Abstract
Neurokinin B (NKB) is a member of the tachykinin (tac) family that plays important roles in mammalian growth by modulating prolactin (PRL) synthesis and secretion and causing contraction of the stomach and intestine. However, its potential role in regulating growth of teleosts is less clear. We aimed to explore the role that NKB plays in regulating fish growth using the spotted sea bass (Lateolabrax maculatus) as a model. In the present study, two tac3 and two tacr3 genes were identified in the spotted sea bass. Sequence analysis showed that two tac3 transcripts, tac3a and tac3b, encode four NKBs: NKBa-13, NKBa-10, NKBb-13, and NKBb-10. Expression analysis in different tissues showed that both genes are highly expressed in the brain, stomach and intestine of the spotted sea bass. In situ hybridization indicated that the tac3a and tac3b mRNAs are both localized in several brain regions, such as the telencephalon and hypothalamus, and that tacr3a and tacr3b are localized in the intestinal villus and gastric gland. To investigate the potential role of NKBs in regulating growth, in vitro experiments were performed to detect the effect of NKBs on growth-related gene expression in the brain and brain-gut peptide (BGP)-related genes in the stomach and intestine. NKBb-13 was the most critical ligand in regulating the expression of growth-related genes in the brain and brain-gut peptide (BGP)-related genes in the stomach. The expression of cholecystokinin (cck) was enhanced by NKBa-13, NKBa-10, and NKBb-10 but not NKBb-13 in the intestine. In general, our results showed that NKBs participate in regulating the growth of spotted sea bass.
Highlights
Neurokinin B (NKB), which is encoded by tachykinin 3, is a member of the tachykinin family [1, 2]
Genomic data mining suggested that two tac3 and two tacr3 genes were present in the spotted sea bass genome
Synteny was clearly observed for tac3a and tac3b, which were closely linked to birc5b, znf385a, and clgaltla in zebrafish and apof and clgalt1b in spotted sea bass
Summary
Neurokinin B (NKB), which is encoded by tachykinin 3 (tac3), is a member of the tachykinin family [1, 2]. Gonadotropinreleasing hormone (GnRH) was believed to be the primary factor that controls the synthesis and release of luteinizing hormone (LH) and follicle-stimulating hormone (FSH) from the pituitary gonadotrophs, which guide the gonad development [10] Kisspeptins and their cognate receptor, GPR54, regulate the secretion of GnRH [11]. NKB was found to regulate reproduction by multiple pathways, including negatively modulating kisspeptin to regulate the release of GnRH1 in the striped bass [15], stimulating the release and synthesis of LH in zebrafish, tilapia and goldfish [10, 16,17,18]. These findings suggested that NKB play an important role in regulating fish reproduction
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