水牛ABCG2基因第9外显子群体遗传特征分析

 三磷酸腺苷结合转运蛋白G超家族成员2 (ABCG2)对普通奶牛泌乳性状有直接影响。水牛中该基因的遗传特征与产奶性状间是否有遗传关联目前还不十分清楚。本文采用PCR SSCP和PCR产物直接测序相结合的技术，对4个河流型水牛群体和9个沼泽型水牛群体共计466个个体的ABCG2基因第9外显子进行了变异检测。结果表明，水牛ABCG2基因第9外显子由251个核苷酸组成，所有的河流型和沼泽型水牛序列相同，未发现SNP位点，但在第9内含子内检测到1个T>C替换(g. SNP44769 T>C)。与GenBank数据库中已发表的牛科物种同源序列比对后发现，数据库中一条河流型水牛序列该外显子第66位核苷酸处有1个G>A替换(c. SNP1018 G>A)，导致所编码的氨基酸发生p. V340I的改变；与普通牛、山羊和绵羊该基因第9外显子序列的核苷酸差异位点个数分别为5,8和11个，表明水牛与其他牛科物种间具有较大的遗传差异。本文结果提示ABCG2基因第9外显子在水牛中已纯化固定，且与水牛产奶量性状间无直接关联性。

Population Genetic Characteristics Analysis of Exon 9 of ABCG2 Gene in Water Buffalo (Bubalus bubalis)

The ATP binding cassette sub family G member 2 (ABCG2) protein plays a crucial role on the milking traits of cattle. But its population genetic characteristics and association with milk production in buffalo were unclear. In this study, ABCG2 exon 9 of 466 buffalo sampled from 4 river type and 9 swamp type populations were examined using PCR SSCP and PCR product direct sequencing techniques. The results revealed that sequences of ABCG2 exon 9 in river type and swamp type buffalo were identical, which consist of 251 nucleotides with no SNP discovered, but one T>C substitution (g. SNP44769 T>C) was detected in intron 9. Compared with published data of the bovidae species in GenBank database, one G>A substitution (c. SNP1018 G>A) was found in one river buffalo sequence and lead to the change of the 340th amino acid residues from Valine to Isoleucine (p. V340I) in ABCG2. And the numbers of nucleotide sequence differences among buffalo, cattle, goat and sheep were 5, 8, 11, respectively, which suggest that there are distinct genetic differences between buffalo and the other bovidae species. The results in the present study indicate that ABCG2 exon 9 has been fixed in buffalo and probably had no direct correlation with the trait of buffalo milk yield.