Funded Studies
Objective/Rationale:
Recent reports have demonstrated that skin cells from patients with Parkinson’s disease can be reprogrammed into pluripotent stem cells (iPS) and subsequently differentiated into dopaminergic neurons. The main goal of this project is to generate iPS-derived neurons from patients with genetic PD. We will examine whether the presence of endogenous human mutations results in specific and disease relevant phenotypes in iPS neurons. We will collaborate with the NINDS PD iPS Cell Research Consortium to optimize the generation and characterization of these iPS neurons.
Project Description:
The overall goal of this project is to establish iPS-derived neurons from patients with PINK1- and Parkin-linked familial forms of PD. We will use the latest technological advances, in collaboration with the PD iPS Consortium, to ensure consistent and reliable neuronal differentiation of the iPS lines, followed by the phenotypic characterization of the differentiated neurons. Recent data suggest that Parkin gets translocated to damaged mitochondria in a PINK1 dependent manner, indicating that PINK1 functions upstream from Parkin in a common pathway. Neuronal toxicity will be examined in Parkin and PINK1 iPS-derived neurons under basal conditions and following treatment with mitochondrial stressors. We will examine mitochondria function in PINK1 and Parkin iPS neurons and employ therapeutic strategies to rescue any abnormalities in phenotypes.
Relevance to Diagnosis/Treatment of Parkinson’s Disease:
There is an imperative to examine appropriate human derived cell models to validate findings in other systems and to investigate novel disease mechanisms. This project will establish whether human PINK1- and Parkin-derived iPS neurons develop discernable phenotypes that are amenable to therapeutic rescue. The study will demonstrate whether it is possible to employ patient-derived, disease-specific cell models as tools to investigate and validate pathogenic mechanisms of PD, and suggests that this powerful approach will be very useful for future studies of PD
Anticipated Outcome:
Based on our preliminary data, it is anticipated that abnormal mitochondrial phenotypes will be detected in PINK1 and Parkin iPS neurons. Since iPS technology and the protocols of neuronal differentiation require continuous improvements, we will closely collaborate with the iPS PD Consortium to further improve dopaminergic differentiation and to ensure comprehensive characterization of these iPS neurons. These patient-derived genetic cell models containing endogenous levels of known pathogenic mutations are expected to increase the biological relevance of PD studies.
Progress Report
Parkin and PINK1 mutations associate with autosomal recessive early-onset Parkinson’s disease. As murine genetic deletion of parkin (an E3-ubiquitin ligase) or PINK1 (mitochondrial kinase) does not faithfully replicate the human syndrome, it is proposed that parkin and PINK1 mutations increase biological susceptibility to, rather than directly causing, substantia nigra neurodegeneration. The characterization of endogenous Parkin and PINK1 function is therefore instrumental in delineating the pathophysiology underpinning early-onset PD. As shown in our preliminary data, we have successfully used this technology to generate DA neuronal cultures from reprogrammed fibroblasts from Parkin- and PINK1-linked PD patients. We were able to identify a phenotype in our mutant PINK1 and Parkin DA neurons, characterized by mitochondrial dysfunction. Importantly, expression of normal PINK1 rescued the loss of function of mutant PINK1, further validating the relevance of PINK1/Parkin pathway in human neurons and demonstrating that it is possible to employ patient-derived, disease-specific cell models as tools to investigate and validate pathogenic mechanisms of PD. Our overall hypothesis in this application is that impairment of mitochondrial function in vulnerable neurons plays a key role in the pathogenesis of PD and that restoration of mitochondrial function will result in neuroprotection. We believe that studies of endogenous PINK1 and Parkin in human neurons offer a unique opportunity to test this hypothesis.