猪肝脏IGF1基因表达调控机制研究

Insulin-like growth factor 1 (IGF1), produced by the liver, is an endocrine hormone, and mediates the effects of growth hormone (GH). Expression of IGF1 gene in pig liver is dramatically increased after birth. Although the function and expression pattern of IGF1 gene in pig liver in realized by us, the regulation of its expression and mechanism of the expression pattern shift remain unknown. In our previous study, we examined the expression pattern of liver-derived IGF1 and found it associated with liver C/EBP β expression pattern in porcine liver during embryonic and postnatal development. Both IGF1 and C/EBP β expression in liver maintained at low levels before birth and increased after birth. Correspondingly, C/EBP β demonstrated high binding activity to two sites at IGF1 promoter region in liver after birth. In addition, IGF1 expression can be activated by C/EBP β overexpression in porcine primary hepatocytes. In this project, we plan to examine the direct combination of C/EBP β and the promoter of IGF1 gene in vitro by the means of EMSA and mutation of the promoter, and design more experiments to verify the hypothesis that C/EBP β is a transcriptional factor of IGF gene. In the other hand, we will look for the candidate key molecules which regulates the expression of C/EBP β in pig liver by genome and epigenome techniques. The findings may contribute to a better understanding of the regulation of IGF1 expression in mammalian liver, and may help to develop new techniques for porcine growth and bring us new horizon for human clinical treatment of growth failure.

猪肝脏表达的IGF1是一种内分泌因子，介导生长激素对机体生长发育的调控。虽然人们已认识到猪肝脏IGF1的重要功能与发育性表达规律（出生后表达水平急剧上升），但其表达调控的机制一直未能阐明。项目组前期研究发现，IGF1基因的7个候选转录因子中仅CCAAT 增强子结合蛋白β(C/EBP β)出生前后的表达模式与IGF1一致；ChIP试验证实C/EBP β能够与IGF1启动子结合，上调靶基因表达，并且过表达C/EBP β促进了IGF1表达。本项目计划采用电泳迁移率分析、启动子突变等技术检测体外C/EBP β与IGF1启动子的直接结合，为证明C/EBP β是IGF1基因的转录因子提供充分的证据；另一方面采用基因组学和表观组学等技术筛选调控C/EBP β表达的候选关键分子。项目研究结果将增加人们有关哺乳动物肝脏IGF1表达调控的知识，为畜牧生产促生长技术的发展与人类矮小症的临床治疗提供有价值的参考。

猪肝脏表达的IGF1是一种内分泌因子，介导生长激素对机体生长发育的调控。猪肝脏IGF1具有出生前低表达，出生后高表达的显著特征，但这种表达特征的分子机制一直未能阐明。本项目试图解析猪肝脏IGF1基因的表达调控机制，主要研究结果包括：（1）证明C/EBP β是猪肝脏IGF1基因的转录调控因子，其不同发育阶段的表达差异是猪肝脏IGF1基因出生前低表达、出生后高表达的重要影响因素。（2）比较了出生前后猪肝脏mRNA与miR表达谱差异，筛选到2个靶向IGF1基因的miR，并且证明这2个miR可能参与调控了出生前后猪肝脏IGF1基因的差异表达。（3）证明猪肝脏IGF1基因的表达受到三维染色质结构的调控，并且可能有假基因和LncRNA的参与。项目研究结果丰富了人们有关哺乳动物肝脏IGF1基因表达调控的知识，并为发展动物促生长技术与人类矮小症的临床治疗提供了基础资料。