Key Laboratory of Aquatic Genetic Resources and Utilization, Shanghai Ocean University, Huchenghuan Road 999, Shanghai 201306, China.
Gene. 2011 Jan 1;470(1-2):46-52. doi: 10.1016/j.gene.2010.10.003. Epub 2010 Oct 14.
Insulin-like growth factor 2 (IGF2) is a potent mitogenic and survival factor involved in the regulation of growth, development and reproduction in animals. Only one IGF2 gene exists in mammals. Recently, two igf2 genes have been identified in zebrafish, which presumably resulted from gene duplication. However, sequence information of duplicated igf2s and their functional regulation in other teleost fish is still unknown. Here, we report the identification of two igf2 cDNAs in grass carp, Ctenopharyngodon idellus. Like their human ortholog, grass carp igf2a and igf2b mRNAs encoded two structurally distinct mature IGF peptides. Both of them were detected by RT-PCR throughout embryogenesis. Ubiquitous expression of igf2b mRNAs was observed in embryos, whereas igf2a mRNAs were expressed mainly in the notochord and brain with in situ hybridization. In adult fish, igf2b mRNAs were transcribed in multiple tissues, whereas igf2a mRNAs were detected mainly in the liver. Hepatic levels of igf2a and igf2b transcripts were both up-regulated by growth hormone injection. Furthermore, the levels of hepatic igf2a and igf2b mRNAs decreased significantly during starvation and were rebounded rapidly after re-feeding. Our results suggest that duplicated igf2 genes have evolved divergent yet played an overlapping biological role in regulating grass carp growth and development.
胰岛素样生长因子 2（IGF2）是一种有效的有丝分裂原和存活因子，参与动物的生长、发育和繁殖调节。哺乳动物中只有一个 IGF2 基因。最近，在斑马鱼中发现了两个 igf2 基因，推测是由于基因复制产生的。然而，其他硬骨鱼中重复 igf2 基因的序列信息及其功能调节仍然未知。在这里，我们报道了草鱼（Ctenopharyngodon idellus）中两个 igf2 cDNA 的鉴定。与人类同源物一样，草鱼 igf2a 和 igf2b mRNAs 编码两种结构不同的成熟 IGF 肽。它们都通过 RT-PCR 在整个胚胎发生过程中被检测到。igf2b mRNAs 在胚胎中广泛表达，而 igf2a mRNAs 主要在脊索和脑中通过原位杂交检测到。在成鱼中，igf2b mRNAs 在多种组织中转录，而 igf2a mRNAs 主要在肝脏中检测到。生长激素注射可上调肝 igf2a 和 igf2b 转录本的水平。此外，饥饿期间肝 igf2a 和 igf2b mRNAs 的水平显著下降，在重新喂食后迅速反弹。我们的结果表明，重复的 igf2 基因在调节草鱼生长和发育方面具有不同但重叠的生物学作用。
