Characteristics of myotonic dystrophy in Istria: Molecular genetics approach - Mutation analysis

Myotonic dystrophy (DM) is the most prevalent myopathy in adults. In Istria one of the highest prevalence rates of 18/100 000 has been reported. Two L oci, the most prevalent 19q Locus with mutations in the myotonin, protein k inase gene and the second Locus mapped to the 3q have been so far implicate d in DM. The purpose of this study was to evaluate the molecular pathogenes is in the Istrian population by the analysis of (CTG) expansion in myotonin protein kinase gene. Additionally genotype - phenotype correlation was ana lysed as well as the transmission of expanded trinucleotides through genera tions. We investigated 27 DM patients from the 10 families that were ascert ained in Istria in our previous epidemiological study. Southern blot and po lymerase chain reaction (PCR) techniques were used to evaluate the (CTG) ex pansion. In 9 of the 10 DM families an amplificaton was identified as the m echanism of mutation. A correlation between the size of the (CTG) expansion and phenotype was found. Among 10 parent-child transmission analysed, one reduction, 2 stable transmissions and 7 amplifications were observed, one t hrough the affected father. The amplificaton of (CTG) in the myotonin protein kinase gene was identifie d in the majority of Istrian DM families. Direct mutation analysis is the m ethod of choice for clinical and prenatal diagnosis of DM.