title: Instability in the transmission of the myotonic dystrophy CTG repeat in human oocytes and preimplantation embryos.
abstract: OBJECTIVE
  To elucidate the timing and variability of CTG repeat expansion within the human dystrophia myotonica protein kinase (DMPK) gene in early development.
  
  
  METHODS
  Triplet-primed polymerase chain reaction was used to amplify the expanded CTG repeat in oocytes and embryos obtained from myotonic dystrophy 1 (DM1) patients, and a heminested polymerase chain reaction approach was used to amplify the normal CTG repeats in supernumerary IVF embryos.
  
  
  METHODS
  University hospital laboratory.
  
  
  METHODS
  Two DM1-affected females undergoing preimplantation genetic diagnosis who carried different CTG repeats. Also, 61 IVF patients who carried a (CTG)(5-18) and (CTG)(19-37) normal DMPK repeat.
  
  
  METHODS
  None.
  
  
  METHODS
  The degree of expansion of the repeat in the oocytes and embryos compared with the DM1-affected maternal repeat and the size of the (CTG)(19-37) repeat compared with the parental size in IVF embryos.
  
  
  RESULTS
  The degree of repeat expansion was greater than the DM1 maternal lymphocyte for two of four oocytes, including a germinal vesicle-stage oocyte and 17 of 20 three-cell to blastocyst stage embryos. A change in the (CTG)(19-37) repeat was seen in 7 (7%) of 95 paternal transmissions but in no maternal transmissions.
  
  
  CONCLUSIONS
  Because the repeat was already expanded in the immature oocyte, the initial expansion most likely occurs during oogenesis. A variable degree of DMPK(CTG)(n) expansion in the embryo is seen from different mothers. In addition, instability in paternal transmission of normal-range (CTG)(19-37) repeats occurs at the level of the embryo.
authors.affiliation: Department of Obstetrics and Gynecology, McGill University, Montreal, Québec, Canada.
authors.forename: Nicola L
authors.initials: NL
authors.lastname: Dean
authors.forename: Seang Lin
authors.initials: SL
authors.lastname: Tan
authors.forename: Asangla
authors.initials: A
authors.lastname: Ao
mesh_terms: D000328:Adult; D001755:Blastocyst / Q000502:physiology*; D002478:Cells, Cultured; D002874:Chromosome Mapping; D004252:DNA Mutational Analysis; D005260:Female; D020022:Genetic Predisposition to Disease / Q000235:genetics; D014644:Genetic Variation / Q000235:genetics; D042822:Genomic Instability / Q000235:genetics; D006801:Humans; D009136:Muscular Dystrophies / Q000151:congenital* / Q000235:genetics*; D065636:Myotonin-Protein Kinase; D009865:Oocytes / Q000502:physiology*; D011247:Pregnancy; D011296:Prenatal Diagnosis; D017346:Protein Serine-Threonine Kinases / Q000235:genetics*; D019680:Trinucleotide Repeat Expansion / Q000235:genetics*
chemical_list: C585517:DMPK protein, human; D065636:Myotonin-Protein Kinase; D017346:Protein Serine-Threonine Kinases