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Gene Mutation Results in Missing Teeth

Approximately 20 percent of the population are born unable to develop a full set of teeth. Although the underlying causes are mostly unknown, members of a Houston family who lack mainly their first and second molars were found to have a mutation in a gene called PAX9. This is the first report of a human disorder linked to PAX9, one of a family of "master" genes that help determine body shape and organ formation during embryological development. This discovery is an important contribution to understanding the genetics of human tooth development and brings scientists a step closer to someday replicating the process.

Scientists at the University of Texas-Houston Dental Branch and Baylor College of Medicine discovered the PAX9 mutation in a family in which congenitally absent molars were documented in members of three generations. The finding, published in the January issue of Nature Genetics, was supported by the National Institute of Dental and Craniofacial Research.

The discovery of the PAX9 mutation began with Dr. Rena D'Souza, an associate professor of orthodontics, directing her students to look for patterns of missing teeth in their patients. One of these students, coauthor Monica Goldenberg, observed a 13-year-old boy missing 14 permanent teeth. Further investigation revealed that the father and two brothers had a similar condition, and out of 43 family members, 21 were determined to have congenitally missing molars.

"This is an example of an astute clinical observation unveiling a classic pattern of autosomal dominant inheritance, where offspring of both sexes have a 50-50 chance of inheriting a mutated gene and the disorder associated with it," said D'Souza. "From that point it was a matter of applying the techniques of molecular epidemiology and DNA analysis to identify the gene."

NIEHS Centers To Breed Genetically Variant Mice

To help learn more about how human bodies repair their environment-damaged DNA and control their cells' life cycles, NIEHS will fund up to five research centers to develop and breed mice with genetic variations that are more like humans' in these regards. The centers will provide the special mutant mice for scientists throughout NIH and to other research programs as well.

Many cases of human disease are caused or triggered by a natural or man-made substance in the environment, often when an environmental substance causes a genetic mutation or a disturbance in cell growth. Variations in a person's genes make the person more, or less, sensitive to these substances or more, or less, able to resist or repair the damage.

Genetic variations explain why one smoker gets cancer or heart disease from that exposure while another smoker doesn't. Or why some members of a family react to environmental substances and develop asthma, while others do not. NIEHS said that understanding the variations in a mouse's genes better — and modifying the mice to add or subtract a human-like gene with its variations — will help scientists unlock the secrets of these and other human diseases in a variable humankind.

NIAMS Launches Projects in Autoimmunity

The National Institute of Arthritis and Musculoskeletal and Skin Diseases has awarded nearly $4 million for new projects on autoimmune diseases, conditions in which the body's immune cells mistakenly attack its own tissues and vital organs. The funds are part of a $30 million allocation from Congress to bolster research in autoimmunity.

The awards enhance NIAMS' commitment in this area, and involve the start-up of nine projects targeted against some 80 serious, chronic, autoimmune illnesses involving almost every human organ system.

"Autoimmune diseases like rheumatoid arthritis, lupus, scleroderma, alopecia areata, and many blistering skin diseases exact a huge toll in human suffering and economic costs," said NIAMS director Dr. Stephen Katz. "But we've recently witnessed exciting research advances in several of these, and we have every intention of pushing our knowledge base further."


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