dsRNA uptake and persistence account for tissue‐dependent susceptibility to RNA interference in the migratory locust,Locusta migratoria

RNA interference (RNAi) by introducing double‐stranded RNA (dsRNA) is a powerful approach to the analysis of gene function in insects; however, RNAi responses vary dramatically in different insect species and tissues, and the underlying mechanisms remain poorly understood. The migratory locust, a destructive insect pest and a hemimetabolic insect with panoistic ovaries, is considered to be a highly susceptible species to RNAi via dsRNA injection, but its ovary appears to be completely insensitive. In the present study, we showed that dsRNA persisted only briefly in locust haemolymph. The ovariole sheath was permeable to dsRNA, but injected dsRNA was not present in the follicle cells and oocytes. The lack of dsRNA uptake into the follicle cells and oocytes is likely to be the primary factor that contributes to the ineffective RNAi response in locust ovaries. These observations provide insights into tissue‐dependent variability of RNAi and help in achieving successful gene silencing in insensitive tissues.     

Role of methionine adenosyltransferase 2A and S-adenosylmethionine in mitogen-induced growth of human colon cancer cells

BACKGROUND & AIMS: Two genes (MAT1A and MAT2A) encode for methionine adenosyltransferase, an essential enzyme responsible for S-adenosylmethionine (SAMe) biosynthesis. MAT1A is expressed in liver, whereas MAT2A is widely distributed. In liver, increased MAT2A expression is associated with growth, while SAMe inhibits MAT2A expression and growth. The role of MAT2A in colon cancer in unknown. The aims of this study were to examine whether MAT2A expression and SAMe and its metabolite methylthioadenosine (MTA) can modulate growth of colon cancer cells. METHODS: Studies were conducted using resected colon cancer specimens, polyps from Min mice, and human colon cancer cell lines RKO and HT-29. MAT2A expression was measured by real-time polymerase chain reaction and cell growth by the 3-(4,5-dimethylthiazolyl-2-yl)-2,5-diphenyltetrazolium bromide assay. RESULTS: In 12 of 13 patients and all 9 polyps from Min mice, the MAT2A messenger RNA levels were 200%-340% of levels in adjacent normal tissues, respectively. Epidermal growth factor, insulin-like growth factor 1, and leptin increased growth and up-regulated MAT2A expression and MAT2A promoter activity in RKO and HT-29 cells. SAMe and MTA lowered the baseline expression of MAT2A and blocked the growth factor-mediated increase in MAT2A expression and growth in colon cancer cell lines. Importantly, the mitogenic effect of these growth factors was inhibited if MAT2A induction was prevented by RNA interference. SAMe and MTA supplementation in drinking water increased intestinal SAMe levels and lowered MAT2A expression. CONCLUSIONS: Similar to the liver, up-regulation of MAT2A also provides a growth advantage and SAMe and MTA can block mitogenic signaling in colon cancer cells.     

Therapeutic silencing of mutant huntingtin with siRNA attenuates striatal and cortical neuropathology and behavioral deficits

Huntington's disease (HD) is a neurodegenerative disorder caused by expansion of a CAG repeat in the huntingtin (Htt) gene. HD is autosomal dominant and, in theory, amenable to therapeutic RNA silencing. We introduced cholesterol-conjugated small interfering RNA duplexes (cc-siRNA) targeting human Htt mRNA (siRNA-Htt) into mouse striata that also received adeno-associated virus containing either expanded (100 CAG) or wild-type (18 CAG) Htt cDNA encoding huntingtin (Htt) 1-400. Adeno-associated virus delivery to striatum and overlying cortex of the mutant Htt gene, but not the wild type, produced neuropathology and motor deficits. Treatment with cc-siRNA-Htt in mice with mutant Htt prolonged survival of striatal neurons, reduced neuropil aggregates, diminished inclusion size, and lowered the frequency of clasping and footslips on balance beam. cc-siRNA-Htt was designed to target human wild-type and mutant Htt and decreased levels of both in the striatum. Our findings indicate that a single administration into the adult striatum of an siRNA targeting Htt can silence mutant Htt, attenuate neuronal pathology, and delay the abnormal behavioral phenotype observed in a rapid-onset, viral transgenic mouse model of HD.     

siRNA介导人结肠癌细胞诱骗受体3基因表达抑制的研究

目的:研究siRNA对结肠癌细胞株SW480 DcR3基因表达的影响.方法:化学合成靶向DcR3基因的4组siRNA,用脂质体转染试剂转染结肠癌细胞株SW480,应用噻唑兰(MTT)法检测siRNA对细胞生长的作用,RT-PcR和Western blot方法检测DcR3基因mRNA水平和蛋白表达量的变化.结果:与对照组相比,MTT试验结果显示各组siRNA对细胞增殖均有明显的抑制效应,但此抑制效应随时间延长而减弱.Western blot结果显示DcR3蛋白表达量明显降低.RT-PCR显示,转染后细胞内DcR3 mRNA的表达量与空白对照组相比降低至24%.结论:DcR3 siRNA通过特异、高效地沉默结肠癌细胞DcR3 mRNA的表达,发挥抑制结肠癌细胞生长的作用.     

导入靶向survivin基因的shRNA质粒表达载体对大肠癌细胞生物学行为的影响

目的:合成靶向survivin基因的shRNA并构建pGenesil-1-shRNA质粒表达载体,研究其对大肠癌Lovo细胞生物学效应的影响。方法:设计2条特异性靶向survivin基因的shRNA,与pGenesil-1质粒载体连接,导入大肠癌Lovo细胞、筛选稳定细胞株,Western Blot检测蛋白表达,流式细胞技术检测细胞生长周期,MTT法描绘细胞生长曲线。结果:筛选的稳定表达细胞内survivin蛋白的表达水平降低,survivin基因低表达的Lovo细胞停滞于G2/M期从而导致细胞生长速度减慢。结论:靶向survivin基因的shRNA能有效降低survivin基因在体内的表达,抑制大肠癌细胞的生长,为大肠癌基因治疗的可行性提供了有力的证据。     

人GLIPR-2基因慢病毒RNAi载体的构建及鉴定

目的 构建人GLIPR-2基因慢病毒RNA干扰（RNAi）载体,并鉴定其感染人肝癌细胞系HepG2后缺氧条件下的GLIPR-2基因表达变化.方法 根据GLIPR-2基因序列合成siRNA片段,克隆至慢病毒载体pMAGic7.1上,转染293T细胞进行包装,收获并浓缩重组慢病毒颗粒.感染HepG2细胞,流式细胞术检测GFP的表达率,并用Western blot检测目的 蛋白在缺氧条件下的表达变化.结果 重组RNAi质粒pMAGic7.1-shRNA-GLIPR-2经菌落PCR鉴定及测序证实构建正确;稳定感染HepG2 细胞后,GFP的表达率为分别为84.48%、69.97% 和39.82%;Western blot结果显示慢病毒转染组GLIPR-2蛋白的表达水平较对照组明显降低.结论成功构建了GLIPR-2基因慢病毒RNAi载体,该载体在缺氧条件下可明显抑制目的 蛋白在HepG2细胞中表达,为进一步研究GLIPR-2的生物学功能奠定了基础.     

RNAi干扰对K562细胞表达谱的影响

目的 联合运用RNAi技术和cDNA表达谱芯片研究干扰c-mye对K562细胞表达谱的影响。方法 经过RT-PCR和流武细胞仪检测。筛选出干扰效果最好的siRNAs,经Lipofectamine^TM 2000脂质体法转染K562细胞,提取总RNA,逆转录为cDNA,荧光标记后与K562表达谱芯片杂交。结果 经扫描、分析杂交结果,有455个基因表达下调,有12个基因表达上调。结论 基因芯片和RNAi是分析基因功能的有力工具,也是发现新的肿瘤治疗靶标的有效方法。     

Targeting ie-1 gene by RNAi induces baculoviral resistance in lepidopteran cell lines and in transgenic silkworms

RNA interference (RNAi)-mediated viral inhibition has been used in a few organisms for eliciting viral resistance. In the present study, we report the use of RNAi in preventing baculovirus infection in a lepidopteran. We targeted the baculoviral immediate early-1 (ie-1) gene in both a transformed lepidopteran cell line and in the transgenic silkworm Bombyx mori L. Constitutive expression of double-stranded RNA was achieved by piggyBac-mediated transformation of Sf9 cell line with a transgene encoding double-stranded ie-1 RNA (dsie-1). Strong viral repression was seen at early stages of infection but subsequent recovery of viral proliferation was observed. In contrast, the same transgene inserted into the chromosomes of transgenic silkworms induced long-term inhibition of B. mori nucleopolyhedrovirus infection, with nearly 40% protection compared with nontransgenic animals. Protection was efficient at larval stages after oral infection with occlusion bodies or hemocoel injection of budded viruses. Virus injected pupae also displayed resistance. These results show that heritable RNAi can be used to protect silkworm strains from baculovirus infection.     

应用RNAi沉默STAT3基因促裸鼠移植瘤细胞凋亡及对Bax/Bcl 2基因表达的影响

目的应用RNAi技术沉默信号转导子与转录活化子3(STAT3)基因,探讨其对人乳腺癌裸鼠移植瘤的细胞凋亡及其对Bax/Bcl2基因表达的影响。方法于雌裸鼠皮下种植MCF7细胞,肿瘤长至一定大小时,随机分为盐水对照(A)组、空质粒对照(B)组及实验(C)组。于肿瘤局部分别注射盐水、psilencer1.0U6空质粒和psilencer1.0U6STAT3siRNA重组质粒。当A组肿瘤长至足够大时处死全部动物,取肿瘤,测其大小及重量,行HE及免疫组化染色,同时用Westernblot检测STAT3,Bax,Bcl2基因的表达水平。结果C组肿瘤瘤块的体积和重量明显小于A,B组(P<0.01)。免疫组化及HE显示C组肿瘤中心区出现大面积细胞坏死及细胞凋亡征象,STAT3免疫组化呈阴性,而A,B组无此现象。Westernblot显示C组STAT3的表达明显低于A,B组(P<0.01),而Bax的表达明显高于A,B组(P<0.05),各组Bcl2的表达水平差异无显著性(P<0.05)。结论应用RNAi技术沉默STAT3基因可以降低人乳腺癌裸鼠移植瘤中STAT3的表达,同时引起Bax基因的表达上调,导致细胞凋亡进而抑制肿瘤的生长。