Development of Sensory Genomics and Basic Analysis on Taste Bioinformation Technology

味觉是任何动物保持适当摄食行为的基本感觉。这也为我们建设传统饮食文化、发展高端食品工业提供了不可或缺的动力。为了清楚地了解这种重要感觉的分子基础，我们使用基因组学对味觉接受和信号进行了研究。具体而言，研究包括1）模型鱼中味觉信号传递途径的分析和2）小鼠中味觉信号传导途径的分析，结果如下。(1)我们研究了GPCR→ G蛋白→ PLC β 2 → TRPM 5通路，发现味觉信号效应器PLC β 2在青鳉和斑马鱼以及哺乳动物中表达。然后，我们揭示了味觉受体，T1 RGPCR和T2 R GPCR，以及TROM 5存在于这些鱼以及人类和其他脊椎动物中。有趣的是，鱼通过T1 R2/3和T1 R1/3接受氨基酸，通过T2 Rs接受苦味剂。我们还尝试将显性负G蛋白连接到PLC启动子上，并成功构建了转基因的、味盲青鳉突变体。(2)在味觉传递研究中，我们通过将凝集素、麦胚凝集素（WGA）连接到T1 R3启动子上构建转基因小鼠，观察了WGA信号在味蕾、初级神经元、GG、NPG和TG以及NST中的信号传导。观察结果显示，WGA mRNA和蛋白质仅在T1 R3阳性细胞中表达，而在响应苦味和酸味的其他味觉细胞中不表达。在GG、NPG甚至NST的部分神经细胞中也观察到了WGA信号，因此我们成功地区分了味觉细胞→味觉神经元→NST神经元通路。

Taste is an essential sensation for any animal to keep its appropriate feeding behavior. It has also had an indispensable motivation for us to construct our traditional food cultures and develop sophisticated food industries. To have clear insights into the molecular basis of this important sensation, we have conducted the studies using genomics on taste reception and signaling. In detail, the studies are comprised of 1) analysis of taste signal transmission pathways in model fish and 2) analysis of taste signal transduction pathways in mice, with the following results. (1) We investigates the GPCR→G-protein→PLCbeta2→TRPM5 pathway and found that the taste signal effector, PLCbeta2, was expressed in medaka and zebrafish as well as in mammals. We then revealed that the taste receptors, T1RGPCRs and T2R GPCRs, and TROM5 existed in these fish as well as in humans and other vertebrates. Interestingly enough, the fish received amino acid by T1R2/3 as well as by T1R1/3 and bitter tastants by T2Rs We also tried to ligate the dominant-negative G-protein to the PLC promoter and succeeded to construct a transgenic, taste-blind medaka mutant. (2) For taste transmission studies, we constructed transgenic mice by ligation of the lectin, wheat germ agglutinin (WGA) to the T1R3 promoter, and observed the WGA signaling events in the taste bud, primary neurons, GG, NPG and TG, as well as those in NST. The observation revealed that both the WGA mRNA and the protein were expressed just in the T1R3-positive cells, with no expression in other taste cells responding to bitterness and sourness. The WGA signal was also observed in parts of neurocytes with GG, NPG and even NST, and we thus succeeded to differentially identify the taste cell→taste neuron→NST neuron pathway for sweet and umami-taste transmission.