Macular Degeneration Caused by Mutation.

How can a single gene cause two very different eye diseases, each affecting a different segment of vision?

Research scientist Radha Ayyagari from the University of Michigan W.K. Kellogg Eye Center (1000 Wall St., Ann Arbor, MI; Tel: 734/763-1415; Website: www.Kellogg.umich.edu) has found that a gene associated with one retinal disease, retinitis pigmentosa, also causes a form of macular degeneration. In the August issue of Genomics, Ayyagari reports that the gene RPGR has a direct link to a form of early-onset macular degeneration that primarily affects males. The finding may ultimately help scientists understand how macular degeneration progresses. A number of scientists, including Kellogg's Anand Swaroop, have studied RPGR extensively and have discovered a large number of mutations that lead to other retinal diseases, including RP.

Ayygari's study revealed that the mutation for macular degeneration in the RPGR gene may have one of two characteristics: The defective gene may either be truncated or it may generate an entirely new protein.

Macular degeneration causes the loss of central vision that is needed for such activities as reading and driving. The peripheral or side vision is generally not affected. Retinitis pigmentosa (RP) first ...