Whole blood RNA extraction efficiency contributes to variability in RNA sequencing data sets

Abstract

Numerous methodologies are used for blood RNA extraction, and large quantitative differences in recovered RNA content are reported. We evaluated three archived data sets to determine how extraction methodologies might influence mRNA and lncRNA sequencing results. The total quantity of RNA recovered /ml of blood affects RNA sequencing by impacting the recovery of weakly expressed mRNA, and lncRNA transcripts. Transcript expression (TPM counts) plotted in relation to transcript size (base pairs, bp) revealed a 30% loss of short to midsized transcripts in some data sets. Quantitative recovery of RNA is of considerable importance, and it should be viewed more judiciously. Transcripts common to the three data sets were subsequently normalized and transcript mean TPM counts and TPM count coefficient of variation (CV) were plotted in relation to increasing transcript size. Regression analysis of mean TPM counts versus transcript size revealed negative slopes in two of the three data sets suggesting a reduction of TPM transcript counts with increasing transcript size. In the third data set, the regression slope line of mRNA transcript TPM counts approximates zero and TPM counts increased in proportion to transcript size over a range of 200 to 30,000 bp. Similarly, transcript TPM count CV values also were uniformly distributed over the range of transcript sizes. In the other data sets, the regression CV slopes increased in relation to transcript size. The recovery of weakly expressed and /or short to midsized mRNA and lncRNA transcripts varies with different RNA extraction methodologies thereby altering the fundamental sequencing relationship between transcript size and TPM counts. Our analysis identifies differences in RNA sequencing results that are dependent upon the quantity of total RNA recovery from whole blood. We propose that incomplete RNA extraction directly impacts the recovery of mRNA and lncRNA transcripts from human blood and speculate these differences contribute to the “batch” effects commonly identified between sequencing results from different archived data sets.

Characteristics of RNA Stabilizer RNApro for Peripheral Blood Collection

“…Human blood has been recognized as an important diagnostic resource for centuries. Blood is a complex fluid that is in constant contact with all body tissues, thereby providing information from a variety of unique compartments that include nucleated white blood cells (WBCs), nucleated red blood cells (RBCs), and cell-free RNA: ribonucleoprotein complexes and additional vesicular debris from various tissues in the body [13]. As blood sampling is considered a non-invasive procedure, it is often used for the assessment of a range of diseaserelated biomarkers.…”

SA-ODG platform: a semi-automated and PCR-free method to analyse microRNAs in solid tissues

“…These steps introduce undesired variability and complexity, impeding their practical use in clinical settings. 10–14 Moreover, many current alternative techniques to RT-qPCR, such as branched DNA, 15 Fireplex, 16 and nCounter, 17 still require RNA extraction and/or PCR amplification. 8…”

“…These steps introduce undesired variability and complexity, impeding their practical use in clinical settings. [10][11][12][13][14] Moreover, many current alternative techniques to RT-qPCR, such as branched DNA, 15 Fireplex, 16 and nCounter, 17 still require RNA extraction and/or PCR amplification. 8 In response to these challenges, in 2019 our group developed the OPTOI-DESTINA Genomica (ODG) platform, a novel analytical biosensor designed for the direct testing of circulating miRNAs.…”