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Leptin为肥胖基因编码产物,是脂肪细胞分泌的蛋白质类激素,在能量平衡、摄食行为调节方面起着重要作用。采用RT-PCR法分离出了吉富罗非鱼(Oreochromis niloticus)leptin基因的部分序列,其cDNA长度为364 bp,编码96个氨基酸。同源性分析显示:鱼类leptin保守性较低。吉富罗非鱼leptin氨基酸序列与斜带石斑鱼(Epinephelus coioides)的相似性较高,为80.6%,但与虹鳟(Oncorhynchusmykiss)、青鳉(Oryzias latipes)、斑马鱼(Danio rerio)等其他鱼的相似性非常低,均在40%以下。使用realtime PCR法检测leptin在各种组织中的表达量,结果发现,leptin在肝中相对表达量最为丰富,是肌肉中相对表达量的3 000倍,其次为性腺和脑,分别是肌肉中相对表达量的1 250倍和450倍,而肾、肠和肌肉中表达量较少。
Leptin, a gene encoded by obese genes, is a protein hormone secreted by fat cells and plays an important role in energy balance and regulation of feeding behavior. The partial sequence of leptin gene of Oreochromis niloticus was isolated by RT-PCR. The cDNA was 364 bp in length and encoded a protein of 96 amino acids. Homology analysis showed that fish leptin was less conserved. The similarity of leptin amino acid sequence with that of Epinephelus coioides was 80.6%, but not with other fish such as Oncorhynchus mykiss, Oryzias latipes, Danio rerio The similarity is very low, both below 40%. The real-time PCR method was used to detect the expression of leptin in various tissues. The results showed that leptin was the most abundant in the liver, which was 3000 times of the relative expression in muscle, followed by the gonads and brains, which were the relative 1 250-fold and 450-fold higher expression levels, while less expression was found in kidney, intestine and muscle.