Weekly Research Update

Researchers discover structural changes to DNA may contribute to age-related eye diseases.

DNA is the hereditary material within our cells and contains genes, which provide instructions to our body to make proteins so we can grow and develop. The epigenome describes the chemical changes to our DNA which regulate the activity of these genes, by switching them “on” or “off”. These chemical changes alter the structure of our DNA and results in a gene producing more or less of a particular protein. DNA methylation is one way in which our body controls gene activity, but as we grow older, this can become less tightly controlled.

A study recently published by the National Eye Institute indicates that changes to the way our body regulates gene activity as we age may contribute to the development of age-related retinal diseases. The findings of this study strongly suggest that structural changes to our DNA can increase our risk of vision loss and presents the epigenome as a promising therapeutic target for age-related retinal diseases, such as Age-related Macular Degeneration, the leading cause of blindness worldwide.

To investigate the epigenomic changes which may disrupt visual function, researchers at the National Eye Institute analysed and compared the DNA methylation patterns in mice rod photoreceptor cells at 4 different stages of life; 3 months, 12 months, 18 months and 24 months. The typical lifespan of a mouse is 2 years (24 months).

In total, researchers identified 2054 regions with DNA methylation changes, many of which are associated with cellular processes including energy metabolism, mitochondrial respiration; the conversion of energy from nutrients to a form the body can use, and longevity specific to rod photoreceptor cells.

Rod cells are an essential component of the visual system which detect dim light, assist with peripheral vison and promote survival of the cone cells, which perceive bright light and colour. Therefore, rod photoreceptor cells require large amounts of energy to fuel this activity. Researchers discovered that many aging rod cells switched from glucose, which is generally their preferred energy source, to fat, and that changes to gene expression patterns in these identified regions may contribute to age-related retinal disease onset.

As rod cells are so heavily reliant on energy to sustain normal function, they may also be more susceptible to genetic and environmental factors which interfere with their energy supply as we grow older and may cause age-related retinal diseases to develop.

Prior to this study, the epigenome and DNA methylation changes were not largely considered as contributing factors to the onset of age-related retinal diseases. However, this research provides significant connections between the epigenome, energy metabolism and other cellular processes and age-related retinal diseases, such as Age-related Macular Degeneration, providing a strong foundation for further study.

Additionally, exploring gene-editing of the epigenome and genes involved in these metabolic processes may yield positive results in the search for treatments and cures for age-related retinal diseases into the future.

Reference:

1. Corso-Díaz, X., Gentry, J., Rebernick, R., Jaeger, C., Brooks, M.J., van Asten, F., Kooragayala, K., Gieser, L., Nellissery, J., Covian, R. and Cogliati, T., 2020. Genome-wide Profiling Identifies DNA Methylation Signatures of Aging in Rod Photoreceptors Associated with Alterations in Energy Metabolism. Cell Reports, 31(3), p.107525.