ABNORMAL INCISOR-TOOTH DIFFERENTIATION IN TRANSGENIC MICE EXPRESSING THE MUSCLE-SPECIFIC DESMIN GENE

Immunocytochemistry and electron microscopic observations on the incis or-tooth organ of transgenic mice expressing the muscle-specific desmi n gene under the direction of the vimentin promoter, reveal that the e xpression of the hybrid transgene occurs both in mesenchymal cells and differentiating odontoblasts. The muscle-specific desmin, as estimate d by fluorescence intensity, is more expressed in immature mesenchymal cells than in postmitotic differentiated odontoblasts. The expression of the transgene generates alteration of the odontoblast-intermediate filament network and interferes with the secretory activity of both o dontoblasts and ameloblasts. Our results are consistent with the hypot hesis that odontoblasts have inductive properties on the differentiati on of ameloblasts and that intermediate filaments among other factors play the role of cell and tissue organizer.