Natriuretic peptides govern euryhalinity of fishes Analyses using transgenid technology

本实验室积累的数据有力地表明，利钠肽(NPs)控制鳗鱼的泛盐度；心房性NP(ANP)促进海水适应；C型NP(CNP)促进淡水适应。在这项研究中，我们试图利用转基因技术来确定ANP实际上是海水适应所必需的。为此，我们使用在同一属中具有多个相似物种的青竹鱼，这些鱼表现出不同的渗透适应性，并且已经建立了转基因技术。因此，不转ANP基因而不能在海水中存活的ANP转基因海水青蛙的生产将直接证明ANP在海水适应中的重要性。然而，尽管在其他几种硬骨鱼中成功克隆了ANP基因，但还没有在青冈鱼中克隆到ANP基因。同时，我们还检测到了4个CNP，命名为CNP-1~4，以及B型NP(BNP)，它们被认为是四足动物特有的NP。此外，我们还从现存的大多数原始脊椎动物、七鳃鳗和七鳃鳗中分离出了CNP-4型NPs。因此，我们提出了NP家族分子进化的新假说：CNP-4是NP家族的祖先分子，随着渗透调节机制的进化，它在硬骨鱼中表现出多样性。

Accumulating data from this laboratory strongly indicate that the natriuretic peptides (NPs) govern euryhalinity of eels ; atrial NP (ANP) promotes seawater adaptation and C-type NP (CNP) promotes freshwater adaptation. In this study, we attempted to determine that ANP is in fact essential for seawater adaptation using transgenic techniques. For this purpose, we use medaka fish that have plural akin species in the same genus that exhibit diverse osmotic adaptability and in which transgenic technique has already been established. Therefore, the production of ANP transgenic seawater medaka that cannot survive in seawater without transferred ANP gene will directly demonstrate the importance of ANP in seawater adaptation. However, ANP cDNA have not been cloned in medaka fish although cloning was successful in several other teleost species. Meanwhile, we could detect four CNPs, named CNP-1 through 4, and B-type NP (BNP) that had been thought as tetrapod-specific NP. Furthermore, we isolated CNP-4 type NPs from most primitive extant vertebrates, lamprey and hagfish. Therefore, we proposed new hypothesis of the molecular evolution of the NP family ; CNP-4 is an ancestral molecule of the NP family and it was diversified in bony fishes in parallel with the evolution of osmoregulatory mechanisms.