Cloning of a full-length insulin-like growth factor-I complementary DNA in the goldfish liver and ovary and development of a quantitative PCR method for its measurement

Five forms of insulin-like growth factor-I (IGF-I) complementary DNA (cDNA) were isolated by PCR from goldfish liver and ovary, using primers based on common carp IGF-I sequence. In the goldfish liver, we cloned and sequenced three IGF-I forms (1, 2, and 3), and elucidated the full-length cDNA sequence using the 5'- and 3'-RACE. Two IGF-I forms (1 and 2) were cloned from the goldfish ovary and were found to have diffences with respect to both size and nucleotide sequence compared to liver IGF-I. The entire liver IGF-I form 1 sequence was found to be 833 nucleotides long, containing a 483-nucleotide open reading frame encoding 161 amino acids. The deduced amino acid sequence of the mature peptide was compared to IGF-I sequences of other vertebrates, and found to have 97 and 93% similarity to carp and salmon IGF-I, respectively. In this study we also developed a competitive quantitative PCR method and demonstrated an increase in IGF-I expression following treatments with growth hormone or gonadotropin-releasing hormone in the goldfish liver. (C) 1998 Academic Press.