An international team of researchers from the United States and Brazil discovered that a mutation in the Son of sevenless-1 (SOS1) gene causes hereditary gingival fibromatosis (HGF) type one, a rare form of gingival overgrowth. The team, led by Thomas Hart, D.D.S., Ph.D., associate professor of oral pathology and medicine, at the University of Pittsburgh School of Dental Medicine, studied a large multi-generational Brazilian family with high incidence of HGF.
From the information gathered from this family, they were able to determine the structure of the SOS1 gene. The gene codes for a protein that activates the ras pathway, which signals cell growth. When the gene is not mutated it is involved in the growth of normal, healthy gums. When the gene is mutated in the fashion discovered by Hart and his colleagues, it results in HGF.
"By understanding this gene and the mutation, we have the potential to understand what causes normal gingival growth and abnormal gingival overgrowth. We are now looking at the therapeutic potenital of manipulating this pathway," said Dr. Hart. "Not only does this create the potential for new therapies to treat HGF, but also new avenues for investigation into common dental problems like periodontal disease and receding gums."
Currently, the only available treatment for HGF includes cutting away the gingival overgrowth and trying to regrow the tissue between the teeth through grafting, a process that is both difficult and painful. By understanding the genetic cause of the disease, researchers say they can now start investigating new therapies, including tissue engineering to treat the disease.
This discovery may also have implications for the diagnosis and treatment of other related diseases, including drug-induced gingival fibromatosis. Researchers believe that by understanding what causes gingival overgrowth, they may ultimately be able to identify those predisposed to drug-induced gingival fibromatosis, an unwanted side effect of many commonly used drugs, affecting approximately 15 percent of patients who take dilantin for seizures; 15 percent who take calcium-channel blockers; 30 percent who take cyclosporine for autoimmune disorders; and 40 percent of transplant patients who combine cyclosporine and nifedipine as anti-rejection medication.
HGF is characterized by an enlargement of the gingiva, causing the gums to grow over the teeth. Those with HGF are predisposed to chronic infection, periodontitis and malocclusion.
The study was funded in part through a grant from the National Institute of Dental and Craniofacial Research (NIDCR). Other members of the research team include Drs. Yingeze Zhang, Michael Gorry, Suzanne Hart, Meg Cooper, Mary Marazita and Jared Marks from the University of Pittsburgh, and Drs. Deborah Pallos and Jose Cortelli from Taubate University, Brazil.