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Biomedical subjects

Sarah J Tabrizi

Publications and source records attributed to Sarah J Tabrizi.

16 recordsLinked to original sources
PubMed2025

Antisense oligonucleotide-mediated MSH3 suppression reduces somatic CAG repeat expansion in Huntington's disease iPSC-derived striatal neurons.

Expanded CAG alleles in the huntingtin (HTT) gene that cause the neurodegenerative disorder Huntington's disease (HD) are genetically unstable and continue to expand somatically throughout life, driving HD onset and progression. MSH3, a DNA mismatch repair protein, modifies HD onset and progression by driving this somatic CAG repeat expansion process. MSH3 is relatively tolerant of loss-of-function variation in humans, making it a potential therapeutic target. Here, we show that an MSH3-targeting antisense oligonucleotide (ASO) effectively engaged with its RNA target in induced pluripotent stem cell (iPSC)-derived striatal neurons obtained from a patient with HD carrying 125 HTT CAG repeats (the 125 CAG iPSC line). ASO treatment led to a dose-dependent reduction of MSH3 and subsequent stalling of CAG repeat expansion in these striatal neurons. Bulk RNA sequencing revealed a safe profile for MSH3 reduction, even when reduced by >95%. Maximal knockdown of MSH3 also effectively slowed CAG repeat expansion in striatal neurons with an otherwise accelerated expansion rate, derived from the 125 CAG iPSC line where FAN1 was knocked out by CRISPR-Cas9 editing. Last, we created a knock-in mouse model expressing the human MSH3 gene and demonstrated effective in vivo reduction in human MSH3 after ASO treatment. Our study shows that ASO-mediated MSH3 reduction can prevent HTT CAG repeat expansion in HD 125 CAG iPSC-derived striatal neurons, highlighting the therapeutic potential of this approach.

Huntington Disease↗
PubMed2025

Generation of C9orf72 repeat knock-in iPSC lines for modelling ALS and FTD.

Induced pluripotent stem cell (iPSC) models are powerful tools for neurodegenerative disease modelling, as they allow mechanistic studies in a human genetic environment and they can be differentiated into a range of neuronal and non-neuronal cells. However, these models come with inherent challenges due to line-to-line and clonal variability. To combat this issue, the iPSC Neurodegenerative Disease Initiative (iNDI) has generated an iPSC repository using a single clonal reference line, KOLF2.1J, into which disease-causing mutations and revertants are introduced via gene editing. Here we describe the generation and validation of lines carrying the most common causative mutation for amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD), a repeat expansion in the C9orf72 gene, for the iNDI collection of neurodegenerative iPSC models. We demonstrate that these C9orf72 knock-in lines differentiate efficiently into neurons and display characteristic C9orf72-associated pathologies, including reduced C9orf72 levels and the presence of dipeptide repeat proteins (DPRs) and RNA foci, which increase in abundance over time in culture. These pathologies are not present in revertant cells lacking the repeat expansion. These repeat expansion and revertant cell lines are now available to academic and for-profit institutions through the JAX iPS cell repository and will help to facilitate and standardise iPSC-based ALS/FTD research.

Journal Article↗
PubMed2006

Progressive alterations in the hypothalamic-pituitary-adrenal axis in the R6/2 transgenic mouse model of Huntington's disease.

Huntington's disease (HD) is characterized by a triad of motor, psychiatric and cognitive symptoms. Although many of these symptoms are likely to be related to central nervous system pathology, others may be due to changes in peripheral tissues. The R6/2 mouse, a transgenic model of HD expressing exon 1 of the human HD gene, develops progressive alterations in the hypothalamic-pituitary-adrenal axis, reminiscent of a Cushing-like syndrome. We observed muscular atrophy, reduced bone mineral density, abdominal fat accumulation and insulin resistance in the mice. All these changes could be consequences of increased glucocorticoid levels. Indeed, hypertrophy of the adrenal cortex and a progressive increase in serum and urine corticosterone levels were found in R6/2 mice. In addition, the intermediate pituitary lobe was markedly enlarged and circulating adreno-corticotrophic hormone (ACTH) increased. Under normal conditions dopamine represses the ACTH expression. In the R6/2 mice, however, the expression of pituitary dopamine D2 receptors was reduced by half, possibly explaining the increase in ACTH. Urinary samples from 82 HD patients and 68 control subjects were analysed for cortisol: in accord with the observations in the R6/2 mice, urinary cortisol increased in parallel with disease progression. This progressive increase in cortisol may contribute to the clinical symptoms, such as muscular wasting, mood changes and some of the cognitive deficits that occur in HD.

Adrenocorticotropic Hormone↗
PubMed2006

The application of NMR-based metabonomics in neurological disorders.

Advances in postgenomic technologies have radically changed the information output from complex biological systems, generating vast amounts of high complexity data that can be interpreted by means of chemometric and bioinformatic methods to achieve disease diagnosis and prognosis. High-resolution nuclear magnetic resonance (NMR) spectroscopy of biofluids such as plasma, cerebrospinal fluid (CSF), and urine can generate robust, interpretable metabolic fingerprints that contain latent information relating to physiological or pathological status. This technology has been successfully applied to both preclinical and clinical studies of neurodegenerative diseases such as Huntington's disease, muscular dystrophy, and cerebellar ataxia. An extension of this technology, (1)H magic-angle-spinning (HRMAS) NMR spectroscopy, can be used to generate metabolic information on small intact tissue samples, providing a metabolic link between metabolic profiling of biofluids and histology. In this review we provide a summary of high-resolution NMR studies in neurodegenerative disease and explore the potential of metabonomics in evaluating disease progression with respect to therapeutic intervention.

Animals↗
PubMed2006

Metabolic characterization of the R6/2 transgenic mouse model of Huntington's disease by high-resolution MAS 1H NMR spectroscopy.

The metabolic consequences of Huntington's disease in the R6/2 mouse model were investigated using NMR spectroscopy and pattern recognition to characterize selected brain regions, muscle, blood, and urine. Global increases in relative brain concentrations of osmolytes, creatine, glutamine, and lactate, and decreases in acetate and N-acetylaspartate were found together with striatal-specific lower concentrations of GABA and choline. Clear differentiation of R6/2 and wild-type mice was also obtained for urine and blood metabolite profiles that may have applicability for monitoring HD in human populations.

Animals↗
PubMed2005

Disease-related prion protein forms aggresomes in neuronal cells leading to caspase activation and apoptosis.

The molecular basis for neuronal death in prion disease is not established, but putative pathogenic roles for both disease-related prion protein (PrP(Sc)) and accumulated cytosolic PrP(C) have been proposed. Here we report that only prion-infected neuronal cells become apoptotic after mild inhibition of the proteasome, and this is strictly dependent upon sustained propagation of PrP(Sc). Whereas cells overexpressing PrP(C) developed cytosolic PrP(C) aggregates, this did not cause cell death. In contrast, only in prion-infected cells, mild proteasome impairment resulted in the formation of large cytosolic perinuclear aggresomes that contained PrP(Sc), heat shock chaperone 70, ubiquitin, proteasome subunits, and vimentin. Similar structures were found in the brains of prion-infected mice. PrP(Sc) aggresome formation was directly associated with activation of caspase 3 and 8, resulting in apoptosis. These data suggest that neuronal propagation of prions invokes a neurotoxic mechanism involving intracellular formation of PrP(Sc) aggresomes. This, in turn, triggers caspase-dependent apoptosis and further implicates proteasome dysfunction in the pathogenesis of prion diseases.

Acetylcysteine↗
PubMed2005

Gene expression in Huntington's disease skeletal muscle: a potential biomarker.

Huntington's disease (HD) is an incurable and fatal neurodegenerative disorder. Improvements in the objective measurement of HD will lead to more efficient clinical trials and earlier therapeutic intervention. We hypothesized that abnormalities seen in the R6/2 mouse, a greatly accelerated HD model, might highlight subtle phenotypes in other mouse models and human HD. In this paper, we identify common gene expression changes in skeletal muscle from R6/2 mice, Hdh(CAG(150)) homozygous knock-in mice and HD patients. This HD-triggered gene expression phenotype is consistent with the beginnings of a transition from fast-twitch to slow-twitch muscle fiber types. Metabolic adaptations similar to those induced by diabetes or fasting are also present but neither metabolic disorder can explain the full phenotype of HD muscle. The HD-induced gene expression changes reflect disease progression. This raises the possibility that muscle gene expression may be used as an objective biomarker to complement clinical HD-rating systems. Furthermore, an understanding of the molecular basis of muscle dysfunction in HD should provide insight into mechanisms involved in neuronal abnormalities and neurodegeneration.

Animals↗
PubMed2005

Spinocerebellar ataxia type 17: extension of phenotype with putaminal rim hyperintensity on magnetic resonance imaging.

We report on a 50-year-old woman who presented with an 8-year history of involuntary movements, unsteadiness, and cognitive decline. Examination revealed multidomain cognitive deficits, jerky ocular pursuit movements, hypometric saccades, gaze impersistence, dysarthria, upper limb dystonia, and widespread chorea. TATA-binding protein gene test revealed trinucleotide expansion allele sizes of 47 and 39 repeats, confirming the diagnosis of spinocerebellar ataxia type 17 (SCA-17). Magnetic resonance imaging (MRI) showed marked cerebellar atrophy and putaminal rim hyperintensity. This is the first case of SCA-17 reported to show MRI signal change in the basal ganglia, and extends the phenotypic manifestation of SCA-17.

Cognition Disorders↗
PubMed2005

Biomarkers for neurodegenerative diseases.

PURPOSE OF REVIEW: A major goal of current clinical research in neurodegenerative diseases is to improve early detection of disease and presymptomatic detection of neuronal dysfunction. We also need better tools to assess disease progression in this group of disorders. Currently, many potential disease-modifying therapies are being developed and evaluated at the preclinical stage, and will lead to clinical trials in the near future for which biomarkers are urgently needed. This review summarizes the field of biomarker research in the major neurodegenerative diseases. RECENT FINDINGS: Many different approaches are being undertaken to identify biomarkers and include imaging, neurophysiological and cognitive testing in addition to newer technologies such as biochemical, proteomic, metabanomic and gene array profiling of tissue and biofluids from patients. Key recent findings in each of these areas are discussed. SUMMARY: The ideal biomarker needs to be easy to quantify and measure, reproducible, not subject to wide variation in the general population and unaffected by co-morbid factors. For evaluation of therapies the biomarker needs to change linearly with disease progression and closely correlate with established clinico-pathological parameters of the disease. It is unlikely that any one biomarker will fulfil all these characteristics, and it is likely that more than one biomarker will be needed for early diagnosis and similarly for evaluation of disease progression for therapeutic trials. For example, the combination of more detailed clinical assessments encompassing specific cognitive and neurophysiological testing, in addition to imaging, biochemical and genomic profiling, is likely to be needed.

Animals↗
PubMed2004

Somatic and germline mosaicism in sporadic early-onset Alzheimer's disease.

Alzheimer's disease (AD) is the commonest neurodegenerative disease worldwide. Rare familial cases may be caused by mutations in one of three genes-amyloid precursor protein, presenilin-1 and presenilin-2; however, the molecular basis of >99% of AD cases is unknown. Somatic mutation has been considered to be a mechanism that may account for a proportion of sporadic cases of AD, but to date there has been no evidence for this. We now report a sporadic early-onset patient with AD, and show that this individual is a somatic mosaic for a mutation in the presenilin-1 gene, suggesting a novel molecular mechanism for AD. Quantification of the mosaicism demonstrated the degree of mosaicism at 8% in peripheral lymphocytes and 14% in cerebral cortex in the index patient; a clear gene dosage effect on age of presentation and clinical phenotypic presentation is demonstrated. This finding has important implications for the aetiology of sporadic AD, and for other apparently sporadic neurodegenerative diseases such as Parkinson's disease, motor neuron disease and Creutzfeldt-Jakob disease.

Adult↗
PubMed2003

Models of Parkinson's disease.

Parkinson's disease (PD) is a heterogenous disease likely to be caused by more than one specific aetiological factor. In rare familial cases of PD with similar clinical features to the idiopathic form of the disease, the underlying genetic cause has been identified. These PD-associated genes have been manipulated to create animal and cell culture models of the disease that have helped to further our understanding of the pathogenesis of PD, particularly concerning causes of the selective loss of dopaminergic neurons at the molecular level. In addition, these models will aid the future development of rational therapeutic strategies. This study briefly reviews toxin-induced models and the genetics of PD. It focuses on recently developed animal models of PD, as well as in vitro approaches to model the disease.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗
PubMed2003

Prion diseases.

Prion diseases are incurable neurodegenerative conditions affecting both animals and humans. They may be sporadic, infectious, or inherited in origin. Human prion diseases include Creutzfeldt-Jakob desease (CJD), Gerstmann-Straussler-Scheinker disease, kuru, and fatal familial insomnia. The appearance of variant CJD, and the demonstration that is caused by strains indistinguishable from bovine spongiform encephalopathy (BSE) in cattle, has led to the threat of a major epidemic of human prion disease in the UK and other countries where widespread dietary exposure to bovine prions has occurred. This article reviews the history and epidemiology of these diseases, and then focuses on important areas of current research in human prion disorders.

Animals↗
PubMed2003

Mouse models as a tool for understanding neurodegenerative diseases.

PURPOSE OF REVIEW: The purpose of this review is to present recent advances in the both the creation and the use of mouse models of human neurodegenerative disease. We briefly touch on the technologies used to make these models, and then focus on recent results from new models. We discuss why such models are useful when they do - and do not - mimic the human disorder. RECENT FINDINGS: The numbers of mouse models are increasing dramatically and are starting to yield important results for human disease. We present a selection of new and important models and the results of recent investigations of these animals. SUMMARY: An accepted protocol when studying any form of human neurodegenerative disease is to investigate the genetics, pathology, neurophysiology, response to therapeutics, etc., of the disorder in the mouse. This approach is clearly bearing fruit for our understanding and treatment of human neurodegeneration.

Animals↗
PubMed2002

Mouse models for neurological disease.

The mouse has many advantages over human beings for the study of genetics, including the unique property that genetic manipulation can be routinely carried out in the mouse genome. Most importantly, mice and human beings share the same mammalian genes, have many similar biochemical pathways, and have the same diseases. In the minority of cases where these features do not apply, we can still often gain new insights into mouse and human biology. In addition to existing mouse models, several major programmes have been set up to generate new mouse models of disease. Alongside these efforts are new initiatives for the clinical, behavioural, and physiological testing of mice. Molecular genetics has had a major influence on our understanding of the causes of neurological disorders in human beings, and much of this has come from work in mice.

Animals↗
PubMedDate not supplied

Idiopathic intimal hyperplasia of small arteries and arterioles affecting intestines and myocardium.

We report the case of a 52-year-old woman dying from a noninflammatory, occlusive vasculopathy. Histology showed marked intimal hyperplasia of small arteries of the intestines and myocardium with subsequent infarction of myocardium, large intestine and gallbladder. A comprehensive work up including laboratory studies, clinical investigations and postmortem failed to assign this condition to any of the known vascular diseases.

Arterioles↗