Thyroid Hormone Receptor Genes of Neotenic Amphibians
Thyroid Hormone Receptor Genes of Neotenic Amphibians
复制标题
幼态两栖类甲状腺激素受体基因
DOI：
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发表时间：
1997
影响因子：
3.9
通讯作者：
V. Laudet
中科院分区：
文献类型：
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作者：
R. Safi;A. Bègue;C. Hänni;D. Stéhelin;J. Tata;V. Laudet
抽象的。由于甲状腺激素在两栖动物变态中起着关键作用，我们使用PCR扩增了与几种新生期两栖动物甲状腺激素受体（TR）基因的配体结合结构域部分相对应的DNA片段：Proteidea家族的强制性新生期成员，泥狗Necturus maculosus和Proteus anguinus以及兼性新生期Ambystoma属的两个成员：蝾螈Ambystoma mexicanum和虎蝾螈Ambystoma tigrinum。此外，我们寻找TR基因的基因组中的一个apode Typhlonectes compressicaudus。TR基因在所有这些物种中均被发现，包括专性幼态物种。获得的PCR片段包含C和E结构域，并且对应于α和β基因。它们的序列似乎是正常的，这表明在幼生期两栖动物的TR基因中没有加速进化速率。这一结果对于Ambystomatidae来说并不奇怪，已知它们对T3（3，3 '，5-三碘甲腺原氨酸）有反应，但与表明Proteidea不能对甲状腺激素有反应的生化和生物学数据不一致。有趣的是，通过RT-PCR分析，我们观察到TRα在Necturus的鳃、肠和肌肉以及Ambystoma mexicanum的肝脏中的高表达水平，而TRβ仅在Ambystoma mexicanum中检测到表达，而在Necturus中没有。TRα和TRβ的这种差异表达模式可以解释Proteidea中的幼态持续现象。从这些物种中克隆甲状腺激素受体基因片段，将使它们无法进行变态的分子研究成为可能。
Abstract. Since thyroid hormones play a pivotal role in amphibian metamorphosis we used PCR to amplify DNA fragments corresponding to a portion of the ligand-binding domain of the thyroid hormone receptor (TR) genes in several neotenic amphibians: the obligatory neotenic members of the family Proteidea the mudpuppy Necturus maculosus and Proteus anguinus as well as two members of the facultative neotenic Ambystoma genus: the axolotl Ambystoma mexicanum and the tiger salamander Ambystoma tigrinum. In addition, we looked for TR genes in the genome of an apode Typhlonectes compressicaudus. TR genes were found in all these species including the obligatory neotenic ones. The PCR fragments obtained encompass both the C and E domains and correspond to α and β genes. Their sequences appear to be normal, suggesting that there is no acceleration of evolutionary rates in the TR genes of neotenic amphibians. This result is not surprising for Ambystomatidae, which are known to respond to T3 (3,3′,5-triiodothyronine) but is not in agreement with biochemical and biological data showing that Proteidea cannot respond to thyroid hormones. Interestingly, by RT-PCR analysis we observed a high expression levels of TRα in gills, intestine, and muscles of Necturus as well as in the liver of Ambystoma mexicanum, whereas TRβ expression was only detected in Ambystoma mexicanum but not in Necturus. Such a differential expression pattern of TRα and TRβ may explain the neoteny in Proteidea. The cloning of thyroid-hormone-receptor gene fragments from these species will allow the molecular study of their failure to undergo metamorphosis.