IGF-Ⅰ及其受体基因在牙鲆胚胎发育过程中的表达图式

Expression patterns of IGF-Ⅰ and its receptor genes during embryonic development of Japanese flounder

胰岛素样生长因子-Ⅰ(insulin-like growth factor Ⅰ,IGF-Ⅰ)是脊椎动物生长发育的重要调控因子,其生物学功能主要通过与其特异的膜受体(IGF-Ⅰ receptor,IGF-IR)结合而调节。因此,IGF-Ⅰ及其受体表达特征的分析对于阐述IGF系统调控的发育过程具有重要的意义。本研究采用荧光实时PCR方法,以不同发育时期的牙鲆(Paralichthys olivaceus)胚胎为材料,分析了胰岛素样生长因子-Ⅰ(IGF-Ⅰ)及其两种受体基因在鱼类胚胎发育过程中的表达图式。结果显示,牙鲆IGF-Ⅰ、IGF-IR-1和IGF-IR-2基因均有母源转录本,且各基因的表达在胚胎发育的不同阶段具有明显的发育性变化。IGF-Ⅰ基因在早期胚胎发育阶段仅有少量的mRNA存在,而合子基因的表达在晶体出现至出膜前阶段逐步增加。两种IGF-Ⅰ受体基因则展现出迥然不同的表达时序。IGF-IR-1基因在受精卵、卵裂及囊胚期的早期胚胎发育中有相对较少的转录本,至原肠期其合子基因强烈表达,且在神经胚、晶体出现、心跳和出膜前各阶段均有高量的表达;相反,IGF-IR-2基因在受精卵至原肠期的早期胚胎中有丰富的转录本,但合子基因的表达在后期胚胎形成中却相对降低,暗示了二者可能在调节牙鲆胚胎发育中起着不同的作用。

Insulin-like growth factor I （IGF-I） is an important regulator of growth and development in vertebrates, and its biological actions are mediated by binding to membrane-specific IGF-I receptors （IGF-IRs）. Therefore, the analysis of IGF-I and IGF-IR expression can help to further elucidate the role for IGF in the regulation of developmental processes. In this study, the expression patterns of IGF-I and its receptor genes during the embryonic development of Japanese flounder （Paralichthys olivaceus） were analyzed by fluorescent real-time PCR using embryos at different developmental stages. We observed that maternal transcripts of IGF-I, IGF-IR-1 and IGF-IR-2 were present in early embryos and that their expression is developmentally regulated at different embryonic stages. A few IGF-I mRNAs are detected in early embryos, and the zygotic IGF-I transcripts are gradually increased from the eye lens formation stage to the pre-hatching stage. IGF-IR-1 and IGF-IR-2 exhibit distinct temporal expression patterns during embryonic development. IGF-IR-1 has fewer transcripts than IGF-IR-2, and these appear at the fertilized egg, cleavage and blastula stages. The zygotic IGF-IR-1 transcripts are abundantly expressed at the gastrula stages and maintain a high level at the neurula, eye lens formation, heart beating and pre-hatching stages. By contrast, the considerable transcripts of IGF-IR-2 are detected as early as the fertilized egg through to the gastrula stage, but the zygotic IGF-IR-2 transcripts decrease significantly following embryogenesis. This indicates that the two IGF-I receptors might play different functional roles during embryonic development of Japanese flounder.