HomeResearchIntramural ResearchResearch Branches at NHGRIMedical Genetics Branch Hart Lab

Suzanne Hart, Ph.D. Associate Investigator Medical Genetics Branch Deputy Director Medical Genetics Residency and Fellowship Training Programs A.A. Diablo Valley College, 1983 B.S. California State University, 1985 Ph.D. Virginia Commonwealth University, 1990 (301) 594-6051 (301) 496-7157 shart@mail.nih.gov Building 10-CRC, Room 3-2563 10 Center Dr, MSC 1205 Bethesda, MD 20892-1205 Selected Publications

An American Board of Medical Genetics-certified clinical biochemical geneticist and medical geneticist, Dr. Hart uses molecular and biochemical techniques to understand genetic diseases of teeth, the oral cavity, and the kidney.

Gingival tissue plays an important role in tooth development, with gum health contributing to overall well-being, appearance, and the ability to eat and speak properly. Overgrowth of the gums can occur as an isolated inherited condition, as part of a genetic syndrome, or as a side effect of certain medications. In 2002, Dr. Hart and colleagues discovered the only known gene mutation involved in hereditary gingival fibromatosis (HGF), a rare form of gum overgrowth. The gene, SOS1, encodes a protein that activates the ras pathway, a key growth-signaling pathway in cells. The Hart laboratory is also studying syndromic forms of gingival overgrowth, such as Zimmerman-Laband syndrome and juvenile hyaline fibromatosis, as well as gingival overgrowth attributed to various medications.

Dr. Hart also investigates the molecular causes of disorders that affect the enamel or the dentin inside teeth. Of particular interest to her research are isolated tooth defects, as well as syndromes where tooth anomalies occur. The genes expressed in the developing tooth are difficult to analyze since teeth are mineralized structures, making the isolation of RNA needed to study gene expression difficult. Her group conducts mutation analysis and uses linkage-type approaches to study genes involved in normal tooth development, and has discovered mutations in a number of these (e.g., AMELX, ENAM, KLK4, MMP20, and DSPP). A large collection of samples compiled by Hart's group since 1991 forms the foundation for this research; these samples are routinely re-examined as new genomic technologies are developed that enable the identification of additional genes involved in the development of tooth defects.

Dr. Hart collaborated with the research group that identified the gene (CTCS) shown to be mutated in Papillon-Lefevre syndrome. This inherited disorder is characterized by keratosis of the palms and soles of the feet, as well as pronounced periodontal disease. Children with this condition suffer mouth inflammation and problems with their newly erupted teeth, with exfoliation and loss of the teeth by age 20.

Another area of Dr. Hart's research is related to medullary cystic kidney disease, a hereditary endoplasmic reticulum storage disorder caused by mutations in the UMOD gene. People with this rare dominant condition have a 50 percent risk of passing the disorder to their children. Currently, this project involves mapping the gene for the type 2 form of the disease, in which patients have normal kidney function through childhood but develop renal failure and ultimately require a kidney transplant. Her group is achieving promising results correcting protein defects in cell culture - progress that could lead to new therapeutic approaches.

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Last Reviewed: May 13, 2008