Unravelling Endogenous MicroRNA System Dysfunction as a New Pathophysiological Mechanism in Machado-Joseph Disease

Area of Science:

• Neuroscience
• Genetics
• Molecular Biology

Background:

• Machado-Joseph disease (MJD) is a fatal genetic neurodegenerative disorder caused by polyglutamine expansion in ataxin-3 (ATXN3).
• The precise mechanisms driving MJD pathogenesis remain elusive, and effective disease-modifying treatments are lacking.
• The 3' untranslated region (UTR) of ATXN3 is a potential target for microRNAs (miRNAs), which regulate gene expression.

Purpose of the Study:

• To investigate the role of the ATXN3 3' UTR in MJD pathogenesis.
• To determine if miRNA biogenesis and function are impaired in MJD.
• To identify specific miRNAs targeting ATXN3 and evaluate their therapeutic potential in MJD.

Main Methods:

• In vitro and in vivo studies using MJD cell and animal models.
• Analysis of ATXN3 3' UTR interactions with miRNAs.
• Assessment of miRNA biogenesis gene expression in MJD.
• Overexpression of identified miRNAs in mouse models of MJD.

Main Results:

• Endogenous miRNAs targeting the ATXN3 3' UTR significantly reduce ATXN3 expression and aggregation in vitro.
• miRNA targeting ameliorates neurodegeneration and neuroinflammation in vivo.
• MJD is associated with downregulated genes involved in miRNA biogenesis and silencing.
• Three specific miRNAs (miR-9, miR-181a, miR-494) were identified as ATXN3 3' UTR interactors with dysregulated expression in MJD.
• Overexpression of these miRNAs in mice decreased mutant ATXN3 levels, aggregate burden, and neuronal dysfunction.

Conclusions:

• Endogenous miRNAs and the ATXN3 3' UTR are critical players in MJD pathogenesis.
• Dysregulation of miRNA machinery contributes to MJD.
• Targeting specific miRNAs offers a promising therapeutic avenue for Machado-Joseph disease.