类胰岛素生长因子(IGFs)在斜带石斑鱼胚胎及卵巢的表达

Expression analysis of insulin-like growth factors′ (IGFs) in embryo and oocyte of Epinephelus coioides

生殖和生长是生物体最基本的特征,两者既密切相关又相互区别,IGFs是生长轴和生殖轴相交联的关键因子。自IGFs在鱼类卵巢的表达被发现后,它们在卵巢的功能开始备受关注,大量的研究表明它们参与了鱼类的性腺发育和成熟进程。氨基酸序列同源性比对表明:IGF-3具有IGF家族成员典型的结构特征,相对IGF-1和IGF-2基因的高保守性,IGF-3基因保守性差。本研究用半定量和荧光定量PCR技术检测了IGF-1、IGF-2和IGF-3mRNA在斜带石斑鱼胚胎发育及人工诱导性逆转过程中的表达模式。对胚胎发育的半定量结果显示:IGF-1在斜带石斑鱼胚胎发育过程中仅有微弱表达,IGF-2自桑椹期开始表达,在桑椹期后期呈现持续高水平的表达态势,预示IGF-2对胚胎发育有着重要作用;IGF-3自未受精卵开始,随着胚胎发育表达水平不断提高,但表达量不如IGF-2丰富,暗示了IGF-3可能在胚胎发育进程中扮演某种角色。利用甲基睾丸酮MT埋植鱼体腹腔,诱导性逆转,荧光定量PCR结果显示:IGF-1和IGF-3在斜带石斑鱼性逆转过程中的表达量都显著性降低,而IGF-2却没有显著变化,表明不同IGFs因子在雌性和雄性的生理功能存在性别差异。

Reproduction and growth,the most basic characteristics of organism,are closely related to and distinguished from each other.Insulin-like growth factors(IGFs)are the key factors conjuncting growth and reproduction axis.Recent researches showed that gonad development and maturation were associated with cell differentiation and tissue growth,and traditional growth factors IGF-1,IGF-2 and a recently discovered IGF subtype(IGF-3)played an important role on embryo and oocyte of fish.Our results showed that,although the IGF-3 sequence was phylogenetically distinct from the conventional IGF-1 and IGF-2 sequences in Epinephelus coioides,the three kinds of IGF maintained a similar overall protein tertiary structure,as shown in the protein structure prediction of IGFs sequences.Homology comparison of amino acid sequences also showed that E.coioides IGF-3 had typical structural characteristics of IGF family members,and was less conservative than E.coioides IGF-1 and IGF-2 genes.In fact all the IGF sequences possess six conserved cysteines which will presumably form disulfide bonds to further stabilize the protein tertiary structure.To test the IGFs expression of E.coioides in embryonic development phage,semi-quantitative RT-PCR was performed and the results showed that IGF-1 and IGF-3 mRNA expressed low in early embryonic development phage,but the expression of IGF-2 mRNA was rising gradually,along with the embryo development,implying that IGF-2 might play an important role during embryogenesis.We further tested IGFs expression after methyl testosterone implantation,along with sex reversal,and the result showed that MT inhibited significantly the expression of IGF-1 and GF-3,while the IGF-2 mRNA expression had no significant change.This study provided a theoretical basis for the endocrine regulation in E.coioides.