Eph Signaling Auditory Brainstem Development

描述（由申请人提供）： 这项研究提出了听觉脑干中精确突触连接形成的潜在分子机制。申请人先前已经表明，受体酪氨酸激酶的Eph家族的几个成员在鸟类听觉脑干核中表达，并且在突触连接形成期间沿着中线表达。这些受体介导轴突生长过程中的细胞-细胞相互作用，Eph受体及其配体肝配蛋白的梯度是视觉系统中形成精确地形图所必需的。本研究的具体目的是探讨Eph受体信号在听觉脑干投射发育中的作用。每组实验都包括描述性研究的发展表达和功能研究，使用实验操作。Inovo微电穿孔将用于错误表达Eph受体，体外标记方法将用于评价所得轴突投射。将在发育中的小鼠脑干中检查雏鸡发现的一般性。具体目标1提出实验来研究Eph受体和ephrin的梯度是否是从VIIIth神经轴突到鸟类耳蜗核的tonotopic投射的发展所必需的。大细胞的具体目标2将这些研究扩展到哺乳动物。Eph受体EphA 4在发育中的小鼠耳蜗核中不均匀地表达。将在缺乏EphA 4的突变小鼠中评估EphA 4在建立从第VIII神经到耳蜗核的同源投射中的作用。轴突投射从N。大细胞分支，使得同侧分支在靶的背侧区域中突触，n.对侧分支穿过背中线与对侧副核腹侧区接触。椎板。具体目标3中概述的实验将评估Eph受体在鸟类脑干中线耳蜗核轴突引导中的作用。这些实验将测试Eph信号传导是否广泛用于听觉脑干中通路的发展，并将解决Eph受体在建立突触特异性方面的作用是否在不同模式和不同物种之间相似。

DESCRIPTION (provided by applicant): The proposed research addresses potential molecular mechanisms underlying the formation of precise synaptic connections in the auditory brainstem. The applicant has previously shown that several members of the Eph family of receptor tyrosine kinases are expressed in avian auditory brainstem nuclei and along the midline during the formation of synaptic connections. These receptors mediate cell-cell interactions during axon outgrowth, and gradients of Eph receptors and their ligands, the ephrins, are required for the formation of precise topographic maps in the visual system. The Specific Aims are to test the roles of Eph receptor signaling in the development of auditory brainstem projections. Each group of experiments includes both descriptive studies of developmental expression and functional studies using experimental manipulations. Inovo microelectroporation will be used to misexpress Eph receptors and an in vitro labeling method will be used to evaluate resulting axonal projections. The generality of findings from chicks will be examined in developing mouse brainstem. Specific Aim 1 proposes experiments to investigate whether gradients of Eph receptors and ephrins are essential for the development of the tonotopic projection from VllIth nerve axons to the avian cochlear nucleus, n. magnocellularis. Specific Aim 2 extends these studies to mammals. The Eph receptor EphA4 is expressed nonuniformly in the developing mouse cochlear nuclei. The role of EphA4 in the establishment of a homologous projection from the VIIIth nerve to the cochlear nucleus will be evaluated in mutant mice that lack EphA4. Axonal projections from n. magnocellularis branch so that an ipsilateral branch synapses in the dorsal region of the target, n. laminaris, while the contralateral branch grows across the dorsal midline and contacts the ventral region of contralateral n. laminaris. Experiments outlined in Specific Aim 3 will evaluate the role of Eph receptors in the guidance of cochlear nucleus axons at the midline in the avian brainstem. These experiments will test whether Eph signaling is extensively used in the development of pathways in the auditory brainstem, and will address whether the roles for Eph receptors in establishing synaptic specificity are similar across modalities and across species.