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

描述（由申请人提供）：本博士后F32 Kirschstein NRSA提出了一项与神经再生治疗相关的嗅觉系统神经发生和轴突引导研究的综合研究和培训计划。受损的神经系统无法自我修复会给全世界数百万人带来衰弱的后果。再生疗法的重点是通过再生和引导存活神经元的轴突或替换死亡神经元来修复受损的神经回路。嗅觉系统为研究成熟神经系统的细胞替代和轴突靶向提供了一个有用的模型。尽管嗅感觉神经元（OSN）轴突定向到嗅球的机制在很大程度上仍不清楚，但球内肾小球会聚的前后模式与神经元水平的cAMP和活动依赖性引导信号的表达改变有关。然而，cAMP参与轴突靶向的直接证据和相关的遗传机制尚缺乏。这一建议的具体目的是验证cAMP在肾小球轴突会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OSNs中表现出持续增加cAMP的转基因小鼠应该表现出肾小球收敛和位置的改变。目的1将使用在未成熟osn中表达组成活性g蛋白偶联受体GPR12的转基因小鼠。GPR12与Gas、腺苷酸环化酶和cAMP结合。为了追踪OSN轴突的特定群体，GPR12转基因小鼠将与OR-tauLacZ小鼠（如M71-tauLacZ菌株）杂交。这将允许可视化OSN轴突的合并。目的2将研究camp介导的下游信号事件导致基因表达改变的变化。在未成熟OSN中发现cAMP驱动的信号转导将有助于阐明控制OSN轴突在嗅球中收敛位置的机制。Aim 3将测试cAMP过表达是否会挽救缺乏emx2基因小鼠靶神经支配的缺失。这些研究结果将为cAMP信号在嗅球OSN轴突生长和收敛中的作用提供新的见解。

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.