Subodh Kumar Mishra(1), Sawyer M. Hicks(1), Jesus A. Frias(1), Sweta Vangaveti(1), John D. Cleary(1), Masayuki Nakamori(2), Kaalak Reddy(1), J. Andrew Berglund(1)
Affiliation:
1: The RNA Institute, University at Albany, State University of New York, Albany, NY,12222;
2: Department of Neurology, Osaka University Graduate School of Medicine, 565-0871 Osaka, Japan
Background: Myotonic dystrophy (DM) is the leading cause of adult-onset muscular dystrophy. DM is characterized by multisystemic manifestations such as progressive muscle weakness, atrophy, myotonia, cataracts, cardiac dysrhythmia, sleep disturbance, cognitive impairment, and gastrointestinal issues. DM type 1 (DM1) and DM type 2 (DM2) are two genetically distinct forms of DM. DM1 is caused by CTG repeat expansion in 3’ UTR of the DMPK gene, and DM2 is caused by CCTG repeat expansion in intron 1 of the CNBP gene. CUG and CCUG repeat RNA expansions sequester the MBNL family of alternative splicing regulatory proteins into ribonuclear foci, leading to pathogenic mis-splicing. Currently, there are no FDA-approved disease-targeting treatments available for DM. The current study identified quercetin as a promising lead molecule as a disease-targeting therapeutic for DM.
Methods: Our lab has developed a HeLa screening cell line that permits the ratio-metric evaluation of toxic r(CUG)480 levels compared to an r(CUG)0 control1. This cell line was used to screen the NCI natural product library. Patient-derived fibroblast (DM1 and DM2) and muscle cell lines (DM1) were used to measure mis-spicing rescue and DMPK/CNBP transcripts levels. DM1 mice were used to measure the CTG transcripts levels, mis-splicing rescue, and myotonia.
Results and conclusion: Screening in the HeLa cells revealed the dietary flavonoid quercetin as a selective modulator of toxic CUG RNA levels. Quercetin treatment reduced the toxic RNA level and alleviated the MBNL-dependent mis-splicing in DM1 and DM2 patient-derived cells. EMIQ is a bioavailable form of quercetin, and its treatment in DM1 mice reduced the toxic CUG RNA levels, mitigated mis-splicing, and reduced myotonia. The excellent safety profile of quercetin with little to no adverse effects and tentative mechanism of action positions quercetin as a potentially safe compound for therapeutic consideration for DM.