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 primer s based on common carp IGF-I sequence. In the goldfish liver, we clone d and sequenced three IGF-I forms (1, 2, and 3), and elucidated the fu ll-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 diff ences with respect to both size and nucleotide sequence compared to li ver IGF-I. The entire liver IGF-I form 1 sequence was found to be 833 nucleotides long, containing a 483-nucleotide open reading frame encod ing 161 amino acids. The deduced amino acid sequence of the mature pep tide was compared to IGF-I sequences of other vertebrates, and found t o have 97 and 93% similarity to carp and salmon IGF-I, respectively. I n this study we also developed a competitive quantitative PCR method a nd demonstrated an increase in IGF-I expression following treatments w ith growth hormone or gonadotropin-releasing hormone in the goldfish l iver. (C) 1998 Academic Press.