MORPHOGENESIS AND DIFFERENTIATION OF GUSTATORY PAPILLAE

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Gustatory papillae are specialized structures which form in specific locations on the dorsal surface of the tongue; their epithelium is unique in its ability to form taste buds. The patterning, morphogenesis and differentiation of these structures and their resident taste buds offer a unique series of developmental events which could serve as a paradigm for epithelial-mesenchymal interactions and the role of nerves in the early stages of morphogenesis. The long term goal of this research is to provide insights into events leading to the formation of gustatory papillae, commitment of the gustatory epithelium to form taste buds and the role of innervation in the formation of gustatory papillae. Since much of gustatory papillary morphogenesis occurs in utero, studies of the causal factors involved in papilla formation have been prohibited by the difficulty of manipulating the process. Therefore, we have developed in vitro models to permit investigation of these processes in the mouse. Using these models, we propose the following Specific Aims: (1) Define the role of extracellular matrix (ECM) molecules and cell adhesion molecules (CAM) in the formation and differentiation of gustatory papillae by: a) determining the temporo-spatial distribution of ECM and CAM during placode and papilla formation and differentiation in vivo and in vitro; and b) demonstrating that perturbation of ECM and CAM results in abnormal papilla morphogenesis in vitro; (2) Elucidate the role of taste nerves in placode and papilla formation in vitro by: a) determining the effects of extirpation of taste ganglia on placode and gustatory papilla formation and differentiation; and b) comparing the ECM and CAM distributions within papilla with and without nerve to determine if innervation has a role in modulation their distribution; (3) Investigate factors involved in the guidance of taste nerves to the gustatory placode, by a) determining the effects of: (i) removing the gustatory placode; (ii) diverting nerves from normal pathways; (iii) ectopic placement of ganglia on the ingrowth of taste fibers into the dorsal tongue in branchial arch explants; and b) co-culturing taste ganglia with gustatory and non-gustatory epithelia. To achieve these goals, microdissection and tissue manipulation, roller tube culture, immunofluorescent staining, biological and biochemical inhibitors, autoradiography and image analysis will be used. These results of these studies will not only provide new information on how epithelial organs form in general, but will also contribute to our understanding of the development of taste which has a primary role in regulating feeding.