Myotonic dystrophy type 2 (Myotonic dystrophy type 2) - Gen CNBP.
Myotonic dystrophy is a group of inherited disorders called muscular dystrophies. Myotonic dystrophy is the most common form of muscular dystrophy that begins in adulthood and is characterized by progressive muscle weakness. Often, those affected have myotonia and are not able to relax certain muscles after use. In addition, affected individuals may have difficulty speaking.
Other signs and symptoms of myotonic dystrophy include cataracts, cardiac conduction defects and premature baldness and infertility in males. Often these features are developed around 20 and 30 years of age, but can occur at any age. The severity of the disease varies widely among affected individuals, even among members of the same family. Signs and symptoms of myotonic dystrophy type 2 tend to be milder than type 1. Muscle weakness in type 2 primarily involves the muscles of the neck, shoulders, elbows and hips.
Type 2 myotonic dystrophy is due to mutations in the gene CNBP, located on the long arm of chromosome 3 (3q21). This gene encodes a protein of CCHC type zinc bound called binding protein nucleic acid. This protein contains seven regions (domains zinc), which is likely to be attached to specific sites on DNA and RNA. The CNBP protein is found in many tissues of the body, but is most abundant in the heart and skeletal muscles. Although the exact function of this protein is unclear, it appears to regulate the activity of other genes. This protein is required for normal embryonic development. A region of the gene contains a segment CNBP four nucleotides is repeated several times. This sequence (CCTG) is called tetranucleotide repeat. In most people, the CCTG sequence is repeated less than 26 times.
Mutations in the gene increase CNBP size CCTG repeated in the gene segment. People with myotonic dystrophy type 2 have 75 to over 11,000 reps CCTG. The mutated gene encodes CNBP an altered version of the messenger RNA, protein synthesis directing. It has been found that proteins synthesized under the direction of altered messenger RNA molecules form lumps inside the cell and interfere with the encoding of many other proteins. These changes prevent muscle cells and cells in other tissues function properly, leading to muscle weakness and other characteristics of myotonic dystrophy type 2.
Myotonic dystrophy type 2 is inherited as an autosomal dominant, which means that a copy of the altered gene in each cell is sufficient for the disease to be expressed. In most cases, an affected person has a parent with the disorder.
Tests in IVAMI: in IVAMI perform detection of mutations associated with myotonic dystrophy type 2, by complete PCR amplification of exons CNBP gene, and subsequent sequencing.
Samples recommended: EDTA blood collected for separation of blood leukocytes, or impregnated sample card with dried blood (IVAMI may mail the card to deposit the blood sample).