Regulation of neuronal network formation in mouse taste buds

Mash1在中枢神经系统和外周神经系统的神经前体亚群中均有表达。然而，Mashl在味蕾细胞分化中的作用尚不清楚。在本研究中，我们利用Mashl KO小鼠研究了Mashl在调节味蕾细胞分化中的作用，以开始了解味蕾细胞分化的调控机制。在Mashl KO小鼠中，AADC-IR细胞在Mashl突变的环状乳头上皮和软腭的味蕾中都缺失。在Mashl KO/GAD67-GFP小鼠中，软腭味蕾中也缺少GFP阳性细胞(GAD67表达III型细胞)。另一方面，味蕾的II型细胞标志物Gustducin在Mashl突变小鼠的软腭味蕾中表达。这些结果表明，Mashl在味蕾III型细胞中AADC和GAD67的表达中起重要作用。味觉感受器细胞是上皮性细胞，其寿命有限，因此必须更换以维持上皮细胞的结构。因此，味觉神经需要与适当的味觉感受器细胞形成突触。然而，味觉感受器细胞表达适当的味觉感受器的识别机制仍不清楚。细胞间黏附分子的钙粘附素超家族控制着一系列的相互作用，调节解离和突触的形成。在本研究中，为了验证味觉神经和味觉感受器细胞之间形成突触是否需要钙粘蛋白，我们研究了味蕾中钙粘蛋白超家族的表达模式。

Mashl is expressed in subsets of neuronal precursors in both the central nervous system and the peripheral nervous system. However, involvement of Mashl in taste bud cell differentiation remained to be demonstrated. In the present study, to begin to understand the mechanisms that regulate taste bud cell differentiation, we have investigated the role of Mashl in regulating taste bud cell differentiation using Mashl KO mice. In Mashl KO mice, AADC-IR cells are missing both in the Mashl mutant circumvallate papilla epithelium and in the taste buds of soft palate. In Mashl KO/GAD67-GFP mice, GFP-positive(GAD67 expression type III cell) cells are also missing in the taste buds of soft palate. On the other hand, Gustducin, a type II cell marker of taste bud, is expressed in soft palate taste bud in Mashl mutant mice. These results suggest Mashl play an important role for expression of AADC and GAD67 in type III cell in taste buds.Taste receptor cells are epithelial in sense that they have a limited life span and therefore must be replaced to maintain the structure of the epithelium. Therefore gustatory nerves need to make synapse with appropriate taste receptor cells. However, mechanism of recognition of taste receptor cells which express appropriate taste receptor still unknown. The cadherin superfamily of cell-cell adhesion molecules controls a series of interactions that regulate the dissociation, synapse formation. In this study, in order to test whether the cadherins are required for formation of synapse between gustatory nerve and taste receptor cell, we have investigated expression patterns of cadherin superfamily in the taste buds.