Huntington’s disease (HD) is caused by a trinucleotide CAG repeat in the huntingtin gene (HTT) that results in expression of a polyglutamine-expanded mutant huntingtin protein (mHTT). N-terminal fragments of mHTT accumulate in brain neurons and glia as soluble monomeric and oligomeric species as well as insoluble protein aggregates and drive the disease process. Decreasing mHTT levels in brain provides protection and reversal of disease signs in HD mice making mHTT a prime target for disease modification. There is evidence for aberrant thiol oxidation within mHTT and other proteins in HD models. Based on this, we hypothesized that a specific thiol-disulfide oxidoreductase exists that decreases mHTT levels in cells and provides protection in HD mice. We undertook an in-vitro genetic screen of key thiol-disulfide oxidoreductases then completed secondary screens to identify those with mHTT decreasing properties. Our in-vitro experiments identified thioredoxin 1 and thioredoxin-related transmembrane protein 3 as proteins that decrease soluble mHTT levels in cultured cells. Using a lentiviral mouse model of HD we tested the effect of these proteins in striatum. Both proteins decreased mHTT-induced striatal neuronal atrophy. Findings provide evidence for a role of dysregulated protein-thiol homeostasis in the pathogenesis of HD.
Background: Recently a profound depletion of cystathionine γ-lyase (CSE), the principal enzyme involved in the generation of cysteine from cystathionine, was shown in Huntington disease (HD) patients and several transgenic HD mouse models. We therefore hypothesized that blood and urine cystathionine levels may be increased in HD patients and that this increase might correlate with disease progression. Methods: We measured concentrations of cystathionine as well as 22 other amino acids in fasting plasma and 24-h urine samples of nine early-stage HD patients and nine age, sex, and body mass index matched controls. Results: There were no significant differences in the plasma or urine concentrations of cystathionine or any other amino acid between HD patients and controls. Conclusion: We found no evidence for changes in plasma or urine concentrations of cystathionine in early-stage HD patients. Therefore, cystathionine levels are unlikely to be useful as a state biomarker in HD.
Background: We investigated the use of a simple novel nut and bolt task in premanifest and manifest Huntington’s disease (HD) patients to detect and quantify motor impairments at all stages of the disease.
Methods: Premanifest HD (n=24), manifest HD (n=27) and control (n=32) participants were asked to screw a nut onto a bolt in one direction, using three different sized bolts with their left and right hand in turn.
Results: We identified some impairments at all stages of HD and in the premanifest individuals, deficits in the non-dominant hand correlated with disease burden scores.
Conclusion: This simple, cheap motor task was able to detect motor impairments in both premanifest and manifest HD and as such might be a useful quantifiable measure of motor function for use in clinical studies.
Weight loss is an important complication of Huntington’s disease (HD), however the mechanism for weight loss in HD is not entirely understood. Mutant huntingtin is expressed in the gastrointestinal (GI) tract and, in HD mice, mutant huntingtin inclusions are found within the enteric nervous system along the GI tract. A reduction of neuropeptides, decreased mucosal thickness and villus length, as well as gut motility impairment, have also been shown in HD mice. We therefore set out to study gastric mucosa of patients with HD, looking for abnormalities of mucosal cells using immunohistochemistry. In order to investigate possible histological differences related to gastric acid production, we evaluated the cell density of acid producing parietal cells, as well as gastrin producing cells (the endocrine cell controlling parietal cell function). In addition, we looked at chief cells and somatostatin-containing cells. In gastric mucosa from HD subjects, compared to control subject biopsies, a reduced expression of gastrin (a marker of G cells) was found. This is in line with previous HD mouse studies showing reduction of GI tract neuropeptides.
Objective: To assess effects of a two year intensive, multidisciplinary rehabilitation program for patients with early- to mid-stage Huntington’s disease.
Design: A prospective intervention study.
Setting: One inpatient rehabilitation center in Norway.
Subjects: 10 patients, with early- to mid-stage Huntington’s disease.
Interventions: A two year rehabilitation program, consisting of six admissions of three weeks each, and two evaluation stays approximately three months after the third and sixth rehabilitation admission. The program focused on physical exercise, social activities, and group/teaching sessions.
Main outcome measures: Standard measures for motor function, including gait and balance, cognitive function, including MMSE and UHDRS cognitive assessment, anxiety and depression, activities of daily living (ADL), health related quality of life (QoL) and Body Mass Index (BMI).
Results: Six out of ten patients completed the full program. Slight, but non-significant, decline was observed for gait and balance from baseline to the evaluation stay after two years. Non-significant improvements were observed in physical QoL, anxiety and depression, and BMI. ADL-function remained stable with no significant decline. None of the cognitive measures showed a significant decline. An analysis of individual cases revealed that four out of the six participants who completed the program sustained or improved their motor function, while motor function declined in two participants. All the six patients who completed the program reported improved or stable QoL throughout the study period.
Conclusion: Our findings suggest that participation in an intensive rehabilitation program is well tolerated among motivated patients with early to mid-stage HD. The findings should be interpreted with caution due to the small sample size in this study.
We have previously reported the genetic correction of Huntington’s disease (HD) patient-derived induced pluripotent stem cells using traditional homologous recombination (HR) approaches. To extend this work, we have adopted a CRISPR-based genome editing approach to improve the efficiency of recombination in order to generate allelic isogenic HD models in human cells. Incorporation of a rapid antibody-based screening approach to measure recombination provides a powerful method to determine relative efficiency of genome editing for modeling polyglutamine diseases or understanding factors that modulate CRISPR/Cas9 HR.
Objective: To assess the effects of an intensive, multidisciplinary rehabilitation program for patients with early to mid-stage Huntington’s disease.
Design: A prospective intervention study.
Setting: Two Norwegian inpatient rehabilitation centers.
Subjects: 37 patients, with early- to midstage Huntington’s disease
Interventions: A one year rehabilitation program, consisting of three admissions of three weeks each, and a five-day evaluation stay approximately 3 months after the last rehabilitation admission. Focus was on physical exercise, social activities, and group/teaching sessions. There was also emphasis to implement of coordinated health care and social services for the patients.
Main outcome measures: standard measures for motor function, including gait and balance, cognitive function, including MMSE and UHDRS cognitive assessment, anxiety and depression, activities of daily living (ADL), health related quality of life and Body Mass Index (BMI).
Results: Significant improvements were observed in gait function, balance, in physical quality of life, anxiety and depression, as well as in BMI. ADL-function remained stable with no significant decline. Only one cognitive measure (SDMT) showed significant decline, while no decline was observed for the remaining cognitive measures.
Conclusion: A multidisciplinary intensive rehabilitation program in patients with early and mid stage HD is associated with improved balance, gait function, physical quality of life and with reduced depressive and anxiety symptoms. Longer follow-up is needed to assess if these positive effects are sustained. There should be emphasis to establishment of long term and coordinated health care services for the HD patient
Background: Longer CAG repeat length is associated with faster clinical progression in Huntington disease, although the effect of higher repeat length on brain atrophy is not well documented. Method: Striatal volumes were obtained from MRI scans of 720 individuals with prodromal Huntington disease. Striatal volume was plotted against age separately for groups with CAG repeat lengths of 38-39, 40, 41, 42, 43, 44, 45, 46, and 47-54. Results: Slopes representing the association between age and striatal volume were significantly steeper as CAG repeat length increased. Discussion: Although cross-sectional, these data suggest that striatal atrophy, like clinical progression, may occur faster with higher CAG repeat lengths.
Background: People with Huntington’s disease (HD) often require tailored healthcare and support packages that develop as the disease progresses. The Client Service Receipt Inventory (CSRI) gathers retrospective information on service utilization. This study investigated the use of formal services and informal care as measured by the CSRI and explored associations between informal care, disease severity and functional ability as measured by the Unified Huntington’s Disease Rating Scale Total Motor Score (UHDRS-TMS) and functional scales.
Methods: All monitored longitudinal data from annual clinical assessments of UHDRS-TMS and functional assessments and CSRI collected under the auspices of the European Huntington’s Disease Network (EHDN) REGISTRY study between the years 2004 and 2009 were utilised in the analyses. Disease severity was reflected by UHDRS-TMS. Functional ability was measured using the UHDRS functional scales. CSRI data were analysed according to percentage use of individual formal services and total estimated hours per week of informal care. Regression analyses were conducted to identify any associations between disease severity, functional ability and hours of informal care.
Results: 451 HD patients (212 female; 239 male) completed one visit; 105 patients (54 females; 51 males) completed two visits and 47 patients (20 females; 27 males) completed three visits in total over the 5 year period. The mean time between visits was 1.2 years. At visit one, 74% of the participants reported being in receipt of at least one formal hospital-based service in the previous six months, and 89% reported receipt of formal primary and community care services. In contrast, at the third visit, 62% of people had used hospital based services and 94% formal community based services in the previous six months. Fifty % of individuals required some form of informal care in the home at visit 1; this increased to 68% at visits 2 and 3. The mean (SD) estimated weekly total informal care hours at visits 1, 2 and 3 were 32.8 (49.4); 21.6 (53.6) and 21.3 (62.4) respectively. Only the scores on the Functional Assessment Scale (FAS) accounted for the variance in the weekly total informal care hours at each visit.
Conclusions: Although it must be acknowledged that service use is supply driven, most HD patients across Europe surveyed as part of this study were in receipt of formal primary and community care services and to a lesser extent formal hospital based services. There was however a large reliance on informal care in the home. The FAS appear to have predictive value on informal care requirements and may have utility in facilitating pro-active service provision and in particular when managing carer burden in this population.
Background: Huntington’s disease (HD) is a rare triplet repeat (CAG) disorder. Advanced, multi-centre, multi-national research frameworks are needed to study simultaneously multiple complementary aspects of HD. This includes the natural history of HD, its management and the collection of clinical information and biosamples for research.
Methods: We report on cross-sectional data of the first 1766 participants in REGISTRY, the European Huntington’s Disease Network’s (EHDN), multi-lingual, multi-national prospective observational study of HD in Europe. Data collection (demographics, phenotype, genotype, medication, co-morbidities, biosamples) followed a standard protocol.
Results: Phenotype, and the HD genotype, of manifest HD participants across different European regions was similar. Motor onset was most common (48%) with a non-motor onset in more than a third of participants. Motor signs increased, and cognitive abilities and functional capacity declined as the disease burden (CAGn-35.5) X age) increased. A life-time history of behavioural symptoms was common, but the behavioural score was not related to disease burden. One fifth of participants had severe psychiatric problems, e.g. suicidal ideation and attempts, and/or irritability/aggression, with psychosis being less common. Participants on anti-dyskinetic medication had a higher motor and lower cognitive score, were older, and more prone to physical trauma. A higher motor and a lower cognitive score predicted more advanced disease.
Conclusions: The unparalleled collection of clinical data and biomaterials within the EHDN’s REGISTRY can expedite the search for disease modifiers (genetic and environmental) of age at onset and disease progression that could be harnessed for the development of novel treatments.
Evaluation of Histone Deacetylases as Drug Targets in Huntington’s Disease models
Study of HDACs in brain tissues from R6/2 and CAG140 knock-in HD mouse models and human patients and in a neuronal HD cell model.
The family of histone deacetylases (HDACs) has recently emerged as important drug targets for treatment of slow progressive neurodegenerative disorders, including Huntington’s disease (HD). Broad pharmaceutical inhibition of HDACs has shown neuroprotective effects in various HD models. Here we examined the susceptibility of HDAC targets for drug treatment in affected brain areas during HD progression. We observed increased HDAC1 and decreased HDAC4, 5 and 6 levels, correlating with disease progression, in cortices and striata of HD R6/2 mice. However, there were no significant changes in HDAC protein levels, assessed in an age-dependent manner, in HD knock-in CAG140 mice and we did not observe significant changes in HDAC1 levels in human HD brains. We further assessed acetylation levels of α-tubulin, as a biomarker of HDAC6 activity, and found it unchanged in cortices from R6/2, knock-in, and human subjects at all disease stages. Inhibition of deacetylase activities was identical in cortical extracts from R6/2 and wild-type mice treated with a class II-selective HDAC inhibitor. Lastly, treatment with class I- and II-selective HDAC inhibitors showed similar responses in HD and wild-type rat striatal cells. In conclusion, our results show that class I and class II HDAC targets are present and accessible for chronic drug treatment during HD progression and provide impetus for therapeutic development of brain-permeable class- or isoform-selective inhibitors.
Increased iron levels have been demonstrated in the basal ganglia of manifest Huntington’s disease (HD). An excess in iron accumulation correlates with MRI T2-weighted hypointensity. Determination of the amount of hypointensities in the basal ganglia in the premanifest phase of HD may give more insight in the role of iron in the pathogenesis of HD. Therefore, the present study assessed whether the degree of hypointensities on T2-w MRI in the basal ganglia of premanifest gene carriers differs from non-carriers. Seventeen HD gene carriers without clinical motor signs and 15 non-carriers underwent clinical evaluation and MRI scanning. The amount of T2-w hypointensities was determined using a computer-assisted quantitative method that classified each pixel in the basal ganglia as hypointense or not, resulting in a total of hypointense pixels for each individual. Carriers showed an increased amount of hypointensities in the basal ganglia compared to non-carriers. More hypointensities were furthermore associated with a higher UHDRS total motor score, a longer CAG repeat length and a greater probability of developing symptoms within 5 years. We concluded that the increased amount of hypointensities in the basal ganglia of premanifest carriers of the HD gene may reflect excessive iron deposition and a role for iron in the neuropathology of HD. Furthermore, this phenomenon is associated with clinical and biological disease characteristics. An increased amount of hypointensities on T2-w MRI in the basal ganglia may be considered a biomarker for HD.