TAC3 Gene Products Regulate Brain and Digestive System Gene Expression in the Spotted Sea Bass ().

Neurokinin B (NKB) is a member of the () 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 () as a model. In the present study, two and two genes were identified in the spotted sea bass. Sequence analysis showed that two transcripts, and , 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. hybridization indicated that the and mRNAs are both localized in several brain regions, such as the telencephalon and hypothalamus, and that and are localized in the intestinal villus and gastric gland. To investigate the potential role of NKBs in regulating growth, 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 () 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.