Molecular, Physiological, and Motor Performance Defects in DMSXL Mice Carrying >1,000 CTG Repeats from the Human DM1 Locus
Molecular, Physiological, and Motor Performance Defects in DMSXL Mice Carrying >1,000 CTG Repeats from the Human DM1 Locus
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DOI：
10.1371/journal.pgen.1003043
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发表时间：
2012-11-01
期刊：
影响因子：
4.5
通讯作者：
Gourdon, Genevieve
中科院分区：
文献类型：
--
作者：
Huguet, Aline;Medja, Fadia;Gourdon, Genevieve
强直性肌营养不良1型(DM1)是由DM蛋白激酶(DMPK)基因第39非编码区不稳定的CTG重复扩增引起的。携带CUG扩增的DMPK转录本形成核焦点，影响各种RNA转录本的剪接调控。此外，DM1中还描述了DMPK基因的双向转录和重复转录产物的非常规RNA翻译。现已明确，该病可能涉及多种致病途径，包括基因表达、RNA稳定性和剪接调节、蛋白质翻译和微小RNA代谢的变化。我们之前培育了带有45kb的DM1基因座和300个CTG重复序列的转基因小鼠(DM300小鼠)。经过连续选育和高水平的CTG重复序列不稳定，我们获得了携带>；1000 CTG的转基因小鼠(DMSXL小鼠)。在这里，我们首次描述了DMPK正义转录本在DMSXL和人类组织中的表达模式。有趣的是，我们还证明了DMPK反义转录本在各种DMSXL和人类组织中都有表达，并且正义和反义转录本都积累在独立的核病灶中，而不是共同定位在一起。DMSXL小鼠中DM1相关的RNA毒性的分子特征(如病灶堆积和轻微剪接错误)与高死亡率、生长迟缓和肌肉缺陷(组织病理学异常、肌肉力量下降和运动能力降低)有关。我们发现，较低水平的IGFBP-3可能导致DMSXL生长迟缓，而蛋白酶体活性增加可能影响肌肉功能。这些数据表明，人类DM1基因座携带非常大的扩增，在转基因小鼠中诱导了各种分子和生理缺陷，在一定程度上反映了DM1。因此，DMSXL小鼠提供了一种动物工具来破译疾病机制的各个方面。此外，这些小鼠可用于测试系统治疗策略对分子和生理表型的临床前影响。
Myotonic dystrophy type 1 (DM1) is caused by an unstable CTG repeat expansion in the 39UTR of the DM protein kinase (DMPK) gene. DMPK transcripts carrying CUG expansions form nuclear foci and affect splicing regulation of various RNA transcripts. Furthermore, bidirectional transcription over the DMPK gene and non-conventional RNA translation of repeated transcripts have been described in DM1. It is clear now that this disease may involve multiple pathogenic pathways including changes in gene expression, RNA stability and splicing regulation, protein translation, and micro-RNA metabolism. We previously generated transgenic mice with 45-kb of the DM1 locus and >300 CTG repeats (DM300 mice). After successive breeding and a high level of CTG repeat instability, we obtained transgenic mice carrying >1,000 CTG (DMSXL mice). Here we described for the first time the expression pattern of the DMPK sense transcripts in DMSXL and human tissues. Interestingly, we also demonstrate that DMPK antisense transcripts are expressed in various DMSXL and human tissues, and that both sense and antisense transcripts accumulate in independent nuclear foci that do not co-localize together. Molecular features of DM1-associated RNA toxicity in DMSXL mice (such as foci accumulation and mild missplicing), were associated with high mortality, growth retardation, and muscle defects (abnormal histopathology, reduced muscle strength, and lower motor performances). We have found that lower levels of IGFBP-3 may contribute to DMSXL growth retardation, while increased proteasome activity may affect muscle function. These data demonstrate that the human DM1 locus carrying very large expansions induced a variety of molecular and physiological defects in transgenic mice, reflecting DM1 to a certain extent. As a result, DMSXL mice provide an animal tool to decipher various aspects of the disease mechanisms. In addition, these mice can be used to test the preclinical impact of systemic therapeutic strategies on molecular and physiological phenotypes.