Small-sample total RNA purification: laser capture microdissection and cultured cell applications.

Gene expression studies require analysis of RNA, but isolation of total RNA from very small samples by traditional methods can be difficult and inefficient. The Absolutely RNA microprep kit provides a convenient method for isolating total RNA from small numbers of cells such as those harvested by laser capture microdissection (LCM). The protocol includes binding of RNA to a solid support, thus eliminating the need for organic extraction and alcohol precipitation. DNase digestion on the solid support reduces or eliminates DNA contamination and minimizes RNA handling. Efficient washing removes contaminants, and elution in a small volume of buffer results in high-purity RNA at a concentration appropriate for demanding applications such as RT-PCR. RNA isolated from as few as 200 laser capture microdissected brain tumor cells resulted in detection of low, medium, and highly expressed genes by conventional and real-time RT-PCR.     

High-quality RNA from cells isolated by laser capture microdissection

Laser capture microdissection (LCM) provides a rapid and simple method for procuring homogeneous populations of cells. However, reproducible isolation of intact RNAfrom these cells can be problematic; the sample may deteriorate before or during sectioning, RNA may degrade during slide staining and LCM, and inadequate extraction and isolation methods may lead to poor recovery. Our report describes an optimized protocol for preparation of frozen sections for LCM using the HistoGene Frozen Section Staining Kit. This slide preparation method is combined with the PicoPure RNA Isolation Kitfor extraction and isolation of RNA from low numbers of microdissected cells. The procedure is easy to perform, rapid, and reproducible. Our results show that the RNA isolated from the LCM samples prepared according to our protocol is of high quality. The RNA maintains its integrity as shown by RT-PCR detection of genes of different abundance levels and by electrophoretic analysis of ribosomal RNA. RNA obtained by this method has also been used to synthesize probes for interrogating cDNA microarray analyses to study expression levels of thousands of genes from LCM samples.     

激光显微切割分离细胞的微量RNA质量鉴定体系的 建立

摘要: 探索一套激光显微切割(Laser capture microdissection, LCM)分离细胞后获得的微量RNA质量鉴定标准操作流程。选取3个低温保存的胃癌旁组织样本, 冰冻切片进行甲酚紫染色和病理学检查, 利用激光显微切割技术分离非癌上皮细胞, 提取RNA并以Agilent 2100生物分析仪鉴定RNA的纯度和完整性。同时, 选择高、中、低3种不同表达丰度的6个基因(EF1A, ACTB, GAPHD, B2M, MED1, CK20), 在每个基因的5′和3′端设计引物, RT-PCR扩增。以3个培养细胞制备的高质量RNA和3个有降解的胃癌旁组织样本RNA作对照, RT-PCR扩增结果与Agilent 2100生物分析仪的结果高度一致。结果显示冻存组织进行冰冻切片结合病理学检查后, LCM获取细胞提取微量RNA采用RT-PCR进行质量鉴定是一种操作简单的稳定方法, 可以作为肿瘤基因组研究的有效和常规方法。     

Isolation of RNA from polysaccharide-rich seeds

Commonly, RNA isolation is the initial step in the study of gene expression analysis and also in the utilization of genes for genetic improvement. However, the recovery of large amounts of RNA with high quality is a difficult process, especially in tissues containing enhanced levels of polysaccharides and other secondary metabolites. Since several procedures for RNA isolation from polysaccharides rich plant tissues have been resulting in poor yields, an effective new protocol is essential for RNA isolation and further analysis. Here, we describe a novel modified technique for isolating total RNA from maturing grains. As a model, we utilized little finger millets, important food staples, which correspond to short duration crops cultivated in varied agro climatic conditions. After isolation, the total RNA was resolved on a denaturing agarose gel, showing more sharp bands of 28S, 18S, and 5S with no degradation. Therefore, the RNA concentration (higher than 1.80) was calculated by spectrophotometry, indicating that RNA is concentrated. Finally, RT-PCR and Northern hybridization confirmed high RNA quality.     

仿刺参体壁总RNA提取方法的建立

目的:通过对TRIzol一步法进行改进,建立一种从富含胶原蛋白、多糖及色素的仿刺参体壁提取总RNA的有效方法。方法:样品在液氮中研磨并用TRIzol匀浆后再进行抽提;对TRIzol一步法提取的总RNA进行DNaseⅠ消化和酚氯仿抽提,用2.5mol/L的醋酸钾沉淀,并加入适量糖原(10mg/mL)与RNA共沉淀。结果:琼脂糖凝胶电泳和紫外分光光度法以及RT-PCR检测结果表明,改进的方法能够有效去除基因组DNA、蛋白、多糖及色素的污染,RNA的产率提高。结论:制备的总RNA纯度高,完整性好,能够满足mRNA差异显示RT-PCR等分子生物学研究的要求,是一种提取仿刺参体壁及其他富含黏多糖、胶原蛋白和色素的动物组织总RNA的有效方法。     

Quantification of enterovirus RNA in sludge samples using single tube real-time RT-PCR

We have developed a quantitative RT-PCR method that can be used to determine the amount of enterovirus RNA in urban sludge samples. This method combines Taq-Man technology with the ABI Prism 7700 real-time sequence detection system. We optimized a one-step RT-PCR that uses a dual-labeled fluorogenic probe to quantify the 5' noncoding region of enteroviruses. For accurate quantification of the number of copies, a Mahoney type 1 poliovirus RNA standard was designed and produced using genetic engineering. This fragment, quantified using the Ribogreen method, was used in serial dilutions as an external standard. The method had a 7-log dynamic range (5 to 2 x 10(7)). PCR inhibitors were removed by extracting viral RNA (after virus concentration) using the RNeasy mini kit with added polyvinylpyrrolidone (PVP) and running the amplification reaction with a mixture containing PVP and T4 gene 32 protein. This real-time quantification of enterovirus RNA allows large numbers of samples to be screened. Its sensitivity, simplicity and reproducibility render it suitable as a screening method with which to characterize enteroviruses, the presence of infectious particles being subsequently confirmed by cell culture.     

Isolation of pure human mucosal epithelium for RNA analysis

Techniques for isolating the desired cell populations from complex tissues are essential for characterizing cells through mRNA analysis. We established a procedure for isolating pure mucosal epithelium from the human alimentary tract. To do this, we made rotating hooks that hold mucosal strips and detach the epithelial sheets from the irregular mucosae surface in medium containing EDTA. An additional step using a cell strainer was required to reduce contamination by lymphoid cells. Sheets of epithelial cells were detached successfully from mucosal samples derived from five different parts of the human alimentary tract. Contamination by lymphoid cells or fibroblasts was monitored by competitive RT-PCR and was no more than 0.5% of the total cells. Total RNA yields were 12.5-17 micrograms for each separation, and the integrity of the RNA was as good as that of RNAs extracted from mucosa immediately after resection. In conclusion, our method permits isolation of RNAs from a pure population of epithelial cells that can be used for mRNA-based gene expression analyses.     

RNA Isolation from Cell Specific Subpopulations Using Laser-capture Microdissection Combined with Rapid Immunolabeling

Laser capture microdissection (LCM) allows the isolation of specific cells from thin tissue sections with high spatial resolution. Effective LCM requires precise identification of cells subpopulations from a heterogeneous tissue. Identification of cells of interest for LCM is usually based on morphological criteria or on fluorescent protein reporters. The combination of LCM and rapid immunolabeling offers an alternative and efficient means to visualize specific cell types and to isolate them from surrounding tissue. High-quality RNA can then be extracted from a pure cell population and further processed for downstream applications, including RNA-sequencing, microarray or qRT-PCR. This approach has been previously performed and briefly described in few publications. The goal of this article is to illustrate how to perform rapid immunolabeling of a cell population while keeping RNA integrity, and how to isolate these specific cells using LCM. Herein, we illustrated this multi-step procedure by immunolabeling and capturing dopaminergic cells in brain tissue from one-day-old mice. We highlight key critical steps that deserve special consideration. This protocol can be adapted to a variety of tissues and cells of interest. Researchers from different fields will likely benefit from the demonstration of this approach.     

Preparative laser capture microdissection and single-pot cell wall material preparation: a novel method for tissue-specific analysis

In adaptation to their function the walls of plant cell display tissue-specific variations of composition according to their developmental stage, cell type and stress of various origin. It is therefore important to obtain a precise analytical data describing the cell wall composition with respect to these different factors. In the present work, laser capture microdissection (LCM) was used for isolating different tissues from the stem of Urtica dioica L. at a semi-preparative scale. The technique was associated for the first time to a one-pot sequential cell wall preparation and hydrolysis for the carbohydrate analysis of each cell type. The results demonstrate that the combination of LCM and micro-analytical methods can provide individual cell type composition and should improve our knowledge of the biochemical diversity of cell walls in plants. This approach will be of potential interest for the understanding of the effects of stress or genetic engineering on the composition of the cell walls.     

Evaluation of eight RNA isolation methods for transcriptional analysis in Campylobacter jejuni

DNA-free RNA samples are essential to investigate gene regulation using real-time RT-PCR. This study evaluated eight RNA isolation methods in combination with TURBO DNase treatment and acid phenol extractions for their ability to produce DNA-free RNA from Campylobacter jejuni strains.     

Isolation of High Quality RNA from Oilseeds of Jatropha curcas

High quality RNA with good yield is a prerequisite for carrying out several molecular biology studies. Recalcitrant tissues such as oilseeds pose several problems while isolating good quality RNA. We have standardized a fast and simple protocol for RNA isolation from the seeds of Jatropha curcas, which gives good quality RNA without compromising for the yield. By including pre wash of seed powder with acetone and removal of polysaccharides through selective precipitation, we have been regularly isolating good quality total RNA in the range of 300–450 μg g^?1 depending upon tissue type. The RNA isolated by this procedure is devoid of any contaminating DNA. The RNA preparations have been subjected to cDNA synthesis and PCR, and found suitable for these studies. This method also works satisfactorily with groundnut and mustard seeds.