MYO15A

The MYO15A gene provides instructions for making a protein called myosin XVA, which is part of a group of proteins called unconventional myosins. These proteins, which have similar structures, each play a role in transporting molecules within cells. Myosins interact with actin, a protein that is important for cell movement and shape. Researchers believe that myosins use long filaments of actin as tracks along which to transport other molecules.

Myosin XVA is made in the inner ear, the pituitary gland (a structure at the base of the brain that makes several hormones), and other tissues. It appears to be essential for normal hearing. In the inner ear, myosin XVA plays a role in the development and maintenance of hairlike projections called stereocilia. Stereocilia, which are rich in actin, line the inner ear and bend in response to sound waves. This bending motion is critical for converting sound waves to nerve impulses.

One function of myosin XVA is to carry a protein called whirlin to its normal location at the tips of stereocilia. Both proteins are essential for building these structures.

nonsyndromic deafness - caused by mutations in the MYO15A gene

At least seven mutations in the MYO15A gene have been identified in families with a form of nonsyndromic deafness (hearing loss without related signs and symptoms affecting other parts of the body) called DFNB3. Most of these genetic changes alter a single protein building block (amino acid) in critical regions of the myosin XVA protein. MYO15A mutations disrupt the usual function of myosin XVA or cause an abnormally short, nonfunctional version of the protein to be made. Altering the function of myosin XVA disrupts the structure and organization of stereocilia, leading to hearing loss.