Extraction Of High-quality RNA Research Articles

The challenge of getting a high quality of RNA from oocyte for gene expression study.

The extraction of intact RNA from oocyte is quite challenging and time-consuming. A standard protocol using commercial RNA extraction kit, yields a low quantity of RNA in oocytes. In the past, several attempts in getting RNA for gene expression study ended up with a few different modified methods. Extraction of high-quality RNA from oocyte is important before further downstream analyses such as reverse transcription-polymerase chain reaction, quantitative polymerase chain reaction, or northern blot analysis. In this review, the efficiency of RNA extraction methods from all species oocytes was compared between published articles and our research to gather all possible methods of RNA extraction. Two different methods of RNA extraction that were proposed from various experiments were reviewed to determine the best method of RNA extraction from the oocyte. Modified TRIzol method can be concluded as an efficient RNA extraction method especially for good RNA from oocytes. Meanwhile, comparing RNA extraction kits to extract the RNA from oocytes or pre-implantation embryos, the micro RNA extraction kit type is the best. Therefore, an appropriate RNA extraction method is important to obtain high quality of total RNA for gene expression profiling analysis.

High-Quality and High-Yield RNA Extraction Method From Whole Human Saliva.

Background:Human saliva has been identified as a novel, practical, and noninvasive source of biomarkers and genetic materials. However, it is equally challenging due to the availability of an abundance of impurities in the form of microbes and other proteinaceous compounds. The objective of this study was to develop a robust, reproducible, and economic method of extracting high-yield and high-quality RNA from whole human saliva.Methods:The modified TRIzol protocol was developed to extract RNA from saliva (n = 14), followed by complementary DNA synthesis and reverse transcription quantitative polymerase chain reaction analyses for the genes encoding IL1B, ALPL, RUNX2, and ACTB. To compare our protocol with the spin column–based method, we used Qiagen Salivary Protect Micro-RNA spin columns (n = 6). To evaluate and compare the yields and quality of extracted RNAs from both methods, we used (1) Experion Bioanalyzer, (2) QuantiFluor RNA dye, and (3) NanoDrop 2000 Spectrometer.Results:With the modified TRIzol lysis protocol, a high yield of total RNA, on average 12.34 μg, from saliva was extracted compared with on average 0.2 μg with a spin column–based method. The average RQI (RNA quality index) with the TRIzol method was 7.86, which is also comparable with that of the spin column–based method (RQI = 7.58). QuantiFluor dye used for RNA quantification showed a 16-fold higher yield of RNA concentration using our TRIzol protocol.Conclusions:Our modified TRIzol protocol is a reproducible method to extract RNA from whole human saliva which can be used for gene expression analysis. This method allows also ensures the quality of RNA required for specific applications such as RNA sequencing.

Understanding Heterogeneity of Fetal Hemoglobin Induction through Comparative Analysis of Stage-Matched F- and a-Cells

Reversing the developmental switch from fetal (HbF, α2γ2) to adult (HbA, α2β2) hemoglobin is an important therapeutic approach in sickle cell disease (SCD) and β-thalassemia. Elevated HbF levels due to genetic variation or through therapeutic induction by hydroxyurea (HU) attenuate the severity of both disorders. HbF in healthy individuals, SCD patients, and patients treated with HU is present in a heterocellular fashion in a subset of red blood cells known as F-cells. Despite over 50 years of observations of F-cells, it is not known why only some cells in a genetically identical population are able to express HbF or respond to pharmacological inducers. Adult F-cells can potentially represent a reversion to a fetal-like epigenetic and transcriptional program, or alternatively isolated transcriptional or posttranscriptional events at the γ-globin genes. Here we set out to understand the heterogeneity of HbF activation and gain insights into whether the mechanisms underlying the heterocellular response are similar or distinct in response to different HbF inducers. To this end we developed techniques to purify differentiation stage-matched late erythroblast F-cells and non-F cells (A-cells) from the human HUDEP2 erythroid cell line and primary CD34 cell erythroid cultures using a reversible fixation protocol enabling extraction of high-quality RNA and protein. Purified F-cells from both sources were enriched for γ-globin transcripts by 200-500 fold by RT-PCR, validating the purification scheme. We profiled these cells by RNA-seq using a modified method that depletes globin mRNAs and ribosomal RNAs and is capable of detecting low abundance transcripts, as well as by mass spectrometry using size fractionation to increase the number of detected proteins. In differentiated clonal HUDEP2 cells, differences between F-cells and A-cells were remarkably small, with only 62 differentially expressed transcripts and 20 differentially expressed proteins. Top differentially expressed transcripts were γ-globin and the non-coding β-globin locus transcripts BGLT3 and HBBP1. Interestingly, there were no significant changes in known HbF regulators BCL11A, LRF, and HRI at the RNA or protein level. Gene set enrichment analysis (GSEA) using a previously generated set of differentially expressed transcripts from adult and fetal-derived CD34 erythroid cultures showed enrichment of fetal transcripts in F-cells and adult transcripts in A-cells. We also carried out transcriptome analysis of sorted matched late erythroblast F-cells and A-cells from human CD34+ cell erythroid cultures at different time points. Similar to HUDEP2 cells, only small numbers of transcripts were differentially expressed (33 at 8 days, 17 at 11 days, and 261 at 14 days). BCL11A, LRF, and HRI were not differentially expressed at the earlier timepoints, and BCL11A and HRI were at most decreased by about 20% at the 14-day mark. GSEA analysis did not show fetal transcript enrichment in day 8. At days 11 and 14, there was some enrichment of fetal transcripts in F-cells but not to the degree of HUDEP2 cells. Finally, we analyzed sorted F- and A-cells from day 11 CD34+ erythroid cultures treated with hydroxyurea and pomalidomide. Again, differences between F- and A-cells were small with hydroxyurea treatment (53 transcripts) and more significant with pomalidomide treatment (400 transcripts). We have successfully established an approach to analyze stage-matched γ-globin containing cells from a genetically identical starting population, with high degree of enrichment. Our preliminary data indicate that these cells are overall highly similar to non-γ-containing cells, but do show some enrichment of fetal-specific transcripts, more so in HUDEP2 cells. The differences between F- and A- cells are overall smaller than those observed by us and others in profiling of fetal and adult-derived erythroblasts. This suggests that F-cells are not formed by reversion to a fetal-like state but rather through specific changes at the β-globin locus. Importantly, we do not find differential levels of any known γ-globin regulators, suggesting an alternative mechanism for the heterocellular expression pattern. Studies are currently ongoing to carry out epigenetic profiling of F-cells. Disclosures Blobel: Bioverativ: Research Funding; Pfizer: Research Funding.

English

High quality RNA extraction from field-grown jute plants can be difficult due to the presence of complex polyphenolic, polysaccharide and waxes. But isolation of RNA in high quality is a basic need in plant genetics, genomics, transcriptomics, molecular biology and related physiological investigations. Here, cetyl trimethyl ammonium bromide (CTAB) based modified RNA isolation protocol suitable for isolating high quality total RNA from different parts of field-grown jute plants was reported. Modifications come with two extra wash with extraction buffer, residual polysaccharides precipitation with absolute ethanol and potassium acetate during phenol:chloroform:isoamyl alcohol (PCI), intermediate pelleting with lithium chloride followed by dissolving the pellet in sodium dodecyl sulfate (SDS). The 28S/18S ratio and RIN of isolated RNA were greater than 2.0 and 7.3 to 8.8, respectively reveal RNA to be high purity. The isolated RNA can be used directly for subsequent downstream applications including cDNA library construction, reverse transcription polymerase chain reaction (RT-PCR) and RNA-Seq raw data generation without further purification. Moreover, this study showed that this method could also be successfully applied to other polyphenols and polysaccharides rich malvaceous plants. Key words: RNA isolation, Corchorus, Jute, quantitative polymerase chain reaction with reverse transcription (RT-qPCR), cDNA library construction, next-generation sequencing (NGS) data generation.

Abstract 2174: A solution for simultaneous DNA & RNA extraction from single tissue without lysate splitting

Abstract Extraction of intact and high quality gDNA or RNA is one of the most common procedures in molecular biology labs. With the advance of NGS, scientists can analyze both genomic and transcriptomic information from the same sample. Techniques that offer the ability to isolate both DNA and RNA from a single biological sample are crucial for this application. There is still great need for improved protocols in this area especially for precious and low-yield samples. Currently, most researchers use TRIzol® to isolate RNA and DNA from the same tube by extracting DNA from the organic phase and RNA from the aqueous phase. Although this method can extract high-quality RNA, the DNA yield is often low. With many biological samples in short supply, it is crucial to maximize yields. We report here using Beckman Coulter reagents, a protocol to isolate both DNA and RNA from the same fresh/frozen sample. The method utilizes size selection to separate DNA and RNA. We tested this method on 4 different frozen mouse tissues and report consistent extraction performance across all 4 tissue types. There are two advantages for this method: (1) There is no need to split a lysate for separate preparation of DNA/RNA; thus, researchers will not lose any portion of DNA or RNA. (2) Due to the different size distributions between DNA and RNA, this method offers quick and efficient extraction. Citation Format: Han Wei. A solution for simultaneous DNA & RNA extraction from single tissue without lysate splitting [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 2174.

An efficient method for extracting next-generation sequencing quality RNA from liver tissue of recalcitrant animal species.

The next-generation RNA sequencing technologies expedite the discovery of a large number of novel transcripts and genes associated with various pathophysiological conditions. These technologies involve poly(A) enrichment, which in turn requires micrograms of high-quality total RNA. Unfortunately, the available RNA isolation approaches produce poor quality total RNA from difficult-to-isolate animal tissues, such as the liver with high glycogen content. Moreover, the extraction efficiencies of these approaches vary significantly depending on the animal species. To address this challenge, we optimized a three-step protocol for the extraction of high-yield and high-quality total RNA from the liver tissue (LT). The procedure effectively resolved the problem of glycogen coprecipitation by its stepwise removal. No signs of RNA degradation on gel electrophoresis analysis and RNA integrity number values ≥8.5 indicated that the extracted RNA is suitable for downstream processing, such as poly(A) enrichment and transcriptome profiling. To demonstrate the robustness of the novel protocol, a comparison was made with other currently available RNA extraction approaches from diverse resources. Whereas other protocols yielded partially degraded bands with either decreased or reversed ribosomal RNA (rRNA) ratio, our protocol yielded intact rRNA with a ratio of 2.0 ± 0.1. This optimized protocol was also successfully followed for other animal tissues, such as the bone and muscles. In conclusion, the study has described a highly efficient method for the next-generation sequencing quality RNA isolation from LT across a broad range of animal species, with extended applicability to other difficult-to-isolate tissues.

Protocol adjustment improves the extraction of high-quality total RNA from common bean stems infected by Sclerotinia sclerotiorum

ABSTRACT The Straw Test is an assay developed to evaluate the resistance of common bean to white mold, in which the plant stems are inoculated and the symptoms of the disease are monitored. It is plausible to admit that investigating gene expression in pathogen-infected tissues may be strategically interesting. However, obtaining a quality RNA is a basic requirement for this purpose. Therefore, the objective of this study was to evaluate adjustments in protocols of commercial kits in the expectation of improving the quality of RNA obtained from bean stems. For this, plants of two lines were inoculated and the stems pathogen-infected were collected 72 hours after. For RNA extraction, two commercial reagents were used following the manufacturer’s recommendations and then following adaptations in these protocols. In particular, the proposed modifications relate to volumes of supernatant recovered in purification steps, additional step of chloroform purification and extended time for nucleic acids precipitation. The obtained RNA was analyzed by spectrophotometer, electrophoresis and bioanalyzer, then converted into cDNA and subsequently submitted to PCR. From the obtained data, it was observed that the adaptations made in the protocols contributed to better results and that, when the indicative values of RNA quality are guaranteed, the subsequent reactions are more pure, precise and representative.

Strategies for Global RNA Sequencing of the Human Pathogen Neisseria gonorrhoeae.

Over the last several years transcriptomic analysis of bacterial pathogens has become easier and less expensive. This technique is used to determine expression levels for all genes of a particular species or collection of species under a given condition, including genes that are not yet known to exist. While transcriptomics can be a powerful tool to better understand bacterial regulatory responses to specific host environments, the experimental approach and data analysis must be performed correctly to ensure robust, accurate, and translational results. Here, we describe experimental protocols related to transcriptomic analysis of the sexually transmitted disease pathogen Neisseria gonorrhoeae. Methods are described for the extraction of high-quality RNA, examination of RNA to ensure quality, the generation of cDNA libraries for sequencing and the downstream analysis of raw sequencing data to determine gene expression levels. Much of this work can be carried out with equipment and reagents that are readily available, and the methods can be performed by a majority of laboratory groups. RNA-seq and transcriptomic analyses are set to become even more common in the coming years. The protocols described here will provide a standardized set of methods for applying this powerful technique to the study of N. gonorrhoeae under a variety of conditions.

Fast and inexpensive protocols for consistent extraction of high quality DNA and RNA from challenging plant and fungal samples for high-throughput SNP genotyping and sequencing applications.

Modern genotyping techniques, such as SNP analysis and genotyping by sequencing (GBS), are hampered by poor DNA quality and purity, particularly in challenging plant species, rich in secondary metabolites. We therefore investigated the utility of a pre-wash step using a buffered sorbitol solution, prior to DNA extraction using a high salt CTAB extraction protocol, in a high throughput or miniprep setting. This pre-wash appears to remove interfering metabolites, such as polyphenols and polysaccharides, from tissue macerates. We also investigated the adaptability of the sorbitol pre-wash for RNA extraction using a lithium chloride-based protocol. The method was successfully applied to a variety of tissues, including leaf, cambium and fruit of diverse plant species including annual crops, forest and fruit trees, herbarium leaf material and lyophilized fungal mycelium. We consistently obtained good yields of high purity DNA or RNA in all species tested. The protocol has been validated for thousands of DNA samples by generating high data quality in dense SNP arrays. DNA extracted from Eucalyptus spp. leaf and cambium as well as mycelium from Trichoderma spp. was readily digested with restriction enzymes and performed consistently in AFLP assays. Scaled-up DNA extractions were also suitable for long read sequencing. Successful RNA quality control and good RNA-Seq data for Eucalyptus and cashew confirms the effectiveness of the sorbitol buffer pre-wash for high quality RNA extraction.

Neocortical Microdissection at Columnar and Laminar Resolution for Molecular Interrogation.

The heterogeneous organization of the mammalian neocortex poses a challenge for elucidating the molecular mechanisms underlying its physiological processes. Although high-throughput molecular methods are increasingly deployed in neuroscience, their anatomical specificity is often lacking. In this unit, we introduce a targeted microdissection technique that enables extraction of high-quality RNA and proteins at high anatomical resolution from acutely prepared brain slices. We exemplify its utility by isolating single cortical columns and laminae from the mouse primary somatosensory (barrel) cortex. Tissues can be isolated from living slices in minutes, and the extracted RNA and protein are of sufficient quantity and quality to be used for RNA sequencing and mass spectrometry. This technique will help to increase the anatomical specificity of molecular studies of the neocortex, and the brain in general, as it is applicable to any brain structure that can be identified using optical landmarks in living slices. © 2018 by John Wiley & Sons, Inc.

Comparison of various RNA extraction methods, cDNA preparation and isolation of calmodulin gene from a highly melanized isolate of apple leaf blotch fungus Marssonina coronaria

Marssonina coronaria causes apple blotch disease resulting in severe premature defoliation, and is distributed in many leading apple-growing areas in the world. Effective, reliable and high-quality RNA extraction is an indispensable procedure in any molecular biology study. No method currently exists for RNA extraction from M. coronaria that produces a high quantity of melanin-free RNA. Therefore, we evaluated eight RNA extraction methods including manual and commercial kits, to yield a sufficient quantity of high-quality and melanin-free RNA. Manual methods used here resulted in low quality and black colored RNA pellets showing the presence of melanin, despite all the modifications employed to original procedures. However, these methods when coupled with clean up resulted in melanin-free RNA. On the other hand, all commercial kits used were able to yield high-quality melanin-free RNA having variable yields. TRIzol™ Reagent + RNA Clean & Concentrator™-5 and Ambion-PureLink® RNA Mini Kit were found to be the best methods as the RNA extracted with these methods from 15 day old fungal culture grown on solid medium were free of melanin with good yield. RNA extracted by this improved methodology was applied for RT-PCR, subsequent PCR amplification, and isolation of calmodulin gene sequences from M. coronaria and infected apple leaf pieces. These methods are more time effective than traditional methods and take only an hour to complete. To our knowledge, this is the first report on the method of isolation of high-quality RNA for cDNA synthesis as well as isolation of the calmodulin gene sequence from this fungus.

A robust method for RNA extraction and purification from a single adult mouse tendon.

BackgroundMechanistic understanding of tendon molecular and cellular biology is crucial toward furthering our abilities to design new therapies for tendon and ligament injuries and disease. Recent transcriptomic and epigenomic studies in the field have harnessed the power of mouse genetics to reveal new insights into tendon biology. However, many mouse studies pool tendon tissues or use amplification methods to perform RNA analysis, which can significantly increase the experimental costs and limit the ability to detect changes in expression of low copy transcripts.MethodsSingle Achilles tendons were harvested from uninjured, contralateral injured, and wild type mice between three and five months of age, and RNA was extracted. RNA Integrity Number (RIN) and concentration were determined, and RT-qPCR gene expression analysis was performed.ResultsAfter testing several RNA extraction approaches on single adult mouse Achilles tendons, we developed a protocol that was successful at obtaining high RIN and sufficient concentrations suitable for RNA analysis. We found that the RNA quality was sensitive to the time between tendon harvest and homogenization, and the RNA quality and concentration was dependent on the duration of homogenization. Using this method, we demonstrate that analysis of Scx gene expression in single mouse tendons reduces the biological variation caused by pooling tendons from multiple mice. We also show successful use of this approach to analyze Sox9 and Col1a2 gene expression changes in injured compared with uninjured control tendons.DiscussionOur work presents a robust, cost-effective, and straightforward method to extract high quality RNA from a single adult mouse Achilles tendon at sufficient amounts for RT-qPCR as well as RNA-seq. We show this can reduce variation and decrease the overall costs associated with experiments. This approach can also be applied to other skeletal tissues, as well as precious human samples.

Transcriptomic profiling of human skin biopsies in the clinical trial setting: A protocol for high quality RNA extraction from skin tumours.

Transcriptomic profiling of skin disease using next generation sequencing allows for detailed information on aspects of RNA biology including gene expression, non-coding regulatory elements and gene splicing. The application of RNA sequencing to human skin disease and cancer is often hampered by degraded RNA. Here we describe a protocol that allows for consistently intact RNA to be extracted from snap frozen skin biopsy samples, which has been validated in a clinical trial setting. Human skin tumour punch biopsies (n=28) ranging from 4-6mm in diameter were obtained from 14 patients with an inherited skin tumour syndrome (CYLD cutaneous syndrome) and frozen in liquid nitrogen prior to being stored at -80°C. These samples were then subject to cyrostat sectioning, allowing for histological assessment, and were homogenised using a bead-based lysis platform. RNA extraction was performed using a silica column-based system. RNA concentration was measured using fluorescent quantitation and RNA integrity assessed using microfluidic gel electrophoresis. We also processed normal skin biopsies using the same protocol (n=10). The mean RNA integrity score of the tumour and normal samples was 9.5, and the quantity of RNA obtained from the small amounts of tissue used exceeded requirements for RNA-seq library generation. We propose that the method of RNA extraction suggested here allows for transcriptomic profiling from small pieces of human tissue without the need for PCR amplification during library preparation. This protocol could be utilised in healthy and diseased skin to improve mechanistic understanding in a range of human skin diseases.

Extraction of high-quality RNA from Bacillus subtilis with a lysozyme pre-treatment followed by the Trizol method

A suitable technique (lysozyme combined with Trizol reagent) was developed to improve the RNA yield, purity and integrity from Bacillus subtilis, under different bacterial growth stages. The obtained RNA was intact, having the required characteristics for downstream applications.

Rapid detection of potyviruses from crude plant extracts

Potyviruses (genus Potyvirus; family Potyviridae) are widely distributed and represent one of the most economically important genera of plant viruses. Therefore, their accurate detection is a key factor in developing efficient control strategies. However, this can sometimes be problematic particularly in plant species containing high amounts of polysaccharides and polyphenols such as yam (Dioscorea spp.). Here, we report the development of a reliable, rapid and cost-effective detection method for the two most important potyviruses infecting yam based on reverse transcription-recombinase polymerase amplification (RT-RPA).The developed method, named ‘Direct RT-RPA’, detects each target virus directly from plant leaf extracts prepared with a simple and inexpensive extraction method avoiding laborious extraction of high-quality RNA. Direct RT-RPA enables the detection of virus-positive samples in under 30 min at a single low operation temperature (37 °C) without the need for any expensive instrumentation.The Direct RT-RPA tests constitute robust, accurate, sensitive and quick methods for detection of potyviruses from recalcitrant plant species. The minimal sample preparation requirements and the possibility of storing RPA reagents without cold chain storage, allow Direct RT-RPA to be adopted in minimally equipped laboratories and with potential use in plant clinic laboratories and seed certification facilities worldwide.

RNA-Seq as an Emerging Tool for Marine Dinoflagellate Transcriptome Analysis: Process and Challenges

Dinoflagellates are the large group of marine phytoplankton with primary studies interest regarding their symbiosis with coral reef and the abilities to form harmful algae blooms (HABs). Toxin produced by dinoflagellates during events of HABs cause severe negative impact both in the economy and health sector. However, attempts to understand the dinoflagellates genomic features are hindered by their complex genome organization. Transcriptomics have been employed to understand dinoflagellates genome structure, profile genes and gene expression. RNA-seq is one of the latest methods for transcriptomics study. This method is capable of profiling the dinoflagellates transcriptomes and has several advantages, including highly sensitive, cost effective and deeper sequence coverage. Thus, in this review paper, the current workflow of dinoflagellates RNA-seq starts with the extraction of high quality RNA and is followed by cDNA sequencing using the next-generation sequencing platform, dinoflagellates transcriptome assembly and computational analysis will be discussed. Certain consideration needs will be highlighted such as difficulty in dinoflagellates sequence annotation, post-transcriptional activity and the effect of RNA pooling when using RNA-seq.

Comparative analysis and innovation of a simple and rapid method for high-quality RNA and DNA extraction of kiwifruit

RNA and DNA extraction is a requirement for the study of gene expression and has an increasingly important role in genetic studies of all fleshy fruits. RNA and DNA extraction is difficult in kiwifruit due to the significant amount of polysaccharides and polyphenols compounds. So far, no commercial kit has been developed specifically for high-quality RNA and DNA extraction in kiwifruit and the common protocols for RNA extraction have poor yields. This study developed a new protocol for high quality RNA extraction in Actinidia deliciosa. According to the results, the average yield of RNA extraction of fruit and leaf of A. deliciosa was ~2180.7?ng/µl (~545.175?µg/g?FW) and ~3424.9?ng/µl (~856.225?µg/g?FW), respectively with A260/A280 between 1.95 to 2.07 and A260/A230 higher than 2 indicating high RNA purity. While the averages yield of RNA extraction using previous methods from kiwifruit and leaf was 23?µg/g?FW and 527?µg/g?FW, respectively. Also, the average yields of genomic DNA from kiwifruit ranged from 52 to 98?ng/µl with A260/A230 between 0.60 to 1.64 and A260/A280 between 1.40 to 1.48. To our knowledge, this is the first report of a highly efficient and rapid method of RNA and DNA extraction in kiwifruit which can be used for a broad spectrum of the all fleshy fruits.

Cell Type-Specific Laser Capture Microdissection for Gene Expression Profiling in the Human Brain.

Cell type-specific laser microdissection technologies in combination with molecular techniques to determine gene expression profiles have become powerful tools to gain insight into the neurobiological basis of neural circuit disturbances in various neurologic or psychiatric diseases. To identify specific cell populations in human postmortem brain tissue, one can use the inherent properties of the cells, such as pigmentation and morphology or their structural composition through immunohistochemistry (IHC). Here, we describe the isolation of homogeneous neurons and oligodendrocytes and the extraction of high-quality RNA from these cells in human postmortem brain using a combination of rapid IHC, Nissl staining, or simple morphology with Laser Capture Microdissection (LCM), or Laser Microdissection (LMD).

Optimization of phenol-chloroform RNA extraction

Accurate and reliable analysis of gene expression depends on the extraction of pure and high-quality RNA. However, while the conventional phenol-chloroform RNA extraction is preferable over silica-based columns, particularly when cost is a concern or higher RNA yield is desired, it can result in significant RNA contamination. Contaminants including excess phenol, chloroform, or salts, can have significant impacts on downstream applications, including RNA quantification and reverse transcription, that can skew data collection and interpretation. To overcome the issue of RNA contamination in the conventional phenol-chloroform based RNA extraction method, we have optimized the protocol by adding one chloroform extraction step, and several RNA washing steps. Importantly, RNA quality and purity and accuracy in the quantification of RNA concentration were significantly improved with the modified protocol, resulting in reliable data collection and interpretation in downstream gene expression analysis.•Our protocol is customized by the addition of a second chloroform extraction step. Chloroform is carefully pipetted so as to not disturb the interphase layer. Any contaminants accidentally removed from interphase will be present in subsequent steps and can result in RNA contaminated with protein or phenol. The additional chloroform step increases RNA purity.•Additionally, the addition of 2 additional ethanol washes, initially intended to remove any residual salts from the isopropanol RNA precipitation step, also removed residual phenol contamination, enhancing RNA purity.•In summary, these modifications serve to enhance not only the purity of the RNA but, also increase the accuracy and reliability of RNA quantification.

MicroRNA Analysis Using Next-Generation Sequencing.

Next-generation sequencing (NGS) enables the analysis of both microRNA expression and sequence, allowing for elucidation of a comprehensive landscape of miRNAs in a given tissue and sample type. NGS analysis requires high-quality RNA extraction and preparation of microRNA libraries. In this chapter, we describe the methods used for RNA extraction from tissue specimens, serum, cytological slides, and formalin-fixed paraffin-embedded samples. Although the described library preparation and sequencing approaches are based on Illumina NextSeq 500 sequencing technology, the presented principles shall be compatible with other commercially available sequencing platforms.