Abstract
Although Facioscapulohumeral Muscular Dystrophy (FSHD) was first described in 1885, an effective treatment is yet to be developed. FSHD is an autosomal dominant disorder characterized by distinct chromatin changes including DNA hypomethylation of the D4Z4 macrosatellite repeat array on a disease-permissive 4qA allele and aberrant expression of the D4Z4-embedded DUX4 retrogene in skeletal muscle. Compelling evidence indicates that this mutation-induced DUX4 expression plays a key role in disease pathogenesis.
We initially performed bioinformatic studies which predicted the presence of novel nucleic acid regulatory elements, namely G-quadruplexes (GQs), in the DUX4 genomic locus and transcript. GQ motifs were identified in transcriptional regulatory elements such as DUX4 myogenic enhancer and promoter regions, as well as near splice sites of DUX4 transcript. The structural characteristics of these putative GQs were characterised and confirmed using circular dichroism and nuclear magnetic resonance spectroscopy. Using a reporter gene system and cell transfection, mutation of GQ sequences in the DUX4 promoter led to decreased reporter gene expression indicating a role in transcription. In addition, when expression from the DUX4 genomic sequence was driven by the CMV promoter (lacking GQs) expression was also downregulated when transfected cells were treated with the GQ specific, small-molecule drug, berberine. The downregulation of DUX4 mRNA expression by berberine treatment was also confirmed in FSHD patient muscle cell cultures. High affinity of berberine binding to the GQ sequences within the DUX4 enhancer, promoter and transcript, was determined using UV, visible light and fluorescence spectroscopic techniques. Although the specific molecular mechanisms involved remain as yet to be fully unravelled, these data demonstrate for the first time that GQs are present in DUX4 locus sequences and that targeting them can reduce DUX4 expression, and thus that their pharmacological modulation may provide a novel therapeutic strategy for the treatment of FSHD.
We initially performed bioinformatic studies which predicted the presence of novel nucleic acid regulatory elements, namely G-quadruplexes (GQs), in the DUX4 genomic locus and transcript. GQ motifs were identified in transcriptional regulatory elements such as DUX4 myogenic enhancer and promoter regions, as well as near splice sites of DUX4 transcript. The structural characteristics of these putative GQs were characterised and confirmed using circular dichroism and nuclear magnetic resonance spectroscopy. Using a reporter gene system and cell transfection, mutation of GQ sequences in the DUX4 promoter led to decreased reporter gene expression indicating a role in transcription. In addition, when expression from the DUX4 genomic sequence was driven by the CMV promoter (lacking GQs) expression was also downregulated when transfected cells were treated with the GQ specific, small-molecule drug, berberine. The downregulation of DUX4 mRNA expression by berberine treatment was also confirmed in FSHD patient muscle cell cultures. High affinity of berberine binding to the GQ sequences within the DUX4 enhancer, promoter and transcript, was determined using UV, visible light and fluorescence spectroscopic techniques. Although the specific molecular mechanisms involved remain as yet to be fully unravelled, these data demonstrate for the first time that GQs are present in DUX4 locus sequences and that targeting them can reduce DUX4 expression, and thus that their pharmacological modulation may provide a novel therapeutic strategy for the treatment of FSHD.
| Original language | English |
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| Qualification | Ph.D. |
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| Award date | 1 Nov 2018 |
| Publication status | Unpublished - 28 Oct 2018 |