Gene flaw that strips colour vision identified

Researchers have identified a previously unknown gene mutation that plays a major role in inherited eye disorder that makes people see the world in black and white.

People with the eye disorder achromatopsia are extremely sensitive to light and totally or predominantly colourblind. This type of colourblindness is different from the more common version, which makes some people unable to distinguish between red and green, the researchers explained.

"There are whole families with this sort of vision problem all over the world," said senior study author Jonathan Lin, associate professor at University of California, San Diego School of Medicine.

"We are very excited to have discovered a mutation in the ATF6 gene which plays a major role in this disorder," Lin said.

Five other genetic mutations have previously been identified by research groups as pivotal in achromatopsia, which causes markedly reduced visual acuity and very poor or no colour vision.

"But we still had families that did not have any of those gene mutations. We knew this meant there must be other genes and proteins involved," Lin said.

The study, which involved an international collaboration of inherited retinal disease specialists, found that a mutation in the ATF6 gene damaged proteins necessary for proper function of the eye's cone photoreceptors.

The eye has millions of these receptors, which control colour recognition and daytime vision.

In achromatopsia, malfunction of the cone photoreceptors causes sufferers to be either totally or predominantly colourblind.

"Achromatopsia sufferers see images on the gray scale," Lin said.

They also have problems with visual acuity and sensitivity to light. As levels of light increase, their vision decreases. Disease severity varies from person to person.

In the study, the scientists looked at 18 achromatopsia patients from 10 different families who had been identified as lacking the five previously known gene mutations.

All 18 were found to have the ATF6 gene mutation.

The study was published online in the journal Nature Genetics.