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Color Blindness: New Cause Identified

Jun 02, 2015 01:26 PM EDT

(Photo : Pixabay)

Color blindness affects a significant portion of the population, most notably men. And now, new research has identified a new gene mutation that could possibly cause this condition.

At least, that's the case for those who suffer from a rare eye disorder (achromatopsia) marked by color blindness, as well as light sensitivity and other vision problems. The findings, which were published in the journal Nature Genetics, could lead to new, targeted treatments for this form of color blindness.

The newly discovered mutation applies to a gene called ATF6, which stands for activating transcription factor 6A. ATF6 is a key regulator of the unfolded protein response, which is critical for preventing the dangerous build-up of unfolded or mis-folded proteins.

Based on mouse studies, scientists from Columbia University Medical Center (CUMC) suspect that the cone cells of people with achromatopsia are not permanently damaged and could be revived by enhancing the pathway that regulates the unfolded protein response.

"Several drugs that activate this pathway have already been approved by the FDA for other conditions and could potentially benefit patients with achromatopsia," Stephen Tsang, one of the study leaders, said in a statement.

And by shedding light on the underlying genetic mechanism of achromatopsia, involving ATF6, researchers behind this new study may have opened new doors to overcoming preventable vision loss.

"Five genes had previously been linked to achromatopsia; however, they accounted for only about half of all cases," Tsang explained. "Using next-generation gene sequencing on a small group of patients, we found that mutations in a sixth gene - ATF6 - can independently lead to the disease."

By sequencing a portion of patient DNA called the exome, researchers identified the ATF6 mutation in a total of 18 patients by the end of the study. Then, through analyses of skin cells they further concluded that the ATF6 mutations were interfering with the signaling pathway that regulates the unfolded protein response. Surprisingly, the patients had no other ATF6-related abnormalities.

"ATF6 is found in every cell of the body, but for some reason only the cone cells were affected," said Tsang.

This led researchers to believe that ATF6 mutations account for only about one percent of cases of the disease.

Pictured: Optical Coherence Tomography (OCT) imaging revealed the loss of outer segments in foveal cone cells in the “optical gap” of a patient with ATF6A defects.
(Photo : Dr. Stephen Tsang, Columbia University Medical Center) Pictured: Optical Coherence Tomography (OCT) imaging revealed the loss of outer segments in foveal cone cells in the “optical gap” of a patient with ATF6A defects.

In addition, all of the studied patients were found to have significant fovea hypoplasia, which is defined by an undeveloped macula, or center of the retina. Curiously, this characteristic is not normally seen in other achromatopsia patients.

"As we sequence more and more achromatopsia patients, we're likely to identify other genes," Tsang concluded. "I think the important lesson of this study is that it demonstrates how advanced technologies are bringing precision medicine to the field of ophthalmology. Certain diseases may look the same based on the clinical diagnosis, but we're finding that each patient is a little bit different and may benefit from a personalized approach to treatment."

Mutations in ATF6 have not only been implicated in achromatopsia-related color blindness, but also in other conditions such as diabetes and Alzheimer disease models. But this is the first time that they have been directly linked to human disease.

Achromatopsia affects an estimated one in 30,000 people worldwide. It is a disorder of the retina's cone cells, which provide vision in daylight, including color vision. Rod cells, which provide vision in dim light or no light, are unaffected. It is first seen in infancy and does not progress. While there is currently no effective treatment for the disease, this research may help change that.

For more great nature science stories and general news, please visit our sister site, Headlines and Global News (HNGN).

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