Science / Medicine : 2nd Blindness Gene Located

By studying 192 members of a large Kentucky family, Texas researchers have identified the approximate location of a second gene that causes retinitis pigmentosa, a hereditary eye disorder that often leads to blindness. RP affects about 100,000 Americans and 1.5 million people worldwide.

In 1989, researchers identified a defective gene that causes about one-third of the cases of RP. That gene, found on chromosome 3, is the blueprint for rhodopsin, a pigment that is important in vision.

Geneticists Stephen P. Daiger and Susan H. Blanton of the University of Texas Health Sciences Center in Houston reported at the human genetics congress that the new defective gene is found on chromosome 8. That discovery is particularly intriguing because no retinal genes are known to exist on chromosome 8. Precise identification of the defective gene should lead to new information about healthy vision as well as RP.