Identification of a second insulin-like growth factor in a fish species.
An internal portion of insulin-like growth factor (IGF) amplified from the total cDNA of rainbow trout (Oncorhynchus mykiss) liver by a PCR was used to screen a rainbow trout liver cDNA library, and recombinant clones encoding two distinct IGFs were isolated. On the basis of a 98.7% nucleotide and 98.3% predicted amino acid identity to coho salmon IGF-I, one cDNA sequence was identified as rainbow trout preproinsulin-like growth factor I (rtIGF-I). The second cDNA sequence shared 46.1% and 43.3% identity with rtIGF-I at the nucleotide and predicted amino acid levels, respectively, and was identified as rainbow trout preproinsulin-like growth factor II (rtIGF-II). Predicted amino acid sequence comparisons of rtIGFs with those of human IGFs indicate that rtIGF-I is more similar to human IGF-I than to human IGF-II, and that rtIGF-II is more similar to human IGF-II than to human IGF-I. Southern blot analysis of rainbow trout genomic DNA probed with rtIGF-I and -II cDNA suggests that these two forms of IGF originate from separate genes. The presence of a teleost IGF-II suggests that the divergence of IGFs occurred early in vertebrate evolution.
Shamblott
M J
MJ
Center of Marine Biotechnology, University of Maryland, Baltimore 21202.
Chen
T T
TT
D000199:Actins / Q000235:genetics; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D015139:Blotting, Southern; D003001:Cloning, Molecular; D003062:Codon / Q000235:genetics; D004247:DNA / Q000235:genetics / Q000302:isolation & purification; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000235:genetics*; D007335:Insulin-Like Growth Factor II / Q000235:genetics*; D008099:Liver / Q000502:physiology; D008969:Molecular Sequence Data; D016133:Polymerase Chain Reaction / Q000379:methods; D015183:Restriction Mapping; D017386:Sequence Homology, Amino Acid; D012689:Sequence Homology, Nucleic Acid; D014337:Trout / Q000235:genetics*
D000199:Actins; D003062:Codon; D007334:Insulin-Like Growth Factor I; D007335:Insulin-Like Growth Factor II; D004247:DNA