Advisory Committee Chair
Rui Zhao
Advisory Committee Members
Michelle Gray
Farah Lubin
Jill Napierala
Marek Napierala
David Schneider
Document Type
Dissertation
Date of Award
2022
Degree Name by School
Doctor of Philosophy (PhD) Heersink School of Medicine
Abstract
Friedreich’s ataxia (FRDA) is the most common inherited ataxia worldwide. This autosomal recessive neurodegenerative disorder manifests in the central and peripheral nervous system but also affects the cardiovascular and endocrine systems. No effective treatment is available. FRDA is caused by expansion of GAA repeat tracts in intron 1 of the frataxin (FXN) gene on both alleles. An inverse correlation between FXN levels and GAA repeat length exists. Frataxin is a mitochondrial protein participating in iron-sulfur (Fe-S) cluster formation. Frataxin deficiency results in reduced activity of Fe-S-containing enzymes involved in critical biological processes, such as cellular respiration and DNA repair. Expansion of GAA repeats causes FXN gene silencing and different epigenetic mechanisms have been implicated in this process. Expansion of GAA repeats causes formation of non B-DNA structures, H-DNA and R-loops, leading to arrest of RNA polymerase II progression. Posttranslational histone modifications characteristic of heterochromatin, specifically trimethylation of H3K9 and H3K27, are enriched upstream and downstream of the expanded GAA repeats and at the FXN promoter. Also, histones in these FXN regulatory regions are hypoacetylated. Differentially expressed miRNAs acting as independent epigenetic regulators that target FXN have also been implicated in its silencing. iv Reversing FXN silencing is considered an achievable therapeutic approach. Epigenetic regulatory mechanisms can be modulated by using small molecules or targeting the expression of specific miRNAs to increase FXN expression. We aimed to create and characterize a reporter cell line, based on FRDA induced pluripotent stem cells (iPSCs), and utilize it to screen an epigenetic compound library to identify novel inducers of FXN. Selected compounds were evaluated in FRDA iPSC-differentiated neuronal cell line models. To determine the influence of the GAA repeat expansion on regulating FXN expression, isogenic FRDA iPSC lines were created by excision of the GAA repeats and analyzed in comparison with control and FRDA neuronal cells. A comprehensive transcriptome analysis was performed to identify differentially expressed miRNAs and their potential targets in FRDA cells. The outcome of these studies contributes to discovery of novel FXN inducers, as well as provides insight into mechanisms regulating FXN transcription in FRDA.
Recommended Citation
Schreiber, Anna Maria, "Targeting the Frataxin Transcriptional Defect as a Therapeutic Approach for Friedreich's Ataxia" (2022). All ETDs from UAB. 331.
https://digitalcommons.library.uab.edu/etd-collection/331
