In myotonic dystrophy type 1 (DM1), however, aberrant MAPT splicing has been documented at multiple exons—including exon 10 as well as exons 2/3 and 6—resulting in an altered 3R/4R ratio, often with a relative predominance of the 3R isoform. The gene discussed is MAPT; the disease is myotonic dystrophy type 1.