The key molecular mechanism of the currently incurable human prion diseases, a group of transmissible neurodegenerative disorders, involves prion formation due to a conformational transition from the cellular prion protein (PrPC) into its pathological form (PrPSc) in the central nervous system. Present cell and animal models do not seem to work for human prion diseases well since potential anti-prion compounds identified using these models failed in clinical trials. Clearly, the lack of appropriate models that are able to faithfully mimic in vivo human PrPC to PrPSc conversion and prion-associated neurotoxicity not only significantly limits our understanding of the molecular mechanism of the conversion but also confines developing of therapeutic drugs. The challenges may be overcome by obtaining various live human neurons using the newly-developed approach by reprogramming patient-derived fibroblasts into induced pluripotent stem cells (iPSCs) (Takahashi et al., 2007). Using skin-derived iPSCs from asymptomatic subjects carrying PrP mutation such as E200K, D178N, F198S, or a new mutation E200G, linked to genetic prion disease recently generated in our laboratory, we propose to further differentiate the patient-specific iPSCs into neurons to test our hypothesis that patient- specific iPSC-derived neurons can be used as models for monitoring disease phenotypes and developing therapeutic strategies for prion diseases. In this application, we propose to differentiate patient- specific iPSCs into neurons and to characterize the molecular identity of differentiated cells. Then, the patient- specific iPSC-derived neurons generated in this study will be used to characterize disease-associated phenotypes and to investigate cellular and molecular mechanisms of neurodegeneration induced by human prions and protective roles of recombinant human PrP and GSK2606414, a new specific inhibitor of a pathway of unfolded protein response. We believe that successful implementation of our study will not only generate patient-specific iPSC-derived neurons but also provide insights into the pathogenesis and treatment of prion diseases. Moreover, our study may be significant in improving our understanding of other neurodegenerative disorders such as Alzheimer's and Parkinson's disease that may involve a prion-like pathogenic mechanism as well.
Currently there are no cell models available that are susceptible to human prions, pathogens causing a group of incurable and transmissible prion diseases. To overcome this challenge, our proposal is to generate live human neurons using the newly-developed induced pluripotent stem cells (iPSCs) approach. We believe that our study will not only provide insights into the pathogenesis but also will facilitate identification of potential therapeutic drugs for prion diseases.
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