Abstract
ABSTRACTThe 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 < 0.05). Expression of PfIGFBP5 was induced by notching the oyster shell margin; the gene was mainly expressed in the outer epithelium of the mantle, and to a lesser extent in the whole pearl sac, including connective tissues. These findings suggest that PfIGFBP5 is very likely to be involved in modulating biomineralization in the mantle and pearl sac of P. fucata since they are the main organs for shell or pearl formation.
Highlights
The insulin-like growth factor (IGF) family is one of the most widely distributed peptide families in animals, including invertebrate species (Renteria et al 2008)
Sequence analysis indicated that PfIGFBP5 has a putative signal peptide (1-21 aa) in the Nterminal region
A CGCCXXC motif was present in P. fucata rather than the typical GCGCCXXC motif of insulin-like growth factor binding protein (IGFBP)
Summary
The insulin-like growth factor (IGF) family is one of the most widely distributed peptide families in animals, including invertebrate species (Renteria et al 2008) These peptides play pivotal roles in regulating growth, development, metabolism, and reproduction (Lardans et al 2001; Riehle and Brown 2002; Schlueter et al 2007). The mantle and pearl sac are associated with shell and pearl formation, a process of biomineralization in P. fucata. Shell and pearl formation involve a series of cell growth and differentiation stages. It is unclear whether any IGFBP is involved in the regulation of the pearl sac and mantle tissue growth and/or biomineralization. Our results provide an insight into the functions of pfIGFBP5 in biomineralization
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