﻿Epigenetics May Help Explain Degrading Eyesight

Elderly Woman Eye Epigenetics


Eyesight is usually one of the first casualties of aging. While most people will experience a deficiency in near focusing or presbyopia as they age, a common cause of gradual vision loss can be attributed to a disorder called Age-related Macular Degeneration (AMD).  

There are two types of AMD—wet and dry. The wet type is the least common form of AMD, and it occurs when new blood vessels grow behind the retina and begin to leak fluid, resulting in blurred vision.

Dry AMD is the most common type, and it occurs when fatty deposits called drusen accumulate in the macula – a highly sensitive part of the eye that is home to millions of light-sensing cells. The macula is mainly responsible for clarity of vision and, over time, the drusen cause atrophy and deterioration to both the retina and macula, altering one’s ability to see clearly.

Though AMD doesn’t lead to complete blindness, it will distort vision making it difficult to complete everyday tasks like driving and reading, or even seeing someone else’s face.  It is the leading cause of impaired vision in people over the age of 50 and is estimated to affect 288 million people all over the world in the next 20 years.

Not much is known about how people develop AMD, only that the major known risk factors are age and smoking. Currently, there aren’t any reliable preventative measures that can be taken against AMD, nor are there any cures at this time.

So, scientists from the University of Liverpool have turned to epigenetics to provide some insight on potential genes to target for treatment. We’ve previously learned the epigenetic process of DNA methylation may play a part in retinal development, but it turns out the same mechanism may leave us susceptible to developing AMD.

In a new study published in Clinical Epigenetics, a research team led by Dr. Louise Porter examined cells from the retinal pigment epithelium (RPE) of 44 human eyes: 25 AMD and 19 control. They performed genome-wide methylation analysis to measure DNA methylation levels in the genes associated with AMD development.

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DNA methylation is an epigenetic mechanism that involves the addition of a methyl (CH3) group to the 5th cytosine base on DNA and can be influenced by diet, smoking, aging, or inheritance. This modification can directly impact gene expression, often resulting in silencing a particular gene.

The researchers discovered increased methylation levels in three genes of the AMD eyes compared to the healthy control eyes. These three genes (SKI, GTF2H4, and TNXB) are all associated with the development and support of tissues.

Interestingly, the first two were not known to be associated with AMD development prior to this study. They suspect that the epigenetic dysregulation found here may be what leads to the development of AMD.

Dr. Porter highlights the importance of her team’s findings: “Our main aim for conducting this research was to help tackle an area of unmet clinical need. This work has identified new genes, providing us with novel targets for investigation in a disease in desperate need for therapies.” She and the team hope that research will continue to advance so that successful treatments can be developed.

Source: Porter S et. al. (2019) Whole-genome methylation profiling of the retinal pigment epithelium of individuals with age-related macular degeneration reveals differential methylation of the SKI, GTF2H4, and TNXB genes Clinical Epigenetics 11:6 

Reference: University of Liverpool “Study identifies new genes associated with the leading cause of blindness.” Univ. of Liverpool News. Jan. 2019

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