Project Details

Using iPSC-derived neurons in unbiased small molecule screens to cure hereditary spastic paraplegia

Darius Ebrahimi-Fakhari, MD, PhD

Summary

The proposed study is a translational cell biological study that aims at generating unique human disease models for SPG47, a protoypical yet poorly understood form of the hereditary spastic paraplegias. SPG47 is a devastating neurodegenerative disease in children caused by recessively inherited mutations in the AP4B1 gene, which encodes a subunit of the AP4 protein complex, a central regulator of protein trafficking. Our preliminary data show that SPG47 patient-derived cells exhibit mistrafficking of AP4 cargo proteins, a cellular phenotype that is suitable for assay development to support a high-throughput screen for therapeutic targets. We propose to: (1) Develop a high content screen for well-annotated bioactive small molecular collections and FDA-approved molecules using patient induced pluripotent stem cell-derived cortical neurons. (2) Retest active small molecule hits with mechanistically similar bioactive molecules and orthologous target validation approaches. For this project we have partnered with the CureSPG47 Foundation (www.CureSPG47.org) and have established a registry for patients with AP4 mutations. BACKGROUND: The hereditary spastic paraplegias are a group of more than 70 neurodegenerative diseases in children that collectively present the most common cause of inherited weakness, spasticity and disability. In this proposal, we focus on a prototypical yet poorly understood form of HSP, called SPG47, caused by mutations in the AP4B1 (Adaptor Related Protein Complex 4 Beta 1 Subunit) gene. Our preliminary data show that SPG47 patient-derived cells exhibit mistrafficking of AP4 cargo proteins, a cellular phenotype that is suitable for assay development to support a high-throughput screen for therapeutic targets using the ThermoFisher ArrayScan XTI High Content Screening Platform. GAP: The treatment for hereditary spastic paraplegia is very limited and available therapies ameliorate some of the symptoms (for example anti-epileptic drugs to ameliorate seizures) but are grossly inefficient in slowing the disease progression, leaving affected children to succumb to this devastating disease usually before they reach adulthood. HYPOTHESIS: Our central hypothesis is that human excitatory cortical neurons differentiated from skin cells of children with hereditary spastic paraplegia type 47 (SPG47) display cellular phenotypes that present surrogates of essential disease mechanisms in hereditary spastic paraplegia and can be employed to perform an unbiased high-throughput screen of FDA-approved compound libraries. METHODS: This study is a translational cell biological study that aims at using unique human disease models for hereditary spastic paraplegia type 47 to find targeted approaches to treating hereditary spastic paraplegias. We have partnered with the CureSPG47 Foundation (www.CureSPG47.org) to generate eight induced-pluripotent stem cell lines from four clinically well-characterized families with SPG47 and have differentiated excitatory cortical neurons. RESULTS: Pending. IMPACT: Identification of an FDA-approved compound with suitable pharmacodynamic and safety profiles would translate into clinical use in SPG47 quickly, i.e. through application for an orphan-drug designation at the FDA. Website Link: https://www.researchgate.net/profile/Darius_Ebrahimi-Fakhari http://curespg47.org

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