A prospective, international, multisite comparison of platelet isolation techniques for genome-wide transcriptomics: Communication from the SSC of the ISTH
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ABSTRACT: Genome-wide platelet transcriptomics is increasingly being used to uncover new aspects of platelet biology and as a diagnostic and prognostic tool. Nevertheless, platelet isolation methods for transcriptomic studies are not standardized, introducing challenges for cross-study comparisons, data integration, and replication. In this prospective multicenter study, we assessed how three of the most commonly-used platelet isolation protocols influence metrics from next-generation bulk RNA sequencing and functional assays. Compared with washing alone, more stringent removal of leukocytes by anti-CD45+ beads or PALL filters resulted in sufficient quantity of RNA for next-generation sequencing and similar quality of RNA sequencing metrics. The more stringent removal of leukocytes resulted in lower relative expression of known leukocyte-specific genes and higher relative expression of known platelet-specific genes. The results were consistent across enrolling sites, suggesting that the techniques are transferrable and reproducible. The use of anti-CD45+ beads reduced integrin aIIbb3 activation to PAR-1 activating peptide (SFLLRN-TRAP) but not ADP, compared to washing alone, while the isolation method had no influence on basal platelet reactivity. In conclusion, genome-wide transcriptional and functional assays in platelets are influenced by isolation technique. These results should help the research community make informed choices about platelet isolation techniques in their own platelet studies.
Project description:We developed a novel approach to isolate tumor cells with high purity from bone marrow which was subjected to immunomagnetic enrichment using EpCAM beads followed by fluorescence activated cell sorting (IE/FACS) to isolate EpCAM-positive cells away from leukocytes (CD45+). For RNA profiling, QPCR analysis was performed on sixty four (64) cancer-related genes using Taqman® low density arrays. For non-tumor controls, RNA profiling was performed on matched leukocytes (CD45+) isolated from the same enriched bone marrow samples from 17 of the 30 patients.
Project description:Post-hybridization washing is an essential part of microarray experiments. Both, the quality of the experimental washing protocol and the adequate consideration of washing in intensity calibration ultimately affect the quality of the expression estimates extracted from the microarray intensities. We conducted experiments on GeneChip microarrays with altered protocols for washing, scanning and staining to study the probe-level intensity changes as a function of washing cycles. Particularly, three Affymetrix GeneChip HGU133plus2 arrays were hybridized and equilibrated for 16 hours in the hybridization oven. For one of the three arrays washing and staining was performed according to the manufacturer’s instructions. For another array the first scan was done immediately after low stringent wash and staining without intermitting stringent washing. Then, the array was stringently washed and scanned in alternating order three more times where each washing step consists of a definite number of washing cycles. The third array was low stringently washed followed by two stringent washing cycles and staining before the first scan. Subsequently it was analogously processed as array A. All three chips are repeatedly processed in a second series of alternating wash/scan-cycles which was performed using the same protocol for each chip as in the first series as described above. As in the first series the arrays were also stained a second time to compensate for any loss of bleached fluorescent dye. Analysis of the washing kinetics shows that the signal-to-noise ratio doubles roughly every ten stringent washing cycles. Washing can be characterized by time-dependent rate constants which reflect the heterogeneous character of target binding to microarray probes. We propose an empirical washing function which estimates the survival of probe bound targets. The washing function allows calibrating probe intensities for the effect of washing. On a relative scale, proper calibration for washing markedly increases expression measures especially in the limit of small and large values.
Project description:Parallel DNA and RNA profiling of EpCAM-positive cells in bone marrow and primary tumor tissue with positive disseminated tumor cell (DTC) count via immunomagnetic Enrichment/Flow Cytometry (IE/FC) of metastatic breast cancer (MBC) patients confirm their malignant nature We developed a novel approach to isolate tumor cells with high purity from bone marrow which was subjected to immunomagnetic enrichment using EpCAM beads followed by fluorescence activated cell sorting (IE/FACS) to isolate EpCAM-positive cells away from leukocytes (CD45+). For DNA profiling, sorted cells were subjected to BAC array comparative genomic hybridization analysis following whole genome amplification. For RNA profiling, QPCR analysis was performed on sixty four (64) cancer-related genes using Taqman® low density arrays. For non-tumor controls, RNA profiling was performed on matched leukocytes (CD45+) isolated from the same enriched bone marrow samples.
Project description:0.3g of flowers were ground in liquid nitrogen. The powder was extracted for 30 min [H2] in 1.5 ml of lysis buffer (50mM Tris HCl pH 8.0, 50mM NaCl, 1% Triton x-100 and 1 x cOmplete™ EDTA-free protease inhibitor (Roche)). After removal of cell debris by centrifugation (2 times 10 min, 16000 x g, 4 °C) the cleared supernatants were incubated for 30 min with GFP or FLAG antibodies coupled to magnetic microbeads (μMACS GFP and DYKDDDDK isolation Kits, Miltenyi). Beads were loaded on magnetized MACS separation columns equilibrated with lysis buffer and washed 4 times with 300 µl washing buffer (50mM Tris HCL pH 7.5, 25 or 50 mM NaCl, 0,1 % Triton). Samples were eluted in 50 µl of pre-warmed elution buffer (Milteny). Control IPS were performed in Col-O using either GFP or FLAG antibodies.
Project description:Comparison of gene expression between aortic adventitial Sca-1+CD45+ progenitor cells and Sca-1-CD45+ or Sca-1+CD45- cells. The hypothesis tested was that Sca-1+CD45+ cells would differentially express genes relating to angiogenesis and vasculogenesis when compared to Sca-1-CD45+ leukocytes.
Project description:We developed a novel approach to isolate tumor cells with high purity from blood which was subjected to immunomagnetic enrichment using EpCAM beads followed by fluorescence activated cell sorting (IE/FACS) to isolate EpCAM-positive cells away from leukocytes (CD45+). Duplicate samples of 20 cells were isolated from the same enriched blood from MBC patients and then subjected to DNA and RNA profiling in parallel. For DNA profiling, sorted cells were subjected to BAC array comparative genomic hybridization analysis following whole genome amplification. For RNA profiling, QPCR analysis was performed on sixty four (64) cancer-related genes using Taqman® low density arrays.
Project description:Platelets are small anucleate cells derived from the fragmentation of megakaryocytes and are involved in different biological processes especially hemostasis, thrombosis and immune response. Platelet purification is a crucial step in transcriptomic analysis, and researchers usually encounter the problem of platelet contamination by leukocytes and erythrocytes. Leukocytes contain much more RNA than platelets, thus the presence of few contaminants in platelet preparation can strongly alter transcriptome results. Using microarray technique, we compared transcriptome of platelets from the same donor, purified by common centrifugation method or using magnetic microbeads to eliminate contaminating cells.
Project description:FLAG-GFP tagged LIN-41 was immunoprecipitated using FLAG dynabeads (Sigma) from lysates of young adult C.elegans. After washing steps, bound fraction (IP) was eluted from beads and associated RNAs were isolated by using the Pico pure RNA isloation kit (Invitrogen)