Amyotrophic Lateral Sclerosis, or ALS, is a rare neurodegenerative disorder the primarily targets upper and lower motor neurons – leading to the inability to control voluntary movements. Like other chronic neurodegenerative diseases, ALS starts in one focal point before spreading to the entire nervous system, including the brain and spinal cord.
As the disease spreads, motor neurons, that control specific muscle movements, begin to degenerate, causing the individual to initially experience difficulties swallowing or performing fine motor movements. Gradually all muscles under voluntary control are affected, causing the individual to lose the ability to speak, eat, move and even breath. Thus, most people with ALS die of respiratory failure, typically within three to ten years from when they first start experiencing symptoms.
There is no cure for ALS, so our focus is on trying to determine what causes the disease to spread. If we know this, then we can begin developing strategies for stopping it from spreading.
Motor neurons are supported by glial cells, accessory cells that have been shown to play an important role in the progression of ALS. One of the ways in which glia cells and neurons communicate is through nanoparticles called extracellular vesicles, or EVs. Extracellular vesicles are small pieces of cells that can be formed in various ways and that are released by the cells constitutively. EVs are loaded with proteins, RNA, and metabolites that reflect the content of the cells from which they are released. Identifying the EV content that breeds toxicity would allow us to better understand how ALS is spread.
In order to test whether glia-derived EVs propagate neuronal death, we took advantage of a mouse model that recapitulates ALS pathology. This mouse model expresses a mutant form of TDP-43, an RNA-binding protein that is the main constituent of protein inclusions present in the spinal cord and brain of sporadic and familial ALS patients. We produced glia cultures and purified EVs with a novel and efficient method, called NBI. We tested the effect of glia-derived EVs on wild type neurons and observed that ALS-derived EVs induced motor and cortical neuronal death. We searched for the EV components transmitting toxicity by using –omics techniques, associated with bioinformatics analysis. To validate our functional data, we also developed new protocols to ‘inactivate’ proteins or RNA cargoes of ALS-EVs. As a result, we have novel candidates for EV-mediated toxicity in ALS that we aim to validate in peripheral bio-fluids to accelerate ALS diagnosis. Furthermore, the outcome of this project will provide new pathways involved in disease progression that can be targeted for therapeutic intervention.
