The role of cAMP signaling in OSN axon convergence in the olfactory bulb

描述(由申请人提供)：这位博士后F32 Kirschstein NRSA提出了一项全面的研究和培训计划，研究与神经再生疗法相关的嗅觉系统中的神经发生和轴突指导。受损的神经系统未能自我修复，给全球数百万人带来了令人衰弱的后果。再生疗法的重点是通过再生和引导备用神经元的轴突或替换死亡的神经元来恢复受损的神经回路。嗅觉系统为研究成熟神经系统中的细胞替代和轴突靶向提供了一个有用的模型。尽管嗅觉神经元(OSN)轴突定位于嗅球的机制尚不清楚，但球内肾小球汇聚的前后模式与神经元cAMP水平和活动依赖的指导信号的表达变化有关。然而，cAMP参与轴突靶向的直接证据和所涉及的遗传机制尚缺乏。这项提议的具体目的将检验cAMP在肾小球轴突汇聚中起决定性作用的假设。如果这个想法是正确的，那么在未成熟的OSN中表现出cAMP持续增加的转基因小鼠应该表现出肾小球会聚和位置的改变。目的1将使用转基因小鼠，在未成熟的OSN中表达具有结构性活性的G蛋白偶联受体GPR12。GPR12偶联到Gas、腺苷环化酶和cAMP的产生。为了跟踪OSN轴突的特定群体，GPR12转基因小鼠将与OR-tauLacZ小鼠杂交，例如M71-tauLacZ品系。这将使OSN轴突的结合可视化。目的2将研究cAMP介导的下游信号事件的变化，从而导致基因表达的变化。识别未成熟OSN中cAMP驱动的信号转导将有助于阐明控制OSN轴突会聚在嗅球中的位置的机制。目的3将测试cAMP过度表达是否将挽救缺乏emx2基因的小鼠的靶神经支配的缺失。这些研究的结果将为了解cAMP信号在OSN轴突生长和嗅球会聚中的作用提供新的见解。 公共卫生相关性：细胞替代作为修复受损神经系统的一种再生方法仍然很有希望。我的研究目标将有助于理解嗅觉系统中允许正常细胞替换和适当的靶神经支配的过程。这种对内源性神经替代的理解只会有助于推动脑和脊髓损伤的有效再生疗法的设计。

DESCRIPTION (provided by applicant): This postdoctoral F32 Kirschstein NRSA proposes a comprehensive research and training plan in the study of neurogenesis and axon guidance in the olfactory system with relevance to neural regeneration therapies. Failure of the damaged nervous system to repair itself has debilitating consequences for millions of people worldwide. Regeneration therapies are focused on restoring damaged circuitry by regrowth and guidance of the axons of spared neurons or replacement of dead neurons. The olfactory system provides a useful model to study cell replacement and axon targeting in a mature nervous system. Although the mechanisms by which olfactory sensory neuron (OSN) axons are targeted to the olfactory bulb remain largely unknown, the anterior-posterior patterning of glomerular convergence in the bulb correlates with neuronal levels of cAMP and altered expression of activity-dependent guidance cues. However, direct evidence of the involvement of cAMP in axon targeting and the genetic mechanisms involved are lacking. The specific aims of this proposal will test the hypothesis that cAMP plays a definitive role in glomerular convergence of axons in the bulb. If this idea is correct, then transgenic mice exhibiting sustained increases in cAMP in immature OSNs should show altered glomerular convergence and position. Aim 1 will use transgenic mice that express a constitutively active G-protein-coupled receptor, GPR12, in immature OSNs. GPR12 couples to Gas, adenylyl cyclase and cAMP production. To follow specific populations of OSN axons, GPR12 transgenic mice will be crossed with OR-tauLacZ mice, such as the M71-tauLacZ strain. This will allow visualization of the coalescence of OSN axons. Aim 2 will investigate changes in cAMP-mediated downstream signaling events that lead to alterations in gene expression. Identification of cAMP driven signal transduction in immature OSNs will help to elucidate mechanisms that control the position of OSN axon convergence in the olfactory bulb. Aim 3 will test whether cAMP over expression will rescue the lack of target innervation in mice lacking the emx2 gene. The results from these studies will provide novel insight into the role of cAMP signaling in OSN axon growth and convergence in the olfactory bulb. PUBLIC HEALTH RELEVANCE: Cell replacement as a regenerative approach to repair the injured nervous system remains promising. My research aims will contribute to understanding the processes that allow normal cellular replacement and appropriate target innervation in the olfactory system. This understanding of endogenous neural replacement can only help advance the design of effective regenerative therapies for brain and spinal cord injuries.