Taste organs: formation and regulation

描述（由申请人提供）：味蕾细胞是将化学刺激转化为传递到中枢神经系统的神经信号的感觉末端器官，位于哺乳动物舌头的味觉乳头中。因此，味觉乳头宿主上皮细胞将分化为包括味蕾细胞。然而，味觉生物学领域缺乏对以下方面的完整理解：（1）在乳头发育中什么构成可能的味觉细胞前体;（2）前体如何以及何时在舌上皮中分化以获得味觉乳头和味蕾细胞表型;以及（3）在乳头和味蕾发育中，底层间充质如何以及通过什么因素向舌上皮发出信号。我们的初步数据的神经嵴（NC）衍生细胞分布在舌上皮细胞，和表型改变的舌和味觉乳头的遗传修饰诱导的间充质NC衍生细胞，表明神经嵴的贡献，上皮和间充质味觉器官的形成。Cre介导的、组织特异性的遗传标记和修饰为这些细胞谱系测定和功能分析提供了有力的工具。使用两种良好表征的转基因小鼠品系用于NC测定，Wnt 1-Cre和P0-Cre。我们发现：（1）在舌上皮中，可见Wnt 1-Cre和P0-Cre标记的NC衍生细胞，包括味乳头和味蕾（P0-Cre中丰富，Wnt 1-Cre中罕见），这表明味细胞的潜在NC衍生，这导致该领域的新概念。P0-Cre标记的细胞首先 在早期以单个、分散的成分分布，后来在味乳头和味蕾中以集群的方式分布。我们建议，单个的，分散的P0-Cre标记的上皮细胞是NC前体，这些将经历细胞分化为特定的细胞类型的味觉乳头和味蕾。(2)在舌间充质中，Wnt 1-Cre标记的NC来源细胞与味乳头和味蕾密切相关。Wnt 1-Cre驱动的、骨形态发生蛋白（BMP）的I型受体Alk 2和Alk 3的条件性遗传修饰以水平、阶段和受体特异性方式显著改变舌、味乳头和味蕾的形成和维持。这表明舌间充质中的BMP信号通过不同的受体与上覆上皮相互作用，在舌、味乳头和味蕾的发育中发挥不同的作用。拟议的研究将使用现代技术（Cre介导的遗传修饰）以及体内和体外研究的结合来解决有关味觉乳头器官形成的基本问题。我们的目标是：（目的1）显示最佳分期（1a）和原发颅区（中脑或后脑）（1b）NC细胞迁移到舌原基上皮中;这些细胞何时以及有多少在舌上皮中分化以获得特定的细胞表型（1c）;什么类型和比例的味蕾细胞来源于NC（1d）;（目的2）研究BMP信号在舌间充质NC细胞中的作用（ALK 2和ALK 3），在舌、味乳头和味蕾的发育和维持中与上覆上皮相互作用，具有遗传修饰以（2a）用Wnt 1-Cre驱动的Alk 2或Alk 3的条件性敲除下调BMP信号传导活性;和（2b）用Wnt 1-Cre驱动的每种受体的条件性组成型激活上调BMP信号传导。总体而言，拟议的研究证明细胞起源，分化和间充质相互作用的味觉乳头和味蕾将有助于了解味觉器官的发展，并将带来新的信息和新的观点，该领域的神经嵴的贡献，味觉乳头和味蕾细胞。

DESCRIPTION (provided by applicant): Taste bud cells, the sensory end organs that transduce chemical stimuli into neural signals conveyed to the central nervous system, reside in taste papillae in the mammalian tongue. Therefore, taste papillae host the epithelium that will differentiate to include taste bud cells. However, the field of taste biology lacks a complete understanding of: (1) what constitutes possible taste cell precursors in developing papillae; (2) how and when the precursors differentiate in lingual epithelium to acquire taste papilla and taste bud cell phenotypes; and (3) how and via what factors the underlying mesenchyme signals to tongue epithelium in papilla and taste bud development. Our preliminary data on neural crest (NC) derived cell distributions in lingual epithelium, and of phenotypic alterations of tongue and taste papillae induced by genetic modifications in mesenchymal NC derived cells, suggest neural crest contributions to both epithelium and mesenchyme in the formation of taste organs. Cre- mediated, tissue-specific, genetic labeling and modifications provide powerful tools for these cell lineage assays and functional analyses. Two well-characterized transgenic mouse lines for NC assays, Wnt1-Cre and P0-Cre, are used. We have found that: (1) In tongue epithelium, both Wnt1-Cre and P0-Cre labeled NC derived cells are seen including taste papillae and taste buds (abundant in P0-Cre, infrequent in Wnt1-Cre) suggesting a potential NC derivation of taste cells which leads to a new concept in the field. P0-Cre labeled cells are first distributed in single, scattered elements at early stages to a clustered pattern later in taste papillae and taste buds. We propose that the single, scattered P0-Cre labeled epithelial cells are NC precursors and these will undergo cell differentiation to specific cell types in taste papillae and taste buds. (2) In tongue mesenchyme, Wnt1-Cre labeled NC derived cells are closely associated with taste papillae and taste buds. Wnt1-Cre driven, conditional genetic modifications of type I receptors Alk2 and Alk3 for bone morphogenetic proteins (BMPs) significantly alter the tongue, taste papilla and taste bud formation and maintenance in a level-, stage- and receptor-specific manner. This suggests that BMP signaling in tongue mesenchyme, via distinct receptors, interacts with the overlying epithelium for different roles in the development of tongue, taste papillae and taste buds. The proposed studies will address fundamental issues about formation of the taste papilla organ, using modern techniques (Cre-mediated genetic modifications) and combination of in vivo and in vitro studies. Our goals are to: (Aim 1) demonstrate the optimal stage (1a) and primary cranial region (midbrain or hindbrain) (1b) of NC cell migration into the epithelium of tongue primordium; when and how many these cells differentiate in lingual epithelium to acquire specific cell phenotypes (1c); what types and proportions of taste bud cells are derived from NC (1d); (Aim 2) characterize how the BMP signaling in tongue mesenchymal NC derived cells, via distinct type I receptors (ALK2 and ALK3), interacts with the overlying epithelium in the development and maintenance of tongue, taste papillae and taste buds, with genetic modifications to (2a) down-regulate BMP signaling activity with Wnt1-Cre driven conditional knockout of Alk2 or Alk3; and (2b) up-regulate BMP signaling with Wnt1-Cre driven conditional constitutive activation of each receptor. Overall, the proposed studies for demonstration of cell origin, differentiation and mesenchymal interactions in taste papillae and taste buds will contribute to understanding development of the taste organ and will bring new information and novel perspectives to the field for neural crest contributions to taste papillae and taste bud cells.