RESUMO
In mammals, taste buds are maintained by continuous turnover of cells, even in adulthood. Cell proliferation and differentiation continue to produce taste cells, which express various genes related to taste reception. We found the co-expression of Sonic hedgehog (Shh) with Prox1 and that of Nkx2.2 with Mash1 in adult mouse taste buds. Whereas Prox1was expressed strongly in cells in the basal region of mouse taste buds where Shh was co-expressed, it was expressed weakly in almost all taste bud cells lacking Shh expression. At 0.5 day after birth, when taste cells have not yet differentiated, the expressions of Shh and Prox1 completely overlapped in the epithelium of circumvallate papillae. Nkx2.2 was observed in cells expressing Mash1, but not in cells expressing genes related to taste reception, such as gustducin and T1R3. Almost all fusiform cells expressing Mash1 co-expressed Nkx2.2, while the majority of round cells expressing Mash1 in the basal region of taste buds lacked Nkx2.2 expression.
Assuntos
Proteínas de Ligação a DNA/metabolismo , Proteínas de Homeodomínio/metabolismo , Papilas Gustativas/metabolismo , Transativadores/metabolismo , Fatores de Transcrição/metabolismo , Animais , Fatores de Transcrição Hélice-Alça-Hélice Básicos , Proteínas de Ligação a DNA/genética , Células Epiteliais/metabolismo , Células Epiteliais/patologia , Proteínas Hedgehog , Sequências Hélice-Alça-Hélice , Proteína Homeobox Nkx-2.2 , Proteínas de Homeodomínio/genética , Hibridização In Situ , Camundongos , Camundongos Endogâmicos C57BL , Dados de Sequência Molecular , Sondas RNA , Papilas Gustativas/citologia , Transativadores/genética , Fatores de Transcrição/genética , Proteínas Supressoras de Tumor , Proteínas de Peixe-ZebraAssuntos
Regulação da Expressão Gênica , Proteínas Hedgehog/metabolismo , Transdução de Sinais , Papilas Gustativas/metabolismo , Paladar/fisiologia , Animais , Fatores de Transcrição Hélice-Alça-Hélice Básicos/metabolismo , Diferenciação Celular , Linhagem da Célula , Proliferação de Células , Proteína Homeobox Nkx-2.2 , Proteínas de Homeodomínio/metabolismo , Camundongos , Camundongos Mutantes , Modelos Biológicos , Receptores Patched , Receptores de Superfície Celular/metabolismo , Fatores de Transcrição/metabolismo , Proteínas de Peixe-ZebraRESUMO
The nerve-dependency of gene expression in mouse taste bud was examined through an analysis of changes in gene expression in and around the taste buds in circumvallate papillae after surgery of cranial nerve IXth (glossopharyngeal nerve). The number of cells expressing T1r3, gustducin, Mash1 and Nkx2.2 gradually decreased after denervation. However, the expression intensity of these genes was barely influenced by denervation, and strong expression was observed at 6 days after denervation. In contrast, the basal cell-specific Sonic hedgehog (Shh) expression in the taste buds was decreased markedly at 6 h after denervation. In the regeneration process of taste buds, Shh expression was observed during a very early phase before taste bud formation. These results indicate the autonomous transcriptional control of genes in differentiated taste cells and the strong nerve-dependency of Shh expression in basal cells. Furthermore, in order to reveal the mitotic activity of Shh-expressing cells in taste buds, the BrdU-labeling experiments were performed using a combination of BrdU-immunohistochemistry and in situ hybridization. BrdU-signal was very rarely observed in Shh-expressing cells immediately after BrdU injection, and the signals were noted mainly in Ptc-expressing cells. BrdU signals rapidly increased in Shh-expressing cells in following 12 h and began to decrease after 2 days post-injection. These results suggest that most Shh-expressing cells are not mitotically active, but that Shh-expressing cells may be in the early transient developmental state of taste cells in taste buds.