Sequencing of Insulin-Like Growth Factor I in the Beluga, Huso huso and evaluation of its Expression in Different Tissues

Insulin-like growth factor I, IGF-I, plays important roles in different biological activities in fish. The present study was aimed at isolating cDNA encoding IGF-I and measuring relative gene expression levels in different tissues in the beluga, Huso huso one of the most important Iranian sturgeon. A fragment of 1229 nucleotides coding for IGF-I was cloned (AB512770.1) from liver using RACE-PCR. It included 483 nucleotides encoding sequences for deduced IGF-I protein (BAH85795.1). Deduced IGF-I involved 160 amino acids and included both the signal peptide and the proIGF-I. The proIGF-I consisted of B, C, A, D and E domains. Comparison of IGF-I in beluga and some animal species from different phyla showed high similarity especially with birds. Expression levels of IGF-I were analyzed in stomach, gill, liver, spleen, kidney, muscle, skin, intestine, heart and brain using real-time PCR. The results showed that although IGF-I expressed in all analyzed tissues, the highest IGF-I transcript levels were in the liver and intestine tissues. The lowest transcript level was measured in the muscle. The results of the present study can help scientists evaluate different aspects of molecular physiology in the beluga