Misexpression of genes in mouse tooth germs using in vitro electroporation

Mouse mandible primodia in vitro explant cultures are an excellent model for investigating tooth development. Mandibular arch epithelial-mesenchymal tissue recombinations and implantation of beads soaked in signaling proteins have revealed much about the early events of odontogenesis. These approaches do, however, suffer from several disadvantages, in particular the nonphysiological nature of beads soaked in very high concentrations of proteins and the inability to directly manipulate receptor and transcription factor gene expression. We have utilized the technique of DNA electroporation to deliver targeted gene expression to defined areas of mandibular arch epithelium or mesenchyme. This approach is being used to (a) ectopically express epithelial signals such as Shh and Bmp-4, (b) inhibit BMP and FGF signaling by expression of dominant negative receptors and antagonists, and (c) misexpress transcriptional factors in the mesenchyme. The technical aspects of electroporation are discussed, as well as preliminary findings.