AXON-TARGET INTERACTIONS IN DEVELOPING CEREBELLUM

拟议中的研究将调查正在生长的轴突的成熟， 使用小鼠小脑作为模型系统，并将解决三个相关的 问题：1）在转型期的形式和细胞学的变化， 生长锥到成熟的突触乔木; 2）在何种程度上生长的尖端和 成熟的突触终扣反映了轴突的起源， 生长尖端与其微环境的相互作用;（3）什么 扩展了轴突生长在突触形成中所采取的策略， 连接包括错误，如果是这样，他们做了什么重新安排，以形成 适当的连接。 一旦形成特定的 连接被描绘，这种特异性的分子基础可以在 未来可以探索。 未成熟轴突和生长尖端的形式将在 在轴突等待期间， 在突触连接的形成过程中。 轴突将被标记为 辣根过氧化物酶（HRP）注射到脑切片，然后 光学和电子显微镜分析。 的三维形式 轴突和它们的生长尖端将与它们的细胞学相关联， 突触模式和与周围细胞的相互作用。 日益增长的 轴突生长过程中的尖端将与 等待和突触形成的过程 等待轴突与靶点的关系 将用HRP标记和特异性抗血清测定细胞， 突触和浦肯野细胞。 攀缘纤维和苔藓纤维将被识别 通过注射它们的特定轴突通路或起源核， 多余的瞬时连接重排参数 攀缘纤维分支和轴突与攀缘和苔藓纤维 特征将被记录。 删除来源的影响 将评估攀缘纤维对苔藓纤维成熟的影响。 的 轴突生长尖端与靶细胞的相互作用将通过 将小脑传入神经与纯化的颗粒细胞或浦肯野细胞共培养。

The proposed research would investigate the maturation of growing axons, using mouse cerebellum as a model system, and would address three related issues: 1) the changes in form and cytology during the transition of growth cone to mature synaptic arbor; 2) to what extent the growing tip and mature synaptic bouton reflect the origin of the axon versus the interaction of the growing tip with its microenvironment; (3) to what extent the strategies taken by growing axons in formation of synaptic connection include error, and if so, what rearrangements they make to form proper connections. Once the steps in the formation of specific connections are delineated, the molecular basis for such specificity can in the future be explored. The form of immature axons and growing tips will be characterized during outgrowth towards target structures, during the period axons wait and during the formation of synaptic connections. Axons will be labeled with horseradish peroxidase (HRP) by injection into brain slices, followed by light and electron microscopic analysis. The three dimensional forms of axons and their growing tips will be correlated with their cytology, synaptic patterns and interactions with surrounding cells. The growing tips on axons during outgrowth will be contrasted with those during periods of waiting and synaptogenesis. The relations of waiting axons with target cells will be determined with HRP labeling and specific antisera to synapses and Purkinje cells. Climbing and mossy fibers will be identified by injection of their specific axon pathways or nucleus of origin, and the parameters of the rearrangement of transient connections of supernumerary climbing fiber branches and of axons with both climbing and mossy fiber features will be documented. The effect of deletion of the source of climbing fibers on the maturation of mossy fibers will be assessed. The interaction of axonal growing tips with target cells will be studied by co-culturing cerebellar afferents with purified granule or Purkinje cells.