G-quadruplex ligands mediate downregulation of DUX4 expression

Area of Science:

• Genetics
• Molecular Biology
• Biochemistry

Background:

• Abnormal DUX4 expression is central to facioscapulohumeral muscular dystrophy (FSHD) pathogenesis.
• The precise molecular mechanisms controlling DUX4 expression remain incompletely understood.

Purpose of the Study:

• To investigate the presence and role of G-quadruplexes (GQs) in the DUX4 locus.
• To evaluate berberine, a GQ-stabilizing compound, as a potential therapeutic agent for FSHD.

Main Methods:

• Bioinformatic analysis identified putative GQ-forming sequences in the DUX4 locus.
• Circular dichroism and NMR confirmed GQ structures in synthetic oligonucleotides.
• Spectroscopic methods assessed berberine binding affinity.
• In vitro studies in FSHD myoblasts and in vivo studies in an FSHD mouse model were conducted.

Main Results:

• G-quadruplexes were confirmed in the DUX4 enhancer, promoter, and transcript regions.
• Berberine treatment reduced DUX4 expression and downstream gene targets in FSHD myoblasts.
• In a mouse model, berberine downregulated DUX4 protein, inhibited muscle fibrosis, and rescued muscle function.

Conclusions:

• G-quadruplexes are present in the DUX4 locus, suggesting a role in FSHD.
• Berberine's ability to reduce DUX4 expression and ameliorate disease phenotypes supports its potential as an FSHD therapeutic strategy.