Elan D. Louis - US grants

Essential tremor (ET) is one of the most prevalent adult neurological disorders. Despite this, several fundamental clinical and genetic issues remain unknown: (1) The extent of familial aggregation is not known. (2) There are few quantitative data on the natural progression of disease, and the associations between disease progression, tremor distribution and tremor severity are not known. (3) There are few data on whether the degree of familial aggregation of ET is greater for certain subtypes of ET than for others (genetic heterogeneity). (4) Data on the mode of inheritance are almost exclusively derived from service or clinic-based studies, which may be biased towards an apparent autosomal dominant mode of inheritance. Additionally, all studies of this question have examined ethnically-homogeneous populations. The study proposal is the first with a case-control community-based shielded (blinded) design, and has the following aims: (1) to determine the extent of familial aggregation of ET, (2) to analyze the natural history of ET, and associations between different clinically-defined subtypes of ET (subtypes will be based on clinical features such as tremor distribution, severity, and age of onset), (3) to compare different clinically-defined subtypes of ET in terms of the extent of increased risk of ET within families, and (4) to test genetic and nongenetic models that could explain the familial distribution of ET. In families with three or more affected cases, blood specimens will be drawn from study subjects for future linkage analysis. Subjects will be selected from a community-based study of neurological disease in a multiethnic community in Washington Heights-Inwood, northern Manhattan, New York (NIH Grant # PO-1-AG07232-06, R. Mayeux, P.I.). Thirty-seven cases with ET, 37 matched controls, and 666 relatives of these cases and controls will be interviewed, examined, and videotaped using a standardized protocol. Data on disease characteristics and progression will be collected. Diagnoses will be assigned by two neurologists using a diagnostic protocol utilized in our previous study. Electrophysiological studies (tremor analysis) will be used to validate a proportion of all diagnoses. This applicant is trained as an academic clinical neurologist with specialization in clinical movement disorders and neuroepidemiology. This grant will enable him to develop an academic career in neurology and genetic epidemiology by allowing him (1) to collaborate with neurologists and genetic epidemiologists in the Sergievsky Center, (2) to learn methods of genetic epidemiology. including segregation analysis and eventually. linkage analysis, (3) to continue courses in the Columbia University School of Public Health. Drs. W. Allen Hauser, Ruth Ottman, Richard Mayeux and Stanley Fahn, all internationally recognized either within the areas of Neuroepidemiology or Movement Disorders, will provide invaluable guidance in these studies.

functional ability; tremor; pathologic process; disabling disease; clinical research; human subject;

abnormal involuntary movement; epidemiology; genetics; genetic susceptibility; family genetics; clinical research; human subject;

? DESCRIPTION (provided by applicant): Our research is devoted to studying the causes of tremor, and especially essential tremor (ET), which is the most common type of tremor. Since 2000, we have been investigating whether several environmental neurotoxins are associated with ET. A link between harmane (HA) (1- methyl-9H-pyrido[3,4-b]indole) and ET has been emerging from these studies, which show that blood and brain HA concentration ([HA]) is elevated in ET cases (esp. familial ET) vs. control subjects. HA is a neurotoxin present in the diet (esp. in meat). Administration of HA to laboratory animals produces severe action tremor resembling ET. Yet the link between HA and ET has not been convincingly established. All epidemiological studies have been case-control studies; thus, it is not clear whether high blood [HA] precedes the onset of ET. Aim 1 of this proposal will address this issue. The HA story has also become more complex and multi-dimensional. Thus, we were recently intrigued to find that blood [HA] was higher in Parkinson's disease (PD) cases than controls in New York. HA is structurally similar to MPTP, a neurotoxin closely linked with PD. ET and PD are both tremor disorders; some patients develop both disorders (ET+PD; i.e., they are comorbid for the two conditions). Whether the HA - PD link is reproducible, whether it tracks with the subtype of PD in which tremor rather than bradykinesia/rigidity is the predominant feature, and whether biomarker findings from blood also occur in the target organ of interest (i.e., the brain) in PD is not known. Aim 2 of this proposal will address this myriad of issues. Finally, whether individuals who are comorbid for both ET and PD have the highest blood [HA] is not known. Aim 3 of this proposal will address this issue. To close these gaps in knowledge, in this application, we propose a 5-year study with 3 inter-related aims that draw on several types of human tissue (blood, brain): AIM 1: To nail down the links between HA and ET by studying the association between baseline blood [HA] and the development of incident ET in a cohort study. AIM 2: To further solidify the emerging links between HA and PD by extending our observations to another country (Spain). AIM 3: To assess blood levels of HA in patients who have both ET and PD (ET+PD). This would be the only study heading in this direction - exploring the etiological role of environmental factors, and more specifically toxins, in ET. It would thus complement the many ongoing studies searching for ET genes. The study could lead to the clear identification of the first modifiable risk factor for ET (i.e., dietary HA).This would also be the only study assessing the possible etiological role and tissue concentrations of this toxin, HA, which is structurally similar to MPTP, in patients with PD.

DESCRIPTION (provided by applicant): Essential tremor (ET) is one of the most common neurological diseases yet it is also among the least studied. Few medications treat the disorder, which is usually progressive. Although it is as much as twenty times more prevalent than Parkinson's disease, at the time of our original application (2002), we noted that there were only 15 postmortems, most of which were from the pre-modern era. Hence, there was almost no knowledge of the underlying pathology of ET. Although often reiterated that 'there is no pathology' in ET, this was not based on rigorous study. Since 2003, our goal has been to establish the Essential Tremor Centralized Brain Repository to address a fundamental question in ET research: can an underlying pathology be identified in terms of morphological changes in specific brain regions? After intensively collecting and then studying 51 ET brains and 34 control brains, we have discovered that, indeed, there are identifiable pathological changes in the ET brain: 82.3% of ET brains have cerebellar degenerative changes in the form of increased numbers of torpedoes and mild reduction in Purkinje cell (PC) number (cerebellar ET) whereas 17.7% have brainstem Lewy bodies. Hence, at this point, we have described several basic changes in the ET brain. Clinical differences between the two pathologically-identified subtypes of ET have not been well studied. We now wish to move beyond our initial work. SPECIFIC AIM 1 is to advance our knowledge of the postmortem changes in patients with cerebellar ET (Aim 1A) and Lewy body ET (Aim 1B) through detailed studies of PC neuronal morphology. In Aim 1A, we will also begin to study neurofilament proteins. Because our previous analyses were confined to a single region of one cerebellar hemisphere, we will broaden our scope to include each of the other functional-anatomic regions of the cerebellum (Aim 1C). In Aim 1D, we will extend our analyses to the thalamus. SPECIFIC AIM 2 is to establish basic links between clinical features and postmortem brain changes (clinical-pathological correlation). The clinical evaluation in our 2002 application was, by design, brief and indirect (telephone and videotape). Now our aim is to conduct a comprehensive in- person clinical evaluation of 175 elderly ET cases, 44 of whom we expect to die during this five year proposal. In doing so, we can begin to identify the specific clinical features that characterize patients with each of the two pathological subtypes of ET. Our goal is to advance this field by: (1) increasing our understanding of the pathological anatomy of ET, and (2) forging the needed links between what physicians observe in living patients and what we uncover in detailed postmortem studies. PUBLIC HEALTH RELEVANCE Essential tremor (ET) is among the most common neurological diseases, yet until recently there had been very few postmortem studies. After intensively collecting and studying 51 ET brains and 34 control brains over the past 5 years, we have discovered that, indeed, there are identifiable pathological changes in the ET brain. Our aims in this competitive renewal application are to advance our knowledge of the postmortem changes in ET with more detailed quantitative morphological studies of Purkinje cells (Aim 1) and to establish basic links between clinical features and postmortem brain changes (Aim 2). Our tissue-based research will place us in unique a position to begin to address basic mechanistic questions about ET and may allow treating physicians to predict during life which subtype of ET a patient is likely to have.

Cardiovascular risk factors (diabetes, hyperinsutinemia, hypertension, hyperlipidemia), cerebrovascular disease, and Alzheimer's disease (AD) are some of the most common problems in the elderly and represent an important public health burden. These problems often coexist, but it is unclear if the relation between these problems is coincidental or causal. Given the public health importance of cardiovascular and cerebrovascular disease as well as AD, it is important to clarify their relation to one another. We propose to conduct longitudinal and cross-sectional studies of cardiovascular and cerebrovascular disease in relation to AD in the WHICAP II cohort, which began recruitment in 1999 of over 2,000 individuals to complement those still followed from WtllCAP I. We will use data from the baseline examinations in 1999 and from subsequent follow-up assessments. In addition, we propose to conduct a brain imaging in 1,000 individuals without dementia from WHICAP II at the second follow-up assessment that will include quantitative assessment of cerebrovascular disease and of imaging biomarkers of AD, namely hippocampal basal metabolism and hippocampal volumes. We also intend to study the association between the recently discovered haplotype of the phosphodiesterase gene (PDE4D) related to stroke in relation to the outcomes in this project. The assessment of cardiovascular risk factors will include the measurement of hyperinsulinemia, a potentially important risk factor for AD at baseline and the second, third, and fourth follow-ups. The following is a brief description of the aims of this project. AIMI: to conduct longitudinal studies of the associations between cardiovascular risk factors (including insulin and c-peptide) and mild cognitive impairment (MCI), AD, and cognitive decline. AIM 2: to conduct longitudinal studies of the associations between clinical stroke, white matter hyperintensities (WMH) and silent infarcts to MCI, AD, and cognitive decline. AIM 3: to conduct cross-sectional studies of the associations between cardiovascular risk factors and measures of hippocampal volume and basal metabolism. AIM 4: to conduct cross-sectional studies of the associations between clinical stroke, WMH and silent infarcts to imaging measures of hippocampal volume and basal metabolism. AIM 5: to conduct longitudinal studies of the associations between the gene encoding PDE4D and MCI, AD, cognitive decline, and measures of hippocampal volume and metabolism. This proposal provides a unique opportunity to study cardiovascular risk factors and eerebrovascular disease with great detail and in relation to several levels of AD related outcomes: imaging biomarkers, clinical precursors, and changes in specific neuropsychologieal profiles. In addition it is likely to advance the clarification of the mechanisms relating cardiovascular risk factors and cerebrovascular disease to MCI, AD and cognitive decline in the elderly.

environmental exposure; disease /disorder etiology; tremor; nervous system disorder epidemiology; disease /disorder proneness /risk; age difference; nonwater solvent; alkaloids; manganese; occupational health /safety; chlorohydrocarbon insecticide; patient oriented research; clinical research; human subject;

DESCRIPTION (provided by applicant):This is a proposal for continuation of support for a training program in Neuroepidemiology. It is the only NIH funded neuroepidemiology program in the United States. The goal of the program is to prepare neurologists and other research scientists for research careers in the epidemiology of neurologic disorders. Since its inception, the program has trained neurologists and neuroscientists who are now professors (5), associate professors (8) assistant professors (12) or career research scientists at the NIH and elsewhere (14). The program has capitalized upon the strengths of the Department of Neurology, the Division of Epidemiology and Biostatistics (Mailman School of Public Health, and the inter-disciplinary structure of the Gertrude H. Seregievsky Center, all at Columbia University; to provide stimulating training in a research environment for developing neuroscientists who wish to use epidemiologic methods to study diseases of the nervous system, and have as a career goal, a research or academic position. The structured training provided by the curriculum of the Mailman School of Public health, combined with the opportunity to participate in and expand upon ongoing epidemiologic studies of neurologic disease being conducted by program faculty, provide an optimal training federal government or accepted academic positions in which they have successfully competed for independent funding from the NIH and other sources. We are requesting support for four MD/DO neurologists or appropriate postdoctoral neuroscientist (Ph.D. or equivalent) each year for 5 years. All trainees will spend a minimum of 2 years in the program, during which time sequenced didactic course work in epidemiology and biostatistics, will be mixed with increasingly independent research activity. A degree is recommended, but not required.

Essential tremor (ET) is one of the most common neurological diseases yet it is also among the least studied. Few medications treat the disorder, which is usually progressive. Although it is as much as twenty times more prevalent than Parkinson?s disease, at the time of our original application (2002), we noted that there were only 15 postmortems, most of which were from the pre-modern era. Hence, there was almost no knowledge of the underlying pathology of ET. Although often reiterated that [unreadable]there is no pathology? in ET, this was not based on rigorous study. Since 2003, our goal has been to establish the Essential Tremor Centralized Brain Repository to address a fundamental question in ET research: can an underlying pathology be identified in terms of morphological changes in specific brain regions? After intensively collecting and then studying 46 ET brains and 32 control brains, we have discovered that, indeed, there are identifiable pathological changes in the ET brain: 80.4% of ET brains have cerebellar degenerative changes in the form of increased numbers of torpedoes and mild reduction in Purkinje cell (PC) number ([unreadable]cerebellar ET[unreadable]) whereas 19.6% have brainstem Lewy bodies. Hence, at this point, we have described several basic changes in the ET brain. Clinical differences between the two pathologically-identified subtypes of ET have not been well studied. We now wish to move beyond our initial work. SPECIFIC AIM 1 is to advance our knowledge of the postmortem changes in patients with cerebellar ET (Aim 1A) and Lewy body ET (Aim 1B) through detailed studies of PC neuronal morphology. Because our analyses have thus far been confined to a single region of one cerebellar hemisphere, we will broaden our scope to include each of the other functional-anatomic regions of the cerebellum (Aim 1C). Through Aim 1, we will test a hypothesis (disease model) for each pathological subtype of ET. SPECIFIC AIM 2 is to establish basic links between clinical features and postmortem brain changes (clinical-pathological correlation). The clinical evaluation in our 2002 application was, by design, brief and indirect (telephone and videotape). Now our aim is to conduct a comprehensive in-person clinical evaluation of 175 elderly ET cases, 42 of whom we expect to die during this five year proposal. In doing so, we can begin to identify the specific clinical features that characterize patients with each of the two pathological subtypes of ET. Our goal is to advance this field by: (1) increasing our understanding of the pathological anatomy of ET, and (2) forging the needed links between what physicians observe in living patients and what we uncover in detailed postmortem studies.

DESCRIPTION (provided by applicant): Essential tremor (ET) is among the most common neurological diseases, with a prevalence (age >40 years) estimated to be 4.0% and prevalence in advanced age (>90 years) exceeding 20.0%. The underlying pathogenesis remains poorly understood and, as a consequence, current medications are empiric and of limited efficacy. There are only two front-line medications, a situation that has not changed in more than 30 years, and one in two patients simply stops these medications due to poor efficacy. The foremost obstacle to the study of pathogenesis is the absence of an animal (genetic) model for this disease. ET (often referred to as "familial tremor"), is generally regarded as a highly-genetic disorder, with physicians commonly seeing families with affecteds over multiple generations, and twin studies showing high concordance among monozygotes. Despite this, as of 2010, genetic studies have not advanced to the point where susceptibility genes have been identified. Previously published studies of linkage in families suggest that susceptibility loci contribute to the etiology of ET. In the current application we will build on previous studies and propose to use a linkage and resequencing approach to identify susceptibility genes for familial early-onset (<40 years) ET. To overcome the problems associated with previously published genetic studies of ET, which did not use strict phenotype definition in assigning affectedness status, we will use strict diagnostic criteria of 'definite'or 'probable'ET for inclusion of probands and affected individuals in families and further restrict our inclusion to individuals with pure ET (i.e. no dystonia) to reduce heterogeneity and to increase our power to detect a linkage signal. We will also focus on multiplex and multigenerational early onset ET families. To date we have already identified 96 families with an affected proband and >2 living first-degree relatives with ET and in 74 (77%) of families, the proband's age at onset was <40 years. PUBLIC HEALTH RELEVANCE: ET, a highly genetic disorder, is the most common cause of tremor in humans, affecting large numbers of individuals worldwide. Current treatments, which are largely unsuccessful, are empiric. Therapies based on an understanding of disease pathogenesis are needed, yet the absence of any identified genes and the resultant lack of an animal model, is the foremost obstacle standing in the way of these studies.

DESCRIPTION (provided by applicant): Despite its high prevalence, essential tremor (ET) it is among the least-studied and most poorly- understood neurological diseases. On the most basic biological level, little is known about its underlying pathologic-anatomy and pathophysiology. Recent postmortem studies report a 30 - 40% loss of Purkinje cells (PCs) in ET, suggesting that on a mechanistic level, this common neurological disease could be neurodegenerative. But postmortem results have been mixed. At the moment, the central debate in the ET field revolves around the question, is PC loss a feature of ET? Unfortunately, the approach to this question has thus far been limited to postmortem studies and a fresh approach is needed. PCs, in the cerebellar cortex, are the major storehouse of brain gamma-aminobutyric acid (GABA), releasing their GABA into the synaptic cleft at the level of the cerebellar dentate nucleus. Thus, cerebellar dentate GABA level is a convenient in vivo marker of PC number. Furthermore, N-acetylaspartate (NAA), an amino acid found in the cytosol of neurons, is a convenient in vivo marker of neuronal integrity in the cerebellar cortex. The long-term goal of the proposed research is to elucidate the basic nature of the underlying pathophysiology of ET. The objective of this research project, which is the next step toward attainment of this long-term goal, is to perform in-vivo magnetic resonance spectroscopy (MRS) to quantify levels of GABA in the cerebellar dentate and NAA in the cerebellar cortex in 50 ET cases vs. 50 controls, both cross-sectionally and longitudinally. The central hypothesis for the proposed research is that there is a progressive destruction of PCs in ET. We plan to accomplish the overall objective of this application by pursuing the following three aims. Aim 1: In this cross-sectional neuroimaging aim, we will use MRS at baseline (Years 1 - 2) to assess in vivo cerebellar dentate GABA levels and cerebellar cortex NAA levels (NAA/total creatine, tCR) in ET cases and controls. Aim 2: In this longitudinal neuroimaging aim, we will perform a second MRS study (Years 4 - 5) to assess in vivo cerebellar cortex NAA/tCR levels and, in an exploratory manner, dentate GABA levels, to determine whether there is a longitudinal decline in these levels in 50 ET cases in excess of any longitudinal decline in these levels in 50 controls. Aim 3: We will cross validate the in vivo MRS findings with postmortem histological and biochemical findings in the brains of 10 - 15 of 50 ET cases whom we expect to die during the 5 year study. We expect that the proposed research will elucidate the underlying disease pathophysiology and provide useful diagnostic biomarkers as well as markers of disease progression for future neuroprotective trials.

DESCRIPTION (provided by applicant): Although the most recognizable clinical feature of essential tremor (ET) is tremor, there is emerging evidence that non-motor features (esp. cognitive dysfunction) are present. A growing number of studies show that ET patients have poorer cognitive performance than age-matched controls. In some ET patients, the cognitive problems are severe. Also, recent epidemiological studies have demonstrated that ET patients are more likely to have mild cognitive impairment (MCI) than age-matched controls, and an increased risk of dementia. While ET appears to be a risk factor for the development of cognitive impairment, the cause is not currently known. The cerebellar basis for ET could contribute to cognitive impairment, yet there is other evidence that ET is associated with an increased risk of developing tau-related disorders (Alzheimer's disease [AD] and progressive supranuclear palsy [PSP]). This absence of a mechanistic understanding results in a difficult clinical predicament - there is presently no way to deduce whether a given ET patient, based on his/her observed cognitive features, has early AD, early PSP, or merely the expected cognitive profile of ET. We have no predictive guidelines for patients. What are the next steps? It is important to conclusively characterize the cognitive impairment of ET and to disentangle its component causes. The overall goal of the proposed research is to refine our understanding of this clinical-pathological entity. We aim to perform longitudinal neuropsychological examinations on 350 ET cases and postmortem neuropathological examinations on 110 of these who die over 5 years, matching them to 220 autopsied non-ET cases. The novel concepts/new hypotheses we now put forward are as follows: i) for reasons that are as yet unclear, ET itself predisposes to tauopathic changes in the brain; thus, by extension, even if one were to match for level of cognitive impairment (normal cognition, MCI, or mild dementia), ET cases would still have more tau pathology than non-ET cases, ii) the nature/features of the tauopathy of ET is likely to differ from that of non-ET cases, iii) ET pathology alone, is likely to be the prime cause of cognitive deficits in a subgroup of ET cases, and iv) within the mix of ET cases, it should be possible to map certain cognitive profiles onto certain pathologies. Our 5-year proposal has two aims: AIM 1: To study the neuropathological basis of cognitive deficits in ET. AIM 2: To provide the first comprehensive characterization of cognition in ET and to demonstrate that the severity of certain cognitive deficits predicts non-ET pathology in ET. We expect that this research will elucidate the processes of dementia in ET and shape the counseling and treatment of ET patients with cognitive symptoms.

? DESCRIPTION (provided by applicant): Over the past 5 - 8 years, we have identified a cluster of morphological changes in the essential tremor (ET) cerebellum, predominantly centered in/around the Purkinje cell (PC). The discovery of ET-related pathology has generated great interest but it has also raised difficult questions. Several of these pathologies have also been observed in primary cerebellar neurodegenerative diseases such as spinocerebellar ataxias (SCAs) and multiple system atrophy (MSA), but the degree to which these changes occur has not been formally studied or compared with that in ET. Interestingly, the cerebellum is now increasingly being implicated in tremor generation in other diseases such as Parkinson's disease (PD) and dystonia, yet their cerebellar pathology is presently unexplored. Hence, there is a large morphologic data gap. On a more primary level, we recently performed laser-capture microdissection (LCM) to specifically target PCs, thereby facilitating a precise evaluation of cell specific molecular changes in ET. We obtained a highly novel differential gene expression profile by direct sequencing of RNA (RNA-seq) isolated from PCs of ET vs. control brains. We identified 47 differentially expressed transcripts, which code for proteins that regulate neuronal function. However, a parallel set of LCM-RNA-seq studies, exploring the molecular biology of PCs in PD, dystonia, MSA and SCA, have yet to be performed. This represents a second, large molecular, data gap. This five-year proposal, which uses postmortem tissue from patients with ET well as from patients with a range of other cerebellar disorders, has two aims. Specific Aim 1: To undertake detailed postmortem studies of the cerebellum, comparing morphological changes in the cerebellum of ET patients to those of patients with primary cerebellar degenerative diseases (SCA and MSA) as well as those of patients with neurological diseases with tremor and cerebellar involvement (PD and dystonia). We will assemble an initial discovery sample of 160 brains (50 ET, 25 SCA, 15 MSA, 30 PD, 15 dystonia, 25 controls) as well as a replicate sample of 160 brains, assessing pathological changes across several cerebellar compartments. Hierarchical cluster analysis of quantified variables will be used to determine whether there is a definable ET cluster as well as definable clusters for each of these other four diseases. Specific Aim 2: To explore the molecular biology of PCs across neurodegenerative diseases characterized by cerebellar involvement and/or tremor. Using a novel LCM-RNA-seq approach, we will determine whether molecular expression changes in PCs are the same or differ across these diseases. For these novel molecular studies, we propose to use 60 brains (10 each of ET, SCA, MSA, PD, dystonia, controls).

Over the past 5 - 8 years, we have identified a cluster of morphological changes in the essential tremor (ET) cerebellum, predominantly centered in/around the Purkinje cell (PC). The discovery of ET-related pathology has generated great interest but it has also raised difficult questions. Several of these pathologies have also been observed in primary cerebellar neurodegenerative diseases such as spinocerebellar ataxias (SCAs) and multiple system atrophy (MSA), but the degree to which these changes occur has not been formally studied or compared with that in ET. Interestingly, the cerebellum is now increasingly being implicated in tremor generation in other diseases such as Parkinson's disease (PD) and dystonia, yet their cerebellar pathology is presently unexplored. Hence, there is a large morphologic data gap. On a more primary level, we recently performed laser-capture microdissection (LCM) to specifically target PCs, thereby facilitating a precise evaluation of cell-specific molecular changes in ET. We obtained a highly novel differential gene expression profile by direct sequencing of RNA (RNA-seq) isolated from PCs of ET vs. control brains. We identified 47 differentially expressed transcripts, which code for proteins that regulate neuronal function. However, a parallel set of LCM-RNA-seq studies, exploring the molecular biology of PCs in PD, dystonia, MSA and SCA, have yet to be performed. This represents a second, large molecular, data gap. This five-year proposal, which uses postmortem tissue from patients with ET well as from patients with a range of other cerebellar disorders, has two aims. Specific Aim 1: To undertake detailed postmortem studies of the cerebellum, comparing morphological changes in the cerebellum of ET patients to those of patients with primary cerebellar degenerative diseases (SCA and MSA) as well as those of patients with neurological diseases with tremor and cerebellar involvement (PD and dystonia). We will assemble an initial discovery sample of 160 brains (50 ET, 25 SCA, 15 MSA, 30 PD, 15 dystonia, 25 controls) as well as a replicate sample of 160 brains, assessing pathological changes across several cerebellar compartments. Hierarchical cluster analysis of quantified variables will be used to determine whether there is a definable ?ET cluster? as well as definable clusters for each of these other four diseases. Specific Aim 2: To explore the molecular biology of PCs across neurodegenerative diseases characterized by cerebellar involvement and/or tremor. Using a novel LCM-RNA-seq approach, we will determine whether molecular expression changes in PCs are the same or differ across these diseases. For these novel molecular studies, we propose to use 60 brains (10 each of ET, SCA, MSA, PD, dystonia, controls).