Maladie des motoneurones

Les maladies des motoneurones (MND) sont un groupe de troubles neurodégénératifs qui affectent sélectivement les motoneurones, les cellules qui contrôlent les muscles volontaires du corps. Selon la CIM-11, les troubles suivants sont comptés parmi les maladies des motoneurones: la sclérose latérale amyotrophique (SLA), la paralysie bulbaire progressive (PBP), la paralysie pseudobulbaire, l'atrophie musculaire progressive (PMA), la sclérose latérale primaire (PLS) et l' amyotrophie monomélique (MMA), ainsi que certaines variantes plus rares ressemblant à la SLA. Les maladies des motoneurones affectent à la fois les enfants et les adultes. Bien que chaque maladie du motoneurone affecte les patients différemment, elles provoquent toutes des symptômes liés aux mouvements, principalement une faiblesse musculaire. La plupart de ces maladies semblent se produire au hasard sans causes connues, mais certaines formes sont héréditaires. Des études sur ces formes hérédita

DJ-1 as a neuroprotective protein in models of Parkinson's disease

Katarzyna Piorkowska-Stanco

Parkinson's disease (PD) is a common progressive neurodegenerative disorder characterized clinically by the combination of motor symptoms like bradykinesia, tremor, rigidity and postural instability. The pathology of PD is related to the degeneration of dopaminergic neurons of the substantia nigra pars compacta (SNpc) leading to the deficiency of dopamine in the striatal projection areas of these neurons. The pathogenesis of PD is not fully elucidated yet, however there is strong evidence that protein aggregation, mitochondrial dysfunction and oxidative stress play a primary role in the etiology of the disease. Most of PD cases are sporadic, however, several genes have been characterized to cause familial forms of the disease. Among them, mutations in DJ-1 were identified in families with autosomal-recessive early-onset PD and account for 2% of inherited PD cases. The DJ-1 protein was identified as an important player in cellular defense against oxidative stress as it possibly acts as an oxidative stress-induced chaperone and inhibits the formation of inclusions of α-synuclein, another protein related to PD. Alpha-synuclein mutations cause an autosomal dominant form of the disease. Moreover, this protein is a main component of Lewy Bodies, a pathological hallmark of PD. The goal of the experiments during my thesis was to investigate the potential protective effect of DJ-1 in toxin-based [6-hydroxydopamine (6-OHDA) and 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)] as well as genetic models of PD in vivo. Towards this goal, the DJ-1 protein was over-expressed in rodent SNpc through the injections of recombinant adeno-associated viral vector (rAAV). In the first study, the DJ-1 over-expression led to significant protection of dopaminergic cells and spontaneous motor behavior in 6-OHDA-lesioned animals. However, this effect of DJ-1 was not confirmed when DJ-1 was over-expressed in the brains of mice lesioned with MPTP. In the third part of the study, the nigral over-expression of mutated a-synuclein (A30P mutation found in familial PD cases) was chosen as the genetic model of PD, already developed in our lab. Interestingly, significant preservation of spontaneous behavior was obtained when a-synuclein (A30P) was co-injected with DJ-1. However, this was accompanied by a modest protection of dopaminergic cells, suggesting the implication of other, subtle mechanisms regulating DJ-1-related basal ganglia output. Although the DJ-1 protection of dopaminergic cells was not always achieved, the effect of DJ-1 on the spontaneous behavior implies the interesting capacity of this protein. Our results suggest that DJ-1 is one of key factors playing role in maintenance of dopaminergic function. For a possible clinical application, DJ-1 may have to be linked with another neuroprotecting factor to assure a stronger protection effect.

EPFL2007

Adeno-Associated Virus-Mediated Gene Delivery for the Treatment of Amyotrophic Lateral Sclerosis and other Motor Neuron Disorders

Christopher Towne

The delivery of molecules and genes to the central nervous system (CNS) poses a major challenge for the treatment of neurodegenerative diseases. CNS disorders require long-term intervention and the presence of the blood-brain barrier (BBB) restricts the penetration of conventional drugs to the desired target cells. One approach towards stable delivery of therapeutic agents to the CNS is based on the transfer of DNA to target cells using viral vectors; a strategy known as gene therapy. Although viral vectors have provided encouraging results in CNS gene therapy trials for disorders such as Parkinson's disease, the small diffusion of the vector following direct injection into the brain region is not amenable to motor neuron (MN) disorders, such as amyotrophic lateral sclerosis (ALS) and spinal muscular atrophy, that have cells distributed across fifty centimeters of spinal cord. The aim of this thesis was to explore non-invasive approaches for gene delivery to MNs of the spinal cord using adeno-associated viruses (AAV). AAV vectors are powerful gene transfer vehicles due to their low pathogenicity and ability to express genes in neurons for long periods of time. The first part of the thesis focused on ALS, an incurable paralytic disease resulting from a global death of MNs. Using a mouse model of ALS expressing a mutant form of superoxide dismutase 1 (SOD1) that causes the disease in humans, we have delivered genetic silencing instructions that act to degrade the SOD1 messenger RNA prior to its translation into the toxic protein. AAV serotype 6 was used to deliver the SOD1-silencing cassette through noninvasive peripheral routes to target relevant cell types in disease. The vector was administered intravenously following the hypothesis that AAV could infect MNs from the vasculature through traversing the peripheral axons that connect the MNs to the muscle fibers, a process known as retrograde transport. This resulted in infection of MNs across the spinal cord and brain stem, as well as almost total infection of skeletal muscle, another cell type implicated in ALS. Direct injections into multiple muscle groups were also performed, capitalizing on the retrograde transport capability of AAVs, to result in even higher levels of MN infection. These injections demonstrated that AAV serotype 6 could successfully deliver genes to MNs across the breadth of the spinal cord and resulted in protection of individual MN pools from ALS-mediated death. Curiously, however, despite the impressive infection profiles and neuroprotection at various spinal cord levels, neither of the techniques altered the disease course of the animals. These results stress the complexity of gene delivery and suggest that critical thresholds of SOD1-silencing and transduction across various cell types are required to rescue this particular disease model. The second component of the thesis concentrated purely on gene delivery to spinal cord neurons. AAV serotype 6 was injected directly into the muscles of Green African monkeys to determine whether the vector could undergo retrograde transport in larger animals. Indeed, efficient infection of MNs occurred, suggesting that this peripheral non-invasive delivery route is applicable to primates. These findings are not only relevant for human ALS therapy, but considering the similar dimensions of the injected monkeys with human newborns, directly relevant for treatment of infantile disease, spinal muscular atrophy. The last part of the thesis examined the ability of AAV serotype 6 to deliver genes to sensory neurons of spinal cord dorsal root ganglia in a mouse model of chronic pain. This study was initiated following the fortuitous observation of sensory neuron infection in the previous ALS mouse experiments. We examined various administration routes and found that AAV serotype 6 could efficiently deliver genes to sensory neurons in the context of chronic pain, demonstrating that the vector can be used to dissect mechanisms behind this disorder in rodents, and potentially serve as a vehicle for gene therapy towards intractable pain. In conclusion, the present thesis demonstrates that AAV serotype 6 is a powerful gene transfer vehicle for the CNS. Combined with future advances in AAV technology and delivery methods, the work presented here may one day facilitate gene therapy across the spinal cord for the treatment of devastating MN diseases, such as ALS and spinal muscular atrophy, as well as sensory neuron disorders, such as chronic pain.

EPFL2010

DJ-1 as a neuroprotective protein in models of Parkinson's disease

Katarzyna Piorkowska-Stanco

EPFL2007

Adeno-Associated Virus-Mediated Gene Delivery for the Treatment of Amyotrophic Lateral Sclerosis and other Motor Neuron Disorders

Christopher Towne

EPFL2010

The role of MCT2 in motor neuron function

DJ-1 as a neuroprotective protein in models of Parkinson's disease

Adeno-Associated Virus-Mediated Gene Delivery for the Treatment of Amyotrophic Lateral Sclerosis and other Motor Neuron Disorders

The role of MCT2 in motor neuron function

DJ-1 as a neuroprotective protein in models of Parkinson's disease

Adeno-Associated Virus-Mediated Gene Delivery for the Treatment of Amyotrophic Lateral Sclerosis and other Motor Neuron Disorders