The KRT3 gene provides instructions for making a protein called keratin 3. Keratins are a group of tough, fibrous proteins that form the structural framework of epithelial cells, which are cells that line the surfaces and cavities of the body. Keratin 3 is produced in a tissue on the surface of the eye called the corneal epithelium. This tissue forms the outermost layer of the cornea, which is the clear front covering of the eye. The corneal epithelium acts as a barrier to help prevent foreign materials, such as dust and bacteria, from entering the eye.
The keratin 3 protein partners with another keratin protein, keratin 12, to form molecules known as intermediate filaments. These filaments assemble into strong networks that provide strength and resilience to the corneal epithelium.
At least three mutations in the KRT3 gene have been found to cause Meesmann corneal dystrophy, an eye disease characterized by the formation of tiny cysts in the corneal epithelium.
All of the identified KRT3 gene mutations associated with Meesmann corneal dystrophy change single protein building blocks (amino acids) in the keratin 3 protein. These changes occur in a region of the protein that is critical for the formation and stability of intermediate filaments. The altered keratin 3 protein interferes with the assembly of intermediate filaments, weakening the structural framework of the corneal epithelium. As a result, this outer layer of the cornea is abnormally fragile and develops the cysts that characterize Meesmann corneal dystrophy. The cysts likely contain clumps of abnormal keratin proteins and other cellular debris. When the cysts break open (rupture), they cause eye irritation, increased sensitivity to light (photophobia), and related symptoms.
- 65 kDa cytokeratin
- cytokeratin 3
- keratin 3, type II
- keratin, type II cytoskeletal 3
- type-II keratin Kb3