dc.description.abstract |
Myotonic dystrophy type 1 (DM1) is the most common form of adult-onset muscular dystrophy which has a wide variety of symptoms, but is known for its classic symptom myotonia. Myotonia is the ability to contract, but not relax one’s muscles. The mis-splicing of a chloride channel gene Clcn1 causes myotonia in DM1 patients. To address symptoms such as myotonia, this thesis aims to test the effect of two potential treatments, heptamidine and furamidine, on splicing events in a DM1 mouse model. The HSALR mouse model replicates the tri-nucleotide CTG repeat that DM1 patients have in the 3’ UTR of the DMPK gene. Repeats in affected individuals range from 38 to more than thousands. This transgenic mouse expresses 220 CUG repeats which form a toxic RNA structure. Like a sponge, the toxic RNA soaks up the MBNL proteins. MBNL proteins are responsible for regulating the alternative splicing of fetal vs. adult isoforms of more than 200 splicing events. When sequestered, the MBNL proteins can no longer regulate these events, resulting in mis-splicing of its targets (such as Clcn1), leading to the symptoms of the disease (like myotonia) Two small molecules have been shown to rescue (reverse) mis-splicing in the transgenic mouse model. Heptamidine and furamidine were each administered to three sibling-matched mice. Three additional mice, which also expressed the CUG repeats, did not receive drug treatment as a control. Their transcriptomes were sequenced and a MISO (Mixture-of-Isoforms) splicing analysis was preformed to quantify and visualize splicing rescue across treatments. Gene expression changes were visualized to compare treatment off-target effects. This quantitation and comparison will confirm and identify known splicing biomarkers of DM1, leading to an improved understanding of how these small molecules are acting at a molecular level. This knowledge will inform future drug design to treat DM1 and other diseases caused by toxic repeat RNA. |
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