Transsynaptic Tracing from Taste Receptor Cells Reveals Local Taste Receptor Gene Expression in Gustatory Ganglia and Brain
Transsynaptic Tracing from Taste Receptor Cells Reveals Local Taste Receptor Gene Expression in Gustatory Ganglia and Brain
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DOI：
10.1523/jneurosci.0381-15.2015
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发表时间：
2015-07
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影响因子：
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通讯作者：
A. Voigt;Juliane Bojahr;M. Narukawa;Sandra Hübner;U. Boehm;W. Meyerhof
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作者：
A. Voigt;Juliane Bojahr;M. Narukawa;Sandra Hübner;U. Boehm;W. Meyerhof
味觉感知在口腔中通过味觉刺激与特定受体的相互作用开始。味觉受体细胞 (TRC) 的特定子集在促味剂刺激下被激活，并将味觉信号传输到传入神经纤维并最终传输到大脑。特定的 TRC 如何影响支配神经以及 TRC 子集的激活如何导致区分不同质量和强度的促味剂尚不完全清楚。为了研究味觉回路的组织，我们使用基因打靶在小鼠味觉系统中表达跨突触示踪剂大麦凝集素（BL）。由于 TRC 与传入神经纤维没有突触连接，因此我们首先分析了味蕾 (TB) 内示踪剂的产生和转移。令人惊讶的是，我们发现 BL 分别在内源性 Tas1r1 和 Tas2r131 启动子的控制下横向转移到表达示踪剂的小鼠 TB 中的所有细胞类型中。此外，虽然我们在神经节和大脑中都检测到了 BL 示踪剂，但我们还发现了局部低水平的 Tas1r1 和 Tas2r131 基因，因此在这些组织中也发现了示踪剂表达。最后，我们使用二元遗传方法鉴定了外周和中枢神经系统中表达 Tas1r1 和 Tas2r131 的细胞。总之，我们的数据表明，来自苦味和鲜味受体细胞的遗传跨突触追踪不会选择性地标记味觉特异性神经元回路并揭示味觉神经节和大脑中的局部味觉受体基因表达。意义声明 先前的论文描述了小鼠中味觉通路的组织，该小鼠在苦味或甜味/鲜味感知味觉受体细胞中表达转基因的跨突触示踪剂。然而，报告的结果在交叉的突触数量和每个转移步骤后信号强度的降低方面存在显着差异。尽管如此，所有团体都声称这种方法适合特定质量的味觉路径可视化。在本研究中，我们证明，由于味蕾中示踪剂的横向转移以及感觉神经节和大脑中味觉受体的表达，源自鲜味和苦味受体细胞的遗传跨突触示踪不能选择性地标记味觉质量特异性神经元回路。此外，我们首次在三七总神经系统和中枢神经系统中观察到味觉受体表达细胞。
Taste perception begins in the oral cavity by interactions of taste stimuli with specific receptors. Specific subsets of taste receptor cells (TRCs) are activated upon tastant stimulation and transmit taste signals to afferent nerve fibers and ultimately to the brain. How specific TRCs impinge on the innervating nerves and how the activation of a subset of TRCs leads to the discrimination of tastants of different qualities and intensities is incompletely understood. To investigate the organization of taste circuits, we used gene targeting to express the transsynaptic tracer barley lectin (BL) in the gustatory system of mice. Because TRCs are not synaptically connected with the afferent nerve fibers, we first analyzed tracer production and transfer within the taste buds (TBs). Surprisingly, we found that BL is laterally transferred across all cell types in TBs of mice expressing the tracer under control of the endogenous Tas1r1 and Tas2r131 promotor, respectively. Furthermore, although we detected the BL tracer in both ganglia and brain, we also found local low-level Tas1r1 and Tas2r131 gene, and thus tracer expression in these tissues. Finally, we identified the Tas1r1 and Tas2r131-expressing cells in the peripheral and CNS using a binary genetic approach. Together, our data demonstrate that genetic transsynaptic tracing from bitter and umami receptor cells does not selectively label taste-specific neuronal circuits and reveal local taste receptor gene expression in the gustatory ganglia and the brain. SIGNIFICANCE STATEMENT Previous papers described the organization of taste pathways in mice expressing a transsynaptic tracer from transgenes in bitter or sweet/umami-sensing taste receptor cells. However, reported results differ dramatically regarding the numbers of synapses crossed and the reduction of signal intensity after each transfer step. Nevertheless, all groups claimed this approach appropriate for quality-specific visualization of taste pathways. In the present study, we demonstrate that genetic transsynaptic tracing originating from umami and bitter taste receptor cells does not selectively label taste quality-specific neuronal circuits due to lateral transfer of the tracer in the taste bud and taste receptor expression in sensory ganglia and brain. Moreover, we visualized for the first time taste receptor-expressing cells in the PNS and CNS.