Researchers at the University of Minnesota have found that faulty proteins may not be the only culprits when it comes to some hereditary diseases. Their findings, published in the current issue of the journal Science, suggest that abnormal RNAthe molecule that translates the DNA code into proteinsmay cause myotonic dystrophy.

Laura P. W. Ranum and her colleagues investigated the causes of a form of myotonic dystrophy (DM) known as DM2, analyzing the clinical and genetic features of 71 individuals from 26 families that have the hereditary disease. Earlier research had indicated that mutations of genes on chromosomes 19q13 and 3q21 cause DM1 and DM2, respectively. Yet exactly how these mutations lead to disease has puzzled investigators because they occur in regions of the chromosomes that are transcribed into RNA but they do not code for proteins. The new work indicates that DM2 occurs when a mutation on chromosome 3q21 is transcribed into RNA. Then, instead of moving out into the cell where it would be translated into a protein, the RNA accumulates in the cell's nucleus, thus causing problems.

"In the past the focus has been on protein abnormalities as the cause of genetic disorders," Ranum remarks, noting that RNA was thought to have little or no role in the matter. The new findings alter that picture considerably. Says team member John Day, "for the first time, there is indisputable evidence that RNA itself can cause disease."