榕江香猪生长激素基因的鉴定及功能分析

生长激素是调节动物生长的主要激素.本研究应用聚合酶链式反应技术从榕江香猪的基因组文库中分离出1.903kb生长激素基因.克隆的生长激素基因由五个外显子和四个内含子组成.榕江香猪生长激素基因的碱基序列与已知四个国外猪种和9个中国地方猪种之间的同源性为97%～99%,其间的差异主要集中在内含子2和4.通过限制性内切酶（DdeI,NarI,BsmNI）分析,鉴定出榕江香猪生长激素基因的五个多态性位点,分别位于5＇-侧翼区274（T/C）位点,外显子2的622（G/A）和631（G/A）位点,内含子2中的841（T/C）以及外显子4中的1 358（A/G）位点.同时,1 358（A/G）位的碱基改变导致榕江香猪生长激素成熟肽第108位异亮氨酸替换,三维结构分析表明,异亮氨酸的存在可能导致生长激素与受体间亲合力降低.

Identification and function of the growth hormone gene in Rongjiang pig of China

Growth of animal is largely regulated by growth hormone (GH). In this study, the GH gene was isolated and cloned from the genomic DNA library from Rongjiang pig, a Chinese local swine, using polymerase chain reaction technique. The complete nucleotide sequence of a 1.903 kb genomic fragment containing Rongjiang swine GH gene has been determined. The GH gene contained five exons and four introns similar to the GH genes of other mammalians and exhibited 97%~99% identity to the GH genes of the four western meat-type breeds and nine Chinese local pigs. Polymorphism of GH genes was analyzed by using the restriction enzymes Dde I, Nar I and BsmN I in four western meat-type breeds and ten Chinese local pigs. Five polymorphic restriction sites, with Dde I at the base 622 (G/A) in exon 2 and 274 (T/C) in 5o-flank, with Nar I at 631 (G/A) in exon 2, and with BsmN I at the base 841 (T/C) in intron 2 and 1358 (A/G) in exon 4, were identified. The polymorphic restriction site at 1358 (A/G) leaded to the GH mature protein of Rongjiang pig differing from that of four western meat-type breeds and eight Chinese local breeds at the residue Val108 substituted by Ile108. According to the crystal structure of human GH mature protein, this Ile108 substitution might result in a lower affinity of GH for its receptor in Rongjiang breed.