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Researchers and Collaborators Identify
New Gene Causing Blindness

During their teen years, the world began to darken for three of Betti and Carlos Lidsky’s four children. That gradual loss of sight set their desperate parents on a path to finding out all they could about the strange disease known as retinitis pigmentosa.

Now there’s hope for better patient care and the possibility of developing new therapies to battle this disease that causes blindness. Researchers, led by geneticists at the Miller School, have identified a new gene that causes retinitis pigmentosa, ending the South Florida family’s nearly 20-year search for the causes of the malady.
Gathered at a Hope for Vision event honoring scientists conducting ophthalmic genetic research are, from left, Jeffery M. Vance, M.D., Ph.D., chair of the Dr. John T. Macdonald Foundation Department of Human Genetics, Eduardo C. Alfonso, M.D., chair of Bascom Palmer Eye Institute, Betti and Carlos Lidsky, Byron Lam, M.D., and Margaret A. Pericak-Vance, Ph.D.

The results came after the Lidskys allowed the family’s DNA to be tested for more than 50 retinitis pigmentosa (RP) genes. The link was not found until the family began consulting with UM researchers in late 2009 for the study led by Margaret A. Pericak-Vance, Ph.D., director of the John P. Hussman Institute for Human Genomics, and Byron Lam, M.D., professor of ophthalmology at Bascom Palmer Eye Institute.

By the summer of 2010, researchers had found the cause of the Lidsky children’s retinitis pigmentosa by using a new technology known as whole exome sequencing and then confirming it with zebrafish studies. “For 18 years, we have been searching for the genetic cause of this disease, and UM researchers have found it,” said Betti Lidsky. “These researchers are doing life-changing work that will benefit not only our family, but many other people.”

Retinitis pigmentosa refers to a large group of diseases that cause degeneration of the eye’s retina. The retina, located at the back of the eye, captures light that enters the eye, which is translated into images by the brain. In RP there is damage to the cells in the retina that capture light, known as cones and rods. Over time, these cells slowly stop working and vision deteriorates.

The RP gene codes for an enzyme known as dehydrodolichol diphosphate synthase, or DHDDS, which is thought to play a role in how rhodopsin, a light-sensing protein, works.

The result of the research, a paper titled “Whole-Exome Sequencing Links a Variant in DHDDS to Retinitis Pigmentosa,” was published in the American
Journal of Human Genetics. The team also included Stephan Züchner, M.D., director of the Center for Human Molecular Genomics at the Hussman Institute and first author of the paper, and researchers from UM and other institutions. Important evidence to support this gene as the cause of RP comes from research with zebrafish, led by collaborator Julia Dallman, Ph.D., in the Department of Biology at UM. When researchers in her lab blocked the enzyme, the fish became blind.