Scientists have discovered that mutations in the gene DRAM2 cause a new type of late-onset inherited blindness.
The article describes individuals from five families with a variety of DRAM2 mutations, all of which lead to loss of central vision beginning at age 30-40. Peripheral vision loss is also described in older individuals. The light-sensing rear surface of the eye (the retina) relays visual information to the brain. It's a complex layered structure, with each layer of cells carrying out clearly defined functions.
DRAM2 has a role in initiating a cell-recycling process called autophagy, in which the damaged components of cells are broken down and renewed. On discovering a link between DRAM2 mutations and inherited blindness, the authors showed that this protein is found in the retina; in the photoreceptor (light-sensitive) cells, and also at the surface of the retinal pigment epithelium (RPE) layer, where it meets the photoreceptors. RPE cells lie underneath the photoreceptors and take care of these essential cells.
"A high level of autophagy takes place in RPE due to the need for constant renewal of the photoreceptor outer segments following daily light-induced damage" says Dr. Manir Ali who led the team making the initial discovery at the University of Leeds. "It is therefore likely that, in the absence of correctly functioning DRAM2, autophagy and photoreceptor renewal is reduced, leading to thinning of the photoreceptor cell layer. Our findings suggest that DRAM2 is essential for photoreceptor survival."
Citation: El-Asrag et al., Biallelic Mutations in the Autophagy Regulator DRAM2 Cause Retinal Dystrophy with Early Macular Involvement., The American Journal of Human Genetics (2015), DOI:10.1016/j.ajhg.2015.04.006