Vandenborne Kristien, Roelens Simon A, Darras Veerle M, Kühn Eduard R, Van der Geyten Serge
Laboratory of Comparative Endocrinology, Zoological Institute, K U Leuven, Naamsestraat 61, B-3000 Leuven, Belgium.
J Endocrinol. 2005 Aug;186(2):387-96. doi: 10.1677/joe.1.06161.
In this paper we report the cloning of the chicken preprothyrotropin-releasing hormone (TRH) cDNA and the study of its hypothalamic distribution. Chicken pre-proTRH contains five exact copies of the TRH progenitor sequence (Glu-His-Pro-Gly) of which only four are flanked by pairs of basic amino acids. In addition, the amino acid sequence contains three sequences that resemble the TRH progenitor sequence but seem to have lost their TRH-coding function during vertebrate evolution. The amino acid sequence homology of preproTRH between different species is very low. Nevertheless, when the tertiary structures are compared using hydrophobicity plots, the resemblance between chicken and rat prepro-TRH is striking. The cloning results also showed that the chicken preproTRH sequence includes neither a rat peptide spacer 4 (Ps4) nor a Ps5 connecting peptide. Comparison of the cDNA sequence with the chicken genome database revealed the presence of two introns, one in the 5' untranslated region, and another downstream from the translation start site. This means that the gene structure of chicken preproTRH resembles the gene stucture of this precursor in mammals. Based on the cDNA sequence, digoxigenin-labelled probes were produced to study the distribution of preproTRH in the chicken brain. By means of in situ hybridization, preproTRH mRNA was detected in the chicken paraventricular nucleus (PVN) and in the lateral hypothalamus (LHy).
在本文中，我们报告了鸡促甲状腺激素释放激素原（TRH）cDNA的克隆及其下丘脑分布的研究。鸡前促甲状腺激素释放激素原（pre-proTRH）包含五个促甲状腺激素释放激素（TRH）前体序列（Glu-His-Pro-Gly）的精确拷贝，其中只有四个两侧是成对的碱性氨基酸。此外，氨基酸序列包含三个类似于TRH前体序列的序列，但在脊椎动物进化过程中似乎失去了其TRH编码功能。不同物种之间前促甲状腺激素释放激素原（preproTRH）的氨基酸序列同源性非常低。然而，当使用疏水性图谱比较三级结构时，鸡和大鼠前促甲状腺激素释放激素原（prepro-TRH）之间的相似性很显著。克隆结果还表明，鸡前促甲状腺激素释放激素原（preproTRH）序列既不包括大鼠肽间隔区4（Ps4）也不包括连接肽Ps5。将cDNA序列与鸡基因组数据库进行比较，发现存在两个内含子，一个在5'非翻译区，另一个在翻译起始位点下游。这意味着鸡前促甲状腺激素释放激素原（preproTRH）的基因结构类似于哺乳动物中该前体的基因结构。基于cDNA序列，制备了地高辛标记的探针来研究前促甲状腺激素释放激素原（preproTRH）在鸡脑中的分布。通过原位杂交，在前室旁核（PVN）和下丘脑外侧区（LHy）中检测到了前促甲状腺激素释放激素原（preproTRH）mRNA。
