scholarly journals Molecular Mechanisms of Polyglutamine Pathology and Lessons Learned from Huntington’s Disease

2021 ◽  
Author(s):  
Nagehan Ersoy Tunalı
Keyword(s):  
Huntington's Disease ◽  
Huntington’S Disease ◽  
Molecular Mechanisms ◽  
Lessons Learned ◽  
Trinucleotide Repeats ◽  
Cag Repeat ◽  
Cag Repeats ◽  
Disease Genes ◽  
Polyq Diseases ◽  
Dynamic Mutations

Identification of polymorphic repeating units on DNA as a cause of many neurological disorders has introduced a new concept in molecular biology: Dynamic mutations. Many of the identified dynamic mutations involve expansion of trinucleotide repeats within disease genes. Nine neurodegenerative disorders are currently known to be caused by expanding CAG trinucleotide repeats. These are Huntington’s Disease (HD), Dentato-Rubral Pallidoluysian Atrophy (DRPLA), Spinal and Bulbar Muscular Atrophy (SBMA), and Spinocerebellar Ataxia (SCA) Type 1, 2, 3, 6, 7 and 17. All are inherited in an autosomal dominant fashion except for SBMA, which is X-linked recessive. In all polyQ diseases, the disease mutation involves an increase in the number of CAG repeats within the coding regions of the respective genes. Since CAG triplets encode glutamine in the proteins, diseases caused by CAG repeat expansions are known as “Polyglutamine (polyQ) Diseases”. PolyQ diseases share certain clinical, neuropathological and molecular findings. The most widely studied polyQ disease is HD. In HD and other polyQ diseases, conformational change in the mutant protein causes abnormal folding and proteolysis of the protein, leading to the formation of a toxic polyQ fragment, which aggregates and causes neuronal dysfunction and selective neuronal death in the brain.

scholarly journals Juvenile Huntington’s Disease and Other PolyQ Diseases, Update on Neurodevelopmental Character and Comparative Bioinformatic Review of Transcriptomic and Proteomic Data

2021 ◽  
Vol 9 ◽  
Author(s):  
Karolina Świtońska-Kurkowska ◽  
Bart Krist ◽  
Joanna Delimata ◽  
Maciej Figiel
Keyword(s):  
Huntington's Disease ◽  
Huntington’S Disease ◽  
Mouse Models ◽  
Muscular Atrophy ◽  
Expression Patterns ◽  
Cag Repeat ◽  
Human Cognition ◽  
Expression Data ◽  
Neuronal Stem Cell ◽  
Polyq Diseases

Polyglutamine (PolyQ) diseases are neurodegenerative disorders caused by the CAG repeat expansion mutation in affected genes resulting in toxic proteins containing a long chain of glutamines. There are nine PolyQ diseases: Huntington’s disease (HD), spinocerebellar ataxias (types 1, 2, 3, 6, 7, and 17), dentatorubral-pallidoluysian atrophy (DRPLA), and spinal bulbar muscular atrophy (SBMA). In general, longer CAG expansions and longer glutamine tracts lead to earlier disease presentations in PolyQ patients. Rarely, cases of extremely long expansions are identified for PolyQ diseases, and they consistently lead to juvenile or sometimes very severe infantile-onset polyQ syndromes. In apparent contrast to the very long CAG tracts, shorter CAGs and PolyQs in proteins seems to be the evolutionary factor enhancing human cognition. Therefore, polyQ tracts in proteins can be modifiers of brain development and disease drivers, which contribute neurodevelopmental phenotypes in juvenile- and adult-onset PolyQ diseases. Therefore we performed a bioinformatics review of published RNAseq polyQ expression data resulting from the presence of polyQ genes in search of neurodevelopmental expression patterns and comparison between diseases. The expression data were collected from cell types reflecting stages of development such as iPSC, neuronal stem cell, neurons, but also the adult patients and models for PolyQ disease. In addition, we extended our bioinformatic transcriptomic analysis by proteomics data. We identified a group of 13 commonly downregulated genes and proteins in HD mouse models. Our comparative bioinformatic review highlighted several (neuro)developmental pathways and genes identified within PolyQ diseases and mouse models responsible for neural growth, synaptogenesis, and synaptic plasticity.

scholarly journals The MID1 Protein: A Promising Therapeutic Target in Huntington’s Disease

2021 ◽  
Vol 12 ◽  
Author(s):  
Annika Heinz ◽  
Judith Schilling ◽  
Willeke van Roon-Mom ◽  
Sybille Krauß
Keyword(s):  
Huntington's Disease ◽  
Huntington’S Disease ◽  
Protein A ◽  
Cag Repeat ◽  
Cag Repeats ◽  
Progressive Movement ◽  
Promising Therapeutic Target ◽  
Promising Therapeutic Approach ◽  
Exon 1 ◽  
Polyglutamine Protein

Huntington’s disease (HD) is caused by an expansion mutation of a CAG repeat in exon 1 of the huntingtin (HTT) gene, that encodes an expanded polyglutamine tract in the HTT protein. HD is characterized by progressive psychiatric and cognitive symptoms associated with a progressive movement disorder. HTT is ubiquitously expressed, but the pathological changes caused by the mutation are most prominent in the central nervous system. Since the mutation was discovered, research has mainly focused on the mutant HTT protein. But what if the polyglutamine protein is not the only cause of the neurotoxicity? Recent studies show that the mutant RNA transcript is also involved in cellular dysfunction. Here we discuss the abnormal interaction of the mutant HTT transcript with a protein complex containing the MID1 protein. MID1 aberrantly binds to CAG repeats and this binding increases with CAG repeat length. Since MID1 is a translation regulator, association of the MID1 complex stimulates translation of mutant HTT mRNA, resulting in an overproduction of polyglutamine protein. Thus, blocking the interaction between MID1 and mutant HTT mRNA is a promising therapeutic approach. Additionally, we show that MID1 expression in the brain of both HD patients and HD mice is aberrantly increased. This finding further supports the concept of blocking the interaction between MID1 and mutant HTT mRNA to counteract mutant HTT translation as a valuable therapeutic strategy. In line, recent studies in which either compounds affecting the assembly of the MID1 complex or molecules targeting HTT RNA, show promising results.

scholarly journals Predicting Disease Onset from Mutation Status Using Proband and Relative Data with Applications to Huntington's Disease

2012 ◽  
Vol 2012 ◽  
pp. 1-19 ◽  
Author(s):  
Tianle Chen ◽  
Yuanjia Wang ◽  
Yanyuan Ma ◽  
Karen Marder ◽  
Douglas R. Langbehn
Keyword(s):  
Huntington's Disease ◽  
Huntington’S Disease ◽  
Family Member ◽  
Disease Onset ◽  
Repeat Length ◽  
Cag Repeat ◽  
Cag Repeats ◽  
Observational Research ◽  
Accurate Estimation ◽  
Combined Data

Huntington's disease (HD) is a progressive neurodegenerative disorder caused by an expansion of CAG repeats in the IT15 gene. The age-at-onset (AAO) of HD is inversely related to the CAG repeat length and the minimum length thought to cause HD is 36. Accurate estimation of the AAO distribution based on CAG repeat length is important for genetic counseling and the design of clinical trials. In the Cooperative Huntington's Observational Research Trial (COHORT) study, the CAG repeat length is known for the proband participants. However, whether a family member shares the huntingtin gene status (CAG expanded or not) with the proband is unknown. In this work, we use the expectation-maximization (EM) algorithm to handle the missing huntingtin gene information in first-degree family members in COHORT, assuming that a family member has the same CAG length as the proband if the family member carries a huntingtin gene mutation. We perform simulation studies to examine performance of the proposed method and apply the methods to analyze COHORT proband and family combined data. Our analyses reveal that the estimated cumulative risk of HD symptom onset obtained from the combined data is slightly lower than the risk estimated from the proband data alone.

scholarly journals Molecular mediators, environmental modulators and experience-dependent synaptic dysfunction in Huntington's disease.

2004 ◽  
Vol 51 (2) ◽  
pp. 415-430 ◽  
Author(s):  
Anthony J Hannan
Keyword(s):  
Neurodegenerative Diseases ◽  
Huntington's Disease ◽  
Huntington’S Disease ◽  
Environmental Enrichment ◽  
Molecular Mechanisms ◽  
Psychiatric Symptoms ◽  
Brain Regions ◽  
Cag Repeat ◽  
Autosomal Dominant Disorder ◽  
Gene Environment

Huntington's disease (HD) is an autosomal dominant disorder in which there is progressive neurodegeneration producing motor, cognitive and psychiatric symptoms. HD is caused by a trinucleotide (CAG) repeat mutation, encoding an expanded polyglutamine tract in the huntingtin protein. At least eight other neurodegenerative diseases are caused by CAG/glutamine repeat expansions in different genes. Recent evidence suggests that environmental factors can modify the onset and progression of Huntington's disease and possibly other neurodegenerative disorders. This review outlines possible molecular and cellular mechanisms mediating the polyglutamine-induced toxic 'gain of function' and associated gene-environment interactions in HD. Key aspects of pathogenesis shared with other neurodegenerative diseases may include abnormal protein-protein interactions, selective disruption of gene expression and 'pathological plasticity' of synapses in specific brain regions. Recent discoveries regarding molecular mechanisms of pathogenesis are guiding the development of new therapeutic approaches. Knowledge of gene-environment interactions, for example, could lead to development of 'enviromimetics' which mimic the beneficial effects of specific environmental stimuli. The effects of environmental enrichment on brain and behaviour will also be discussed, together with the general implications for neuroscience research involving animal models.

scholarly journals Parkinsonism with a Hint of Huntington’s from 29 CAG Repeats in HTT

2019 ◽  
Vol 9 (10) ◽  
pp. 245
Author(s):  
Sipilä JOT
Keyword(s):  
Huntington's Disease ◽  
Huntington’S Disease ◽  
Clinical Phenotype ◽  
Cag Repeat ◽  
Cag Repeats ◽  
Test Results ◽  
Intermediate Allele ◽  
History Of ◽  
Neurophysiological Test ◽  
History Of Parkinson’S Disease

Huntington’s disease is caused by at least 36 cytosine-adenine-guanine (CAG) repeats in an HTT gene allele, but repeat tracts in the intermediate range (27–35 repeats) also display a subtle phenotype. This patient had a slightly elongated CAG repeat tract (29 repeats), a prominent family history of Parkinson’s disease (PD), and a clinical phenotype mostly consistent with PD, but early dystonia and poor levodopa response. Neurophysiological test results were more consistent with Huntington’s disease (HD) than PD. It is suggested that the intermediate allele modulated the clinical phenotype of PD in this patient.

Molecular Mechanisms and Potential Therapeutical Targets in Huntington's Disease

2010 ◽  
Vol 90 (3) ◽  
pp. 905-981 ◽  
Author(s):  
Chiara Zuccato ◽  
Marta Valenza ◽  
Elena Cattaneo
Keyword(s):  
Huntington's Disease ◽  
Huntington’S Disease ◽  
Molecular Mechanisms ◽  
Neurodegenerative Disorder ◽  
Disease Process ◽  
Primary Source ◽  
Cag Repeat ◽  
Mutant Protein ◽  
Loss Of Function ◽  
Causative Gene

Huntington's disease (HD) is a neurodegenerative disorder caused by a CAG repeat expansion in the gene encoding for huntingtin protein. A lot has been learned about this disease since its first description in 1872 and the identification of its causative gene and mutation in 1993. We now know that the disease is characterized by several molecular and cellular abnormalities whose precise timing and relative roles in pathogenesis have yet to be understood. HD is triggered by the mutant protein, and both gain-of-function (of the mutant protein) and loss-of-function (of the normal protein) mechanisms are involved. Here we review the data that describe the emergence of the ancient huntingtin gene and of the polyglutamine trait during the last 800 million years of evolution. We focus on the known functions of wild-type huntingtin that are fundamental for the survival and functioning of the brain neurons that predominantly degenerate in HD. We summarize data indicating how the loss of these beneficial activities reduces the ability of these neurons to survive. We also review the different mechanisms by which the mutation in huntingtin causes toxicity. This may arise both from cell-autonomous processes and dysfunction of neuronal circuitries. We then focus on novel therapeutical targets and pathways and on the attractive option to counteract HD at its primary source, i.e., by blocking the production of the mutant protein. Strategies and technologies used to screen for candidate HD biomarkers and their potential application are presented. Furthermore, we discuss the opportunities offered by intracerebral cell transplantation and the likely need for these multiple routes into therapies to converge at some point as, ideally, one would wish to stop the disease process and, at the same time, possibly replace the damaged neurons.

scholarly journals The timing and impact of psychiatric, cognitive and motor abnormalities in Huntington's disease

2020 ◽  
Author(s):  
Branduff McAllister ◽  
James F. Gusella ◽  
G. Bernhard Landwehrmeyer ◽  
Jong-Min Lee ◽  
Marcy E. MacDonald ◽  
...  
Keyword(s):  
Huntington's Disease ◽  
Huntington’S Disease ◽  
Clinical Characteristics ◽  
Negative Impact ◽  
Cag Repeat ◽  
Cag Repeats ◽  
Motor Symptoms ◽  
Cognitive Symptoms ◽  
Cognitive Symptom ◽  
Motor Abnormalities

Objective: To assess the prevalence, timing and functional impact of psychiatric, cognitive and motor abnormalities in Huntington's disease (HD), we analysed retrospective clinical data from individuals with manifest HD. Methods: Clinical features of HD patients were analysed for 6316 individuals in the European REGISTRY study from 161 sites across 17 countries. Data came from clinical history and the Clinical Characteristics Questionnaire that assessed eight symptoms: motor, cognitive, apathy, depression, perseverative/obsessive behavior, irritability, violent/aggressive behavior, and psychosis. Multiple logistic regression was used to analyse relationships between symptoms and functional outcomes. Results: The initial manifestation of HD is increasingly likely to be motor, and less likely to be psychiatric, as age at presentation increases. The nature of the first manifestation is not associated with pathogenic CAG repeat length. Symptom prevalence data from the patient-completed Clinical Characteristics Questionnaire correlate specifically with validated clinical measures. Using these data, we show that psychiatric and cognitive symptoms are common in HD, with earlier onsets associated with longer CAG repeats. 42.4% of HD patients reported at least one psychiatric or cognitive symptom before motor symptoms, with depression most common. Apathy and cognitive impairment tend to come later in the disease course. Each psychiatric or cognitive symptom was associated with significantly reduced total functional capacity scores. Conclusions: Psychiatric and cognitive symptoms occur before motor symptoms in many more HD patients than previously reported. They have a greater negative impact on daily life than involuntary movements and should be specifically targeted with clinical outcome measures and treatments.

scholarly journals Genomic architecture differences at the HTT locus associated with symptomatic and pre-symptomatic cases of Huntington’s disease in a pilot study

2021 ◽  
pp. 1-6
Author(s):  
Matthew Salter ◽  
Ryan Powell ◽  
Jennifer Back ◽  
Francis Grand ◽  
Christina Koutsothanasi ◽  
...  
Keyword(s):  
Huntington's Disease ◽  
Huntington’S Disease ◽  
Clinical Symptoms ◽  
Disease Onset ◽  
Cag Repeat ◽  
Cag Repeats ◽  
Healthy Controls ◽  
Chromosome Conformation ◽  
Chromatin Architecture ◽  
Patient Groups

Huntington’s Disease (HD) is a progressive neurodegenerative condition that causes degeneration of neurons in the brain, ultimately leading to death. The root cause of HD is an expanded trinucleotide Cytosine-Adenine-Guanine (CAG) repeat in the “huntingtin gene” (HTT). While there is a rough correlation between the number of CAG repeats and disease onset, the development of clinical symptoms can vary by decades within individuals and little is known about this presymptomatic phase. Using peripheral blood samples from HD patients and healthy controls we used EpiSwitch®, a validated high-resolution industrial platform for the detection of chromosome conformations, to assess chromatin architecture in the immediate vicinity of the HTT gene. We evaluated chromatin conformations at 20 sites across 225 kb of the HTT locus in a small cohort of healthy controls, verified symptomatic HD patients (CAG, n>39) and patients with CAG expansions who had not yet manifested clinical symptoms of HD. Discrete chromosome conformations were observed across the patient groups. We found two constitutive interactions (occurring in all patient groups) and seven conditional interactions which were present in HD, but not in healthy controls. Most important, we observed three conditional interactions that were present only in HD patients manifesting clinical symptoms (symptomatic cases), but not in presymptomatic cases. 85% (6 out of 7) of the patients in the symptomatic HD cohort demonstrated at least one of the specific chromosome conformations associated with symptomatic HD. Our results provide the first evidence that chromatin architecture at the HTT locus is systemically altered in patients with HD, with conditional differences between clinical stages. Given the high clinical need in having a molecular tool to assess disease progression in HD, these results strongly suggest that the non-invasive assessment of Chromosome Conformation Signatures (CCS) warrant further study as a prognostic tool in HD.

scholarly journals Genomic architecture differences at the HTT locus underlie symptomatic and pre-symptomatic cases of Huntington’s disease.

F1000Research ◽  
2019 ◽  
Vol 7 ◽  
pp. 1757
Author(s):  
Matthew Salter ◽  
Ryan Powell ◽  
Jennifer Back ◽  
Francis Grand ◽  
Christina Koutsothanasi ◽  
...  
Keyword(s):  
Huntington's Disease ◽  
Huntington’S Disease ◽  
Clinical Symptoms ◽  
Disease Onset ◽  
Cag Repeat ◽  
Cag Repeats ◽  
Healthy Controls ◽  
Chromosome Conformation ◽  
Chromatin Architecture ◽  
Patient Groups

Background:Huntington’s disease (HD) is a progressive neurodegenerative condition that causes degeneration of neurons in the brain, ultimately leading to death. The root cause of HD is an expanded trinucleotide cytosine-adenine-guanine (CAG) repeat in the “huntingtin gene” (HTT). While there is a rough correlation between the number of CAG repeats and disease onset, the development of clinical symptoms can vary by decades within individuals and little is known about this pre-symptomatic phase.Methods:Using peripheral blood samples from HD patients and healthy controls we usedEpiSwitch™, a validated high-resolution industrial platform for the detection of chromosome conformations, to assess chromatin architecture in the immediate vicinity of theHTTgene. We evaluated chromatin conformations at 20 sites across 225 kb of theHTTlocus in healthy controls, verified symptomatic HD patients (CAG, n>39) and patients with CAG expansions who had not yet manifested clinical symptoms of HD.Results:Discrete chromosome conformations were observed across the patient groups. We found two constitutive interactions (occurring in all patient groups) and seven conditional interactions which were present in HD, but not in healthy controls. Most important, we observed three conditional interactions that were present only in HD patients manifesting clinical symptoms (symptomatic cases), but not in presymptomatic cases. Of the patients in the symptomatic HD cohort, 86% (6 out of 7) demonstrated at least one of the specific chromosome conformations associated with symptomatic HD.Conclusion:Our results provide the first evidence that chromatin architecture at theHTTlocus is systemically altered in patients with HD, with conditional differences between clinical stages. Given the high clinical need in having a molecular tool to assess disease progression in HD, these results strongly suggest that the non-invasive assessment of chromosome conformation signatures can be a valuable addition to prognostic assessment of HD patients.

Huntington’s Disease

2008 ◽  
Author(s):  
Adam Rosenblatt
Keyword(s):  
Huntington's Disease ◽  
Movement Disorder ◽  
Huntington’S Disease ◽  
Neurodegenerative Disorder ◽  
Age Of Onset ◽  
Cag Repeat ◽  
Cag Repeats ◽  
Triplet Repeat Expansion ◽  
Common Time ◽  
The Individual

Huntington’s disease (HD) is a hereditary neurodegenerative disorder characterized by the triad of a movement disorder, dementia, and various psychiatric disturbances. HD is caused by the abnormal expansion of a trinucleotide (CAG) repeat in the huntingtin gene of chromosome 4—a mutation that is inherited as an autosomal dominant. When the number of CAG repeats exceeds 39, the individual harboring it goes on to develop HD. The most common time of onset is in the fourth or fifth decade, but the age of onset is inversely correlated with the size of the triplet repeat expansion. In rare instances, persons with very large expansions may have onset in childhood, and those with expansions only just into the abnormal range may have onset late in life. Children of affected fathers, if they receive the abnormal allele, tend to inherit an allele that is even further expanded, and thus usually experience the onset of symptoms at a younger age than their fathers; this phenomenon is known as paternal anticipation. The progression of HD is inexorable and usually leads to death within 15 to 20 years of symptom onset; patients in the final stages have severe dementia and are unable to speak, eat, or purposefully move. Death typically results from the consequences of immobility such as pneumonia or malnutrition. The movement disorder of HD has two major manifestations: involuntary movements (eg, chorea, dystonia) and impairments of voluntary movement (eg, clumsiness, dysarthria, swallowing difficulties, falls, bradykinesia, rigidity). Chorea generally predominates early in the course and is gradually eclipsed by motor impairment as the disease becomes more advanced. In the end stages, patients are rigid and immobile. A variety of medications are used to suppress chorea in HD, including neuroleptics, benzodiazepines, and dopamine-depleting agents such as tetrabenazine, but it remains controversial whether these agents convey functional, as opposed to cosmetic, benefits. HD, like many other neurodegenerative disorders, is associated with a variety of psychiatric problems. Some of these problems such as insomnia or demoralization may be thought of as nonspecific. They have a variety of causes and are associated with many different medical conditions.

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