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Normal Function
The KRT12 gene provides instructions for making a protein called keratin 12. 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 12 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 12 protein partners with another keratin protein, keratin 3, to form molecules known as intermediate filaments. These filaments assemble into strong networks that provide strength and resilience to the corneal epithelium.
Health Conditions Related to Genetic Changes
Meesmann corneal dystrophy
At least 20 mutations in the KRT12 gene have been found to cause Meesmann corneal dystrophy, an eye disease characterized by the formation of tiny cysts in the corneal epithelium.
Almost all of the KRT12 gene mutations associated with Meesmann corneal dystrophy change single protein building blocks (amino acids) in the keratin 12 protein. These changes occur in regions of the protein that are critical for the formation and stability of intermediate filaments. The altered keratin 12 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.
More About This Health ConditionOther Names for This Gene
- CK-12
- cytokeratin-12
- K12
- K1C12_HUMAN
- keratin 12, type I
- keratin, type I cytoskeletal 12
- keratin-12
Additional Information & Resources
Tests Listed in the Genetic Testing Registry
Scientific Articles on PubMed
Catalog of Genes and Diseases from OMIM
References
- Corden LD, Swensson O, Swensson B, Smith FJ, Rochels R, Uitto J, McLEAN WH. Molecular genetics of Meesmann's corneal dystrophy: ancestral and novel mutations in keratin 12 (K12) and complete sequence of the human KRT12 gene. Exp Eye Res. 2000 Jan;70(1):41-9. doi: 10.1006/exer.1999.0769. Citation on PubMed
- Irvine AD, Corden LD, Swensson O, Swensson B, Moore JE, Frazer DG, Smith FJ, Knowlton RG, Christophers E, Rochels R, Uitto J, McLean WH. Mutations in cornea-specific keratin K3 or K12 genes cause Meesmann's corneal dystrophy. Nat Genet. 1997 Jun;16(2):184-7. doi: 10.1038/ng0697-184. Citation on PubMed
- Nishida K, Adachi W, Shimizu-Matsumoto A, Kinoshita S, Mizuno K, Matsubara K, Okubo K. A gene expression profile of human corneal epithelium and the isolation of human keratin 12 cDNA. Invest Ophthalmol Vis Sci. 1996 Aug;37(9):1800-9. Citation on PubMed
- Nishida K, Honma Y, Dota A, Kawasaki S, Adachi W, Nakamura T, Quantock AJ, Hosotani H, Yamamoto S, Okada M, Shimomura Y, Kinoshita S. Isolation and chromosomal localization of a cornea-specific human keratin 12 gene and detection of four mutations in Meesmann corneal epithelial dystrophy. Am J Hum Genet. 1997 Dec;61(6):1268-75. doi: 10.1086/301650. Citation on PubMed or Free article on PubMed Central
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