Abstract
ABSTRACTMyotonic dystrophy 1 (DM1) is a multisystem disorder primarily affecting the central nervous system, heart and skeletal muscle. It is caused by an expansion of the CTG trinucleotide repeats in the 3′ untranslated region of the DMPK gene. Although patient myoblasts have been used for studying the disease in vitro, the invasiveness as well as the low accessibility to muscle biopsies motivate the development of alternative reliable myogenic models. Here, we established two DM1 induced pluripotent stem (iPS) cell lines from patient-derived fibroblasts and, using the PAX7 conditional expression system, differentiated these into myogenic progenitors and, subsequently, terminally differentiated myotubes. Both DM1 myogenic progenitors and myotubes were found to express the intranuclear RNA foci exhibiting sequestration of MBNL1. Moreover, we found the DM1-related mis-splicing, namely BIN1 exon 11 in DM1 myotubes. We used this model to test a specific therapy, antisense oligonucleotide treatment, and found that this efficiently abolished RNA foci and rescued BIN1 mis-splicing in DM1 iPS cell-derived myotubes. Together, our results demonstrate that myotubes derived from DM1 iPS cells recapitulate the critical molecular features of DM1 and are sensitive to antisense oligonucleotide treatment, confirming that these cells can be used for in vitro disease modeling and candidate drug testing or screening.This article has an associated First Person interview with the first author of the paper.
Highlights
Myotonic dystrophy 1 (DM1) is an autosomal dominant multisystemic disorder that causes myotonia and progressive muscle weakness and wasting
Various molecular events related to the CTG repeat expansion have been associated with the disease phenotype (Klesert et al, 2000; Reddy et al, 1996; Ho et al, 2005), but the most relevant is a toxic RNA gain-of-function of the dystrophia myotonica protein kinase (DMPK) mutant transcripts (Mankodi et al, 2000). mRNAs containing expanded CUG repeats fold into extended stem-loop structures that form RNA foci (Taneja et al, 1995; Napierala and Krzyzosiak, 1997; Tian et al, 2000)
Sequestration of the splicing factor MBNL1 by the RNA foci, which leads to splicing disruption of MBNL1 target genes, is the main molecular feature associated with DM1 skeletal muscle pathology (Meola and Cardani, 2015; Tang et al, 2012; Fugier et al, 2011)
Summary
Myotonic dystrophy 1 (DM1) is an autosomal dominant multisystemic disorder that causes myotonia and progressive muscle weakness and wasting. MRNAs containing expanded CUG repeats fold into extended stem-loop structures that form RNA foci (Taneja et al, 1995; Napierala and Krzyzosiak, 1997; Tian et al, 2000). These RNA foci are retained in the nucleus and interact with RNA binding proteins, such as Staufen ( known as STAU1), hnRNP H ( known as HNRNPH1) and members of the MBNL family (Ravel-Chapuis et al, 2012; Paul et al, 2006; Miller et al, 2000). DM1 is a complex disease that remains to be fully understood
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