|http://ghr.nlm.nih.gov/ A service of the U.S. National Library of Medicine®|
The official name of this gene is “collagen, type VIII, alpha 2.”
COL8A2 is the gene's official symbol. The COL8A2 gene is also known by other names, listed below.
The COL8A2 gene provides instructions for making a component of type VIII collagen called alpha 2(VIII) collagen. Type VIII collagen is largely found within the front surface of the eye, called the cornea. Type VIII collagen is a major component of Descemet's membrane, which is a tissue at the back of the cornea. This membrane is a thin, sheet-like structure that separates and supports corneal endothelium cells. These cells regulate the amount of fluid inside the cornea. An appropriate fluid balance in the cornea is necessary for clear vision.
To construct type VIII collagen, one subunit of the alpha 2(VIII) collagen protein interacts with two subunits of another protein called alpha 1(VIII) collagen. These three proteins twist together to form a triple-stranded, rope-like molecule known as procollagen. Procollagen molecules are secreted by the cell and processed by enzymes to remove extra protein segments from the ends. Once these molecules are processed, they arrange themselves into long, thin bundles of mature type VIII collagen.
At least two mutations in the COL8A2 gene have been found to cause a variant of Fuchs endothelial dystrophy, an eye disorder characterized by progressively blurry vision and sensitivity to bright light. COL8A2 gene mutations are associated with the rare, early-onset variant of Fuchs endothelial dystrophy, in which vision problems typically begin in a person's twenties.
The COL8A2 gene mutations that cause the early-onset variant of Fuchs endothelial dystrophy replace single protein building blocks in alpha 2(VIII) collagen. One mutation replaces the amino acid leucine with the amino acid tryptophan at position 450 (written as Leu450Trp or L450W). Another mutation replaces the amino acid glutamine with the amino acid lysine at position 455 (Gln455Lys or Q455K). These mutations impair the structure of alpha 2(VIII) collagen, probably preventing the abnormal protein from being incorporated into type VIII collagen fibers. As a result, there is a reduced amount of type VIII collagen in the cornea, specifically in Descemet's membrane. This abnormal Descemet's membrane leads to the death of the corneal endothelial cells, causing the cornea to become swollen with fluid. Corneal endothelial cells continue to die over time, which causes the vision problems in people with the early-onset variant of Fuchs endothelial dystrophy.
Cytogenetic Location: 1p34.2
Molecular Location on chromosome 1: base pairs 36,560,839 to 36,591,304
The COL8A2 gene is located on the short (p) arm of chromosome 1 at position 34.2.
More precisely, the COL8A2 gene is located from base pair 36,560,839 to base pair 36,591,304 on chromosome 1.
See How do geneticists indicate the location of a gene? (http://ghr.nlm.nih.gov/handbook/howgeneswork/genelocation) in the Handbook.
You and your healthcare professional may find the following resources about COL8A2 helpful.
You may also be interested in these resources, which are designed for genetics professionals and researchers.
See How are genetic conditions and genes named? (http://ghr.nlm.nih.gov/handbook/mutationsanddisorders/naming) in the Handbook.
amino acid ; cell ; collagen ; cornea ; endothelial cells ; gene ; leucine ; molecule ; mutation ; protein ; sensitivity ; subunit ; tissue
You may find definitions for these and many other terms in the Genetics Home Reference Glossary (http://www.ghr.nlm.nih.gov/glossary).
The resources on this site should not be used as a substitute for professional medical care or advice. Users seeking information about a personal genetic disease, syndrome, or condition should consult with a qualified healthcare professional. See How can I find a genetics professional in my area? (http://ghr.nlm.nih.gov/handbook/consult/findingprofessional) in the Handbook.