HNRNPA1-induced spliceopathy in a transgenic mouse model of myotonic dystrophy
HNRNPA1-induced spliceopathy in a transgenic mouse model of myotonic dystrophy
复制标题
HNRNPA1 在强直性肌营养不良转基因小鼠模型中诱导的剪接病
DOI：
10.1073/pnas.1907297117
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发表时间：
2020-03-10
影响因子：
11.1
通讯作者：
Xie, Wei
中科院分区：
文献类型：
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作者：
Li, Moyi;Zhuang, Yan;Xie, Wei
强直性肌营养不良1型（DM 1）是微卫星扩增障碍中RNA介导的疾病的模型。DM 1是由CTG扩增（CTGexp）和CUGexp RNA的表达引起的，CUGexp RNA可隔离肌盲样（MBNL）蛋白，同时还触发CUGBP 1/ETR 3样因子1（CELF 1）的过度磷酸化。这些蛋白质调节RNA加工中的发育转变，因此DM 1的特征是在成人中保留胎儿RNA加工模式。尽管目前的证据表明CELF 1是MBNL活性的特异性拮抗剂，但这项研究表明，另一种蛋白质HNRNPA 1在正常发育期间也下调，但在DM 1中上调，它也诱导胎儿剪接转变。因此，DM 1疾病是由对增殖和分化都很重要的多种RNA加工因子表达的不平衡引起的。对强直性肌营养不良1型（DM 1）的研究已经导致了由非编码微卫星扩增引起的遗传性疾病的RNA介导的疾病模型。该模型提出，DM 1疾病表现是由成人组织中胎儿RNA加工模式的逆转引起的，这是由于毒性CUG RNA扩增（CUGexp）的表达导致肌盲样减少，但增加了CUGBP 1/ETR 3样因子1（CELF 1）的选择性剪接活性。在这里，我们测试这个模型在体内，使用小鼠HSALR聚（CUG）模型DM 1和重组腺相关病毒（rAAV）介导的特定剪接因子的转导。令人惊讶的是，HNRNPA 1的系统性过表达，以前没有连接到DM 1，也转移DM 1相关的剪接靶向胎儿亚型，导致更严重的肌无力/肌病早在4至6周后转导，而rAAV对照不受影响。HNRNPA 1的过表达促进分化成肌细胞中代表性DM 1相关剪接靶标的胎儿外显子的包含，并且rAAV-mycHnrnpa 1注射肌肉的HITS-CLIP揭示了HNRNPA 1与这些靶标的体内直接相互作用。与CELF 1类似，HNRNPA 1蛋白水平在出生后发育期间下降，但在再生小鼠肌肉和DM 1骨骼肌中升高。我们的研究表明，CUGexp RNA触发异常表达的多个核RNA结合蛋白，包括CELF 1和HNRNPA 1，拮抗MBNL活性，促进胎儿剪接模式。
Significance Myotonic dystrophy type 1 (DM1) is a model for RNA-mediated disease in microsatellite expansion disorders. DM1 is caused by CTG expansions (CTGexp) and expression of CUGexp RNAs that sequester muscleblind-like (MBNL) proteins, while also triggering hyperphosphorylation of CUGBP1/ETR3-like factor 1 (CELF1). These proteins regulate developmental transitions in RNA processing, so DM1 is characterized by retention of fetal RNA processing patterns in adults. Although current evidence indicates that CELF1 is a specific antagonist of MBNL activity, this study reveals that another protein, HNRNPA1, is also downregulated during normal development but upregulated in DM1, where it also induces fetal splicing shifts. Thus, DM1 disease results from an imbalance in the expression of multiple RNA processing factors important for both proliferation and differentiation. Studies on myotonic dystrophy type 1 (DM1) have led to the RNA-mediated disease model for hereditary disorders caused by noncoding microsatellite expansions. This model proposes that DM1 disease manifestations are caused by a reversion to fetal RNA processing patterns in adult tissues due to the expression of toxic CUG RNA expansions (CUGexp) leading to decreased muscleblind-like, but increased CUGBP1/ETR3-like factor 1 (CELF1), alternative splicing activities. Here, we test this model in vivo, using the mouse HSALR poly(CUG) model for DM1 and recombinant adeno-associated virus (rAAV)-mediated transduction of specific splicing factors. Surprisingly, systemic overexpression of HNRNPA1, not previously linked to DM1, also shifted DM1-relevant splicing targets to fetal isoforms, resulting in more severe muscle weakness/myopathy as early as 4 to 6 wk posttransduction, whereas rAAV controls were unaffected. Overexpression of HNRNPA1 promotes fetal exon inclusion of representative DM1-relevant splicing targets in differentiated myoblasts, and HITS-CLIP of rAAV-mycHnrnpa1-injected muscle revealed direct interactions of HNRNPA1 with these targets in vivo. Similar to CELF1, HNRNPA1 protein levels decrease during postnatal development, but are elevated in both regenerating mouse muscle and DM1 skeletal muscle. Our studies suggest that CUGexp RNA triggers abnormal expression of multiple nuclear RNA binding proteins, including CELF1 and HNRNPA1, that antagonize MBNL activity to promote fetal splicing patterns.