|http://ghr.nlm.nih.gov/ A service of the U.S. National Library of Medicine®|
The official name of this gene is “dystrophin.”
DMD is the gene's official symbol. The DMD gene is also known by other names, listed below.
DMD, the largest known human gene, provides instructions for making a protein called dystrophin. This protein is located primarily in muscles used for movement (skeletal muscles) and in heart (cardiac) muscle. Small amounts of dystrophin are present in nerve cells in the brain.
In skeletal and cardiac muscles, dystrophin is part of a group of proteins (a protein complex) that work together to strengthen muscle fibers and protect them from injury as muscles contract and relax. The dystrophin complex acts as an anchor, connecting each muscle cell's structural framework (cytoskeleton) with the lattice of proteins and other molecules outside the cell (extracellular matrix). The dystrophin complex may also play a role in cell signaling by interacting with proteins that send and receive chemical signals.
Little is known about the function of dystrophin in nerve cells. Research suggests that the protein is important for the normal structure and function of synapses, which are specialized connections between nerve cells where cell-to-cell communication occurs.
At least 18 mutations in the DMD gene can cause a form of heart disease called DMD-associated dilated cardiomyopathy. This condition enlarges and weakens the cardiac muscle, preventing the heart from pumping blood efficiently. Although dilated cardiomyopathy is a sign of Duchenne and Becker muscular dystrophies (described below), DMD-associated dilated cardiomyopathy is typically not associated with weakness and wasting of skeletal muscles.
The mutations that cause DMD-associated dilated cardiomyopathy preferentially affect the activity of dystrophin in cardiac muscle cells. As a result of these mutations, affected individuals typically have little or no functional dystrophin in the heart. Without enough of this protein, cardiac muscle cells become damaged as the heart muscle repeatedly contracts and relaxes. The damaged muscle cells weaken and die over time, leading to the heart problems characteristic of DMD-associated dilated cardiomyopathy.
The mutations that cause DMD-associated dilated cardiomyopathy often lead to reduced amounts of dystrophin in skeletal muscle cells. However, enough of this protein is present to prevent weakness and wasting of the skeletal muscles.
More than 1,000 mutations in the DMD gene have been identified in people with the Duchenne and Becker forms of muscular dystrophy. These conditions occur almost exclusively in males and are characterized by progressive muscle weakness and wasting (atrophy). Most of the mutations that cause these conditions delete part of the DMD gene. Other mutations abnormally duplicate part of the gene or change a small number of DNA building blocks (nucleotides) in the gene.
Mutations that cause Becker muscular dystrophy, which typically has milder features and appears at a later age than Duchenne muscular dystrophy, usually lead to an abnormal version of dystrophin that retains some function. Mutations that cause the more severe Duchenne muscular dystrophy typically prevent any functional dystrophin from being produced.
Skeletal and cardiac muscle cells without enough functional dystrophin become damaged as the muscles repeatedly contract and relax with use. The damaged cells weaken and die over time, causing the characteristic muscle weakness and heart problems seen in Duchenne and Becker muscular dystrophy.
Cytogenetic Location: Xp21.2
Molecular Location on the X chromosome: base pairs 31,119,218 to 33,339,608
The DMD gene is located on the short (p) arm of the X chromosome at position 21.2.
More precisely, the DMD gene is located from base pair 31,119,218 to base pair 33,339,608 on the X chromosome.
See How do geneticists indicate the location of a gene? (http://ghr.nlm.nih.gov/handbook/howgeneswork/genelocation) in the Handbook.
You and your healthcare professional may find the following resources about DMD helpful.
You may also be interested in these resources, which are designed for genetics professionals and researchers.
See How are genetic conditions and genes named? (http://ghr.nlm.nih.gov/handbook/mutationsanddisorders/naming) in the Handbook.
atrophy ; cardiac ; cardiomyopathy ; cell ; cytoskeleton ; dilated ; DNA ; extracellular ; extracellular matrix ; familial ; gene ; injury ; muscle cell ; muscle cells ; muscular dystrophy ; protein ; sign ; skeletal muscle ; wasting
You may find definitions for these and many other terms in the Genetics Home Reference Glossary.
The resources on this site should not be used as a substitute for professional medical care or advice. Users seeking information about a personal genetic disease, syndrome, or condition should consult with a qualified healthcare professional. See How can I find a genetics professional in my area? (http://ghr.nlm.nih.gov/handbook/consult/findingprofessional) in the Handbook.