Absolute quantification of mTOR related signaling molecules
Ontology highlight
ABSTRACT: To determine protein concentration in cells, we performed spike-in DIA experiments.
Isotopically labeled concatemers (for mTOR-related signaling proteins) were spiked into lysates from p18Rev cells (each 20 mg) with four three-fold serial dilutions from 5,000 fmol. The lysates were subjected to digestion with trypsin. For absolute quantification of proteins, the digests containing isotopically labeled recombinant proteins were separated on a column (EV1106, Evosep) using a pre-programmed gradient (15 samples per day) at a flow rate of 200 nL/min using the Evosep One system (Evosep).
Project description:Hypertranscription facilitates biosynthetically demanding cellular state transitions through global upregulation of the nascent transcriptome. Despite its potential widespread relevance, documented examples of hypertranscription remain few and limited predominantly to early development. This limitation is in large part due to the fact that modern sequencing approaches, including single-cell RNA sequencing (scRNA-seq), generally assume similar levels of transcriptional output per cell. Here, we use molecule counting and spike-in normalization to develop absolute scaling of single-cell RNA sequencing data. Absolute scaling enables an estimation of total transcript abundances per cell, which we validate in embryonic stem cell (ESC) and germline data and apply to adult mouse organs at steady-state or during regeneration.
Project description:MicroRNAs (miRNAs) have been shown to play an important role in many different cellular, developmental, and physiological processes. Accordingly, numerous methods have been established to identify and quantify miRNAs. The shortness of miRNA sequence results in a high dynamic range of melting temperatures and, moreover, impedes a proper selection of detection probes or optimized PCR primers. While miRNA microarrays allow for massive parallel and accurate relative measurement of all known miRNAs, they have so far been less useful as an assay for absolute quantification. Here, we present a microarray based approach for global and absolute quantification of miRNAs. The method relies on an equimolar pool of about 1000 synthetic miRNAs of known concentration which is used as an universal reference and labeled and hybridized in a dual colour approach on the same array as the sample of interest. Each single miRNA is quantified with respect to the universal reference outbalancing bias related to sequence, labeling, hybridization or signal detection method. We demonstrate the accuracy of the method by various spike in experiments. Further, we quantified miRNA copy numbers in liver samples and CD34(+)CD133(-) hematopoietic stem cells.
Project description:We developed a method to estimate the 3D interaction probabilities of chromatin loops across the genome on an absolute scale from Micro-C maps. To calibrate the method, we performed Micro-C on two engineered mouse embryonic stem cell (mESC) lines, each containing a fluorescently labeled chromatin loop that was quantified in previous live imaging studies. One loop is an endogenous loop containing the Fbn2 gene, and the other is a synthetic loop near the Npr3 gene. We performed two replicates of Micro-C per cell line. Using our absolute quantification method, we find that loops generally form with low probabilities. We also provide an ultra-deep merged Micro-C map for mESCs that combines all existing mESC Micro-C datasets to date, containing a total of 15.6 billion unique interactions.
Project description:MicroRNAs (miRNAs) have been shown to play an important role in many different cellular, developmental, and physiological processes. Accordingly, numerous methods have been established to identify and quantify miRNAs. The shortness of miRNA sequence results in a high dynamic range of melting temperatures and, moreover, impedes a proper selection of detection probes or optimized PCR primers. While miRNA microarrays allow for massive parallel and accurate relative measurement of all known miRNAs, they have so far been less useful as an assay for absolute quantification. Here, we present a microarray based approach for global and absolute quantification of miRNAs. The method relies on an equimolar pool of about 1000 synthetic miRNAs of known concentration which is used as an universal reference and labeled and hybridized in a dual colour approach on the same array as the sample of interest. Each single miRNA is quantified with respect to the universal reference outbalancing bias related to sequence, labeling, hybridization or signal detection method. We demonstrate the accuracy of the method by various spike in experiments. Further, we quantified miRNA copy numbers in liver samples and CD34(+)CD133(-) hematopoietic stem cells.
Project description:Normalization of high-throughput small RNA sequencing (sRNA-Seq) data is required to compare sRNA levels across different samples. Commonly used relative normalization approaches can cause erroneous conclusions due to fluctuating small RNA populations between tissues. We developed a set of sRNA spike-in oligonucleotides (sRNA spike-ins) that enable absolute normalization of sRNA-Seq data across independent experiments, as well as the genome-wide estimation of sRNA:mRNA stoichiometries when used together with mRNA spike-in oligonucleotides.
Project description:MicroRNAs (miRNAs) have been shown to play an important role in many different cellular, developmental, and physiological processes. Accordingly, numerous methods have been established to identify and quantify miRNAs. The shortness of miRNA sequence results in a high dynamic range of melting temperatures and, moreover, impedes a proper selection of detection probes or optimized PCR primers. While miRNA microarrays allow for massive parallel and accurate relative measurement of all known miRNAs, they have so far been less useful as an assay for absolute quantification. Here, we present a microarray based approach for global and absolute quantification of miRNAs. The method relies on an equimolar pool of about 1000 synthetic miRNAs of known concentration which is used as an universal reference and labeled and hybridized in a dual colour approach on the same array as the sample of interest. Each single miRNA is quantified with respect to the universal reference outbalancing bias related to sequence, labeling, hybridization or signal detection method. We demonstrate the accuracy of the method by various spike in experiments. Further, we quantified miRNA copy numbers in liver samples and CD34(+)CD133(-) hematopoietic stem cells. Total liver RNA was mixed with 2.5 fmol of each of 18 RNA oligonucleotides reverse complement to miRControl 3 probes and subsequently fluorescently labelled by 3â ligation. Total RNA mix was hybridized in a dual colour approach to microarrays versus a second labelled synthetic miRNA pool (n = 6). The synthetic miRNA pool consisted of 2.5 fmol of each of 891 non redundant miRNAs sequences and miRControl 3 sequences. The array data was normalized by calculating the median of the miRControl 3 present in the liver and UR sample. The miRNA amount was calculated with respect to the corresponding miRNA in the UR.
Project description:Absolute targeted proteomics typically employs known amounts of synthetic stable isotopically labeled peptides which are mixed with the analyte and analysed by LC-MS. In order to obtain accurate data, we evaluated the use of two different stable isotopes of the same peptide as spike-in for absolute quantification. For this purpose, peptide labeling by reductive amination was applied, which is a mild reaction for dimethylation of amine groups with very high yield and very little side reactions. Furthermore, three different forms can be generated with e.g., light and heavy labels for spike-in peptides, and medium label for endogenous peptides. The addition of the dimethylated proteotypic peptide in two different versions allows to determine the accuracy of the quantification of endogenous peptides using the relative ratio of the intensities of the two internal standards. The method was studied with peptides of apolipoprotein A-I, apolipoprotein B-100, and leucine-rich alpha-2-glycoprotein without and with serum. In serum, the endogenous protein concentrations were accurately measured across four orders of magnitude by the two-point quantitation method. Less than 20% of coefficient of variation (CV) values and strong correlation with R2 of 0.99 across three analytical replicates was observed. The results showed that the accuracy to determine the amount of endogenous peptides can be validated using two references against each other, which cannot be obtained by one-point quantitation. Because of the significant lower costs than synthetic stable isotopically labeled peptides, this approach might be particularly interesting for the absolute quantitation of multiple proteins.
Project description:To determine the absolute copy number of proteins in MDA-MB231 breast cancer cells, we employed IBAQ mediated absolute quantification of proteins based on (Schwanhäusser et al., Nature, 2011), with some modifications. Maqquant calculated iBAQ values were calibrated using spike-in standards, and used to calculate copy numbers for each identified protein within the dataset. Copy numbers for a total of 3,584 proteins were calculated in MDA-MB231 cells.