Improved method for molecular diagnosis of myotonic dystrophy type 1 (DM1).

Myotonic dystrophy type 1 (DM1) has been identified as the amplification of a polymorphic (CTG)n repeat in the 3' untranslated region of a gene encoding a serine/threonine kinase (DMPK). The length of the CTG repeat correlates with clinical severity and the age at onset of the disease. Thus, the ability to perform quick and accurate molecular genetic diagnoses is of great importance to patients and their families. Polymerase chain reaction (PCR) and Southern blots are essential methods for such diagnoses. All previously published methods are based on Southern blots using radioactive probes. Furthermore, the enzymes used for DNA digestion result in larger fragments, which makes it difficult to accurately determine the insert sizes. In this study, we report an improved method for molecular diagnosis of DM1. This method employs an initial screening with PCR followed by Southern blots using nonradioactive probes and TaqI as the enzyme, and provides a much better resolution of the labeled bands.