Todd Peter K, Ackall Feras Y, Hur Junguk, Sharma Kush, Paulson Henry L, Dowling James J
Department of Neurology, University of Michigan, Ann Arbor, MI 48109, USA.
Dis Model Mech. 2014 Jan;7(1):143-55. doi: 10.1242/dmm.012427. Epub 2013 Oct 2.
Myotonic dystrophy type I (DM1) is a multi-system, autosomal dominant disorder caused by expansion of a CTG repeat sequence in the 3'UTR of the DMPK gene. The size of the repeat sequence correlates with age at onset and disease severity, with large repeats leading to congenital forms of DM1 associated with hypotonia and intellectual disability. In models of adult DM1, expanded CUG repeats lead to an RNA toxic gain of function, mediated at least in part by sequestering specific RNA splicing proteins, most notably muscleblind-related (MBNL) proteins. However, the impact of CUG RNA repeat expression on early developmental processes is not well understood. To better understand early developmental processes in DM1, we utilized the zebrafish, Danio rerio, as a model system. Direct injection of (CUG)91 repeat-containing mRNA into single-cell embryos induces toxicity in the nervous system and muscle during early development. These effects manifest as abnormal morphology, behavioral abnormalities and broad transcriptional changes, as shown by cDNA microarray analysis. Co-injection of zebrafish mbnl2 RNA suppresses (CUG)91 RNA toxicity and reverses the associated behavioral and transcriptional abnormalities. Taken together, these findings suggest that early expression of exogenously transcribed CUG repeat RNA can disrupt normal muscle and nervous system development and provides a new model for DM1 research that is amenable to small-molecule therapeutic development.
I型强直性肌营养不良症（DM1）是一种多系统常染色体显性疾病，由DMPK基因3'非翻译区CTG重复序列的扩增引起。重复序列的大小与发病年龄和疾病严重程度相关，大的重复序列会导致与肌张力减退和智力残疾相关的先天性DM1形式。在成年DM1模型中，扩增的CUG重复序列导致RNA功能获得性毒性，至少部分是通过隔离特定的RNA剪接蛋白介导的，最显著的是与肌肉盲相关（MBNL）的蛋白。然而，CUG RNA重复序列表达对早期发育过程的影响尚不清楚。为了更好地了解DM1中的早期发育过程，我们利用斑马鱼（Danio rerio）作为模型系统。将含有（CUG）91重复序列的mRNA直接注射到单细胞胚胎中，会在早期发育过程中诱导神经系统和肌肉产生毒性。如cDNA微阵列分析所示，这些影响表现为形态异常、行为异常和广泛的转录变化。共注射斑马鱼mbnl2 RNA可抑制（CUG）91 RNA毒性，并逆转相关的行为和转录异常。综上所述，这些发现表明，外源转录的CUG重复RNA的早期表达会破坏正常的肌肉和神经系统发育，并为DM1研究提供了一个适用于小分子治疗开发的新模型。
