Filby Amy L, Tyler Charles R
Environmental and Molecular Fish Biology Group, School of Biosciences, Hatherly Laboratories, University of Exeter, Prince of Wales Road, Exeter, Devon EX4 4PS, UK.
Gen Comp Endocrinol. 2007 Jan 1;150(1):151-63. doi: 10.1016/j.ygcen.2006.07.014. Epub 2006 Sep 12.
Growth hormone (GH), insulin-like growth factor-I (IGF-I), thyroid hormones, and corticosteroids play central roles in a wide range of body functions but, in fish, information on their interactions is limited. These axes of the endocrine system are also potential targets for disruption of signaling pathways by hormone-mimicking chemicals, but have received little study. Molecular approaches offer an effective way to help unravel these endocrine interactions but require the appropriate gene-specific assays to do so. In this study, the cDNAs for a suite of hormones and/or receptors involved in signaling for the effects of GH and IGF-I [GH, GH receptor (GHR), IGF-I, IGF-I receptor (IGF-IR)], thyroid hormones [thyroid hormone receptor alpha (TRalpha) and beta (TRbeta)], and corticosteroids [glucocorticoid receptor (GR)] were cloned from the fathead minnow (Pimephales promelas; fhm), and the tissue-, developmental-, and gender-related expression of their mRNA transcripts established. By polymerase chain reaction (PCR) strategy, we obtained full-length 1123-bp GH, 817-bp IGF-I, 1584-bp TRbeta, and 2571-bp GR cDNAs, coding for 210 amino acid (aa) GH, 161 aa IGF-I, 378 aa TRbeta, and 745 aa GR putative proteins, and partial-length 158-bp GHR, 811-bp IGF-IR, and 446-bp TRalpha cDNAs. Real-time PCR analyses revealed broad tissue expression for the target mRNAs; all targets were expressed in brain, pituitary, gill, liver, gonad, intestine, and muscle, with the exception of GH that was expressed only in the pituitary and gonad. Expression patterns in both juvenile and adult fhm were complex, with both temporal-, tissue-, and sex-specific characteristics. For example, hepatic expressions of GHR, IGF-I, and IGF-IR were far higher in males than in females, possibly reflecting the sex-related dimorphism in growth that occurs in this species, and TRalpha and TRbeta showed divergent expression patterns during development (where TRbeta predominated) and in adult tissues implying some distinct roles for the two TR subtypes.
生长激素（GH）、胰岛素样生长因子-I（IGF-I）、甲状腺激素和皮质类固醇在多种身体功能中发挥核心作用，但在鱼类中，关于它们相互作用的信息有限。内分泌系统的这些轴也是激素模拟化学物质干扰信号通路的潜在靶点，但相关研究较少。分子方法为帮助揭示这些内分泌相互作用提供了一种有效途径，但需要合适的基因特异性检测方法。在本研究中，从黑头呆鱼（Pimephales promelas；fhm）中克隆了一系列参与GH和IGF-I作用信号传导的激素和/或受体的cDNA [GH、GH受体（GHR）、IGF-I、IGF-I受体（IGF-IR）]、甲状腺激素[甲状腺激素受体α（TRα）和β（TRβ）]以及皮质类固醇[糖皮质激素受体（GR）]，并确定了它们mRNA转录本的组织、发育和性别相关表达。通过聚合酶链反应（PCR）策略，我们获得了全长1123 bp的GH、817 bp的IGF-I、1584 bp的TRβ和2571 bp的GR cDNA，分别编码210个氨基酸（aa）的GH、161 aa的IGF-I、378 aa的TRβ和745 aa的GR推定蛋白，以及部分长度158 bp的GHR、811 bp的IGF-IR和446 bp的TRα cDNA。实时PCR分析显示目标mRNA在广泛的组织中表达；所有目标在脑、垂体、鳃、肝、性腺（精巢）、肠和肌肉中均有表达，但GH仅在垂体和性腺（精巢）中表达。幼年和成年fhm的表达模式都很复杂，具有时间、组织和性别特异性特征。例如，GHR（生长激素受体）、IGF-I和IGF-IR的肝脏表达在雄性中比雌性高得多，这可能反映了该物种生长过程中与性别相关的二态性，并且TRα和TRβ在发育过程中（TRβ占主导）以及成年组织中表现出不同的表达模式，这意味着两种TR亚型具有一些不同的作用。
