Discovery of a novel insulin-like peptide and insulin binding proteins in the Eastern rock lobster Sagmariasus verreauxi

This study reports, for the first time in any of the commercially important decapod species, the identification of an <a href="#200019063">insulin</a>-like <a href="#200002687">peptide</a> (ILP), distinct from the <a href="#200002657">androgenic</a> gland hormone. <a href="#200023719">Bioinformatics</a> analysis of the <em>de novo</em> assembled spiny lobster, (<em>Sagmariasus verreauxi</em>) <a href="#200005736">transcriptome</a>, allowed identification of <em>Sv-ILP1</em> as well as eight binding proteins. Binding proteins were termed as <em>Sv-<a href="#200016193">IGFBP</a></em>, due to homology with the vertebrate <a href="#200016193">insulin-like growth-factor binding protein</a> and <em>Sv-SIBD1-7</em>, single insulin-binding domain protein (SIBD), similar to those identified in other invertebrate species. <em>Sv-ILP1</em> was found to be expressed in the eyestalk, gonads and antennal gland of both sexes and to a lesser extent in male muscle, androgenic gland and hepatopancreas. The expression profiles of each binding protein were found to vary across tissues, with <em>Sv-SIBD5</em>, <em>6</em> and <em>7</em> showing higher expression in the gonad, demonstrated by <a href="#200021912">PCR</a> and digital gene expression. Further spatial investigations, using <em>in-situ</em> hybridisation, found <em>Sv-ILP1</em> to be expressed in the neurosecretory cells of the <a href="#200021438">thoracic ganglia</a>, in keeping with the tissue expression of <em>Drosophila</em> ILP7 (DILP7). This correlative tissue expression, considered with the <a href="#200019980">phylogenetic</a> clustering of Sv-ILP1 and DILP7, suggests Sv-ILP1 to be a DILP7 orthologue. The broad expression of <em>Sv-ILP1</em> strongly suggests that ILPs have a role beyond that of <a href="#200013635">masculinisation</a> in decapods. The function of these novel <a href="#200002687">peptides</a> may have application in enhancing aquaculture practices in the commercially important decapod species.