A second gene, called fibulin 5, has been shown to be related to age-related macular degeneration (AMD). The discovery was announced in the July 22, 2004 issue of the New England Journal of Medicine by a team from the Research Center for Macular Degeneration and Allied Retinal Diseases at the University of Iowa. Earlier research led to the first discovery of an AMD-related gene called hemicentin-1 (see www.mdsupport.org/library/amdgene.html.)
The fibulin 5 gene is involved in the production of the protein elastin, which helps form elastic fibers found in Bruch's membrane. This membrane separates the blood vessels in the choroid layer of the retina from the retinal pigment epithelium, or RPE (see Anatomy of the Eye for graphics). The researchers believe that a reduced amount of elastin caused by the defective gene may lead to the formation of drusen, a precursor of AMD.
After comparing the DNA of 402 AMD patients with an equal-sized control group of people with healthy retinas, the UI team found mutations of the fibulin 5 genes in seven of the AMD patients. That is a statistically significant number that calls for more study, and we will continue to stay updated on further developments.