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Q&A on Modifier Genes with Dr. Stephen Daiger

Funded by the Foundation Fighting Blindness since 1985, Dr. Stephen Daiger, of the University of Texas—Houston, is a world-renowned expert in identifying and understanding the genes and related mutations that cause retinal degenerative diseases.

Stephen Daiger, Ph.D.
Why can the severity of vision loss vary so much for people who have retinal degeneration caused by the same genetic mutation — even people within the same family?
The reasons are not well known, but this is an extremely important area of research because understanding the reasons for these individual differences may suggest new ways to modify or slow the progression of vision loss. Some people are “protected” from the bad effects of the disease and by understanding the protective factors, we may learn how to protect other people. Some modifying factors are probably environmental. For example, siblings exposed to different amounts of sunlight while growing up may have different vision loss.

However, some modifying factors are clearly inherited just as the original disease-causing mutation is inherited. But the inherited modifying factors are most likely in genes distinct from the original disease-causing gene. This is true for all forms of retinal disease, whether dominant, recessive or X-linked.

Have any researchers found modifier genes?
FFB-funded researcher Dr. Hemant Khanna and his colleagues at the Kellogg Eye Center, University of Michigan, recently found one of the major genetic factors modifying Leber congenital amaurosis (LCA) and the severe complications that may be associated with this condition. What Dr. Khanna found is that a common, non-disease-causing variant in a gene with the symbol “RPGRIP1” helps determine whether disease-causing mutations in other genes cause LCA alone or LCA with other disorders.

Are you and other researchers trying to find other modifier genes?
Yes. In addition to the work of Dr. Khanna, the Foundation supports other studies to identify factors that modify the clinical results of mutations in retinal disease genes. For example, Dr. Eric Pierce, of the Scheie Eye Institute at the University of Pennsylvania, is studying genetic differences in mice that are partly protected from the effects of mutations that cause retinal diseases in humans. Also, we in Houston are studying factors that protect people who have autosomal dominant forms of retinitis pigmentosa. Finding the factors that protect some people with genetic mutations causing retinal degeneration is a major strategic goal of the Foundation Fighting Blindness, because they would likely have great potential as vision-saving treatments.

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