人乳腺癌MDR1基因稳定沉默细胞的筛选及其生物学特性

目的筛选MDR1沉默的人乳腺癌细胞并比较其生物学特性。方法采用BLOCK-iT Lentiviral RNAi Expres-sion System生产表达MDR1基因shRNA的慢病毒载体,转导敏感人乳腺癌细胞MCF-7和耐阿霉素人乳腺癌细胞MCF-7/ADM,杀稻瘟菌素(blasticidin)筛选获得MDR1稳定沉默细胞MCF-7/RNAi和MCF-7/ADM/RNAi。定量RT-PCR检测MDR1mRNA表达,流式细胞术检测P-GP蛋白表达和功能,MTT法检测药物敏感性。结果经10 mg/L blasticidin筛选12 d获得MCF-7/RNAi和MCF-7/ADM/RNAi细胞。MCF-7、MCF-7/RNAi、MCF-7/ADM和MCF-7/ADM/RNAi细胞的MDR1mRNA相对表达水平分别为1、0.13、17.14和2.01;P-GP表达分别为(1.5±0.3)%、(1.2±0.2)%、(89.4±3.6)%和(16.3±1.9)%;细胞内Rh123的潴留分别为(92.4±3.1)%、(90.6±4.0)%、(13.6±1.6)%、(72.4±2.8)%;IC50值分别为0.90、0.92、19.61和4.04 mg/L。结论应用慢病毒载体稳定沉默MDR1基因可有效逆转人乳腺癌细胞耐药性。     

微小RNAmiR-26a的克隆及其慢病毒表达载体的构建

目的克隆微小RNAhsa-miR-26a并构建其慢病毒表达载体。方法将PCR扩增得到的miR-26。前体序列和pIVTHM载体经双酶切后连接产生pIVTHM-miR-26a慢病毒表达载体，双酶切后测序鉴定。筛选阳性克隆。用pIVTHM-miR-26a、psPAX2和pMD2-G3质粒共转染包装细胞293FT，包装产生慢病毒，以293FT细胞绿色荧光蛋白（green fluorescent protein，GFP）的表达水平测定病毒滴度。结果经双酶切鉴定和测序证实，成功构建了miR-26a的慢病毒表达载体pIVTHM—miR-26a。倒置荧光显微镜下观察可见包装细胞293FT呈绿色荧光．并测得病毒滴度为5×10^5TU／ml。成功构建hsa—miR-26a的慢病毒表达载体，为深入研究miR-26a的生物学功能奠定了基础．     

慢病毒介导的外源基因体外投递系统的建立

目的针对不同哺乳类细胞建立相应的慢病毒体外感染体系，以建立慢病毒介导的外源基因体外投递系统。方法按Invitrogen公司推荐的标准程序进行慢病毒（携带EGFP基因）包装（脂质体介导的瞬时转染）、超速离心浓缩和保存等，随后用病毒上清或浓缩后的病毒感染293FT细胞，24—48h后荧光显微镜下观察是否见绿色荧光以证实慢病毒是否成功生产；将携带EGFP基因的病毒上清或浓缩后的病毒分别加入内含293FF细胞、小鼠ES细胞、小鼠胚胎成纤维细胞（MEFs）或小鼠睾丸生殖细胞的培养板孔内，感染6—12h后，用相应培养基替换感染液，数天后荧光显微镜下观察是否见绿色荧光以证实慢病毒是否成功感染不同哺乳类细胞。结果按标准程序生产的携带EGFP基因慢病毒（病毒上清或浓缩后的病毒）成功高效率感染293FF细胞、MEFs或小鼠睾丸生殖细胞；用浓缩后的病毒（携带EGFP基因）感染小鼠ES细胞，亦可获得EGFP阳性的ES细胞克隆。结论熟练掌握了慢病毒包装、浓缩及鉴定等技术，同时针对不同哺乳类细胞建立了相应的慢病毒介导的外源基因体外传递系统，这些为相关后续研究打下了良好的基础。     

Hypothalamic Corticotropin-Releasing Factor is Centrally Involved in Learning Under Moderate Stress

The corticotropin-releasing factor (CRF) neuropeptide is found to have a pivotal role in the regulation of the behavioral and neuroendocrine responses to stressful challenges. Here, we studied the involvement of the hypothalamic CRF in learning under stressful conditions. We have used a site-specific viral approach to knockdown (KD) CRF expression in the paraventricular nucleus of the hypothalamus (PVN). The two-way shuttle avoidance (TWSA) task was chosen to assess learning and memory under stressful conditions. Control animals learned to shuttle from one side to the other to avoid electrical foot shock by responding to a tone. Novel object and social recognition tasks were used to assess memory under less stressful conditions. KD of PVN-CRF expression decreased the number of avoidance responses in a TWSA session under moderate (0.8 mA), but not strong (1.5 mA), stimulus intensity compared to control rats. On the other hand, KD of PVN-CRF had no effect on memory performance in the less stressful novel object or social recognition tasks. Interestingly, basal or stress-induced corticosterone levels in CRF KD rats were not significantly different from controls. Taken together, the data suggest that the observed impairment was not a result of alteration in HPA axis activity, but rather due to reduced PVN-CRF activity on other brain areas. We propose that hypothalamic CRF is centrally involved in learning under moderate stressful challenge. Under ‘basal'' (less stressful) conditions or when the intensity of the stress is more demanding, central CRF ceases to be the determinant factor, as was indicated by performances in the TWSA with higher stimulus intensity or in the less stressful tasks of object and social recognition.     

Novel lentiviral vectors for human gene therapy

This review summarises an emerging viral vector system for use in human gene therapy - lentiviral vectors. Lentiviral vectors have several advantages over existing viral vectors. They can stably express transgenes in non-dividing cells in vivo without provoking a significant immune response. They can be produced to a high titre and can be pseudotyped with heterologous envelope proteins to confer broad tropism. Although not without safety concerns, the properties of lentiviral vectors makes them an attractive choice for human gene therapy.     

Development of packaging cell lines for generation of adeno-associated virus vectors by lentiviral gene transfer of trans-complementary components

Adeno-associated virus (AAV) vector system has several useful advantages with regard to in vitro and in vivo gene transfer. However, their usages have been limited by cumbersome and labor-intensive vector production in the traditional method. To overcome limitations in AAV production, in this report, we explored the possibility of generating AAV packaging cell line, 293T R/C.VA.E2A.E4. cells, by using lentivirus-mediated transduction of Rep/Cap gene of AAV-2, VA RNA, E2A, and E4 genes of Ad5 into 293T cells. In packaging cell lines, it is important that supply of the AAV vector can be stably performed for long time. We showed that the 293T R/C.VA.E2A.E4. cells have stably maintained the transduced components after more than 10 passages and yielded high-titer AAV vectors, and the titer of AAV vectors did not decline even if culture of the packaging cells was continued for long time. The Rep/Cap and E4 gene products caused no remarkable cytotoxicity. The 293T R/C.VA.E2A.E4. cells might be able to tolerate the Rep/Cap and E4 gene products, or have less copy numbers of the Rep/Cap and E4 genes than the traditional method. Moreover, we showed that the AAV vectors derived from 293T R/C.VA.E2A.E4. cells infected the primary human CD34+ haematopoietic progenitor cells with high efficiency (50-70%). In the 293T R/C.VA.E2A.E4. cells, the AAV vectors can be generated by the transfection of one AAV vector plasmid, and large-scale AAV production can be easily achieved. It is important that cumbersome, variable, and costly transfection is avoided.     

Brief Report: Divergent low-density lipoprotein receptor (LDLR) linked to low VSV G-dependent viral infectivity and unique serum lipid profile in zebra finches

The low-density lipoprotein receptor (LDLR) is key to cellular cholesterol uptake and is also the main receptor for the vesicular stomatitis virus glycoprotein (VSV G). Here we show that in songbirds LDLR is highly divergent and lacks domains critical for ligand binding and cellular trafficking, inconsistent with universal structure conservation and function across vertebrates. Linked to the LDLR functional domain loss, zebra finches show inefficient infectivity by lentiviruses (LVs) pseudotyped with VSV G, which can be rescued by the expression of human LDLR. Finches also show an atypical plasma lipid distribution that relies largely on high-density lipoprotein (HDL). These findings provide insights into the genetics and evolution of viral infectivity and cholesterol transport mechanisms in vertebrates.     

Lentiviral vector delivery of parkin prevents dopaminergic degeneration in an alpha-synuclein rat model of Parkinson's disease

Parkinson's disease (PD) is characterized by a progressive loss of midbrain dopamine neurons and the presence of cytoplasmic inclusions called Lewy bodies. Mutations in several genes including alpha-synuclein and parkin have been linked to familial PD. The loss of parkin's E3-ligase activity leads to dopaminergic neuronal degeneration in early-onset autosomal recessive juvenile parkinsonism, suggesting a key role of parkin for dopamine neuron survival. To evaluate the potential neuroprotective role of parkin in the pathogenesis of PD, we tested whether overexpression of wild-type rat parkin could protect against the toxicity of mutated human A30P alpha-synuclein in a rat lentiviral model of PD. Animals overexpressing parkin showed significant reductions in alpha-synuclein-induced neuropathology, including preservation of tyrosine hydroxylase-positive cell bodies in the substantia nigra and sparing of tyrosine hydroxylase-positive nerve terminals in the striatum. The parkin-mediated neuroprotection was associated with an increase in hyperphosphorylated alpha-synuclein inclusions, suggesting a key role for parkin in the genesis of Lewy bodies. These results indicate that parkin gene therapy may represent a promising candidate treatment for PD.     

慢病毒介导新型Tet-On系统调控大鼠GDNF和TH双基因表达对帕金森病大鼠的实验研究

目的观察改良Tet-On系统修饰慢病毒(Lv-TH-GDNF)目的基因的表达调控及纹状体内直接转移对帕金森病(PD)大鼠的作用。方法 1用Lv-TH-GDNF与rt TA2s-M2病毒感染He La细胞,免疫印迹法检测强力霉素(Dox)对TH、GDNF基因表达的调控。2用Lv-TH-GDNF与rt TA2sM2病毒共同注射到PD大鼠患侧纹状体,Dox诱导目的基因表达。通过观察阿扑吗啡(APO)诱导旋转行为、黑质多巴胺能神经元数量、患侧纹状体DA、DOPAC含量评估Lv-THGDNF治疗效应;通过移植侧纹状体内TH与GDNF蛋白量评估外源基因在体内的表达。结果 1在体外He La细胞实验,仅Dox阳性组见TH、GDNF蛋白条带。2在动物体内实验,病毒移植4周后,与PBS对照组相比,仅病毒+Dox组大鼠旋转行为明显改善(P<0.01),损伤侧黑质致密部TH阳性细胞数、纹状体DA、DOPAC含量及TH和GDNF蛋白量明显增高(P<0.01)。结论新型Tet-On系统修饰的Lv-THGDNF目的基因表达受四环素类抗生素调控,在体外实验未见基础活动,且纹状体内直接转移对PD大鼠有一定治疗作用。     

生长因子受体结合蛋白-2抑制肠癌细胞HT29增殖

目的 研究Grb2 shRNA转染对肠癌细胞HT29增殖相关信号通路的影响,探讨以Grb2为肠癌治疗靶点的可行性.方法 应用shRNA慢病毒质粒系统,将Grb2 shRNA转染至293T细胞,获得5株不同序列Grb2 shRNA慢病毒颗粒,并感染肠癌HT29细胞,分别获得的5株感染Grb2 shRNA慢病毒颗粒的肠癌HT29细胞系为实验组(即感染Grb2 shRNA的细胞HT29/shGrb2-69、HT29/shGrb2-70、HT29/shGrb2-71、HT29/shGrb2-72、HT29/shGrb2-73),以eGFP shRNA慢病毒感染肠癌HT29细胞为阴性对照组.MTT法检测细胞增殖情况,RT-PCR检测Grb2 mRNA表达,Western blot检测Grb2、P42/44 ERK、磷酸化P42/44 ERK、Akt、磷酸化Akt(P-Akt)和STAT5等信号通路分子表达的改变.结果 感染shGrb2病毒72 h,HT29/shGrb2-69、HT29/shGrb2-73两株细胞在mRNA和蛋白水平均出现抑制现象.HT29/shGrb2-69、HT29/shGrb2-73细胞在感染后24h A值分别为0.176±0.045,0.186±0.013,感染48 h后为0.347±0.048、0.382±0.041均显著高于空白对照、阴性对照(P ＜0.001),72 h为0.934±0.038、0.983±0.205高于空白对照、阴性对照(P＜0.01);感染后72 h,phospho-P42/44 ERK、Akt、phospho-Akt明显下降,而ERK、STAT5表达不受影响.结论 在HT29细胞,Grb2 mRNA和蛋白水平上明显抑制,可诱导HT29细胞增殖和相关信号传导通路分子表达下调.