On-line info leads to gene identification

November 16, 2000

INDIANAPOLIS -- Online information from the Human Genome Project has allowed researchers on two continents to jointly isolate the gene responsible for a rare form of rickets, and the findings may present hope for individuals with more common diseases and moderate renal insufficiency.

Researchers at the Indiana University School of Medicine and Ludwig-Maximilians University in Munich, Germany, have published their findings in the November issue of Nature Genetics.

The scientists mapped the gene FGF23 on the short arm of chromosome 12. The mutation is believed responsible for autosomal dominant hypophosphataemic rickets, a rare disorder first identified in the mid-1970s and known to exist in only a handful of families worldwide. Only about 30 people in the United States are known to have the inherited disorder, which can cause lower leg deformity (bowed legs and knock knees), missing teeth, bone pain and fractures. Individuals with ADHR do not produce phosphorus, an important element in bone development.

Michael J. Econs, M.D., associate professor of medicine and of medical and molecular genetics, and Kenneth E. White, Ph.D., research associate in the Department of Medicine, at the IU School of Medicine, and Marcy Speer, Ph.D., of Duke University School of Medicine, began the mapping process by first identifying the affected families and holding reunions for the various families. The researchers obtained blood samples at the reunions and during home visits.

After mapping the gene to chromosome 12, the researchers formed the ADHR consortium with Tim Strom, M.D., and Thomas Meitinger, M.D., of Ludwig-Maximilians University. The consortium members used various computer programs and online data provided by the Human Genome Project to identify genes in the region and then tested these genes for mutations in their ADHR patients. They identified mutations in one of these genes, which they named FGF23, in four families. The sequence of the FGF23 gene indicates it makes a secreted protein.

"The importance of this is that by using a few families and information from the Human Genome Project, we may have opened a window on how normal people metabolize phosphorus," said Dr. Econs. "This discovery may lead to the development of new therapies for these families and for individuals with less rare phosphorus-wasting diseases, as well as disorders that lead to excessive accumulation of phosphate, such as tumoral calcinosis and moderate renal insufficiency."

By using the online resources of the Human Genome Project, Drs. Econs and White believe their project was advanced by several years. They also believe that FGF23 may be one of the first, if not the first, gene isolated using online resources from the genome project.
The IU School of Medicine research was funded by grants from the National Institute of Arthritis and Musculosketal and Skin Diseases.

Indiana University

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