Rezümékötet 2008. - vmtdk

É L Õ T E R M É S Z E T T U D O M Á N Y O K
IDENTIFICATION OF EXPANDED DMPK ALLELES
IN PATIENTS WITH MYOTONIC DYSTROPHY TYPE 1 WITH THE
USE OF TRIPLET-PRIMED PCR
Author: János RADVÁNSZKÝ 1 , Monika BATOVÁ 2 , Péter REŠKO 1 , Roland PÁLFFY 3 3 rd year of postgradual studies
Supervisor: Doc. RNDr. Lajos KÁDASI, PhD.1
Institution: 1 Comenius University, Faculty of Natural Sciences, Department of Molecular Biology, Bratislava, Slovak Republic
2 Comenius University, Faculty of Natural Sciences, Department of Microbiology and Virology, Bratislava, Slovak Republic
3 Comenius University, Faculty of Medicine, Institute of Pathophysiology, Bratislava, Slovak Republic
Myotonic dystrophy type 1 (DM1) is a neuromuscular disorder caused by a CTG trinucleotide expansion in the
Dystrophia Mytonica Protein Kinase gene (DMPK). This repeat is highly polymorphic both in healthy and in affected
individuals. Healthy alleles are in a range of 5 to 37 CTG repeats. The disease causing CTG expansion can vary from
50 to several thousand repeats in affected individuals. DNA testing is important for the diagnosis of this disease because
clinical discrimination is complicated by its late onset and frequently overlapping symptomatology with other neuromuscular
diseases. However unusual secondary structures of the expanded CTG repeat regions poses a challenge
for PCR based diagnostic methods. Our work describes a two-step procedure for detection of unstable alleles causing
myotonic dystrophy type 1. At first the repeat lengths are examined by standard PCR and those problematic samples,
were only one allele is detected (homozygous sample for this allele or heterozygous sample with one amplifiable and
one non-amplifiable, expanded allele) are further analysed by Triplet-Primed PCR (TP-PCR). CTG repeat length was
analysed in samples of 38 suspected patients and in 103 samples of healthy, unrelated individuals both by standard
PCR and by TP-PCR. Both types of these reactions were carried out with fluorescent labelled primers and the results
were analysed using fragment analysis in genetic analyser. Analysis of the repeat length in healthy samples showed trimodal
distribution with the majority of chromosomes belonging to the groups (CTG) 5 and (CTG) 9-17. Among samples
of suspected patients expanded allele was detected in 8 cases.
Keywords: CTG repeat, DM1, Dystrophia Mytonica Protein Kinase, myotonic dystrophy type 1, TP-PCR, trinucleotide
expansion, Triplet-Primed PCR
N Y O S D I Á K K Ö R I K O N F E R E N C I A
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