Failure of MBNL1-dependent post-natal splicing transitions in myotonic dystrophy

Lin, Xiaoyan; Miller, Jill W.; Mankodi, Ami; Kanadia, Rahul N.; Yuan, Yuan; Moxley, Richard T.; Swanson, Maurice S.; Thornton, Charles A.

doi:10.1093/hmg/ddl132

Cited by 456 publications

(647 citation statements)

References 34 publications

Supporting

Mentioning

605

Contrasting

Unclassified

Order By: Relevance

“…This could be related to developmentally regulated reductions in CUG-BP1 or MBNL1 (ref. 22 ). CUG-BP1 is highly expressed in myoblasts and developing muscle and markedly reduced in postnatal skeletal muscle.…”

mentioning

confidence: 99%

Reversible model of RNA toxicity and cardiac conduction defects in myotonic dystrophy

et al. 2006

View full text Add to dashboard Cite

Myotonic dystrophy (DM1), the most common muscular dystrophy in adults, is caused by an expanded (CTG) n tract in the 3′ UTR of the gene encoding myotonic dystrophy protein kinase (DMPK) 1 , which results in nuclear entrapment of the 'toxic' mutant RNA and interacting RNAbinding proteins (such as MBNL1) in ribonuclear inclusions 2 . It is unclear if therapy aimed at eliminating the toxin would be beneficial. To address this, we generated transgenic mice expressing the DMPK 3′ UTR as part of an inducible RNA transcript encoding green fluorescent protein (GFP). We were surprised to find that mice overexpressing a normal DMPK 3′ UTR mRNA reproduced cardinal features of myotonic dystrophy, including myotonia, cardiac conduction abnormalities, histopathology and RNA splicing defects in the absence of detectable nuclear inclusions. However, we observed increased levels of CUG-binding protein (CUG-BP1) in skeletal muscle, as seen in individuals with DM1. Notably, these effects were reversible in both mature skeletal and cardiac muscles by silencing transgene expression. These results represent the first in vivo proof of principle for a therapeutic strategy for treatment of myotonic dystrophy by ablating or silencing expression of the toxic RNA molecules.Common features of adult-onset DM1 include myotonia, progressive skeletal muscle loss, cardiac conduction defects, smooth muscle dysfunction, cataracts and insulin resistance 2 . The normal number of CTG repeats (n = 5 to ~30) is higher (n = 50 to >3,000) in individuals with DM1 (ref. 1 ). Unlike the wild-type transcript, mutant DMPK mRNA forms nuclear aggregates 3,4 and is thought to trigger dominant effects by aberrant interactions with or altered activity of RNA splicing factors, principally members of the muscleblind-like (MBNL) family (such as MBNL1) and the CUG-BP and ETR3-like factor (CELF) family (such as CUG-BP1), leading to abnormal splicing of specific RNAs such as chloride channel (Clcn1), insulin Correspondence should be addressed to M.S.M. (mahadevan@virginia.edu). 4 These authors contributed equally to this work. AUTHOR CONTRIBUTIONSM.S.M., R.S.Y., Q.Y., C.D.F.-M., T.D.B. and L.H.P. performed experimental work and data analysis. S.B. generated the transgene constructs. M.S.M. was responsible for conceptual design and execution. COMPETING INTERESTS STATEMENTThe authors declare that they have no competing financial interests. One potential therapeutic approach in DM1 is to get rid of the toxic RNA from cells. However, it is unclear if this will alleviate the effects of the disease. We used the tetracycline (Tet) inducible system with the reverse tetracycline transactivator (rtTA) to generate double transgenic mice harboring (i) a Tet-responsive, DMPK promoter 10,11 -driven transgene (named GFP-DMPK 3′ UTR) expressing the DMPK 3′ UTR mRNA as part of a GFP transcript, and (ii) a constitutively expressed rtTA transgene (Fig. 1a) Fig. 1). Notably, RNA blots of skeletal muscle RNA showed two major species due to alternative use of polyadenylation signal...

show abstract

mentioning

confidence: 99%

Reversible model of RNA toxicity and cardiac conduction defects in myotonic dystrophy

et al. 2006

View full text Add to dashboard Cite

show abstract

“…Muscleblind proteins are nuclear factors that participate in the developmental regulation of alternative splicing [6,23], and they also may regulate the transport and decay of mRNA [24]. However, except for microtubuleassociated protein tau, it is not known which transcripts expressed in subsynaptic nuclei or motor neurons are subject to CUG exp -induced spliceopathy.…”

Section: Discussionmentioning

confidence: 99%

“…HSA LR transgenic mice that express CUG exp RNA in skeletal muscle were described previously [20]. CUG exp expression in these transgenic mice is controlled by regulatory elements from the human skeletal actin gene, which results in ribonuclear foci, myotonia, myopathy, and a spliceopathy that is similar to human DM1 [6]. Transgenic mice that express human DMPK (hDMPK) and mice with a targeted disruption of the DMPK gene were described previously [21].…”

Section: Tissue Samplesmentioning

confidence: 99%

“…This region excludes the kinase homology domains of DMPK. IF was performed with primary antibodies against the following proteins: DMPK (antibody 5244, 1:2000), developmental myosin heavy chain (MHC) (1:60; Novacastra), MBNL1 (antibody A2764, 1:10,000 [6]), or choline acetyl transferase (Chemicon, 1:100). Secondary antibodies were labeled with Alexa 488, 568, or 594 (Invitrogen, 1:400).…”

Section: Fluorescence In Situ Hybridization (Fish) and Immunofluorescmentioning

confidence: 99%

“…A multi-step model for DM1 pathogenesis has been proposed [reviewed in reference 2]: (1) the mutant gene is transcribed, giving rise to transcripts that contain an expanded CUG repeat (CUG exp ) [3]; (2) the CUG exp transcripts accumulate in RNA nuclear (ribonuclear) foci [4]; (3) RNA binding proteins, including muscleblind 1 (MBNL1), are sequestered in the ribonuclear foci [5,6]; (4) altered activity of splicing factors, such as MBNL1 and CUG binding protein 1, leads to abnormal alternative splicing for a sub-group of pre-mRNAs [7,8]; and (5) expression of inappropriate splice products leads to symptoms of DM1. For example, CUG exp RNA triggers abnormal alternative splicing of the ClC-1 chloride channel, and the predominant ClC-1 splice products expressed in DM1 muscle are devoid of ion channel activity [9][10][11].…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Ribonuclear foci at the neuromuscular junction in myotonic dystrophy type 1

Wheeler

Krym

Thornton

2007

Neuromuscular Disorders

View full text Add to dashboard Cite

In myotonic dystrophy type 1 (DM1) the muscle fibers express RNA containing an expanded CUG repeat (CUG exp ). The CUG exp RNA is retained in the nucleus, forming ribonuclear foci. Splicing factors in the muscleblind (MBNL) family are sequestered in ribonuclear foci, resulting in abnormal regulation of alternative splicing. In extrajunctional nuclei, these effects on splicing regulation lead to reduced chloride conductance and altered insulin receptor signaling. Here we show that CUG exp RNA is also expressed in subsynaptic nuclei of muscle fibers and in motor neurons in DM1, causing sequestration of MBNL1 protein in both locations. In a transgenic mouse model, expression of CUG exp RNA at high levels in extrajunctional nuclei replicates many features of DM1, but the toxic RNA is poorly expressed in subsynaptic nuclei and the mice fail to develop denervation-like features of DM1 myopathology. Our findings indicate that subsynaptic nuclei and motor neurons are at risk for DM1-induced spliceopathy, which may affect function or stability of the neuromuscular junction.

show abstract

Molecular Genetic Basis of Myotonic Dystrophy

Radvánszky

Kádaši

2013

Encyclopedia of Life Sciences

View full text Add to dashboard Cite

Myotonic dystrophy (DM) comprises at least two genetically distinct forms, both of which are caused by expansions of microsatellite repeats. Expansion of a CTG repeat in the DMPK gene leads to DM1, whereas expansion of a CCTG repeat in the ZNF9 gene causes DM2. In both cases, the repeat units may expand to several thousand repeats. Strikingly similar phenotypes, mutation types and pathological findings suggest a common pathogenic mechanism for both DM1 and DM2. However, the differences between DM1 and DM2 may be a consequence of locus‐specific effects involving haploinsufficiency of different genes and downstream events triggered by CUG or CCUG transcripts. Altogether, the complex DM1 and DM2 phenotypes are probably caused by specific combinations of several possible pathogenic pathways in different tissues of individual patients. Key Concepts: Myotonic dystrophy type 1 (DM1) and type 2 (DM2) are complex multisystemic disorders with highly similar but not identical symptoms. Both DM1 and DM2 are caused by expansions of microsatellite repeats, however, in two distinct genes ( DMPK and ZNF9 ). Mechanisms leading to the DM1 and DM2 symptoms are very complex with several possible pathogenic pathways. The best described pathogenic pathway involves the misregulation of two alternative splicing regulators, CUG‐BP1 (gain of function) and MBNL1 (loss of function), leading to target‐specific splicing alterations. Both CUG‐BP1 and MBNL1 are multifunctional proteins; thus, their activation/sequestration have effect on further cellular functions such as transcription, translation and mRNA decay. Both DM1 and DM2 causing expansions can also lead to decreased levels of proteins coded by genes around and near to the expansion sites, such as DMPK , ZNF9 , SIX5 and DMWD. The exact molecular pathogenic mechanism in certain tissues is probably not uniform, it rather represents a specific combination of several distinct pathogenic pathways.

show abstract

Failure of MBNL1-dependent post-natal splicing transitions in myotonic dystrophy

Cited by 456 publications

References 34 publications

Reversible model of RNA toxicity and cardiac conduction defects in myotonic dystrophy

Reversible model of RNA toxicity and cardiac conduction defects in myotonic dystrophy

Ribonuclear foci at the neuromuscular junction in myotonic dystrophy type 1

Molecular Genetic Basis of Myotonic Dystrophy

Contact Info

Product

Resources

About