Characterization of the myotonic dystrophy region predicts multiple protein isoform-encoding mRNAs.

The mutation underlying myotonic dystrophy (DM) has been identified as an expansion of a polymorphic CTG-repeat in a gene encoding protein kinase activity.
Brain and heart transcripts of the DM-kinase (DMR-B15) gene are subject to alternative RNA splicing in both human and mouse.
The unstable [CTG] 5-30 motif is found uniquely in humans, although the flanking nucleotides are also present in mouse.
Characterization of the DM region of both species reveals another active gene (DMR-N9) in close proximity to the kinase gene.
DMR-N9 transcripts, mainly expressed in brain and testis, possess a single, large open reading frame, but the function of its protein product is unknown.
Clinical manifestation of DM may be caused by the expanded CTG-repeat compromising the (alternative) expression of DM-kinase or DMR-N9 proteins.. 
