Development of Sensory Genomics and Basic Analysis on Taste Bioinformation Technology

味觉是任何动物保持其适当摄食行为的基本感觉。它也为我们构建传统饮食文化和发展尖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，我们对味觉接收和信号进行了基因组学研究。具体研究包括：1)分析模型鱼的味觉信号传递途径；2)分析小鼠的味觉信号转导途径。研究结果如下：(1)我们研究了GPCR→g蛋白→PLCbeta2→TRPM5通路，发现味觉信号效应因子PLCbeta2在medaka和斑马鱼以及哺乳动物中均有表达。然后我们发现味觉受体，t1rgpcr和T2R gpcr，以及TROM5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T1R1/3和T1R1/3获得氨基酸，通过T2Rs获得苦味。我们还尝试将显性阴性g蛋白连接到PLC启动子上，并成功构建了一个转基因的、味觉盲的medaka突变体。(2)在味觉传递研究方面，我们通过将凝集素、小麦胚芽凝集素（WGA）与T1R3启动子连接构建转基因小鼠，观察了WGA在味蕾、初级神经元、GG、NPG、TG以及NST中的信号事件。观察发现，WGA mRNA和蛋白均仅在t1r3阳性细胞中表达，在其他味觉细胞中均无表达。在部分GG、NPG甚至NST的神经细胞中也观察到WGA信号，从而成功鉴别出味觉细胞→味觉神经元→NST神经元的甜味和鲜味传递通路。

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.