Immunohistochemical Localization of YAP and TAZ in Mouse Molar Tooth Germ

Abstract

Tooth development is a multi-stage and multi-step process involving fate determination and morphogenetic patterning events, epithelial-mesenchymal interactions, and cell proliferation, differentiation, and migration. Animal model studies have shown that YAP and TAZ, effectors of the Hippo pathway, have a critical function in tooth morphogenesis. However, the function of YAP and TAZ in tooth development has not been well documented and its specific roles in tooth morphogenesis remain unclear. We used immunohistochemistry to examine the localization of YAP and TAZ in mouse mandibular first molar tooth germ. ICR mouse embryos on days E12, E14 and E18 were produced. Heads from these embryos were processed for paraffin embedding and prepared for immunohistochemistry. Immunostaining for YAP and TAZ showed different localization in tooth development. YAP was localized in the odontogenic epithelium from the early stages of tooth germ, but TAZ was not almost observed. YAP was also positive for pre-ameloblasts or inner enamel epithelium, which were high columnar cells. On the other hand, TAZ localized to odontoblasts and pre-ameloblasts or inner enamel epithelium. These results demonstrated functional differences between YAP and TAZ in tooth development, and suggested that these proteins were not only involved in cell proliferation, differentiation, and hard tissue formation, but also in three-dimensional cusp morphogenesis during tooth development.