Mechanisms of early axonal pathfinding in the olfactory system of larval zebrafish

斑马鱼幼虫嗅觉系统早期轴突寻路机制

• 批准号: 10386589
• 负责人: Jessica Nicole Brandt
• 金额: $ 4.6万
• 依托单位: UNIVERSITY OF PENNSYLVANIA
• 依托单位国家: 美国
• 财政年份: 2021
• 资助国家: 美国
• 起止时间: 2021-09-01 至 2024-08-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/10386589
• 关键词: Mechanisms; early; axonal; pathfinding; olfactory

Abstract In the olfactory system precise connections create a functional topographic map that translates odorant experience into ordered patterns of odorant-specific neural activity. This map is established early in development. Olfactory Sensory Neurons (OSNs) stochastically choose to mono-allelically express one Odorant Receptor (OR), which belong to the G-Protein Coupled Receptor (GPCR) family, from a large gene repertoire. Each OSN projects a single axon from the Olfactory Epithelium (OE) to the Olfactory Bulb (OB). Axons of OSNs first target larger identifiable neuropils called protoglomeruli. In zebrafish, our lab has found that the protoglomerulus an OSN axon targets correlates with the family or homology clade of its chosen OR. OSNs expressing ORs from different homology clades target different protoglomeruli. Subsequent to this initial protoglomerular targeting, the axons of OSNs expressing the same OR ultimately coalesce into smaller, distinct, and reproducible neuropil regions known as glomeruli. Thus, the target location of each axon on the OB is coordinated with its chosen OR. Previous research has shown that an OSN’s chosen OR and OR-driven neural activity are important for glomerular segregation. However, it is not known how clade-specific protoglomerular targeting and OR-specific glomerular segregation are achieved. Previous studies performed in the mouse may have conflated initial targeting processes with glomerular segregation due to the relative inaccessibility of early developmental stages. The foundational research in olfactory development utilized static imaging after development was complete, often leading to developmental processes being inferred rather than investigated. We believe protoglomerular targeting is determined by the coordinated expression of the OR locus and axon guidance loci, rather than OR protein function. We have shown through single-cell RNA sequencing that OSNs expressing ORs within the same homology clade also express similar transcription factors and axon-guidance-related factors. Further, OSNs expressing closely related ORs target nearby glomeruli. Thus, I hypothesize that regulators controlling OR choice in OSNs also regulate axonal guidance receptor expression, while OR-specific neural activity regulates the subsequent segregation of OR-specific glomeruli. Utilizing a recombinase-mediated cassette exchange approach, my proposed experiments will disambiguate the relative contributions of OR identity and OR-driven neural activity to protoglomerular and glomerular targeting.

摘要 在嗅觉系统中，精确的连接创建了一个功能地形图， 气味特定神经活动的有序模式。这张地图是在开发的早期建立的。 嗅觉感觉神经元（OSNs）随机选择单等位基因表达一种气味受体 (OR)属于G蛋白偶联受体（GPCR）家族。每个OSN 将单个轴突从嗅上皮（OE）投射到嗅球（OB）。OSNs的轴突首先靶向 称为原肾小球的较大的可识别的神经柱。在斑马鱼中，我们的实验室发现， OSN轴突靶标与其选择的OR的家族或同源进化枝相关。OSN表达来自 不同的同源进化枝靶向不同的原肾小球。在最初的肾小球靶向之后， 表达相同OR的OSN的轴突最终合并成较小的、不同的和可再生的神经元 称为肾小球的区域。因此，OB上每个轴突的目标位置与其选择的OR相协调。 先前的研究表明，OSN选择的OR和OR驱动的神经活动对于 肾小球分离然而，尚不清楚进化枝特异性的原肾小球靶向和OR特异性的靶向是如何发生的。 实现肾小球分离。先前在小鼠中进行的研究可能混淆了最初的 由于早期发育阶段的相对不可及性，靶向过程与肾小球分离有关。 嗅觉发育的基础研究在发育完成后利用静态成像， 往往导致发展过程被推断而不是调查。我们认为原肾小球 靶向是由OR基因座和轴突导向基因座的协调表达决定的，而不是OR基因座。 蛋白质功能我们已经通过单细胞RNA测序表明，表达ORs的OSN在细胞内表达ORs。 同一同源进化枝也表达相似的转录因子和轴突导向相关因子。此外，本发明还 表达密切相关OR的OSN靶向肾小球附近。因此，我假设监管机构控制 OSNs中OR选择也调节轴突导向受体的表达，而OR特异性神经活动 调节随后OR特异性肾小球的分离。利用重组酶介导的盒 交换的方法，我提出的实验将消除歧义的相对贡献或身份， OR驱动的神经活动，以肾小球和肾小球靶向。