Cell Types, Circuits, and Plasticity in the Mouse Taste System

描述（由申请人提供）：在广泛研究的感觉系统中，例如，视觉，从初级神经节细胞开始的“细胞类型”已根据其结构和功能进行分类，并显示通过大脑内平行通路的不同投射。这种差异投射由平行连线的神经元组成，这些神经元编码和传递感觉刺激的不同方面，即在这个系统中，视觉图像。从神经节细胞开始，确定味觉系统是否具有类似的组织是本研究的目标。长期以来关于味觉神经节细胞生理类型的证据，以及我们最近关于味觉神经节细胞“形态/连接类型”的证据，为提出的目标提供了理论和实践基础。使用新设计的跨突触顺行病毒，我们将绘制一大批单个味觉神经节细胞的连接图，以充分表征基于它们在两个中枢突触之间突触连接的中枢味觉回路的初级感觉神经元类型。这些回路将被证实，并扩展到一个额外的突触通过神经解剖学的研究，以确定与病毒运输的位点。此外，该系统如何应对受体细胞的转换是味觉的一个独特挑战，对感觉编码有着深远的影响。我们的假设是，我们的病毒和神经解剖学研究揭示的神经节细胞的中心连接是固定的，但它们的外周纤维是可塑的，可以想象，随着时间的推移，它们会保持稳定的信息，例如，神经节细胞与相同类型的芽细胞的连接，即使它们翻转。我们将通过量化小鼠味蕾细胞的分化率、迁移运动和寿命来表征其活力。这将通过BrdU和受体细胞标记物gustducin或细胞凋亡标记物的双重标记来完成。最后，基于我们对离散神经节细胞-芽神经支配模式的论证，我们获得了神经节细胞具有显著可塑性的初步证据，随着时间的推移，纤维在附近芽中的撤回和部署。我们将研究单个神经节细胞与味蕾的关系，随着时间的推移，用生长纤维的GAP43标记，以及在单个神经节细胞及其过程中表达不同颜色荧光的Brainbow小鼠。

DESCRIPTION (provided by applicant): In extensively studied sensory systems, e.g., vision, "cell types", beginning with the primary ganglion cells, have been classified on the basis of their structure and function and shown to project differentially via parallel pathways within the brain. Such differential projections comprise parallel-wired sets of neurons that code and transmit different aspects of the sensory stimulus, i.e., in this system, of the visual image. Determining whether the taste system, beginning with the ganglion cells, has a similar organization is the goal of the present research. Long-standing evidence for physiological types of taste ganglion cells, and our recent evidence for "morphological/connectional types" of taste ganglion cells are boons to the theoretical and practical basis for the proposed aims. Using newly engineered trans-synaptic anterograde viruses we will map the connections of a large set of single taste ganglion cells to fully characterize types of primary sensory neurons based on the central taste circuits they synaptically engage across two central synapses. These circuits will be verified and extended one an additional synapse by neuroanatomical study targeting the sites identified with viral transport. Additionally, how the system copes with turn over of receptor cells is a unique challenge for taste and has profound implications for sensory coding. Our hypothesis is that central connections of ganglion cells revealed by our virus and neuroanatomical studies are fixed, but that their peripheral fibers are plastic, conceivably to maintain a stable message over time, e.g. connection of a ganglion cell to the same types of bud cells even as they turn over. We will characterize the dynamism of mouse taste bud cells by quantifying their rate of differentiation, migratory movement, and lifespan. This will be accomplished by double-labeling with BrdU and the receptor cell marker gustducin or an apoptosis marker. Finally, based on our demonstration of a discrete ganglion cell-bud innervation pattern, we obtained preliminary evidence for a remarkable ganglion cell plasticity with withdrawal and deployment of fibers among nearby buds over time. We will study this relationship of single ganglion cells to taste buds with dye labeling over time, with GAP43 labeling for growing fibers, and with Brainbow mice expressing different colored fluorescence in individual ganglion cells and their processes.