小鼠Bpi条件基因打靶载体的构建和鉴定

目的构建小鼠Bpi条件基因打靶载体,为建立Bpi条件基因打靶小鼠模型和深入研究Bpi基因功能奠定基础。方法采用Cre/LoxP系统,选择小鼠Bpi基因第2、3外显子作为条件性敲除的目的片段,并在其两侧插入LoxP位点;运用LA-PCR技术,以129品系小鼠ES细胞基因组DNA为模板分步扩增包括Bpi第2、3外显子(中间同源臂)和上游同源臂在内的3.1 kb基因片段以及下游同源臂4.9 kb基因片段;构建pBSKⅡ-5SLoxP和ploxPFRTNeo-3L重组质粒,将前者酶切产物(3.1 kb)与酶切后的ploxPFRTNeo-3L质粒相连获得Bpi条件基因打靶载体。结果经多个限制性内切酶酶切鉴定和测序证实,构建的pBSKⅡ-5SLoxP、ploxPFRTNeo-3L重组质粒和Bpi条件基因打靶载体结构正确,与设计相符。结论成功构建了小鼠Bpi条件基因打靶载体。     

Co-transformation to tobacco of Cre/lox site-specific recombination system and its precise recombination

For the temporally and spatially regulated expression of the barnase gene in plant,two kinds of plasmids with cre gene and its directly repeat recognition sites lox from bacteriophage P1 were constructed and co-transformed into tobacco by agrobacterium mediated procedure.The transgenic plants were conformed by PCR analysis.The blocking fragment between the two lox directly repeat sites was excised by Cre protein in the transgenic plant genome.Cloning and sequencing the DNA fragment from the co-transformed plant DNA showed that the precise DNA excision occurred in transgenic tobacco genome directed by Cre/lox site-specific recombination.     

Co-transformation to tobacco of Cre/lox site-specific recombination system and its precise recombination

For the temporally and spatially regulated expression of the barnase gene in plant, two kinds of plasmids with cre gene and its directly repeat recognition sitesiox from bacteriophage P1 were constructed and co-transformed into tobacco by agrobacterium mediated procedure. The transgenic plants were conformed by PCR analysis. The blocking fragment between the twolox directly repeat sites was excised by Cre protein in the transgenic plant genome. Cloning and sequencing the DNA fragment from the co-transformed plant DNA showed that the precise DNA excision occurred in transgenic tobacco genome directed by Cre/lox site-specific recombination.     

Development of thymic lymphomas in mice disrupted of Brca2 allele in the thymus

Germ-line mutations in BRCA2 predispose to early-onset cancer. Homozygous mutant mouse, which has Brca2 truncated in exon 11 exhibit paradoxic occurrence of growth retardation and development of thymic lymphomas. However, due to its large embryonic lethality, cohort studies on the thymic lymphomas were not feasible. With the aid of Cre-loxP system, we demonstrate here that thymus-specific disruption of Brca2 allele without crossing it to p53-mutant background leads to the development of thymic lymphomas. Varying from 16 weeks to 66 weeks after birth, 25% of mice disrupted of Brca2 in the thymus died of thymic lymphomas, whereas previous report did not observe lymphomagenesis using similar Cre-loxP system. Future analysis of thymic lymphomas from these mice presented here will provide information on the cooperative mutations that are required for the BRCA2-associated pathogenesis of cancer.     

基于Cre／Loxp系统Tyr03、Axl受体酪氨酸激酶转基因小鼠的建立

采用大肠杆菌β一半乳糖酶基因LacZ作为报告基因,建立Tyr03、Axl受体酪氨酸激酶含有loxp位点的转基因小鼠。与不同组织特异性Cre小鼠杂交,获得时空性表达Tyr03、Axl的转基因小鼠,为研究其在各个组织中的功能奠定基础。方法构建含有loxp位点的Tyr03、Axl受体酪氨酸激酶质粒,测序正确后,通过显微注射法将插入CAG启动子下游的Geo—STOP—msAxl及Geo—STOP—msTyr03基因的转基因载体注射入BDFI供体鼠受精卵,移植受精卵至ICR受体鼠,待产仔后,通过双引物PCR鉴定F。以及Fn代小鼠的基因型,RT—PCR,X—gal染色观察小鼠组织中LaeZ基因,运用WB（WesternBlot）检测转基因小鼠和野生型小鼠体内目的蛋白表达的差异。结果获得了含有目的基因的转基因阳性小鼠;通过RT—PCR对阳性小鼠证明LacZ基因的存在;对存在LacZ基因的小鼠进行X—gal染色,在Geo—STOP—msTyr03的脑、睾丸、胸腺中观察到蓝色沉淀,在Geo—STOP—msAxl的脑、心、肾中观察到蓝色沉淀,间接说明目的基因能表达的组织和器官;对双阳性的Geo．STOP．msTyr03、Geo．STOP—msAxl转基因小鼠和野生型小鼠,WB检验证实Tyr03、Axl基因的表达没有差异,说明在加入stop序列之后,Tyr03基因确实存在,而且表达受到抑制。结论成功建立Geo-STOP—msAxl及Geo—STOP—msTyr03酪氨酸受体转基因小鼠。     

Avp －iCre 转基因小鼠的鉴定

将Avp－iCre转基因首建小鼠传到C57BL／6背景。通过与纯合ROSA26 Cre报告小鼠交配来检测iCre（improved Cre,改进的Cre重组酶）的表达,在子代中研究β－gal（beta－galactosidase,β－半乳糖苷酶）与AVP（ arginine vasopressin,精氨酸血管加压素）的共定位关系。利用ClockLab软件记录分析Avp－iCre小鼠跑轮运行行为节律的完整性。实验结果显示β－gal和AVP在SCN（ suprachiasmatic nucleus,视交叉上核）的表达存在明显共定位;Avp－iCre小鼠具备正常行为节律,其周期为23．65±0．14 h（Mean ±SD）,表明该Avp－iCre转基因小鼠可用于近日节律研究。     

Simultaneous deletion of floxed genes mediated by CaMKIIα-Cre in the brain and in male germ cells: application to conditional and conventional disruption of Goα

The Cre/LoxP system is a well-established approach to spatially and temporally control genetic inactivation. The calcium/calmodulin-dependent protein kinase II alpha subunit (CaMKIIα) promoter limits expression to specific regions of the forebrain and thus has been utilized for the brain-specific inactivation of the genes. Here, we show that CaMKIIα-Cre can be utilized for simultaneous inactivation of genes in the adult brain and in male germ cells. Double transgenic Rosa26^+/stop-lacZ::CaMKIIα-Cre^+/Cre mice generated by crossing CaMKIIα-Cre^+/Cre mice with floxed ROSA26 lacZ reporter (Rosa26^+/stop-lacZ) mice exhibited lacZ expression in the brain and testis. When these mice were mated to wild-type females, about 27% of the offspring were whole body blue by X-gal staining without inheriting the Cre transgene. These results indicate that recombination can occur in the germ cells of male Rosa26^+/stop-lacZ::CaMKIIα-Cre^+/Cre mice. Similarly, when double transgenic Gnao^+/f::CaMKIIα-Cre^+/Cre mice carrying a floxed Go-alpha gene (Gnao^f/f) were backcrossed to wild-type females, approximately 22% of the offspring carried the disrupted allele (Gnao^Δ) without inheriting the Cre transgene. The Gnao^Δ/Δ mice closely resembled conventional Go-alpha knockout mice (Gnao^−/−) with respect to impairment of their behavior. Thus, we conclude that CaMKIIα-Cre mice afford recombination for both tissue- and time-controlled inactivation of floxed target genes in the brain and for their permanent disruption. This work also emphasizes that extra caution should be exercised in utilizing CaMKIIα-Cre mice as breeding pairs.     

Towards a Light-mediated Gene Therapy for the Eye using Caged Ethinylestradiol and the Inducible Cre/lox System

Increasingly, retinal pathologies are being treated with virus-mediated gene therapies. To be able to target viral transgene expression specifically to the pathological regions of the retina with light, we established an in vivo photoactivated gene expression paradigm for retinal tissue. Based on the inducible Cre/lox system, we discovered that ethinylestradiol is a suitable alternative to Tamoxifen as ethinylestradiol is more amenable to modification with photosensitive protecting compounds, i.e., “caging.” Identification of ethinylestradiol as a ligand for the mutated human estradiol receptor was supported by in silico binding studies showing the reduced binding of caged ethinylestradiol. Caged ethinylestradiol was injected into the eyes of double transgenic GFAP-CreERT2 mice with a Cre-dependent tdTomato reporter transgene followed by irradiation with light of 450 nm. Photoactivation significantly increased retinal tdTomato expression compared to controls. We thus demonstrated a first step towards the development of a targeted, light-mediated gene therapy for the eyes.     

Cre-lox重组系统介导转基因烟草中外源基因删除的研究

对Cre在转基因个体中介导的重组效率进行了研究。构建了含有Cre 基因(p35S-Cre)和 GUS 基因侧翼含同向loxP 位点的(loxP-p35S-GUS-loxP)两种植物表达载体。以共转化的技术将两种基因元件同时转化烟草得到转基因植株,根据对共转化植株GUS 基因的活性分析、分子检测、PCR检测及对重组后扩增DNA片段进行序列分析表明：Cre-loxP 重组系统在转基因烟草中能精确高效地介导转基因的删除,但也存在部分植株不能完全删除的现象。     

通用型奶牛多位点基因打靶载体系统的构建

以奶牛为研究对象,以其重复的rRNA基因间的间隔序列为靶位点,基于BAC重组酶系统构建多位点基因打靶载体,为建立体内多位点基因打靶技术获得关键材料.首先构建BAC-TDN筛选载体,然后构建pYLVS-GD表达载体.将BAC-TDN筛选载体和pYLVS-GD表达载体共转化至大肠杆菌NS3529中,通过Cre重组酶的作用形成BAC-TDN-VS-GD质粒,采用归位内切酶I-SceI切除pYLVS载体骨架,构建奶牛多位点基因打靶载体BAC-TDN-GD,利用接头LS使之环化.BAC-TDN-GD打靶载体与pYLSV质粒组成了通用型奶牛多位点打靶载体系统.以重复序列为靶位点的多位点基因打靶技术,将部分解决目前存在的打靶效率低、安全性差等问题.