Molecular cloning and expression profiles of an insulin-like growth factor binding protein IGFBP5 in the pearl oyster, Pinctada fucata

The insulin-like growth factor binding protein (IGFBP) family participates in transportation, localization, and biological regulation of insulin-like growth factors (IGFs). In the present study, IGFBP5 gene from the Pinctada fucata (PfIGFBP5) was cloned and characterized. The full-length cDNA sequence (1319 bp) contained an open reading frame of 399 bp encoding a predicted protein of 132 amino acids. The amino acid sequence of PfIGFBP5 included an IGF binding domain and multiple cysteine residues. The genomic sequence of PfIGFBP5 consisted of three exons and two introns. PfIGFBP5 was found to be expressed in all tissues and developmental stages investigated, although the expression level was significantly higher in the pearl sac and in trochophore larvae than in other tissues or developmental stages (P