Genetic Factors in Age-Related Macular Degeneration

Overview

This study will examine whether certain polymorphisms (small gene variances) predispose people to develop age-related macular degeneration (AMD). This eye condition affects people over 50 years of age and can cause permanent loss of central vision. The study will examine and compare the frequency of polymorphisms in patients with AMD to that of individuals without AMD. This information will help identify genetic risk factors for the AMD and may lead to the development of more effective treatments. Patients 50 years of age and older with advanced AMD and healthy normal volunteers may be eligible for this study. All participants will provide an eye health history and will have 10 milliliters (2 teaspoons) of blood drawn from an arm vein. The DNA in the blood will be isolated and tested for certain genes that other research indicates are important in aging and age-related diseases. The normal and polymorphic gene sequences will be identified and compared in patients with AMD and control subjects to determine if any of the polymorphisms are related to development of AMD. In addition, control subjects will have a routine eye examination, including dilation of the pupils for examination of the back of the eye. ...

Age-related macular degeneration (AMD) is the leading cause of irreversible severe central visual loss older than 50 in the world.1 The incidence and progression of all the features of AMD are known to increase significantly with age.2-4 In a recent study, Klein et al. reported that approximately 15.6% of the US population aged 60 years and older in 2005-2008 had signs of AMD.5 In a study in Iceland, the prevalence of early AMD was 12.4% for those aged 66 to 74 years and 36% for those aged 85 years and older.6 Currently in the United States, advanced AMD affects more than 1.75 million people and the number will increase to 2.95 million by the year 2020.7 Epidemiological studies of genome wide association study (GWAS), candidate gene association, and linkage disequilibrium suggest that AMD has a significant genetic component.7-10 Ample evidence supports the hypothesis that variance of genes involved in DNA repair,11-13 oxidative stress14, 15 and inflammation16-20 play a role in aging and age-related diseases. Many studies have documented the association between polymorphisms in complement factors (CF), oxidative stress, apolipoprotein E (ApoE), mitochondria and chaperone proteins genes and AMD.21-23 Single nucleotide polymorphism (SNP) in ApoE, ApoE or C2/BF may protect AMD. On the other hand, SNP in CFH, AMRS2/HTRA-1 or CX3CR1 gene may increase AMD risk.24 In this study, we would like to test whether the variations of biologically plausible genes (or the modifying genes) listed above are differentially distributed in AMD patients and normal populations. To this end, we choose genes that are believed to play a crucial role in the aging process and will analyze the frequency of SNPs specifically within the coding frames of biologically plausible genes responsible for aging and age-related diseases. Our aim will be to compare the allelic frequencies of candidate genes listed above in cohorts with AMD to the frequency in normal control subjects without AMD. With this study we hope to identify genetic risk factors that could have functional implications for understanding and treating AMD.