What are the genetic changes related to myotonic dystrophy ?
Myotonic dystrophy type 1 is caused by mutations in the DMPK gene, while type 2 results from mutations in the CNBP gene. The specific functions of these genes are unclear. The protein produced from the DMPK gene may play a role in communication within cells. It appears to be important for the correct functioning of cells in the heart, brain, and skeletal muscles (which are used for movement). The protein produced from the CNBP gene is found primarily in the heart and in skeletal muscles, where it probably helps regulate the function of other genes.  Similar changes in the structure of the DMPK and CNBP genes cause the two forms of myotonic dystrophy. In each case, a segment of DNA is abnormally repeated many times, forming an unstable region in the gene. The mutated gene produces an expanded version of messenger RNA, which is a molecular blueprint of the gene that is normally used to guide the production of proteins. The abnormally long messenger RNA forms clumps inside the cell that interfere with the production of many other proteins. These changes prevent muscle cells and cells in other tissues from functioning normally, which leads to the signs and symptoms of myotonic dystrophy.