大黄鱼(Pseudosciaena crocea)leptin和cholecystokinin基因的克隆和表达特性研究

摘要

本文克隆了两种大黄鱼(Pseudosciaena crocea)摄食调控因子胆囊收缩素(CCK)、瘦素(LEP)基因的全长序列,并对其表达特性进行了研究.结果表明,克隆得到CCK基因属硬骨鱼类的CCK1亚家族,全长900nt,编码137个氨基酸,与其他鱼类的CCK1相比序列组成非常保守,特别是在20氨基酸的信号肽和8个氨基酸的CCK-8活性结构区域;而克隆得到LEP基因属硬骨鱼类的LEPA亚家族,全长1290nt,编码161个氨基酸,与其他鱼类LEP相比基因同源性较差,但在3D结构上却保留了LEP经典的4个α螺旋特征.两种因子在所检测的所有组织中均有表达,但尤以脑、胃、肠消化道、肝脏等摄食及能量平衡相关组织中表达活性最高.8天的饥饿能使大黄鱼脑、消化道组织的CCK和肝脏、脂肪组织中的LEP表达显著降低(P＜0.05).该结果说明CCK和LEP可能在大黄鱼的摄食生理和能量平衡中起着重要的调控作用;本研究将为深入了解鱼类食欲调控的神经内分泌机理提供基础.%cDNAs encoding for two feeding regulation factors,cholecystokinin (CCK) and leptin (LEP),were cloned in large yellow croaker Pseudosciaena crocea,mRNA tissue distribution was examined for the two peptides,as well as the effects of 8-day fasting on their expression.The results show that large yellow croaker CCK sequences displayed identity with that of teleost CCK1 gene sub-family.It is a 900bp nucleotide sequence,encoding a peptide composed of 137 amino acids.The sequences displayed great identity with the teleost CCK1 gene,especially within the segments of signal peptide and cck-8 sequences.In contrast,large yellow croaker LEP displayed less identity with other teleost LEP gene,but kept a classic LEP 3D structure formed by four-helix bundle.It is a 1290bp nucleotide sequence,which encodes a peptide composed of 161 amino acids.The sequences displayed identity with teleost LEPA gene sub-family.Both peptides are present in all tissues examined,but only abundant in the feeding regulation tissues,such as brain,gastrointestinal tract,and other peripheral tissues,including liver.The 8-day fasting induced a significant decrease in both brain and gut CCK,and liver and mesenteric fat LEP mRNA expression (P＜0.05).Therefore,the CCK and LEP played possibly a role in feeding regulation and digestive processes in large yellow croaker.The present results provide a basis for further investigation into the neural and gastroenteric mechanisms regulating appetite in large yellow croaker.