No description available.

Neurodegenerative Erkrankungen (NDs) wie Alzheimer (AD), Parkinson (PD), und amyotrophe lateral Sklerose (ALS) sind Hirnerkrankungen, die durch unlösliche Proteinaggregate in Neuronen oder im Extrazellularraum charakterisiert sind. In dieser Arbeit habe ich für verschiede bekannte und vorhergesagte neurodegenerative Krankheitsproteine (NDPs) Proteininteraktionsnetzwerke erstellt, um mögliche gemeinsame Krankheitsmechanismen genauer zu studieren. Mit Hilfe eines automatisierten Hefe-Zwei-Hybrid-Systems (Y2H) konnte ich 18.663 Protein-Protein-Interaktionen (PPIs) für 449 wildtyp und 22 mutierte Proteine identifizieren. Eine genaue funktionelle Analyse der Interaktionspartner von korrespondierenden wildtyp und mutierten Proteinen ergab deutliche Unterschiede zum einen im Fall von allen untersuchten Proteinen und insbesondere im Fall vom ALS Krankheitsprotein TDP-43. Die identifizierten PPIs wurden außerdem verwendet um krankheitsspezifische Netzwerke zu erstellen und um Proteine zu identifizieren, die mit mehreren NDPs verbunden sind. Ich habe auf diese Weise vier Proteine (APP, IQSEC1, ZNF179 und ZMAT2) gefunden, die mit bekannten NDPs with Huntingtin, TDP-43, Parkin und Ataxin-1 interagieren und so fünf verschiedene NDs miteinander verbinden. Die Reduktion der mRNA Expression von IQSEC1, ZNF179 oder ZMAT2 mit Hilfe von siRNA führte zu einer Verstärkung von pathogenen Mechanismen wie der Aggregation von mutiertem Huntingtin und TDP-43 sowie der Hyperphosphorylierung des Proteins Tau. Außerdem habe ich 22 Proteine entdeckt, die die Aggregation von TDP-43 deutlich verändern und außerdem Mitglieder in sieben vorhergesagten Proteinkomplexen sind. Die Proteinkomplexe habe ich durch Kombination von Interaktionsdaten und Daten eines siRNA Screenings vorhergesagt. Zusätzlich habe ich herausgefunden, dass die Proteine eines vorhergesagten Komplexes, nämlich HDAC1, pRB, HP1, BRG1 und c-MYC, die Aggregation von TDP-43 durch Veränderung von dessen Genexpression beeinflussen. / Neurodegenerative diseases (NDs) such as Alzheimer’s disease (AD), Parkinson’s disease (PD) or amyotrophic lateral sclerosis (ALS) are progressive brain disorders characterized by the accumulation of insoluble protein aggregates in neuronal cells or the extracellular space of patient brains. To elucidate potential common pathological mechanisms in different NDs, I created comprehensive interaction networks for various known and predicted neurodegenerative disease proteins (NDPs). I identified 18,663 protein-protein interactions (PPIs) for 449 bioinformatically selected wild-type target proteins and 22 mutant variants of 11 known NDPs by using an automated yeast two-hybrid (Y2H) system. The functional analysis of the interaction partners of corresponding wild-type and mutant NDPs revealed strong differences in the case of all 11 NDPs and especially for the ALS protein TDP-43. The identified PPIs were used to generate networks for individual NDs such as AD or PD and to identify proteins that are connected to multiple NDPs. For example, I found that five neurodegenerative diseases are connected by four proteins (APP, ZMAT2, ZNF179 and IQSEC1) that link known NDPs such as huntingtin, TDP-43, parkin, ataxin-1 and SOD1. Analysis of publicly available gene expression data suggested that the mRNA expression of the four proteins is abnormally altered in brains of ND patients. Moreover, the knock-down of IQSEC1, ZNF179 or ZMAT2 aggravates pathogenic disease mechanisms such as aggregation of mutant huntingtin or TDP-43 as well as hyperphosphorylation of tau. Additionally, I identified 22 modifiers of TDP-43 aggregation, which are members in 7 protein complexes. These complexes were predicted based on combined data from PPI as well as siRNA screenings. Finally, I found that the proteins HDAC1, pRB, HP1, BRG1 and c-MYC, which form one of the predicted complexes, influence TDP-43 aggregation by altering its mRNA expression.

Eine Gemeinsamkeit verschiedener neurodegenerativer Erkrankungen ist die abnormale Ansammlung von Proteinen im Gehirn, wie z. B. von alpha-Synuclein (Syn)-Aggregaten bei der Parkinson''schen Krankheit (PD) oder von Huntingtin (Htt)-Aggregaten bei Chorea Huntington (HD). Am Anfang dieser Studie wurde eine Bibliothek von ca. 5000 natürlichen Substanzen nach Inhibitoren der Htt-Aggregation durchsucht. Eine der wirksamen Substanzen war (-)-Epigallocatechingallat (EGCG), eine Verbindung, die in grünem und schwarzem Tee vorkommt. Die antioxidativen Eigenschaften von EGCG wurden bereits mit einer neuroprotektiven Wirkung in Verbindung gebracht, was EGCG zu einem vielversprechenden Kandidaten für die Entwicklung einer neuen Behandlungsmethode macht. Eine inhibierende Wirkung auf Proteinaggregation wurde jedoch bis jetzt noch nicht nachgewiesen. Diese Studie zeigt, dass EGCG die Aggregation von Htt und Syn hemmt, indem es dosisabhängig eine oligomere Proteinkonformation stabilisiert. Diese Oligomere wirken jedoch nicht als Keime in Aggregationsreaktionen. Zusätzlich verändert EGCG die Exposition bestimmter Epitope, die von konformationsspezifischen Antikörpern im Laufe der Aggregation erkannt werden. Daher könnte die Substanz Proteine, die zur Aggregation neigen, auf einen alternativen Faltungspfad in der Missfaltungskaskade führen. Weiterhin legen die Ergebnisse nahe, dass eine direkte Wechselwirkung zwischen EGCG und Proteinen in einer ungefalteten Konformation stattfindet. In verschiedenen Zellkultur-Modellsystemen verringerte EGCG die Toxizität, die von missgefalteten Proteinen ausgeht, was nahelegt, dass die neu geformten oligomeren Spezies nicht toxisch sind. EGCG könnte daher ein chemisches Chaperon darstellen, das die Missfaltung und Toxizität von Proteinen, die mit neurodegenerativen Krankheiten assoziiert sind, verringert. Die Substanz könnte daher die Basis zur Entwicklung einer neuen Therapie für diese unheilbaren Krankheiten darstellen. / A common feature of neurodegenerative disorders is the abnormal accumulation of aggregated protein the brain, such as alpha-Synuclein (Syn) aggregates in Parkinson''s disease (PD) and Huntingtin (Htt) aggregates in Huntington''s disease (HD). In this study, a library of approximately 5000 natural compounds was screened for inhibitors of Htt aggregation. One of the hits was (-)- Epigallocatechin gallate (EGCG), a compound present in green and black tea. The antioxidant properties of this substance have been linked to neuroprotection before, making it a promising candidate for the development of a treatment for neurodegenerative diseases. Inhibition of protein aggregation by EGCG, however, has not been demonstrated so far. This study shows that EGCG inhibits the aggregation of Htt and Syn by stabilizing an oligomeric conformation of the respective proteins in a dose-dependent manner. These oligomers do not seed the aggregation of Htt and Syn. Also, EGCG modifies the exposure of different epitopes recognized by conformation-specific antibodies during the aggregation process. The compound might therefore lead aggregation-prone proteins on an alternative folding pathway in the misfolding cascade. The results furthermore suggest that direct interaction occurs between EGCG and proteins in an unfolded conformation. EGCG also reduces toxicity caused by misfolded Htt or Syn in cell culture model systems, suggesting that the oligomeric protein species formed in the presence of EGCG are not toxic to living cells. EGCG might therefore represent a chemical chaperone that can modulate misfolding and toxicity of proteins associated with neurodegenerative diseases and could provide the basis for the development of a novel pharmacotherapy for these fatal disorders.

No description available.

Background: Parkinson disease (PD) is a neurodegenerative disorder with a variety of motor and nonmotor symptoms. Many of these symptoms can be monitored by eHealth solutions, including smartphone apps, wearable sensors, and camera systems. The usability of such systems is a key factor in long-term use, but not much is known about the predictors of successful use and preferable methods to assess usability in patients with PD. Objective: This study tested methods to assess usability and determined prerequisites for successful use in patients with PD. - Methods: We performed comprehensive usability assessments with 18 patients with PD using a mixed methods usability battery containing the System Usability Scale, a rater-based evaluation of device-specific tasks, and qualitative interviews. Each patient performed the usability battery with 2 of 3 randomly assigned devices: a tablet app, wearable sensors, and a camera system. The usability battery was administered at the beginning and at the end of a 4-day testing period. Between usability batteries, the systems were used by the patients during 3 sessions of motor assessments (wearable sensors and camera system) and at the movement disorder ward (tablet app). - Results: In this study, the rater-based evaluation of tasks discriminated the best between the 3 eHealth solutions, whereas subjective modalities such as the System Usability Scale were not able to distinguish between the systems. Successful use was associated with different clinical characteristics for each system: eHealth literacy and cognitive function predicted successful use of the tablet app, and bettermotor function and lower age correlated with the independent use of the camera system. The successful use of the wearable sensors was independent of clinical characteristics. Unfortunately, patients who were not able to use the devices well provided few improvement suggestions in qualitative interviews. Conclusions: eHealth solutions should be developed with a specific set of patients in mind and subsequently tested in this cohort. For a complete picture, usability assessments should include a rater-based evaluation of task performance, and there is a need to develop strategies to circumvent the underrepresentation of poorly performing patients in qualitative usability research.

Thesis (MScMedSc)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: Parkinson's disease (PD) is a severely debilitating neurodegenerative disorder that results in motor circuit dysregulation and ultimately, causes impairment of movement. This condition is due to the selective degradation of the dopaminergic neurons in the substantia nigra pars compacta in the midbrain, which subsequently results in the pathological symptoms namely bradykinesia, resting tremor, postural instability and rigidity. It was initially hypothesized that individuals who develop PD were exposed to an environmental trigger(s) that caused the onset of the disease, but more recently, a significant genetic component, coupled to environmental factors have been implicated in disease pathogenesis. Currently, there are eight genes (Parkin, PINK1, LRRK2, SNCA, DJ-1, ATP13A2, EIF4G1 and VPS35) that have been directly implicated in PD. Worldwide, the prevalence of neurodegenerative disorders is increasing as populations are living longer. In Europe, Canada and USA, it has been projected that the prevalence of PD may increase by a factor of two between 2010 and 2050; approximately a 92% increase. In Tanzania (the only study done in sub-Saharan Africa) an even larger increase of 184% between 2005 and 2025 is predicted, due to the fact that the speed of populations ageing in developing countries, will exceed that of developed countries. Research into the causes and risk factors underlying neurodegenerative disorders such as PD is therefore urgently needed for policy makers and governments in developing nations to take appropriate action to deal with this impending health care problem. The aim of the present study was to investigate the molecular aetiology of a group of South African PD patients. A total of 262 patients from various ethnic backgrounds were recruited for the study, and 35% had a positive family history of PD with the average age at onset (AAO) being 54.3 years of age (SD = 12.5 years). Mutation screening of the known PD genes (Parkin, PINK1, LRRK2, SNCA and DJ-1) was performed using high resolution melt and Sanger sequencing. Genotyping was done using fluorescently-labelled PCR primers followed by electrophoresis on an ABI 3130xl genetic analyser (for CTG repeats in JPH3) and with a KASP™ Genotyping Assay (for a 16bp indel in DJ-1). In order to identify a novel PD-causing gene, whole exome sequencing (WES) was conducted on three Afrikaner probands with an Illumina Genome Hiseq 2000TM and the sequences were aligned using the NCBI Human Reference Genome 37.2. The BORG (Bio-Ontological Relationship Graph) semantic database, which models the relationship of human and model organism genes to functions, pathways and phenotypes, was used to filter and prioritise genetic variants shared between the three PD exomes. It was determined that the known PD genes do not play a significant role in disease pathogenesis in the South African patients as only 15/262 (5.7%) of the patients harboured mutations: seven in Parkin, one in PINK1, six in LRRK2 and one in SNCA. Only one of the patients harboured a 16bp indel variant at the transcription start site of DJ-1. None of the Black PD patients had pathogenic repeat expansions in JPH3 thereby excluding Huntington disease-like 2 as a cause of the disease phenotype. Genealogical analysis revealed that six of the apparently unrelated Afrikaner PD probands were related to a founder couple that immigrated to South Africa in the 1600s which suggests that there is a possible founder effect for the disease. Bioinformatics analysis of WES data on three of the probands identified 21 variants in 12 genes that were present in all three PD exomes and fulfilled various criteria. Sanger sequencing was used for verification of five variants and of these, two (in CDC27 and NEDD4) were found to be artefacts. The remaining three (in HECDT1, TBCC and RNF40) were excluded based on the lack of cosegregation with disease and the high frequency of the allele in controls. Further work is necessary to verify the presence of the remaining sixteen variants and to characterise each of them for their possible pathogenicity. The discovery of novel PD-causing genes is important as this may shed light on the pathways or processes that are involved. A current hypothesis implicates the lysosome-dependent pathway as a unifying biochemical pathway that can account for the phenotypic spectrum within PD. Notably, although Mendelian forms are thought to account for only about 10- 15% of cases, the study of Mendelian inherited variants is likely to provide insight into the pathophysiology of the more common sporadic form of this condition. Dissecting the key molecular mechanisms underlying PD will provide critical information for improved treatment strategies and drug interventions that will ultimately prevent or halt neuronal cell loss in susceptible individuals. / AFRIKAANSE OPSOMMING: Parkinson se siekte (PS) is 'n erge neurodegeneratiewe bewegings-siekte, wat motorstroombaan disregulasie veroorsaak. Dit lei uiteindelik tot beperkte bewegings vermoëns. Hierdie toestand word veroorsaak weens die selektiewe agteruitgang van die dopaminergeniese neurone in die substantia nigra pars compacta in die midbrein, wat later lei tot die patologiese simptome naamlik: bradykinesia, rustende spiersametrekkings, posturale onstabiliteit en rigiditeit. Daar is aanvanklik vermoed dat individue wat PS ontwikkel, aan 'n omgewingsfaktor(e) blootgestel is wat die aanvang van die siekte veroorsaak het, terwyl meer onlangs is daar 'n aansienlike genetiese komponent tesame met omgewingsfaktore geïdentifiseer, wat betrokke is by die patogenese van die siekte. Tans is daar agt gene (Parkin, PINK1, LRRK2, SNCA, DJ-1, ATP13A2, EIF4G1 en VPS35) wat direk by PS geïmpliseer is. Wêreldwyd is daar ‗n toenemende voorkoms van neurodegeneratiewe siektes aangesien bevolkings langer leef. In Europa, Kanada en die VSA, is daar geprojekteer dat die voorkoms van PS tussen 2010 en 2050 met 'n faktor van twee verhoog kan word. Dit is ongeveer 'n 92%- verhoging. In Tanzanië (die enigste studie wat tot dusver in sub-Sahara Afrika gedoen is) word daar selfs ‗n groter toename, van 184% tussen 2005 en 2025 voorspel. Dit is te danke aan die feit dat die bevolkings- veroudering in ontwikkelende lande die van ontwikkelde lande sal oorskry. Ondersoeke na die oorsake en risiko-faktore onderliggend aan neurodegeneratiewe siektes, byvoorbeeld PS, word dus dringend benodig deur beleidmakers en regerings in ontwikkelende lande, sodat hulle die nodige stappe kan neem om hierdie dreigende gesondheidsorg-probleem op te los. Die doel van die huidige studie was om ondersoek in te stel na die molekulêre etiologie van 'n groep Suid-Afrikaanse PS pasiënte. 'n Totaal van 262 pasiënte van verskillende etniese agtergronde, is gewerf vir die studie. Hiervan het 35% 'n positiewe familiegeskiedenis van PS en die gemiddelde aanvangs ouderdom (AAO) was 54,3 jaar (SD = 12,5 jaar). Mutasie-analise van die bekende PS gene is uitgevoer met behulp van hoë resolusie smelt en Sanger volgordebepaling. Genotipering is gedoen met behulp van fluoresserend geëtiketteerde PKR inleiers met elektroforese, op 'n ABI 3130xl genetiese analiseerder (CTG herhalings in JPH3), en met 'n KASP ™ Genotipering toets (vir 'n 16bp indel in DJ-1). Ten einde, om 'n nuwe PSveroorsakende geen te identifiseer was heel eksoom volgordebepaling (WES) uitgevoer op drie Afrikaner PS positiewe pasiënte met 'n Illumina Genome Hiseq 2000™ en die volgorders is gerangskik met behulp van die NCBI Menslike Verwysings Genoom 37.2. Die BORG (Bio- Ontologiese Verhoudings Grafiek) semantiese databasis, wat gebaseer is op die verhouding van die mens en model organisme gene funksies, paaie en fenotipes, en is gebruik om genetiese variante, wat gedeel word tussen die drie PS exome te filtreer en te prioritiseer. Daar is vasgestel dat die bekende PS gene nie 'n belangrike rol in die patogenese van die siekte in die Suid-Afrikaanse pasiënte speel nie. Dit is aangesien slegs 15/262 (5.7%) van die pasiënte bekende mutasies dra: sewe in Parkin, een in PINK1, ses in LRRK2 en een in SNCA. Slegs een van die pasiënte het 'n 16bp delesie variant in die transkripsie promotor area van DJ-1 gedra. Geen van die Swart PS pasiënte het patogeniese herhalings in JPH3 vertoon nie. Gevolglik is Huntington siekte-agtige 2 uitgesluit as 'n oorsaak van die siekte fenotipe. Genealogiese analise het getoon dat ses van die skynbaar onverwante Afrikaner PS pasiënte verwant is aan 'n stigter paartjie wat in die 1600's na Suid-Afrika geïmigreer het, wat daarop dui dat daar 'n moontlike stigter effek vir die siekte is. Bioinformatiese analise van WES data vir drie van die pasiënte, het 21 variante in 12 gene geïdentifiseer, wat in al drie PS exome teenwoordig was en verskeie kriteria vervul het. Sanger volgordebepaling is gebruik vir die bevestiging van vyf variante en van hierdie, is twee (in CDC27 en NEDD4) bevind om artefakte te wees. Die oorblywende drie (in HECDT1, TBCC en RNF40) is uitgesluit gebaseer op die gebrek aan gesamentlike-segregasie met die siekte en die hoë frekwensie van die allele in die kontrole groep. Verdere werk is nodig om die teenwoordigheid van die oorblywende variante te verifieer en om elkeen van hulle te karakteriseer vir hulle moontlike patogenisiteit. Die ontdekking van die nuwe PS-veroorsakende gene is belangrik aangesien dit lig kan werp op die stelsels of prosesse wat betrokke is. 'n Huidige hipotese impliseer die lisosoom-afhanklike pad as 'n verenigende biochemiese padweg, wat verantwoordelik is vir die fenotipiese spektrum binne PS. Alhoewel Mendeliese vorms vermoedelik verantwoordelik is vir slegs omgeveer 10-15% van die gevalle, is die studie van Mendelse gene geneig om insig te verkry in die patofisiologie van die meer algemene sporadiese vorm van hierdie toestand. Ontleding van die kern molekulêre meganismes onderliggend aan PS sal kritiese inligting vir beter strategieë vir behandeling en geneesmiddel-intervensies voorsien, wat gevolglik neuronale sel verlies in vatbare individue sal voorkom of beëindig. / Medical Research Council / National Research Foundation / Harry Crossley Foundation

The Transmissible Spongiform Encephalopathies (TSEs) or “prion” diseases are a group of fatal neurodegenerative diseases the aetiology of which is not fully understood. These diseases are characterised by a number of pathological changes in the central nervous system (CNS) including; vacuolation of the neuropil, gliosis and deposition of PrPSc; the abnormal form of the host glycoprotein PrP. Although the major pathology in these diseases is associated with the CNS the immune system is central to the pathogenesis of many natural and experimental TSEs including natural scrapie in sheep, chronic wasting disease in free ranging and captive deer and variant CJD (vCJD) in humans. Unlike many infectious diseases where deficiencies in immune function are opportunistic for the invading pathogen a competent immune system is required for efficient TSE infection via peripheral routes. As infection of the lymphoid tissues in many TSEs can occur many months before the detection of infectivity in the CNS, the determination of those cells in the lymphoid system has been the focus of much research and a number of studies now point towards the importance of the follicular dendritic cell (FDC), a long-lived radio resistant cell, in TSE pathogenesis. The involvement of FDCs in peripheral TSE pathogenesis relates to the inability of ionising radiation to influence pathogenesis, the association of PrP protein with FDCs in both uninfected and infected lymphoid tissues, and the demonstration that TSE pathogenesis is severely impaired in mice devoid of these cells. The aims of this thesis were to further understand the role of FDCs in the pathogenesis of a range of mouse-adapted experimental TSE strains and to determine if peripherally acquired TSE infections are influenced by host age or by stimulation of the immune system. Using chimaeric mouse models where a mismatch in the expression of PrP protein between FDCs and lymphoid/myeloid cells was produced, further evidence for a critical role for in the pathogenesis of the ME7 TSE strain was produced. Although these findings produced strong evidence that FDCs were important for the ME7 strain the possibility that different TSE strains may target different cell types in the peripheral lymphoid system was explored using a range of mice with specific immunological defects. Infection of these mice with several experimental TSE strains showed that the presence of mature FDCs was also important for the pathogenesis of the strains tested. Clinical cases of vCJD have been confined almost exclusively to young adults, although the reasons behind this apparent age-related susceptibility are not fully understood. The capacity of the immune system to mediate immune responses to pathogens declines with age as a result of impaired lymphocyte and FDC function. As FDCs are critically involved in the pathogenesis of many TSEs, including vCJD, it was hypothesised that an aging immune system may impair disease pathogenesis. Peripheral infection of senescent mice failed to produce clinical disease during lifespan, although evidence of disease transmission, was detected in a proportion of aged mice. These findings demonstrate that this inefficient disease transmission, as a consequence of age, may lead to considerable levels of sub-clinical disease within the population. Finally the influence of immune system stimulation, by the generation of a humoral immune response, on peripheral TSE pathogenesis was investigated. These findings demonstrated that immunisation can influence pathogenesis, but only during the early stages of infection prior to spread to the CNS. These data imply that modulation of the immune system does not alter TSE pathogenesis once disease has been initiated in the CNS. Finally, these studies have found some preliminary evidence that TSE infection may induce FDC activation suggesting that TSE infection may influence the immune response. Together, these data show that a functional immune system and specifically, the presence of mature FDCs, are central to the pathogenesis of peripherally acquired TSE infections.

A worldwide demographic shift is currently occurring, with rapidly increasing numbers of elderly individuals. Since the incidence of neurodegenerative disease generally increases with age, this entails an increase in dementia prevalence. There are several strong incentives for establishing robust and widely available imaging methods for the early diagnosis of these diseases. Atrophy patterns are evident only late in the disease process, and the distinction from healthy ageing can often be elusive. For early diagnosis, physiologic parameters such as perfusion or metabolism must be assessed. The available modalities all have restricted clinical usefulness. The main aim of this thesis was to advance the clinical usefulness of perfusion and metabolism imaging in patients with neurodegenerative dementia, with a focus on visual assessment. A cohort of patients with neurodegenerative dementia was included, along with an age-matched control group. All subjects underwent MRI, including a pseudocontinuous ASL sequence and FDG-PET. In papers II and III, a subgroup containing both patients and controls underwent a second FDG-PET with reduced dose. In paper IV, the material was combined with a similar cohort from Amsterdam. Paper I showed that spatial smoothing increased the correlation between visually assessed perfusion and metabolism levels as displayed with FDG-PET. However, the distinction between patients and healthy controls was less satisfactory due to false positives. Paper II showed that differences in regional standard uptake value ratios between normal- and low-dose FDG-PET were small and without clinically significant bias. Paper III showed that the diagnostic performance of Z-score maps showing regions of significant deficits in metabolism was highly similar in normal- and low-dose FDG-PET images.  Paper IV showed that ASL perfusion-based Z-score maps can be used for diagnostic purposes with high specificity, but inferior sensitivity, compared to FDG-PET. In conclusion, the included studies address aspects of the visual assessment of perfusion and metabolism neuroimaging, with a focus on clinical usefulness in diagnosing neurodegenerative dementia.

Neurodegeneration is a chronic, progressive and debilitating condition that affects majority of the World's elderly population who are at greater risk. Numerous scientific studies suggest that there could be a common underlying molecular mechanism that promotes the degeneration and the subsequent neuronal loss, however so far the progress in this direction is rather limited. Abnormal protein misfoldings, as well as protein plaque formations in the brain, are some of the hallmark characteristic features of neurodegenerative disorders (NDDs). Genetic and environmental factors, oxidative stress, excessive reactive oxygen species formation, mitochondrial dysfunction, energy depletion and autophagy disruption etc. are some of the widely suspected mechanisms that manifest the cognitive, motor and emotional symptoms of these NDDs. Motivated by some molecular traits found in common in several NDDs, network-based systems biology tools and techniques were used in this study to identify critical molecular players and underlying biological processes that are common for Parkinson's, Alzheimer's and Huntington's disease. Utilizing multiple microarray gene expression datasets, several biomolecular networks such as direct interaction, shortest path, and microRNA regulatory networks were constructed and analyzed for each of the disease conditions. The network-based analysis revealed 26 genes of potential interest in Parkinson's, 16 in Alzheimer's and 30 in Huntington's disease. Many new microRNA-target regulatory interactions were identified. For each disorder, several routes for possible disease initiation and protection scenarios were uncovered. A unified neurodegeneration mechanism network was constructed by utilizing the significantly differentially expressed genes found in common in Parkinson's, Alzheimer's and Huntington's microarray datasets. In this integrated network many key molecular partakers and several biological processes that were significantly affected in all three NDDs were uncovered. The integrated network also revealed complex dual-level interactions that occur between disease contributing and protecting entities. Possibilities of microRNA-target interactions were explored and many such pairs of potential interest in NDDs were suggested. Investigating the integrated network mechanism, we have identified several routes for disease initiating, as well as alleviating ones that could be utilized in common for Parkinson's, Alzheimer's and Huntington's disease. Finding such crucial and universal molecular players in addition to maintaining a delicate balance between neurodegeneration promoters and protectors is vital for restoring the homeostasis in the three NDDs.

La contamination des ressources en eau potable et des terres agricoles par les pesticides qui entrent dans la chaine alimentaire est un problème environnemental et sanitaire majeur. Des études épidémiologiques ont montré un lien entre l’exposition aux pesticides et la maladie de Parkinson, mais peu d’études sont disponibles sur les autres pathologies neurodégénératives. Notre hypothèse est que les pesticides pourraient être des facteurs déclencheurs ou aggravants, communs aux maladies neurodégénératives.Au laboratoire, nous avons identifié par criblage sur la protéine prion, PrP, un composé nommé A6 décrit pour ses propriétés herbicides. A6 est un dérivé de l’α-terthiényl, molécule naturelle extraite des œillets d’inde. Le composé A6 a la capacité de promouvoir des formes oligomériques de la protéine prion sur une lignée cellulaire infectée par des prions. Mon projet de recherche visait à étudier les effets du bio-herbicide A6 sur l’agrégation et la propagation des prions in vivo. Des souris infectées par les prions ont été traitées avec différentes doses de cette molécule (5, 10 et 20 mg/kg). A la dose de 5 mg/kg, le composé A6 diminue le temps de survie des animaux avec une augmentation de la charge amyloïde. Tandis qu’aux plus fortes doses le traitement par A6 augmente la survie des souris avec une diminution de la charge amyloïde. Par un test de centrifugation rapide (RCA), nous avons montré que les faibles concentrations d’A6 favorisent la formation d’oligomères solubles de PrPSc SDS résistants (rSDS-PrPSc), alors que les plus fortes concentrations induisent des formes insolubles. L’analyse des cerveaux montre que seules les souris traitées avec 10 et 20 mg/kg d’A6 présentent des formes dimériques de rSDS-PrPSc. Cette étude montre une dualité d’effet du composé A6 : à de faibles doses, il favorise la pathologie probablement via des formes oligomériques solubles favorisant la réplication des prions. A de plus fortes doses, le composé A6 piègerait une partie de l’infectiosité des prions sous forme d’agrégats amorphes SDS résistants, bloquant la réplication des prions, et ayant un effet « protecteur ».Une recherche d’analogues structurels au composé A6 a permis l’identification d’une classe d’antifongiques commercialisés : les anilinopyrimidines. Cette famille est composée de 3 molécules : cyprodinil, mépanipyrim et pyriméthanil, qui luttent contre des champignons responsables de la pourriture grise des fruits. L’analyse de nombreux rapports a révélé que nous sommes chroniquement exposés à des résidus d’anilinopyrimidines. Dans cette deuxième étude, nous avons étudié l’effet de ces 3 fongicides dans plusieurs modèles de la maladie d’Alzheimer (MA) et les conséquences sur les marqueurs de la pathologie. Des études d’incubation ex vivo associées à des expériences de cinétique d’agrégation de peptides Aβ1-42 ont montré que ces composés interagissent directement avec les peptides et accélèrent sa cinétique d’agrégation. Afin de déterminer leurs effets in vivo, nous avons exposé chroniquement des souris J20 à un cocktail des 3 fongicides via l’eau de boisson. Les souris ont été traitées à 0,1 μg/L (0,44 nM) de chaque composé, correspondant à la concentration maximale autorisée dans l’eau potable. Après 9 mois de traitement, l’analyse des souris J20 a montré une augmentation du nombre et de la surface des plaques amyloïdes au niveau de l’hippocampe et du cortex. Pour déterminer à quel moment se produit l’effet proagrégant du cocktail, une étude longitudinale d’apparition des agrégats à 3, 6 et 9 mois par microscopie biphotonique, a montré que les plaques amyloïdes augmentent entre 6 et 9 mois et que les pesticides exacerbent les agrégats vasculaires. Les anilinopyrimidines modifient la production et la clairance des peptides Aβ en augmentant l’expression de BACE1 et en diminuant l’expression de la néprilysine. Nos travaux montrent que les antifongiques aggravent la MA. / Contamination of the drinking water and agricultural lands by the use of pesticides entering into the food chain is a major environmental and health problem. Epidemiological studies have shown a link between pesticide exposure and Parkinson's disease, but few studies are available on other neurodegenerative disorders. Our hypothesis is that pesticides may be triggering or aggravating factors common to neurodegenerative diseases.In the laboratory, we identified by a screening on the prion protein, PrP, a compound named A6 described for its herbicidal properties. A6 is a derivative of α-terthienyl, a natural molecule extracted from marigolds. A6 compound has the ability to promote oligomeric forms of the prion protein on a prion-infected cell line. My research project aimed to study the effects of the bioherbicide A6 on prion aggregation and propagation in vivo. Mice infected with prions were treated with different doses of this molecule (5, 10 and 20 mg/kg). At the dose of 5 mg/kg, A6 compound decreases the survival time of animals with an increase of the amyloid load. While at the higher doses, A6 treatment increases survival of mice with a decreased amyloid burden. Using a rapid centrifugation assay (RCA), we have shown that low concentrations of A6 promote soluble SDS-resistant oligomers of PrPSc (rSDS-PrPSc), while higher concentrations favour insoluble forms. Brain analysis shows that only mice treated with 10 and 20 mg/kg of A6 exhibit dimeric forms of rSDS-PrPSc. This study shows a dual effect of A6 compound: at low doses, it strenghtens the pathology probably via soluble oligomeric forms favouring the replication of prions. At higher doses, A6 compound would trap part of the infectivity of prions as SDS resistant amorphous aggregates, blocking prion replication, and thus having a “protective” effectA search for structural analogs of A6 compound allowed the identification of a class of commercial antifungals: anilinopyrimidines. This family is composed of 3 molecules: cyprodinil, mepanipyrim and pyrimethanil, used to fight against fungi responsible for the gray mold of fruits. Analysis of many reports have revealed that we are chronically exposed to residues of anilinopyrimidines. In this second study, we evaluated the impact of the 3 fungicides in several models of Alzheimer’s disease (AD) and their consequences on pathological markers. Ex vivo incubation studies associated to kinetics of fibril formation of Aβ1-42 peptides have shown that these compounds interact directly with Aβ peptides and accelerate its kinetics of aggregation. To determine their effects in vivo, we chronically exposed J20 mice to a cocktail of the 3 fungicides through drinking water. Mice were treated with 0.1 μg/L (0.44 nM) of each compound, corresponding to the maximal concentration allowed in the tap water. After 9 months of treatment, analysis of J20 mice showed an increase in the number and surface of plaques in the hippocampus and cortex. To determine the moment when the pro-aggregative effect occurs, a longitudinal study of appearance of aggregates at 3, 6 and 9 months by 2-photon microscopy was done. Our results showed that amyloid plaques increase between 6 and 9 months, and exacerbate vascular amyloid aggregates. Anilinopyrimidines modified the production and clearance of Aβ peptides by increasing BACE1 expression and by decreasing neprilysin expression. Our researches show a role of fungicides in the aggravation of AD.