Pierre Burkhard

Proteomics in human Parkinson's disease research

During the last decades, considerable advances in the understanding of specific mechanisms underlying neurodegeneration in Parkinsons disease have been achieved, yet neither definite etiology nor unifying sequence of molecular events has been formally established. Current unmet needs in Parkinsons disease research include exploring new hypotheses regarding disease susceptibility, occurrence and progression, identifying reliable diagnostic, prognostic and therapeutic biomarkers, and translating basic research into appropriate disease-modifying strategies. The most popular view proposes that Parkinsons disease results from the complex interplay between genetic and environmental factors and mechanisms believed to be at work include oxidative stress, mitochondrial dysfunction, excitotoxicity, iron deposition and inflammation. More recently, a plethora of data has accumulated pinpointing an abnormal processing of the neuronal protein alpha-synuclein as a pivotal mechanism leading to aggregation, inclusions formation and degeneration. This protein-oriented scenario logically opens the door to the application of proteomic strategies to this field of research. We here review the current literature on proteomics applied to Parkinsons disease research, with particular emphasis on pathogenesis of sporadic Parkinsons disease in humans. We propose the view that Parkinsons disease may be an acquired or genetically-determined brain proteinopathy involving an abnormal processing of several, rather than individual neuronal proteins, and discuss some pre-analytical and analytical developments in proteomics that may help in verifying this concept.

Study of a Swiss dopa-responsive dystonia family with a deletion in GCH1: Redefining DYT14 as DYT5

Objective: To report the study of a multigenerational Swiss family with dopa-responsive dystonia (DRD). Methods: Clinical investigation was made of available family members, including historical and chart reviews. Subject examinations were video recorded. Genetic analysis included a genome-wide linkage study with microsatellite markers (STR), GTP cyclohydrolase I (GCH1) gene sequencing, and dosage analysis. Results: We evaluated 32 individuals, of whom 6 were clinically diagnosed with DRD, with childhood-onset progressive foot dystonia, later generalizing, followed by parkinsonism in the two older patients. The response to levodopa was very good. Two additional patients had late onset dopa-responsive parkinsonism. Three other subjects had DRD symptoms on historical grounds. We found suggestive linkage to the previously reported DYT14 locus, which excluded GCH1. However, further study with more stringent criteria for disease status attribution showed linkage to a larger region, which included GCH1. No mutation was found in GCH1 by gene sequencing but dosage methods identified a novel heterozygous deletion of exons 3 to 6 of GCH1. The mutation was found in seven subjects. One of the patients with dystonia represented a phenocopy. Conclusions: This study rules out the previously reported DYT14 locus as a cause of disease, as a novel multiexonic deletion was identified in GCH1. This work highlights the necessity of an accurate clinical diagnosis in linkage studies as well as the need for appropriate allele frequencies, penetrance, and phenocopy estimates. Comprehensive sequencing and dosage analysis of known genes is recommended prior to genome-wide linkage analysis. GLOSSARY: DRD = dopa-responsive dystonia; GCH1 = GTP cyclohydrolase I; SNP = single nucleotide polymorphisms; STR = short tandem repeats.

Individual Detection of Patients with Parkinson Disease using Support Vector Machine Analysis of Diffusion Tensor Imaging Data: Initial Results

BACKGROUND AND PURPOSE: Brain MR imaging is routinely performed in the work-up of suspected PD, yet its role is essentially limited to the exclusion of other pathologies. We performed a pattern-recognition analysis based on DTI data to detect subjects with PD at the individual level. MATERIALS AND METHODS: We included 40 consecutive patients with Parkinsonism suggestive of PD who had DTI at 3T, brain 123I ioflupane SPECT (DaTSCAN), and extensive neurologic testing including follow-up (17 PD: age range, 67.8 ± 6.7 years; 9 women; 23 Other: consisting of atypical forms of Parkinsonism; age range, 67.2 ± 9.7 years; 7 women). Data analysis included group-level TBSS and individual-level SVM classification. RESULTS: At the group level, patients with PD versus Other had spatially consistent increase in FA and decrease in RD and MD in a bilateral network, predominantly in the right frontal white matter. At the individual level, SVM correctly classified patients with PD at the individual level with accuracies up to 97%. CONCLUSIONS: Support vector machine–based pattern recognition of DTI data provides highly accurate detection of patients with PD among those with suspected PD at an individual level, which is potentially clinically applicable. Because most suspected subjects with PD undergo brain MR imaging, already existing MR imaging data may be reused; this practice is very cost-efficient.

Proteomic analysis of human substantia nigra identifies novel candidates involved in Parkinson's disease pathogenesis.

Parkinsons disease (PD) pathology spreads throughout the brain following a region‐specific process predominantly affecting the substantia nigra (SN) pars compacta. SN exhibits a progressive loss of dopaminergic neurons responsible for the major cardinal motor symptoms, along with the occurrence of Lewy bodies in the surviving neurons. To gain new insights into the underlying pathogenic mechanisms in PD, we studied postmortem nigral tissues dissected from pathologically confirmed PD cases (n = 5) and neurologically intact controls (n = 8). Using a high‐throughput shotgun proteomic strategy, we simultaneously identified 1795 proteins with concomitant quantitative data. To date, this represents the most extensive catalog of nigral proteins. Of them, 204 proteins displayed significant expression level changes in PD patients versus controls. These were involved in novel or known pathogenic processes including mitochondrial dysfunction, oxidative stress, or cytoskeleton impairment. We further characterized four candidates that might be relevant to PD pathogenesis. We confirmed the differential expression of ferritin‐L and seipin by Western blot and demonstrated the neuronal localization of gamma glutamyl hydrolase and nebulette by immunohistochemistry. Our preliminary findings suggest a role for nebulette overexpression in PD neurodegeneration, through mechanisms that may involve cytoskeleton dynamics disruption. All MS data have been deposited in the ProteomeXchange with identifier PXD000427 (http://proteomecentral.proteomexchange.org/dataset/PXD000427).

Neuropathology of dementia in a large cohort of patients with Parkinson's disease

The aim of our study was to establish the contribution of distinct pathological aggregates (cortical Lewy bodies (LB), neuronal tau-inclusions and β-amyloid plaque (Aβ) deposition) in dementia related to Parkinsons disease (PD) in a large autopsy cohort. We studied the brains of 155 PD patients, 109 of whom were clinically demented. The total LB score, the Braak stages for neurofibrillary tangles (NFT) and the Thal phases for Aβ deposition were assessed in each case, according to previously published guidelines. All the three lesion types were more abundant in the demented PD group, compared to the non-demented PD group, but neocortical LB pathology was the most important substrate of dementia. A significant correlation was found between the severity of Aβ phases, NFT stages and cortical LB scores. In a subgroup of severely demented PD patients, cortical tau burden was much higher than in the rest of the group. Extensive cortical NFTs associate unavoidably with dementia. Some patients remain cognitively intact despite high cortical LB score. In conclusion, our data strongly support a combining, yet distinct role of neocortical LBs and tau deposits.

A Novel Approach to Reducing Number of Sensing Units for Wearable Gait Analysis Systems

Gait analysis methods to estimate spatiotemporal measures, based on two, three or four gyroscopes attached on lower limbs have been discussed in the literature. The most common approach to reduce the number of sensing units is to simplify the underlying biomechanical gait model. In this study, we propose a novel method based on prediction of movements of thighs from movements of shanks. Datasets from three previous studies were used. Data from the first study (ten healthy subjects and ten with Parkinsons disease) were used to develop and calibrate a system with only two gyroscopes attached on shanks. Data from two other studies (36 subjects with hip replacement, seven subjects with coxarthrosis, and eight control subjects) were used for comparison with the other methods and for assessment of error compared to a motion capture system. Results show that the error of estimation of stride length compared to motion capture with the system with four gyroscopes and our new method based on two gyroscopes was close ( -0.8 ±6.6 versus 3.8 ±6.6 cm). An alternative with three sensing units did not show better results (error: -0.2 ±8.4 cm). Finally, a fourth that also used two units but with a simpler gait model had the highest bias compared to the reference (error: -25.6 ±7.6 cm). We concluded that it is feasible to estimate movements of thighs from movements of shanks to reduce number of needed sensing units from 4 to 2 in context of ambulatory gait analysis.

Differentiation between Parkinson disease and other forms of Parkinsonism using support vector machine analysis of susceptibility-weighted imaging (SWI): initial results

ObjectivesTo diagnose Parkinson disease (PD) at the individual level using pattern recognition of brain susceptibility-weighted imaging (SWI).MethodsWe analysed brain SWI in 36 consecutive patients with Parkinsonism suggestive of PD who had (1) SWI at 3xa0T, (2) brain 123I-ioflupane SPECT and (3) extensive neurological testing including follow-up (16 PD, 67.4u2009±u20096.2xa0years, 11 female; 20 OTHER, a heterogeneous group of atypical Parkinsonism syndromes 65.2u2009±u200912.5xa0years, 6 female). Analysis included group-level comparison of SWI values and individual-level support vector machine (SVM) analysis.ResultsAt the group level, simple visual analysis yielded no differences between groups. However, the group-level analyses demonstrated increased SWI in the bilateral thalamus and left substantia nigra in PD patients versus other Parkinsonism. The inverse comparison yielded no supra-threshold clusters. At the individual level, SVM correctly classified PD patients with an accuracy above 86xa0%.ConclusionsSVM pattern recognition of SWI data provides accurate discrimination of PD among patients with various forms of Parkinsonism at an individual level, despite the absence of visually detectable alterations. This pilot study warrants further confirmation in a larger cohort of PD patients and with different MR machines and MR parameters.Key Points• Magnetic resonance imaging data offers new insights into Parkinson’s disease• Visual susceptibility-weighted imaging (SWI) analysis could not discriminate idiopathic from atypical PD• However, support vector machine (SVM) analysis provided highly accurate detection of idiopathic PD• SVM analysis may contribute to the clinical diagnosis of individual PD patients• Such information can be readily obtained from routine MR data

Proteomic profiling of the substantia nigra demonstrates CNDP2 overexpression in Parkinson's disease.

Despite decades of intensive investigations, the precise sequence of molecular events and the specific proteins mediating the degenerative process underlying Parkinsons disease (PD) remain unraveled. Proteomic strategies may provide unbiased tools to identify novel candidates and explore original mechanisms involved in PD. Substantia nigra pars compacta (SN) tissue, whose degeneration is the hallmark of PD, was dissected from neuropathologically confirmed PD patients (n=3) and control subjects (n=3), before being submitted to a comparative 2-DE analysis. The present study revealed a subset of neuronal and/or glial proteins that appears to be deregulated in PD and likely to contribute to neurodegeneration. Observed alterations not only consolidate well accepted concepts surrounding PD pathogenesis such as oxidative stress and mitochondrial dysfunction but also point out to novel pathways. Among the latter, cytosolic non specific dipeptidase 2 (CNDP2), a relatively unknown protein not yet reported to be associated with PD pathogenesis, was shown to be increased in the SN of PD patients, as confirmed by Western blot. Immunohistochemical analyses demonstrated the presence of CNDP2 within the cytoplasm of SN dopaminergic neurons. Altogether, our findings support a key role of CNDP2 in PD neurodegeneration, by mechanisms that could involve oxidative stress, protein aggregation or inflammation. This article is part of a Special Issue entitled: Translational Proteomics.

Exploring the human tear fluid: Discovery of new biomarkers in multiple sclerosis

Multiple sclerosis is the first cause of progressive neurological disability among young adults living in Western countries. Its diagnosis is mostly based on clinical evaluation, neuroimaging, and in some cases cerebrospinal fluid (CSF) analysis, but no definitive diagnostic test exists. We proposed here that the exploration of tears from multiple sclerosis patients could lead to the discovery of new biomarkers.

Acute and subacute drug-induced movement disorders

Many pharmacological agents may induce a variety of movement disorders, including dystonia, tremor, parkinsonism, myoclonus and dyskinesia, with an acute, subacute or more chronic time course. Motor symptoms may be isolated or part of a more extensive cerebral or systemic condition, such as the neuroleptic malignant syndrome or the serotonin syndrome. Drug-induced movement disorders share a number of features that should make them easy to identify, including a clear temporal relationship between medication initiation and symptom onset, a dose-effect, and, with the exception of tardive syndromes, complete resolution after discontinuation of the offending agent. Diagnosis relies on a thorough medication history. Medications commonly involved include dopamine receptor blockers, antidepressants and anti-epileptics, among many others. Mechanisms underlying drug-induced movement disorders involve blockade, facilitation or imbalance of dopamine, serotonin, noradrenaline and cholinergic neurotransmission in the basal ganglia. The present review focuses on drug-induced movement disorders that typically develop as an acute (hours to days) or subacute (days to weeks) event, including acute dystonic reactions, akathisia, drug-induced parkinsonism, neuroleptic malignant syndrome, serotonin syndrome, parkinsonism-hyperpyrexia syndrome, drug-induced tremor, drug-induced hyperkinesias and movement disorders associated with the use of recreational drugs.