Role of Zic Genes in Patterning the Binocular Projection

描述(申请人提供)：视交叉中的视网膜神经节细胞(RGC)投射的交叉对于视觉信息的正常映射是必不可少的，并确保每个半球接收来自双眼的信息以建立双眼视觉。如何确定双眼通路的发展一直是一个谜。最近对脊髓的研究表明，不同的神经元亚群表达同源结构域转录因子的组合，这种编码决定了投射到特定靶点的情况。我们假设，类似的调控基因表达密码可能指定RGC的未杂交和交叉亚群。本实验室已发现含有转录因子Zic2的锌指在视网膜节细胞中以不交叉的轨迹表达。Zic2，而不是其他Zic家族成员，在未交叉的RGC亚群将轴突从该位置投射到交叉时，在腹颞部(VT)视网膜的RGCs中动态表达。体外获得和丧失功能的实验表明，当与交叉细胞共同培养时，Zic2是必要和充分的转换视网膜轴突的生长行为，从交叉模式到非交叉模式，反之亦然。此外，Zic2的表达与几个物种的双眼视觉程度相关。我们实验室的其他工作已经确认EphB1是一个受体系统，在小鼠的交叉中线与抑制因子ewitinB2相互作用。EphB1与Zic2在空间和时间上表达一致。 这项拟议的工作将进一步分析Zic2指定未交叉的视网膜神经节细胞轴突轨迹的假设，通过调节Eph家族中介导视交叉中线视网膜轴突发散的引导受体的表达。目的包括验证Zic2在神经节细胞中的表达具有未交叉轨迹并阐明其时间表达(AIM1)；通过在体内使用功能丧失和功能获得策略确认Zic2对于建立未交叉轨迹是必要的且充分的(目标2)；研究Zic2的S对作为潜在靶标的基因的影响，尤其是关于视网膜中的EphB1受体的影响(目标3)。这一分析应该有助于建立双眼通路的模式，并应适用于神经系统其他部位双侧感觉通路的建立。

DESCRIPTION (provided by applicant): The decussation of the retinal ganglion cell (RGC) projections in the optic chiasm is essential for normal mapping of visual information, and insures that each hemisphere receives information from both eyes to establish binocular vision. How the development of the binocular pathway is determined has been a longstanding enigma. Recent work in the spinal cord has shown that distinct subpopulations of neurons express combinations of homeodomain transcription factors and that such code determines projection to specific targets. We hypothesized that a similar code of regulatory gene expression might designate the uncrossed and crossed subpopulations of RGCs. Our laboratory has discovered that a zinc-finger containing transcription factor Zic2, is expressed in RGCs with an uncrossed trajectory. Zic2, but not other Zic family members, is postmitotically but dynamically expressed in RGCs in ventrotemporal (VT) retina in the period when the uncrossed RGC subpopulation projects axons from this location toward the chiasm. Gain- and loss-of-function experiments in vitro indicate that Zic2 is necessary and sufficient to switch the outgrowth behavior of retinal axons when co-cultured with chiasm cells, from crossed to uncrossed patterns, or vice versa. Moreover, Zic2 expression correlates with the degree of binocular vision across several species. Other work in our lab has identified EphB1 as a receptor system interacting with the inhibitory factor ephrinB2 at the chiasm midline in mouse. EphB1 is expressed coincident with Zic2, spatially and temporally. The proposed work will further analyze the hypothesis that Zic2 specifies the uncrossed retinal ganglion cell axon trajectory, by regulating expression of guidance receptors in the Eph family that mediate retinal axon divergence at the optic chiasm midline. Aims include verification that Zic2 is expressed in ganglion cells with an uncrossed trajectory and elucidation of its temporal expression (Aim1); confirmation that Zic2 is necessary and sufficient to establish an uncrossed trajectory, by using loss- and gain-of-function strategies in vivo (Aim 2); investigation of Zic2's influence on genes that are putative targets, especially with regard to the EphB1 receptor in the retina (Aim 3). This analysis should shed light on patterning the binocular pathway and should apply to the establishment of bilateral sensory pathways elsewhere in the nervous system.