Design, Synthesis and Efficacy of New Small Molecule Therapeutics to Impede Myotonic Dystrophy

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Project Abstract Myotonic dystrophy type 1 (DM1) is the leading cause of adult-onset muscular dystrophy, yet no effective treatment strategies are available to DM1 patients. The parental grant to this supplement project is aimed at understanding the disease mechanisms of myotonic dystrophy type 1 (DM1) and identifying potential therapeutics for this multisystemic disease. DM1 is caused by a CTG expansion repeat in the 3’ untranslated region (UTR) of the dystrophia myotonica protein kinase (DMPK) gene. When transcribed, the expanded repeats sequester muscleblind-like (MBNL) proteins, a family of alternative splicing regulators, disrupting their normal cellular splicing function. Our group has previously identified existing small molecules that rescue the molecular hallmarks of DM1, such as correction of aberrant splicing and reduction of ribonuclear foci and have now designed a series of new modified polycyclic compounds (MPCs) for evaluation. While we are currently investigating the therapeutic potential and mechanism of action of these new MPCs, preliminary data suggests that they operate through either reduction of the transcription of the toxic RNA and/or increases the expression of MBNL proteins. The project for this supplement is focused on complementary studies that seek to better understand the interaction between MBNL proteins, CUG expansion RNAs, and genome-wide splicing targets through the generation, analysis, and evaluation of various synthetic MBNL proteins. The Berglund lab has previous generated several synthetic MBNL proteins and demonstrated that these proteins show improved or altered splicing activity. These data suggested that synthetic MBNL may have the potential to be used as tools for investigating splicing regulation as well as for protein therapeutics for DM. Brianna’s project will extend and leverage these studies by generating additional synthetic MBNL proteins and probing their structure and function through in vitro biochemical assays and their impact on the RNA GOF in DM1 through transcriptomic studies in cell culture. This one-year post-baccalaureate project will provide research and career development skills around a central research project aim at: (1) identifying and characterizing in vitro the target engagement specificity of engineered synthetic MBNL in the context of myotonic dystrophy type 1 expansion RNAs; and (2) determining the in vivo transcriptomic specificity and therapeutic potential of engineered synthetic MBNL in DM1 patient- derived cell lines. Determining the functional and global transcriptomic impacts of synthetic MBNL proteins will enhance our understanding of the disease biology of DM while provide critical information to improve their therapeutic potential for the treatment of DM1 and potentially other splicing-related repeat expansion diseases.