牦牛LPL基因组织表达及其突变与乳质性状的关联分析

Tissue expression and polymorphisms of LPL gene and their associations with milk quality traits in Yak

【目的】检测牦牛脂蛋白脂酶(lipoprotein lipase,LPL)基因在不同组织中的表达量及其突变位点,评估基因突变对甘南牦牛乳质性状的影响,丰富牦牛乳质性状分子遗传数据。【方法】采用实时荧光定量PCR(RT-qPCR)检测甘南牦牛LPL基因在不同组织中的相对表达量;应用单链构象多态性(single strand conformation polymorphism,SSCP)技术检测LPL基因在青海牦牛、天祝白牦牛、甘南牦牛、西藏牦牛及野血牦牛5个群体中的突变,应用一般线性模型分析基因突变与甘南牦牛乳质性状的相关性。【结果】甘南牦牛LPL基因在皮下脂肪和心脏中高表达,在背最长肌、乳腺、肝脏、脾脏、肾脏、大肠、小肠、皱胃、瘤胃中低表达,在肺脏中表达量最低。在5个牦牛群体LPL基因的exon 3区,exon 6区和exon 7区均未检测到多态性,在intron 2区检测到2处单碱基突变,形成M和N 2种等位基因,其中M为优势等位基因(频率为67.11%~83.21%);在exon 4-intron 4区也检测到2处单碱基突变,形成A和B 2种等位基因,其中等位基因A为西藏牦牛优势等位基因(频率为63.95%),其他4类群牦牛中B为优势等位基因(频率59.75%~69.71%)。5个类群牦牛LPL基因在intron 2区和exon4-intron 4区为中低度多态。关联分析表明,甘南牦牛LPL基因intron 2区基因型MM个体、exon 4-intron 4区基因型AB个体和两区域单倍型组合H1H2(M-A/M-B)的乳脂率、乳蛋白率及总固体物质含量均高于其他个体,且乳脂率显著高于其他个体(P<0.05)。【结论】5个类群牦牛LPL基因intron 2区和exon4-intron 4区各存在2处单碱基突变,且显著影响了甘南牦牛的乳脂率,可作为牦牛乳脂性状潜在的遗传标记。

【Objective】 Expressions of lipoprotein lipase(LPL)gene in different tissues and gene mutations were detected in yaks and the associations between mutations and milk quality traits were investigated to enrich the molecular genetic data for yak.【Method】 The expressions of LPL gene in tissues of Gannan yak were detected using Real-time quantitative PCR(RT-qPCR).Variations of LPL gene were identified by single strand conformation polymorphism(SSCP)in five yak populations including Gannan yak,Tianzhu white yak,Qinghai yak,Tibetan yak and wild-blood yak,and the associations between variations and milk quality traits of Gannan yak were analyzed by general linear model(GLM).【Result】 The relative expressions of LPL were higher in subcutaneous fat and heart,and lower in longissimus dorsi,breast,liver,spleen,kidney,large intestine,small intestine,abdomen and rumen,while the lowest expression was in lung.No polymorphism was identified in the exon 3,exon 6 and exon 7 regions of LPL gene in five yark populations.The two variations were identified in intron 2 region of LPL gene in five yak populations and allele M was the dominant allele with frequency of 67.11%-83.21%.The two variations were found in exon 4-intron 4 region and allele A was the dominant allele in Tibet yak(frequency 63.95%),while allele B was the dominant in other four yak populations(frequencies 59.75%-69.71%).Association analysis showed that Gannan yaks with genotype MM in intron 2 and AB in exon 4-intron 4 region or the two-region haplotype combination H1 H2(M-A/M-B) of LPL gene had higher milk fat rate,milk protein rate and total solid rate than other individuals.Especially,the milk fat rate was significantly higher than other individuals(P<0.05).【Conclusion】 A total of four variations were identified in intron 2 and intron 4 region of yak LPL gene.Mutations of LPL gene significantly affected milk fat rate of Gannan yak,and can be used as potential genetic marker for yak milk fascia.