ZNF9: A gene that encodes a protein called zinc finger protein 9. An inherited mutation in ZNF9 causes type 2 myotonic dystrophy. One region of the ZNF9 gene has a particular 4-base-pair sequence, CCTG, that is normally repeated a few times. (Base pairs are the building blocks of DNA.) This region is called a tetranucleotide repeat. The inherited mutation in the ZNF9 gene that causes type 2 myotonic dystrophy is an abnormally large segment made up of the four repeated DNA base pairs (CCTG). This expanded tetranucleotide repeat is copied from 75 to more than 11,000 times in people who have the disease, with an average of about 5,000 repeats.
Messenger RNA from the altered ZNF9 gene can interact with certain proteins to form clumps in the nucleus of the cell. The altered messenger RNA is thought to disrupt the ability to make the ZNF9 protein and the proteins of other genes. This disruption prevents cells from functioning normally, leading to the signs and symptoms of type 2 myotonic dystrophy.
The protein made by ZNF9 has seven areas, called zinc finger domains, which are thought to bind to specific sites on messenger RNA (a molecule similar to DNA that carries information for making proteins). Zinc finger protein 9 plays a role in regulating genes involved in the production and use of cholesterol. The protein is found in many of the body's tissues, but is most abundant in heart and skeletal muscle.