SNPwatch: AMD Linked to Yet Another Immune System Gene

Age-related macular degeneration (AMD) is the most common cause of irreversible vision loss in the western world among people over 60. The two forms of the disease — wet and dry — both cause vision loss by destroying cells in the central portion of the retina.

Genetic Associations

In the last few years, progress in understanding AMD has been made thanks in part to the discovery of several common genetic variants, or SNPs, that together explain a large part of the risk for the disease. Several of these recently discovered genetic associations have pointed to a role for the immune system in the disease.

A new study published online Monday in The Lancet yet again links the immune system to AMD. As is the case for several of the previously found SNPs, the variant found in this study is in a gene involved in the complement pathway, an arm of the immune system that facilitates the elimination of both pathogens and cellular debris.

Making a Connection

Many years ago some researchers suspected that the complement system might be involved in AMD. Proteins from this pathway were found in drusen, the small crystalline deposits that build up in the eyes of people with AMD. But it was not until genetic studies started to show a link between AMD and complement genes that other scientists began to sit up and take notice.

In two separate samples — one British with 479 AMD patients and 479 controls, the other from the U.S. with 248 cases and 252 controls — Ennis et al found that the odds of developing AMD were reduced for those with on variant in the SERPING1 gene, which encodes a protein that regulates the complement pathway.

“Our findings add to the growing understanding of the genetics of age-related macular degeneration, which should ultimately lead to novel treatments for this common and devastating disease,” the authors write.

In an accompanying comment in The Lancet, Caroline Klaver and Arthur Bergen, two scientists not associated with the research, said the results of Ennis et al need to be replicated in large, independent samples before SERPING1 will be established as a true risk factor for AMD. They also suggest that the researchers may find other SNPs within the gene that are even more tightly linked to AMD.