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The Pingelapese colorblind
New gene identified to shed light on rare vision disorder
By Birgit Hofmann

Confined to a world of grays, blacks and whites, five percent of the Pingelapese islanders have never seen any colors. Pingelap, also called "the island of the colorblind", is a tiny atoll in the Western Pacific, one of the Eastern Caroline Islands of Micronesia, where complete achromatopsia is not rare but a rather common genetic disorder. Of the 3,000 Pingelapese, about one in twenty is suffering from total colorblindness paired with extreme sensitivity to light and reduced visual acuity.

Totally colorblind individuals can only see shades of gray, black and white (simulation).

The condition can be traced back to 1775, when Typhoon Lengkieki devastated the island, and the ensuing famine killed all but a handful of islanders. One of the few survivors was a carrier for the rare genetic mutation and—passing it on to his descendants—became the genetic founder for the vision disorder still apparent four generations later.

A team of researchers led by Olof Sundin, of the Johns Hopkins University School of Medicine in Baltimore, has now identified a small region on chromosome 8 as the location of the achromatopsia gene. This gene—CNGB3—is responsible for the defective response of the cones, which are the color-detecting photoreceptors of the eye. The study is published in the July issue of Nature Genetics.

There is presently no treatment for total colorblindness available. The identification of the causative gene provides a genetic basis for tests to detect carriers and represents a first step towards potentially new treatments in the future involving gene therapy.

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Sundin, O.H. et al. Genetic basis of total colourblindness among the Pingelapese islanders. Nat Genet 25, 289-293 (July 2000).
Sheffield, V.C. The vision of Typhoon Lengkieki. Nat Med 6, 746-747 (July 2000).

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