DALLAS - July 9, 1999 - UT Southwestern Medical Center at Dallas scientists have used genetically altered mice to help explain two types of human blindness, one that occurs in children and another that develops in approximately one in four adults over 65.
Stargardt's disease affects about one in 20,000 children over age 6, and age-related macular degeneration (AMD) develops in approximately one in four adults over 65. Both disorders affect central vision, which enables reading, driving and face recognition. The work is a major step toward finding treatment for these macular-degenerative illnesses, in which cells in the center of the retina - the macula - die.
The research, published in today's issue of Cell, describes a UT Southwestern study of mice that the investigators developed by inactivating the ABCR gene, which produces Rim protein (RmP). This study identifies the molecule transported by RmP in the retina's photoreceptor cells. When a mutation occurs in ABCR, then RmP dysfunctions and cannot perform its transporter role.
"Our research revealed, among other things, the biochemical change in patients with Stargardt's that makes vision more difficult when coming from sunshine into a dimly lit room," said Dr. Gabriel Travis, associate professor of psychiatry and an investigator in the Center for Basic Neuroscience at UT Southwestern. This symptom is called delayed dark adaptation, an early sign of the illness, which is the most common form of juvenile macular degeneration.
Because the genetically engineered animals lack the ABCR gene, RmP also
is missing. In normal mice, RmP inhibits accumulation in the retinal pigment
epithelium (RPE) of lipofuscin, a brown pigment generally associated with aging.
The buildup of lipofuscin poisons the RPE, which then cannot perform its role of
keeping photoreceptor cells healthy. The unhealthy cells begin to die, causing
blindness. The lipofuscin accumulation seen in the ro
Contact: Susan Steeves
UT Southwestern Medical Center