| 1. |
- Lönn, Peter, et al.
(författare)
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High-throughput in situ mapping of phosphorylated protein complexes across the cell cycle and in response to drugs
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Interactions and posttranslational modifications (PTMs) of proteins orchestrate cellular responses to cytokines, drugs or other agents, but it has been difficult to monitor and characterize these dynamic events at high-throughput. Here, we have established a semi-automated system for large-scale in situ proximity ligation assays (isPLA). The protocol combines isPLA in microtiter wells with automated microscopy and computer-based image analysis whereby specific protein phosphorylations and interactions are digitally recorded in cells, along with measurements of morphological features. We demonstrate how this platform can improve analysis of cellular signaling by investigating TGF-b responsive Smad2 linker phosphorylations and complex formations over time and across millions of individual cells. We depict single cell responses in relation to e.g. local cell crowding and cell cycle progression via measurements of DNA content and nuclear size. Finally, we illustrate the application of the protocol for demonstrating drug effects by screening a library of phosphatase inhibitors. In summary, our approach expands the scope for image-based single cell analyses by combining observations of protein interactions and modifications with morphological details of individual cells at high throughput.
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| 2. |
- Lönn, Peter, et al.
(författare)
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Image-based high-throughput mapping of TGF-beta-induced phosphocomplexes at a single-cell level
- 2021
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Ingår i: Communications Biology. - : Springer Nature. - 2399-3642. ; 4
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Tidskriftsartikel (refereegranskat)abstract
- To improve our ability to monitor cellular responses to e.g. cytokines or drugs, Lonn et al have developed a semi-automated system for large-scale in situ proximity ligation assays (isPLA) in HaCAT keratinocyte cells. Their approach expands the scope for image-based single cell analyses by combining observations of protein interactions and modifications with morphological details of individual cells at high throughput. Protein interactions and posttranslational modifications orchestrate cellular responses to e.g. cytokines and drugs, but it has been difficult to monitor these dynamic events in high-throughput. Here, we describe a semi-automated system for large-scale in situ proximity ligation assays (isPLA), combining isPLA in microtiter wells with automated microscopy and computer-based image analysis. Phosphorylations and interactions are digitally recorded along with subcellular morphological features. We investigated TGF-beta-responsive Smad2 linker phosphorylations and complex formations over time and across millions of individual cells, and we relate these events to cell cycle progression and local cell crowding via measurements of DNA content and nuclear size of individual cells, and of their relative positions. We illustrate the suitability of this protocol to screen for drug effects using phosphatase inhibitors. Our approach expands the scope for image-based single cell analyses by combining observations of protein interactions and modifications with morphological details of individual cells at high throughput.
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| 3. |
- Björkesten, Johan, et al.
(författare)
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A multiplex platform for digital measurement of circular DNA reaction products
- 2020
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Ingår i: Nucleic Acids Research. - : OXFORD UNIV PRESS. - 0305-1048 .- 1362-4962. ; 48:13
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Tidskriftsartikel (refereegranskat)abstract
- Digital PCR provides high sensitivity and unprecedented accuracy in DNA quantification, but current approaches require dedicated instrumentation and have limited opportunities for multiplexing. Here, we present an isothermal platform for digital enumeration of DNA reaction products in multiplex via standard fluorescence microscopy. Circular DNA strands, which may result from a wide range of molecular detection reactions, are captured on streptavidin-coated surfaces via hybridized biotinylated primers, followed by rolling circle amplification (RCA). The addition of 15% polyethylene glycol 4000 during RCA resulted in uniform, easily recorded reaction products. Immobilized DNA circles were visualized as RCA products with 100% efficiency, as determined by droplet digital PCR. We confirmed previous reports about the influence on RCA by sequence composition and size of RCA templates, and we developed an efficient one-step restaining procedure for sequential multiplexing using toehold-triggered DNA strand displacement. Finally, we exemplify applications of this digital readout platform by demonstrating more than three orders of magnitude improved sensitivity by digital measurement of prostate specific antigen (PSA) (detection threshold similar to 100 pg/l), compared to a commercial enzyme-linked immunosorbent assay (ELISA) with analogue readout (detection threshold similar to 500 ng/l), using the same antibody pair.
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| 4. |
- Björkesten, Johan, 1988-
(författare)
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Dried blood sampling and digital readout to advance molecular diagnostics
- 2019
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- A drastically increased capacity to measure large sets of molecular features in numerous patient samples in great detail will be required to fulfill the vision of precision medicine and wellness, which may characterize molecular diagnostics in the 21st century. Also sampling procedures need a renaissance to permit continuous sampling at population levels at reasonable cost.Blood sampling is typically performed via venipuncture to draw several milliliters of blood for plasma isolation. This is inconvenient, time-consuming and costly, as well as hard to standardize. The effect on plasma protein profiles by pre-centrifugation delay was investigated in Paper II, demonstrating time- and temperature-dependent release of proteins from blood cells upon delayed plasma isolation, but almost no protein degradation as analyzed by two 92-plex protein panels (Olink® Proteomics). An alternative sampling method, where blood drops from a finger stick are collected dried on paper, is relatively non-invasive, potentially home-based and cheap. Dried blood spots can also be shipped via regular mail and compactly stored. The effect of drying and long term storage stability of a large set of proteins from dried blood spots was investigated in Paper I using Olink® technology. The main findings were that drying slightly but consistently influenced the recorded levels of blood proteins, and that long-term storage decreased the detected levels of some of the proteins with half-lives of decades.Some molecular diagnostic investigations require great accuracy to be useful, arguing for digital enumeration of individual molecules. Digital PCR is the gold standard but Paper III presents an alternative approach based on rolling circle amplification of single molecules. Another instance where extreme assay performance is required is for rare mutation detection from liquid biopsies. Paper V presents a new method offering essentially error-free genotyping of individual molecules by majority-vote decisions for counting rare mutant DNA in blood. Yet other diagnostic investigations require very simple assays. Paper IV presents a novel one-step method to detect nucleic acid sequences by combining the power of rolling circle amplification and the specificity of DNA strand displacement in a format simple enough to be used at the point of care. Altogether, the thesis spans technologies for advanced molecular diagnostics, from sample collection over assay techniques to an improved readout.
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| 5. |
- Björkesten, Johan, et al.
(författare)
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Multiplex digital enumeration of circular DNA molecules on solid supports
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Digital PCR is a detection method with unprecedented accuracy for DNA quantification, but with some limitations in the form of complexity of instrumentation and limited multiplexing. Here we present an isothermal platform for digital enumeration of DNA reaction products in multiplex via standard fluorescence microscopy, to overcome limitations of digital PCR. In this method, sets of small DNA circles, resulting from detection reactions, are captured on a streptavidin-coated surface and subjected to rolling circle amplification (RCA). We found that the addition of 15% polyethylene glycol 4000 to RCA on planar surfaces ensured uniform, easily counted signals, each of which represents an individual reaction product. The DNA circles were immobilized and detected with efficiencies of 50 and 100%, respectively, as determined by droplet digital PCR. We confirmed previous reports about the effect on RCA efficiency by sequence composition and size of the RCA templates at the level of individual amplified molecules, and we developed an efficient one-step de- and re-staining procedure for sequential multiplexing via toehold-triggered DNA strand displacement.
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| 6. |
- Björkesten, Johan, et al.
(författare)
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Rolling circle amplification reporters – a general tool to simplify molecular detections
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Methods to detect biomolecules via rolling circle amplification (RCA), for example padlock probes and proximity ligation assay (PLA) tend to be complex and include several reaction steps. Herein, we evaluated a new tool for the toolbox of RCA-based detection methods - RCA Reporters. Briefly, RCA Reporters represent inert DNA structures that, upon contact with a specific nucleic acid sequence, unravel via a highly specific strand displacement process to initiate local enzyme-assisted RCA reactions. The RCA Reporters can be used to directly detect ssDNA or RNA in a sample, or proteins via oligonucleotide-conjugated antibodies. The reagents can also enable faster RCA reactions or extremely selective genotyping of RCA products with repeated copies of a target sequence through a majority-vote mechanism. Further amplification of ongoing RCA reactions via RCA Reporters can allow efficient digital enumeration of single molecules via flow cytometry, with potential for simple and highly accurate molecular counting assays. The intrinsic simplicity of RCA Reporter also renders them attractive for applications at the point of care.
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| 7. |
- Björkesten, Johan, et al.
(författare)
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Stability of Proteins in Dried Blood Spot Biobanks.
- 2017
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Ingår i: Molecular & Cellular Proteomics. - 1535-9476 .- 1535-9484. ; 16:7, s. 1286-1296
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Tidskriftsartikel (refereegranskat)abstract
- An important motivation for the construction of biobanks is to discover biomarkers that identify diseases at early, potentially curable stages. This will require biobanks from large numbers of individuals, preferably sampled repeatedly, where the samples are collected and stored under conditions that preserve potential biomarkers. Dried blood samples are attractive for biobanking because of the ease and low cost of collection and storage. Here we have investigated their suitability for protein measurements. 92 proteins with relevance for oncology were analyzed using multiplex proximity extension assays (PEA) in dried blood spots collected on paper and stored for up to 30 years at either +4°C or -24°C. Our main findings were that 1) the act of drying only slightly influenced detection of blood proteins (average correlation of 0.970), and in a reproducible manner (correlation of 0.999), 2) detection of some proteins was not significantly affected by storage over the full range of three decades (34% and 76% of the analyzed proteins at +4°C and -24°C, respectively), while levels of others decreased slowly during storage with half-lives in the range of 10 to 50 years, and 3) detectability of proteins was less affected in dried samples stored at -24°C compared to at +4°C, as the median protein abundance had decreased to 80% and 93% of starting levels after 10 years of storage at +4°C or -24°C, respectively. The results of our study are encouraging as they suggest an inexpensive means to collect large numbers of blood samples, even by the donors themselves, and to transport, and store biobanked samples as spots of whole blood dried on paper. Combined with emerging means to measure hundreds or thousands of protein, such biobanks could prove of great medical value by greatly enhancing discovery as well as routine analysis of blood biomarkers.
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| 8. |
- Chen, Lei, 1985-, et al.
(författare)
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Rare Mutation Detection in Blood Plasma Using sRCA Molecule Counting Probes
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Problems in biology and medicine frequently require the ability to observe, evaluate, andcount even extremely rare macromolecules in biological samples. In particular, rare tumorspecific mutations in plasma provide valuable insights in the course of malignant disease andresponses to therapy, but simpler assay techniques are needed. We describe herein a rapidand exquisitely specific means to recognize and magnify detection signals from individualmolecules to easily recorded levels via a process we call super rolling circle amplification(sRCA). We demonstrate the ability of this technique to enumerate tumor-specific sequencevariants in plasma from cancer patients via flow cytometry at very high efficiency, with specificityadequate to detect single nucleotide mutant sequences among 100,000 copies of thenormal sequence in a 3 hr protocol. And the mutation analysis data generated from patientctDNA samples with our sRCA method are in high accordance with the patients’ primary tumorsequencing data.
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| 9. |
- Landegren, Ulf, et al.
(författare)
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A myopic perspective on the future of protein diagnostics
- 2018
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Ingår i: New Biotechnology. - : ELSEVIER SCIENCE BV. - 1871-6784 .- 1876-4347. ; 45, s. 14-18
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Forskningsöversikt (refereegranskat)abstract
- Plasma proteome analyses of the future promise invaluable insights into states of health, not only by measuring proteins whose role it is to ensure blood homeostasis, but increasingly also as a window into the health of practically any tissue in the body via so-called leakage protein biomarkers. Realizing more of this vast potential will require progress along many lines. Here we discuss the main ones, such as optimal selection of target proteins, affinity reagents, immunoassay formats, samples, and applications, with a view from ongoing work in our laboratory.
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| 10. |
- Shen, Qiujin, et al.
(författare)
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Strong impact on plasma protein profiles by precentrifugation delay but not by repeated freeze-thaw cycles, as analyzed using multiplex proximity extension assays
- 2018
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Ingår i: Clinical Chemistry and Laboratory Medicine. - : WALTER DE GRUYTER GMBH. - 1434-6621 .- 1437-4331. ; 56:4, s. 582-594
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Tidskriftsartikel (refereegranskat)abstract
- Background: A number of factors regarding blood collection, handling and storage may affect sample quality. The purpose of this study was to assess the impact on plasma protein profiles by delayed centrifugation and plasma separation and multiple freeze-thaw cycles.Methods: Blood samples drawn from 16 healthy individuals were collected into ethylenediaminetetraacetic acid tubes and kept either at 4 degrees C or 22 degrees C for 1-36 h prior to centrifugation. Plasma samples prepared 1 h after venipuncture were also subjected to two to eight cycles of freezing at -80 degrees C and thawing at 22 degrees C. Multiplex proximity extension assay, an antibody-based protein assay, was used to investigate the influence on plasma proteins.Results: Up to 36 h delay before blood centrifugation resulted in significant increases of 16 and 40 out of 139 detectable proteins in samples kept at 4 degrees C or 22 degrees C, respectively. Some increases became noticeable after 8 h delay at 4 degrees C but already after 1 h at 22 degrees C. For samples stored at 4 degrees C, epidermal growth factor (EGF), NF-kappa-B essential modulator, SRC, interleukin 16 and CD6 increased the most, whereas the five most significantly increased proteins after storage at 22 degrees C were CD40 antigen ligand (CD40-L), EGF, platelet-derived growth factor subunit B, C-X-C motif chemokine ligand 5 and matrix metallopeptidase 1 (MMP1). Only matrix metallopeptidase 7 (MMP7) decreased significantly over time and only after storage at 22 degrees C. No protein levels were found to be significantly affected by up to eight freeze-thaw cycles.Conclusions: Plasma should be prepared from blood after a limited precentrifugation delay at a refrigerated temperature. By contrast, the influence by several freeze-thaw cycles on detectable protein levels in plasma was negligible.
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| 11. |
- Siart, Benjamin, et al.
(författare)
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Measurements ofinflammation protein biomarkers in venous plasma, earlobe capillary plasma andin capillary plasma stored on filter paper
- 2017
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Ingår i: Cytokine. - 1043-4666 .- 1096-0023.
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Multiplex panels for protein biomarkers are increasingly used to analyze blood samples in various fields of clinical research. However, they are rarely used in studies performed outside of a clinical setting. This may in part be due to the relative invasiveness of drawing blood from the vein and because of problems associated with the separation and transport of plasma. Samples collected from the earlobe would be less invasive and could be collected more conveniently. Transportation and storage of such samples could be made easier by blotting plasma on filter paper as dried plasma spots (DPS). The objective of this study was to compare values of multiple protein biomarkers for inflammation measured from three different sources (1) venous plasma, (2) plasma derived from capillary blood from the earlobe and (3) from capillary plasma stored as DPS. Samples from twelve male individuals were assessed with a panel of 92 inflammation related proteins using multiplex proximity extension assay technology. Correlations between the three sample types varied greatly between analytes. In general, a high correlation was observed between capillary plasma and DPS, with 33 analytes showing a correlation value of ρ > 0.8 in the two sample types. At this level of correlation (ρ > 0.8) 14 analytes correlated between venous and capillary plasma in contrast to only six analytes in the comparison of venous blood with DPS. We conclude that collecting samples from the earlobe is a feasible and less invasive alternative to venipuncture, but that the comparability with measures obtained from venous samples varies greatly between proteins.
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| 12. |
- Siart, Benjamin, et al.
(författare)
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Protein measurements in venous plasma, earlobe capillary plasma and in plasma stored on filter paper
- 2019
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Ingår i: Analytical Biochemistry. - : ACADEMIC PRESS INC ELSEVIER SCIENCE. - 0003-2697 .- 1096-0309. ; 566, s. 146-150
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Tidskriftsartikel (refereegranskat)abstract
- In this study, levels of inflammatory protein biomarkers in venous plasma, plasma derived from capillary blood from the earlobe, and capillary plasma stored as dried plasma spots (DPS) were compared. Samples from 12 male individuals were assessed with a panel of 92 inflammation-related proteins using multiplex proximity extension assay. Correlations between sample types varied greatly between analytes. A high correlation of rho > 0.8 was observed between capillary plasma and DPS for 32 analytes. At this level of correlation, 13 analytes correlated between venous and capillary plasma and 5 analytes in the comparison of venous blood with DPS.
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