Cytoplasmic CUG RNA foci are insufficient to elicit key DM1 features

Warunee Dansithong, Cordula M. Wolf, Partha Sarkar, Sharan Paul, Andy Chiang, Ian Holt, Glenn E. Morris, Dorothy Branco, Megan C. Sherwood, Lucio Comai, Charles I. Berul, Sita Reddy

Research output: Contribution to journalArticle

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Abstract

The genetic basis of myotonic dystrophy type I (DM1) is the expansion of a CTG tract located in the 3′ untranslated region of DMPK. Expression of mutant RNAs encoding expanded CUG repeats plays a central role in the development of cardiac disease in DM1. Expanded CUG tracts form both nuclear and cytoplasmic aggregates, yet the relative significance of such aggregates in eliciting DM1 pathology is unclear. To test the pathophysiology of CUG repeat encoding RNAs, we developed and analyzed mice with cardiac-specific expression of a beta-galactosidase cassette in which a (CTG)400 repeat tract was positioned 3′ of the termination codon and 5′ of the bovine growth hormone polyadenylation signal. In these animals CUG aggregates form exclusively in the cytoplasm of cardiac cells. A key pathological consequence of expanded CUG repeat RNA expression in DM1 is aberrant RNA splicing. Abnormal splicing results from the functional inactivation of MBNL1, which is hypothesized to occur due to MBNL1 sequestration in CUG foci or from elevated levels of CUG-BP1. We therefore tested the ability of cytoplasmic CUG foci to elicit these changes. Aggregation of CUG RNAs within the cytoplasm results both in Mbnl1 sequestration and in approximately a two fold increase in both nuclear and cytoplasmic Cug-bp1 levels. Significantly, despite these changes RNA splice defects were not observed and functional analysis revealed only subtle cardiac dysfunction, characterized by conduction defects that primarily manifest under anesthesia. Using a human myoblast culture system we show that this transgene, when expressed at similar levels to a second transgene, which encodes expanded CTG tracts and facilitates both nuclear focus formation and aberrant splicing, does not elicit aberrant splicing. Thus the lack of toxicity of cytoplasmic CUG foci does not appear to be a consequence of low expression levels. Our results therefore demonstrate that the cellular location of CUG RNA aggregates is an important variable that influences toxicity and support the hypothesis that small molecules that increase the rate of transport of the mutant DMPK RNA from the nucleus into the cytoplasm may significantly improve DM1 pathology.

Original languageEnglish (US)
Article numbere3968
JournalPLoS One
Volume3
Issue number12
DOIs
StatePublished - Dec 18 2008

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RNA
cell aggregates
Cytoplasm
cytoplasm
Transgenes
Pathology
transgenes
Toxicity
RNA splicing
toxicity
RNA Splicing
mutants
Myotonic Dystrophy
Polyadenylation
myoblasts
Terminator Codon
stop codon
Myoblasts
heart diseases
Functional analysis

ASJC Scopus subject areas

  • Agricultural and Biological Sciences(all)
  • Biochemistry, Genetics and Molecular Biology(all)
  • Medicine(all)

Cite this

Dansithong, W., Wolf, C. M., Sarkar, P., Paul, S., Chiang, A., Holt, I., ... Reddy, S. (2008). Cytoplasmic CUG RNA foci are insufficient to elicit key DM1 features. PLoS One, 3(12), [e3968]. https://doi.org/10.1371/journal.pone.0003968

Cytoplasmic CUG RNA foci are insufficient to elicit key DM1 features. / Dansithong, Warunee; Wolf, Cordula M.; Sarkar, Partha; Paul, Sharan; Chiang, Andy; Holt, Ian; Morris, Glenn E.; Branco, Dorothy; Sherwood, Megan C.; Comai, Lucio; Berul, Charles I.; Reddy, Sita.

In: PLoS One, Vol. 3, No. 12, e3968, 18.12.2008.

Research output: Contribution to journalArticle

Dansithong, W, Wolf, CM, Sarkar, P, Paul, S, Chiang, A, Holt, I, Morris, GE, Branco, D, Sherwood, MC, Comai, L, Berul, CI & Reddy, S 2008, 'Cytoplasmic CUG RNA foci are insufficient to elicit key DM1 features', PLoS One, vol. 3, no. 12, e3968. https://doi.org/10.1371/journal.pone.0003968
Dansithong, Warunee ; Wolf, Cordula M. ; Sarkar, Partha ; Paul, Sharan ; Chiang, Andy ; Holt, Ian ; Morris, Glenn E. ; Branco, Dorothy ; Sherwood, Megan C. ; Comai, Lucio ; Berul, Charles I. ; Reddy, Sita. / Cytoplasmic CUG RNA foci are insufficient to elicit key DM1 features. In: PLoS One. 2008 ; Vol. 3, No. 12.
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