In both the eye and the kidney, U-M scientists found that mutations in NPHP5 produced defects in hair-like cellular structures called cilia, which serve as sensory devices throughout the body. Researchers are interested in cilia, because they may play an important role in diseases ranging from diabetes to Alzheimer's.
News of the discovery is published in the March 2005 issue of Nature Genetics. Edgar A. Otto, Ph.D., a U-M research investigator, is first author of the paper.
"It seems that defective ciliary proteins can lead to disease in virtually all organ systems," says Friedhelm Hildebrandt, M.D., the U-M's Frederick G.L. Huetwell Professor for the Cure and Prevention of Birth Defects, who directed the research. "Just as defective cilia in kidney tubules underlie kidney disease, defective cilia in the light-sensitive portion of the eye cause retinitis pigmentosa."
For the past 15 years, Hildebrandt and his collaborators have been studying nephronophthisis* (NPHP), a disease that leads to kidney failure in infants, children and young adults. Although rare, NPHP is the most common genetic cause of kidney failure in the first two decades of life. Other than dialysis or a kidney transplant, there is no treatment and no cure for NPHP.
In earlier research, Hildebrandt and coworkers discovered three genes, NPHP1, NPHP2, and NPHP3, mutated forms of which are responsible for three types of nephronophthisis. In 2002, they discovered a fourth gene, NPHP4, simultaneously with another research team in France.