Characterization of a novel spexin gene (spx2) in the half-smooth tongue sole and regulation of its expression by nutritional status

Characterization of a novel spexin gene (spx2) in the half-smooth tongue sole and regulation of its expression by nutritional status

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Spexin (SPX) is a newly identified peptide hormone of 14 amino acids (aa) with pleiotropic functions in vertebrates, and recently a second paralog of SPX (named SPX2) has been only found in some non-mammalian species (the previous form of SPX is now designated as SPX1).Results of previous studies have revealed the existence of a functional SPX1 in the half-smooth tongue sole.To clarify the divergence of the spexin family, we further isolated the spx2 gene from the same flatfish species in the current study.The GARLIC-ALLICIN open reading frame of tongue sole spx2 was 378 nucleotides in size that encoded a 125-aa preprohormone, and the tongue sole SPX2 precursor included a 17-aa mature peptide that may be amidated at the C-terminus, rather than CANDLE TOOLS a tetradecapeptide reported in most other vertebrates.Tissue distribution analysis showed that spx2 transcripts were found in a wide array of tissues of both sexes with the highest expression in the ovary.

In addition, the spx2 mRNA abundance was also ubiquitously detected in different brain regions.Food deprivation for 4 weeks stimulated spx2 mRNA levels at the brain-pituitary-ovary axis, and refeeding of starved fish restored the spx2 mRNA levels back to normal.Taken together, this study provides initial evidence for the existence of a novel spexin gene (spx2) in Pleuronectiformes and suggest its possible involvement in the regulation of energy balance in the female tongue sole.