CNBP

The CNBP gene (also known as ZNF9) provides instructions for making a protein called CCHC-type zinc finger, nucleic acid binding protein. This protein has seven regions, called zinc finger domains, which are thought to attach (bind) to specific sites on DNA and its chemical cousin, RNA.

The CNBP protein is found in many of the body's tissues, but it is most abundant in the heart and in muscles used for movement (skeletal muscles). Although the exact function of this protein is unclear, it appears to regulate the activity of other genes. The CNBP protein is necessary for normal embryonic development.

One region of the CNBP gene contains a segment of four DNA building blocks (nucleotides) that is repeated multiple times. This sequence, which is written as CCTG, is called a tetranucleotide repeat. In most people, the CCTG sequence is repeated fewer than 26 times.

myotonic dystrophy - caused by mutations in the CNBP gene

Type 2 myotonic dystrophy results from a mutation in the CNBP gene known as a tetranucleotide repeat expansion. This mutation increases the size of the repeated CCTG segment in the CNBP gene. People with type 2 myotonic dystrophy have from 75 to more than 11,000 CCTG repeats.

The mutated CNBP gene produces an altered version of messenger RNA, which is a molecular blueprint of the gene that is normally used to guide the production of proteins. Researchers have found that the altered messenger RNA traps proteins to form clumps within the cell. The clumps interfere with the production of many other proteins. These changes prevent muscle cells and cells in other tissues from functioning properly, leading to muscle weakness and the other features of type 2 myotonic dystrophy.