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Alternative splicing and gene expression in a mouse model of myotonic dystrophy

ABSTRACT: Distinct RNA-mediated impacts on alternative splicing and extracellular matrix gene expression in a mouse model of myotonic dystrophy. Myotonic dystrophy (DM1) is associated with expression of expanded CTG DNA repeats as RNA (CUGexp RNA). To test whether CUGexp RNA creates a global splicing defect, we compared skeletal muscle of two mouse DM1 models, one expressing a CTGexp transgene, and another homozygous for a defective Mbnl1 gene. Strong correlation in splicing changes for ~100 new Mbnl1-regulated exons indicates loss of Mbnl1 explains >80% of the splicing pathology due to CUGexp RNA. In contrast, only about half of mRNA level changes can be attributed to loss of Mbnl1, indicating CUGexp RNA has Mbnl1-independent effects, particularly on mRNAs for extracellular matrix (ECM) proteins. We propose that CUGexp RNA causes two separate effects: loss of Mbnl1 function, disrupting splicing, and loss of another function that disrupts ECM mRNA regulation, possibly mediated by MBNL2. These findings reveal unanticipated similarities between DM1 and other muscular dystrophies.

ORGANISM(S): Mus musculus

PROVIDER: GSE17986 | GEO | 2010/01/24

SECONDARY ACCESSION(S): PRJNA120019

REPOSITORIES: GEO

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Project description:Myotonic dystrophy type 1 (DM1) is an RNA dominant disease in which mutant transcripts containing an expanded CUG repeat (CUGexp) cause muscle dysfunction by interfering with biogenesis of other mRNAs. The toxic effects of mutant RNA are mediated partly through sequestration of splicing regulator Muscleblind-like 1 (Mbnl1), a protein that binds to CUGexp RNA. A gene that is prominently affected encodes chloride channel 1 (Clcn1), resulting in hyperexcitability of muscle (myotonia). To identify DM1-affected genes and study mechanisms for dysregulation, we performed global mRNA profiling in transgenic mice that express CUGexp RNA, as compared to Mbnl1 knockout and Clcn1 null mice. We found that the majority of changes induced by CUGexp RNA in skeletal muscle can be explained by reduced activity of Mbnl1, including many changes that are secondary to myotonia. The pathway most affected comprises genes involved in calcium signaling and homeostasis. Some effects of CUGexp RNA on gene expression are caused by abnormal alternative splicing or downregulation of Mbnl1-interacting mRNAs. However, several of the most highly dysregulated genes showed altered transcription, as indicated by parallel changes of the corresponding premRNAs. These results support the idea that trans-dominant effects of CUGexp RNA on gene expression in this transgenic model may occur at the level of transcription, RNA processing, and mRNA decay, and are mediated mainly but not entirely through sequestration of Mbnl1. Experiment Overall Design: All experiments involved generating expression profiles of quadriceps muscles taken from mice. Experiments 1 and 2: samples were hybridized to Moe430A and Moe430B arrays. Experiment 3: samples were hybridized to Mouse Genome 430 2.0 array. Experiment 1 compared expression profiles of wild-type mice (FVB strain) with two lines, designated 20b and 41, of CUGexp transgenic mice with FVB background. Experiment 2 compared expression profiles of Clcn1-null (myotonic) mice with the wild-type background strain (BALB). Experiment 3 compared expression profiles of Mbnl1-null mice with the wild-type background strain (FVB).

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Alternative splicing and gene expression in a mouse model of myotonic dystrophy

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