Nadia D’Ambrosi, PhD

University of Rome Tor Vergata, Department of Biology
Rome, Italy

Role of iron-dependent dysfunctions in microglia toxicity*

Summary:
It is widely recognized that the nervous system is a primary target in Friedreich’s ataxia (FRDA), with specific brain and spinal cord regions displaying significant atrophy and degeneration. Neuron loss is usually a permanent event, since nerve cells are poorly replaced by adult stem cells, leading therefore to derangement of brain areas, with dramatic consequences. In most diseases characterized by nerve cells injury, neuron fate relies not only on intrinsic pathological mechanisms, rather neuron loss is often preceded and accompanied by activation of neighboring non-neuronal cells, that contribute to establish the neuronal outcome of these diseases. Microglia, in particular, are considered the immune cells of the central nervous system, where they represent 10% of the total cell population. They constantly surveil the extracellular environment and respond to multiple stimuli, in order to kill and remove possible harmful agents. Malfunctioning neurons are a source of signals that activate adverse responses by microglia, culminating into further damage to neurons, recognized by microglia as undesirable elements that have to be removed. Nevertheless, under certain circumstances, microglia can also exert trophic and pro-survival actions that can support neuron integrity. Therefore, the possibility to switch microglia towards this beneficial side can be of advantage. The multifaceted role of microglia is well defined in neurodegenerative conditions such as Alzheimer’s and Lou Gehrig’s, as well as fronto-temporal dementia, where the replacing of harmful microglia with a beneficial type has provided many encouraging results in slowing-down the progression of the diseases. In FRDA, there is a limited knowledge about the toxic functions assumed by microglia as a consequence of frataxin-dependent iron accumulation. However, important papers published in very recent years, demonstrated that reactive microglia populate affected brain areas and that the transplantation of healthy microglia protects to a certain extent tissue damage in FRDA mice models. These data provide a robust indication that microglia can contribute to neuronal demise also in FRDA. With this project, we aim to obtain a direct demonstration that FRDA-related pathological mechanisms encompass the neurotoxic conversion of microglia. To this purpose, we will employ microglia derived from healthy and FRDA affected mice to dissect how iron accumulation, derived by frataxin loss-of-function, drives incorrect mechanisms in microglia that alter their mitochondria, their production of damaging free oxygen radicals and their release of pro-inflammatory molecules, transforming them into possible neurons’ foes. Finally, we will directly demonstrate how microglia from FRDA mice impair neuron survival and thus how these cells contribute to neuron demise in the disease. The clear identification of microglia as main players in the pathology will open new venues for a possible treatment strategy. The understanding of microglia function in the disease obtained by the expected results of this project could help in developing therapeutics, which take into account and match the specific functional states microglia, in order to drive them towards a neuron protective state. Under this aspect, it is conceivable that halting a complex and multi-systemic disease as Friedreich’s ataxia should require a multitargeted approach. With this research project, we will identify microglia toxic activation as a novel mechanism implicated in FRDA pathogenesis, indicating new potential therapeutic strategies to be exploited to counteract the disease.

*Co-funded in collaboration with FARA

Khalid El Hachimi, PhD

Institut du Cerveau et de la Moelle epiniere
Paris, France

Role of KIF1C motor protein in myelination – Involvment in ataxia

Summary:
Persistent ataxia is a neurological sign result from brain damage. This peculiar damage affects the brain centers that controls voluntary muscle movements and coordination. These movements disorders induce also difficulties in speech, eye coordination movements and swallowing. The cause of the persistent ataxia are diverse; toxic, metabolic, genetic or both. Our laboratory, located at Salpêtrière hospital (Paris) which include the largest neurological diseases care department in France, is involved in the research of genetic causes of the ataxia. The team is leaded by Alexdra Durr and Giovanni Stevanin. We have collaborated in the identification of several forms of genetically determined ataxia. We also studied the biological mechanisms underlying these peculiar forms of ataxia and developed preclinical therapeutic approach against this disease assocaited to this clinical sign. Recently, we and others have shown that autosomal-recessive mutations in the human gene coding for a motor protein belonging to Kinesin protein family KIF1C lead to neurodegenerative spastic ataxia. Soon after, we discovered that a homozygous mutation in the bovine KIF1C gene is the leading cause of progressive ataxia in Charolais cattle. The biological role of KIF1C in the CNS and specially the pathomechanistic link between KIF1C deficiency and cerebral/cerebellar dysfunction in spastic ataxia, remains however, poorly understood. Amandine Duchesne researcher at the “Institut national en recherches agronomiques et écologiques” (INRAE) and myself generated a mouse model mimicking clinical and pathological features of this peculiar ataxia (SAX2/spastic paraplegia58). We are also and currently developping a novel V5-tagged Kif1c model mice which allow us to identify the RNA and protein parteners of KIF1C. Our integrative scientific approach is based on collaboration with physicians and researchers from different disciplines. For that we have biological samples (cattle and mice) to perform all the studies. We have developed at our institute (Paris Brain institute, ICM) many tools (behavioral, radiological, histopathology, and molecular) to carry out this study. We have a performant facilities in rodent phenotyping (Phenoparc), small animals neuroradiological investigations (CENIRS), neuropathological characterization (Histomics), cell culture and cellular imaging (Quant, Celis)) and molecular analyzing. Within the institute we have also developed very good technical skills. These mice models, for which we request financial assistance from the National Ataxia Foundation, may allows us to decipher the biological aspect of the cerebellum dysfunction and to propose rational approach for preclinical therapeutic strategy, before their hopefull extention to man. We hope that our study draws your attention, worth being considering by scientific board, and we would be happy to be encouraged by the National Ataxia Foundation.

Andreia Teixeira-Castro, PhD

Life and Health Sciences Research Institute (ICVS) and ICVS/3B’s – PT Government Associate Laboratory, University of Minho
Braga, Portugal

Intermittent fasting as a novel therapeutic strategy for SCAs

Summary:
Spinocerebellar ataxias (SCAs) are diseases of the nervous system, in which certain neurons, including neurons of the cerebellum, the motor coordination center of the brain, slowly degenerate. Common symptoms of ataxias are lack of coordination, slurred speech, trouble with eating and swallowing and deterioration of fine motor skills. Extensive research has been conducted to understand how the disease occurs and address the disease causes. Spinocerebellar Ataxia type 3 (SCA3) or Machado–Joseph disease (MJD) is the most frequent ataxia worldwide, and affected individuals have a 50% chance of transmitting the affected gene to their children. In SCA3, a mutation in the ATXN3 gene generates a bigger-than-normal size of polyglutamine tract of ATXN3 protein, causing neurons to die and ultimately leading to the patients’ death. Existing treatments for SCA3 are very limited, only improving symptoms, and not stopping disease progression, making the search for new therapeutics an urgent need. The primary goal of aging research is to improve the health of the elderly and to discover ways of stopping or delaying age-related diseases. Several factors like genetics, socioeconomic status, environmental quality, and alimentary habits affect how long and how healthy people live. Although genetics and environmental quality are not under our direct control, alimentary habits, especially the amount and quality of food are. Proper nutrition can influence health and survival and often delay or prevent the start and progression of diseases. However, eating too much or too little has been associated with a high risk of chronic diseases and early death. Importantly, in our modern society, eating too much is a major risk for several diseases. A nutritionally balanced diet based on alteration of caloric intake or meal timing can lead to disease control and a healthier and longer life. There are four main diets that have been proposed to improve health: caloric restriction, in which people eat less calories per day; time restricted feeding, in which people eat only during certain hours of the day; alternate-day fasting, in which people fast during fixed periods each week; and fasting-mimicking diets, in which people eat only certain food types that mimic a fasting-like state in the body- the ketogenic diet. The classical caloric restriction was the first type of dietary regimen to be widely used for disease intervention and, only many years after, it was discovered how caloric restriction might improve disease progression: because eating less calories is often accompanied by long fasting periods, our bodies stop using sugar (glucose) as a fuel source, using ketones instead- the so-called metabolic switch that leads to many neuroprotective features. It is likely that more people may adopt these eating habits, because, compared to caloric restriction, these diets are less difficult, in the long-term. In this study, we will test different diets as a therapeutic strategy for SCA3 in rodents. Without any reduction in caloric intake, a metabolic switch will be induced by daily limiting feeding periods to certain times of the day, and by feeding the animals with a fast-mimicking ketogenic diet. We will test if these different alimentary habits stall disease progression in mice. If these diets show an impact on SCA3 animals, this could be relevant also for other ataxias.

Marka Van Blitterswijk, MD, PhD

Mayo Clinic Jacksonville
Jacksonville, FL

Long-read sequencing to decipher a repeat expansion causative of SCA36

Summary:
Spinocerebellar ataxia 36 (SCA36) is a condition characterized by problems with balance and coordination resulting from the progressive atrophy of various regions of the brain, in particular the cerebellum. The cerebellum receives information from the spinal cord and other parts of the brain, and uses this information to coordinate voluntary movements. In addition to balance and coordination problems, people with SCA36 may also experience exaggerated reflexes, difficulty with speech, tongue muscle twitches and wasting, and eventually muscle atrophy in the legs, forearms and hands. The cause of SCA36 is a longer than usual repetitive DNA sequence in a gene called NOP56. We seek to untangle how this repetitive sequence gives rise to SCA36. To this end, we will use a highly innovative technology called No-Amp sequencing. This technology enables us to perform in-depth studies focusing on the repetitive area in NOP56. We can accurately assess how long the repetitive stretch is and whether there is variability in its length across and within patients. Moreover, we will evaluate the content of the repetitive sequence itself. Although it has been reported to contain a stretch of GGCCTG-repeats, it has yet to be determined whether it is pure or interrupted by other sequences. Additionally, we will investigate whether the repeat is methylated and, if so, to what extent. Thus, our original approach – to examine the entire span of the repetitive sequence using cutting-edge technology – gives us the opportunity to reveal whether its length, purity and/or methylation profile may modify the symptoms or severity of SCA36. Furthermore, we will examine whether these characteristics of the repetitive sequence itself influence crucial disease-associated features of SCA36, such as the expression levels of NOP56 and the production of faulty RNAs or abnormal proteins. Hence, our proposed project will aid in unraveling the underpinnings of SCA36.