The myotonic dystrophy gene
A. Pizzuti, D. L. Friedman and C. T. Caskey
Institute for Molecular Genetics, Baylor College of Medicine, Houston, Tex.
The myotonic dystrophy gene codes for a protein kinase and contains a
repeated trinucleotide motif (adenine-guanine-cytosine [AGC]) in its
transcribed sequence. The repeat is polymorphic in the general population,
varying in size from five to 37 AGC units in normal alleles. Myotonic
dystrophy patients show expansions of the repeated sequence from over 50
elements up to several thousand units. There is a positive correlation
between repeat size and clinical severity. The direct analysis of the AGC
repeat size allows an easy confirmation of the clinical diagnosis of
myotonic dystrophy in difficult cases and for prenatal counseling.
