Epidemiology of Huntington disease

Metabolomics: An Emerging "Omics" Platform for Systems Biology and Its Implications for Huntington Disease Research

Huntington's disease (HD) is a progressive, fatal neurodegenerative disease characterized by motor, cognitive, and psychiatric symptoms. The precise mechanisms of HD progression are poorly understood; however, it is known that there is an expansion of the trinucleotide cytosine-adenine-guanine (CAG) repeat in the Huntingtin gene. Important new strategies are of paramount importance to identify early biomarkers with predictive value for intervening in disease progression at a stage when cellular dysfunction has not progressed irreversibly. Metabolomics is the study of global metabolite profiles in a system (cell, tissue, or organism) under certain conditions and is becoming an essential tool for the systemic characterization of metabolites to provide a snapshot of the functional and pathophysiological states of an organism and support disease diagnosis and biomarker discovery. This review briefly highlights the historical progress of metabolomic methodologies, followed by a more detailed review of the use of metabolomics in HD research to enable a greater understanding of the pathogenesis, its early prediction, and finally the main technical platforms in the field of metabolomics.

The Huntington's Disease Gene in an Italian Cohort of Patients with Bipolar Disorder

BACKGROUND AND OBJECTIVES

Huntington's disease (HD) is characterized by motor, cognitive and psychiatric manifestations and caused by an expansion of CAG repeats over 35 triplets on the huntingtin (HTT) gene. However, expansions in the range 27-35 repeats (intermediate allele) can be associated with pathological phenotypes. The onset of HD is conventionally defined by the onset of motor symptoms, but psychiatric disturbances can precede the motor phase by up to twenty years. The aims of the present study are to identify HD patients in the pre-motor phase of the disease among patients diagnosed with bipolar disorders and evaluate any differences between bipolar patients carrying the normal HTT allele and patients with the expanded HTT gene.

METHODS

We assessed the HTT genotype in an Italian cohort of 69 patients who were affected by either type 1 or type 2 bipolar disorder.

RESULTS

No patient was found to be a carrier of the pathological HTT allele, but 10% of bipolar subjects carried an intermediate allele. Carriers of the intermediate allele were older at the onset of psychiatric symptoms than non-carriers.

CONCLUSION

The pathological HTT gene was not associated with bipolar disorder, while we found a higher frequency of the intermediate allele among the bipolar population with respect to healthy controls. The identification of this subset of bipolar subjects has implications for the clinical management of patients and their family members and promotes further investigation into possible pathological mechanisms common to both HD and bipolar disorder.

Neuroprotective potency of mangiferin against 3-nitropropionic acid induced Huntington's disease-like symptoms in rats: possible antioxidant and anti-inflammatory mechanisms

Huntington's disease (HD), a neurodegenerative disease, normally starts in the prime of adult life, followed by a gradual occurrence of psychiatric disturbances, cognitive and motor dysfunction. The daily performances and life quality of HD patients have been severely interfered by these clinical signs and symptoms until the last stage of neuronal cell death. To the best of our knowledge, no treatment is available to completely mitigate the progression of HD. Mangiferin, a naturally occurring potent glucoxilxanthone, is mainly isolated from the Mangifera indica plant. Considerable studies have confirmed the medicinal benefits of mangiferin against memory and cognitive impairment in neurodegenerative experimental models such as Alzheimer's and Parkinson's diseases. Therefore, this study aims to evaluate the neuroprotective effect of mangiferin against 3-nitropropionic acid (3-NP) induced HD in rat models. Adult Wistar rats (n = 32) were randomly allocated equally into four groups of eight rats each: normal control (Group I), disease control (Group II) and two treatment groups (Group III and Group IV). Treatment with mangiferin (10 and 20 mg/kg, p. o.) was given for 14 days, whereas 3-NP (15 mg/kg, i. p.) was given for 7 days to induce HD-like symptoms in rats. Rats were assessed for cognitive functions and motor coordination using open field test (OFT), novel object recognition (NOR) test, neurological assessment, rotarod and grip strength tests. Biochemical parameters such as oxidative stress markers and pro-inflammatory markers in brain hippocampus, striatum and cortex regions were evaluated. Histopathological study on brain tissue was also conducted using hematoxylin and eosin (H&E) staining. 3-NP triggered anxiety, decreased recognition memory, reduced locomotor activity, lower neurological scoring, declined rotarod performance and grip strength were alleviated by mangiferin treatment. Further, a significant depletion in brain malondialdehyde (MDA) level, an increase in reduced glutathione (GSH) level, succinate dehydrogenase (SDH), superoxide dismutase (SOD) and catalase (CAT) activities, and a decrease in tumor necrosis factor-alpha (TNF-α), interleukin-1 beta (IL-1β) and interleukin-6 (IL-6) levels were observed in mangiferin treated groups. Mangiferin also mitigated 3-NP induced histopathological alteration in the brain hippocampus, striatum and cortex sections. It could be inferred that mangiferin protects the brain against oxidative damage and neuroinflammation, notably via antioxidant and anti-inflammatory activities. Mangiferin, which has a good safety profile, may be an alternate treatment option for treating HD and other neurodegenerative disorders. The results of the current research of mangiferin will open up new avenues for the development of safe and effective therapeutic agents in diminishing HD.

Huntington's Disease in Chile: Epidemiological and Genetic Aspects

INTRODUCTION

Huntington's disease (HD) is a neurodegenerative, autosomal dominant disabling condition due to an expansion of the CAG trinucleotide in the HTT gene. Motor, psychiatric, and cognitive disorders characterize it. Chilean reports on HD in the era of molecular diagnosis were wanted.

METHODS

This is a retrospective analysis of a prospective cohort of patients with HD seen at the Center for Movement Disorders (CETRAM) in Chile between 2013 and 2019. Sociodemographic, genotype, and neuropsychiatric features were investigated.

RESULTS

One hundred three probands with HD were identified. The majority (63.1%) were born in the metropolitan region, followed by the VIII and V regions with 8.73% and 7.76%, respectively. When pedigrees were analyzed, ninety unrelated families encompassing 1,007 individuals were identified; among relatives, other 35 manifested HD, and 106 died of HD. Besides, five hundred seventy-nine individuals were at genetic risk. The minimum estimated prevalence of HD in Chile in 2019 was 0.72 × 100,000 inhabitants. The mean CAG repeats (CAGR) of 47.2 ± 10.74 for the expanded allele and 17.93 ± 2.05 for the normal allele. The mean age of onset was 41.39 ± 13.47 years. Juvenile cases represented 7.8% of this cohort, and 4.9% had a late onset. There was a negative correlation between the age of onset and the CAGR of the expanded allele (r =-0.84 p < 0.0001). Besides, 79.6% had a family history of HD.

CONCLUSIONS

This is the first report characterizing genetics, motor, and neuropsychiatric features in patients with HD in Chile. The mean length of CAGR expansion of the abnormal allele was similar to previous reports in North America (i.e., Mexico and Canada) and higher than that reported in the neighboring country of Argentina. According to previous estimations, the minimal prevalence of HD in Chile may be lower than expected.

Cell Rearrangement and Oxidant/Antioxidant Imbalance in Huntington's Disease

Huntington's Disease (HD) is a hereditary neurodegenerative disorder caused by the expansion of a CAG triplet repeat in the HTT gene, resulting in the production of an aberrant huntingtin (Htt) protein. The mutant protein accumulation is responsible for neuronal dysfunction and cell death. This is due to the involvement of oxidative damage, excitotoxicity, inflammation, and mitochondrial impairment. Neurons naturally adapt to bioenergetic alteration and oxidative stress in physiological conditions. However, this dynamic system is compromised when a neurodegenerative disorder occurs, resulting in changes in metabolism, alteration in calcium signaling, and impaired substrates transport. Thus, the aim of this review is to provide an overview of the cell's answer to the stress induced by HD, focusing on the role of oxidative stress and its balance with the antioxidant system.

An Overview of Specialist Services for Huntington's Disease in the United Kingdom

BACKGROUND

Huntington's disease (HD) is a rare inherited neurodegenerative disorder characterized by complex evolving needs that change as the condition progresses. There is limited understanding about the organization of HD clinical services and their resourcing in the United Kingdom (UK).

OBJECTIVE

To understand the organization and resourcing of specialist HD services for people with HD (PwHD) in the UKMethods:This cross-sectional study collected quantitative data via on online survey, and qualitative data via telephone semi-structured interviews. Descriptive statistics were used to describe quantitative outcomes, and qualitative results were analyzed using content analysis.

RESULTS

A total of 31 specialist services for HD were identified. Of the 27 services that completed the online survey, 23 had an active multidisciplinary team of healthcare professionals (HCPs) and were led primarily by a mental health trust (26%) or tertiary referral hospital (26%). Specialist services offered outpatient clinics (96%), outreach in the community (74%), telemedicine (70%), inpatient beds (26%) and satellite clinics (26%). Many services indicated that their capacity (ability to see patients as often as needed with current resources) was difficult, with some services reporting more difficulty at the early or later stages of HD. Key resourcing gaps were identified with access to facilities, HCPs and referral networks.

CONCLUSIONS

This research highlights the variation in organization and capacity within individual HD services as well as current resourcing and gaps in access that influence this capacity. Further research should be done to understand the impact of service organization and current resourcing gaps in access on the quality of care provided for PwHD in the UK.

An Overview of Specialist Services for Huntington's Disease in the United Kingdom

BACKGROUND

Huntington's disease (HD) is a rare inherited neurodegenerative disorder characterized by complex evolving needs that change as the condition progresses. There is limited understanding about the organization of HD clinical services and their resourcing in the United Kingdom (UK).

OBJECTIVE

To understand the organization and resourcing of specialist HD services for people with HD (PwHD) in the UKMethods:This cross-sectional study collected quantitative data via on online survey, and qualitative data via telephone semi-structured interviews. Descriptive statistics were used to describe quantitative outcomes, and qualitative results were analyzed using content analysis.

RESULTS

A total of 31 specialist services for HD were identified. Of the 27 services that completed the online survey, 23 had an active multidisciplinary team of healthcare professionals (HCPs) and were led primarily by a mental health trust (26%) or tertiary referral hospital (26%). Specialist services offered outpatient clinics (96%), outreach in the community (74%), telemedicine (70%), inpatient beds (26%) and satellite clinics (26%). Many services indicated that their capacity (ability to see patients as often as needed with current resources) was difficult, with some services reporting more difficulty at the early or later stages of HD. Key resourcing gaps were identified with access to facilities, HCPs and referral networks.

CONCLUSIONS

This research highlights the variation in organization and capacity within individual HD services as well as current resourcing and gaps in access that influence this capacity. Further research should be done to understand the impact of service organization and current resourcing gaps in access on the quality of care provided for PwHD in the UK.

Expanding Arsenal against Neurodegenerative Diseases Using Quercetin Based Nanoformulations: Breakthroughs and Bottlenecks

Quercetin (Qu), a dietary flavonoid, is obtained from many fruits and vegetables such as coriander, broccoli, capers, asparagus, onion, figs, radish leaves, cranberry, walnuts, and citrus fruits. It has proven its role as a nutraceutical owing to numerous pharmacological effects against various diseases in preclinical studies. Despite these facts, Qu and its nanoparticles are less explored in clinical research as a nutraceutical. The present review covers various neuroprotective actions of Qu against various neurodegenerative diseases (NDs) such as Alzheimer's, Parkinson's, Huntington's, and Amyotrophic lateral sclerosis. A literature search was conducted to systematically review the various mechanistic pathways through which Qu elicits its neuroprotective actions and the challenges associated with raw Qu that compromise therapeutic efficacy. The nanoformulations developed to enhance Qu's therapeutic efficacy are also covered. Various ongoing/completed clinical trials related to Qu in treating various diseases, including NDs, are also tabulated. Despite these many successes, the exploration of research on Qu-loaded nanoformulations is limited mostly to preclinical studies, probably due to poor drug loading and stability of the formulation, time-consuming steps involved in the formulation, and their poor scale-up capacity. Hence, future efforts are required in this area to reach Qu nanoformulations to the clinical level.

Computational insights into missense mutations in HTT gene causing Huntington's disease and its interactome networks

BACKGROUND

Huntington's disease is a rare neurodegenerative illness of the central nervous system that is inherited in an autosomal dominant pattern. Mutant huntingtin protein is produced as a result of enlargement of CAG repeat in the N-terminal of the polyglutamine tract.

AIM OF THE STUDY

Herein, we aim to investigate the mutations and their effects on the HTT gene and its genetic variants. Additionally, the protein-protein interaction of HTT with other proteins and receptor-ligand interaction with the three-dimensional structure of huntingtin protein were identified.

METHODS

A comprehensive analysis of the HTT interactome and protein-ligand interaction has been carried out to provide a global picture of structure-function analysis of huntingtin protein. Mutations were analyzed and mutation verification tools were used to check the effect of mutation on protein function.

RESULTS

The results showed, mutations in a single gene are not only responsible for causing a particular disease but may also cause other hereditary disorders as well. Moreover, the modification at the nucleotide level also cause the change in the specific amino acid which may disrupt the function of HTT and its interacting proteins contributing in disease pathogenesis. Furthermore, the interaction between MECP2 and BDNF lowers the rate of transcriptional activity. Molecular docking further confirmed the strong interaction between MECP2 and BDNF with highest affinity. Amino acid residues of the HTT protein, involved in the interaction with tetrabenazine were N912, Y890, G2385, and V2320. These findings proved, tetrabenazine as one of the potential therapeutic agent for treatment of Huntington's disease.

CONCLUSION

These results give further insights into the genetics of Huntington's disease for a better understanding of disease models which will be beneficial for the future therapeutic studies.

Geographic Barriers Drive Disparities in Specialty Center Access for Older Adults with Huntington's Disease

BACKGROUND

Huntington's Disease Society of America Centers of Excellence (HDSA COEs) are primary hubs for Huntington's disease (HD) research opportunities and accessing new treatments. Data on the extent to which HDSA COEs are accessible to individuals with HD, particularly those older or disabled, are lacking.

OBJECTIVE

To describe persons with HD in the U.S. Medicare program and characterize this population by proximity to an HDSA COE.

METHODS

We conducted a cross-sectional study of Medicare beneficiaries ages ≥65 with HD in 2017. We analyzed data on benefit entitlement, demographics, and comorbidities. QGis software and Google Maps Interface were employed to estimate the distance from each patient to the nearest HDSA COE, and the proportion of individuals residing within 100 miles of these COEs at the state level.

RESULTS

Among 9,056 Medicare beneficiaries with HD, 54.5% were female, 83.0% were white; 48.5% were ≥65 years, but 64.9% originally qualified for Medicare due to disability. Common comorbidities were dementia (32.4%) and depression (35.9%), and these were more common in HD vs. non-HD patients. Overall, 5,144 (57.1%) lived within 100 miles of a COE. Race/ethnicity, sex, age, and poverty markers were not associated with below-average proximity to HDSA COEs. The proportion of patients living within 100 miles of a center varied from < 10% (16 states) to > 90% (7 states). Most underserved states were in the Mountain and West Central divisions.

CONCLUSION

Older Medicare beneficiaries with HD are frequently disabled and have a distinct comorbidity profile. Geographical, rather than sociodemographic factors, define the HD population with limited access to HDSA COEs.

Huntingtin Ubiquitination Mechanisms and Novel Possible Therapies to Decrease the Toxic Effects of Mutated Huntingtin

Huntington Disease (HD) is a dominant, lethal neurodegenerative disorder caused by the abnormal expansion (>35 copies) of a CAG triplet located in exon 1 of the HTT gene encoding the huntingtin protein (Htt). Mutated Htt (mHtt) easily aggregates, thereby inducing ER stress that in turn leads to neuronal injury and apoptosis. Therefore, both the inhibition of mHtt aggregate formation and the acceleration of mHtt degradation represent attractive strategies to delay HD progression, and even for HD treatment. Here, we describe the mechanism underlying mHtt degradation by the ubiquitin–proteasome system (UPS), which has been shown to play a more important role than the autophagy–lysosomal pathway. In particular, we focus on E3 ligase proteins involved in the UPS and detail their structure–function relationships. In this framework, we discuss the possible exploitation of PROteolysis TArgeting Chimeras (PROTACs) for HD therapy. PROTACs are heterobifunctional small molecules that comprise two different ligands joined by an appropriate linker; one of the ligands is specific for a selected E3 ubiquitin ligase, the other ligand is able to recruit a target protein of interest, in this case mHtt. As a consequence of PROTAC binding, mHtt and the E3 ubiquitin ligase can be brought to a relative position that allows mHtt to be ubiquitinated and, ultimately, allows a reduction in the amount of mHtt in the cell.

Myelinosome Organelles in the Retina of R6/1 Huntington Disease (HD) Mice: Ubiquitous Distribution and Possible Role in Disease Spreading

Visual deficit is one of the complications of Huntington disease (HD), a fatal neurological disorder caused by CAG trinucleotide expansions in the Huntingtin gene, leading to the production of mutant Huntingtin (mHTT) protein. Transgenic HD R6/1 mice expressing human HTT exon1 with 115 CAG repeats recapitulate major features of the human pathology and exhibit a degeneration of the retina. Our aim was to gain insight into the ultrastructure of the pathological HD R6/1 retina by electron microscopy (EM). We show that the HD R6/1 retina is enriched with unusual organelles myelinosomes, produced by retinal neurons and glia. Myelinosomes are present in all nuclear and plexiform layers, in the synaptic terminals of photoreceptors, in the processes of retinal neurons and glial cells, and in the subretinal space. In vitro study shows that myelinosomes secreted by human retinal glial Müller MIO-M1 cells transfected with EGFP-mHTT-exon1 carry EGFP-mHTT-exon1 protein, as revealed by immuno-EM and Western-blotting. Myelinosomes loaded with mHTT-exon1 are incorporated by naive neuronal/neuroblastoma SH-SY5Y cells. This results in the emergence of mHTT-exon1 in recipient cells. This process is blocked by membrane fusion inhibitor MDL 28170. Conclusion: Incorporation of myelinosomes carrying mHTT-exon1 in recipient cells may contribute to HD spreading in the retina. Exploring ocular fluids for myelinosome presence could bring an additional biomarker for HD diagnostics.

Huntington's Disease in Israel: A Population-Based Study Using 20 Years of Routinely-Collected Healthcare Data

BACKGROUND

Huntington's disease (HD) is a rare, genetic, neurodegenerative disease. Obtaining population-level data on epidemiology and disease management is challenging.

OBJECTIVE

To investigate the epidemiology, clinical manifestations, treatment, and healthcare utilization of patients with HD in Israel.

METHODS

Retrospective population-based cohort study, including 20 years of routinely collected data from Maccabi Healthcare Services, an insurer and healthcare provider for one-quarter of the Israeli population.

RESULTS

The study cohort included 109 adult patients (aged ≥18 years) diagnosed with HD, with mean age of 49.9 years and 56%females. The most common HD-related conditions were anxiety (40%), behavioral problems (34%), sleep disorders (21%), and falls (13%). Annual incidence rates for HD ranged from 0.17 to 1.34 per 100,000 from 2000 to 2018; the 2018 crude prevalence in adults was 4.36 per 100,000. Median survival from diagnosis was approximately 12 years (95%CI: 10.4-15.3). The most frequent symptomatic treatments were antidepressants (69%), antipsychotics (63%), and tetrabenazine (63%), the only drug approved for the treatment of HD chorea in Israel during the examined period. Patterns of healthcare utilization changed as disease duration increased, reflected by increased frequency of emergency department visits and home visits.

CONCLUSION

This retrospective population-based study provides insights into the prevalence, incidence, clinical profile, survival, and resource utilization of patients with HD in ethnically diverse Israel. The findings in this study are generally consistent with the international literature and demonstrate the value of routinely collected healthcare data as a complementary resource in HD research.

Revisiting cell and gene therapies in Huntington's disease

Neurodegenerative movement disorders, such as Huntington's disease (HD), share a progressive and relentless course with increasing motor disability, linked with neuropsychiatric impairment. These diseases exhibit diverse pathophysiological processes and are a topic of intense experimental and clinical research due to the lack of therapeutic options. Restorative therapies are promising approaches with the potential to restore brain circuits. However, there were less compelling results in the few clinical trials. In this review, we discuss cell replacement therapies applied to animal models and HD patients. We thoroughly describe the initial trials using fetal neural tissue transplantation and recent approaches based on alternative cell sources tested in several animal models. Stem cells were shown to generate the desired neuron phenotype and/or provide growth factors to the degenerating host cells. Besides, genetic approaches such as RNA interference and the CRISPR/Cas9 system have been studied in animal models and human-derived cells. New genetic manipulations have revealed the capability to control or counteract the effect of human gene mutations as described by the use of antisense oligonucleotides in a clinical trial. In HD, innovative strategies are at forefront of human testing and thus other brain genetic diseases may follow similar therapeutic strategies.

hiPSCs for predictive modelling of neurodegenerative diseases: dreaming the possible

Human induced pluripotent stem cells (hiPSCs) were first generated in 2007, but the full translational potential of this valuable tool has yet to be realized. The potential applications of hiPSCs are especially relevant to neurology, as brain cells from patients are rarely available for research. hiPSCs from individuals with neuropsychiatric or neurodegenerative diseases have facilitated biological and multi-omics studies as well as large-scale screening of chemical libraries. However, researchers are struggling to improve the scalability, reproducibility and quality of this descriptive disease modelling. Addressing these limitations will be the first step towards a new era in hiPSC research - that of predictive disease modelling - involving the correlation and integration of in vitro experimental data with longitudinal clinical data. This approach is a key element of the emerging precision medicine paradigm, in which hiPSCs could become a powerful diagnostic and prognostic tool. Here, we consider the steps necessary to achieve predictive modelling of neurodegenerative disease with hiPSCs, using Huntington disease as an example.

Therapeutic and Mechanistic Effects of Curcumin in Huntington's Disease

Curcumin is a spice derived nutraceutical which gained tremendous attention because of its profound medicinal values. It alters a number of molecular pathways such as nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB), signal transducer and activator of transcription 3 (STAT3), nuclear factor erythroid 2-related factor 2 (Nrf2) and cyclooxygenases-2 (COX-2), which make it potential therapeutic choice in treating multiple disorders. It also possesses the potential to prevent protein aggregation and thus protect against degeneration of neurons in neurodegenerative disorders including Huntington's disease (HD). HD is an autosomal dominant disorder linked with altered gene expression which leads to an increase in the size of cytosine, adenine and guanine (CAG) trinucleotide repeats, aids in protein aggregation throughout the brain and thus damages neurons. Upstream regulation of oxidative stress and inflammatory cascade are two important factors that drive HD progression. Available therapies just suppress the severity of symptoms with a number of side effects. Curcumin targets multiple mechanisms in treating or preventing HD including antioxidant and anti-inflammatory potential, metal ion chelation, transcriptional alterations and upregulating activity of molecular chaperons, heat shock proteins (HSPs). Having a favorable safety profile, curcumin can be an alternative therapeutic choice in treating neurodegenerative disorders like HD. This review will focus on mechanistic aspects of curcumin in treating or preventing HD and its potential to arrest disease progression and will open new dimensions for safe and effective therapeutic agents in diminishing HD.

Juvenile Huntington's disease: two case reports and a review of the literature

Background

Huntington’s disease is a rare, autosomal dominant neurodegenerative disease characterized by motor, cognitive, and psychiatric symptoms. Usually, the disease symptoms first appear around the age of 40, but in 5–10% of cases, they manifest before the age of 21. This is then referred to as juvenile Huntington’s disease. According to the small number of cases reported in the literature, the course of juvenile Huntington’s disease significantly differs from adult onset and shows significant interpatient variability, making every case unique.

Case presentation

Our study aims to highlight the complexity and diversity of rare juvenile Huntington’s disease. We report cases of two Caucasian patients with chronic tics referred to the Huntington’s Disease Competence Center of Vilnius University Hospital Santaros Klinikos with suspicion of juvenile Huntington’s disease due to the appearance of chronic motor tics, and behavior problems. The diagnosis of juvenile Huntington’s disease was confirmed on both clinical and genetic grounds. In both cases described, the patients developed symptoms in all three main groups: motor, cognitive, and psychiatric. However, the first patient was experiencing more severe psychiatric symptoms; in the second case, motor symptoms (rigidity, tremor) were more prominent. In both cases, apathy was one of the first symptoms and affected patients’ motivation to participate in treatment actively. These two case descriptions serve as an important message for clinicians seeing patients with chronic tics and gradually worsening mood and behavior, indicating the need to investigate them for rare genetic disorders.

Conclusions

Description of these two clinical cases of juvenile Huntington’s disease provides insight into how differently it manifests and progresses in young patients and the difficulties the patients and their families face. There were different but painful ways for families to accept the diagnosis. Because the disease inevitably affects the patient’s closest ones, it is crucial to also provide adequate psychological and social support to all the family members. Establishment of multidisciplinary specialist centers for Huntington’s disease, as demonstrated by our experience, not only allows timely diagnosis and treatment plans but also ensures thorough disease management and care for patients and systematic support for their families.

High frequency of intermediary alleles in the HTT gene in Northern Sweden - The Swedish Huntingtin Alleles and Phenotype (SHAPE) study

Trinucleotide (CAG) repeat expansions longer than 39 in the huntingtin (HTT) gene cause Huntington's disease (HD). The frequency of intermediate alleles (IA) with a length of 27-35 in the general population is not fully known, but studied in specific materials connected to the incidence of HD. The Swedish Huntingtin Alleles and Phenotype (SHAPE) study aims to assess the frequency of trinucleotide repeat expansions in the HTT gene in north Sweden. 8260 individuals unselected for HD from the counties of Norr- and Västerbotten in the north of Sweden were included. DNA samples were obtained and analysis of the HTT gene was performed, yielding data on HTT gene expansion length in 7379 individuals. A high frequency of intermediate alleles, 6.8%, was seen. Also, individuals with repeat numbers lower than ever previously reported (<5) were found. These results suggest a high frequency of HD in the norther parts of Sweden. Subsequent analyses may elucidate the influence of IA:s on traits other than HD.

Huntington disease: Advances in the understanding of its mechanisms

Huntington disease (HD) is a devastating monogenic autosomal dominant disorder. HD is caused by a CAG expansion in exon 1 of the gene coding for huntingtin, placed in the short arm of chromosome 4. Despite its well-defined genetic origin, the molecular and cellular mechanisms underlying the disease are unclear and complex. Here, we review some of the currently known functions of the wild-type huntingtin protein and discuss the deleterious effects that arise from the expansion of the CAG repeats, which are translated into an abnormally long polyglutamine tract.

Also, we present a modern view on the molecular biology of HD as a representative of the group of polyglutamine diseases, with an emphasis on conformational changes of mutant huntingtin, disturbances in its cellular processing, and proteolytic stress in degenerating neurons. The main pathogenetic mechanisms of neurodegeneration in HD are discussed in detail, such as autophagy, impaired mitochondrial biogenesis, lysosomal dysfunction, organelle and protein transport, inflammation, oxidative stress, and transcription factor modulation. However, other unraveling mechanisms are still unknown. This practical and brief review summarizes some of the currently known functions of the wild-type huntingtin protein and the recent findings related to the mechanisms involved in HD pathogenesis.

Live births following preimplantation genetic testing for dynamic mutation diseases by karyomapping: a report of three cases

PURPOSE

The preimplantation genetic testing for monogenic defects (PGT-M) is a beneficial strategy for the patients suffering from a Mendelian disease, which could protect their offspring from inheriting the disease. The purpose of this study is to report the effectiveness of PGT-M based on karyomapping for three cases of dynamic mutation diseases with trinucleotide repeat expansion.

METHODS

PGT-M was carried out on three couples, whose family members were diagnosed with Huntington's disease or spinocerebellar ataxias 2 or 12. The whole genome amplification was obtained using the multiple displacement amplification (MDA) method. Then, karyomapping was performed to detect the allele that is carrying the trinucleotide repeat expansion using single nucleotide polymorphism (SNP) linkage analyses, and the copy number variations (CNVs) of the embryos were also identified. Prenatal diagnosis was performed to validate the accuracy of PGT-M.

RESULTS

PGT-M was successfully performed on the three couples, and they accepted the transfers of euploid blastocysts without the relevant pathogenic allele. The clinical pregnancies were acquired and the prenatal diagnosis of the three families confirmed the effectiveness of karyomapping. The three born babies were healthy and free of the pathogenic alleles HTT, ATXN2, or PPP2R2B corresponding to Huntington's disease, spinocerebellar ataxias 2 or 12, respectively.

CONCLUSION

This study shows that karyomapping is a highly powerful and efficient approach for dynamic mutation detection in preimplantation embryos. In this work, we first report the birth of healthy babies that are free of the pathogenic gene for dynamic mutation diseases in patients receiving PGT-M by karyomapping.

Inpatient gastrostomy in Huntington's disease: Nationwide analysis of utilization and outcomes compared to amyotrophic lateral sclerosis

Background

Huntington's disease (HD) causes dysphagia and dementia, both of which are risk factors for malnutrition. Gastrostomy is used to sustain enteral intake in neurodegenerative diseases and specifically improves outcomes in ALS, but its indications and outcomes in HD are understudied.

Objective

To explore the indications and outcomes for gastrostomy for HD.

Methods

We performed a retrospective cross-sectional analysis of all HD admissions in the National Inpatient Sample. Logistic regression models compared the patient- and hospital-level characteristics associated with gastrostomy placement in HD and the prevalence of associated diagnoses in HD vs. ALS gastrostomy patients. We also examined in-hospital mortality, length of stay (LOS), and discharge status.

Results

Between 2000 and 2010, 5.12% (n = 1614) of HD admissions included gastrostomy tube placement. Gastrostomy patients were more likely to be Black (adjusted odds ratio [AOR] 1.55, 95% CI: 1.09–2.21) and have Medicare coverage (AOR 1.43, 95% CI: 1.0–2.05). The most common comorbidities were aspiration pneumonia (34.1%), dementia (31.3%), malnutrition (30.3%), and dysphagia (29.5%). Dementia and delirium were associated with discharge type but not LOS. Aspiration pneumonia, sepsis, and Elixhauser comorbidity index were associated with LOS but not discharge type. Compared to 7908 ALS gastrostomy patients, those with HD more frequently had aspiration pneumonia (34.1% vs. 20.5%, p < 0.0001), sepsis (28.1% vs. 13.7%, p < 0.0001), prolonged LOS (OR 1.14, 95% CI: 1.02–1.28), and skilled nursing facility discharge (p < 0.0001, Wald chi square test).

Conclusions

Gastrostomy is frequently performed in HD patients with dementia and aspiration pneumonia who are at increased risk for negative hospitalization outcomes.

•

More than 1,600 inpatient gastrostomies were performed for Huntington’s disease from 2000-2010 in the United States.

•

Gastrostomy is associated with aspiration pneumonia, dementia, prolonged hospitalization, hizationospital and non-routine discharge.

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Negative outcomes after gastrostomy are more common in Huntingtons disease than motor neuron disease.

Economic burden of Huntington's disease in Peru

Background

Huntington’s disease (HD) is a devastating and fatal neurodegenerative disorder that leads to progressive disability, and over time to total dependence. The economic impact of HD on patients living in developing countries like Peru is still unknown. This study aims to estimate the economic burden by estimating direct and indirect costs of Huntington’s disease in Peru, as well as the proportion of direct costs borne by patients and their families.

Methods

Disease-cost cross-sectional study where 97 participants and their primary caregivers were interviewed using a common questionnaire. Prevalence and human capital approaches were used to estimate direct and indirect costs, respectively.

Results

The average annual cost of HD reached USD 8120 per patient in 2015. Direct non-healthcare costs represented 78.3% of total cost, indirect costs 14.4% and direct healthcare costs the remaining 7.3%. The mean cost of HD increased with the degree of patient dependency: from USD 6572 for Barthel 4 & 5 (slight dependency and total independency, respectively) to USD 23,251 for Barthel 1 (total dependency). Direct costs were primarily financed by patients and their families.

Conclusions

The estimated annual cost of HD for Peruvian society reached USD 1.2 million in 2015. The cost impact of HD on patients and their families is very high, becoming catastrophic for most dependent patients, and thus making it essential to prioritize full coverage by the State.

Structural neuroimaging differentiates vulnerability from disease manifestation in colombian families with Huntington's disease

INTRODUCTION

The volume of the striatal structures has been associated with disease progression in individuals with Huntington's disease (HD) from North America, Europe, and Australia. However, it is not known whether the gray matter (GM) volume in the striatum is also sensitive in differentiating vulnerability from disease manifestation in HD families from a South-American region known to have high incidence of the disease. In addition, the association of enlarged brain perivascular spaces (PVS) with cognitive, behavioral, and motor symptoms of HD is unknown.

MATERIALS AND METHODS

We have analyzed neuroimaging indicators of global atrophy, PVS burden, and GM tissue volume in the basal ganglia and thalami, in relation to behavioral, motor, and cognitive scores, in 15 HD patients with overt disease manifestation and 14 first-degree relatives not genetically tested, which represent a vulnerable group, from the region of Magdalena, Colombia.

RESULTS

Poor fluid intelligence as per the Raven's Standard Progressive Matrices was associated with global brain atrophy (p = 0.002) and PVS burden (p ≤ 0.02) in HD patients, where the GM volume in all subcortical structures, with the exception of the right globus pallidus, was associated with motor or cognitive scores. Only the GM volume in the right putamen was associated with envy and MOCA scores (p = 0.008 and 0.015 respectively) in first-degree relatives.

CONCLUSION

Striatal GM volume, global brain atrophy and PVS burden may serve as differential indicators of disease manifestation in HD. The Raven's Standard Progressive Matrices could be a cognitive test worth to consider in the differentiation of vulnerability versus overt disease in HD.

Design and characterization of mutant and wildtype huntingtin proteins produced from a toolkit of scalable eukaryotic expression systems

The gene mutated in individuals with Huntington's disease (HD) encodes the 348-kDa huntingtin (HTT) protein. Pathogenic HD CAG-expansion mutations create a polyglutamine (polyQ) tract at the N terminus of HTT that expands above a critical threshold of ∼35 glutamine residues. The effect of these HD mutations on HTT is not well understood, in part because it is difficult to carry out biochemical, biophysical, and structural studies of this large protein. To facilitate such studies, here we have generated expression constructs for the scalable production of HTT in multiple eukaryotic expression systems. Our set of HTT expression clones comprised both N- and C-terminally FLAG-tagged HTT constructs with polyQ lengths representative of the general population, HD patients, and juvenile HD patients, as well as the more extreme polyQ expansions used in some HD tissue and animal models. Our expression system yielded milligram quantities of pure recombinant HTT protein, including many of the previously mapped post-translational modifications. We characterized both apo and HTT-HTT-associated protein 40 (HAP40) complex samples produced with this HD resource, demonstrating that this toolkit can be used to generate physiologically meaningful HTT complexes. We further demonstrate that these resources can produce sufficient material for protein-intensive experiments, such as small-angle X-ray scattering, providing biochemical insight into full-length HTT protein structure. The work outlined and the tools generated here lay a foundation for further biochemical and structural work on the HTT protein and for studying its functional interactions with other biomolecules.

A Pipeline to Assess Disease-Associated Haplotypes in Repeat Expansion Disorders: The Example of MJD/SCA3 Locus

At least 40 human diseases are associated with repeat expansions; yet, the mutational origin and instability mechanisms remain unknown for most of them. Previously, genetic epidemiology and predisposing backgrounds for the instability of some expanding loci have been studied in different populations through the analysis of diversity flanking the respective pathogenic repeats. Here, we aimed at developing a pipeline to assess disease-associated haplotypes at oligonucleotide repeat loci, combining analysis of single nucleotide polymorphisms (SNPs) and short tandem repeats (STRs). Machado-Joseph disease (MJD/SCA3), the most frequent dominant ataxia worldwide, was used as an example of a detailed procedure. Thus, to identify genetic backgrounds that segregate with expanded/mutated alleles in MJD, we selected a set of 26 SNPs and 7 STRs flanking the causative CAG repeat. Key criteria and steps for this selection are described, and included (1) haplotype blocks minimizing the occurrence of recombination (for SNPs); and (2) match scores to increase potential for polymorphic information content of repetitive sequences found in Tandem Repeats Finder (for STRs). To directly assess SNP haplotypes in phase with MJD expansions, we optimized a strategy with preferential amplification of normal over expanded alleles, in addition to SNP allele-specific amplifications; this allowed the identification of disease-associated SNP haplotypes, even when only the proband is available in a given family. To infer STR haplotypes, we optimized a multiplex PCR, including 7 STRs plus the MJD_CAG repeat, followed by analysis of segregation or the use of the PHASE software. This protocol is a ready-to-use tool to assess MJD haplotypes in different populations. The pipeline designed can be used to assess disease-associated haplotypes in other repeat-expansion diseases. This should be of great utility to study (1) genetic epidemiology (population-of-origin, age and spreading routes of mutations) and (2) mechanisms responsible for de novo expansions, in these neurological diseases; (3) to detect predisposing haplotypes and (4) phenotype modifiers; (5) to help solving cases of apparent homoallelism (two same-size normal alleles) in diagnosis; and (6) to identify the best targets for the development of allele-specific therapies in ethnically diverse patient populations.

Empathy In Neurodegenerative Diseases: A Systematic Review

INTRODUCTION

Empathy, in its affective and cognitive components, is a crucial interpersonal ability. It is broadly studied in the field of psychopathology, whereas its study in the neurodegenerative diseases is relatively recent. Existing literature, though, focused on a reduced subset of considered diseases, which often found a compromise in empathy abilities. Organized knowledge about a more comprehensive set of diseases is lacking.

METHOD

The present PRISMA systematic review was aimed at collecting the current available literature concerning empathic alterations in adult patients affected by neurodegenerative diseases. It considered the different empathy components, evaluated existing patterns, the impact on patients' lives, and treatment considerations.

RESULTS

Overall, the 32 retrieved studies describe a spread deterioration of empathic abilities in patients, with each disease displaying its own pattern of empathy functioning. Literature in this field is fragmented and of heterogeneous quality, and further studies are warranted to increase evidence of many preliminary results.

DISCUSSION

In conclusion, we highlight the crucial importance of acknowledging empathy deficits in these diseases, showing their repercussion on both patients' and caregivers' quality of life, the establishment of a functional doctor-patient relationship, and the development of efficacious psychological intervention. These clinical approaches can be enriched by the knowledge of the spared abilities of patients affected by neurodegenerative diseases.

Polyglutamine Repeats in Neurodegenerative Diseases

Among the age-dependent protein aggregation disorders, nine neurodegenerative diseases are caused by expansions of CAG repeats encoding polyglutamine (polyQ) tracts. We review the clinical, pathological, and biological features of these inherited disorders. We discuss insights into pathogenesis gleaned from studies of model systems and patients, highlighting work that informs efforts to develop effective therapies. An important conclusion from these analyses is that expanded CAG/polyQ domains are the primary drivers of neurodegeneration, with the biology of carrier proteins influencing disease-specific manifestations. Additionally, it has become apparent that CAG/polyQ repeat expansions produce neurodegeneration via multiple downstream mechanisms, involving both gain- and loss-of-function effects. This conclusion indicates that the likelihood of developing effective therapies targeting single nodes is reduced. The evaluation of treatments for premanifest disease will likely require new investigational approaches. We highlight the opportunities and challenges underlying ongoing work and provide recommendations related to the development of symptomatic and disease-modifying therapies and biomarkers that could inform future research.

Proteostasis in Huntington's disease: disease mechanisms and therapeutic opportunities

Many neurodegenerative diseases are characterized by impairment of protein quality control mechanisms in neuronal cells. Ineffective clearance of misfolded proteins by the proteasome, autophagy pathways and exocytosis leads to accumulation of toxic protein oligomers and aggregates in neurons. Toxic protein species affect various cellular functions resulting in the development of a spectrum of different neurodegenerative proteinopathies, including Huntington's disease (HD). Playing an integral role in proteostasis, dysfunction of the ubiquitylation system in HD is progressive and multi-faceted with numerous biochemical pathways affected, in particular, the ubiquitin-proteasome system and autophagy routes for protein aggregate degradation. Unravelling the molecular mechanisms involved in HD pathogenesis of proteostasis provides new insight in disease progression in HD as well as possible therapeutic avenues. Recent developments of potential therapeutics are discussed in this review.