Scientists at Wake Forest University School of Medicine report that they have cloned the gene responsible for an inherited form of kidney stone disease, which may open the way to new treatments.
The disease, called primary hyperoxaluria type II, "often results in the formation of kidney stones at a very young age," said Ross P. Holmes, Ph.D., associate professor of surgical sciences (urology), one of the authors of the study, published in the current issue of Human Molecular Genetics.
"In severe forms of the disease, kidney failure may occur, and other organs may fail, leading to early death," he said.
Scott D. Cramer, Ph.D.,assistant professor of cancer biology and surgical sciences (urology) and lead author, said patients with the disease have an alternate or mutated form of the gene, which ordinarily directs creation of a critical enzyme.
In these patients, the absence of the enzyme results in too much oxalic acid or oxalates, which in turn leads to formation of calcium oxalate stones, the most common form of kidney stones.
Cramer and Holmes said, "The discovery of this gene may lead to a better understanding of the way that oxalate is synthesized in the body."
That in turn may benefit not only patients with this disease, but also people with calcium oxalate kidney stones from other causes.
Primary hyperoxaluria type II ordinarily is detected because of excessive oxalate in the urine. The missing enzyme is hydroxypyruvate reducatase, and it is the body''s primary process for breaking down the oxalates.
With the discovery of the gene, Cramer and Holmes expect to develop an animal model for kidney stone disease. They plan to create a group of mice that are lacking a functioning gene, so they will be missing the hydroxypyruvate reductase enzyme.
Cramer said, "We will use the mice as a model to test new therapeutic treatments not only for this disease, but calcium oxalate stones in general."
Holmes said white men have the highest incidence of kidney stone disease, with 12-15 percent of the men in this group likely to have kidney stones sometime in their lifetimes. The peak in occurrence is in people during their 40s and 50s.
The research was funded by the National Institutes of Health and the Oxalosis and Hyperoxaluria Foundation.
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