Alternative splicing and gene expression in a mouse model of myotonic dystrophy
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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. MBNL1 knockout and HSALR mice on FVB background. 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. These samples were compared to the skeletal muscle of a wildtype mouse.
RNA介导的强直性肌营养不良小鼠模型可变剪接与细胞外基质基因表达的差异化影响 强直性肌营养不良1型（Myotonic dystrophy 1, DM1）与扩增的CTG DNA重复序列转录生成的RNA（CUGexp RNA）的表达密切相关。为验证CUGexp RNA是否会引发全局性剪接缺陷，本研究对两种DM1小鼠模型的骨骼肌组织进行了对比分析：一种携带CTGexp转基因，另一种为Mbnl1基因缺陷型纯合子。针对约100个新发现的受Mbnl1调控的外显子，其剪接变化呈现显著相关性，这表明Mbnl1功能缺失可解释CUGexp RNA引发的剪接病理改变中80%以上的部分。与之相反，仅约半数的mRNA水平变化可归因于Mbnl1功能缺失，提示CUGexp RNA存在不依赖Mbnl1的调控效应，尤其对细胞外基质（extracellular matrix, ECM）蛋白编码mRNA的影响更为显著。本研究提出，CUGexp RNA可引发两类独立效应：一是Mbnl1功能缺失，进而干扰可变剪接；二是另一项功能的丧失，该功能可破坏ECM mRNA的调控，这一过程可能由MBNL2介导。本研究结果揭示了DM1与其他肌营养不良症之间此前未被发现的相似性。 本研究采用FVB品系背景下的MBNL1基因敲除小鼠与HSALR小鼠。为验证CUGexp RNA是否会引发全局性剪接缺陷，本研究对两种DM1小鼠模型的骨骼肌组织进行了对比分析：一种携带CTGexp转基因，另一种为Mbnl1基因缺陷型纯合子，并将上述样本与野生型小鼠的骨骼肌组织进行了对照比较。
