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Sunday 11th September
S001 GENETICS, HISTORY, AND HUNTINGTON’S DISEASE
P. S. Harper.University Department of Genetics, Cardiff University, UK
An historical perspective can throw valuable light on how our understanding has progressed over the years, not just for Huntington’s disease (HD) itself, but for a range of other genetic and neurological disorders. The history of the condition is of interest in its own right, but less explored historically have been the genetics of HD as a pioneer in gene mapping and gene isolation, the experience of predictive testing as a worldwide endeavour, and HD as a model for social issues, such as insurance.
In each of these aspects, HD has led the way and our experience from it has been widely generalisable. Now we are starting to see the same process in relation to therapeutic initiatives and worldwide collaborative trials. The history of all these successive developments may well confirm the key role that HD, through the patients, families, and professionals involved, has had in the wider development of our understanding of the basis and consequences of inherited disease.
Keywords: history; genetics; therapeutic trials
Plenary session I: pathogenic mechanisms 1
S002 PATHOGENIC MECHANISMS IN HUNTINGTON’S DISEASE: CLUES TO POSSIBLE THERAPEUTIC STRATEGIES
D. C. Rubinsztein1, B. Ravikumar1, C. Vacher1, S. Luo1, J. Davies1, Z. Berger1, C. O’Kane2, S. Imarisio2, A. Acevedo-Arozena3, S. D. M. Brown3.1Department of Medical Genetics, Cambridge Institute for Medical Research, Addenbrooke’s Hospital, Cambridge, UK; 2Department of Genetics, University of Cambridge, UK; 3Medical Research Council Mammalian Genetics Unit, Harwell, UK
The Huntington’s disease mutation is likely to cause disease predominantly by gain-of-function mechanisms. A number of processes may contribute to the toxicity of the mutation, including aggregation, raised levels of reactive oxygen species, abnormal calcium signalling, and perturbed axonal transport. Thus, it may be difficult to effectively treat the disease by targeting a single specific pathogenic pathway, unless that pathway is a major contributor to the human disease. As the severity of disease is likely to correlate with the levels of the toxic product, we have been trying to understand how its levels are regulated. At the level of synthesis, current data, largely from the Hayden laboratory, suggest that the toxicity of mutant huntingtin is exposed after cleavage events. We will review some recent data describing a novel way of regulating the production of the toxic fragments. The levels of the toxic fragment are also regulated by its clearance. We will review data in cell and animal models suggesting that autophagy is a key pathway regulating mutant huntingtin fragment clearance, and discuss how this may have potential as a therapeutic strategy.
Keywords: autophagy; cleavage
S003 THE VARIABLE PATTERN OF CELL LOSS IN THE CEREBRAL CORTEX CORRELATES WITH THE VARIABLE PATTERN OF SYMPTOMATOLOGY IN HUNTINGTON’S DISEASE
D. C. V. Thu1, D. E. Oorschot3, L. Tippet2, V. Hogg2, H. J. Waldvogel1, R. L. M. Faull1.1Department of Anatomy with Radiology; 2Department of Psychology, University of Auckland, New Zealand; 3Department of Anatomy and Structural Biology, Otago School of Medical Sciences, University of Otago, New Zealand
Huntington’s disease (HD) is a neurodegenerative disease that is characterised by a variable pattern of symptomatology (motor, cognition, and mood changes). HD primarily affects the basal ganglia but recent studies have shown that the cerebral cortex, particularly the motor cortex, is also affected. In this study, the total neuronal population in the primary motor cortex (Brodmann’s area 4) and the cingulate cortex (Brodmann’s area 24) was investigated using stereological counting techniques and compared with the pattern of symptomatology in 13 cases of HD (grades 0, 1, 2, and 3) and 14 age, sex, and postmortem delay matched neurologically normal cases. The human brains were fixed by perfusion and tissue blocks were selected from the same regions of the primary motor cortex and cingulate cortex and sectioned at 50 μm. After a random start, every tenth section was immunohistochemically stained with neuronal N and the total number of neurons was determined using the optical disector and Cavalieri methods (Nv × Vref). In general, the results show a variable loss in the total number of neurons in the HD brains, which was the greatest in the grade 3 cases compared to the normal for both the primary motor cortex and cingulate cortex. Most interestingly, when the HD cases were grouped according to their symptoms (mainly mood versus mainly motor symptoms), the results show a positive correlation between the pattern of cell loss and the pattern of symptomatology in HD. The HD cases with mainly motor symptoms show more cell loss in the primary motor cortex whereas those with mainly mood symptoms show more cell loss in the cingulate cortex. These findings indicate that the variable pattern of cell loss in the primary motor and cingulate cortex correlates with the variable pattern of symptomatology in HD.
Keywords: cell loss; cerebral cortex; symptomatology
S004 REGIONAL SPECIFICITY OF TRANSCRIPTIONAL CHANGES IN EARLY GRADE HUNTINGTON’S DISEASE BRAIN
A. Hodges1, A. D. Strand2, A. K. Aragaki2, T. Sengstag3, G. Hughes1, L. A. Elliston1, C. Hartog1, D. R. Goldstein4, D. Thu5, Z. R. Hollingsworth6, F. Collin7, B. Synek8, P. A. Holmans1, A. B. Young6, N. S. Wexler9, M. Delorenzi3, C. Kooperberg2, S. J. Augood6, R. L. M. Faull5, J. M. Olson2*, R. Luthi-Carter4*, L. Jones1*.1Departments of Psychological Medicine and Medical Genetics, Cardiff University, Cardiff, UK; 2Fred Hutchinson Cancer Research Center, Seattle, USA; 3National Center of Competence in Research (NCCR) Molecular Oncology, Swiss Institute of Experimental Cancer Research (ISREC) and Swiss Institute of Bioinformatics (SIB), Epalinges, Switzerland; 4Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland; 5Department of Anatomy with Radiology, University of Auckland, Auckland, New Zealand; 6MassGeneral Institute of Neurodegenerative Disease (MIND), Massachusetts General Hospital, Charlestown, USA; 7Diabetics Center, University of California, San Francisco, USA; 8Auckland City Hospital, Auckland, New Zealand; 9Columbia University, New York, USA
Transcriptional dysregulation has been proposed as an early pathogenic event in Huntington’s disease (HD) and is a potential target for therapeutic intervention. The present study examines a large set of low grade human HD brains in order to measure mRNA changes in HD sensitive and HD spared brain regions. We extracted and hybridised RNA from 44 HD and 33 age, sex, and postmortem interval matched control brain samples to Affymetrix U133A and B GeneChips. The greatest number and magnitude of RNA changes were found in caudate where 21% of probesets demonstrated significant alterations (p<0.001). In motor cortex (BA4) and cerebellum, 3% and 1% of probesets, respectively, demonstrated significantly altered expression (p<0.001). There were no changes in expression in HD prefrontal association cortex (BA9). Thus expression changes are most prevalent in brain regions susceptible to neurodegeneration. Although some changes will be attributable to cell loss, many genes changed in common between the affected brain areas (46% of significant BA4 probesets: p<0.001, overlap with significant caudate probesets). This suggests common pathways underlying neurodegeneration. To investigate these pathways, the Gene Ontology database (http://www.geneontology.org) was used to assign function to the altered mRNAs and identify overrepresented functional categories. Consistent with previous observations, significantly altered biological processes in caudate are related to neuronal signaling and homeostasis. Changes in gene expression in several categories related to ion transport, CNS development, and neurogenesis are observed in both caudate and cortex. Although HD caudate and BA4 show many overlapping gene expression changes, differences include decreased levels of mRNAs encoding microtubule structure and transport components in motor cortex but not in caudate. These data provide for the first time a broad and thorough view of the molecular phenotype of human HD and show that changes in mRNA levels are extensive in early grade HD brains.
Keywords: transcription; dysregulation; human
S005 MUTANT HUNTINGTIN REPRESSES TRANSCRIPTION FROM THE THYROID HORMONE RECEPTOR
L. Jones1, L. A. Elliston1, R. Caswell1, N. Ersoy2.1Cardiff University, UK; 2Bogazici University, Istanbul, Turkey
Huntington’s disease (HD) is an inherited neurodegeneration with midlife onset and inexorable progression to debilitation and death 10–20 years later. The disease is caused by expression of an expanded glutamine tract in the protein huntingtin. One of the earliest events known to be mediated by mutant huntingtin is a deficit in transcription. In people with HD and in animal models of the disease there is dysregulation of mRNAs in the brain: increasing transcription using inhibitors of histone deacetylases alleviates phenotypic changes in HD models indicating that the transcriptional changes are important in pathogenesis. The mechanism proposed is that mutant huntingtin binds transcriptionally active proteins, including the nuclear receptor co-repressor 1 (NCOR1), which mediates transcriptional repression through nuclear hormone receptors including thyroid receptors (TR). Expression of both normal and mutant full length huntingtin repressed transcription from TR1β; in the presence of 3:5,3′ triiodothyronine (T3); coexpression of NCOR1 alleviated repression by normal huntingtin, but not by mutant huntingtin. The expressed mutant and normal huntingtin remained cytoplasmic and were not truncated. In order to investigate whether this effect is likely to be relevant to disease aetiology, we compared changes in gene expression seen in human HD cortex with those seen in cultured cells and in mouse liver upon stimulation by T3. We detected a substantial overlap of genes with altered expression in human HD cortex, T3 stimulated rat cardiomyocytes (p<0.0001) and mouse liver (p = 0.0027). Alterations in transcription through TR appear to be important mediators of HD transcriptional changes.
Keywords: neurodegeneration; thyroid receptor
Plenary session II: genetics
S006 GENETIC CRITERIA FOR THE MECHANISM OF PATHOGENESIS IN HUNTINGTON’S DISEASE
J. F. Gusella.MGH Center for Human Genetic Research and Harvard Medical School, Boston, USA
Huntington’s disease (HD) is a neurodegenerative disorder in which all patients have the same dominant genetic lesion, expansion of the number of consecutive glutamine codons in the huntingtin coding sequence, though the size of the expansion varies. The pathogenic pathway that produces the symptoms of HD is triggered by the presence of an expanded polyglutamine tract in the huntingtin protein. However, mutant huntingtin is present throughout life, whereas the symptoms of HD typically appear only in midlife, suggesting that there are multiple steps in the pathway before the ultimate demise of striatal neurons that is characteristic of the disorder. Genotype-phenotype comparisons of HD patients and patients with other polyglutamine disorders have established clear genetic criteria for assessing the mechanism that triggers HD pathogenesis and have revealed that the length of the polyglutamine stretch is the primary determinant of age at neurological onset, explaining up to 70% of the variance in this parameter. Genetically accurate mouse models have indicated that the gain-of-function that triggers pathogenesis acts first at the level of the full length huntingtin protein, only much later leading to protein cleavage and aggregation. In humans, the variation in age at onset not attributable to the CAG repeat length shows high heritability, indicating that other genes act to modify the disease process. The effort to define the nature of these modifiers is underway, as their known capacity to alter HD in humans will provide prevalidated targets for therapeutic development.
Keywords: genetics; mouse model; modifier
S007 HDL2 MUTATIONS ARE AN IMPORTANT CAUSE OF HUNTINGTON’S DISEASE IN PATIENTS WITH AFRICAN ANCESTRY
A. Krause1, C. Hetem1, S. E. Holmes2, R. L. Margolis2.1Division of Human Genetics, School of Pathology, National Health Laboratory Service and University of the Witwatersrand, Johannesburg, South Africa; 2John Hopkins University, School of Medicine, Baltimore, USA
Huntington’s disease (HD), in most cases, is caused by a CAG repeat expansion in the IT15 gene on chromosome 4p. A CAG/CTG repeat expansion in the junctophilin-3 (JPH3) gene on chromosome 16q23 has been implicated in a subset of clinically diagnosed HD cases that did not have an expansion in the HD gene. The disorder caused by this mutation has been designated Huntington’s disease type 2 (HDL2).
In a sample of South African unrelated individuals tested diagnostically for HD, 84% (78/93) of white patients had IT15 expansions, while only 36% (18/50) of black patients and 50% (3/6) of mixed ancestry patients had IT15 expansions. However, 24% (12/50) of black patients and 50% (3/6) of mixed ancestry patients had HDL2 expansions. Thus mutations at the HDL2 locus contribute significantly to the HD phenotype in South Africa, and thus HDL2 testing is now offered as part of routine Huntington disease diagnostic testing.
To date, we have studied 17 HDL2 patients from 15 families. Repeat sizes range from 40–58 repeats. No juvenile cases have yet been observed, but in some families anticipation appears to be marked. Although clinical and pedigree data are few at present, 73% (11/15) have a positive family history. Clinically, features are similar to HD, but remain to be fully documented. Preliminary data suggest later average age of onset, earlier onset dementia and psychiatric symptoms, and more prominent early Parkinsonian features.
All HDL2 cases reported worldwide to date, including the cases that we have identified in South Africa, have definite or probable African ancestry suggesting a founder HDL2 mutation that originated in Africa. Haplotype analysis using 6 linked markers (3 SNPs and 3 microsatellite markers) in 20 HDL2 families has identified a common core haplotype. This suggests the HDL2 mutation originated in Africa between 300 and 2000 years ago.
Keywords: HDL2; Africa; founder
S008 MODIFIERS OF THE HUNTINGTON’S DISEASE MUTATION IN THE MOUSE
A. Lloret, I-SSeong, J. Srinidhi, T. Gillis, M. Hakky, S. Kishikawa, J. Gusella, V. Wheeler, M. MacDonald.Molecular Neurogenetics Unit and Center for Human Genetic Research, Massachusetts General Hospital, Charlestown, MA, USA
Discovery of the HD CAG repeat expansion that is the root cause of Huntington’s disease (HD) set the stage for identifying genes and factors that modify the severity of the pathogenic process. In HD patients, onset of disease symptoms is determined by the length of the HD CAG repeat, although there is significant variation in the precise age at onset in any given individual that points to genetic HD modifier loci. To facilitate the discovery of these loci, and to elucidate early steps in pathogenesis, we have created genetically accurate HD CAG knock-in mice. Testing of candidate modifier loci reveals that wild type huntingtin does not alter the timing of nuclear mutant huntingtin, an early disease phenotype. By contrast, mismatch repair gene Msh2 is a major modifier, hastening disease, implicating the activities of this protein in the early disease process. Moreover, in an unbiased strategy designed to identify novel modifer genes, we have performed breeding experiments to place the HdhQ111 allele on different inbred mouse strain genetic backgrounds, including C57BL/6, FVB/N and 129Sv. Our analysis of these HdhQ111 congenic mice demonstrates that the genetic background is a major determinant of the onset of early disease, setting the stage for classical mapping experiments to identify genes that modify the onset of early disease events that precede overt pathology. The identification of these HdhQ111 modifier loci would provide insights into the early pathogenic process, provide candidates to test in studies with HD samples, and offer potentially novel validated targets for the development of effective therapeutics for this devastating disorder.
Keywords: genetic modifier; Hdh; early disease
S009 IS THE PROGRESSION OF HUNTINGTON’S DISEASE DETERMINED BY SOMATIC CAG REPEAT INSTABILITY?
S. C. Vatsavayai, G. M. Dallérac, A. J. Milner, D. M. Cummings, K. P. S. J. Murphy, M. C. Hirst.Open University, Milton Keynes, UK
Huntington’s disease (HD) is a fatal genetic neurodegenerative disorder that afflicts 3–6 people per 20 000 of the population. Symptoms include progressive motor dysfunction, cognitive decline, and psychiatric problems. The genetic mutation that gives rise to HD is a CAG repeat expansion in the gene that encodes huntingtin, resulting in an expanded polyglutamine tract in the protein. It is known that the mutant allele can undergo further CAG repeat expansion as seen during transmission through the male germline; the mechanism that determines anticipation. Importantly, there is evidence that the allele is also unstable in somatic tissue, particularly in the brain. The role of somatic instability in the disease process has yet to be addressed.
To address this question we are currently investigating the relation between CAG repeat instability and brain pathology, at a cellular level, in the R6/1 mouse model of HD. During this study we discovered a spontaneous CAG repeat deletion (∼30 repeats) in the transgene of a male breeder. This deletion event has allowed us to generate two lines of R6/1 mice, one carrying the original expansion of 115 and the deleted line carry an expansion of 85 repeats. Importantly, the deleted transgene was transmitted to further generations without a significant increase or decrease in CAG repeat number. Both lines exhibit a progressive phenotype but onset is delayed in the deleted line. These lines share a common genetic ancestry and only differ in terms of their CAG repeat number, thus they provide a unique tool to study repeat length instability in otherwise identical mice. Preliminary work suggests that in both lines, somatic instability is evident before the onset of an overt behavioural phenotype, suggesting that CAG instability may contribute to the ongoing disease process.
Keywords: transgenic; mouse; DNA
Plenary session III: clinical markers
S010 EARLY CLINICAL MARKERS OF HUNTINGTON’S DISEASE
E. H. Aylward.University of Washington, Seattle, USA
This presentation will review recent findings regarding the earliest changes observable in individuals who have tested positive for the Huntington’s disease (HD) gene mutation but have not yet been diagnosed with the disorder. These include findings from neuroimaging (MRI, functional MRI, and MRS), neuropsychological testing, and measures of psychiatric impairment. Discussion will include use of these measures as biomarkers for assessing progression of the illness during the presymptomatic stage. Baseline data from the PREDICT-HD study, as well as from individual investigators will be presented and evaluated. Neuroimaging findings include: (a) data indicating smaller striatal volumes in gene-positive individuals as early as 12 years before estimated onset; (b) highly significant correlation between striatal volumes and estimated years to onset; (c) 2–5% per year shrinkage of caudate and putamen in individuals within 12 years of estimated onset; (d) good discriminant analysis of presymptomatic individuals who will be diagnosed within two years of the MRI scan. Studies involving early cortical atrophy will also be discussed. Functional MRI, using a variety of tasks (for example, interference, implicit learning, time discrimination), indicates reduced activation in medial prefrontal regions and striatum in presymptomatic subjects. Neuropsychological studies suggest that subtle changes in brain and behaviour may be detected before subjects with the HD mutation develop sufficient signs and symptoms for diagnosis. Data will be presented regarding which measurements can detect the earliest signs of impairment. The presentation will include discussion of the combination of data from multiple modalities that may provide the most accurate prediction of the onset of diagnosable HD. Also included will be a discussion of the types of data needed to warrant use of these measures as surrogate endpoint in future clinical trials.
Keywords: biomarker; neuroimaging; presymptomatic
S011 STRIATAL LOSS OF A1 ADENOSINE RECEPTORS IN HUNTINGTON’S DISEASE: A PET STUDY
A. Bauer1, C. Saft2, J. E. Andrich2, D. Elmenhorst1, A. Matusch1, P. H. Kraus2, H. Przuntek2, K. Zilles1.1Molecular Neuroimaging Laboratory, Institute of Medicine, Research Centre Jülich, Germany; 2Department of Neurology, Ruhr University, Bochum, Germany
Introduction: Adenosine plays an important role in neurotransmission. It exerts a potent feedback inhibitory effect on excitatory, esp glutamatergic neurotransmission and is thus regarded as a “natural” neuroprotective compound. Most of its effects are mediated by the activation of A1 adenosine receptors (A1AR). The occupancy of these receptors is, therefore, regarded as a potential indicator of neuronal stress. We report the first application of a novel PET ligand for A1ARs ([18F]CPFPX) in patients suffering from Huntington’s disease (HD).
Methods: Quantitative dynamic [18F]CPFPX receptor PET was performed in eight HD patients (6M/2F; range 36.8–47.4 years, mean 47.4 (SD 5.3 years.) and 14 healthy age matched controls (8M/6F; range 28.3–73.5 years, mean 49.1 (SD 14.3 years.). Regional cerebral ligand distribution was evaluated generating stereotactical normalised and averaged parametric datasets from k3/k4 ratio values which were regarded as a measure of A1AR density using the cerebellum as reference region. Group comparison was done using SPM99.
Results: The in vivo distribution of [18F]CPFPX in healthy controls is in excellent accordance with in vitro findings on the regional cerebral A1AR pattern of human postmortem brains. Highest densities are found in temporal cortex, striatum, and thalamus. Medium to low receptor densities are observed in midbrain and brainstem. Voxel based group comparisons of HD patients and healthy age matched controls demonstrate a significant reduction of A1AR density in the striatum.
Conclusion: [18F]CPFPX is the first ligand which allows non-invasive imaging of cerebral A1ARs. It reveals a distinct distribution pattern of the A1AR in the human brain, which is in accordance with in vitro autoradiographic data. In HD patients, there is a significant reduction of striatal A1AR density. The novel adenosinergic PET ligand has potentials to serve as an indicator and progression marker of HD.
Keywords: PET; adenosine; receptors
S012 MICROGLIAL ACTIVATION IN PRESYMPTOMATIC HUNTINGTON’S DISEASE GENE CARRIERS: A 11C-PK11195 PET STUDY
Y. F. Tai1, N. Pavese1, A. Gerhard1, S. J. Tabrizi2, R. A. Barker3, D. J. Brooks1, P. Piccini1.1MRC Clinical Sciences Centre, Hammersmith Hospital, Imperial College London, UK; 2Department of Neurodegenerative Disease, Institute of Neurology, London, UK; 3Cambridge Centre for Brain Repair, Forvie Site, Cambridge, UK
Introduction: Microglial activation has been postulated to be involved in the pathogenesis of Huntington’s disease (HD). Using 11C-(R)-PK11195 (PK) positron emission tomography (PET), we have recently shown significant microglial activation in HD brain, and that it correlates with disease severity rated both clinically and with 11C-raclopride PET, a marker of striatal dopamine D2 receptors. The aims of the current study are to investigate microglial activation in presymptomatic HD gene carriers (PSGC) and its role in the pathogenesis of HD.
Methods: Six PSGC (mean age 39.8 (SD 4.1) years; CAG repeats mean length 43.5 (SD 3.6)) and 10 normal controls (age 57.4 (SD 11.3) years) underwent a PK PET and an MRI. Striatal regions of interest were defined on MRI and applied to coregistered PK binding potential (BP) parametric images.
Results: Mean striatal PK BP of PSGC is significantly higher than the controls (p<0.005). Among the PSGC, four subjects, all of whom had ⩽3 years to predicted disease onset (based on Brinkman et al, 1997), had increased striatal PK BP (>2 SDs above control mean). The other two PSGC with normal striatal PK BP had >10 years to predicted disease onset. The individual PSGC striatal PK BP correlated negatively with number of years to predicted disease onset (r = −0.89, p<0.05), and positively with age related genetic disease load, measured by CAG index [ = (CAG repeats length-35.5)*age], (r = 0.89, p<0.05).
Discussion: We have demonstrated for the first time in vivo microglial activation in PSGC, particularly nearing the predicted onset of disease. This supports the notion that microglial activation is a relatively early event in the pathogenic processes of HD and is associated with subclinical progression of disease. This may have important therapeutic implications as agents that inhibit microglial activation, such as minocycline, may be trialled to delay disease onset in PSGC.
Keywords: presymptomatic; microglial activation; positron emission tomography
S013 THE EFFECTS OF CAG REPEAT LENGTH ON CLINICAL PROGRESSION IN HUNTINGTON’S DISEASE
A. Rosenblatt1, M. H. Abbott1, L. M. Gourley1, R. L. Margolis1, J. Brandt1, C. A. Ross1, K-YLiang2, H. Zhou2.1Department of Psychiatry, Johns Hopkins University School of Medicine, Baltimore, USA; 2Department of Biostatistics, Johns Hopkins University, Baltimore, USA
Objective: To determine whether the rate and trajectory of clinical progression in Huntington’s disease is influenced by the size of the CAG expansion.
Methods: The dataset consisted of 3402 examinations of the 512 individuals who had been examined two or more times in the Baltimore Huntington’s Disease Center. Subjects were seen 2–26 times, with a mean of 6.64 visits. The duration of follow up ranged from less than 1 to 22 years and the mean was 6.74 years. CAG ranged from 36 to 97 repeats (mean 47.15) and the exams took place 0–42 years after onset of symptoms (mean 9.42). Compared with subjects who were seen only once, subjects who were seen two or more times did not differ on race or sex, age, or any of our main clinical measures once a correction was made for disease duration. Subjects were administered the Quantified Neurological Examination, with its subsets the Motor Impairment and Chorea Scores, the Mini-Mental State Examination, and the HD Activities of Daily Living (ADL) Scale.
Results: QNE, MIS, ADL, and MMSE scores observed over time for each individual were then regressed linearly on race, sex, disease duration, CAG number, and the interaction terms for CAG number with disease duration using the PROC MIXED of SAS version 8.0 to fit the random effects model to the repeated observations. Further graphical exploration of the data using Lowess plots also suggested differences in trajectory based on repeat length, with those with the smallest CAG expansions possibly experiencing a more benign late course.
Conclusions: CAG repeat length has an effect on rate of progression, which may be clinically important over time. Individuals with the shortest expansions may have a better late prognosis. These effects of CAG length may be relevant in the analysis of clinical trials.
Keywords: progression; longitudinal; clinical
Monday 12th September
Concurrent session Ia: pathogenic mechanisms 2
S014 LINKS BETWEEN PROTEOLYSIS AND NEUROTOXICITY IDENTIFY NOVEL APPROACHES FOR MODIFYING THE PATHOGENESIS OF HUNTINGTON’S DISEASE
R. K. Graham1, A. Yanai1, A. El Husseini2, M. R. Hayden1.1Centre for Molecular Medicine and Therapeutics; 2Department of Psychiatry, University of British Columbia, Vancouver, Canada
Huntington’s disease is a neuropsychiatric disease caused by expansion of a trinucleotide repeat in the HD gene, huntingtin. Proteolytic cleavage of huntingtin by caspases with concomitant generation of toxic huntingtin fragments has been well characterised in vitro, and caspase mediated fragments of huntingtin are present in HD brain before clinical onset of HD. These observations provide strong support for the toxic fragment hypothesis, which proposes that huntingtin cleavage is a crucial determinant of pathology in HD and furthermore suggest that caspase resistant (CR) huntingtin may delay or prevent the onset or progression of HD in vivo. To test this hypothesis using the YAC animal model of HD, we used homologous recombination to mutate both caspase 3 and 6 cleavage sites within full length genomic huntingtin with 18 and 128CAG. Neuropathological analysis revealed that complete inhibition of caspase cleavage of expanded htt (128CQR) protects against the neurodegeneration observed in the YAC 128 model. We then sought to determine whether caspase 3 or caspase 6 is the key player in generating the selective toxicity observed in the striatum. Analysis of 128C3R and 128C6R lines demonstrated that while 128C3R did not provide protection, selective mutagenesis of the caspase-6 site provided significant protection from neurodegeneration in vivo. In two independent 128C6R lines, brain weights, and striatal volumes are indistinguishable from wild type. In contrast, brain weights and striatal volumes in caspase cleavable YAC128 mice are decreased by 10 (*p<0.05) and 16% (***p<0.0003) respectively. Furthermore, assessment of excitotoxicity in YAC128 and 128C6R mice, using ex vivo and in vivo approaches revealed that there was significantly decreased excitotoxicity in the 128C6R versus YAC128 mice (***p<0.001). An early marker for neuronal toxicity is trafficking of htt fragments into the nucleus. Lipid modification of htt within the cleaved fragment is crucial for its normal trafficking which is altered by the mutation for HD leading to enhanced inclusion body formation and neuronal toxicity. These results provide novel insights into the roles of proteolysis, excitotoxicity, and post-translational modification of htt in the pathogenesis of HD.
Keywords: huntingtin cleavage; caspase; neuronal toxicity; pathogenesis
S015 SELECTIVE DEGENERATION AND NUCLEAR LOCALISATION OF MUTANT HUNTINGTIN IN THE YAC128 MOUSE MODEL OF HUNTINGTON’S DISEASE
J. M. Van Raamsdonk, Z. Murphy, E. J. Slow, B. R. Leavitt, M. R. Hayden.Department of Medical Genetics and Centre for Molecular Medicine and Therapeutics, University of British Columbia, Vancouver, BC, Canada
Huntington’s disease (HD) is an adult onset neurodegenerative disorder that is characterised by selective atrophy and neuronal loss that occurs primarily in the striatum and cortex. Here we demonstrate that this pattern of selective degeneration is present in the YAC128 mouse model of HD. YAC128 mice express full length mutant huntingtin (htt) from a yeast artificial chromosome transgene containing the entire HD gene. At 12 months of age, YAC128 mice show significant atrophy in the striatum, globus pallidus, and cortex with relative sparing of the hippocampus and cerebellum (striatum: −10.4%, p<0.001; globus pallidus: −10.8%, p = 0.04; cortex: −8.6%, p = 0.001; hippocampus: +0.3%, p = 0.9; cerebellum: +2.9%, p = 0.6). Similarly, neuronal loss at this age is present in the striatum (−9.1%, p<0.001) and cortex of YAC128 mice (−8.3%, p = 0.02) but is not detected in the hippocampus (+1.5%, p = 0.72). As in human HD, mutant htt expression levels are similar in affected and unaffected regions of the brain and thus the selective degeneration in YAC128 mice is not explained by differences in mutant htt expression. In contrast, nuclear localisation of mutant htt in YAC128 mice is selective—it occurs earlier and to a greater extent in the striatum and thus correlates with the disease pathology. Examination of the R6/1 mouse model of HD reveals relatively unselective, widespread atrophy in the brain at 10 months of age. At this age, nuclear localisation of mutant htt in R6/1 mice is also unselective, occurring evenly throughout the brain. Our findings suggest that selective nuclear localisation of mutant htt may contribute to the selective degeneration in HD and that the appropriately regulated expression of full length mutant htt in YAC128 mice results in a pattern of selective degeneration that is remarkably similar to human HD.
Keywords: mouse model; selective degeneration; pathogenesis
S016 DECREASED ULTRASONIC VOCALISATION CALLS ARE ASSOCIATED WITH GENE EXPRESSION CHANGES IN HUNTINGTON’S DISEASE TRANSGENIC RAT PUBS AT POSTNATAL DAY 10
H. Phuc Nguyen1, M. Stephan2, K. Raber2, O. Riess1, S. von Hörsten2.1Medical Genetics, University of Tübingen, Germany; 2Functional and Applied Anatomy, Hannover Medical School, Germany
Transgenic rats carrying a truncated rat huntingtin fragment of 51 CAG repeats under control of the rat htt promoter exhibit a slowly progressive behavioral phenotype with emotional disturbance, motor deficits, and cognitive decline. So far we have found that the sequence of behavioural markers per se closely replicates the symptomatology of HD as well as that the very first behavioural symptoms seem to precede significantly the appearance of aggregates. In the present studies, we screened for behavioural differences even in tgHD rat pups and observed decreased ultrasonic vocalisation calls in 10 day old tgHD rat pups compared with controls, whereas the earliest aggregates have been detected at 9 months of age so far. In order to elucidate possible mechanisms leading to this unsuspected early phenotype we performed a microarray analysis on these animals. We found reduced levels of mRNAs encoding components of the neurotransmitter catabolism (Comt) and Akt signalling pathways (Pdpk1) at this very early time point in transgenic animals. Our results also indicate that mutant huntingtin directly or indirectly reduces the expression of a distinct set of genes involved in signaling pathways known to affect cell survival and apoptosis even at this young age.
Partly supported by the High Q Foundation.
Keywords: microarray; early phenotype; transgenic rat
S017 DOPAMINE RESTORES CORTICAL FUNCTION HUNTINGTON’S DISEASE MICE
D. M. Cummings, A. J. Milner, G. M. Dallérac, S. C. Vatsavayai, M. C. Hirst, K. P. S. J. Murphy.Open University, Milton Keynes, UK
Huntington’s disease (HD) is characterised by a progressive motor, psychiatric, and cognitive decline, often manifesting in midlife. Since the identification of the gene responsible for HD and the development of predictive testing it has become apparent that asymptomatic patients often exhibit early cognitive deficits, in particular impairment in recognition memory. The perirhinal cortex encodes recognition memory and activity dependent decrements in neuronal firing in this brain area are believed to underlie this cognitive process (as a cue becomes familiar the firing rate decreases). We have examined synaptic plasticity in the perirhinal cortex of the R6/1 mouse model of HD. Brain slices were prepared according to UK legislation and electrophysiological recordings were made from layer II/III in response to stimulation of layer I. In normal mice, the predominant form of plasticity is synaptic depression. Slices prepared from litter mate controls exhibited paired pulse depression (PPD) and long term depression (LTD) (−19.4 (4.7)%, n = 16; −24.6 (7.2)%, n = 7; −16.5 (5.7)%, n = 6; at 2, 5, and 7 months respectively; mean (SEM)). Slices prepared from 2 month old R6/1 mice also showed PPD, but LTD was unexpectedly enhanced (−42.7 (12.8)%, n = 5; p<0.05) whereas at 7 months slices displayed paired pulse facilitation and failed to support LTD (+8.1 (6.8)%, n = 7; p<0.0001). The neurotransmitter dopamine is a potent neuromodulator in the perirhinal cortex. It has recently been shown that dopamine activity is reduced in asymptomatic HD patients. Interestingly, the 7 month R6/1 synaptic phenotype could be recapitulated in litter mate control slices by the application of the D2 dopamine receptor antagonist Remoxipride. Importantly, normal synaptic plasticity was restored in transgenic HD slices by the D2 agonist Quinpirole (10 μM;−42.1 (13.7)%, n = 9). These data strongly suggest that dopaminergic therapy targeted to the cortex may be beneficial in the relief of cognitive decline in HD.
Keywords: synaptic plasticity; recognition memory; cognition
Concurrent session Ib: genetic counselling and testing
S018 GENETIC COUNSELLING AND TESTING
A. Tibben.Department of Neurology and Centre for Human and Clinical Genetics, Leiden, the Netherlands
Localisation of the causal factor for Huntington’s disease (HD), in 1983, paved the way for predictive testing (PD), which was experienced as a herald of better times in which the disease could be controlled, cured, and prevented. It took another few years (1986/1987) before PD became clinically available. Identification of the HD gene in 1993 made testing more reliable and easier to perform. Unbearable uncertainty was—and still is—the main reason for individuals at risk for HD to consider PD. Another important motive concerns family planning—to avoid passing the gene on to future offspring. Worldwide, counselling and testing protocols have benefited from the WFN/IHA guidelines (1987/1994). After a tentative start, an increasing number of genetic centres have provided PD, making use of the experience of research groups that have tenaciously followed up large groups of tested individuals. Yet, uptake has been relatively low over the years, the highest uptake being 24% in the Netherlands. Now, 20 years later, testing has become common practice and most of the difficulties encountered relate not to laboratory issues, but to the counselling and human aspects of PD. People wish to anticipate and control their future, they wish to know their CAG repeat size and at which point in their lives onset of HD can be expected. Some people have to process the complex risk figures with regard to intermediate or reduced penetrance alleles. Test candidates ask questions about progress in treatment options, often encouraged by science reports. They find easy access to the Internet, get overwhelmed by huge amounts of information, and challenge counsellors to comment on new discoveries. The first children at risk, born after 1986, whose parents had decided not to take a test, have found their way to the genetic centres, bringing with them the subsequent parent-child dilemmas that need to be addressed. Lay people construct their own websites and provide an opportunity to exchange experiences. The great challenge of PD is to find out how we support people in optimally processing the information that is available, how we allow them to make the best personal decisions, how we help them adjust to the test outcomes and take the appropriate actions, and how we encourage them to adjust their behaviour to profit optimally from testing. Lessons of 20 years of PD require continuous adjustment of the testing protocols.
Keywords: predictive testing
S019 AN INTERNATIONAL SURVEY OF PREDICTIVE GENETIC TESTING IN YOUNG PEOPLE FOR ADULT ONSET CONDITIONS
R. E. Duncan1,2,3, J. Savulescu1,4, L. Gillam2, R. Williamson2, M. B. Delatycki1,3.1Murdoch Children’s Research Institute, Royal Children’s Hospital, Parkville, Victoria, Australia; 2University of Melbourne, Parkville, Victoria, Australia; 3Bruce Lefroy Centre for Genetic Health Research, Royal Children’s Hospital, Parkville, Victoria, Australia; 4Oxford Uehiro Centre for Practical Ethics, University of Oxford, UK
Background: Predictive genetic testing is offered to asymptomatic adults even when there is no prophylaxis or treatment available. However, testing of young people in similar circumstances is controversial and international guidelines recommend against it. Despite this, there has been considerable debate regarding the issue. Some perceive such testing as too potentially harmful to allow. Others perceive it as an opportunity for the promotion of benefit, an opportunity even for the prevention of harm. There is virtually no empirical evidence available to support either perception. We sought to document examples of the occurrence of such testing in young people in countries where guidelines exist.
Methods: Clinical geneticists in the USA, Canada, UK, Australia, and New Zealand were surveyed electronically about the occurrence and outcomes of testing in asymptomatic young people for adult onset conditions where no treatment or prophylaxis exists.
Results: Of 301 responses, details were provided of 49 cases where such testing had occurred. The most common condition tested for was Huntington’s disease. In 22 cases the young person tested was immature (under 14 years). Results were disclosed to only two immature minors. In three cases parents experienced clinically significant anxiety related to the timing of passing on information to their gene positive child. In 27 cases the young person tested was mature. Results were disclosed to 26/27, of whom two individuals experienced an adverse event. Consistent follow up did not take place. The majority of respondents agree with existing guidelines in principle but believe each case must be considered individually.
Conclusion: In general, clinicians agree with existing guidelines recommending against predictive genetic testing of young people unless clinically indicated, but some choose to provide tests to young people for non-medical reasons in specific cases.
Keywords: ethics; genetic testing; counselling
S020 PREIMPLANTATION GENETIC DIAGNOSIS FOR HUNTINGTON DISEASE AND PATIENTS’ VIEWS
C. L. Zaitsoff, A. Lashwood.Clinical Genetics, Guy’s Hospital, London, UK
The Centre for PGD at Guy’s Hospital performed its first cycle of preimplantation genetic diagnosis (PGD) for Huntingtons’ disease (HD) in April 2002. Since then, we have seen 29 couples for initial consultation and started 24 cycles of PGD. Sixteen cycles reached embryo transfer and nine pregnancies were achieved. Three pregnancies miscarried. Three sets of twins and three singletons have been born through the PGD programme to date.
Special considerations exist for couples considering PGD for HD that do not exist for couples requesting treatment for other disorders. As part of the preparation for treatment, neurological examination was requested for the gene carrier to allow for responsible discussions regarding the welfare of the child born following treatment. The non-carrier had their allele sizes measured to ensure analysis would be informative. The issue of prenatal diagnosis was explored as confirmatory testing would not be available after the birth of the child. We wanted to know how our couples felt about these discussions and so asked couples to complete questionnaires independently following initial consultation.
Although the sample was small (n = 20), some trends did emerge. None of the couples had children and most had had a predictive test to aid reproductive decision making. Sixteen respondents were unconcerned about the non-carrier being tested; 10 thought that discussions regarding welfare of the child were intrusive; and nine, most of whom were non-carriers, said they would want prenatal diagnosis following PGD. Ten respondents would worry about residual risk if testing at birth was not permitted.
Couples shared their views about welfare of the child and testing the non-carrier, but often did not share views with regard to prenatal diagnosis. The couples seem to come to clinic aware of their options, often having discussed them together before consultation.
Keywords: preimplantation genetic diagnosis; patient views
S021 PREDICTIVE TESTING FOR HUNTINGTON’S DISEASE: PSYCHOLOGICAL DISTRESS AND COPING STRATEGIES IN PARTNERS OF TESTED PEOPLE
M. Decruyenaere1, G. Evers-Kiebooms1, A. Boogaerts1, K. Demyttenaere2, R. Dom3, J-PFryns4.1Psychosocial Genetics Unit, 2Department of Psychiatry, 3Department of Neurology, 4Center for Human Genetics, University Hospital, Leuven, Belgium
Introduction: Asymptomatic carriers of a Huntington mutation know that they will develop a debilitating, untreatable disease in the future. In the present study, we focus on psychological distress and coping strategies in partners of tested people five years after predictive DNA testing for Huntington’s disease (HD).
Methods: Sixteen carrier couples and 17 non-carrier couples participated in the study. Semistructured interviews and self-report questionnaires were used, assessing depression level (Beck Depression Inventory), anxiety (STAI), intrusive and avoidance thoughts (Impact of Event Scale), and coping strategies (Utrechtse Coping List).
Results: Partners of carriers have as much distress as carriers and for some distress variables even more (p<0.05 to 0.001). Carriers’ partners clearly experience more psychological distress than non-carriers’ partners, as expected (p<0.05 to 0.001). Regarding coping with the unfavourable test result, carriers’ partners adopt more passive strategies (passive-regressive coping and avoiding behaviour; p<0.05) and less active strategies (social support seeking and problem solving; p<0.05 to 0.001), compared with carriers. For both carriers and their partners, the adoption of more passive strategies for coping was associated with more distress and the use of more active strategies with less distress (p<0.05 to 0.001). The presence of children before predictive testing was an additional result-specific distress factor in carriers and their partners.
Conclusion: Partners of carriers do have psychological distress, but they have the tendency to draw back. The results suggest that the grief of carriers’ partners may be “disenfranchised”, or not socially recognised, as if they have no right to mourn. We moreover interpret the results referring to concepts such as anticipatory grief, psychological defences, and imbalanced partner relationship. Finally, we formulate some implications for follow up counselling of carrier couples.
Keywords: predictive testing; psychological distress; partners
Concurrent session IIa: pathogenic mechanisms 3
S022 ROLE OF WILD TYPE HUNTINGTIN IN HUNTINGTON’S DISEASE
E. Cattaneo.Department of Pharmacological Sciences and Center of Excellence on Neurodegenerative Diseases, University of Milano, Italy
Huntington’s disease (HD) is a dominant neurodegenerative disorder caused by a CAG expansion in the gene encoding for huntingtin. It is generally considered that the disease is caused by a gained toxicity of the mutant protein. However, recent data have shown beneficial functions for normal huntingtin in neurons suggesting that some features of the disease may result from loss of wild type huntingtin activity in addition to a gained toxic activity of the mutant protein (Cattaneo, Trends in Neuroscience, 2001). Following this hypothesis we started by defining disease phenotypes that are dependent either on wild type or mutant huntingtin activity.
We reported the first evidence for a neuroprotective role of the wild type protein in neurons and how loss of these physiological functions may contribute to the striatal selective vulnerability which is typical of the disease state (Rigamonti, J Neurosci 2000; Rigamonti, J Biol Chem 2001; Zuccato, Science 2001; Zuccato, Nat Genet 2003). In addition, we have elucidated a new toxic effect triggered by mutant huntingtin by showing that the cholesterol biosynthetic pathway is altered both in HD brain and extraneuronal cells (Valenza, submitted). As cholesterol is synthesised locally in the brain and it is crucially involved both in synapse remodelling and optimal neurotransmitter release, defective cholesterol production may also contribute to HD. Finally, the study of the mechanisms underlying these findings lead us to identify two novel potential molecular targets to be used for the development of complementary therapeutical strategies.
Keywords: huntingtin; neuroprotection
S023 DYNAMICS OF SOMATIC CAG INSTABILITY IN HUNTINGTON’S DISEASE
R. Gonitel1, B. Woodman1, K. Sathasivam1, G. Bates1, R. Faull2, P. Detloff3, J. Lucas4.1Department of Medical and Molecular Genetics, King’s College London, London, UK; 2Department of Anatomy with Radiology, Faculty of Medical and Health Sciences, University of Auckland, New Zealand; 3Department of Biochemistry and Molecular Genetics, University of Alabama at Birmingham, Birmingham, AL, USA; 4Centro de Biologia Molecular Severo Ochoa, Consejo Superior de Investigaciones Cientificas, Universidad Autonoma de Madrid, Spain
Huntington’s disease (HD) is one of a group of neurodegenerative disorders caused by the pathological expansion of CAG repeat. This expanded CAG is a consequence of genetic instability—a process that leads to a change in the number of CAG units with a bias towards their increase. Despite the known relation between repeat length and polyglutamine pathology, neither the mechanisms of instability nor its contribution to the specificity of disease are understood. We have carried out a detailed characterisation of somatic instability in several HD mouse models and human HD brain tissue. Resulting data suggest that instability is a rigidly regulated process that is influenced by several variables: age, brain region, repeat length, and genomic context. Furthermore, striatal repeats showed increased bias towards expansion compared with other brain regions. Also, distinctively in the striatum, transcription was preferential from the alleles that have undergone expansion, the average size of the transcribed repeats reaching 50% increase over originally inherited length of the tract in some mouse models. This can potentially contribute to the striatal specificity of neurodegeneration in HD. Consistent with expression disequilibrium we observed striatal neuronal cells to carry exclusively somatically expanded alleles. We propose that somatic instability is not a necessary condition but a modifier for polyglutamine disease. Further, as instability develops in postmitotic cells its regulation can be sufficiently described through DNA repair processes. Understanding mechanisms of CAG instability might allow manipulation of CAG repeat length to modify polyglutamine disease.
S024 HUNTINGTIN PHOSPHORYLATION ON SERINE 421 IS SIGNIFICANTLY REDUCED IN THE STRIATUM AND BY POLYGLUTAMINE EXPANSION IN VIVO
S. C. Warby1, E. Y. W. Chan1, M. Metzler1, L. Gan1, R. R. Singaraja1, S. F. Crocker2, H. A. Robertson2, M. R. Hayden1.1Centre for Molecular Medicine and Therapeutics (CMMT), University of British Columbia, Vancouver, Canada; 2Department of Pharmacology, Dalhousie University, Halifax, Nova Scotia, Canada
Huntington’s disease (HD) results from polyglutamine expansion in the huntingtin protein (htt). Despite the widespread tissue expression pattern of htt, neuronal loss is highly selective to medium spiny neurons of the striatum. Huntingtin is phosphorylated on serine-421 (S421) by the pro-survival signaling protein kinase Akt (PKB) and this has been previously shown to be protective against the toxicity of polyglutamine-expanded htt in cell culture. Using an antibody specific for htt phosphorylated on S421, we demonstrate that htt phosphorylation is present at significant levels under normal physiological conditions in human and mouse brain. The amount of htt phosphorylation shows a regional distribution in the normal brain that is inversely correlated with disease pathology: phosphorylation in the striatum is significantly lower than the cerebellum in the normal mousebrain (p<0.001). Furthermore, the endogenous phosphorylation of polyglutamine expanded htt is significantly reduced relative to wild type htt in cell cultures (−50%, p<0.005) and in YAC transgenic mice (−50%, p = 0.016). Further work assesses the timing and functional implications of the decreased phosphorylation in relation to pathology in the YAC mice. The presence and pattern of significant htt phosphorylation in the brain indicates that this dynamic post-translational modification is important for the regulation of htt and may contribute to the selective neurodegeneration seen in HD.
Keywords: AKT; phosphorylation; YAC mouse model
S025 HYPOTHALAMIC PATHOLOGY AND ENDOCRINE CHANGES AS THERAPEUTIC TARGETS FOR HUNTINGTON’S DISEASE
Å. Petersén1, M. Björkqvist1,2, J. Gil1, N. Popovic1, P. Norlén3, H. Mulder2, P. Brundin1.1Neuronal Survival Unit, Department of Experimental Medical Science, Wallenberg Neuroscience Center, Lund University, Sweden; 2Unit of Molecular Metabolism, Department of Experimental Medical Science, Lund University, Sweden; 3Unit of Clinical and Experimental Pharmacology, Department of Laboratory, Medicine, Lund University, Sweden
Huntington’s disease (HD) is a CAG triplet repeat disorder featuring neuronal loss in the striatum, cerebral cortex, and the hypothalamus. In the most studied HD mouse model for therapeutic trials, the R6/2 line, only minor neuronal death has been reported. Therefore neuronal cell death has not been possible to use as an outcome parameter in preclinical trials. We have, however, identified a progressive loss of orexin neurons in the lateral hypothalamus of R6/2 mice (
), leading to narcolepsy. Levels of orexin are also progressively reduced in the CSF of R6/2 mice. Another cell population in the lateral hypothalamus expresses the melanin concentrating hormone (MCH). Very recently, we detected a 38% reduction in the number of MCH positive neurons and the levels of MCH in CSF in 12 week old R6/2 mice. Furthermore, we have detected severe changes in the hypothalamic-pituitary-adrenal axis that cause a Cushing-like syndrome in R6/2 mice. Finally we have observed reduced levels of gonadotrophin releasing factor (GnRH) and testosterone deficits in R6/2 mice. Are these changes in the hypothalamus and endocrine systems relevant to clinical HD? We have observed reductions in the number of orexin neurons also in the lateral hypothalamus of HD patients. A recent study (
) suggests that circulating testosterone levels are reduced in HD patients. The possibility to measure hypothalamic peptides in the CSF and in plasma suggests that these novel neuroendocrine changes could be used as biomarkers to objectively monitor disease progression. As orexin loss also occurs in human HD, this cell population emerges as a therapeutic target for HD. Finally therapies aimed at correcting neuroendocrine changes in HD could possibly be an interesting approach to improve cognitive functions, depression, muscle mass, weight loss, and sleep disturbances in HD.
Keywords: endocrine; hypothalamus
Concurrent session IIb: clinical management 1
S026 NON-PHARMACOLOGICAL APPROACHES TO MANAGEMENT
A. E. Rosser.Clinical Neurosciences, Cardiff University, UK
Therapeutic options for Huntington’s disease are severely limited and no disease modifying treatment is available to date. Management requires a broad approach with consideration of family and domestic issues as well as addressing specific physical symptoms in the patient. Patients may be referred for specialised therapy such as physiotherapy for assessment and assistance with motor symptoms, and speech therapy for assessment and treatment of swallowing and speech abnormalities. However, there is a dearth of information as to the optimal strategies that should be employed using these approaches and their benefit or otherwise. Other symptoms, such as sleep disorders, are also poorly understood, management tends to be generic, and again its success has not been systematically assessed. Future non-pharmacological interventions may also include neurosurgical intervention to replace cells, or implant growth factors or stimulators. For advances to be made in all these areas it will be important to understand more about the underlying mechanisms that produce the symptoms and to assess the effects of interventions. There is an increasing tendency to manage Huntington’s disease patients in multidisciplinary clinics, although considerable variation exists depending on local resources and the availability of the appropriate expertise. A multidisciplinary approach facilitates the optimal use of available management options and will also be important in the development and implementation of potential emerging therapies.
S027 BALANCE DISORDERS IN HUNTINGTON’S DISEASE
Y. A. M. Grimbergen1, M. J. Knol2, B. R. Bloem2, H. P. H. Kremer2, R. A. C. Roos1, M. Munneke2.1Leiden University Medical Center, the Netherlands; 2Radboud University Nijmegen Medical Centre, the Netherlands
Aims: (1) To determine the incidence, circumstances, and clinical impact of falls in Huntington’s disease (HD). (2) To investigate the pathophysiology underlying falls in patients with HD.
Background: The clinical epidemiology of falls in HD has not been systematically studied. The pathophysiology of balance disorders in HD is likely complex, with possible contributions of chorea (causing excessive trunk sway), bradykinesia (causing slowed postural responses), and cognitive dysfunction (causing recklessness).
Methods: Forty five outpatients (23 women; mean age 51.9, range 28–71 years) answered a falls questionnaire. Clinical assessment included Unified Huntington’s Disease Rating Scale (UHDRS) and balance and gait analysis using pressure-sensitive walkway (GAITRite), trunk accelerometry (Swaystar system), and Berg Balance Test.
Results: Twenty seven (60%) patients reported multiple falls in the past year, 17 (38%) had fallen one or more times in the past month. Sixteen per cent (7/45) was afraid of falling and 29% (13/45) had stopped activities like cycling or climbing stairs. Both bradykinesia and chorea items of the UHDRS showed, after correction for age and disease duration, a significant correlation with multiple falls in the past year.
Discussion: Fall rates are high in HD. However, only a few patients were afraid of falling or tried to prevent serious falls. This may be due to behavioural or cognitive symptoms. Clinically both bradykinesia and chorea were related to falling. Ongoing quantitative analyses of balance and gait will further clarify whether excess chorea or bradykinesia is the most important determinant of falling.
S028 PREVALENCE OF PSYCHIATRIC DISORDERS IN DIFFERENT STAGES OF HUNTINGTON’S DISEASE
E. van Duijn1, F. G. Zitman1, A. Tibben2, R. A. C. Roos3, R. C. van der Mast4.Departments of 1Psychiatry, 2Clinical Genetics, 3Neurology and 4Psychiatry, Leiden University Medical Centre, the Netherlands
Objective: Huntington’s disease (HD) is, next to movement disorders and cognitive deterioration, characterised by behavioural problems and psychiatric disorders. Psychopathology is often described in symptomatic as well as pre(motor)symptomatic gene carriers. However, most studies on psychopathology in HD are hampered by methodological shortcomings, in particular a lack of a control group. The aim of our study was to investigate the prevalence of psychiatric disorders in different stages of HD, including pre(motor)symptomatic gene carriers, in comparison with a control group of non-gene carriers.
Materials and Methods: In a cross sectional observational study we recruited patients from the outpatient clinics of Neurology and Clinical Genetics. Most of the patients from the department of Neurology had movement disorders, and gene carriers from the department of Clinical Genetics were in general pre(motor)symptomatic. Further, we examined relatives who had an a priori 50% risk, but appeared to be gene negative. We used the sections anxiety (with the exception of specific phobia), depression, mania, psychosis/schizophrenia, obsessive-compulsive disorder, and cognitive disorder of the computerised version of the Composite International Diagnostic Interview 2.1 (CIDI-auto) to assess the 12 month and lifetime prevalence. Patients with a score <18 on the Mini-Mental State Examination were excluded because the CIDI is not validated for patients with such cognitive impairment.
Results: Preliminary results indicate that depressive disorder and generalised anxiety disorder (GAD) are the most frequent psychiatric disorders in both pre(motor)symptomatic and symptomatic gene carriers being more prevalent compared to non-gene carriers. Non-gene carriers were equally affected as the general population.
Conclusion: Depressive disorders and GAD are frequent comorbid disorders both in pre(motor)symptomatic and symptomatic stages. Because most of our symptomatic patients were in an early phase of the disease, these results do not yet represent the full course of psychopathology in HD.
Keywords: psychopathology; presymptomatic gene carriers; symptomatic gene carriers
S029 MONITORING THE MENTAL HEALTH AND WELLBEING OF THE PROSPECTIVE HUNTINGTON AT RISK OBSERVATIONAL STUDY (PHAROS) COHORT
E. P. Kayson, HuntingtonStudy Group PHAROS Investigators.University of Rochester; Rochester, NY, USA
Objective: PHAROS is an observational study to determine the early and gene specific signs of the onset of Huntington’s disease (HD) in an adult population at nominal 50:50 risk for carrying the HD gene.
Methods: Consenting research participants included unaffected adults at risk for HD, aged 26–55 years, who have chosen not to learn of their gene status but agreed to provide a DNA sample for de-identified analysis of HD gene status and undergo prospective clinical assessments every nine months. Mental health status was evaluated by the Unified Huntington’s Disease Rating Scale (UHDRS), Beck Depression Inventory (BDI I or II), histories of depression and suicidal behaviour, and the reporting of pre-specified events relevant to safety and feasibility.
Results: As of January 2004, 1001 participants (mean age 41.3 (SD 7.3) years; 689 women, 312 men) were enrolled at 43 research sites in North America. At baseline, a self-reported history of depression was more common in women (33.2%) than men (18.3%*), as was suicidal ideation (10.6% women, 6.4%* men), previous suicide attempts (4.9% women, 1.6%* men), and antidepressant treatment (15.8% women, 9.3%* men) (*p<0.05).
Conclusions: Adverse life events, depression, and the prospects of developing HD predispose the PHAROS cohort to mental health risks especially among women that require prospective assessment and clinical vigilance. Identification and minimisation of these risk factors will help protect the wellbeing of the PHAROS cohort and other research subjects who participate in therapeutic trials aimed at postponing the onset of HD.
Support: The National Institutes of Health (HG 02449), the Huntington’s Disease Society of America, the Hereditary Disease Foundation, and the High Q Foundation.
Keywords: at risk; mental health
Concurrent session IIIa: experimental therapeutics 1
S030 IDENTIFICATION AND CHARACTERISATION OF CHEMICAL COMPOUNDS AND PROTEINS THAT PREVENT THE SELF ASSEMBLY OF PROTEIN AGGREGATES IN HUNTINGTON’S DISEASE AND RELATED DISORDERS
E. E. Wanker.Max Delbrück Center for Molecular Medicine, Berlin-Buch, Germany
Huntington’s disease (HD) is an inherited progressive neurodegenerative disorder caused by an elongated polyglutamine (polyQ) repeat located at the N-terminus of huntingtin. The pathomechanism of HD as well as the normal function of huntingtin are unclear. HD exon 1 proteins with a polyQ stretch in the pathological range (>37 glutamines) form protein aggregates in vitro. In addition, the accumulation of insoluble polyQ-containing protein aggregates has been detected in intra and perinuclear inclusions of HD transgenic mice and patients, suggesting that processes that lead to the formation of insoluble protein aggregates are critical for HD pathogenesis.
Thus, preventing the formation of insoluble huntingtin aggregates in neurons of patients may represent an attractive therapeutic strategy to ameliorate HD. In order to identify htt aggregation inhibitors we have developed an automated filter retardation assay. Using this method we have screened a library of about 180 000 small molecules and identified 25 benzothiazole derivatives that inhibit HD exon 1 fibrillogenesis in a dose dependent manner. The results obtained by the filter assay were confirmed by immunoblotting, electon microscopy and mass spectrometry. Moreover, chemical compounds were identified that slow down htt aggregation and toxicity in cell based assays and fly model systems of HD. Currently, the mode of action of these compounds is analysed in detail using biochemical, biophysical, and cell biological methods. Our findings may provide the basis for a new therapeutic approach to prevent the accumulation htt aggregates in HD and related amyloid disorders.
Keywords: aggregation; amyloid
S031 ISOLATION OF INCLUSION BODIES AND FILAMENTS FROM A MOUSE MODEL OF HUNTINGTON’S DISEASE REVEALS THAT PROTEASOME INHIBITION DEPENDS ON THE DEGREE OF HUNTINGTIN AGGREGATION
A. G. Valera, M. Díaz-Hernández, F. Hernández, Z. Ortega, J. J. Lucas.Centro de Biologia Molecular Severo Ochoa, CSIC/UAM, Fac Ciencias, Universidad Autonoma de Madrid, Spain
The main histopathological feature of Huntington’s disease (HD) is the presence of inclusions bodies (IB) that are formed by huntingtin with an expanded polyglutamine (polyQ) sequence. IB also contains components of the ubiquitin proteasome system (UPS). It has been postulated that impairment of this machinery can be one of the causes of HD. However, it is not totally clear if UPS is inhibited in HD, nor which could be toxic forms of huntingtin according to its level of aggregation. Studies performed in vitro demonstrate that eukaryotic proteasomes cannot degrade soluble synthetic PolyQ which could get retained, thus inhibiting the proteasome (
). On the other hand, similar experiments with in vitro aggregated PolyQ did not detect impairment in proteasome activity (
). These studies with synthetic polyQ do not reflect protein context and postraductional modifications that are found in affected tissue. We recently described a protocol to isolate huntingtin filaments (
) from brains of the a conditional model of HD (Tet/HD94 mice) that express exon 1 mutant htt with 94Q in forebrain neurons, leading to formation of huntingtin aggregates (
). Here we describe a protocol to isolate IB from brain of Tet/HD94 mice. The method is based on magnetic sorting and its efficiency is confirmed by flow cytometry and immunofluorescence studies. The effect of isolated huntingtin filaments and IB on proteasome activity will be presented.
Keywords: proteasome; filaments; body inclusion
Concurrent session IIIb: clinical management 2 and markers of HD
S032 EHDI STUDY: EFFECT OF RILUZOLE ON HUNTINGTON’S DISEASE PROGRESSION
J. Garcia de Yebenes1, B. Dubois2, M. Dib2, H. P. H. Kremer3, H. Przuntek4, A. Ludolph5, B. Landwehrmeyer5, W. Gaus5, W. Fischer6, theEHDI-Study-Group.1Madrid, Spain; 2Paris, France; 3Nijmegen, the Netherlands; 4Bochum, Germany; 5Ulm, Germany; 6Aventis Pharma Deutschland, Berlin, Germany
Riluzole has been shown to modify disease progression in amyotrophic lateral sclerosis (ALS), resulting in improved survival rates compared to controls. Initial studies in a R6/2 transgenic mice indicated an increase in survival time for animals on riluzole and a fragmentation of neuronal intranuclear inclusions. Whether riluzole has a clinical effect in Huntington’s disease (HD) patients was studied in a multinational phase III, multicenter, double blind, placebo controlled trial, the EHDI trial. This trial assessed the effect of riluzole 50 mg b.i.d. for 36 months on the disease progression of HD. Primary efficacy parameters were change from baseline of the total functional capacity score (TFC) and the change from baseline of the motor score (MS) of the UHDRS as well as a combined score (CS) of TFC and MS after treatment with riluzole compared with placebo. Because of reports of a possible effect of riluzole on motor symptoms of HD, in particular chorea, the effect of riluzole on disease progression was assessed following a washout phase of one month after 36 months of treatment. Inclusion criteria for patients recruited in this study were the following: (a) age 25–65 years, (b) number of CAG repeats in the IT15 gene >36, (c) presence of clinical symptoms of the disease as defined by a motor score >5, and (d) initial stages of the disease as defined by TFC >8. The 537 patients that fulfilled these criteria were randomised in 43 centres from eight countries (France, Germany, Spain, the Netherlands, Italy, Austria, Switzerland, and Poland). After three years of treatment 366 HD patients completed the protocol. 171 (31.8%) dropped out for various reasons (adverse events, suicide and suicide attempts, start of antichoreic medication, etc). Results on disease progression will be discussed.
The study was sponsored by Aventis Pharma, a company of the Sanofi-Aventis group.
Keywords: EHDI study; riluzole; disease progression
S033 ETHYL-EPA IN HUNTINGTON’S DISEASE: A DOUBLE BLIND, RANDOMISED, PLACEBO CONTROLLED TRIAL
H. Murck1, M. Manku1, B. K. Puri2, B. R. Leavitt3, M. R. Hayden3, C. A. Ross4, A. Rosenblatt4, J. T. Greenamyre5, S. Hersch6, K. S. Vaddadi7.1Amarin Neuroscience Ltd., Stirling, UK; 2MRI Unit, MRC Clinical Sciences Centre, Imperial College, Hammersmith Hospital, London, UK; 3Department of Medical Genetics, Centre for Molecular Medicine and Therapeutics, University of British Columbia Hospital, Vancouver, Canada; 4Baltimore Huntington’s Disease Center, Department of Psychiatry, Johns Hopkins University School of Medicine, Baltimore, USA; 5Department of Neurology, Emory University School of Medicine, Atlanta, USA; 6Massachusetts General Hospital, Boston, USA; 7Department of Psychological Medicine, Monash Medical Centre, Clayton, Australia
Background: Preliminary evidence suggests beneficial effects of pure ethyl-eicosapentaenoate (ethyl-EPA) in Huntington’s disease (HD). Ethyl-EPA is suggested to stabilise mitochondrial integrity.
Methods: 135 patients with HD were randomised to enter a multicentre, double blind, placebo controlled trial on the efficacy of 2 g/d ethyl-EPA versus placebo. The Unified Huntington’s Disease Rating Scale (UHDRS) was used for assessment. The primary endpoint was outcome at 12 months on the Total Motor Score-4 subscale (TMS-4). Analysis of covariance (ANCOVA) and a χ2 test on response, defined as absence of increase on TMS-4, were performed.
Results: 121 patients completed 12 months and 83 did so without protocol violations (PP-cohort). Intent to treat (ITT) analysis revealed no significant difference between ethyl-EPA and placebo for TMS-4. In the per protocol (PP) cohort, ethyl-EPA was better than placebo on the χ2 test on TMS-4 (p 44 CAG repeats was consistent over the centres. Reported adverse events were distributed equally between treatment arms.
Conclusion: Ethyl-EPA (purity >95%) had no benefit in the intent to treat (ITT) cohort of patients with HD, but exploratory analysis revealed that a significantly higher number of patients in the PP cohort, treated with ethyl-EPA, showed stable or improved motor function. Furthermore the number of CAG repeats could be a predictor of response. Further studies of the potential efficacy of ethyl-EPA are warranted.
Keywords: fatty acids; clinical trial; motor dysfunction
S034 DEVELOPING A SCALE TO MEASURE THE QUALITY OF LIFE OF HUNTINGTON’S DISEASE SPOUSAL CARERS
A. Aubeeluck1, H. Buchanan2.1Derbyshire Royal Infirmary, UK; 2Centre for Psychological Research in Human Behaviour, University of Derby, UK
The purpose of this series of studies was to systematically investigate the factors that enhance and compromise the lives of Huntington’s disease (HD) spousal carers by using the theoretical construct of quality of life (QoL). Three exploratory studies provided evidence that spousal carers of HD patients have specific difficulties in maintaining their QoL while continuing in a primary caregiving role. Study 1 provided preliminary evidence that spousal carers of HD patients and healthcare professionals would value a disease specific QoL scale that could be used to evaluate spousal carers’ objective and subjective QoL. Study 2 established that spousal carers of HD patients often experience loneliness, a need to escape, and a unique sense of loss while trying to adequately care for their loved ones and maintain some form of QoL for themselves. Study 3 provided further evidence that QoL is compromised in many ways and is an issue for HD carers. The carers in this study often neglected their own needs as the caregiving role and disease processes “took over” their lives as well as the life of their HD affected spouse. The findings of these three studies prepared the way for the development of a disease specific QoL measure for spousal carers of HD patients. Validation of the Huntington’s disease Quality of Life Battery for Carers (HDQoL-C) was carried out in study 4. The HDQoL-C was established as a multidimensional and psychometrically sound disease specific and subjective QoL assessment tool, which incorporates the individual’s physical health, psychological state, level of independence, social relationships, personal beliefs, and relationship to salient features of the environment. It demonstrates good internal consistency, test-retest, and face validity. It is hoped that the HDQoL-C will be used in the future to quantify the caregiving experience in HD in order to implement and assess therapeutic interventions.
Keywords: spousal caregiving; quality of life
S035 UNEXPANDED CAG-REPEAT SIZE HAS NO INFLUENCE OF ON AGE AT ONSET IN HUNTINGTON’S DISEASE
P. H. Kraus1, C. Saft1, J. Andrich1, A. Hoffmann1, H. Przuntek1, L. Arning2, J. T. Epplen2, C. Kleiber3.1Department of Neurology, St Josef Hospital, Ruhr University Bochum, Germany; 2Department of Human Genetics, Ruhr University Bochum, Germany; 3University of Dortmund, Department of Statistics, Dortmund, Germany
The functional connection between the length of the expanded CAG-repeats and the age at onset in Huntington’s disease (HD) has been known for a long time. Usually logarithmic models are preferred in the literature. Such results were often overinterpreted concerning the possible pathomechanism as well as the “forecast” of the age at onset in the individual case.
Djoussé et al (2003) tested a multiple regression model with the expanded and the unexpanded CAG-repeat length plus a mathematical interaction term (product of both CAG-repeats). Under this condition the unexpanded CAG-repeat as well as especially the interaction term showed a significant contribution to the age at onset. The unexpanded CAG-repeat length does not contribute, however, any explained variance.
We carried out the outstanding confirmatory evaluation of this hypothesis with data from 230 unrelated HD patients from our centre and did not find any significant influence of the unexpanded CAG-repeat. Our estimated regression coefficients are rather similar to those presented by Djoussé et al. We also found expanded CAG to be significant at any reasonable level. However, neither unexpanded CAG nor the interaction term appears to belong to this model. Specifically, we were unable to reproduce Djoussé et al’s main finding of a significant interaction of expanded and unexpanded CAG. We therefore subjected the fitted model to a number of misspecification tests. Clearly, there appeared to be a problem with the model. For better practical understanding we tested the interaction model with random numbers instead of the unexpanded CAGs and found comparable significance values.
Whether there is an influence of unexpanded CAG-repeat length on the age at onset and whether or not the interaction between expanded and unexpanded CAGs plays any role is especially important for an understanding of the underlying basic pathomechanism. Following our results the answer to both questions has to be “no”.
Keywords: unexpanded CAG-repeat size; age at onset
Concurrent session IVa: experimental therapeutics 2
S036 EXPERIMENTAL THERAPEUTICS IN CELL CULTURE AND DROSOPHILA
L. M. Thompson, J. S. Steffan, B. L. Apostol, J. Pallos, N. Agrawal, K. Illes, D. E. Housman, A. Kazantsev, J. L. Marsh.Departments of Psychiatry and Human Behavior and Biological Chemistry, University of California, Irvine, USA
While cellular processes have been defined that are altered in Huntington’s disease (HD), the identification of treatments and cures has proven more elusive. The pathology of HD is complex, affecting multiple cellular pathways and processes including transcription, protein modification (for example, acetylation, SUMOylation, and ubiquitination), protein processing, neurotransmission, cytoskeleton, and mitochondrial function. Currently, no cure or effective treatment for this agonising and lethal disease exists and the process of finding drugs and therapies to treat human diseases can be slow, expensive, and frustrating. The development of cellular and drosophila model systems have significantly facilitated these efforts and have proven invaluable for functional assessment of specific pathways for drug development. A common feature of HD and other polyglutamine (polyQ) repeat diseases is the accumulation of polyQ-containing pathogenic proteins, leading to formation of visible aggregates (that is, inclusions) in affected regions of the brain, likely a result of abnormal protein folding and/or proteolytic cleavage of the htt protein. The process of aggregation can be recapitulated in cell culture and in vivo models. Although the contribution of inclusions to pathogenesis is unclear, cell based assays that can be used to screen for chemical compounds affecting aggregation may provide potential therapeutics and will be discussed. Further, we will focus on the use of drosophila to identify potential treatments for dominant neurodegenerative diseases such as HD and discuss how well these therapies translate into mammalian systems. As any single drug is likely to affect only some aspects of HD pathology, it may also be desirable to administer several drugs that target different mechanisms in the hopes of achieving greater relief from symptoms. Such a regimen has been tested in drosophila and results suggest that more modest doses of drugs may be used so as to avoid undesirable side effects caused by high drug doses. Several investigations of HD pathogenesis including the potential role of transcriptional dysregulation, mutant htt protein stability, and nucleocytoplasmic localisation will be highlighted.
Keywords: drosophila; treatment
S037 EXPERIMENTAL THERAPEUTICS IN MOUSE MODELS OF HUNTINGTON’S DISEASE
E. Hockly1, M. K. Lupton1, S. Sunshine1, J. Tse1, B. Woodman1, G. P. Bates1, A. P. Revington2, P. A. S. Lowden2.1Medical and Molecular Genetics, GKT School of Medicine, Guy’s Hospital, London, UK; 2School of Biological and Chemical Sciences, Birkbeck College, London, UK
Since the identification of the HD mutation in 1993, our understanding of the molecular pathogenesis of Huntington’s disease (HD) has improved at an exponential rate. As a consequence, there are an increasing number of compounds that can be considered as potential therapeutics for HD. These are either FDA approved drugs that can be postulated to benefit HD or compounds arising from high throughput screens of compound libraries using assays designed to specifically target stages in HD pathogenesis. Phase III clinical trials in HD patients are long and very expensive and therefore, it is important that we develop preclinical assessments that can predict the clinical outcome as far as possible. Currently, preclinical trials in mouse models of HD are most likely to be used to inform which compounds are taken forward into the clinic.
We have set out to establish rigorously standardised preclinical testing protocols for use with the R6/2 mouse model. As compounds are generally metabolised much faster in mouse than in humans, we design our administration regimes to best mimic the drug exposure that would occur in humans. Therefore, compounds are usually administered in the drinking water or food to allow steady state tissue concentrations to be achieved. Tissue concentrations in plasma, liver, and brain are measured routinely to assist in the interpretation of the outcome of the experiment. All of our preclinical trials are conducted in environmentally enriched conditions as we have shown that environmental enrichment alone can significantly improve R6/2 motor performance and, therefore, the compound must impart an additional beneficial effect. Treatment groups are matched according to their baseline performance in the behavioural tests before starting the trial in order to minimise artefactual results. Histone deacetylase inhibitors are one class of compounds that are emerging as promising therapeutics for HD.
Keywords: mouse models; treatment
Concurrent session IVb: late stage care
S038 LATE STAGE CARE IN HUNTINGTON’S DISEASE
S. A. Simpson.Department of Clinical Genetics, Aberdeen, UK
Huntington’s disease (HD) is a relentlessly progressive neurodegenerative disease which is presently incurable. Despite the hope for future therapies that exists for the families, they meantime are aware that there is little that their clinicians can do to delay either onset or progression of the disease. There are unique issues to address in a disorder where patients are aware in advance that their ability to communicate successfully, as well as their cognitive capacity, will become impaired. Most affected individuals have experience of the disease in its late stages because of their parent’s and other family member’s illness, and all have their own ideas and anxieties about how their own care ought to proceed. There is little evidence for guidelines for management at this stage of disease, although all clinicians involved in the care of HD will have their own experiences to share. I will present a review of the literature on clinical problems of late stage HD, and I will propose guidelines for management which will include discussion about advance directives for feeding and treatment, as well as placement for care.
Keywords: late stage care; advance directives; feeding
S039 CAPACITY AND ADVANCE DIRECTIVES
J. I. Bisson.University Hospital of Wales, Cardiff, UK
The Mental Capacity Act received Royal Assent in the United Kingdom in April 2005. It will provide a statutory framework for individuals who are not able to make their own decisions and those who want to plan ahead for a time when they may lose their capacity. The Act is likely to be extremely important in terms of the clinical care and management of individuals with Huntington’s disease and provides an opportunity to involve those affected in their ongoing care.
Advance directives involve decisions regarding future care made by individuals who are competent and come into force when they are no longer competent. There is no good evidence or clear consensus regarding when advance directives are best considered or made by individuals with Huntington’s disease. There has been considerable debate regarding the usefulness of them but most agree that they can extend individual autonomy. A major concern has been the difficulties associated with expecting individuals to provide authentic wishes regarding hypothetical situations when they have no experience of them. This is particularly pertinent in the early stages of Huntington’s disease but if advance directives are to be considered it is vital that this occurs while the individual remains competent and can effectively communicate their wishes.
This presentation will review advance directives and capacity from a clinical standpoint. The key issues surrounding capacity and its assessment in the context of Huntington’s disease will be reviewed and the development of a model of care and Huntington’s disease specific advance directives discussed.
Keywords: capacity; advance directive; competence
S040 STRUGGLE FOR QUALITY OF LIFE
D. Van der Wedden, A. B. Statius Muller, H. Claus.Overduin Nursing Home, the Netherlands
Caring for Huntington’s disease (HD) patients in the fifth stage of the disease (according to Shoulson and Fahn (1979)) has received little attention in the research and literature. The fifth stage of the disease is characterised by severely impaired capacity to perform activities of daily living. Most patients require residential care in this stage. Psychogeriatric nursing home “Overduin” in the Netherlands has a long tradition in caring for patients in the fifth stage. In 1974 the first HD patient was admitted. In 1991 a specialised unit for HD care was established for seven patients. Today we offer residential care to 70 HD patients. Moreover, 15 patients with moderately impaired capacities (stage 3–4) receive daycare. Average duration of residential stay is between five and 10 years. A nursing home physician coordinates a multidisciplinary team of health specialists that aims to eliminate or to compensate the devastating effects of the disease as much as possible. A pivotal principle is that the patient is considered as a participant in organising his or her care. This presentation addresses our guiding principles in offering care in the fifth stage, based on scientific knowledge and lessons from daily practice. Special attention will be given to the decisions that have to be made when life is ending but death has not yet arrived. When unambiguous communication with the patient is no longer possible in the final stage of the disease, it becomes hard to know what to decide according to ethical principles. Knowledge of the patient’s moral values and convictions/beliefs, documented during the earlier stages, may help us to do justice to the patient as well as to his or her partner, children, and close relatives. We suggest further research and international exchange of ideas and experiences.
Keywords: residential care; late stage care
S041 ACCOMMODATING THE COGNITIVE PHENOTYPE: A CHALLENGE TO NURSING HOMES AND CONSIDERATIONS FOR CARE
J. J. Pollard1, R. M. Stein2.1Laurel Lake Center, Lee, MA, USA; 2Center for Neurobehavioral Health, Lancaster, PA, USA
Huntington’s disease (HD) challenges even the most skilled nursing homes that care for residents in the mid and more advanced stages. Just as features of the movement disorder are often mistaken as intentional aggression, cognitive changes can complicate care and increase anger and aggression. Neuropsychology has learned more about both the common and unique cognitive features of HD. There is now a set of strategies available to health professionals to manage impulsive, disruptive behaviour and avoid episodes of extreme anger and aggression. A few simple but necessary principles must be integrated into planning recreational activities to actively engage residents. Similarly, nurses and other professional carers may consider these cognitive deficits as they approach their interactions with residents. From medication administration to assistance with bathing, recognition of the cognitive phenotype in nursing practice facilitates compliance with medication, therapy, care, and treatment.
The cognitive features of HD complicate one’s day-to-day activities. Health and residential care professionals can draw on a collection of techniques to help sufferers establish their own routines, facilitate their falling into the home’s more general routine and using this predictability to minimise confusion, frustration, anger, and aggression.
The presentation suggests by demonstration a close examination of resident’s daily schedule and possible unanticipated disruptions as a tool to provide a degree of comfort to residents as they encounter otherwise mundane changes. An approach to assisting someone with a shower that integrates routine, predictability, difficulty waiting, and minimal instructions is also presented.
Many residents with HD have pleasant experiences in their nursing homes. Others, though, can have a less problematic experience if staff draw on the knowledge base and become applied settings for the research of the last 20 years. In addition to medication management, physicians and psychologists can now recommend a set of environmental accommodations and staff interactions that may be helpful.
Keywords: cognition; care; routine
Tuesday 13th September
Plenary session IV: the way forward, development of new treatments for huntington’s disease
S042 EXPLORING RNA INTERFERENCE AS POTENTIAL THERAPY FOR HUNTINGTON’S DISEASE AND RELATED NEURODEGENERATIVE DISORDERS
H. Paulson.Carver College of Medicine, University of Iowa Hospitals and Clinics, Iowa City, USA
The recent discovery of RNA interference (RNAi), an evolutionarily conserved biological process through which small RNAs regulate specific transcripts, has revolutionised biological research. It also holds promise as a potential therapy for human diseases because it can be used to silence disease related genes. In RNAi, a small duplex of RNA complementary to a specific target gene suppresses its expression, either by degrading the targeted messenger RNA (mRNA) or by inhibiting its translation into protein. Naturally occurring inhibitory RNAs, termed microRNAs, normally regulate the expression of specific genes in the brain and elsewhere. The biological machinery of RNAi can be exploited by introducing gene specific, small inhibitory RNAs into cells that will suppress expression of the targeted gene. Untreatable neurological disorders caused by dominantly acting toxic gene products, such as Huntington’s disease (HD), constitute especially attractive targets for potential RNAi therapy. Here I will review the mechanisms underlying RNAi and describe several examples of RNAi mediated suppression of neurodegenerative disease genes, emphasising advances in applying this technology to HD. As with any new technology, RNAi holds great promise but also brings with it many unknowns. How best to deliver RNAi to the brain in HD? And can we target the HD gene product in a highly specific manner that does not result in deleterious, off target effects? This presentation will serve as an introduction to these and other key questions that must be answered if we hope to move RNAi into the HD clinic.
Keywords: RNAi; treatment
S043 STRIATAL TRANSPLANTATION
S. B. Dunnett.Brain Repair Group, School of Biosciences, Cardiff University, Cardiff, UK
Huntington’s disease (HD) can be modelled in experimental animals by excitotoxic or metabolic lesions of the striatum, or in transgenic mice carrying CAG expansion mutations in the huntingtin gene. In this animal model, embryonic striatal tissue survives transplantation into the striatum of adult lesioned hosts, where it differentiates into all major cell types of the striatum and establishes reciprocal afferent and efferent connections with the host brain. The grafts are functional at both physiological and behavioural levels, restoring LTD in the grafts in striatal slices, and ameliorating both motor and cognitive deficits in the experimental animals. On the basis of experimental animal studies, clinical trials of striatal tissue transplantation in HD have begun in a number centres in both North America and Europe. There are recent reports of safety of the neurosurgical operation from several centres, although one centre has experienced significant problems with subdural haemorrhage in three patients, which may relate to the relatively advanced stage of the disease in this study. Several MRI and PET studies, along with one postmortem study, indicate clear evidence for good graft survival comparable with that observed in the relevant animal models. One study has reported clear evidence of efficacy over several years post-transplantation, and a second centre reports anecdotal evidence for efficacy, but results from other centres are either non-significant or the trials have not yet been closed for analysis. The clinical trials indicate the need for careful translation of experimental protocols into the clinic, and highlight the need for well validated tools for multidimensional longitudinal assessment within a standardised design and over a significant postoperative duration. Although encouraging, results are still too preliminary to conclude whether neural transplantation will offer a practical future therapy for HD. In particular, if primary embryonic tissues do prove effective then it will be necessary to identify suitable, more readily available, quality assured sources of cells that could be used for practical therapy. Stem cells, whether from embryonic, fetal neural, or adult origin, are all under active exploration for this purpose. As an alternative to cell replacement, neuroprotection and gene replacement therapies are also under active investigation. In these cases, the issues of how to achieve stable trophic or gene delivery into deep brain targets remains a significant issue, for which transplantation of cells engineered ex vivo may provide an effective resolution.
Acknowledgements: the Cardiff studies are part of the NEST-UK clinical trial on the safety and feasibility of neural transplantation in early to moderate Huntington’s disease, funded by the MRC.
Keywords: transplantation; therapy
S044 EXPERIMENTAL THERAPEUTICS: PHARMACOLOGICAL THERAPIES
K. Kieburtz.University of Rochester Medical Center, Rochester, USA
Current pharmacological therapies can provide some relief from the symptoms of Huntington’s disease (HD), particularly mood disorders, but the areas of unmet therapeutic need are far in excess of the areas with effective therapy. Experimental pharmacological therapies are being developed for both symptom management and modification of disease progression. Active areas of investigation include the improvement of motor features (miraxion) and cognitive impairment (memantine). Initial investigations with these agents have lead to the planning of larger scale studies. In the area of disease modification, multiple compounds are being investigated. Depending on the amount of information available about compounds there are several types of trials underway. Initial safety and tolerability trials for relatively novel compounds such as phenylbutyrate assess the ability of HD patients to take these medications and help to identify appropriate dosages. Once a dosage has been identified and tolerability demonstrated, studies to assess whether there is initial evidence of any impact on disease progression are appropriate, and such a trial is currently planned for minocycline. Lastly, once controlled investigations demonstrate initial evidence of therapeutic benefit, large long term trials to demonstrate effectiveness in slowing functional decline in HD are appropriate. Currently such a trial is planned for coenzyme Q10 in North America, and a similar trial of riluzole is drawing to a close in Europe. In summary, there are several active areas of pharmacological investigation both for symptom control and for slowing of disease progression in HD. Given the potential compounds which will be emerging from preclinical investigation, a systematic approach for decision making and product development will add efficiency to the process of identifying effective pharmacological therapies for HD.
Keywords: experimental therapeutics
Plenary session V: clinical management 3
S045 HUNTINGTON’S DISEASE: CLINICAL CARE AND MANAGEMENT
M. A. Nance.Struthers Parkinson’s Center, Golden Valley, Minnesota, USA
Huntington’s disease (HD) is a chronic, genetic, neurodegenerative disorder that imposes unique challenges to patients, families, and medical care providers. Communication and community are essential to the successful management of the disease. I will present an overview of the continuum of medical care for HD through the stages of the illness. The integrated roles of the physician, nurse, mental health professionals, neuropsychologist, social worker, rehabilitation therapists, dietitian, genetic counsellor, and other health professionals will be reviewed. Novel strategies for pharmacological management will be discussed, and new approaches to care presented earlier in the conference will be reprised. The broad view of “community” includes a health team that participates in the events and lives of HD patients, as well as patients and families who support the clinical research efforts of HD professionals; examples of both will be provided. Until a cure for HD is identified, thoughtful care by dedicated health professionals, with the goal of preserving the quality of life, remains the gold standard of management for this disease.
Keywords: treatment; management; community
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