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| What Role Does Genetics Play? |
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It is becoming more evident that many eye diseases have a genetic component to their development. - In 1997, the first genetic mutations to be associated with age-related macular degeneration (AMD) were reported. This identified gene was the ABCR gene, which codes for a retinal binding protein.
Subsequently a number of other genes were reported to be associated with AMD including the apolipoprotein E (ApoE) gene, ACE gene (angiotensin converting enzyme), hemicentin-1 (fibulin 6) gene, and the ELOVL4 (elongation of very long chain fatty acid-like 4) gene but these accounted for only a relatively small percentage of AMD patients.
However, in 2005 a nucleotide substitution in the complement factor H (CFH) gene was reported to be associated with nearly 50% of AMD patients. CFH is part of the alternate complement pathway and is an inhibitor for complement activation. The CFH plasma levels decline with smoking and aging, both risk factors for AMD. These lower CFH levels are associated with increased inflammation which is found to be present in AMD retinas. To date at least 3-4 additional genes have been reported to be associated with AMD. In addition, studies are now investigating the possible involvement of mitochondrial DNA in the development and progression of AMD. Other eye diseases such as glaucoma, Leber’s hereditary optic neuropathy, keratoconus, congenital eye defects and lattice corneal dystrophy are associated with alterations in specific genes. Identifying the gene defects allows for greater understanding of the disease process and will help to guide future therapies. |