A recent study lead by researchers at the Genome Institute at Washington University School of Medicine in St. Louis and the University of Michigan School of Public Health in Ann Arbor identified a gene mutation that's linked to macular degeneration.

This gene variation could be the first to suggest a mechanism in which a variant may contribute to the disease. Researchers report the change in the C3 gene that plays a role in inflammation of the body's immune response.

"In past studies of AMD, there is a clear relationship between the complement pathway and the onset of this disease," co-senior investigator Elaine R. Mardis, PhD said, via a press release. "The complement system is part of the immune system that helps amplify or 'complement' the efforts of immune cells to fight infections. So the idea is that the gene variant interferes with the complement pathway's normal function throughout life, and that can damage the retina over time, which ultimately leads to AMD's emergence."

The researchers examined DNA from 10 regions of the genome that had previously been linked to AMD in various genetic studies. They then analyzed a total of 57 genes from 2,335 patients with macular degeneration. The researchers sequenced the same genes in 789 people the same age who did not have AMD.

Background information from the study notes that the search turned up two gene variants, including the following: one in C3 complete gene and an alteration that had been identified in previous studies of the health issue.

"Finding the variant that had been identified previously helped confirm that we were on the right track," explained Mardis, a professor of genetics and co-director of the Genome Institute, via the release. "And it's likely this new variant was discovered because of the very large number of patients whose DNA we sequenced. By analyzing so many AMD patients, it was possible to find variants that may not have been identified in a smaller patient sample and to establish that this C3 gene variant is unique to people with AMD."

Results show that these two gene variants help contribute to a three-fold increased risk for macular degeneration.

"When you have these mutations, interactions between the proteins that cascade in the complement pathway are altered," Mardis said. "And when they're altered, the secondary response to infection, which involves complement, also is altered. So our hypothesis is that over time, because of the role of the complement pathway in the retina, damage begins to accrue, and eventually that leads to vision loss."

Researchers hope that by looking at different DNA regions in the participants, this could possibly help uncover more about the disease.

Sources:

1. Science World Report:
   Macular Degeneration.