Somatic cell heterogeneity between DNA extracted from lymphocytes and skeletal muscle in congenital myotonic...

Myotonic dystrophy (DM) results from the expansion of an unstable CTG trinucleotide repeat in the 3' untranslated region of mRNA encoding a putative serine/threonine protein kinase. The degree of the CTG repeat amplification in genomic DNAs extracted from lymphocytes correlates with disease severity. We have analyzed the amplification of the CTG repeat of DNAs extracted from skeletal muscles and lymphocytes in five congenital DM patients. The amplification from skeletal muscles showed an increase of about 1.5 kb to 3.5 kb larger than that from lymphocytes in all patients. Furthermore, we have investigated the somatic instability of the CTG repeat in various tissues from a severe congenital DM patient.