This application is aimed at understanding the molecular basis for the neurodegenerative disease Friedreich's ataxia (FRDA) and development of novel therapeutics. FRDA is one of the triplet-repeat diseases, where expansion of GAA.TTC repeats within the FXN gene, encoding the essential mitochondrial protein frataxin, leads to epigenetic transcriptional silencing. Loss of frataxin results in a spinocerebellar ataxia with secondary cardiomyopathy, which is the major cause of death in FRDA patients. At present there is no approved therapy for FRDA. Since the GAA.TTC repeats are in an intron, and do not affect the sequence of frataxin protein, gene activation would be of therapeutic value. We identified members of the 2-aminobenzamide class of HDAC inhibitors as potent activators of FXN transcription. These molecules cross the blood brain barrier in mice and canines, exhibit no acute or chronic toxicity, and increase FXN mRNA and frataxin protein levels in the brain and heart in the mouse FRDA model, as well as in circulating lymphocytes in drug-treated FRDA patients in a Phase Ib human clinical trial. While these data provide a proof of concept for this therapeutic approach, our current compounds suffer from pharmacological limitations that preclude their use in chronic treatment. Through a medicinal chemistry effort, we have identified new compounds that have solved these limitations, and one such molecule is being taken forward as a new clinical candidate. During the previous application period, we generated induced pluripotent stem cells (iPSCs) from FRDA patients and differentiated these cells along the neuronal lineage. We have used these cells to model FRDA to study FXN gene silencing and for drug screening. In the present application, we plan to (1) optimize methods for the differentiation of hiPSCs to sensory neurons, the major cell type affected in FRDA, and to use these cells to model the disease through global gene expression studies and markers of mitochondrial dysfunction. For these experiments, we will use helper-dependent adenovirus-mediated homologous recombination to generate isogenic cell lines have the GAA?TTC repeats "corrected" to normal lengths. (2) Since cardiomyopathy is the major cause of death in FRDA, we will also model the disease in FRDA iPSC-derived cardiomyocytes. (3) We will use these two FRDA cell models to ask if improved HDAC inhibitors can reverse FRDA gene expression signatures and FRDA mitochondrial pathology. (4) Lastly, we will use neuronal cells and patient lymphocytes to identify gene expression biomarkers to be used in Phase II efficacy studies in FRDA patients. Our studies are at the forefront of development of a novel therapeutic for this currently untreatable and lethal disease.

Public Health Relevance

This application is aimed at understanding the molecular basis and pathophysiology of the inherited neurodegenerative disease Friedreich's ataxia (FRDA) and development of histone deacetylase (HDAC) inhibitors as therapeutics for this disease. We found that FRDA is an epigenetic gene silencing disease, and our efforts focus on using patient induced pluripotent stem cell-derived cell types to both model the disease and to screen our therapeutic compounds.

Agency
National Institute of Health (NIH)
Type
Research Project (R01)
Project #
2R01NS062856-06
Application #
8759653
Study Section
Cellular and Molecular Biology of Neurodegeneration Study Section (CMND)
Program Officer
Gwinn, Katrina
Project Start
Project End
Budget Start
Budget End
Support Year
6
Fiscal Year
2014
Total Cost
Indirect Cost
Name
Scripps Research Institute
Department
Type
DUNS #
City
La Jolla
State
CA
Country
United States
Zip Code
92037
Soragni, Elisabetta; Miao, Wenyan; Iudicello, Marco et al. (2014) Epigenetic therapy for Friedreich ataxia. Ann Neurol 76:489-508
Gottesfeld, Joel M; Rusche, James R; Pandolfo, Massimo (2013) Increasing frataxin gene expression with histone deacetylase inhibitors as a therapeutic approach for Friedreich's ataxia. J Neurochem 126 Suppl 1:147-54
Polak, Urszula; Hirsch, Calley; Ku, Sherman et al. (2012) Selecting and isolating colonies of human induced pluripotent stem cells reprogrammed from adult fibroblasts. J Vis Exp :
Laurent, Louise C; Ulitsky, Igor; Slavin, Ileana et al. (2011) Dynamic changes in the copy number of pluripotency and cell proliferation genes in human ESCs and iPSCs during reprogramming and time in culture. Cell Stem Cell 8:106-18
Sandi, Chiranjeevi; Pinto, Ricardo Mouro; Al-Mahdawi, Sahar et al. (2011) Prolonged treatment with pimelic o-aminobenzamide HDAC inhibitors ameliorates the disease phenotype of a Friedreich ataxia mouse model. Neurobiol Dis 42:496-505
Ku, Sherman; Soragni, Elisabetta; Campau, Erica et al. (2010) Friedreich's ataxia induced pluripotent stem cells model intergenerational GAAýýýTTC triplet repeat instability. Cell Stem Cell 7:631-7
Xu, Chunping; Soragni, Elisabetta; Chou, C James et al. (2009) Chemical probes identify a role for histone deacetylase 3 in Friedreich's ataxia gene silencing. Chem Biol 16:980-9
Gottesfeld, Joel M; Pandolfo, Massimo (2009) Development of histone deacetylase inhibitors as therapeutics for neurological disease. Future Neurol 4:775-784