Colocalization of muscleblind with RNA foci is separable from mis-regulation of alternative splicing in myotonic dystrophy

Thai H. Ho, Rajesh S. Savkur, Michael G. Poulos, Michael A. Mancini, Maurice S. Swanson, Thomas A. Cooper

Research output: Contribution to journalArticle

146 Scopus citations

Abstract

Myotonic dystrophy type I (DM1), which is caused by a non-coding CTG-repeat expansion in the dystrophia myotonica-protein kinase (DMPK) gene, is an RNA-mediated disease. Expanded CUG repeats in transcripts of mutant DMPK form nuclear foci that recruit muscleblind-like (MBNL) proteins, a family of alternative splicing factors. Although transcripts of mutant DMPK and MBNL proteins accumulate in nuclear RNA foci, it is not clear whether foci formation is required for splicing mis-regulation. Here, we use a co-transfection strategy to show that both CUG and CAG repeats form RNA foci that colocalize with green fluorescent protein (GFP)-MBNL1 and endogenous MBNL1 However, only CUG repeats alter splicing of the two tested pre-mRNAs, cardiac troponin T (cTNT) and insulin receptor (IR). Using FRAP, we demonstrate that GFP-MBNL1 in CUG and CAG foci have similar half-times of recovery and fractions of immobile molecules, suggesting that GFP-MBNL1 is bound by both CUG and CAG repeats. We also find an immobile fraction of GFP-MBNL1 in DM1 fibroblasts and a similar rapid exchange in endogenous CUG RNA foci. Therefore, formation of RNA foci and disruption of MBNL1-regulated splicing are separable events.

Original languageEnglish (US)
Pages (from-to)2923-2933
Number of pages11
JournalJournal of cell science
Volume118
Issue number13
DOIs
StatePublished - Jul 1 2005
Externally publishedYes

Keywords

  • Alternative splicing
  • MBNL
  • Muscleblind
  • Myotonic dystrophy

ASJC Scopus subject areas

  • Cell Biology

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