The Molecular and Cellular Basis of Parkinson’s Disease
Parkinson’s disease (PD) affects >1% of the population over the age of 65. Currently, there are over 100,000 people affected in Canada alone and the numbers will only grow as the population ages. PD involves the death of dopamine (DA) neurons in the midbrain, which leads to devastating motor and functional impairment. Moreover, it is becoming clear that PD pathology is not limited to DA neurons but is much more widespread, involving cells both inside and outside the brain. These non-DA lesions often precede DA involvement and help explain the many early non-motor symptoms in PD patients, which until recently have been largely ignored. Although treatment for PD is available, its effectiveness diminishes over the long term. Hope for a more definitive treatment lies in basic biomedical research. Over the last decades, the discovery of genes responsible for familial forms of PD have transformed what had been considered until the late 1990s as a prototypic “environmental disease” into one of the most complex multi-genetic diseases of the brain.
Our lab has had a longstanding interest in understanding the molecular and cellular functions of these PD genes. Mutations in the genes encoding α-synuclein, leucine-rich repeat kinase 2 (LRRK2) and Vps35 cause autosomal dominant forms of PD, whereas mutations in the genes encoding parkin, PINK1, and DJ-1 cause autosomal recessive forms of PD. Although these monogenic forms only account for ~5-10% of all PD cases, characterizing the molecular and cell biological mechanisms involved has become one of the most promising strategies for understanding the pathogenesis of the more common sporadic forms of PD.
Ongoing projects in the lab :
- α-Synuclein Pathology in PD – from mouse models to genetic screens
- Modeling Parkinson’s disease with iPSC
- Investigating the function of Parkin/PINK1 in mitochondria biology
α-Synuclein Pathology in PD – from mouse models to genetic screens
In an effort to understand how α-synuclein fibrils are taken up into cells and propagated, as well as the potential associated pathological effects, we produce α-synuclein pre-formed fibrils (PFF) in vitro, in collaboration with Dr. Durcan’s Early Drug Discovery Unit, the Neuro-EDDU.
Striatal injection of α-synuclein PFFs induces PD-like phenotypes in M83 transgenic mice. This model is used in our lab to test specific compounds as therapeutic strategies for PD.
We also have developed robust cell-based α-synuclein uptake assays, both in immortalized cell lines and human induced pluripotent stem cell (iPSC) derived cells. Such assays are amenable to High-Throughput Screening, and, through a screen based on genome-wide CRISPR, we already identified several candidate genes that could be involved in α-synuclein cellular uptake.
Finally, in close collaboration with the Neuro-EDDU, we are also producing iPSC derived midbrain organoids, in order to study α-synuclein propagation in a cerebral 3D environment.
Modeling Parkinson’s disease with iPSC
In collaboration with Dr. Durcan’s Early Drug Discovery Unit, the Neuro-EDDU, our team is developing models of PD using human iPSCs. We have access to numerous lines derived from healthy individuals as well as PD patients bearing different genetic mutations associated with the disease. We are also putting a lot of effort into genetically engineering iPSCs lines in order to generate isogenic pairs for our studies.
We are able to grow and differentiate iPSCs into dopaminergic, cortical or motor neurons as well as astrocytes and microglial cells, to investigate PD pathogenesis in 2D cultures. We also work towards co-culturing different iPSC derived cell types in 2D. Finally, we are producing iPSC derived organoids with these various cell types, which allows us to study PD pathological pathways and mechanisms in 3D environments.
Investigating the function of Parkin/PINK1 in mitochondria biology
The study of Parkin/PINK1 function in mitochondrial biology, and the role of mitochondrial dysfunction in PD pathology, is one of our long-standing interest in the lab. Throughout the years, we developed an expertise in monitoring mitochondrial dysfunction in vitro, we helped unravel new mitochondrial quality control mechanisms such as mitochondrial derived vesicles (MDVs), and we contributed to a better understanding of Parkin structure and function. Our main ongoing project now focuses on PINK1 biology at the surface of mitochondria.