GHR信号通路在动物出生后的生长中扮演着重要角色.实验利用斑马鱼模型研究了GHR信号相关基因在成体组织、胚胎发育以及幼体期的表达情况,这些基因包括gh、ghra、ghrb、jak2a、jak2b、statS.1、stat5.2、igf1、c-fos、socsl和socs2.值得关注的是,上述的大部分基因都存在母源性表达,且它们的合子表达均起始在体节早期之前.这说明在有功能性的脑垂体形成之前和完善的循环系统建立之前,GH及GH信号相关因子就已经存在于早期胚胎中,因此GH很可能是控制胚胎发育的一系列自分泌/旁分泌生长因子中的一员.同时,我们发现成体组织的SocS表达水平与GH信号靶基因igf1和c-fos的表达呈某种程度的负相关.我们利用实时定量PCR技术和荧光素酶分析技术,通过注射GH和GHR表达载体,在斑马鱼胚胎中分析了它们促进GH信号靶基因c-fos和igfl转录活性以及GH应激启动子spi12.1活性的能力.由此,研究利用斑马鱼胚胎建立一个体内研究模型来评估发育过程中的GH信号激活(GHSA).在受精后1天(dpf)和3dpf斑马鱼胚胎中,单独过表达gh或ghr均可以显著刺激GHSA,这表明在ldpf的斑马鱼胚胎中即存在功能性的GH和GHR蛋白表达,而这一时期是在功能性垂体的形成之前的.gh以及ghr的协同过表达则可以显著放大gh或ghr单独过表达的GHSA效果.%Growth hormone receptor (GHR) signaling pathway plays an important role in postnatal growth of animals.Although significant progress has been made in elucidating the signaling pathways activated by GHR in recent years,a comparative expression analysis of all the GHR signaling related genes and evaluation of GH-signal activation (GHSA)in an in vivo model still remain elusive.The zebrafish (Danio rerio) is an excellent model organism to study both developmental and physiological processes.In the present study,we comparatively analyzed the expression of GHR signal related genes,such as gh,ghra,ghrb,jak2a,jak2b,stat5.1,stat5.2,igf1,c-fos,socsl and socs2 in adult tissues,and during embryonic development by means of RT-PCR.Maternal expression was found in most of them and their zygotic expression mostly started from early-somite stage,far before the differentiation of pituitary somatotrophs and before the establishment of a functional circulatory system.In adults,the tissue distribution abundance of socs mRNA was negatively correlated with the GH-signal targets,igfl and c-f os.By analyzing the transcription level ofc-fos and igfl and the promoter activity of spi2.1,in zebrafish embryos injected with different constructs,i.e.,the expression constructs of gh and ghr,we established an in vivo model to evaluate GH-signal activation (GHSA) in early development of zebrafish embryos.Overexpression of gh or ghr alone in zebrafish embryos could significantly stimulate GHSA at 1 day post-fertilization (dpf) and 3 dpf,strongly indicating the existence of functional GH and GHR proteins in zebrafish embryos from 1 dpf,far prior to the formation of functional pituitary gland.A synergetic overexpression of gh and ghr could amplify the GHSA effects ofgh or ghr overexpression.
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