NERVE-TARGET CELL INTERACTION IN TASTE BUD MAINTENANCE

描述（由申请人提供）：味觉的一个关键问题是，当受体细胞翻转，味蕾和神经纤维之间的连接不断变化时，系统如何保持关于味觉质量的稳定信息。要做到这一点，味觉外围必须具有高度的接受神经可塑性。我们开始了解与神经节细胞与味蕾连接的精确度有关的接受神经可塑性的神经化学基础。可塑性是最显著的味蕾退化时，去神经和他们的快速再生时，再神经。越来越多的证据表明，这种神经元靶细胞可塑性涉及神经营养因子及其酪氨酸激酶受体。在仓鼠中，真菌芽在去神经支配后独特地抵抗退化，我们发现在不抵抗去神经支配的价值状芽或叶状芽中没有发现BDNF、TrkB和TrkC的富集，例如，神经营养因子阳性的真菌芽细胞独特地不受去神经支配的影响。可以想象，表达这些生长因子的细胞参与了味蕾的维持和促进神经纤维的生长。这种维持包括增加生殖细胞发生的可能性，以抵消因去神经支配而导致的细胞损失，或对细胞寿命的影响，将通过BrdU标记进行评估。神经营养因子在靶向神经纤维中的作用将用多色亲脂性染料来探索，以精确地展示神经节细胞和单个芽之间的小群体之间的连通性。味蕾神经营养因子表达与去神经支配、再神经支配、生殖细胞发生和神经支配模式的关系的研究将着重于小鼠的分析。小鼠蕈状芽具有独特的离散神经支配模式，并且与仓鼠芽表达不同的神经营养因子（例如，较少的BDNF）。物种比较可以形成关于神经营养因子和受体在味蕾维持和神经支配中的作用的假设。现有的BDNF上皮过表达的小鼠系将用于验证芽周神经营养因子增加导致更密集，更少离散的神经支配和延长芽细胞发生或寿命的假设。为了比较，我们将产生芽特异性BDNF敲除小鼠，专门测试芽神经营养因子缺失对神经支配、再神经支配和生殖细胞分化的影响。此外，将产生一个可诱导的BDNF芽敲除小鼠来测试BDNF丢失的影响。

DESCRIPTION (provided by applicant): A key question in taste is how the system maintains a stable message about taste quality while receptor cells are turning over, constantly changing connections between the taste bud and its nerve fibers. To accomplish this the taste periphery must employ a high degree of receptoneural plasticity. We are beginning to understand the neurochemical basis of receptoneural plasticity in relation to the precision with which ganglion cells are connected to taste buds. Plasticity is most dramatic in the degeneration of taste buds when denervated, and their rapid regeneration when reinnervated. Evidence is growing that such neuron-target cell plasticity involves neurotrophins and their tyrosine kinase receptors. In hamster, the fungiform buds of which uniquely resist degeneration after denervation, we identified enrichments in BDNF, TrkB and TrkC not seen in vallate or foliate buds that do not resist denervation, e.g., neurotrophin-positive fungiform bud cells are uniquely unaffected by denervation. Conceivably, cells expressing these growth factors are involved in taste bud maintenance and in promoting nerve fiber in-growth. The possibilities that such maintenance involves increases in gemmal cell genesis to offset cell losses due to denervation, or influences on cell lifespan, will be evaluated by BrdU labeling. A role for neurotrophins in the targeting of nerve fibers will be explored with multicolored lipophilic dyes to demonstrate precisely the connectivity between small populations of ganglion cells and a single buds. Studies of taste bud neurotrophin expression in relation to denervation, reinnervation, gemmal cell genesis, and innervation patterns will emphasize analysis of the mouse. Mouse fungiform buds have uniquely discrete innervation patterns and express neurotrophins differently (e.g., less BDNF) than hamster buds. Species comparison allows formulation of hypotheses about the role of neurotrophins and receptors in taste bud maintenance and innervation. An existing BDNF epithelial overexpressing mouse line will be used to test the hypothesis that increased peri-bud neurotrophin results in denser, less discrete innervation and heightened bud cell genesis or lifespan. For comparison, bud-specific BDNF knockout mice will be generated to specifically test the effect of bud neurotrophin absence on innervation, reinnervation and gemmal cell differentiation. Additionally, an inducible BDNF bud knockout mouse will be generated to test the effect of BDNF loss.