The SELENON gene (also called SEPN1) provides instructions for making a protein called selenoprotein N. This protein is part of a family of selenoproteins, which have several critical functions within the body. Selenoproteins are primarily involved in chemical reactions called oxidation-reduction reactions, which are essential for protecting cells from damage caused by unstable oxygen-containing molecules. Selenoprotein N is likely involved in protecting cells against oxidative stress. Oxidative stress occurs when unstable molecules called free radicals accumulate to levels that damage or kill cells.
The exact function of selenoprotein N is unknown. This protein is highly active in many tissues before birth and may be involved in the formation of muscle tissue (myogenesis). Selenoprotein N may also be important for normal muscle function after birth, although it is active at much lower levels in adult tissues. This protein contains a region that likely allows it to bind to calcium. This region is of interest because calcium plays an important role in triggering muscle contractions, which allow the body to move.
At least 17 mutations in the SELENON gene have been identified in people with the classic form of multiminicore disease. Many of these genetic changes lead to the production of an abnormally short version of selenoprotein N. Other mutations change single protein building blocks (amino acids) in critical regions of the protein. The effects of changes in the structure and function of selenoprotein N are unknown, and researchers are working to determine how these changes lead to muscle weakness and the other characteristic features of multiminicore disease.
Mutations in the SELENON gene are responsible for several other rare muscle disorders, including rigid spine muscular dystrophy and desmin-related myopathy with Mallory body-like inclusions. These conditions cause muscle weakness, particularly in the muscles of the trunk and neck. Affected individuals also have decreased muscle tone (hypotonia), abnormal curvature of the spine (scoliosis), and serious breathing problems. Because they have a similar pattern of signs and symptoms and are caused by mutations in the same gene, many researchers believe that these conditions are all part of a single syndrome with variable signs and symptoms. Together, muscle diseases caused by SELENON gene mutations are known as SELENON-related (or SEPN1-related) myopathy.
- selenoprotein N, 1