Genome size and organization in the ixodid tick Amblyomma americanum (L.)

We used DNA reassociation kinetics to determine genome size and organization in the ixodid tick Amblyomma americanum. We calculated the genome size of A. americanum to be approximately 1.08 pg or 1.04 × 10⁹ base pairs and to consist of 35.8% unique DNA, 4.2% foldback sequences, 17.9% highly repetitive sequences, and 42.1% moderately repetitive sequences. Comparison of the reassociation kinetics of long and short fragments revealed repetitive sequences to be distributed in a pattern of long period interspersion, a feature that, to date, has been associated with arthropod genomes that lack a high percentage of repetitive DNA.     

Amblyomma americanum tick saliva insulin‐like growth factor binding protein‐related protein 1 binds insulin but not insulin‐like growth factors

Silencing Amblyomma americanum insulin‐like growth factor binding protein‐related protein 1 (AamIGFBP‐rP1) mRNA prevented ticks from feeding to repletion. In this study, we used recombinant (r)AamIGFBP‐rP1 in a series of assays to obtain further insight into the role(s) of this protein in tick feeding regulation. Our results suggest that AamIGFBP‐1 is an antigenic protein that is apparently exclusively expressed in salivary glands. We found that both males and females secrete AamIGFBP‐rP1 into the host during feeding and confirmed that female ticks secrete this protein from within 24–48 h after attachment. Our data suggest that native AamIGFBP‐rP1 is a functional insulin binding protein in that both yeast‐ and insect cell‐expressed rAamIGFBP‐rP1 bound insulin, but not insulin‐like growth factors. When subjected to anti‐blood clotting and platelet aggregation assays, rAamIGFBP‐rP1 did not have any effect. Unlike human IGFBP‐rP1, which is controlled by trypsinization, rAamIGFBP‐rP1 is resistant to digestion, suggesting that the tick protein may not be under mammalian host control at the tick feeding site. The majority of tick‐borne pathogens are transmitted 48 h after the tick has attached. Thus, the demonstrated antigenicity and secretion into the host within 24–48 h of the tick starting to feed makes AamIGFBP‐rP1 an attractive target for antitick vaccine development.     

Identification and characterization of a homologue of the pro-inflammatory cytokine Macrophage Migration Inhibitory Factor in the tick, Amblyomma americanum

Studying tick feeding and digestion, we discovered in a cDNA library from partially fed Amblyomma americanum ticks the first known arthropod homologue of a human cytokine, the pro-inflammatory Macrophage Migration Inhibitory Factor (MIF). The tick origin of the MIF cDNA clone was confirmed by sequencing a genomic fragment that contained the full-length tick MIF gene with two introns. Antiserum to a tick MIF-specific peptide as well as antiserum to complete tick MIF revealed the expression of tick MIF in the salivary gland and midgut tissues of A. americanum ticks. In an in vitro functional assay, recombinant tick MIF inhibited the migration of human macrophages to the same extent that recombinant human MIF did.     

RNA结合蛋白QKI在心肌肥大中的作用

目的探讨RNA结合蛋白QKI在血管紧张素Ⅱ诱导的心肌细胞肥大中的作用。方法将H9C2细胞分为对照组与心肌肥大组(AngⅡ组),AngⅡ组采用血管紧张素Ⅱ(10-7 mol/L)刺激H9C2细胞建立肥大模型;2组均采用转染小干扰RNA抑制QKI的表达,腺病毒感染H9C2细胞过表达QKI5和QKI6,应用Western blot检测H9C2细胞中QKI水平,应用实时定量RCR检测对照组及AngⅡ组作用6,12,18,24,36h时心房利钠多肽表达水平。结果与对照组比较,AngⅡ组作用12h总QKI增加,其中QKI6升高明显(P<0.05);AngⅡ+siQKI组心房利钠多肽水平较AngⅡ+NC组增加(P<0.05);AngⅡ+Ad-QKI5组心房利钠多肽水平与AngⅡ+Ad-Ctrl组比较差异无统计学意义(P>0.05),AngⅡ+Ad-QKI6组心房利钠多肽水平较AngⅡ+Ad-Ctrl组降低(P<0.05)。结论 QKI6可抑制心肌肥大。     

肺腺癌中关键RNA结合蛋白预后评估模型的构建

目的 基于生物信息学方法,评估肺腺癌中关键RNA结合蛋白的表达及预后作用.方法 从癌症基因组图谱(TCGA)数据库中下载526例肺腺癌组织、59例正常组织,以及从基因型-组织表达(GTEx)数据库中下载288例正常组织的RNA测序数据,筛选差异表达RNA结合蛋白;单因素和多因素Cox回归分析筛选关键RNA结合蛋白并构建...     

RNA interference in Pardosa pseudoannulata,an important predatory enemy against several insect pests,through ingestion of dsRNA-expressing Escherichia coli

RNA interference is an important technology for gene functional research in many organisms. The pond wolf spider (Pardosa pseudoannulata) is an important natural enemy of rice field pests. To facilitate large-scale gene functional research in this spider species and others, we developed an RNA interference (RNAi) method via ingestion of bacteria expressing dsRNA. The dsRNA targeting a cytochrome P450 monooxygenase (cyp41g2) was expressed in Escherichia coli HT115 (DE3). And then the bacterial suspension was fed to 14–20 days old spiderlings. The mRNA abundance of the target gene was significantly reduced after 3-day's ingestion of bacteria expressing dsRNA, and between day 5 and 7, RNAi efficiency remained stable. Thus, we selected 5 days as the optimum interference time. Furthermore, the bacteria resuspension containing 20 ng/μl dsRNA was selected as the optimum concentration. To evaluate the applicability of this method, three other genes with different tissue expression pattern were also selected as targets. And the mRNA abundance of all the four target genes was significantly reduced with RNAi efficiency between 66.0% and up to 86.9%. The results demonstrated that the oral delivery of bacteria expressing dsRNA would be an effective RNAi method for the gene functional study in P. pseudoannulata.     

Improved transient silencing of gene expression in the mosquito female Aedes aegypti

Gene silencing using RNA interference (RNAi) has become a widely used genetic technique to study gene function in many organisms. In insects, this technique is often applied through the delivery of dsRNA. In the adult female Aedes aegypti, a main vector of human-infecting arboviruses, efficiency of gene silencing following dsRNA injection varies greatly according to targeted genes. Difficult knockdowns using dsRNA can thus hamper gene function analysis. Here, by analysing silencing of three different genes in female Ae. aegypti (p400, ago2 and E75), we show that gene silencing can indeed be dsRNA sequence dependent but different efficiencies do not correlate with dsRNA length. Our findings suggest that silencing is likely also gene dependent, probably due to gene-specific tissue expression and/or feedback mechanisms. We demonstrate that use of high doses of dsRNA can improve knockdown efficiency, and injection of a transfection reagent along with dsRNA reduces the variability in efficiency between replicates. Finally, we show that gene silencing cannot be achieved using siRNA injection in Ae. aegypti adult females. Overall, this work should help future gene function analyses using RNAi in adult females Ae. aegypti, leading toward a better understanding of physiological and infectious processes.     

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.     

慢病毒载体及其在RNA干扰技术中的应用与发展

慢病毒载体是一类逆转录病毒载体,以其转染效率高,可感染分裂期和非分裂期细胞,可容纳较大的基因片段等优点,现已被作为转移目的基因的理想载体。而RNA干扰技术是近年来迅速发展起来可以特异性地剔除特定基因或者抑制特定基因表达的一种新技术,在病毒感染、心血管疾病、肿瘤等疾病的治疗中被广泛应用。通过慢病毒载体与RNA干扰技术的结合应用,有望为特定基因的功能以及相关疾病的治疗研究提供新的手段和方法。     

Functional validation of the carbon dioxide receptor genes in Aedes aegypti mosquitoes using RNA interference

Carbon dioxide (CO(2)) is an important long-range chemosensory cue used by blood-feeding female mosquitoes to find their hosts. The CO(2) receptor in Drosophila melanogaster was previously determined to be a heterodimer comprised of two gustatory receptor (Gr) proteins, DmGr21a and DmGr63a. In the mosquito Aedes aegypti, two putative orthologous genes, AaGr1 and AaGr3, were identified in the genome database, along with an apparent paralogue of AaGr1, AaGr2. In this study, RNA interference (RNAi)-mediated gene knockdown of either AaGr1 or AaGr3 resulted in a loss of CO(2) sensitivity in both male and female mosquitoes, suggesting that these two proteins, like the Drosophila orthologues, function as a heterodimer. RNAi-mediated knockdown of AaGr2 expression had no impact on CO(2) reception. All three Gr genes were expressed in the maxillary palps of both Ae. aegypti and the West Nile virus vector mosquito, Culex pipiens quinquefasciatus. Interestingly, expression of the two CO(2) receptor genes was not equivalent in the two sexes and the implications of differential sex expression of the CO(2) receptor in different species are discussed. The functional identification of the CO(2) receptor in a mosquito could prove invaluable in the strategic design of compounds that disrupt the mosquito's ability to find hosts.     

针对不同靶位点的siRNA对HepG2人肝肿瘤细胞株FOX03a表达的抑制作用

目的：探讨针对FOXO3a的小干扰RNA（siRNA）对HepG2 FOXO3a的表达、细胞增殖的抑制及细胞凋亡的作用。方法利用RNA干扰（RNAi）效应设计针对FOXO3a的不同siRNA,构建表达载体质粒并转染HepG2细胞系。RT-PCR和Western Blot分别检测FOXO3a mRNA及蛋白的表达,细胞生长实验和流式细胞观察转染前后细胞增殖及细胞凋亡的变化。另设一无意义RNA载体质粒为阴性对照。结果 P2、P3实验组,细胞核绿色荧光明显减淡,有细胞核的排出。特异性siRNA对FOXO3a mRNA及蛋白的表达具有抑制作用（P〈0.05）,细胞凋亡减少,增殖明显增加（P〈0.05）。结论抑制 FOXO3a 基因的表达能够减少HepG2细胞的凋亡,并增加细胞的增殖。FOXO3a有望成为治疗肝癌的有效的靶基因。     

siRNA前体慢病毒干扰A549细胞株蛋白激酶2a表达的载体构建及鉴定

目的构建针对蛋白激酶2a（caseinkinase2a,CK2a）基因的siRNA前体（shortharpinRNA,shRNA）表达载体,鉴定CK2a基因干扰效率。方法体外设计并合成针对CK2a基因的慢病毒shRNA干扰载体,通过PCR及测序证实载体构建成功。将人肺腺癌细胞株A549分为3组,病毒干扰组（CK组）将慢病毒颗粒以最适滴度感染细胞株A549,病毒空载组（NC组）将慢病毒颗粒空载体感染细胞株A549,阴性对照组（CON组）为未经任何处理的细胞株A549;检测各组CK2a的干扰效率。结果构建的慢病毒载体序列通过PCR、测序等鉴定证实与设计序列相同;实时定量PCR检测显示CK组A549细胞CK2amRNA表达率较NC组及CON组下降约80％;Westernblotting显示CK组A549细胞表达CK2a蛋白量较NC组及CON组明显减少。结论构建的shRNA表达载体可在mRNA和蛋白水平上有效抑制A549细胞株CK2a基因的表达。     

Feeding‐based RNA interference of a trehalose phosphate synthase gene in the brown planthopper,Nilaparvata lugens

The brown planthopper, Nilaparvata lugens, is the most devastating rice insect pest to have given rise to an outbreak in recent years. RNA interference (RNAi) is a technological breakthrough that has been developed as a powerful tool for studying gene function and for the highly targeted control of insect pests. Here, we examined the effects of using a feeding‐based RNAi technique to target the gene trehalose phosphate synthase (TPS) in N. lugens. The full‐length cDNA of N. lugens TPS (NlTPS) is 3235 bp and has an open reading frame of 2424 bp, encoding a protein of 807 amino acids. NlTPS was expressed in the fat body, midgut and ovary. Quantitative real‐time PCR (qRT‐PCR) analysis revealed that NlTPS mRNA is expressed continuously with little change during the life of the insect. Efficient silencing of the TPS gene through double‐stranded RNA (dsRNA) feeding led to rapid and significant reduction levels of TPS mRNA and enzymatic activity. Additionally, the development of N. lugens larvae that had been fed with the dsRNA was disturbed, resulting in lethality, and the cumulative survival rates dropped to 75.56, 64.44, 55.56 and 40.00% after continuous ingestion of 0.5 µg/µl dsRNA for 2, 4, 7 and 10 days, respectively. These values were significantly lower than those of the insects in the control group, suggesting that NlTPS dsRNA may be useful as a means of insect pest control.     

RNA interference‐mediated depletion of N‐ethylmaleimide Sensitive Fusion Protein and Synaptosomal Associated Protein of 25 kDa results in the inhibition of blood feeding of the Gulf Coast tick,Amblyomma maculatum

The signalling pathways in tick salivary glands that control ‘sialo‐secretome’ secretion at the tick?host interface remain elusive; however, this complex process is essential for successful feeding and manipulation of the host haemostatic response. Exocytosis of the sialo‐secretome in the salivary glands requires a core of soluble N‐ethylmaleimide‐sensitive fusion (NSF) attachment proteins (SNAPs) and receptor proteins (SNAREs). SNAREs have been identified as the key components in regulating the sialo‐secretome in the salivary gland cells. In this study, we utilized RNA interference to investigate the functional role of two Amblyomma maculatum SNARE complex proteins, AmNSF and AmSNAP‐25, in the tick salivary glands during extended blood feeding on the vertebrate host. Knock‐down of AmNSF and AmSNAP‐25 resulted in death, impaired feeding on the host, lack of engorgement and inhibited oviposition in ticks. Depletion also led to important morphological changes in the collapse of the Golgi apparatus in the salivary gland cells. Our results imply a functional significance of AmNSF and AMSNAP‐25 in prolonged tick feeding, and survival on the host. Further characterization of the factors that regulate exocytosis may lead to novel approaches to prevent tick‐borne diseases.