Childhood Blindness: Genetic Cause Finally Identified

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Blindness ; infantile: the genetic cause is finally identified

Breakthrough paves way for development of new therapies.

BCOR gene mutations cause early-onset retinitis pigmentosa, a group of rare eye diseases which lead to progressive vision loss in children, reveal work carried out in Montreal.

This breakthrough could pave the way for the development of new therapies and early detection of the disease, said Dr. Michel Cayouette, of the Montreal Clinical Research Institute.

Once we identify it and understand how this genetic problem leads to cellular degeneration, we can get down to trying to develop approaches to try to correct these mutations- there, then obviously eventually restore vision to the patient, he said.

The origin of this discovery dates back to the pediatric ophthalmology department of the Montreal Children's Hospital. Its director, Dr. Robert K. Koenekoop, came across a Quebec family in the course of his practice whose three young boys suffered from vision loss, but not from cancer, even though they had mutations in BCOR, a cancer gene implicated in the development of B-cell lymphoma and other cancers.

Believing to be on an interesting track to finally elucidate the genetic origin of retinitis pigmentosa, Dr. Koenekoop recruited Dr. Cayouette, who is recognized for his work on the biology of the retina.

This cooperation and the collaboration of the Quebec family has enabled researchers to understand, after several years of work, exactly how the mutations identified in BCOR cause vision loss.

Vision loss is caused by a loss of photoreceptors, the cells in the retina that allow us to see, which allow us to transform light into nerve impulses that are interpreted by the brain, explained Dr. Cayouette.

Mutations in the BCOR gene disrupt the expression level of many retinal genes, he added, which eventually causes retinal cell death and vision loss. He likens it to a thermostat losing control of the temperature in a house except it's about gene expression, not degrees Celsius.

Understanding the genetic origin of the problem is crucial to the eventual development of therapies to combat it, underlined Dr. Cayouette.

It is essential if we want to develop therapies, develop approaches using small molecules or gene therapy, for example, to try to slow down or even reverse the disease, he explained.

Gene therapy is already authorized in Canada for the treatment of a similar health problem, Leber's congenital amaurosis, recalled Dr. Cayouette. I think the advances we've made probably allow us to aim to eventually do a bit of the same thing for those kinds of conditions, he said.

But pending the eventual development of a treatment, the discovery by the Montreal researchers immediately dispels the uncertainty that families affected by early-onset retinitis pigmentosa are experiencing.

It allows parents, children, patients, to have a slightly clearer idea of ​​what is happening in their condition, explained Doctor Cayouette. This is often a major problem for patients: they end up having a condition that leads to blindness, but they are told, “yeah, we don't know what's causing your disease, we don't know the because of this disease”, so it creates a lot of anxiety and stress.

To be able to put a name to the gene in question, he adds , it's reassuring to know, OK, now I know that this is the mutation that is causing my disease, now we have to work, try to develop therapeutic approaches to try to correct these mysteries”.

The findings of this study are published by the journal Science Advances.

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