转基因牧草研究进展

目前,国外在利用基因工程技术进行牧草育种方面已经取得重大进展。国内利用该技术进行相关领域的研究还相对滞后。本文在查阅国内外转基因牧草育种文献的基础上,介绍了转基因技术的要点、常用方法、存在的问题及应用前景。为今后牧草育种工作提供参考。     

Transgenic expression of a CD46 (membrane cofactor protein) minigene: Studies of xenotransplantation and measles virus infection

CD46 (membrane cofactor protein) is a human cell-surface regulator of activated complement and a receptor for the measles virus. A CD46 transgenic mouse line with an expression pattern similar to that of human tissues has been produced, to develop an animal model of (i) the control of complement activation by complement regulators in hyperacute rejection of xenografts, and (ii) measles virus infection. The mouse line was made using a CD46 minigene that includes promoter sequence and the first two introns of genomic CD46, which was coinjected into mouse ova with chicken lysozyme matrix attachment region DNA. A high level of CD46 expression in homozygotic transgenic mice was obtained with spleen cells having approximately 75% of the level found on human peripheral blood mononuclear cells. CD46 was detected in all tissues examined by immunohistochemistry, radioimmunoassay and Western blotting, showing that these mice were suitable for transplantation and measles virus infection studies. It also indicated that the transgene included the important regulatory elements of the CD46 promoter. Transgenic spleen cells were significantly protected in vitro from human complement activated by either the classical or alternative pathways and from alternative pathway rat complement. Furthermore, transgenic mouse hearts transplanted to rats regulated complement deposition in an in vivo model of antibody-dependent hyperacute xenograft rejection. Similar to human lymphocytes, transgenic lymphoblasts could be infected in vitro with measles virus; infected cells expressed viral proteins and produced infectious viral particles. The data demonstrate the suitability of this minigene for obtaining high-level CD46 expression sufficient for enhanced resistance of transgenic cells to complement attack and for obtaining wide tissue distribution of CD46, analogous to human tissues and, therefore, useful for comparative studies.     

Methylation status of immunoglobulin x e segments correlates with their recombination potential

We have previously shown that unlike endogenous ? genes, unrearranged ? transgenes undergo V?-J? recombination in T as well as B cells of transgenic mice. To determine whether the difference in recombination specificity of the transgenic and endogenous ? genes is associated with differences in DNA structure, the methylation status of the endogenous genes and three unrearranged ? transgenes was compared. The J?-C? locus of the transgenes was found to be hypomethylated in all tissues of the transgenic mice. In contrast, methylation of the endogenous ? genes was tissue and developmentally regulated. Hypomethylation of the endogenous J?-C? region occurs only in cells of the B lineage undergoing, or having completed ? gene recombination. Transfection of fibroblasts from transgenic and control mice with the recombination activating genes, Rag1 and Rag2, led to a high level of rearrangement of the hypomethylated transgenic, but not the endogenous ? genes. These results suggest that hypomethylation defines an accessible state of the ? locus and that methylation/demethylation could be involved in the control of ? gene rearrangement during lymphocyte differentiation.     

False-Positive β-Galactosidase Staining in Osteoclasts by Endogenous Enzyme: Studies in Neonatal and Month-Old Wild-Type Mice

Escherichia coli β-galactosidase (β-gal), encoded by the lacZ gene, has become an essential tool in studies of gene expression and function in higher eukaryotes. lac-Z is widely used as a marker gene to detect expression of transgenes or Cre recombinase driven by tissue-specific promoters. The timing and location of promoter activity is easily visualized in whole embryos or specific tissues using the cleavable, chromogenic substrate, 5-bromo-4-chloro-3-indolyl-D-galactopyranoside (X-gal). The tissue specificity of promoters in transgenic constructs is routinely tested by using a promoter of choice to drive lacZ. Alternatively, the targeted expression of Cre recombinase to perform in vivo recombination of loxP sites can be visualized by β-gal staining in mice carrying a Cre-activated lacZ transgene, such as the ROSA26 strain. In the course of our investigations, we examined β-gal activity in bone tissue from genetically normal mice using standard detection methodology and found very high endogenous activity in bone-resorbing osteoclasts. This was true in frozen, paraffin, and glycol methacrylate sections. X-gal staining colocalized with the osteoclast marker, tartrate-resistant acid phosphatase (TRAP). β-gal activity was present in osteoclasts in long bones, in the mandible, and in both neonatal and more mature animals. We present this brief article as a caution to those testing genetic models of skeletal gene expression using β-gal as a marker gene.     

降钙素基因相关肽转基因小鼠的建立及血压动态分析

目的 建立降钙素基因相关肽α(calcitonin gene-related peptide, CGRPα)和β(CGRPβ)转基因小鼠,并对其血压进行动态对比分析,建立可用于高血压研究的动物模型。方法 把人CGRPα和CGRPβ基因分别插入鸡β-肌动蛋白启动子下游,构建转基因表达载体,显微注射法建立C57BL/6J CGRPα和CGRPβ转基因小鼠,PCR鉴定转基因小鼠基因型。采用Western Blot鉴定CGRPα和CGRPβ在心脏、肺、肾脏和肝脏组织中的表达,筛选高表达转基因品系。用无创血压测量仪分析转基因小鼠动态血压变化。结果 建立了在心脏、肺、肾脏和肝脏组织中均高表达CGRPα基因的CGRPα转基因小鼠;在肺和肝脏组织中高表达CGRPβ基因的CGRPβ转基因小鼠。CGRPα转基因小鼠血压正常,CGRPβ转基因小鼠在12月龄时表现出显著的血压降低。结论 CGRPα和CGRPβ转基因小鼠可作为用于CGRP对外周血管阻力和高血压抵抗机制研究的动物模型。     

Enzyme therapy for Pompe disease: from science to industrial enterprise

Pompe disease or glycogen storage disease type II (OMIM 232300) is a metabolic myopathy with a broad clinical spectrum. Generalised muscle weakness combined with cardiomegaly presents within the first 3 months after birth, if the lysosomal α-glucosidase (AGLU) deficiency is complete. Residual enzyme activity prevents cardiac involvement and delays onset of muscle weakness. Enzyme therapy, by intravenous administration of acid AGLU, aims to supplement the missing enzyme activity. At the SHS symposium on Glycogen Storage Diseases Type I and II, in Fulda, two interim accounts were given of studies on the efficacy of enzyme therapy for Pompe disease; one with recombinant human acid AGLU produced in Chinese hamster ovary cells and the other with the same enzyme produced in the milk of transgenic rabbits.Conclusion: this review focuses on the latter study, discusses the scientific, technological and commercial aspects of the enterprise, and addresses the prospects and challenges of enzyme therapy for Pompe disease. Published online: 13 August 2002     

脑组织特异表达胆囊收缩素转基因小鼠的建立

目的建立在脑内特异表达胆囊收缩素(CCK)转基因小鼠,研究CCK表达在中枢对饮食行为和代谢的影响。方法构建PDGF-CCK表达载体,利用显微注射法将目的片断注射到受精卵的雄原核中,建立CCK转基因小鼠。通过PCR的方法鉴定转基因鼠的基因型。采用Western Blotting方法鉴定CCK在脑内的表达。用试剂盒测定小鼠血脂并进行统计学分析。结果得到了3个CCK转基因品系,其中2个转基因品系脑内CCK表达量比野生鼠明显增加。高表达CCK的转基因小鼠在正常饲养的情况下体重低于阴性鼠,但血脂未发现显著差异。结论脑内高表达CCK可在一定程度上导致小鼠体重减轻。     

B细胞淋巴瘤/白血病-2过表达对大鼠全脑缺血/再灌注后海马回磷酸化细胞外信号调节激酶的影响

目的 观察B细胞淋巴瘤/白血病-2(B-cell lymphoma/leukemia-2,Bcl-2)过表达对大鼠全脑缺血/再灌注(ischemia/reperfusion,I/R)后磷酸化细胞外信号调节激酶(phosphor-extracellular signal-regulated kinase,p-ERK)蛋白在海马回表达的影响.方法 90只健康雄性SD大鼠采用随机数字表法分为:假手术(SO)组,I/R组,Bcl-2过表达(Bcl-2)组.采用改良四血管法(four vessels occlusion method,4-VO)建立全脑I/R模型.应用HE染色,免疫组化染色及原位末端标记(terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling,TUNEL)方法观察海马回神经元形态改变,凋亡细胞及p-ERK在CA1区和CA3区的不同表达.结果 HE染色显示I/R组再灌注后48 h CA1区神经元数目减少,排列紊乱,核膜界限不清,结构模糊,CA3区较CA1区变化轻微 ;Bcl-2组变化不明显.TUNEL染色显示,SO组可见到少量凋亡细胞 ;I/R组再灌注后48 h凋亡细胞数达高峰,CA1区(110±13)明显多于CA3区(145±18)(P＜0.05);Bcl-2组较I/R组凋亡细胞数量明显减少(CA1区:143±15,CA3区:165±10)(P＜0.05).免疫组化染色显示:p-ERK在SO组CA1区、CA3区的表达基本呈阴性 ;I/R组再灌注后2h于CA3区开始弱表达,24 h达高峰,然后逐渐下降,CA1区(150±14)表达弱于CA3区(125±9) (P＜0.05) ;Bcl-2组表达明显强于I/R组(CA1区:123±13,CA3区:100± 10)(P＜0.05).结论 Bcl-2过表达可增加脑I/R后海马区p-ERK的表达,抑制细胞凋亡,其抗凋亡机制与ERK信号转导通路有关.     

设施设备心脏组织特异性表达Neuregulin-2转基因小鼠的建立及心脏功能分析

目的神经调节蛋白2(neuregulin-2,NRG2)可促进神经系统发育,基因缺失表现早期生长延迟,NRG2在心脏中也有表达,但其在心脏发育尤其是病理刺激时对心脏结构及功能的影响尚未见报道。本文目的是建立心脏组织特异性表达NRG2转基因小鼠,分析其在正常及压力负荷刺激时对心脏结构及功能的影响。方法将人NRG2基因插入到心脏特异性启动子α-MHC下游,构建转基因表达载体,显微注射法建立NRG2转基因小鼠,PCR鉴定转基因小鼠基因型,western blot鉴定NRG2蛋白在心脏中的表达并筛选高表达的转基因品系,主动脉缩窄术(transverse aortic constriction,TAC)制备压力负荷诱导的心肌肥厚小鼠模型。利用超声影像分析和病理学观察小鼠心脏结构和功能改变。结果建立了心脏组织特异性高表达NRG2转基因小鼠品系。与同窝阴性转基因小鼠相比,转基因小鼠左心室舒张末期后壁厚度(LVPWD)明显增加,3月龄时可达15.6%(P0.05),经压力负荷刺激后,NRG2转基因手术小鼠心室壁增厚程度显著下降,心室腔增大,同时心肌排列紊乱程度和纤维化程度明显比NTG手术小鼠严重。结论在压力负荷下,转基因表达NRG2缩短了肥厚过程,同时加速了心衰进程。     

转基因表达KLK1抵抗压力负荷引起的心室重构

目的 KLK1基因对高血压具有保护作用,KLK1在心脏中也有所表达,但目前对KLK1基因在心肌中的作用所知甚少。本研究通过建立KLK1基因转基因小鼠,在压力负荷的条件下,研究KLK1对心室重构的作用。方法把人KLK1基因插入鸡β-肌动蛋白启动子下游,构建转基因表达载体,显微注射法建立C57BL/6JKLK1转基因小鼠,PCR鉴定转基因小鼠基因型。采用Western Blot鉴定KLK1在心脏、大血管和肾脏中的表达筛选高表达转基因品系。用无创血压仪测量血压,利用超声影像分析技术和病理学观察转基因小鼠心脏结构与功能改变。结果建立了在心脏、肾脏和大血管壁高表达KLK1基因的转基因小鼠。在正常情况下,与同窝转基因阴性小鼠相比,转基因小鼠心脏结构和功能无显著变化。主动脉缩窄术后1个月,由于压力负荷的存在,同窝阴性小鼠左心室壁厚病理性肥厚,而转基因表达的KLK1可明显地抑制左心室壁肥厚的进程;主动脉缩窄术后2个月,同窝阴性小鼠心脏进入到病理性扩张阶段,KLK1也表现出对心肌病理性扩张的抑制,同时,组织学染色显示KLK1转基因小鼠心肌肥厚与纤维化程度减弱。结论转基因表达KLK1可抵抗压力负荷引起的心室重构。