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 heat transcripts of the DM-kinase (DMR-B15) gene are subject to alternative RNA splicing in both human and mouse. The unstable (CTG) sub(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 is unknown.