02 June 2015

The sixth culprit of achromatopsia has been found

Geneticists have discovered a gene for the disease of "black and white" vision

RIA News

An international group of geneticists has found out that the so-called achromatopsia, a disease of black-and-white vision, occurs as a result of a mutation in the ATF6 gene, which breaks the light-sensitive proteins in the cones on the retina of the eye and turns the world into an illuminated black-and-white photograph, according to an article published in the journal Nature Genetics (Kohl et al., Mutations in the unfolded protein response regulator ATF6 causes the cone dysfunction disorder achromatopsia – VM).

"There are whole families on Earth who suffer from similar vision problems. People with achromatopsia see the world in shades of gray. In the most severe cases, they cannot drive a car, read books, watch TV or just work. In fact, they are blind," says Jonathan Lin from the University of California at San Diego (in a press release, UC San Diego A World Without Color – Researchers Find Gene Mutation That Strips Color, Reduces Vision - VM).

Lin and his colleagues uncovered the causes of this severe hereditary disease and paved the way for the development of gene therapy to suppress it by studying DNA samples that were obtained from members of several families suffering from achromatopsia.

Similar studies have been conducted before, and during them five genes were identified, mutations in which caused achromatopsia of varying severity. The problem, as the authors of the article explain, was that a significant part of the carriers of "black and white" vision did not possess any of these five mutations. This forced scientists to check what other factors could be involved in the development of achromatopsia.

To do this, Lin and his colleagues gathered a group of 18 volunteers who suffered from black-and-white vision and were not carriers of five previously discovered mutations, collected samples of their genome and compared them with each other. The "family" approach allowed scientists to understand which of the two sets of DNA inherited from the father and mother was to blame for the development of achromatopsia.

As it turned out, another gene was involved in the development of achromatopsia – ATF6 (activating transcription factor 6, transcription activation factor – 6), a special section of the genetic code that is responsible for cleaning cells from improperly assembled three-dimensional protein molecules and "rebooting" the cellular conveyor for their assembly.

In the cones of people suffering from achromatopsia, the work of this gene is disrupted due to a typo with a length of only one "letter"-a nucleotide, as a result of which they gradually become "clogged" with improperly assembled protein molecules and eventually die or simply stop working.

According to Lin, such a breakdown is not necessarily irrevocable, and he believes that it can be dealt with with the help of gene therapy, changing damaged copies of ATF6 to their normal version. According to him, similar experiments are already being conducted on mice, and their results, as the geneticist hopes, will help to find a way to help people with this rare disease to return colors to their lives.

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