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

描述（由申请人提供）：这个博士后F32 Kirschstein NRSA提出了一个全面的研究和培训计划，研究嗅觉系统中与神经再生疗法相关的神经发生和轴突指导。受损的神经系统无法自我修复，给全世界数百万人带来了衰弱的后果。再生疗法的重点是通过再生和引导幸存神经元的轴突或替换死亡神经元来恢复受损的电路。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。虽然嗅觉感觉神经元（OSN）轴突靶向嗅球的机制在很大程度上仍然未知，但球中肾小球会聚的前后模式与cAMP的神经元水平和活动依赖性指导线索的表达改变相关。然而，cAMP参与轴突靶向和所涉及的遗传机制的直接证据缺乏。这项建议的具体目标将测试的假设，cAMP在球的轴突的肾小球收敛中起着决定性的作用。如果这个想法是正确的，那么在未成熟的OSN中表现出持续增加的cAMP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，表达一个组成型活性的G蛋白偶联受体，GPR 12，在未成熟的OSN。GPR 12与Gas、腺苷酸环化酶和cAMP产生偶联。为了跟踪OSN轴突的特定群体，将GPR 12转基因小鼠与OR-tauLacZ小鼠（例如M71-tauLacZ品系）杂交。这将允许OSN轴突的聚结的可视化。目的2将研究cAMP介导的下游信号事件的变化，导致基因表达的改变。在未成熟的OSN中识别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过表达是否会挽救缺乏emx 2基因的小鼠中靶神经支配的缺乏。这些研究的结果将提供新的见解的作用，cAMP信号在OSN轴突生长和收敛的嗅球。 公共卫生相关性：细胞替代作为修复受损神经系统的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目标神经支配的过程。这种对内源性神经替代的理解只会有助于推进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.