Regulation of neuronal network formation in mouse taste buds

Mashl在中枢神经系统和周围神经系统的神经元前体亚群中表达。然而，Mashl在味蕾细胞分化中的作用仍有待证实。在本研究中，为了进一步了解味蕾细胞分化的调控机制，我们利用Mashl KO小鼠研究了Mashl在味蕾细胞分化调控中的作用。在Mashl KO小鼠中，在Mashl突变体的环瓣乳头上皮和软腭味蕾中都缺失AADC-IR细胞。在Mashl KO/GAD67- gfp小鼠中，软腭味蕾中也缺失gfp阳性（GAD67表达型III细胞）细胞。另一方面，在Mashl突变小鼠的软腭味蕾中表达了味蕾II型细胞标记物Gustducin。这些结果表明，在味蕾III型细胞中，Mashl对AADC和GAD67的表达起重要作用。味觉受体细胞在某种意义上是上皮细胞，它们的寿命有限，因此必须被替换以维持上皮的结构。因此，味觉神经需要与合适的味觉受体细胞形成突触。然而，味觉感受器细胞表达合适的味觉感受器的识别机制尚不清楚。钙粘蛋白超家族的细胞-细胞粘附分子控制一系列的相互作用，调节解离，突触的形成。在本研究中，我们研究了钙粘蛋白超家族在味蕾中的表达模式，以验证钙粘蛋白是否需要在味觉神经和味觉受体细胞之间形成突触。

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.