title: The CTG repeat expansion size correlates with the splicing defects observed in muscles from myotonic dystrophy type 1 patients.
abstract: BACKGROUND
  Myotonic dystrophy type 1 is caused by an unstable (CTG)n repetition located in the 3'UTR of the DM protein kinase gene (DMPK). Untranslated expanded DMPK transcripts are retained in ribonuclear foci which sequester CUG-binding proteins essential for the maturation of pre-mRNAs.
  
  
  OBJECTIVE
  To investigate the effects of CTG expansion length on three molecular parameters associated with the DM1 muscle pathology: (1) the expression level of the DMPK gene; (2) the degree of splicing misregulation; and (3) the number of ribonuclear foci.
  
  
  METHODS
  Splicing analysis of the IR, MBNL1, c-TNT and CLCN1 genes, RNA-FISH experiments and determination of the DMPK expression on muscle samples from DM1 patients with an expansion below 500 repetitions (n = 6), DM1 patients carrying a mutation above 1000 CTGs (n = 6), and from controls (n = 6).
  
  
  RESULTS
  The level of aberrant splicing of the IR, MBNL1, c-TNT and CLCN1 genes is different between the two groups of DM1 muscle samples and correlates with the CTG repeat length. RNA-FISH analysis revealed that the number of ribonuclear foci in DM1 muscle sections increases in patients with a higher (CTG)n number. No relationships were found between the expression level of the DMPK gene transcript and average expansion sizes.
  
  
  CONCLUSIONS
  The CTG repeat length plays a key role in the extent of splicing misregulation and foci formation, thus providing a useful link between the genotype and the molecular cellular phenotype in DM1.
authors.affiliation: Tor Vergata University of Rome, Department of Biopathology, Via Montpellier, 1, 00133 Rome, Italy. abottait@yahoo.it
authors.forename: A
authors.initials: A
authors.lastname: Botta
authors.forename: F
authors.initials: F
authors.lastname: Rinaldi
authors.forename: C
authors.initials: C
authors.lastname: Catalli
authors.forename: L
authors.initials: L
authors.lastname: Vergani
authors.forename: E
authors.initials: E
authors.lastname: Bonifazi
authors.forename: V
authors.initials: V
authors.lastname: Romeo
authors.forename: E
authors.initials: E
authors.lastname: Loro
authors.forename: A
authors.initials: A
authors.lastname: Viola
authors.forename: C
authors.initials: C
authors.lastname: Angelini
authors.forename: G
authors.initials: G
authors.lastname: Novelli
mesh_terms: D000293:Adolescent; D000328:Adult; D005091:Exons; D015870:Gene Expression; D006801:Humans; D017404:In Situ Hybridization, Fluorescence; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000378:metabolism*; D009223:Myotonic Dystrophy / Q000235:genetics*; D065636:Myotonin-Protein Kinase; D017346:Protein Serine-Threonine Kinases / Q000235:genetics* / Q000378:metabolism; D012313:RNA / Q000378:metabolism; D012326:RNA Splicing; D020133:Reverse Transcriptase Polymerase Chain Reaction; D019680:Trinucleotide Repeat Expansion
chemical_list: C585517:DMPK protein, human; D012313:RNA; D065636:Myotonin-Protein Kinase; D017346:Protein Serine-Threonine Kinases