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β2-微球蛋白(β2-microglobulin,β2m)是主要组织相容性复合体(major histocompatibility complex,MHC)Ⅰ分子的亚基之一,与MHC-Iα链非共价结合构成MHCⅠ分子。本实验通过反转录PCR(RT-PCR)和c DNA末端快速扩增技术(rapid-amplification of c DNA ends,RACE)克隆了尼罗罗非鱼(Oreochromis niloticus)β2m基因的全长c DNA序列及基因组序列,并对c DNA多态性、m RNA组织分布及感染链球菌后表达的变化进行了分析。结果共获得尼罗罗非鱼2条β2m基因c DNA,全长分别为900和906 bp。两c DNA均包括351 bp的ORF,共编码116个氨基酸残基,还包含68 bp的5’非编码区(5’-UTR)和486(492)bp的3’-UTR。两条c DNA对应各自不同的基因组序列。基因组序列分析发现,β2m基因含3个外显子和2个内含子。尼罗罗非鱼β2m基因推测氨基酸序列与其他物种的β2m基因相似性在39.20%~89.80%之间。β2m基因c DNA多态性分析表明,尼罗罗非鱼中共有2种不同类型的β2m c DNA,每种类型c DNA又有3种不同的亚型。定量PCR分析表明,β2m基因在尼罗罗非鱼脾脏、心脏和肾脏中表达量最高,鳃与肠中的表达量较高,在皮肤和肌肉中的表达量最低。腹腔注射无乳链球菌(Streptococcus agalactiae)后,尼罗罗非鱼β2m m RNA表达量在4个所检测组织(鳃,肾脏,心脏和脾脏)中均出现了先上升后下降的变化趋势。本实验结果表明,β2m基因可能参与尼罗罗非鱼的免疫应答,在免疫反应中发挥重要功能。本研究有助于进一步了解尼罗罗非鱼的免疫调节机制和更好地理解鱼类β2m的生理功能。
β2-microglobulin (β2-microglobulin, β2m) is one of the major subunits of the major histocompatibility complex (MHC) Ⅰ molecule, forming non-covalently MHC-Iα chain with MHC-Iα chain. In this study, the full-length c DNA sequence of β2m gene from Oreochromis niloticus was cloned by RT-PCR and rapid amplification of cDNA ends (RACE) And genomic sequences. The changes of c DNA polymorphism, tissue distribution of m RNA and expression after infection with streptococcus were analyzed. Results Two β2m gene cDNAs of Nile tilapia were obtained, with full length of 900 and 906 bp, respectively. Both c DNAs contain a 351 bp ORF encoding a total of 116 amino acid residues and also contain a 68 bp 5 ’UTR (5’-UTR) and a 486 (492) bp 3’-UTR. The two c DNAs correspond to different genomic sequences. Genomic sequence analysis found that β2m gene contains three exons and two introns. The similarity of the β2m gene between Nile tilapia and other species was estimated to be between 39.20% and 89.80%. β2m gene c DNA polymorphism analysis showed that Nile tilapia there are two different types of β2m c DNA, each type of c DNA and 3 different subtypes. Quantitative PCR analysis showed that β2m gene expressed highest in the spleen, heart and kidney of Nile tilapia, with higher expression in gill and intestine and lowest in skin and muscle. After intraperitoneal injection of Streptococcus agalactiae, the expression level ofβ2m m RNA in Nile tilapia (Tilapia niloticus) increased firstly and then decreased in four tissues (gill, kidney, heart and spleen). The experimental results show that β2m gene may be involved in the immune response of Nile tilapia, play an important role in the immune response. This study helps to further understand the immunomodulatory mechanisms of Nile tilapia and to better understand the physiological function of fish β2m.