Molecular cloning, expression analysis and cellular localization of an LFRFamide gene in the cuttlefish Sepiella japonica

Neuropeptides are important regulators of physiological processes in metazoans, such as feeding, reproduction, and heart activities. In this study, an LFRFamide gene was identified from the cuttlefish Sepiella japonica (designated as SjLFRFamide). The full-length sequence of SjLFRFamide cDNA has 841 bp, and the open reading frame contains 567 bp encoding 188 amino acids, which shared high similarity with precursor SOFaRP2 from Sepia officinalis. The deduced SjLFRFamdie precursor protein contains a signal peptide and four different FLPs (FMRFamide-like peptides): one pentapeptide (TIFRFamide), two hexapeptides (NSLFRFamide and GNLFRFamide) and one heptapeptide (PHTPFRFamide). Multiple sequence alignment showed that SjLFRFamide contains rather conserved mature peptides, which all ended in FRF. The phylogenetic analysis suggests that SjLFRFamide belongs to the LFRFamide subfamily. The tissue distribution analysis through quantitative real-time PCR method showed that SjLFRFamide mRNA is significantly expressed in the brain, and slight trace are detected in female nidamental gland and accessory nidamental gland. In situ hybridization assay of the brain indicated that SjLFRFamide is transcribed in several different functional lobes, suggesting SjLFRFamide might associate with multiple physiological regulations, such as feeding, chromatophore regulation and reproduction. This is the first study describing LFRFamide in S. japonica, which might have great importance for cuttlefish artificial breeding.