Department of Applied Biochemistry, Faculty of Agriculture, Utsunomiya University, 350 Mine-machi, Utsunomiya, Tochigi 321-8505, Japan.
Gen Comp Endocrinol. 2011 Jan 15;170(2):374-80. doi: 10.1016/j.ygcen.2010.10.013. Epub 2010 Oct 25.
Molecular cloning of thyrotropin-releasing hormone receptors (TRHR) was performed in a model teleost fish, medaka (Oryzias latipes). Four subtypes of TRHR were cloned and named them as TRHR1a, TRHR1b, TRHR2 and TRHR3 based on their similarity to known TRHR subtypes in vertebrates. TRHR1a, TRHR1b, TRHR2, and TRHR3 of medaka encode 416, 398, 451, and 386 amino acid residues, respectively. Comparison of cDNA sequences of medaka TRHR subtypes with respective genomic DNA sequences revealed gene structures: TRHR1a, TRHR1b and TRHR3genes consist of two exons while the TRH2 gene consists of five exons. Molecular phylogenetic analyses depicted the molecular evolution of TRHR in vertebrates: From the ancestral molecule, TRHR2 diverged first and then TRHR1 and TRHR3. Reverse transcription-polymerase chain reaction analyses revealed the sites of TRHR expression: Expression of TRHR1, TRHR1b and TRHR2 subtypes has been confirmed in the brain, pineal organ, retina and pituitary gland. In addition, TRHR1b is expressed in spleen, digestive tract and skin, and TRHR2 in testis, ovary and gill. TRHR3 is widely expressed in various tissues. These results indicate that in medaka, TRH might exert multiple functions mediated by different TRHR subtypes expressed in each tissue.
促甲状腺素释放激素受体（TRHR）的分子克隆在模式硬骨鱼，青鳉（Oryzias latipes）中进行。克隆了四种亚型的 TRHR，并根据它们与脊椎动物中已知的 TRHR 亚型的相似性将其命名为 TRHR1a、TRHR1b、TRHR2 和 TRHR3。青鳉的 TRHR1a、TRHR1b、TRHR2 和 TRHR3 分别编码 416、398、451 和 386 个氨基酸残基。青鳉 TRHR 亚型的 cDNA 序列与相应的基因组 DNA 序列的比较揭示了基因结构：TRHR1a、TRHR1b 和 TRHR3 基因由两个外显子组成，而 TRH2 基因由五个外显子组成。分子系统发育分析描绘了 TRHR 在脊椎动物中的分子进化：从祖分子开始，TRHR2 首先分化，然后是 TRHR1 和 TRHR3。逆转录-聚合酶链反应分析显示了 TRHR 的表达部位：在脑中、松果腺、视网膜和垂体中证实了 TRHR1、TRHR1b 和 TRHR2 亚型的表达。此外，TRHR1b 在脾脏、消化道和皮肤中表达，TRHR2 在睾丸、卵巢和鳃中表达。TRHR3 在各种组织中广泛表达。这些结果表明，在青鳉中，TRH 可能通过在每个组织中表达的不同 TRHR 亚型发挥多种功能。
