New insights into the etiology of age-related macular degeneration by a large genetic study

Age-related macular degeneration is a leading cause of blindness and severe disability that affects ten million older individuals worldwide. Therapy options are limited as currently therapy is only available for patients with one of the two disease subtypes, the so-called wet AMD, and even this therapy is symptomatic and no cure.

Unfortunately, it is not well understood by doctors or scientists why some people develop the disease while others remain disease-free. A major portion of the risk for AMD is the combination of genetic variants a person possesses; other risk factors include smoking or intensive light exposure. Finding the exact combination of genetic variants that puts people at risk for AMD is a difficult task that requires evaluating information from many thousands of individuals.

To get at the goal of better understanding the genetic influence of AMD risk, an international group of scientists from 26 study sites, including scientists from the University of Regensburg, joined forces to create and evaluate an extensive genome-wide data set that provided an excellent platform for a thorough search for gene regions that may influence AMD risk.

Using medical information and DNA from blood collected from more than 43,000 participants with and without AMD across the world, this group applied novel methods, that enabled the investigation of 12 million genetic variants. Not only did they find 34 gene regions for AMD including 16 that have not been described before. The new regions provide new clues to search for cures for this severe medical condition.

Most interestingly, this international group also identified a genetic region around the MMP9 gene that showed only an effect for the wet AMD, but not for dry AMD. This new knowledge might lead to a better understanding of why the therapy is more effective in some patients than in others.

The genetic make-up of a patient might also help explain why some treated patients suffer from a recurrence: To some extent this might be simply that the genetics hits again.

The investigators also had a specific focus on rare variants that alter the protein. If such a variant is found to be relevant for the disease, the mechanisms by what this variant exerts its effect is much easier to derive than for other variants: the specific change in the protein itself is then very likely the cause. While several such variants for AMD were depicted by this study, the study made also clear that these variants can be very rare and hard to depict.

This work also substantiates a strong role of the University of Regensburg. Researchers from the UR Institute of Human Genetics and the Department of Genetic Epidemiology have not only contributed study data, but also helped organize the international consortium (Prof. Weber) and co-lead and conducted (Prof. Heid and team) the analysis of this complex and high-dimensional data.

Overall, the results published in Nature Genetics (NG-A41068R2) help understand what makes individuals susceptible to the disease, which patients might benefit from a particular form of treatment, and what might be worthwhile next steps towards a cure that would be the hope of millions of patients (www.nature.com/ng/journal/v45/n4/full/ng.2578.html ).

Contact:
Prof. Dr. Iris Heid
Universität Regensburg
Chair for Genetic Epidemiology
Tel.: +49 (0)941 944-5210/5211
Iris.Heid@klinik.uni-regensburg.de