Gene Responsible for Congenital Lack of Teeth

Researchers at Baylor College of Medicine and The University of Texas-Houston Dental Branch have identified a gene defect that causes people to be born without six or more permanent teeth.

The findings, which appear in the January issue of the journal Nature Genetics, show that the gene called PAX9 is involved in regulating the tooth development process.

"Approximately 20 percent of the population has some form of abnormal tooth development, but little is known about the genetic causes," says Dr. Pragna Patel, Baylor associate professor of neurology and molecular and human genetics, and principal investigator for the study.

"Knowing more about the cause of missing teeth might lead to treatment or preventive strategies that could spare patients costly orthodontic corrections and risks to oral health," she says.

"This study grew out of a challenge I issued to my students to use basic science knowledge when diagnosing dental disorders," says study co-author Dr. Rena D'Souza, an associate professor of orthodontics at the Dental Branch. One of those students, study co-author Dr. Monica Goldenberg, noticed that a 13-year-old patient was missing 14 permanent teeth, and soon learned that his father and two brothers had the same condition. All had experienced normal primary tooth development.

Further research into the family records uncovered other members with oligodontia, a condition in which at least six permanent teeth are missing. The team studied 19 members of the family with the condition. When the DNA makeups of these family members were compared to those of family members unaffected by the condition, the research team noted a similarity on chromosome 14 that was not present in those unaffected. The research was furthered narrowed to reveal a mutation on the PAX9 gene found in all family members' missing teeth. The condition was traced back to family ancestors in the year 1645.

The genetic defect is hereditary and affects males and females equally. If a parent carries the genetic defect, the offspring have a 50 percent chance of inheriting it.

"The scientific community is rapidly discovering the genetic rules for tooth development. The mutation in PAX9 associated with missing teeth is a very significant contribution," says Dr. Harold Slavkin, director of the National Institute of Dental & Craniofacial Research (NIDCR).

Drs. David W. Stockton and Parimal Das at Baylor co-authored the paper with Drs. Patel, D'Souza and Goldenberg. The research was funded by the Kleberg Foundation, the March of Dimes Birth Defects Foundation and the National Institutes of Health.

- KRISTINA VAN ARSDEL

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©2006 Texas Medical Center

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