- Email: [email protected]
Tooth enamel gene identified by rDNA technology
JADA A dvances
in
Dental R esearch
Tooth enamel gene identified by rDNA technology
U
sing recombinant DNA technology, a team of dental scientists at the Univer sity of Southern California (USC) and Baylor College of Medicine has identified one of the four genes responsible for the production of tooth enamel in humans.1'4 This finding, supported by the National Institute of Dental Research, is the first step in a complex process that could eventually lead to the “cloning” of natu ral restorations for decayed teeth— restorative materials with structure and durability virtually identical to those of the healthy tooth. Progress in genetic engineering has proceeded at a faster pace than was ever anticipated. Four years ago, the produc tion of human insulin and human growth hormone through recom binant DNA technology opened the door to the possi bility of using this procedure to tailormake virtually any protein. These genesplicing techniques have found ready ap plication not only in medicine, industry, and agriculture, but now also hold poten tial for the field of restorative dentistry as well. Tooth enamel is produced, in part, by a blend of four different proteins—three amelogenins and one enamelin—each manufactured by its own gene. In studies with mice, USC investigators Drs. Harold Slavkin , M alcolm Snead, Margarita Zeichner-David, and associates isolated the tissues that produce these proteins and extracted the m essen ger RNA (mRNA). As its name implies, mRNA re lays instructions from the DNA—the gen e’s storehouse of gen etic in for mation—that tells the cell what to do. The scientists used the newly isolated mRNA to prepare a gene identical to the largest amelogenin. In collaboration with Dr. Savio Woo at Baylor, they spliced the gene into an established mammalian cell line. These living cell factories should begin to manufacture the specific enamel protein as programmed by its artificial genetic mechinery. The investigators are applying these techniques from the animal model to hu mans. Using the mouse enamel protein and antibodies to learn more about the 384 ■ JADA, Vol. 110, M arch 1985
M ammalian ameloblasts producing enamel extracellular m atrix as visualized with scanning electron microscopy. Note red blood cell (arrow) that is 7 /xm in diameter. Can this process be genetically engineered?
human counterpart, they found that both mouse and human enamel proteins share antigenic determinants, and that one of the four enamel proteins in humans is similar in genetic sequence to that deter mined for the mouse. This is particularly significant because it demonstrates the usefulness of the mouse gene products in identifying and isolating human enamel genes as well as in producing human tooth enamel proteins—the object of studies currently in progress. A number of steps have yet to be ac complished before a new restorative ma terial becomes available. The other three proteins must first be isolated and cloned. The research team must then hope that the four proteins will combine in the lab oratory with other essential components to form enamel with characteristics iden tical to the natural tooth. Despite the extensive work ahead, the investigators see exciting possibilities for the practical application of their research. If the studies continue as planned, den tists in the future may be filling cavities with an enamel-cloned material that har dens quickly and becomes in d istin guishable from the natural tooth enamel.
Moreover, Dr. Slavkin projects that this new substance may look better, last longer, and be less sensitive to heat and cold than the currently used silver, gold, and plastic restorative materials. These studies are also providing valuable clues to our understanding of both normal and abnormal genetic development in ani ____ mals and humans.
_________________________ J!*O A
Articles included in A dvances in D ental R esearch are selected by the National Institute of Dental Re search, Dr. Harald Lôe, director, and prepared by Pat ricia Sheridan, technical science writer, in coopera tion with the principal investigator. 1. Slavkin, H.C., and others. Enamel-like antigens in hagfish: possible evolutionary significance. Evolu tion 37(2):404-412, 1983. 2. Slavkin, H.C., and others. Antibodies to murine am elogenins: localization of enamel proteins during tooth organ developm ent in vitro. Differentiation 23:73-82, 1982. 3. Slavkin, H.C.; Zeichner-David, M.; and Siddiqui, M.A. Enamel extracellular matrix: differentia tion specific gene products and the control of their synthesis and accum ulation during development. In Silbermann, M., and Slavkin, H.C., eds. Current ad v an ces in sk eleto g en esis. Am sterdam , Excerpta Medica, 1982, pp 24-33. 4. Snead, M.L., and others. Construction and iden tification of mouse am elogenin cDNA clones. Proc Natl Acad Sci USA 80:7254-7258, 1983.
in
Dental R esearch
Tooth enamel gene identified by rDNA technology
U
sing recombinant DNA technology, a team of dental scientists at the Univer sity of Southern California (USC) and Baylor College of Medicine has identified one of the four genes responsible for the production of tooth enamel in humans.1'4 This finding, supported by the National Institute of Dental Research, is the first step in a complex process that could eventually lead to the “cloning” of natu ral restorations for decayed teeth— restorative materials with structure and durability virtually identical to those of the healthy tooth. Progress in genetic engineering has proceeded at a faster pace than was ever anticipated. Four years ago, the produc tion of human insulin and human growth hormone through recom binant DNA technology opened the door to the possi bility of using this procedure to tailormake virtually any protein. These genesplicing techniques have found ready ap plication not only in medicine, industry, and agriculture, but now also hold poten tial for the field of restorative dentistry as well. Tooth enamel is produced, in part, by a blend of four different proteins—three amelogenins and one enamelin—each manufactured by its own gene. In studies with mice, USC investigators Drs. Harold Slavkin , M alcolm Snead, Margarita Zeichner-David, and associates isolated the tissues that produce these proteins and extracted the m essen ger RNA (mRNA). As its name implies, mRNA re lays instructions from the DNA—the gen e’s storehouse of gen etic in for mation—that tells the cell what to do. The scientists used the newly isolated mRNA to prepare a gene identical to the largest amelogenin. In collaboration with Dr. Savio Woo at Baylor, they spliced the gene into an established mammalian cell line. These living cell factories should begin to manufacture the specific enamel protein as programmed by its artificial genetic mechinery. The investigators are applying these techniques from the animal model to hu mans. Using the mouse enamel protein and antibodies to learn more about the 384 ■ JADA, Vol. 110, M arch 1985
M ammalian ameloblasts producing enamel extracellular m atrix as visualized with scanning electron microscopy. Note red blood cell (arrow) that is 7 /xm in diameter. Can this process be genetically engineered?
human counterpart, they found that both mouse and human enamel proteins share antigenic determinants, and that one of the four enamel proteins in humans is similar in genetic sequence to that deter mined for the mouse. This is particularly significant because it demonstrates the usefulness of the mouse gene products in identifying and isolating human enamel genes as well as in producing human tooth enamel proteins—the object of studies currently in progress. A number of steps have yet to be ac complished before a new restorative ma terial becomes available. The other three proteins must first be isolated and cloned. The research team must then hope that the four proteins will combine in the lab oratory with other essential components to form enamel with characteristics iden tical to the natural tooth. Despite the extensive work ahead, the investigators see exciting possibilities for the practical application of their research. If the studies continue as planned, den tists in the future may be filling cavities with an enamel-cloned material that har dens quickly and becomes in d istin guishable from the natural tooth enamel.
Moreover, Dr. Slavkin projects that this new substance may look better, last longer, and be less sensitive to heat and cold than the currently used silver, gold, and plastic restorative materials. These studies are also providing valuable clues to our understanding of both normal and abnormal genetic development in ani ____ mals and humans.
_________________________ J!*O A
Articles included in A dvances in D ental R esearch are selected by the National Institute of Dental Re search, Dr. Harald Lôe, director, and prepared by Pat ricia Sheridan, technical science writer, in coopera tion with the principal investigator. 1. Slavkin, H.C., and others. Enamel-like antigens in hagfish: possible evolutionary significance. Evolu tion 37(2):404-412, 1983. 2. Slavkin, H.C., and others. Antibodies to murine am elogenins: localization of enamel proteins during tooth organ developm ent in vitro. Differentiation 23:73-82, 1982. 3. Slavkin, H.C.; Zeichner-David, M.; and Siddiqui, M.A. Enamel extracellular matrix: differentia tion specific gene products and the control of their synthesis and accum ulation during development. In Silbermann, M., and Slavkin, H.C., eds. Current ad v an ces in sk eleto g en esis. Am sterdam , Excerpta Medica, 1982, pp 24-33. 4. Snead, M.L., and others. Construction and iden tification of mouse am elogenin cDNA clones. Proc Natl Acad Sci USA 80:7254-7258, 1983.