gBTN1A1基因的筛选、克隆及序列分析

利用抑制消减杂交技术研究西农萨能羊泌乳中期和末期的乳腺组织差异表达基因，构建消减文库，得到山羊嗜乳脂蛋白的部分序列，根据牛和绵羊基因组序列进行电子拼接，设计引物，得到山羊嗜乳脂蛋白的CDs区全序列，应用RT-PCR技术从山羊乳腺组织总RNA中扩增克隆了山羊嗜乳脂蛋白基因CDs区，命名为gBTN1A1,并登录Genbank（EF102891）。gBTN1A1全基因由7个外显子和6个内含子组成，开放读码框由1581个碱基,编码526个氨基酸，gBTN1A1基因核苷酸序列与牛、人和鼠的同源性为97%, 88%, 84%，蛋白质序列的同源性为96%, 84% and 70%。其二级结构、跨膜区域及信号肽分析与牛、人和鼠相似，所以推测gBTN1A1与乳脂肪球的分泌密切相关，根据其在泌乳期表达丰度的差异推测其可能影响山羊产奶量。

Screening, Cloning and sequence analyzing of gBTN1A1 gene

Suppression subtractive hybridization was used to compare gene expression of middle versus late lactation of Xinong Saanen Goat mammary gland, and the goat butyrophilin(gBTN1A1) gene was screened form subtracted cDNA library of difference expressed genes. After electrical spilicing, The gBTN1A1 gene was amplified and cloned from total RNA of goat mammary gland by RT-PCR , and Registered in Genbank. Sequence analysis indicated that the gBTN1A1 complementary DNA that contained an open reading frame of 1581 nucleotides encoding a putative protein of 526 amino acids was identified. The whole DNA sequence includes 7 exons and 6 introns and amino acids through 1-26 constitute the signal peptide domain. The homologies of nucleotide and peptide sequence of the butyrophilin with bovine (NM_174508), human (NM_001732) and mouse’s (AK145168) are 97%, 88%, 84%，96%, 84% and 70%, respectively. The predicted structure of gBTN1A1 was similar to that of bovine and human, although some differences exist in transmembrane domain and hydrophilicity among them. Our results suggested that the goat mammary gland mRNA level of gBTN1A1 was not only responsible for milk fat globule secretion, but also for milk yield.