Researchers at the University of Minnesota showed that myotonic dystrophy, known formally as dystrophia myotonica (DM), derives primarily from a mutation in untranslated RNA.1 Their finding, which concerns DM type 2, corroborates evidence of a decade earlier that DM1 is similarly caused.2 The two mutations, which occur on chromosomes 19 and 3, respectively, both result in the multisystemic signs and symptoms that characterize myotonic dystrophy. Moreover, both mutations are repeat expansions-nucleotide sequences that recur adjacently many more times than normal. A third type of DM is thought to exist, but it has not been identified.
"I think this will be considered the major pathogenic mechanism for DM," asserts Laura P.W. Ranum, the DM2 paper's senior author and a University of Minnesota associate professor of genetics, cell biology, and development. The paper points out that untranslated repeat expansions also are involved in two types of spinocerebellar ataxia, SCA8 and SCA10. However, ...
