune response genes at the earliest stages of development, and revealed relevance of ISG15 to the following degradation and accumulation of mutant ataxin-1 in Purkinje cells of SCA1 model mice and human patients.
Topics: Animals; Humans; Mice; Cytokines; Induced Pluripotent Stem Cells; Mice, Transgenic; Purkinje Cells; Spinocerebellar Ataxias; Ubiquitins
PubMed: 38594382
DOI: 10.1038/s42003-024-06066-z -
Brain Communications 2024Genetic repeat expansions cause neuronal degeneration in amyotrophic lateral sclerosis as well as other neurodegenerative disorders such as spinocerebellar ataxia,...
Genetic repeat expansions cause neuronal degeneration in amyotrophic lateral sclerosis as well as other neurodegenerative disorders such as spinocerebellar ataxia, Huntington's disease and Kennedy's disease. Repeat expansions in the same gene can cause multiple clinical phenotypes. We aimed to characterize repeat expansions in a Norwegian amyotrophic lateral sclerosis cohort. Norwegian amyotrophic lateral sclerosis patients ( = 414) and neurologically healthy controls adjusted for age and gender ( = 713) were investigated for repeat expansions in , , and using short read exome sequencing and the ExpansionHunter software. Five amyotrophic lateral sclerosis patients (1.2%) and two controls (0.3%) carried ≥36 repeats in ( = 0.032), and seven amyotrophic lateral sclerosis patients (1.7%) and three controls (0.4%) carried ≥29 repeats in ( = 0.038). One male diagnosed with amyotrophic lateral sclerosis carried a pathogenic repeat expansion in , and his diagnosis was revised to Kennedy's disease. In , 50 amyotrophic lateral sclerosis patients (12.1%) and 96 controls (13.5%) carried ≥33 repeats ( = 0.753). None of the patients with repeat expansions in or had signs of Huntington's disease or spinocerebellar ataxia type 2, based on a re-evaluation of medical records. The diagnosis of amyotrophic lateral sclerosis was confirmed in all patients, with the exception of one patient who had primary lateral sclerosis. Our findings indicate that repeat expansions in and are associated with increased likelihood of developing amyotrophic lateral sclerosis. Further studies are required to investigate the potential relationship between repeat expansions and amyotrophic lateral sclerosis.
PubMed: 38585669
DOI: 10.1093/braincomms/fcae087 -
Revue Neurologique May 2024Spinocerebellar ataxia type 3 (SCA3), also known as Machado-Joseph disease, is a neurodegenerative disease caused by expanded polyglutamine repeats in exon 10 of the... (Review)
Review
Spinocerebellar ataxia type 3 (SCA3), also known as Machado-Joseph disease, is a neurodegenerative disease caused by expanded polyglutamine repeats in exon 10 of the ataxin-3 gene, ATXN3. The accumulation of mutant ATXN3 protein leads to severe clinical manifestations and premature death. Clinically, SCA3 pathology is characterized by progressive ataxia leading to motor incoordination that may affect balance, gait and speech, and neuropathologically by a progressive degeneration of the spinal cord and cerebellum, as well as the cerebral cortex and basal ganglia. Although SCA3 is a rare disease, it is the most common autosomal dominant spinocerebellar ataxia worldwide. Its geographical distribution varies worldwide, with peak prevalence in certain regions of Brazil, Portugal and China. In 1994, the identification of the polyglutamine expansion in the ATXN3 gene made it possible not only to diagnose this pathology but also to dissect the mechanisms leading to cellular degeneration. As a monogenic disease for which only symptomatic treatment is available, the ATXN3 gene represents an attractive therapeutic target for gene editing strategies.
Topics: Humans; Machado-Joseph Disease; Ataxin-3; Gene Editing; Genetic Therapy; Animals; Repressor Proteins
PubMed: 38580500
DOI: 10.1016/j.neurol.2024.03.003 -
Neurobiology of Disease Jun 2024We performed a comprehensive study of the morphological, functional, and genetic features of moonwalker (MWK) mice, a mouse model of spinocerebellar ataxia caused by a...
We performed a comprehensive study of the morphological, functional, and genetic features of moonwalker (MWK) mice, a mouse model of spinocerebellar ataxia caused by a gain of function of the TRPC3 channel. These mice show numerous behavioral symptoms including tremor, altered gait, circling behavior, impaired motor coordination, impaired motor learning and decreased limb strength. Cerebellar pathology is characterized by early and almost complete loss of unipolar brush cells as well as slowly progressive, moderate loss of Purkinje cell (PCs). Structural damage also includes loss of synaptic contacts from parallel fibers, swollen ER structures, and degenerating axons. Interestingly, no obvious correlation was observed between PC loss and severity of the symptoms, as the phenotype stabilizes around 2 months of age, while the cerebellar pathology is progressive. This is probably due to the fact that PC function is severely impaired much earlier than the appearance of PC loss. Indeed, PC firing is already impaired in 3 weeks old mice. An interesting feature of the MWK pathology that still remains to be explained consists in a strong lobule selectivity of the PC loss, which is puzzling considering that TRPC is expressed in every PC. Intriguingly, genetic analysis of MWK cerebella shows, among other alterations, changes in the expression of both apoptosis inducing and resistance factors possibly suggesting that damaged PCs initiate specific cellular pathways that protect them from overt cell loss.
Topics: Animals; Mice; Disease Models, Animal; Phenotype; Cerebellum; Purkinje Cells; TRPC Cation Channels; Genotype; Spinocerebellar Ataxias; Mice, Neurologic Mutants; Mice, Inbred C57BL; Mice, Transgenic
PubMed: 38575093
DOI: 10.1016/j.nbd.2024.106492 -
Memantine suppresses the excitotoxicity but fails to rescue the ataxic phenotype in SCA1 model mice.Biomedicine & Pharmacotherapy =... May 2024Spinocerebellar ataxia type 1 (SCA1) is a debilitating neurodegenerative disorder of the cerebellum and brainstem. Memantine has been proposed as a potential treatment...
Spinocerebellar ataxia type 1 (SCA1) is a debilitating neurodegenerative disorder of the cerebellum and brainstem. Memantine has been proposed as a potential treatment for SCA1. It blocks N-methyl-D-aspartate (NMDA) receptors on neurons, reduces excitotoxicity and decreases neurodegeneration in Alzheimer models. However, in cerebellar neurodegenerative diseases, the potential value of memantine is still unclear. We investigated the effects of memantine on motor performance and synaptic transmission in the cerebellum in a mouse model where mutant ataxin 1 is specifically targeted to glia. Lentiviral vectors (LVV) were used to express mutant ataxin 1 selectively in Bergmann glia (BG). In mice transduced with the mutant ataxin 1, chronic treatment with memantine improved motor activity during initial tests, presumably due to preserved BG and Purkinje cell (PC) morphology and numbers. However, mice were unable to improve their rota rod scores during next days of training. Memantine also compromised improvement in the rota rod scores in control mice upon repetitive training. These effects may be due to the effects of memantine on plasticity (LTD suppression) and NMDA receptor modulation. Some effects of chronically administered memantine persisted even after its wash-out from brain slices. Chronic memantine reduced morphological signs of neurodegeneration in the cerebellum of SCA1 model mice. This resulted in an apparent initial reduction of ataxic phenotype, but memantine also affected cerebellar plasticity and ultimately compromised motor learning. We speculate that that clinical application of memantine in SCA1 might be hampered by its ability to suppress NMDA-dependent plasticity in cerebellar cortex.
Topics: Animals; Memantine; Disease Models, Animal; Spinocerebellar Ataxias; Phenotype; Mice; Ataxin-1; Motor Activity; Cerebellum; Purkinje Cells; Receptors, N-Methyl-D-Aspartate; Mice, Transgenic; Mice, Inbred C57BL; Neuroglia; Male; Neuronal Plasticity
PubMed: 38574621
DOI: 10.1016/j.biopha.2024.116526