Abnormal incisor-tooth differentiation in transgenic mice expressing the muscle-specific desmin gene.

Immunocytochemistry and electron microscopic observations on the incisor-tooth organ of transgenic mice expressing the muscle-specific desmin gene under the direction of the vimentin promoter, reveal that the expression of the hybrid transgene occurs both in mesenchymal cells and differentiating odontoblasts. The muscle-specific desmin, as estimated 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 odontoblasts and ameloblasts. Our results are consistent with the hypothesis that odontoblasts have inductive properties on the differentiation of ameloblasts and that intermediate filaments among other factors play the role of cell and tissue organizer.