Molecular cloning of insulin-like growth factor-I complimentary DNA and promoter region in the domestic duck (Anas platyrhynchos)

Complementary DNA (cDNA) and the flanking region of insulin-like growth factor-I (IGF-I) of domesticated duck were cloned. The nucleotide sequence analysis of the cDNA showed seven and eight bases different, respectively, from chicken and turkey IGF-I cDNA within the coding region. The amino acid sequence of prepro IGF-I differed by one and two amino acids from those observed in chicken and turkey, respectively. However, no amino acid substitution was observed in the mature IGF-I region. Sequence analysis of the promoter region and exon 1 of the duck IGF-I revealed a high degree of similarity to that of the chicken IGF-I gene. These results suggest that the mechanisms which regulate expression of the IGF-I gene may be widely conserved in avian species.