Pre-amplification in the context of high-throughput qPCR gene expression experiment

High-Throughput Microfluidic Quantitative PCR Platform for the Simultaneous Quantification of Pathogens, Fecal Indicator Bacteria, and Microbial Source Tracking Markers

Contamination of water with bacterial, viral, and protozoan pathogens can cause human diseases. Both humans and nonhumans can release these pathogens through their feces. To identify the sources of fecal contamination in the water environment, microbial source tracking (MST) approaches have been developed; however, the relationship between MST markers and pathogens is still not well understood most likely due to the lack of comprehensive datasets of pathogens and MST marker concentrations. In this study, we developed a novel microfluidic quantitative PCR (MFQPCR) platform for the simultaneous quantification of 37 previously validated MST markers, two fecal indicator bacteria (FIB), 22 bacterial, 11 viral, and five protozoan pathogens, and three internal amplification/process controls in many samples. The MFQPCR chip was applied to analyze pathogen removal rates during the wastewater treatment processes. In addition, multiple host-specific MST markers, FIB, and pathogens were successfully quantified in human and avian-impacted surface waters. While the genes for pathogens were relatively infrequently detected, positive correlations were observed between some potential pathogens such as Clostridium perfringens and Mycobacterium spp., and human MST markers. The MFQPCR chips developed in this study, therefore, can provide useful information to monitor and improve water quality.

Inoculation of Freund's adjuvant in European eel (Anguilla anguilla) revealed key KEGG pathways and DEGs of host anti-Edwardsiella anguillarum infection

Freund's complete (FCA) and incomplete adjuvants (FIA), generally applied in subunit fishery vaccine, have not been explored on the molecular mechanism of the nonspecific immune enhancement. In this study, we examined the RNA-seq in the spleen of European eel (Anguilla anguilla) inoculated with FCA and FIA (FCIA group) to elucidate the key KEGG pathways and differential expressed genes (DEGs) in the process of Edwardsiella anguillarum infection and A. anguilla anti-E. anguillarum infection using genome-wide transcriptome. After eels were challenged by E. anguillarum at 28 d post the first inoculation (dpi), compared to the control uninfected eels (Con group), the control infected eels (Con_inf group) showed severe pathological changes in the liver, kidney and spleen, although infected eels post the inoculation of FCIA (FCIA_inf group) also formed slight bleeding. Compared to the FCIA_inf group, there was more than 10 times colony forming unit (cfu) in the Con_inf group per 100 μg spleen, kidney or blood, and the relative percent survival (RPS) of eels was 44.4% in FCIA_inf vs Con_inf. Compared to the Con group, the SOD activity in the FCIA group increased significantly in the liver and spleen. Using high-throughput transcriptomics, DEGs were identified and 29 genes were verified using fluorescence real-time polymerase chain reaction (qRT-PCR). The result of DEGs clustering showed 9 samples in 3 groups of Con, FCIA and FCIA_inf were similar, contrast to distinct differences of 3 samples in the Con_inf group. We found 3795 up and 3548 down regulated DEGs in the compare of FCIA_inf vs Con_inf, of which 5 enriched KEGG pathways of "Lysosome", "Autophagy", "Apoptosis", "C-type lectin receptor signaling" and "Insulin signaling" were ascertained, and 26 of 30 top GO terms in the compare were significantly enriched. Finally, protein-protein interactions between the DEGs of the 5 KEGG pathways and other DEGs were explored using Cytoscape 3.9.1. The compare of FCIA_inf vs Con_inf showed 110 DEGs from the 5 pathways and 718 DEGs from other pathways formed total of 9747° in a network, of which 9 hub DEGs play vital roles in anti-infection or apoptosis. Together, the interaction networks revealed that 9 DEGs involved in the 5 pathways underlies the key process of A. anguilla anti-E. anguillarum infection or host cell apoptosis.

Validation of qPCR from a crude extract for the rapid detection of white spot syndrome virus

White spot disease (WSD) has posed a serious threat to the China and the global shrimp aquaculture. In order to diagnose white spot syndrome virus (WSSV) early and prevent the spread and outbreak of WSD, it is necessary to establish a highly sensitive WSSV diagnosis method suitable for shrimp farming sites. In this study, a pre-amplification qPCR assay from the crude extract of samples heated lysis was established, which was further compared with the universal qPCR assay to verify the shrimp samples. The limit of detection (LOD) of pre-amplification qPCR assay and universal qPCR assay was 2.80 copies and 20.57 copies per reaction at 95% CI, respectively. It had good WSSV specificity and did not show cross-detection of infectious hypodermal and hematopoietic necrosis virus (IHHNV), hepatopancreatic parvovirus (HPV), Enterocytozoon hepatopenaei (EHP), acute hepatopancreas necrosis disease (AHPND), necrotizing hepatopancreatitis bacteria (NHPB), and decapod iridescent virus 1 (DIV1). A total of 36 shrimp samples were detected as WSSV DNA positive by pre-amplification qPCR with crude extract from samples heated lysis and universal qPCR with DNA extraction. The diagnostic sensitivity and specificity were 97.22% (85.5 ~ 99.9%, 95% CI) and 100% (81.5 ~ 100%, 95% CI), respectively. The agreement Kappa value was 0.959 (0.879 ~ 1, 95% CI), and the analysis results were basically consistent. Eliminating the tedious steps of extracting DNA and using pre-amplified qPCR to detect WSSV in shrimp, it is a good choice for aquaculture farms.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s10499-022-00920-9.

Transcriptional Biomarkers and Immunohistochemistry for Detection of Illicit Dexamethasone Administration in Veal Calves

Corticosteroids such as Dexamethasone (DEX) are commonly licensed for therapy in meat animals due to their known pharmacological properties. However, their misuse aimed to achieve anabolic effects is often found by National Residues Control Plans. The setup of a complementary “biomarker based” methods to unveil such illicit practices is encouraged by current European legislation. In this study, the combined use of molecular and histological quantitative techniques was applied on formalin fixed paraffin embedded (FFPE) muscle samples to assess the effects of illicit DEX treatment on veal calves. A PCR array, including 28 transcriptional biomarkers related to DEX exposure, was combined with a histochemical analysis of muscle fiber. An analysis based on unsupervised (PCA) and supervised (PLS-DA and Kohonen’s SOM) methods, was applied in order to define multivariate models able to classify animals suspected of illicit treatment by DEX. According to the conventional univariate approach, a not-significant reduction in type I fibres was recorded in the DEX-treated group, and only 12 out of 28 targeted genes maintained their expected differential expression, confirming the technical limitations of a quantitative analysis on FFPE samples. However, the multivariate models developed highlighted the possibility to establish complementary screening strategies, particularly when based on transcriptional biomarkers characterised by low expression profiles.

Eight weeks of combined exercise training do not alter circulating microRNAs-29a, -133a, -133b, and -155 in young, healthy men

PURPOSE

Individuals with a family history of type 2 diabetes (FH +) have an increased risk of developing type 2 diabetes. Circulating microRNAs (miRNAs) have been implicated as biomarkers of type 2 diabetes risk. Here, we investigated if four circulating miRNAs related to glucose metabolism were altered in men with a FH + and we conducted a preliminary analysis to determine if miRNA expressions were responsive to 8 weeks of combined exercise training.

METHODS

Sixteen young healthy men (mean ± SD; age 22.5 ± 2.5; BMI 26.4 ± 4.0) with FH + or without a family history of type 2 diabetes (FH -) underweight 8 weeks of combined endurance and resistance exercise training (n = 8 FH -; n = 8 FH +). The expression of miR-29a, miR-133a, miR-133b, and miR-155 were measured in serum before and after exercise training. QIAGEN's Ingenuity^® Pathway Analysis was used to examine miRNA target genes and their involvement in glucose metabolism signaling pathways.

RESULTS

There were no differences in miRNA expressions between FH - and FH + . Exercise training did not alter miRNA expressions in either FH - or FH + despite improvements in insulin sensitivity, aerobic capacity, and muscular strength. miR-29a and miR-155 were inversely related to fasting glucose, and miR-133a and miR-133b were negatively correlated with glucose tolerance; however, correlations were not observed with insulin sensitivity.

CONCLUSIONS

The circulating miRNAs- miR-29a, miR-133a, miR-133b, and miR-155 are related to measures of glucose metabolism in healthy, normoglycemic men, but do not reflect peripheral insulin sensitivity or improvements in metabolic health following 8 weeks of combined exercise training.

Gene Expression Studies in Formalin-Fixed Paraffin-Embedded Samples of Cutaneous Cancer: The Need for Reference Genes

Formalin-fixed paraffin-embedded (FFPE) tumour samples may provide crucial data regarding biomarkers for neoplasm progression. Analysis of gene expression is frequently used for this purpose. Therefore, mRNA expression needs to be normalized through comparison to reference genes. In this study, we establish which of the usually reported reference genes is the most reliable one in cutaneous malignant melanoma (MM) and cutaneous squamous cell carcinoma (CSCC). ACTB, TFRC, HPRT1 and TBP expression was quantified in 123 FFPE samples (74 MM and 49 CSCC biopsies) using qPCR. Expression stability was analysed by NormFinder and Bestkeeper softwares, and the direct comparison method between means and SD. The in-silico analysis with BestKeeper indicated that HPRT1 was more stable than ACTB and TFRC in MM (1.85 vs. 2.15) and CSCC tissues (2.09 vs. 2.33). The best option to NormFinder was ACTB gene (0.56) in MM and TFRC (0.26) in CSCC. The direct comparison method showed lower SD means of ACTB expression in MM (1.17) and TFRC expression in CSCC samples (1.00). When analysing the combination of two reference genes for improving stability, NormFinder indicated HPRT1 and ACTB to be the best for MM samples, and HPRT1 and TFRC genes for CSCC. In conclusion, HPRT1 and ACTB genes in combination are the most appropriate choice for normalization in gene expression studies in MM FFPE tissue, while the combination of HPRT1 and TFRC genes are the best option in analysing CSCC FFPE samples. These may be used consistently in forthcoming studies on gene expression in both tumours.

Gene Expression Signature Associated with Clinical Outcome in ALK-Positive Anaplastic Large Cell Lymphoma

Simple Summary

Anaplastic large cell lymphomas associated with ALK translocation have a good outcome after CHOP treatment; however, the 2-year relapse rate remains at 30%. Microarray gene-expression profiling, high throughput RT-qPCR, and RNA sequencing of 48 ALK-positive anaplastic large cell lymphoma (ALK⁺ ALCL) samples obtained at diagnosis enable the identification of genes associated with clinical outcome. More particularly, our molecular signatures indicate that the FN1 gene, a matrix key regulator, might also be involved in the prognosis and the therapeutic response in anaplastic lymphomas.

Abstract

Anaplastic large cell lymphomas associated with ALK translocation have a good outcome after CHOP treatment; however, the 2-year relapse rate remains at 30%. Microarray gene-expression profiling of 48 samples obtained at diagnosis was used to identify 47 genes that were differentially expressed between patients with early relapse/progression and no relapse. In the relapsing group, the most significant overrepresented genes were related to the regulation of the immune response and T-cell activation while those in the non-relapsing group were involved in the extracellular matrix. Fluidigm technology gave concordant results for 29 genes, of which FN1, FAM179A, and SLC40A1 had the strongest predictive power after logistic regression and two classification algorithms. In parallel with 39 samples, we used a Kallisto/Sleuth pipeline to analyze RNA sequencing data and identified 20 genes common to the 28 genes validated by Fluidigm technology—notably, the FAM179A and FN1 genes. Interestingly, FN1 also belongs to the gene signature predicting longer survival in diffuse large B-cell lymphomas treated with CHOP. Thus, our molecular signatures indicate that the FN1 gene, a matrix key regulator, might also be involved in the prognosis and the therapeutic response in anaplastic lymphomas.

Tutorial: Guidelines for Single-Cell RT-qPCR

Reverse transcription quantitative PCR (RT-qPCR) has delivered significant insights in understanding the gene expression landscape. Thanks to its precision, sensitivity, flexibility, and cost effectiveness, RT-qPCR has also found utility in advanced single-cell analysis. Single-cell RT-qPCR now represents a well-established method, suitable for an efficient screening prior to single-cell RNA sequencing (scRNA-Seq) experiments, or, oppositely, for validation of hypotheses formulated from high-throughput approaches. Here, we aim to provide a comprehensive summary of the scRT-qPCR method by discussing the limitations of single-cell collection methods, describing the importance of reverse transcription, providing recommendations for the preamplification and primer design, and summarizing essential data processing steps. With the detailed protocol attached in the appendix, this tutorial provides a set of guidelines that allow any researcher to perform scRT-qPCR measurements of the highest standard.

miR-181c level predicts response to exercise training in patients with heart failure and preserved ejection fraction: an analysis of the OptimEx-Clin trial

AIMS

In patients with heart failure with preserved ejection fraction (HFpEF), exercise training improves the quality of life and aerobic capacity (peakV·O2). Up to 55% of HF patients, however, show no increase in peakV·O2 despite adequate training. We hypothesized that circulating microRNAs (miRNAs) can distinguish exercise low responders (LR) from exercise high responders (HR) among HFpEF patients.

METHODS AND RESULTS

We selected HFpEF patients from the Optimizing Exercise Training in Prevention and Treatment of Diastolic HF (OptimEx) study which attended ≥70% of training sessions during 3 months (n = 51). Patients were defined as HR with a change in peakV·O2 above median (6.4%), and LR as below median (n = 30 and n = 21, respectively). Clinical, ergospirometric, and echocardiographic characteristics were similar between LR and HR. We performed an miRNA array (n = 377 miRNAs) in 14 age- and sex-matched patients. A total of 10 miRNAs were upregulated in LR, of which 4 correlated with peakV·O2. Validation in the remaining 37 patients indicated that high miR-181c predicted reduced peakV·O2 response (multiple linear regression, β = -2.60, P = 0.011), and LR status (multiple logistic regression, odds ratio = 0.48, P = 0.010), independent of age, sex, body mass index, and resting heart rate. Furthermore, miR-181c decreased in LR after exercise training (P-group = 0.030, P-time = 0.048, P-interaction = 0.037). An in silico pathway analysis identified several downstream targets involved in exercise adaptation.

CONCLUSIONS

Circulating miR-181c is a marker of the response to exercise training in HFpEF patients. High miR-181c levels can aid in identifying LR prior to training, providing the possibility for individualized management.

Design of a High-Throughput Real-Time PCR System for Detection of Bovine Respiratory and Enteric Pathogens

Bovine respiratory and enteric diseases have a profound negative impact on animal, health, welfare, and productivity. A vast number of viruses and bacteria are associated with the diseases. Pathogen detection using real-time PCR (rtPCR) assays performed on traditional rtPCR platforms are costly and time consuming and by that limit the use of diagnostics in bovine medicine. To diminish these limitations, we have developed a high-throughput rtPCR system (BioMark HD; Fluidigm) for simultaneous detection of the 11 most important respiratory and enteric viral and bacterial pathogens. The sensitivity and specificity of the rtPCR assays on the high-throughput platform was comparable with that of the traditional rtPCR platform. Pools consisting of positive and negative individual field samples were tested in the high-throughput rtPCR system in order to investigate the effect of an individual sample in a pool. The pool tests showed that irrespective of the size of the pool, a high-range positive individual sample had a high influence on the cycle quantification value of the pool compared with the influence of a low-range positive individual sample. To validate the test on field samples, 2,393 nasal swab and 2,379 fecal samples were tested on the high-throughput rtPCR system as pools in order to determine the occurrence of the 11 pathogens in 100 Danish herds (83 dairy and 17 veal herds). In the dairy calves, Pasteurella multocida (38.4%), rotavirus A (27.4%), Mycoplasma spp. (26.2%), and Trueperella pyogenes (25.5%) were the most prevalent pathogens, while P. multocida (71.4%), Mycoplasma spp. (58.9%), Mannheimia haemolytica (53.6%), and Mycoplasma bovis (42.9%) were the most often detected pathogens in the veal calves. The established high-throughput system provides new possibilities for analysis of bovine samples, since the system enables testing of multiple samples for the presence of different pathogens in the same analysis test even with reduced costs and turnover time.

Estimating Clinically Relevant Cut-Off Values for a High-Throughput Quantitative Real-Time PCR Detecting Bacterial Respiratory Pathogens in Cattle

Bovine respiratory disease (BRD) results from interactions between pathogens, environmental stressors, and host factors. Obtaining a diagnosis of the causal pathogens is challenging but the use of high-throughput real-time PCR (rtPCR) may help target preventive and therapeutic interventions. The aim of this study was to improve the interpretation of rtPCR results by analysing their associations with clinical observations. The objective was to develop and illustrate a field-data driven statistical method to guide the selection of relevant quantification cycle cut-off values for pathogens associated with BRD for the high-throughput rtPCR system "Fluidigm BioMark HD" based on nasal swabs from calves. We used data from 36 herds enrolled in a Danish field study where 340 calves within pre-determined age-groups were subject to clinical examination and nasal swabs up to four times. The samples were analysed with the rtPCR system. Each of the 1,025 observation units were classified as sick with BRD or healthy, based on clinical scores. The optimal rtPCR results to predict BRD were investigated for Pasteurella multocida, Mycoplasma bovis, Histophilus somni, Mannheimia haemolytica, and Trueperella pyogenes by interpreting scatterplots and results of mixed effects logistic regression models. The clinically relevant rtPCR cut-off suggested for P. multocida and M. bovis was ≤ 21.3. For H. somni it was ≤ 17.4, while no cut-off could be determined for M. haemolytica and T. pyogenes. The demonstrated approach can provide objective support in the choice of clinically relevant cut-offs. However, for robust performance of the regression model sufficient amounts of suitable data are required.

An improved method for specific-target preamplification PCR analysis of single blastocysts useful for embryo sexing and high-throughput gene expression analysis

Gene expression analysis in preimplantation embryos has been used for answering fundamental questions related to development, prediction of pregnancy outcome, and other topics. Limited amounts of mRNA in preimplantation embryos hinders progress in studying the preimplantation embryo. Here, a method was developed involving direct synthesis and specific-target preamplification (STA) of cDNA for gene expression analysis in single blastocysts. Effective cell lysis and genomic DNA removal steps were incorporated into the method. In addition, conditions for real-time PCR of cDNA generated from these processes were improved. By using this system, reliable embryo sexing results based on expression of sex-chromosome linked genes was demonstrated. Calibration curve analysis of PCR results using the Fluidigm Biomark microfluidic platform (Fluidigm, South San Francisco, CA) was performed to evaluate 96 STA cDNA from single blastocysts. In total, 93.75% of the genes were validated. Robust amplification was detected even when STA cDNA from a single blastocyst was diluted 1,024-fold. Further analysis showed that within-assay variation increased when cycle threshold values exceeded 18. Overall, STA quantitative real-time PCR analysis was shown to be useful for analysis of gene expression of multiple specific targets in single blastocysts.

Pre-amplification as a method for improvement of quantitative RT-PCR analysis of circulating miRNAs

Introduction

The assessment of circulating miRNAs is challenging and still limited due to their low concentrations, small size and lack of reference values in human biological samples. Pre-amplification of complementary DNAs may facilitate reliable miRNA quantification. The aim of our study was to evaluate the efficacy of pre-amplification as a step to increase the sensitivity of qPCR analysis for five candidate circulating miRNAs presumably related to toxic metals and cigarette smoke exposure: miR-1537, miR-190b, miR-16, miR-21, and miR-146a.

Materials and methods

Candidate miRNAs expression was analysed in plasma samples of 19 mother-newborn pairs. For isolation, transcription, pre-amplification and qPCR quantification kits and protocols by Qiagen (Hilden, Germany) were used. Paired t-test or Wilcoxon rank test were used to compare miRNAs expression levels with and without a pre-amplification step prior to qPCR, separately in maternal and cord plasma. Intraclass correlation (ICC) was calculated as an agreement measure between procedures for each miRNA.

Results

Pre-amplification facilitated the detection of all assayed miRNAs with an overall cycle threshold (C_T) improvement of 6.6 ± 0.89 (P < 0.05). Excellent ICCs (> 0.90) were found between data for preamplified and not preamplified miR-16, miR-21 and miR-146a. However, these correlations for low expressed miR-190b were moderate (0.79 in maternal; 0.61 in cord plasma) and poor for miR-1537 (0.49 in maternal; no correlation in cord plasma).

Conclusion

Pre-amplification is a useful, necessary step in the analysis of miR-1537 and miR-190b as a reliable procedure facilitating extracellular miRNA expression detection in human plasma by real-time PCR quantification.

Bona fide gene expression analysis of samples from the bovine reproductive system by microfluidic platform

Sample types such as those from reproductive systems often yield scarce material, which limits RT-qPCR analysis to only a few targets. Recently developed high-throughput systems can potentially change this scenario, however, the nanoliter scale of such platforms requires extra processing, e.g., preamplification, which needs to be defined through observation and experience. In order to establish best practices in high-throughput PCR approaches using samples from reproductive systems, we evaluated the Biomark™ HD performance using 11 different sample types from the bovine reproductive system: blastocyst (single/pool), oocyte (pool), cumulus, granulosa, and theca cells, oviduct tissue, fetal ovary, testicle (adult/fetal), and uterine horn. We observed that the preamplification step is not just reliable, but mandatory. Our results indicated that 14-preamplification cycles associated to 5- and 7-fold-dilution is the best approach for those samples. Additionally, the Biomark™ HD system has a high intra and inter reproducibility, therefore its performance in duplicate is unnecessary for the ΔCq analysis, taking in consideration the cutoff value 4 < Cq < 22. In summary, this high-throughput approach is a reliable and excellent tool for studying the bovine reproductive system, especially using quantitatively-limited samples, as a larger number of target genes can be assessed from a very low amount of starting material.

Development of a high-throughput real-time PCR system for detection of enzootic pathogens in pigs

Respiratory and intestinal diseases in pigs can have significant negative influence on productivity and animal welfare. A wide range of real-time PCR (rtPCR) assays are used in our laboratory (National Veterinary Institute, Technical University of Denmark) for pathogen detection, and PCR analyses are performed on traditional rtPCR platforms in which a limited number of samples can be analyzed per day given limitations in equipment and personnel. To mitigate these restrictions, rtPCR assays have been optimized for the high-throughput rtPCR BioMark platform (Fluidigm). Using this platform, we developed a high-throughput detection system that can be used for simultaneous examination of 48 samples with detection specificity for 18 selected respiratory and enteric viral and bacterial pathogens of high importance to Danish pig production. The rtPCR assays were validated and optimized to run under the same reaction conditions using a BioMark 48.48 dynamic array (DA) integrated fluidic circuit chip, and the sensitivity and specificity were assessed by testing known positive samples. Performance of the 48.48DA was similar to traditional rtPCR analysis, and the specificity of the 48.48DA was high. Application of the high-throughput platform has resulted in a significant reduction in cost and working hours and has provided production herds with a new innovative service with the potential to facilitate the optimal choice of disease control strategies such as vaccination and treatment.

Validation of molecular biomarkers for preoperative diagnostics of human papillary thyroid carcinoma in fine needle aspirates

Background

Despite substantial efforts, reliable preoperative diagnostic for human thyroid malignancies in case of cytologically indeterminate nodules is still missing, resulting in high number of unnecessary thyroidectomies. In an attempt to increase precision of existing preoperative diagnostics, we aimed at validating the panel of molecular biomarkers predictive for papillary thyroid carcinoma (PTC) in preoperative fine needle aspirate (FNA) samples.

Methods

In this prospective study conducted in preoperative thyroid FNA from 44 thyroid nodules, expression levels of 11 molecular biomarkers previously validated on the postoperative samples of PTCs were measured by Cell-to-CT and QuantiGene Plex methods and correlated with final diagnosis.

Results

The QuantiGene Plex resulted in reliable gene expression measurements for FNA and core-needle biopsy (CNB) samples, however this method was less sensitive than pre-amplification based Cell-to-CT. Measurements conducted on the same samples by the two methods significantly correlated for most of the genes. Expression levels of TIMP1, c-MET and ARNTL were upregulated in PTC nodules as compared to benign counterparts, supporting previous post-operative studies. Strong correlation was observed between these biomarker alterations in the same samples. Within the sub-group of 15 indeterminate nodules (Bethesda II-V), TIMP1 had 100% specificity and 83% sensitivity for PTC cases.

Conclusions

Assessment of TIMP1, c-MET and core-clock gene ARNTL expression levels by QuantiGene Plex assay in FNA samples holds promise as an ancillary method to the cytological preoperative diagnostics.

Triage of high-risk HPV-positive women in population-based screening by miRNA expression analysis in cervical scrapes; a feasibility study

Background

Primary testing for high-risk HPV (hrHPV) is increasingly implemented in cervical cancer screening programs. Many hrHPV-positive women, however, harbor clinically irrelevant infections, demanding additional disease markers to prevent over-referral and over-treatment. Most promising biomarkers reflect molecular events relevant to the disease process that can be measured objectively in small amounts of clinical material, such as miRNAs. We previously identified eight miRNAs with altered expression in cervical precancer and cancer due to either methylation-mediated silencing or chromosomal alterations. In this study, we evaluated the clinical value of these eight miRNAs on cervical scrapes to triage hrHPV-positive women in cervical screening.

Results

Expression levels of the eight candidate miRNAs in cervical tissue samples (n = 58) and hrHPV-positive cervical scrapes from a screening population (n = 187) and cancer patients (n = 38) were verified by quantitative RT-PCR. In tissue samples, all miRNAs were significantly differentially expressed (p < 0.05) between normal, high-grade precancerous lesions (CIN3), and/or cancer. Expression patterns detected in cervical tissue samples were reflected in cervical scrapes, with five miRNAs showing significantly differential expression between controls and women with CIN3 and cancer. Using logistic regression analysis, a miRNA classifier was built for optimal detection of CIN3 in hrHPV-positive cervical scrapes from the screening population and its performance was evaluated using leave-one-out cross-validation. This miRNA classifier consisted of miR-15b-5p and miR-375 and detected a major subset of CIN3 as well as all carcinomas at a specificity of 70%. The CIN3 detection rate was further improved by combining the two miRNAs with HPV16/18 genotyping. Interestingly, both miRNAs affected the viability of cervical cancer cells in vitro.

Conclusions

This study shows that miRNA expression analysis in cervical scrapes is feasible and enables the early detection of cervical cancer, thus underlining the potential of miRNA expression analysis for triage of hrHPV-positive women in cervical cancer screening.

Electronic supplementary material

The online version of this article (10.1186/s13148-018-0509-9) contains supplementary material, which is available to authorized users.

Subtyping of Swine Influenza Viruses Using a High-Throughput Real-Time PCR Platform

Influenza A viruses (IAVs) are important human and animal pathogens with high impact on human and animal health. In Denmark, a passive surveillance program for IAV in pigs has been performed since 2011, where screening tests and subsequent subtyping are performed by reverse transcription quantitative real-time PCR (RT-qPCR). A disadvantage of the current subtyping system is that several assays are needed to cover the wide range of circulating subtypes, which makes the system expensive and time-consuming. Therefore, the aim of the present study was to develop a high-throughput method, which could improve surveillance of swine influenza viruses (swIAVs) and lower the costs of virus subtyping. Twelve qPCR assays specific for various hemagglutinin and neuraminidase gene lineages relevant for swIAV and six assays specific for the internal genes of IAV were developed and optimized for the high-throughput qPCR platform BioMark (Fluidigm). The qPCR assays were validated and optimized to run under the same reaction conditions using a 48.48 dynamic array (48.48DA). The sensitivity and specificity was assessed by testing virus isolates and field samples with known subtypes. The results revealed a performance of the swIAV 48.48DA similar to conventional real-time analysis, and furthermore, the specificity of swIAV 48.48DA was very high and without cross reactions between the assays. This high-throughput system provides a cost-effective alternative for subtyping of swIAVs.

A Strategy to Find Suitable Reference Genes for miRNA Quantitative PCR Analysis and Its Application to Cervical Specimens

miRNAs represent an emerging class of promising biomarkers for cancer diagnostics. To perform reliable miRNA expression analysis using quantitative PCR, adequate data normalization is essential to remove nonbiological, technical variations. Ideal reference genes should be biologically stable and reduce technical variability of miRNA expression analysis. Herein is a new strategy for the identification and evaluation of reference genes that can be applied for miRNA-based diagnostic tests without entailing excessive additional experiments. We analyzed the expression of 11 carefully selected candidate reference genes in different types of cervical specimens [ie, tissues, scrapes, and self-collected cervicovaginal specimens (self-samples)]. To identify the biologically most stable reference genes, three commonly used algorithms (GeNorm, NormFinder, and BestKeeper) were combined. Signal-to-noise ratios and P values between control and disease groups were calculated to validate the reduction in technical variability on expression analysis of two marker miRNAs. miR-423 was identified as a suitable reference gene for all sample types, to be used in combination with RNU24 in cervical tissues, RNU43 in scrapes, and miR-30b in self-samples. These findings demonstrate that the choice of reference genes may differ between different types of specimens, even when originating from the same anatomical source. More important, it is shown that adequate normalization increases the signal-to-noise ratio, which is not observed when normalizing to commonly used reference genes.

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

Background

Mechanistic 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.

Methods

Single 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.

Results

After 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.

Discussion

Our 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.

Recommendations for mRNA analysis of micro-dissected glomerular tufts from paraffin-embedded human kidney biopsy samples

Background

Glomeruli are excellent pre-determined natural structures for laser micro-dissection. Compartment-specific glomerular gene expression analysis of formalin-fixed paraffin-embedded renal biopsies could improve research applications. The major challenge for such studies is to obtain good-quality RNA from small amounts of starting material, as applicable for the analysis of glomerular compartments. In this work, we provide data and recommendations for an optimized workflow of glomerular mRNA analysis.

Results

With a proper resolution of the camera and screen provided by the next generation of micro-dissection systems, we are able to separate parietal epithelial cells from glomerular tufts. Selected compartment-specific transcripts (WT1 and GLEPP1 for glomerular tuft as well as PAX2 for parietal epithelial cells) seem to be reliable discriminators for these micro-dissected glomerular substructures. Using the phenol–chloroform extraction and hemalaun-stained sections (2 µm), high amounts of Bowman’s capsule transections (> 300) reveal sufficient RNA concentrations (> 300 ng mRNA) for further analysis. For comparison, in unstained sections from a number of 60 glomerular transections upwards, a minimum amount of 157 ng mRNA with a reasonable mRNA purity [A260/A280 ratio of 1.5 (1.4/1.7) median (25th/75th percentiles)] was reversely transcribed into cDNA. Comparing the effect of input RNA (20, 60, 150 and 300 micro-dissected glomerular transections), transcript expression of POLR2A significantly correlated when 60 and 150 laser micro-dissected glomerular transections were used for analysis. There was a lower inter-assay coefficient of variability for ADAMTS13, when at least 60 glomerular transections were used. According to the algorithms of geNormPlus and NormFinder, PGK1 and PPIA are more stable glomerular reference transcripts compared to GUSB, GAPDH, POLR2A, RPLPO, TBP, B2M, ACTB, 18SrRNA and HMBS.

Conclusions

Our approach implements compartment-specific glomerular mRNA expression analysis into research applications, even regarding glomerular substructures like parietal epithelial cells. We recommend using of at least 60 micro-dissected unstained glomerular or 300 hemalaun-stained Bowman’s capsule transections to obtain sufficient input mRNA for reproducible results. Hereby, the range of RNA concentrations in 60 micro-dissected glomeruli is low and appropriate normalization of C_q values using our suggested reference transcripts (PGK1 and PPIA) allows compensation with respect to different amounts of RNA purity and quantity.

Electronic supplementary material

The online version of this article (10.1186/s12867-018-0103-x) contains supplementary material, which is available to authorized users.

MicroRNA profiling in plasma samples using qPCR arrays: Recommendations for correct analysis and interpretation

MicroRNA (miRNA) regulate gene expression through posttranscriptional mRNA degradation or suppression of translation. Many (pre)analytical issues remain to be resolved for miRNA screening with TaqMan Low Density Arrays (TLDA) in plasma samples, such as optimal RNA isolation, preamplification and data normalization. We optimized the TLDA protocol using three RNA isolation protocols and preamplification dilutions. By using 100μL elution volume during RNA isolation and adding a preamplification step without dilution, 49% of wells were amplified. Informative target miRNA were defined as having quantification cycle values ≤35 in at least 20% of samples and low technical variability (CV across 2 duplicates of 1 sample <4%). A total of 218 miRNA was considered informative (= 59% of all target miRNA). Different normalization strategies were compared: exogenous Ath-miR-159a, endogenous RNA U6, and three mathematical normalization techniques: geNorm (Qbase, QB) and NormFinder (NF) normalization algorithms, and global mean calculation. To select the best normalization method, technical variability, biological variability, stability, and the extent to which the normalization method reduces data dispersion were calculated. The geNorm normalization algorithm reduced data dispersion to the greatest extent, while endogenous RNA U6 performed worst. In conclusion, for miRNA profiling in plasma samples using TLDA cards we recommend: 1. Implementing a preamplification step in the TLDA protocol without diluting the final preamplification product 2. A stepwise approach to exclude non-informative miRNA based on quality control parameters 3. Against using snoRNA U6 as normalization method for relative quantification 4. Using the geNorm algorithm as normalization method for relative quantification.

Resolving Species Level Changes in a Representative Soil Bacterial Community Using Microfluidic Quantitative PCR

Rapid advances in genome sequencing technologies enable determination of relative bacterial abundances and community composition, yet, changes at the species level remain difficult to detect despite importance for certain ecological inferences. We present a method for extraction and direct quantification of species composition of a predefined multispecies bacterial community using microfluidic-based quantitative real-time PCR (qPCR). We employ a nested PCR approach based on universal 16S rRNA gene pre-amplification followed by detection and quantification of absolute abundance of bacterial species using microfluidic array of parallel singleplex qPCR reactions. Present microfluidic qPCR supports 2,304 simultaneous reactions on a single chip, while automatic distribution of samples and reactants minimizes pipetting errors and technical variations. The utility of the method is illustrated using a synthetic soil bacterial community grown in two contrasting environments – sand microcosms and batch cultures. The protocol entails extraction of total nucleic acid, preparation of genomic DNA, and steps for qPCR assessment of bacterial community composition. This method provides specific and sensitive quantification of bacterial species requiring only 2 ng of community DNA. Optimized extraction protocol and preamplification step allow for rapid, quantitative, and simultaneous detection of candidate species with high throughput. The proposed method offers a simple and accurate alternative to present sequencing methods especially when absolute values of species abundance are required. Quantification of changes at the species level contributes to the mechanistic understanding of the roles of particular species in a bacterial community functioning.

Toward biotechnology in space: High-throughput instruments for in situ biological research beyond Earth

Space biotechnology is a nascent field aimed at applying tools of modern biology to advance our goals in space exploration. These advances rely on our ability to exploit in situ high throughput techniques for amplification and sequencing DNA, and measuring levels of RNA transcripts, proteins and metabolites in a cell. These techniques, collectively known as "omics" techniques have already revolutionized terrestrial biology. A number of on-going efforts are aimed at developing instruments to carry out "omics" research in space, in particular on board the International Space Station and small satellites. For space applications these instruments require substantial and creative reengineering that includes automation, miniaturization and ensuring that the device is resistant to conditions in space and works independently of the direction of the gravity vector. Different paths taken to meet these requirements for different "omics" instruments are the subjects of this review. The advantages and disadvantages of these instruments and technological solutions and their level of readiness for deployment in space are discussed. Considering that effects of space environments on terrestrial organisms appear to be global, it is argued that high throughput instruments are essential to advance (1) biomedical and physiological studies to control and reduce space-related stressors on living systems, (2) application of biology to life support and in situ resource utilization, (3) planetary protection, and (4) basic research about the limits on life in space. It is also argued that carrying out measurements in situ provides considerable advantages over the traditional space biology paradigm that relies on post-flight data analysis.

Removal of human pathogenic viruses in a down-flow hanging sponge (DHS) reactor treating municipal wastewater and health risks associated with utilization of the effluent for agricultural irrigation

A down-flow hanging sponge (DHS) reactor has been developed as a cost-effective wastewater treatment system that is adaptable to local conditions in low-income countries. A pilot-scale DHS reactor previously demonstrated stable reduction efficiencies for chemical oxygen demand (COD) and ammonium nitrogen over a year at ambient temperature, but the pathogen reduction efficiency of the DHS reactor has yet to be investigated. In the present study, the reduction efficiency of a pilot-scale DHS reactor fed with municipal wastewater was investigated for 10 types of human pathogenic viruses (norovirus GI, GII and GIV, aichivirus, astrovirus, enterovirus, hepatitis A and E viruses, rotavirus, and sapovirus). DHS influent and effluent were collected weekly or biweekly for 337 days, and concentrations of viral genomes were determined by microfluidic quantitative PCR. Aichivirus, norovirus GI and GII, enterovirus, and sapovirus were frequently detected in DHS influent, and the log₁₀ reduction (LR) of these viruses ranged from 1.5 to 3.7. The LR values for aichivirus and norovirus GII were also calculated using a Bayesian estimation model, and the average LR (±standard deviation) values for aichivirus and norovirus GII were estimated to be 1.4 (±1.5) and 1.8 (±2.5), respectively. Quantitative microbial risk assessment was conducted to calculate a threshold reduction level for norovirus GII that would be required for the use of DHS effluent for agricultural irrigation, and it was found that LRs of 2.6 and 3.7 for norovirus GII in the DHS effluent were required in order to not exceed the tolerable burden of disease at 10^-4 and 10^-6 disability-adjusted life years loss per person per year, respectively, for 95% of the exposed population during wastewater reuse for irrigation.

Amy2B copy number variation reveals starch diet adaptations in ancient European dogs

Extant dog and wolf DNA indicates that dog domestication was accompanied by the selection of a series of duplications on the Amy2B gene coding for pancreatic amylase. In this study, we used a palaeogenetic approach to investigate the timing and expansion of the Amy2B gene in the ancient dog populations of Western and Eastern Europe and Southwest Asia. Quantitative polymerase chain reaction was used to estimate the copy numbers of this gene for 13 ancient dog samples, dated to between 15 000 and 4000 years before present (cal. BP). This evidenced an increase of Amy2B copies in ancient dogs from as early as the 7th millennium cal. BP in Southeastern Europe. We found that the gene expansion was not fixed across all dogs within this early farming context, with ancient dogs bearing between 2 and 20 diploid copies of the gene. The results also suggested that selection for the increased Amy2B copy number started 7000 years cal. BP, at the latest. This expansion reflects a local adaptation that allowed dogs to thrive on a starch rich diet, especially within early farming societies, and suggests a biocultural coevolution of dog genes and human culture.

The focus on sample quality: Influence of colon tissue collection on reliability of qPCR data

Successful molecular analyses of human solid tissues require intact biological material with well-preserved nucleic acids, proteins, and other cell structures. Pre-analytical handling, comprising of the collection of material at the operating theatre, is among the first critical steps that influence sample quality. The aim of this study was to compare the experimental outcomes obtained from samples collected and stored by the conventional means of snap freezing and by PAXgene Tissue System (Qiagen). These approaches were evaluated by measuring rRNA and mRNA integrity of the samples (RNA Quality Indicator and Differential Amplification Method) and by gene expression profiling. The collection procedures of the biological material were implemented in two hospitals during colon cancer surgery in order to identify the impact of the collection method on the experimental outcome. Our study shows that the pre-analytical sample handling has a significant effect on the quality of RNA and on the variability of qPCR data. PAXgene collection mode proved to be more easily implemented in the operating room and moreover the quality of RNA obtained from human colon tissues by this method is superior to the one obtained by snap freezing.

Expression profiling of genes involved in drought stress and leaf senescence in juvenile barley

BACKGROUND

Drought stress in juvenile stages of crop development and premature leaf senescence induced by drought stress have an impact on biomass production and yield formation of barley (Hordeum vulgare L.). Therefore, in order to get information of regulatory processes involved in the adaptation to drought stress and leaf senescence expression analyses of candidate genes were conducted on a set of 156 barley genotypes in early developmental stages, and expression quantitative trait loci (eQTL) were identified by a genome wide association study.

RESULTS

Significant effects of genotype and treatment were detected for leaf colour measured at BBCH 25 as an indicator of leaf senescence and for the expression level of the genes analysed. Furthermore, significant correlations were detected within the group of genes involved in drought stress (r = 0.84) and those acting in leaf senescence (r = 0.64), as well as between leaf senescence genes and the leaf colour (r = 0.34). Based on these expression data and 3,212 polymorphic single nucleotide polymorphisms (SNP) with a minor allele frequency >5% derived from the Illumina 9 k iSelect SNP Chip, eight cis eQTL and seven trans eQTL were found. Out of these an eQTL located on chromosome 3H at 142.1 cM is of special interest harbouring two drought stress genes (GAD3 and P5CS2) and one leaf senescence gene (Contig7437), as well as an eQTL on chromosome 5H at 44.5 cM in which two genes (TRIUR3 and AVP1) were identified to be associated to drought stress tolerance in a previous study.

CONCLUSION

With respect to the expression of genes involved in drought stress and early leaf senescence, genotypic differences exist in barley. Major eQTL for the expression of these genes are located on barley chromosome 3H and 5H. Respective markers may be used in future barley breeding programmes for improving tolerance to drought stress and leaf senescence.

Evaluation of bias associated with high-multiplex, target-specific pre-amplification

We developed a novel PCR-based pre-amplification (PreAmp) technology that can increase the abundance of over 350 target genes one million-fold. To assess potential bias introduced by PreAmp we utilized ERCC RNA reference standards, a model system that quantifies measurement error in RNA analysis. We assessed three types of bias: amplification bias, dynamic range bias and fold-change bias. We show that our PreAmp workflow introduces only minimal amplification and fold-change bias under stringent conditions. We do detect dynamic range bias if a target gene is highly abundant and PreAmp occurred for 16 or more PCR cycles; however, this type of bias is easily correctable. To assess PreAmp bias in a gene expression profiling experiment, we analyzed a panel of genes that are regulated during differentiation using the NTera2 stem cell model system. We find that results generated using PreAmp are similar to results obtained using standard qPCR (without the pre-amplification step). Importantly, PreAmp maintains patterns of gene expression changes across samples; the same biological insights would be derived from a PreAmp experiment as with a standard gene expression profiling experiment. We conclude that our PreAmp technology can facilitate analysis of extremely limited samples in gene expression quantification experiments.