Cloning And Tissue Expression Of Insulin-like Growth Factor Ⅱ Gene In Carassius Auratus

Insulin-like growth factors â…¡(Igf2), also known as somatomedin A, is a single chain polypeptides which shares homology with insulin-like growth factors â… (Igf1) in amino acid sequences. Both Igf2 and Igf1 are homologues to proinsulin. Igf2 is a factor that is of great importance to cell proliferation, differentiation and apoptosis. It is also vital to ontogeny and development. In mammalians, Igf2 is an imprinted gene and the abnormal imprinting of it is relative to many diseases such as cancers and growth disorders. Thus, many researches have been done on this gene and a lot of progress has been made.Recently, it was found that in the gynogenetic haploid and diploid embryos of goldfish, which have exactly the same genome, the haploid condition results in obstruction of gene expression and abnormal development while the diploid embryos have normal gene expression and development. Then we extracted the total proteins of both the gynogenetic haploid and diploid embryos of goldfish in the same eye formation stage. It is demonstrated that Igf2 is one of the significantly different gene expressions during embryos developing between diploid and haploid. So, through further investigation of Igf2 imprinting situation in goldfish, we may find a diploid-dependent regulatory mechanism of gene expression and the relationship between the mechanism and gene imprinting of mammalian.The coding sequences of Igf2 have been reported in many mammalians, a few birds, amphibian and osteichthyes. But it has not been reported in goldfish. In our investigation, goldfish's insulin-like growth factor â…¡ gene clone was obtained by PCR. Sequence analysis showed thatthe genomic structure of Igf2 is composed of four exons and three introns and the entire open reading frame of Igf2 is 606bp, which was predicted to encode a protein of 201 amino acids. Homology between goldfish and zebrafish was 85% at the nucleotide level and 80.9% at the protein level. nxRNA detection analysis with RT-PCR revealed that Igf2 expressed in goldfish's gill, heart, kidney, muscle, tail fin, male and female gonads.