Cloning,tissue expression of three somatostatin genes of Siniperca chuatsi and their localizations in brain

Somatostatins(SS)play important physiological functions in vertebrate’s growth and development,which belong to a multiple gene family.In this study,the complete cDNA sequences of three distinct preprosomatostatins(PSSⅠ,PSSⅡand PSSⅢ)were isolated from Siniperca chuatsi brain and cloned by means of rapid amplification of cDNA ends(RACE).The full length of PSSⅠ cDNA was 647 bp,which contained 369 bp open reading frame and encoded 122 amino acids with a signal peptide of 26 amino acids.It contained the conservative SS-14 sequence at the C-terminal extremity,which is identical with that of other vertebrates.The full length of PSSⅡ cDNA was 655 bp,which contained 387 bp open reading frame and encoded 128 amino acids with a signal peptide of 25 amino acids.It contained［Tyr⁷,Gly¹⁰］SS-14 at the C-terminal extremity.The full length of PSSⅢ cDNA was 823 bp,which contained 333 bp open reading frame and encoded 110 amino acids with a signal peptide of 21 amino acids.It contained［Pro²］SS-14 at its C-terminal extremity.PSS mRNA expressions in different adult tissues were analyzed by RT-PCR technique.All PSS mRNA were found in brain,while PSSⅠ mRNA wasn’t detected in other peripheral tissues,high levels of PSSⅡ mRNA were also present in esophagus and stomach,PSSⅢ mRNA in kidney and gonad.These suggested that all PSSs participate in neurological regulation in brain,whereas PSSⅡ may also regulate digestion activity,and PSSⅢ regulates reproduction activity.Cellular localization of PSS mRNAs in brain was determined by in situ hybridization,PSSⅠ mRNA was expressed in hypothalamus and medulla oblongata,PSSⅡ mRNA was expressed in hypothalamus,PSSⅢ mRNA was expressed in hypothalamus,optic tectun,medulla oblongata and spinal cord.All PSS mRNA were detected in the hypothalamus,which showed they could be involved in hypothalamic-pituitary regulation.Distinct expression in other brain sections suggested somatostatins may also act as neurotransmitters or hormones,and exhibit different biological effects.