生长轴对半滑舌鳎早期生长发育的调控作用

Physiological role of the growth axis in embryonic development and early growth of Cynoglossus semilaevis

为深入了解生长轴(GH/IGF axis)对半滑舌鳎(Cynoglossus semilaevis)生长发育的调控作用,采用定量PCR方法研究了GH/IGF轴5个关键生长因子(GH、GHR1、GHR2、IGF-I、IGF-II)在配子、胚胎发育和仔稚幼鱼生长过程中的差异表达调控特性。结果显示,这5个生长因子都具有亲本遗传的特性,除GH外,精子中其他4个生长因子转录表达水平均显著高于卵子。在胚胎发育阶段, GH mRNA在胚胎发育各时期均有表达,且在细胞分裂初期和孵化期表达水平较高。GHR1和GHR2mRNA在胚胎发育各时期呈现相似的表达水平变化趋势,除囊胚期和原肠胚期外, GHR1 mRNA的表达量均高于GHR2。IGF-I和IGF-II mRNA在胚胎发育各时期均表达, IGF-I在孵化期表达水平最高, IGF-II在胚体下包2/3期和孵化期表达水平最高。除64细胞期和128细胞期外, IGF-II mRNA的表达量均显著高于IGF-I (P<0.05)。在仔稚幼鱼生长阶段, GH mRNA表达水平从孵化后3 d开始显著升高,到6 d时达峰值。GHR1 mRNA表达水平自6 d开始显著升高(P<0.05),到30 d达峰值。GHR2 mRNA在3 d、20 d、25 d、30 d和60 d均处于显著高表达水平(P<0.05)。IGF-I mRNA在3 d表达水平最高, IGF-II mRNA从6 d开始显著上调表达,并保持较高表达水平至45 d, IGF-II mRNA表达量均显著高于IGF-I (P<0.05)。偏相关分析发现:这5个生长因子通过正向协同或负向拮抗作用在半滑舌鳎胚胎发育和仔稚幼鱼生长过程中共同起调控作用。研究结果为深入了解GH/IGF轴对鱼类生长调控机制积累了新的素材。

In order to understand the physiological role of the growth axis(GH/IGF axis) in embryonic development and early growth of Cynoglossus semilaevis, a quantitative PCR method was used to study the differential expression patterns of five key growth factors(GH, GHR1, GHR2, IGF-I, and IGF-II) along the growth axis during early life stages. The results showed that these five growth factors could all be genetically inherited from parents, and they all exhibited significantly higher paternal expression levels, except for GH. GH mRNA was detected in all embryonic development stages, but the highest expression level was observed at the 2-cell stage and hatching stage. GHR1 and GHR2 mRNA levels showed similar expression patterns during embryonic development stages, and there were significantly higher expression levels of GHR1 mRNA than that of GHR2 during all embryonic development stages, except in the morula and gastrula stages. IGF-I and IGF-II mRNA were both detected during all embryonic development stages, and the highest expression level of IGF-I mRNA was observed at the hatching stage. IGF-II mRNA levels peaked at the embryo encircling 2/3 of yolk sac and hatching stages. During the larval and juvenile development stages, GH mRNA expression level increased significantly from 3 d post hatching and peaked at 6 d. The GHR1 mRNA expression level increased significantly from 6 d and reached the maximum level at 30 d. GHR2 mRNA level significantly increased at 3 d, then gradually decreased to a lower expression level at 15 d, but then showed a significantly higher level from 20 d to 30 d, and also at 60 d. The expression level of IGF-I mRNA was the highest in 3 d larvae, and for IGF-II mRNA, there was significantly increased expression from 6 d, which was maintained at a high level until 45 d. The IGF-II mRNA level was significantly higher than that of IGF-I during the larval and juvenile stages. Correlation analysis showed that these growth factors play positive synergistic or negative antagonistic regulatory roles in the embryonic development and early growth stages. The results showed that the GH/IGF axis plays an important physiological role in regulating the embryonic development and early growth of Cynoglossus semilaevis, and provide new clues and materials for better understanding the role of the GH/IGF axis in fish growth.