A flow cytometry-based screen identifies MBNL1 modulators that rescue splicing defects in myotonic dystrophy type I

Area of Science:

• Molecular Biology
• Genetics
• Drug Discovery

Background:

• Myotonic dystrophy type 1 (DM1) stems from expanded CTG repeats in the DMPK gene.
• These repeats sequester Muscleblind-like protein 1 (MBNL1), disrupting pre-mRNA splicing.
• MBNL1 overexpression rescues splicing defects in DM1 models, suggesting a therapeutic avenue.

Purpose of the Study:

• To establish a high-throughput screening system for identifying compounds that upregulate MBNL1.
• To discover novel pharmacological modulators for MBNL1 expression.

Main Methods:

• Engineered a ZsGreen tag into the endogenous MBNL1 locus in HeLa cells.
• Developed a flow cytometry-based screening system to quantify MBNL1 levels.
• Screened small molecule compound libraries and characterized hit compounds.

Main Results:

• Identified over thirty small molecules that doubled MBNL1 expression.
• Two hits, ISOX and vorinostat (HDAC inhibitors), increased MBNL1 in DM1 patient fibroblasts.
• These compounds partially rescued the splicing defect associated with (CUG)exp repeats.

Conclusions:

• A flow cytometry-based screen is feasible for identifying MBNL1-upregulating compounds.
• HDAC inhibitors show potential for treating DM1 by restoring MBNL1 function.
• This screen can identify both small molecules and potential drug targets for MBNL1 upregulation.