Thesis (Ph. D.)--University of California, San Diego, 1997. / Vita. Includes bibliographical references (leaves 174-188).

Thesis (Ph. D.)--University of California, San Diego and San Diego State University, 2007. / Title from first page of PDF file (viewed June 11, 2007). Available via ProQuest Digital Dissertations. Vita. Includes bibliographical references (p. 171-178).

<p>Huntington’s disease (HD) is an adult-onset, neurodegenerative disease caused by an autosomal dominant mutation in the huntingtin (HTT) gene. HD patients suffer from motor, cognitive, and psychiatric symptoms. The pathogenic mutation of HD is expansion of a CAG repeat in the first exon of the HTT that encodes for a polyglutamine (poly-Q) repeat in the huntingtin protein (Htt). HD results in neurodegeneration of the striatum and cortex, which is thought to underlie the development of HD symptoms, but recent evidence has shown that there are alterations to the connectivity of patients’ brains preceding degeneration. This study focuses on how wild type Htt contributes to establishing and maintaining synaptic connectivity and how a loss of normal Htt function may contribute to the synaptic alterations in HD.</p><p>In this study, I examined the role of wild type Htt in synapse formation and maturation synapses in the basal ganglia circuit, and I examined how loss of wild type Htt function may affect the pathogenesis of HD. To do so, I created conditional deletions of Htt in the mouse brain by crossing a floxed allele of Huntingtin to transgenic Cre lines. I conditionally deleted Htt from the cortex and the indirect pathway spiny neurons (iSPNs) of the striatum using Emx1-Cre and Adora2A-Cre, respectively. I also used a knock-in mouse model of HD, the zQ175 mouse, to examine alterations caused by the HD mutation. I used imaging and electrophysiological techniques to determine how loss of Huntingtin affected synapse number, function, and morphology in the cortex, striatum, and basal ganglia. </p><p>In the cortex and striatum, loss of Htt leads to disruptions in synaptic connectivity followed by neuronal stress and death. Htt is critical for moderating the formation of excitatory synapse formation in both the cortex and striatum, and that in the cortex this function is lost in HD. In the striatum, Htt is required for stabilizing striatopallidal synapses, and for proper basal ganglia function. </p><p>In order to explore the molecular mechanisms behind Htt’s control of excitatory synapse formation, I investigated its interaction with α2δ-1. α2δ-1 is a genetic modifier of mutant Htt toxicity that our lab had previously identified as the neuronal receptor of the synaptogenic Thrombospondin family (TSP) of proteins. I used in vitro neuronal cultures and biochemical analysis to determine how Htt interacts with α2δ-1 and how Htt affects TSP/α2δ-1 excitatory synapse formation. I characterized α2δ-1’s biochemical interaction with Htt and discovered that Htt postsynaptically suppresses excitatory synapses.</p><p>Taken together, these results suggest that wild type Htt functions to moderate excitatory activity in the brain. It slows the formation of excitatory connections and stabilized inhibitory ones, which may protect the brain from excitotoxic damage. These results show that Htt plays an important role in maintaining neuronal health and the establishment of synaptic connectivity in cortical and striatal circuits.</p> / Dissertation

MicroRNAs (miRNAs) represent a major system of post-transcriptional regulation, by either preventing translational initiation or by targeting messenger RNA transcripts for storage or degradation. miRNA deregulation has been reported in neurodegenerative disorders, such as Huntington’s disease (HD) and Parkinson’s disease (PD), which may impact gene expression and modify disease progression and/or severity. To assess the relationship of miRNA levels to HD, small RNA sequence analysis was performed for 26 HD and 36 non-disease control samples derived from human prefrontal cortex. 75 miRNAs were differentially expressed in HD brain as compared to controls at genome-wide significance (FDR q<0.05). Among HD brains, nine miRNAs were significantly associated with the extent of neuropathological involvement in the striatum and three of these significantly related to a continuous measure of striatal involvement, after statistical adjustment for the contribution of HD gene length. Five miRNAs were identified as having a significant, inverse relationship to age of motor onset, in particular, miR-10b-5p, the mostly strongly over-expressed miRNA in HD cases. Although prefrontal cortex was the source of tissue profiled in these studies, the relationship of miR-10b-5p levels to striatal involvement in the disease was independent of cortical involvement. In blood plasma from 26 HD, 4 asymptomatic HD gene carriers and 8 controls, miR-10b-5p levels were significantly elevated in HD as compared to non-diseased and preclinical HD subjects, demonstrating that miRNA alterations associated with diseased brain may be detected peripherally. Using small RNA sequence analysis for 29 PD brains, 125 miRNAs were identified as differentially expressed at genome-wide significance (FDR q<0.05) in PD versus controls. A set of 29 miRNAs accurately classified PD from non-diseased brain (93.9% specificity, 96.6% sensitivity, 4.8% absolute error). In contrast to HD, among PD cases, miR-10b-5p was significantly decreased and had a significant, positive association to onset age independent of age at death. These studies provide a detailed miRNA profile for HD and PD brain, identify miRNAs associated with disease pathology and suggest miRNA changes observed in brain can be detected in blood. Together, these findings support the potential of miRNA biomarkers for the diagnosis and assessment of progression for neurodegenerative diseases.

Le sujet de cette thèse est la poursuite de la caractérisation et du développement à fins thérapeutiques du peptide P42 dans la maladie d’Huntington (MH). Ce peptide a été précédemment identifié dans l’équipe dirigée par Florence Maschat et est capable de réduire la présence d’agrégats dans différents modèles cellulaires, mais aussi de Drosophile et murins de maladie d’Huntington. P42 est aussi capable de prévenir la dégénérescence neuronale et les altérations du transport axonal dans des tests effectués chez la drosophile (Arribat et al. 2013). Enfin les anomalies motrices, la perte de poids, et l’atrophie cérébrale sont restituées in vivo dans des souris R6/2 traitées par P42. Dans ce cas, P42 a été conjugué au peptide de transduction TAT, dérivé de VIH, et a été inséré dans des microémulsions, permettant des administrations répétées du peptide par voie intra-muqueuse, protégeant le peptide jusqu’à son arrivée au cerveau et facilitant sa diffusion au travers des membranes et la barrière hémato-encéphalique (Arribat et al., 2014). L’efficacité de ce peptide a ainsi été montrée après administration dans une phase pré-symptomatique ; toutefois, des résultats non publiés suggèrent également une efficacité partielle au niveau post-symptomatique. Ainsi ce peptide agirait à travers l’inhibition de l’agrégation en interagissant avec la protéine Htt dans sa partie N-terminale, et notamment au niveau de la partie N17. Des résultats préliminaires suggèrent également que, en tant que partie physiologiquement présente dans la protéine Htt, P42 pourrait avoir un rôle bénéfique et physiologique, notamment au niveau du transport axonal, sur le niveau d’expression du Brain nerve factor (BDNF) et sur l’activité neuronale. Mon travail de thèse se compose d’une part d’un travail de laboratoire, et d’autre part d’un travail de documentation. Le travail de laboratoire a été conduit sur le modèle Drosophile. Dans une première partie j’ai essayé de mieux caractériser l’efficacité de P42TAT par rapport à P42 dans l’inhibition des agrégats dans les glandes salivaires et dans la protection de la dégénérescence de l’œil. Notamment, j’ai testé l’efficacité de l’administration orale de P42TAT sur la réduction des agrégats dans les glandes salivaires. Dans une deuxième partie j’ai contribué à évaluer l’efficacité d’un fragment plus court de P42, P42B ; ce fragment de 14 aa initialement identifié par des études de dégradation de P42TAT dans des extraits de cerveau par la technique MALDI est retrouvé après 3 h et pourrait donc être une partie active, suffisante pour l’efficacité du peptide. Dans une troisième partie j’ai contribué à des études visant à étudier le rôle physiologique de P42 dans le transport axonal. Le travail de documentation a été finalisé par la soumission d’un dossier à l’agence européenne pour la médecine (EMEA), qui a permis d’obtenir la reconnaissance de P42 en tant que médicament orphelin pour la MH. Ce résultat est particulièrement important et pourrait être un premier pas vers le développement clinique de ce peptide. En effet aucun traitement curatif n’existe à ce jour pour la MH et la possibilité de réaliser des tests pré-symptomatiques permet de disposer d’une fenêtre unique pour une intervention thérapeutique précoce. De plus, au cours de ces dernières années, des études cliniques de suivi de sujets pré-symptomatiques et symptomatiques ont été menées, (études PREDICT-HD et TRACK-HD), qui ont conduit à l’identification de bio-marqueurs, notamment d’imagerie, capables de suivre l’évolution de la maladie, dès un stade pré-symptomatique, utilisables pour évaluer de façon objective l’efficacité d’un traitement, si disponible. Enfin, l’ensemble de ce travail m’a permis d’acquérir une expertise et de mener une réflexion au sein du laboratoire sur l’utilisation des peptides à des fins thérapeutiques dans la maladie d’Huntington, avec la production d’un papier de revue sur le sujet, soumis dans une revue internationale. / The subject of this thesis is the further characterization and development in therapeutic purpose of P42 peptide in Huntington's disease. This peptide was previously identified in the team led by Florence Maschat and it showed be able to reduce the presence of aggregates in different cell models, but also Drosophila and murine (mouse R6 / 2) of Huntington's disease. P42 is also able to prevent neuronal degeneration and alteration of axonal transport in the tests performed in Drosophila (Arribat et al. 2013). Finally the motor abnormalities, weight loss and brain atrophy are ameliorated in vivo in R6 / 2 mice treated with P42. In the latter case, P42 was conjugated to TAT transducing peptide, derived from HIV, and was inserted into microemulsions, with the purpose of enabling repeated administrations of the peptide by intra-mucosal route, protect the peptide until his arrival to the brain and facilitate its diffusion through the membranes and the blood-brain barrier (Arribat et al. 2014). The efficacy of this peptide has been shown following administration in a pre-symptomatic stage; however, unpublished results also suggest a partial efficacy in post-symptomatic level. Thus this peptide would be through the inhibition of aggregation by interacting with Htt in its N-terminal part, and in particular at the N17 part. Preliminary results also suggest that, as part physiologically present in the Htt protein, P42 and could have a beneficial physiological role, particularly in terms of axonal transport, level of expression of Brain nerve factor (BDNF), and neuronal activity.My thesis consists of a hand on a laboratory work, and secondly on a work documentation. The laboratory work was conducted using the Drosophila model. In the first part I tried to better characterize the effectiveness of P42TAT and compare it to that of P42 in inhibiting aggregates in the salivary glands and in the protection of the degeneration of the eye. In particular, I tested the efficacy of oral administration of the peptide P42TAT on reducing aggregates in the salivary glands. In the second part I helped evaluate the effectiveness of a shorter fragment of P42, P42B; this peptide was first identified through studies on the degradation of P42TAT in extracts of brain by MALDI; this fragment of 14 aa was found after 3 h and therefore could be an active portion, sufficient for the effectiveness of the peptide. In the third part I contributed to studies to study the physiological role of P42 in axonal transport.The documentation work was finalized at the submission of a dossier to the European Agency for medicine (EMEA), in order to obtain for P42 the label of orphan drug for Huntington's disease. This result is particularly important and could be a first step in the clinical development of this peptide. Indeed no curative treatment exists to date for Huntington's disease and the ability to perform pre-symptomatic tests can provide a single window for early therapeutic intervention. Moreover, in recent years, clinical studies monitoring symptomatic and pre-symptomatic patients were conducted (PREDICT-HD studies and TRACK-HD), which led to the identification of biomarkers, in particular of imaging, able to follow the evolution of the disease, already at a pre-symptomatic stage, be used to objectively evaluate the effectiveness of treatment if available. Finally, all of this work has allowed me to gain expertise and to reflect on the use of peptides for therapeutic purposes in Huntington's disease, with the production of paper review on the subject submitted to an international journal.

Les neuroleptiques ou antipsychotiques sont indiqués dans le traitement des troubles psychotiques et selon les molécules, troubles du comportement et traitement de courte durée de l'anxiété. Depuis l'introduction des neuroleptiques de seconde génération, la prescription s'est étendue à plusieurs utilisations, avec ou sans autorisation de mise sur le marché (AMM). Les travaux de thèse ont pour objectif de décrire le profil des patients et les conditions réelles d'utilisation des neuroleptiques en France, permettant ainsi de vérifier le respect des indications de l'AMM et des recommandations. Nous avons également comparé les effets des neuroleptiques sur la cognition dans une pathologie fréquente (la schizophrénie) à partir d'une méta-analyse en réseau et comparé l'efficacité en conditions réelles des traitements neuroleptiques et apparentés dans une maladie rare avec des symptômes différents (la maladie de Huntington).Nos résultats montrent qu'en population générale, 2,23% de la population avait reçu au moins un neuroleptique. Les médicaments les plus couramment remboursés étaient la cyamemazine, la risperidone, l'olanzapine et l'halopéridol. Une utilisation était inappropriée entre 10 et 31% des patients selon les molécules. Les patients traités par neuroleptiques soit dans le cadre de la schizophrénie soit dans le cadre de la maladie de Huntington, présentaient une évolution différente des scores cognitifs selon le neuroleptique utilisé. Ainsi, c'était une benzamide qui se retrouvait être la classe avec l'effet le plus défavorable sur la cognition. / Antipsychotics are indicated for the treatment of psychotic disorders and according to the drugs, behavioral disorders and short-term treatment of anxiety. Since the introduction of second-generation antipsychotics, prescriptions have extended to several uses, with or without marketing authorization. The thesis aims to describe the profile of patients and the actual conditions of use of antipsychotics in France, and to verify compliance with the indications of the marketing authorization and recommendations. We also compared the effects of antipsychotics on cognition in a common disorder (schizophrenia) with a network meta-analysis and compared the efficacy of antipsychotics and related treatments in real conditions, in a rare disease with different symptoms (Huntington's disease).Our results showed that in general population, 2.23% of the population had received at least one antipsychotic. The most common drugs reimbursed were cyamemazine, risperidone, olanzapine and haloperidol. Inappropriate use was between 10 and 31% of patients depending on the drug. Patients treated with antipsychotics as part of schizophrenia or in the context of Huntington's disease, showed a different pattern on cognitive scores depending on antipsychotic use. Thus, it was found that benzamide was the class with the most adverse effect on cognition.

No description available.

La maladie de Huntington (MH) est une maladie neurodégénérative, autosomique, dominante. La MH se manifeste par des troubles moteurs, cognitifs, psychiatriques et/ou comportementaux. Les troubles cognitifs sont probablement parmi les mieux documentés dans la MH, perturbant la flexibilité, l’inhibition, la planification et la prise de décision. Des désordres des aptitudes en cognition sociale ont aussi été rapportés chez ces patients, dont en particulier des troubles de la reconnaissance des expressions faciales émotionnelles et de théorie de l’esprit (ToM).Les fonctions émotionnelles et leurs régulations sont actuellement peu caractérisées, tant chez les patients que chez les modèles animaux de la MH.Chez le modèle de rats transgéniques (tgHD rats), des perturbations des réponses émotionnelles et hédoniques ont été caractérisées à un âge précoce.L’objectif de cette thèse était de mieux caractériser les déficits émotionnels et leur impact sur les fonctions exécutives en étudiant (1) différentes tâches cognitives chez des patients MH et chez des modèles animaux de la MH (rats TgHD et rats BACHD) à différents stades de la maladie ; (2) en analysant l’impact d’états émotionnels induits (peur et plaisir) sur la prise de décision chez les patients MH (symptomatiques) et chez les rats BACHD à des âges différents. / Huntington's disease (HD) is an autosomal dominant genetic neurodegenerative disease. HD is characterized by a combination of motor, cognitive, psychiatric and behavioral symptoms. Social cognition skills disorders have also been reported in these patients, including in particular recognition disorders of emotional facial expressions and theory of mind (ToM).Emotional functions and regulations are currently poorly characterized in patients and in animal models of HD. In patients, loss of emotional control, and negative or positive emotions recognition deficits have been described.In the rat model of HD (tgHD rats), disturbances of emotional and hedonic responses were characterized at early stage.The aim of this thesis was to better define the emotional deficits and their impact on executive functions (1) different cognitive tasks among HD patients and in animal models of HD (TgHD and BACHD rats) at different stages of the disease; (2) by analyzing the impact of induced emotional states (fear and pleasure) on decision making in symptomatic HD patients and in BACHD rats at different ages.

Ferroptosis is a non-apoptotic, regulated form of cell death that is characterized by the iron-dependent lethal accumulation of lipid peroxides and lipid peroxide byproducts. Huntington’s disease (HD) is an autosomal neurodegenerative disease with characteristic motor, psychiatric, and cognitive signs and symptoms caused by the expansion of CAG repeats in the Huntingtin gene, resulting in the production of pathogenic protein with an extended polyglutamine tract that is prone to aggregation. Accumulating evidence has identified links between ferroptosis and HD suggesting that ferroptosis inhibition may provide therapeutic benefit. However, the ability to evaluate this potential has been limited by the unavailability of potent, brain-penetrant specific ferroptosis inhibitors. This dissertation evaluates two different types of ferroptosis inhibitors and increases the available molecular tools to investigate the role of ferroptosis in the etiology of HD. In the second and third chapters, two new classes of ferrostatin analogs, termed fourth and fifth generation ferrostatins, are developed and their in vitro and in vivo properties characterized. These efforts identify three, fifth generation analogs that are potent, brain-penetrant, and stable and can be administered chronically to symptomatic HD mice. The fourth chapter provides molecular insights into the mechanism of action of the hypocholesterolemic drug probucol in inhibiting ferroptosis and identifies cellular cholesterol levels and cholesterol import as regulators of ferroptosis. In sum, this work provides new molecular tools and insights that can be utilized to elucidate the contribution of ferroptosis to HD and other disease states.

Metabotropic glutamate receptor 5 (mGluR5) is a key regulator of numerous brain functions including memory, cognition, and motor behavior. Dysregulation of mGluR5 signaling is evident in Huntington's disease (HD) neuropathology, an inherited, neurodegenerative disease characterized with progressive deterioration in motor, cognitive, and psychiatric functions. In this context, two cellular proteins draw particular interest for this thesis: vesicular glutamate transporter 3 (VGLUT3) and optineurin (OPTN). VGLUT3 modulates glutamate release from selected neurons that are affected by HD, while OPTN is a mGluR5-interacting protein and contributes to neuronal vulnerability in HD. However, current evidence on their involvement in mGluR5 signaling and HD pathogenesis is still lacking. Using VGLUT3 knockout (VGLUT3⁻ᐟ⁻) mice, we showed that this transporter dynamically regulated glutamate receptor densities in different brain regions. Of note, VGLUT3 deletion upregulated mGluR5 in the cerebral cortex and the striatum, unlike the hippocampus which exhibited reduced mGluR5 cell surface densities. We then crossed VGLUT3⁻ᐟ⁻ mice with the zQ175 knock-in mouse model of HD (zQ175:VGLUT3⁻ᐟ⁻) to assess the impact of VGLUT3 transmission loss on HD progression. The longitudinal behavioral assessment revealed that VGLUT3 ablation rescued the deficits in motor coordination and short-term memory in both male and female zQ175 mice throughout 15 months of age. Furthermore, VGLUT3 deletion rescued striatal cell loss likely via activation of Akt and ERK1/2 cellular pathways, with no impact on total mutant huntingtin aggregation or the associated microgliosis. To delineate the role of OPTN in mGluR5 signaling, we employed a CRISPR/Cas9 OPTN-deficient cell line and global OPTN knockout mice. We demonstrated that OPTN was essential for mGluR5-mediated canonical signaling and ERK1/2 activation in both the striatal cell line, STHdh^Q7/Q7, and acute hippocampal slices. We then showed that OPTN deletion impaired autophagic machinery via GSK3β/ZBTB16 and mTOR/ULK1 signaling pathways downstream of mGluR5. This work offers novel insights into the molecular roles of VGLUT3 transmission and OPTN in mGluR5 signaling and provides a rationale for their targeting to therapeutically mitigate pathological mGluR5 signaling in HD.