41 results on '"Lun ATL"'
Search Results
2. Genome-wide analysis reveals no evidence of trans chromosomal regulation of mammalian immune development
- Author
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Barsh, GS, Johanson, TM, Coughlan, HD, Lun, ATL, Bediaga, NG, Naselli, G, Garnham, AL, Harrison, LC, Smyth, GK, Allan, RS, Barsh, GS, Johanson, TM, Coughlan, HD, Lun, ATL, Bediaga, NG, Naselli, G, Garnham, AL, Harrison, LC, Smyth, GK, and Allan, RS
- Abstract
It has been proposed that interactions between mammalian chromosomes, or transchromosomal interactions (also known as kissing chromosomes), regulate gene expression and cell fate determination. Here we aimed to identify novel transchromosomal interactions in immune cells by high-resolution genome-wide chromosome conformation capture. Although we readily identified stable interactions in cis, and also between centromeres and telomeres on different chromosomes, surprisingly we identified no gene regulatory transchromosomal interactions in either mouse or human cells, including previously described interactions. We suggest that advances in the chromosome conformation capture technique and the unbiased nature of this approach allow more reliable capture of interactions between chromosomes than previous methods. Overall our findings suggest that stable transchromosomal interactions that regulate gene expression are not present in mammalian immune cells and that lineage identity is governed by cis, not trans chromosomal interactions.
- Published
- 2018
3. Overcoming confounding plate effects in differential expression analyses of single-cell RNA-seq data
- Author
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Lun, ATL, Marioni, JC, Lun, Aaron [0000-0002-3564-4813], Marioni, John [0000-0001-9092-0852], and Apollo - University of Cambridge Repository
- Subjects
summation ,plate effects ,differential expression ,single-cell RNA sequencing - Abstract
An increasing number of studies are using single-cell RNA-sequencing (scRNA-seq) to characterize the gene expression profiles of individual cells. One common analysis applied to scRNA-seq data involves detecting differentially expressed (DE) genes between cells in different biological groups. However, many experiments are designed such that the cells to be compared are processed in separate plates or chips, meaning that the groupings are confounded with systematic plate effects. This confounding aspect is frequently ignored in DE analyses of scRNA-seq data. In this article, we demonstrate that failing to consider plate effects in the statistical model results in loss of type I error control. A solution is proposed whereby counts are summed from all cells in each plate and the count sums for all plates are used in the DE analysis. This restores type I error control in the presence of plate effects without compromising detection power in simulated data. Summation is also robust to varying numbers and library sizes of cells on each plate. Similar results are observed in DE analyses of real data where the use of count sums instead of single-cell counts improves specificity and the ranking of relevant genes. This suggests that summation can assist in maintaining statistical rigour in DE analyses of scRNA-seq data with plate effects.
- Published
- 2017
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- View/download PDF
4. A non-canonical function of Ezh2 preserves immune homeostasis
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Vasanthakumar, A, Xu, D, Lun, ATL, Kueh, AJ, van Gisbergen, KPJM, Iannarella, N, Li, X, Yu, L, Wang, D, Williams, BRG, Lee, SCW, Majewski, IJ, Godfrey, DI, Smyth, GK, Alexander, WS, Herold, MJ, Kallies, A, Nutt, SL, Allan, RS, Vasanthakumar, A, Xu, D, Lun, ATL, Kueh, AJ, van Gisbergen, KPJM, Iannarella, N, Li, X, Yu, L, Wang, D, Williams, BRG, Lee, SCW, Majewski, IJ, Godfrey, DI, Smyth, GK, Alexander, WS, Herold, MJ, Kallies, A, Nutt, SL, and Allan, RS
- Abstract
Enhancer of zeste 2 (Ezh2) mainly methylates lysine 27 of histone-H3 (H3K27me3) as part of the polycomb repressive complex 2 (PRC2) together with Suz12 and Eed. However, Ezh2 can also modify non-histone substrates, although it is unclear whether this mechanism has a role during development. Here, we present evidence for a chromatin-independent role of Ezh2 during T-cell development and immune homeostasis. T-cell-specific depletion of Ezh2 induces a pronounced expansion of natural killer T (NKT) cells, although Ezh2-deficient T cells maintain normal levels of H3K27me3. In contrast, removal of Suz12 or Eed destabilizes canonical PRC2 function and ablates NKT cell development completely. We further show that Ezh2 directly methylates the NKT cell lineage defining transcription factor PLZF, leading to its ubiquitination and subsequent degradation. Sustained PLZF expression in Ezh2-deficient mice is associated with the expansion of a subset of NKT cells that cause immune perturbation. Taken together, we have identified a chromatin-independent function of Ezh2 that impacts on the development of the immune system.
- Published
- 2017
5. Scater: pre-processing, quality control, normalization and visualization of single-cell RNA-seq data in R
- Author
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Hofacker, I, McCarthy, DJ, Campbell, KR, Lun, ATL, Wills, QF, Hofacker, I, McCarthy, DJ, Campbell, KR, Lun, ATL, and Wills, QF
- Abstract
MOTIVATION: Single-cell RNA sequencing (scRNA-seq) is increasingly used to study gene expression at the level of individual cells. However, preparing raw sequence data for further analysis is not a straightforward process. Biases, artifacts and other sources of unwanted variation are present in the data, requiring substantial time and effort to be spent on pre-processing, quality control (QC) and normalization. RESULTS: We have developed the R/Bioconductor package scater to facilitate rigorous pre-processing, quality control, normalization and visualization of scRNA-seq data. The package provides a convenient, flexible workflow to process raw sequencing reads into a high-quality expression dataset ready for downstream analysis. scater provides a rich suite of plotting tools for single-cell data and a flexible data structure that is compatible with existing tools and can be used as infrastructure for future software development. AVAILABILITY AND IMPLEMENTATION: The open-source code, along with installation instructions, vignettes and case studies, is available through Bioconductor at http://bioconductor.org/packages/scater . CONTACT: davis@ebi.ac.uk. SUPPLEMENTARY INFORMATION: Supplementary data are available at Bioinformatics online.
- Published
- 2017
6. A step-by-step workflow for low-level analysis of single-cell RNA-seq data with Bioconductor.
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Lun, ATL, McCarthy, DJ, Marioni, JC, Lun, ATL, McCarthy, DJ, and Marioni, JC
- Abstract
Single-cell RNA sequencing (scRNA-seq) is widely used to profile the transcriptome of individual cells. This provides biological resolution that cannot be matched by bulk RNA sequencing, at the cost of increased technical noise and data complexity. The differences between scRNA-seq and bulk RNA-seq data mean that the analysis of the former cannot be performed by recycling bioinformatics pipelines for the latter. Rather, dedicated single-cell methods are required at various steps to exploit the cellular resolution while accounting for technical noise. This article describes a computational workflow for low-level analyses of scRNA-seq data, based primarily on software packages from the open-source Bioconductor project. It covers basic steps including quality control, data exploration and normalization, as well as more complex procedures such as cell cycle phase assignment, identification of highly variable and correlated genes, clustering into subpopulations and marker gene detection. Analyses were demonstrated on gene-level count data from several publicly available datasets involving haematopoietic stem cells, brain-derived cells, T-helper cells and mouse embryonic stem cells. This will provide a range of usage scenarios from which readers can construct their own analysis pipelines.
- Published
- 2016
7. csaw: a Bioconductor package for differential binding analysis of ChIP-seq data using sliding windows
- Author
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Lun, ATL, Smyth, GK, Lun, ATL, and Smyth, GK
- Abstract
Chromatin immunoprecipitation with massively parallel sequencing (ChIP-seq) is widely used to identify binding sites for a target protein in the genome. An important scientific application is to identify changes in protein binding between different treatment conditions, i.e. to detect differential binding. This can reveal potential mechanisms through which changes in binding may contribute to the treatment effect. The csaw package provides a framework for the de novo detection of differentially bound genomic regions. It uses a window-based strategy to summarize read counts across the genome. It exploits existing statistical software to test for significant differences in each window. Finally, it clusters windows into regions for output and controls the false discovery rate properly over all detected regions. The csaw package can handle arbitrarily complex experimental designs involving biological replicates. It can be applied to both transcription factor and histone mark datasets, and, more generally, to any type of sequencing data measuring genomic coverage. csaw performs favorably against existing methods for de novo DB analyses on both simulated and real data. csaw is implemented as a R software package and is freely available from the open-source Bioconductor project.
- Published
- 2016
8. From reads to genes to pathways: differential expression analysis of RNA-Seq experiments using Rsubread and the edgeR quasi-likelihood pipeline.
- Author
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Chen, Y, Lun, ATL, Smyth, GK, Chen, Y, Lun, ATL, and Smyth, GK
- Abstract
In recent years, RNA sequencing (RNA-seq) has become a very widely used technology for profiling gene expression. One of the most common aims of RNA-seq profiling is to identify genes or molecular pathways that are differentially expressed (DE) between two or more biological conditions. This article demonstrates a computational workflow for the detection of DE genes and pathways from RNA-seq data by providing a complete analysis of an RNA-seq experiment profiling epithelial cell subsets in the mouse mammary gland. The workflow uses R software packages from the open-source Bioconductor project and covers all steps of the analysis pipeline, including alignment of read sequences, data exploration, differential expression analysis, visualization and pathway analysis. Read alignment and count quantification is conducted using the Rsubread package and the statistical analyses are performed using the edgeR package. The differential expression analysis uses the quasi-likelihood functionality of edgeR.
- Published
- 2016
9. From reads to regions: a Bioconductor workflow to detect differential binding in ChIP-seq data.
- Author
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Lun, ATL, Smyth, GK, Lun, ATL, and Smyth, GK
- Abstract
Chromatin immunoprecipitation with massively parallel sequencing (ChIP-seq) is widely used to identify the genomic binding sites for protein of interest. Most conventional approaches to ChIP-seq data analysis involve the detection of the absolute presence (or absence) of a binding site. However, an alternative strategy is to identify changes in the binding intensity between two biological conditions, i.e., differential binding (DB). This may yield more relevant results than conventional analyses, as changes in binding can be associated with the biological difference being investigated. The aim of this article is to facilitate the implementation of DB analyses, by comprehensively describing a computational workflow for the detection of DB regions from ChIP-seq data. The workflow is based primarily on R software packages from the open-source Bioconductor project and covers all steps of the analysis pipeline, from alignment of read sequences to interpretation and visualization of putative DB regions. In particular, detection of DB regions will be conducted using the counts for sliding windows from the csaw package, with statistical modelling performed using methods in the edgeR package. Analyses will be demonstrated on real histone mark and transcription factor data sets. This will provide readers with practical usage examples that can be applied in their own studies.
- Published
- 2015
10. diffHic: a Bioconductor package to detect differential genomic interactions in Hi-C data
- Author
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Lun, ATL, Smyth, GK, Lun, ATL, and Smyth, GK
- Abstract
BACKGROUND: Chromatin conformation capture with high-throughput sequencing (Hi-C) is a technique that measures the in vivo intensity of interactions between all pairs of loci in the genome. Most conventional analyses of Hi-C data focus on the detection of statistically significant interactions. However, an alternative strategy involves identifying significant changes in the interaction intensity (i.e., differential interactions) between two or more biological conditions. This is more statistically rigorous and may provide more biologically relevant results. RESULTS: Here, we present the diffHic software package for the detection of differential interactions from Hi-C data. diffHic provides methods for read pair alignment and processing, counting into bin pairs, filtering out low-abundance events and normalization of trended or CNV-driven biases. It uses the statistical framework of the edgeR package to model biological variability and to test for significant differences between conditions. Several options for the visualization of results are also included. The use of diffHic is demonstrated with real Hi-C data sets. Performance against existing methods is also evaluated with simulated data. CONCLUSIONS: On real data, diffHic is able to successfully detect interactions with significant differences in intensity between biological conditions. It also compares favourably to existing software tools on simulated data sets. These results suggest that diffHic is a viable approach for differential analyses of Hi-C data.
- Published
- 2015
11. Repression of Igf1 expression by Ezh2 prevents basal cell differentiation in the developing lung
- Author
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Galvis, LA, Holik, AZ, Short, KM, Pasquet, J, Lun, ATL, Blewitt, ME, Smyth, IM, Ritchie, ME, Asselin-Labat, M-L, Galvis, LA, Holik, AZ, Short, KM, Pasquet, J, Lun, ATL, Blewitt, ME, Smyth, IM, Ritchie, ME, and Asselin-Labat, M-L
- Abstract
Epigenetic mechanisms involved in the establishment of lung epithelial cell lineage identities during development are largely unknown. Here, we explored the role of the histone methyltransferase Ezh2 during lung lineage determination. Loss of Ezh2 in the lung epithelium leads to defective lung formation and perinatal mortality. We show that Ezh2 is crucial for airway lineage specification and alveolarization. Using optical projection tomography imaging, we found that branching morphogenesis is affected in Ezh2 conditional knockout mice and the remaining bronchioles are abnormal, lacking terminally differentiated secretory club cells. Remarkably, RNA-seq analysis revealed the upregulation of basal genes in Ezh2-deficient epithelium. Three-dimensional imaging for keratin 5 further showed the unexpected presence of a layer of basal cells from the proximal airways to the distal bronchioles in E16.5 embryos. ChIP-seq analysis indicated the presence of Ezh2-mediated repressive marks on the genomic loci of some but not all basal genes, suggesting an indirect mechanism of action of Ezh2. We found that loss of Ezh2 de-represses insulin-like growth factor 1 (Igf1) expression and that modulation of IGF1 signaling ex vivo in wild-type lungs could induce basal cell differentiation. Altogether, our work reveals an unexpected role for Ezh2 in controlling basal cell fate determination in the embryonic lung endoderm, mediated in part by repression of Igf1 expression.
- Published
- 2015
12. Transcriptome and H3K27 tri-methylation profiling of Ezh2-deficient lung epithelium
- Author
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Holik, AZ, Galvis, LA, Lun, ATL, Ritchie, ME, Asselin-Labat, M-L, Holik, AZ, Galvis, LA, Lun, ATL, Ritchie, ME, and Asselin-Labat, M-L
- Abstract
The adaptation of the lungs to air breathing at birth requires the fine orchestration of different processes to control lung morphogenesis and progenitor cell differentiation. However, there is little understanding of the role that epigenetic modifiers play in the control of lung development. We found that the histone methyl transferase Ezh2 plays a critical role in lung lineage specification and survival at birth. We performed a genome-wide transcriptome study combined with a genome-wide analysis of the distribution of H3K27 tri-methylation marks to interrogate the role of Ezh2 in lung epithelial cells. Lung cells isolated from Ezh2-deficient and control mice at embryonic day E16.5 were sorted into epithelial and mesenchymal populations based on EpCAM expression. This enabled us to dissect the transcriptional and epigenetic changes induced by the loss of Ezh2 specifically in the lung epithelium. Here we provide a detailed description of the analysis of the RNA-seq and ChIP-seq data, including quality control, read mapping, differential expression and differential binding analyses, as well as visualisation methods used to present the data. These data can be accessed from the Gene Expression Omnibus database (super-series accession number GSE57393).
- Published
- 2015
13. De novo detection of differentially bound regions for ChIP-seq data using peaks and windows: controlling error rates correctly
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Lun, ATL, Smyth, GK, Lun, ATL, and Smyth, GK
- Abstract
A common aim in ChIP-seq experiments is to identify changes in protein binding patterns between conditions, i.e. differential binding. A number of peak- and window-based strategies have been developed to detect differential binding when the regions of interest are not known in advance. However, careful consideration of error control is needed when applying these methods. Peak-based approaches use the same data set to define peaks and to detect differential binding. Done improperly, this can result in loss of type I error control. For window-based methods, controlling the false discovery rate over all detected windows does not guarantee control across all detected regions. Misinterpreting the former as the latter can result in unexpected liberalness. Here, several solutions are presented to maintain error control for these de novo counting strategies. For peak-based methods, peak calling should be performed on pooled libraries prior to the statistical analysis. For window-based methods, a hybrid approach using Simes' method is proposed to maintain control of the false discovery rate across regions. More generally, the relative advantages of peak- and window-based strategies are explored using a range of simulated and real data sets. Implementations of both strategies also compare favourably to existing programs for differential binding analyses.
- Published
- 2014
14. edgeR v4: powerful differential analysis of sequencing data with expanded functionality and improved support for small counts and larger datasets.
- Author
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Chen Y, Chen L, Lun ATL, Baldoni PL, and Smyth GK
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- Bayes Theorem, Humans, High-Throughput Nucleotide Sequencing methods, Gene Expression Profiling methods, DNA Methylation, Sequence Analysis, RNA methods, Software
- Abstract
edgeR is an R/Bioconductor software package for differential analyses of sequencing data in the form of read counts for genes or genomic features. Over the past 15 years, edgeR has been a popular choice for statistical analysis of data from sequencing technologies such as RNA-seq or ChIP-seq. edgeR pioneered the use of the negative binomial distribution to model read count data with replicates and the use of generalized linear models to analyze complex experimental designs. edgeR implements empirical Bayes moderation methods to allow reliable inference when the number of replicates is small. This article announces edgeR version 4, which includes new developments across a range of application areas. Infrastructure improvements include support for fractional counts, implementation of model fitting in C and a new statistical treatment of the quasi-likelihood pipeline that improves accuracy for small counts. The revised package has new functionality for differential methylation analysis, differential transcript expression, differential transcript and exon usage, testing relative to a fold-change threshold and pathway analysis. This article reviews the statistical framework and computational implementation of edgeR, briefly summarizing all the existing features and functionalities but with special attention to new features and those that have not been described previously., (© The Author(s) 2025. Published by Oxford University Press on behalf of Nucleic Acids Research.)
- Published
- 2025
- Full Text
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15. Dyadic interaction of parentification in Chinese families of maternal depression: A qualitative study.
- Author
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Tam ATL and Cheung MC
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- Adolescent, Adult, Female, Humans, Male, Middle Aged, Child of Impaired Parents psychology, East Asian People, Hong Kong, Parent-Child Relations ethnology, Parenting psychology, Parenting ethnology, Qualitative Research, Depressive Disorder, Major ethnology, Depressive Disorder, Major psychology, Parents psychology
- Abstract
This qualitative study explores the lived experiences of parent-child dyads to understand the occurrence of parentification in Chinese families affected by parental depression. Utilizing purposive sampling, families were recruited from community mental health services in Hong Kong, focusing on parents with major depressive disorder and their adolescent children. Data were collected from 14 families through in-depth, semistructured interviews with adolescents (n = 8) and parents (n = 12), as well as dyadic interviews (n = 8), and analyzed utilizing thematic analysis. The central theme, "Complementary Dynamic Interaction: Rippled Relationship," captures the mutual, circular, and reciprocal interactions within parent-adolescent dyads in the context of parental depression. These findings highlight the unique dynamics of parentification in Chinese families affected by parental depression., (© 2024 American Association for Marriage and Family Therapy.)
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- 2025
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16. Systemic inflammatory response syndrome triggered by blood-borne pathogens induces prolonged dendritic cell paralysis and immunosuppression.
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Ashayeripanah M, Vega-Ramos J, Fernandez-Ruiz D, Valikhani S, Lun ATL, White JT, Young LJ, Yaftiyan A, Zhan Y, Wakim L, Caminschi I, Lahoud MH, Lew AM, Shortman K, Smyth GK, Heath WR, Mintern JD, Roquilly A, and Villadangos JA
- Subjects
- Humans, Dendritic Cells, Paralysis, Systemic Inflammatory Response Syndrome, Blood-Borne Pathogens, Immunosuppression Therapy
- Abstract
Blood-borne pathogens can cause systemic inflammatory response syndrome (SIRS) followed by protracted, potentially lethal immunosuppression. The mechanisms responsible for impaired immunity post-SIRS remain unclear. We show that SIRS triggered by pathogen mimics or malaria infection leads to functional paralysis of conventional dendritic cells (cDCs). Paralysis affects several generations of cDCs and impairs immunity for 3-4 weeks. Paralyzed cDCs display distinct transcriptomic and phenotypic signatures and show impaired capacity to capture and present antigens in vivo. They also display altered cytokine production patterns upon stimulation. The paralysis program is not initiated in the bone marrow but during final cDC differentiation in peripheral tissues under the influence of local secondary signals that persist after resolution of SIRS. Vaccination with monoclonal antibodies that target cDC receptors or blockade of transforming growth factor β partially overcomes paralysis and immunosuppression. This work provides insights into the mechanisms of paralysis and describes strategies to restore immunocompetence post-SIRS., Competing Interests: Declaration of interests M.H.L., I.C., and K.S. are listed as inventors on patents relating to Clec9A antibodies., (Copyright © 2024 The Authors. Published by Elsevier Inc. All rights reserved.)
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- 2024
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17. Human Mesenchymal Stem Cell Processing for Clinical Applications Using a Closed Semi-Automated Workflow.
- Author
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Lam ATL, Jayaraman P, Becker A, Lim R, Teo KL, Ng J, and Oh S
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- Humans, Reproducibility of Results, Workflow, Cell Differentiation, Cell Proliferation, Cells, Cultured, Cell Culture Techniques methods, Mesenchymal Stem Cells
- Abstract
Human mesenchymal stem cells (hMSCs) are currently being explored as a promising cell-based therapeutic modality for various diseases, with more market approvals for clinical use expected over the next few years. To facilitate this transition, addressing the bottlenecks of scale, lot-to-lot reproducibility, cost, regulatory compliance, and quality control is critical. These challenges can be addressed by closing the process and adopting automated manufacturing platforms. In this study, we developed a closed and semi-automated process for passaging and harvesting Wharton's jelly (WJ)-derived hMSCs (WJ-hMSCs) from multi-layered flasks using counterflow centrifugation. The WJ-hMSCs were expanded using regulatory compliant serum-free xeno-free (SFM XF) medium, and they showed comparable cell proliferation (population doubling) and morphology to WJ-hMSCs expanded in classic serum-containing media. Our closed semi-automated harvesting protocol demonstrated high cell recovery (~98%) and viability (~99%). The cells washed and concentrated using counterflow centrifugation maintained WJ-hMSC surface marker expression, colony-forming units (CFU-F), trilineage differentiation potential, and cytokine secretion profiles. The semi-automated cell harvesting protocol developed in the study can be easily applied for the small- to medium-scale processing of various adherent and suspension cells by directly connecting to different cell expansion platforms to perform volume reduction, washing, and harvesting with a low output volume.
- Published
- 2023
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18. An allied reprogramming, selection, expansion and differentiation platform for creating hiPSC on microcarriers.
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Lam ATL, Ho V, Vassilev S, Reuveny S, and Oh SKW
- Abstract
Objectives: Induced pluripotent stem cells (iPSCs) generated by monolayer cultures is plagued by low efficiencies, high levels of manipulation and operator unpredictability. We have developed a platform, reprogramming, expansion, and differentiation on Microcarriers, to solve these challenges., Materials and Methods: Five sources of human somatic cells were reprogrammed, selected, expanded and differentiated in microcarriers suspension cultures., Results: Improvement of transduction efficiencies up to 2 times was observed. Accelerated reprogramming in microcarrier cultures was 7 days faster than monolayer, providing between 30 and 50-fold more clones to choose from fibroblasts, peripheral blood mononuclear cells, T cells and CD34+ stem cells. This was observed to be due to an earlier induction of genes (β-catenin, E-cadherin and EpCAM) on day 4 versus monolayer cultures which occurred on days 14 or later. Following that, faster induction and earlier stabilization of pluripotency genes occurred during the maturation phase of reprogramming. Integrated expansion without trypsinization and efficient differentiation, without embryoid bodies formation, to the three germ-layers, cardiomyocytes and haematopoietic stem cells were further demonstrated., Conclusions: Our method can solve the inherent problems of conventional monolayer cultures. It is highly efficient, cell dissociation free, can be operated with lower labor, and allows testing of differentiation efficiency without trypsinization and generation of embryoid bodies. It is also amenable to automation for processing more samples in a small footprint, alleviating many challenges of manual monolayer selection., (© 2022 The Authors. Cell Proliferation published by John Wiley & Sons Ltd.)
- Published
- 2022
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19. Selection of O-negative induced pluripotent stem cell clones for high-density red blood cell production in a scalable perfusion bioreactor system.
- Author
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Yu S, Vassilev S, Lim ZR, Sivalingam J, Lam ATL, Ho V, Renia L, Malleret B, Reuveny S, and Oh SKW
- Subjects
- Bioreactors, Cell Differentiation, Clone Cells, Erythrocytes, Erythropoiesis, Humans, Perfusion, Induced Pluripotent Stem Cells
- Abstract
Objectives: Large-scale generation of universal red blood cells (RBCs) from O-negative (O-ve) human induced pluripotent stem cells (hiPSCs) holds the potential to alleviate worldwide shortages of blood and provide a safe and secure year-round supply. Mature RBCs and reticulocytes, the immature counterparts of RBCs generated during erythropoiesis, could also find important applications in research, for example in malaria parasite infection studies. However, one major challenge is the lack of a high-density culture platform for large-scale generation of RBCs in vitro., Materials and Methods: We generated 10 O-ve hiPSC clones and evaluated their potential for mesoderm formation and erythroid differentiation. We then used a perfusion bioreactor system to perform studies with high-density cultures of erythroblasts in vitro., Results: Based on their tri-lineage (and specifically mesoderm) differentiation potential, we isolated six hiPSC clones capable of producing functional erythroblasts. Using the best performing clone, we demonstrated the small-scale generation of high-density cultures of erythroblasts in a perfusion bioreactor system. After process optimization, we were able to achieve a peak cell density of 34.7 million cells/ml with 92.2% viability in the stirred bioreactor. The cells expressed high levels of erythroblast markers, showed oxygen carrying capacity, and were able to undergo enucleation., Conclusions: This study demonstrated a scalable platform for the production of functional RBCs from hiPSCs. The perfusion culture platform we describe here could pave the way for large volume-controlled bioreactor culture for the industrial generation of high cell density erythroblasts and RBCs., (© 2022 The Authors. Cell Proliferation published by John Wiley & Sons Ltd.)
- Published
- 2022
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20. SpatialExperiment: infrastructure for spatially-resolved transcriptomics data in R using Bioconductor.
- Author
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Righelli D, Weber LM, Crowell HL, Pardo B, Collado-Torres L, Ghazanfar S, Lun ATL, Hicks SC, and Risso D
- Subjects
- Genomics, Software, Transcriptome
- Abstract
Summary: SpatialExperiment is a new data infrastructure for storing and accessing spatially-resolved transcriptomics data, implemented within the R/Bioconductor framework, which provides advantages of modularity, interoperability, standardized operations and comprehensive documentation. Here, we demonstrate the structure and user interface with examples from the 10x Genomics Visium and seqFISH platforms, and provide access to example datasets and visualization tools in the STexampleData, TENxVisiumData and ggspavis packages., Availability and Implementation: The SpatialExperiment, STexampleData, TENxVisiumData and ggspavis packages are available from Bioconductor. The package versions described in this manuscript are available in Bioconductor version 3.15 onwards., Supplementary Information: Supplementary data are available at Bioinformatics online., (© The Author(s) 2022. Published by Oxford University Press.)
- Published
- 2022
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21. Locus-specific expression of transposable elements in single cells with CELLO-seq.
- Author
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Berrens RV, Yang A, Laumer CE, Lun ATL, Bieberich F, Law CT, Lan G, Imaz M, Bowness JS, Brockdorff N, Gaffney DJ, and Marioni JC
- Subjects
- Animals, Humans, Mice, RNA, DNA Transposable Elements genetics, Induced Pluripotent Stem Cells
- Abstract
Transposable elements (TEs) regulate diverse biological processes, from early development to cancer. Expression of young TEs is difficult to measure with next-generation, single-cell sequencing technologies because their highly repetitive nature means that short complementary DNA reads cannot be unambiguously mapped to a specific locus. Single CELl LOng-read RNA-sequencing (CELLO-seq) combines long-read single cell RNA-sequencing with computational analyses to measure TE expression at unique loci. We used CELLO-seq to assess the widespread expression of TEs in two-cell mouse blastomeres as well as in human induced pluripotent stem cells. Across both species, old and young TEs showed evidence of locus-specific expression with simulations demonstrating that only a small number of very young elements in the mouse could not be mapped back to the reference with high confidence. Exploring the relationship between the expression of individual elements and putative regulators revealed large heterogeneity, with TEs within a class showing different patterns of correlation and suggesting distinct regulatory mechanisms., (© 2021. The Author(s), under exclusive licence to Springer Nature America, Inc.)
- Published
- 2022
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22. A high-content RNAi screen reveals multiple roles for long noncoding RNAs in cell division.
- Author
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Stojic L, Lun ATL, Mascalchi P, Ernst C, Redmond AM, Mangei J, Barr AR, Bousgouni V, Bakal C, Marioni JC, Odom DT, and Gergely F
- Subjects
- HeLa Cells, High-Throughput Screening Assays, Humans, Mitosis genetics, Mitosis physiology, Proteins genetics, RNA Interference physiology, Cell Division genetics, Cell Division physiology, RNA, Long Noncoding genetics
- Abstract
Genome stability relies on proper coordination of mitosis and cytokinesis, where dynamic microtubules capture and faithfully segregate chromosomes into daughter cells. With a high-content RNAi imaging screen targeting more than 2,000 human lncRNAs, we identify numerous lncRNAs involved in key steps of cell division such as chromosome segregation, mitotic duration and cytokinesis. Here, we provide evidence that the chromatin-associated lncRNA, linc00899, leads to robust mitotic delay upon its depletion in multiple cell types. We perform transcriptome analysis of linc00899-depleted cells and identify the neuronal microtubule-binding protein, TPPP/p25, as a target of linc00899. We further show that linc00899 binds TPPP/p25 and suppresses its transcription. In cells depleted of linc00899, upregulation of TPPP/p25 alters microtubule dynamics and delays mitosis. Overall, our comprehensive screen uncovers several lncRNAs involved in genome stability and reveals a lncRNA that controls microtubule behaviour with functional implications beyond cell division.
- Published
- 2020
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23. Orchestrating single-cell analysis with Bioconductor.
- Author
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Amezquita RA, Lun ATL, Becht E, Carey VJ, Carpp LN, Geistlinger L, Marini F, Rue-Albrecht K, Risso D, Soneson C, Waldron L, Pagès H, Smith ML, Huber W, Morgan M, Gottardo R, and Hicks SC
- Subjects
- Gene Expression Profiling, Genome, High-Throughput Nucleotide Sequencing, Software, Single-Cell Analysis methods
- Abstract
Recent technological advancements have enabled the profiling of a large number of genome-wide features in individual cells. However, single-cell data present unique challenges that require the development of specialized methods and software infrastructure to successfully derive biological insights. The Bioconductor project has rapidly grown to meet these demands, hosting community-developed open-source software distributed as R packages. Featuring state-of-the-art computational methods, standardized data infrastructure and interactive data visualization tools, we present an overview and online book (https://osca.bioconductor.org) of single-cell methods for prospective users.
- Published
- 2020
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24. EmptyDrops: distinguishing cells from empty droplets in droplet-based single-cell RNA sequencing data.
- Author
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Lun ATL, Riesenfeld S, Andrews T, Dao TP, Gomes T, and Marioni JC
- Subjects
- Biomarkers metabolism, Humans, Monocytes cytology, Neurons cytology, High-Throughput Nucleotide Sequencing methods, Microfluidic Analytical Techniques methods, Monocytes metabolism, Neurons metabolism, Sequence Analysis, RNA methods, Single-Cell Analysis methods
- Abstract
Droplet-based single-cell RNA sequencing protocols have dramatically increased the throughput of single-cell transcriptomics studies. A key computational challenge when processing these data is to distinguish libraries for real cells from empty droplets. Here, we describe a new statistical method for calling cells from droplet-based data, based on detecting significant deviations from the expression profile of the ambient solution. Using simulations, we demonstrate that EmptyDrops has greater power than existing approaches while controlling the false discovery rate among detected cells. Our method also retains distinct cell types that would have been discarded by existing methods in several real data sets.
- Published
- 2019
- Full Text
- View/download PDF
25. Transcriptional Heterogeneity in Naive and Primed Human Pluripotent Stem Cells at Single-Cell Resolution.
- Author
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Messmer T, von Meyenn F, Savino A, Santos F, Mohammed H, Lun ATL, Marioni JC, and Reik W
- Subjects
- Cell Line, Human Embryonic Stem Cells cytology, Humans, Epigenesis, Genetic, Human Embryonic Stem Cells metabolism, Sequence Analysis, RNA, Single-Cell Analysis, Transcription, Genetic
- Abstract
Conventional human embryonic stem cells are considered to be primed pluripotent but can be induced to enter a naive state. However, the transcriptional features associated with naive and primed pluripotency are still not fully understood. Here we used single-cell RNA sequencing to characterize the differences between these conditions. We observed that both naive and primed populations were mostly homogeneous with no clear lineage-related structure and identified an intermediate subpopulation of naive cells with primed-like expression. We found that the naive-primed pluripotency axis is preserved across species, although the timing of the transition to a primed state is species specific. We also identified markers for distinguishing human naive and primed pluripotency as well as strong co-regulatory relationships between lineage markers and epigenetic regulators that were exclusive to naive cells. Our data provide valuable insights into the transcriptional landscape of human pluripotency at a cellular and genome-wide resolution., (Crown Copyright © 2019. Published by Elsevier Inc. All rights reserved.)
- Published
- 2019
- Full Text
- View/download PDF
26. Transcription-factor-mediated supervision of global genome architecture maintains B cell identity.
- Author
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Johanson TM, Lun ATL, Coughlan HD, Tan T, Smyth GK, Nutt SL, and Allan RS
- Subjects
- Animals, B-Lymphocytes metabolism, Male, Mice, Mice, Inbred C57BL, PAX5 Transcription Factor metabolism, B-Lymphocytes cytology, Cell Differentiation genetics, Cell Lineage genetics, PAX5 Transcription Factor genetics
- Abstract
Recent studies have elucidated cell-lineage-specific three-dimensional genome organization; however, how such specific architecture is established or maintained is unclear. We hypothesized that lineage-defining transcription factors maintain cell identity via global control of genome organization. These factors bind many genomic sites outside of the genes that they directly regulate and thus are potentially implicated in three-dimensional genome organization. Using chromosome-conformation-capture techniques, we show that the transcription factor Paired box 5 (Pax5) is critical for the establishment and maintenance of the global lineage-specific architecture of B cells. Pax5 was found to supervise genome architecture throughout B cell differentiation, until the plasmablast stage, in which Pax5 is naturally silenced and B cell-specific genome structure is lost. Crucially, Pax5 did not rely on ongoing transcription to organize the genome. These results implicate sequence-specific DNA-binding proteins in global genome organization to establish and maintain lineage fidelity.
- Published
- 2018
- Full Text
- View/download PDF
27. COMRADES determines in vivo RNA structures and interactions.
- Author
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Ziv O, Gabryelska MM, Lun ATL, Gebert LFR, Sheu-Gruttadauria J, Meredith LW, Liu ZY, Kwok CK, Qin CF, MacRae IJ, Goodfellow I, Marioni JC, Kudla G, and Miska EA
- Subjects
- Humans, RNA-Binding Proteins chemistry, Sequence Analysis, RNA methods, Transcriptome, Zika Virus isolation & purification, Zika Virus Infection genetics, Zika Virus Infection virology, High-Throughput Nucleotide Sequencing methods, Nucleic Acid Conformation, RNA, Viral chemistry, RNA, Viral metabolism, RNA-Binding Proteins metabolism, Zika Virus physiology, Zika Virus Infection metabolism
- Abstract
The structural flexibility of RNA underlies fundamental biological processes, but there are no methods for exploring the multiple conformations adopted by RNAs in vivo. We developed cross-linking of matched RNAs and deep sequencing (COMRADES) for in-depth RNA conformation capture, and a pipeline for the retrieval of RNA structural ensembles. Using COMRADES, we determined the architecture of the Zika virus RNA genome inside cells, and identified multiple site-specific interactions with human noncoding RNAs.
- Published
- 2018
- Full Text
- View/download PDF
28. T cell cytolytic capacity is independent of initial stimulation strength.
- Author
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Richard AC, Lun ATL, Lau WWY, Göttgens B, Marioni JC, and Griffiths GM
- Subjects
- Animals, Cell Line, Genome, Lymphocyte Activation, Mice, Mice, Inbred C57BL, RNA genetics, Signal Transduction, Single-Cell Analysis, CD8-Positive T-Lymphocytes physiology, Cytotoxicity, Immunologic, Receptors, Antigen, T-Cell, alpha-beta metabolism
- Abstract
How cells respond to myriad stimuli with finite signaling machinery is central to immunology. In naive T cells, the inherent effect of ligand strength on activation pathways and endpoints has remained controversial, confounded by environmental fluctuations and intercellular variability within populations. Here we studied how ligand potency affected the activation of CD8
+ T cells in vitro, through the use of genome-wide RNA, multi-dimensional protein and functional measurements in single cells. Our data revealed that strong ligands drove more efficient and uniform activation than did weak ligands, but all activated cells were fully cytolytic. Notably, activation followed the same transcriptional pathways regardless of ligand potency. Thus, stimulation strength did not intrinsically dictate the T cell-activation route or phenotype; instead, it controlled how rapidly and simultaneously the cells initiated activation, allowing limited machinery to elicit wide-ranging responses.- Published
- 2018
- Full Text
- View/download PDF
29. Detection and removal of barcode swapping in single-cell RNA-seq data.
- Author
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Griffiths JA, Richard AC, Bach K, Lun ATL, and Marioni JC
- Subjects
- Animals, DNA Probes genetics, Humans, Mice, Models, Genetic, Reproducibility of Results, DNA genetics, Genomics methods, Sequence Analysis, RNA methods, Single-Cell Analysis methods
- Abstract
Barcode swapping results in the mislabelling of sequencing reads between multiplexed samples on patterned flow-cell Illumina sequencing machines. This may compromise the validity of numerous genomic assays; however, the severity and consequences of barcode swapping remain poorly understood. We have used two statistical approaches to robustly quantify the fraction of swapped reads in two plate-based single-cell RNA-sequencing datasets. We found that approximately 2.5% of reads were mislabelled between samples on the HiSeq 4000, which is lower than previous reports. We observed no correlation between the swapped fraction of reads and the concentration of free barcode across plates. Furthermore, we have demonstrated that barcode swapping may generate complex but artefactual cell libraries in droplet-based single-cell RNA-sequencing studies. To eliminate these artefacts, we have developed an algorithm to exclude individual molecules that have swapped between samples in 10x Genomics experiments, allowing the continued use of cutting-edge sequencing machines for these assays.
- Published
- 2018
- Full Text
- View/download PDF
30. Specificity of RNAi, LNA and CRISPRi as loss-of-function methods in transcriptional analysis.
- Author
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Stojic L, Lun ATL, Mangei J, Mascalchi P, Quarantotti V, Barr AR, Bakal C, Marioni JC, Gergely F, and Odom DT
- Subjects
- Gene Expression Profiling, HEK293 Cells, HeLa Cells, Humans, Proteins genetics, RNA, Long Noncoding metabolism, CRISPR-Cas Systems, Gene Knockdown Techniques, Oligonucleotides, Oligonucleotides, Antisense chemistry, RNA Interference, Transcription, Genetic
- Abstract
Loss-of-function (LOF) methods such as RNA interference (RNAi), antisense oligonucleotides or CRISPR-based genome editing provide unparalleled power for studying the biological function of genes of interest. However, a major concern is non-specific targeting, which involves depletion of transcripts other than those intended. Little work has been performed to characterize the off-target effects of these common LOF methods at the whole-transcriptome level. Here, we experimentally compared the non-specific activity of RNAi, antisense oligonucleotides and CRISPR interference (CRISPRi). All three methods yielded non-negligible off-target effects in gene expression, with CRISPRi also exhibiting strong clonal effects. As an illustrative example, we evaluated the performance of each method for determining the role of an uncharacterized long noncoding RNA (lncRNA). Several LOF methods successfully depleted the candidate lncRNA but yielded different sets of differentially expressed genes as well as a different cellular phenotype upon depletion. Similar discrepancies between methods were observed with a protein-coding gene (Ch-TOG/CKAP5) and another lncRNA (MALAT1). We suggest that the differences between methods arise due to method-specific off-target effects and provide guidelines for mitigating such effects in functional studies. Our recommendations provide a framework with which off-target effects can be managed to improve functional characterization of genes of interest.
- Published
- 2018
- Full Text
- View/download PDF
31. Improved erythroid differentiation of multiple human pluripotent stem cell lines in microcarrier culture by modulation of Wnt/β-Catenin signaling.
- Author
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Sivalingam J, Chen HY, Yang BX, Lim ZR, Lam ATL, Woo TL, Chen AK, Reuveny S, Loh YH, and Oh SK
- Subjects
- Biomarkers, Cell Culture Techniques, Cell Line, Erythroblasts cytology, Erythroblasts metabolism, Humans, Cell Differentiation genetics, Erythropoiesis genetics, Pluripotent Stem Cells cytology, Pluripotent Stem Cells metabolism, Wnt Signaling Pathway
- Published
- 2018
- Full Text
- View/download PDF
32. iSEE: Interactive SummarizedExperiment Explorer.
- Author
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Rue-Albrecht K, Marini F, Soneson C, and Lun ATL
- Abstract
Data exploration is critical to the comprehension of large biological data sets generated by high-throughput assays such as sequencing. However, most existing tools for interactive visualisation are limited to specific assays or analyses. Here, we present the iSEE (Interactive SummarizedExperiment Explorer) software package, which provides a general visual interface for exploring data in a SummarizedExperiment object. iSEE is directly compatible with many existing R/Bioconductor packages for analysing high-throughput biological data, and provides useful features such as simultaneous examination of (meta)data and analysis results, dynamic linking between plots and code tracking for reproducibility. We demonstrate the utility and flexibility of iSEE by applying it to explore a range of real transcriptomics and proteomics data sets., Competing Interests: No competing interests were disclosed.
- Published
- 2018
- Full Text
- View/download PDF
33. Genome-wide analysis reveals no evidence of trans chromosomal regulation of mammalian immune development.
- Author
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Johanson TM, Coughlan HD, Lun ATL, Bediaga NG, Naselli G, Garnham AL, Harrison LC, Smyth GK, and Allan RS
- Subjects
- Animals, Chromatin chemistry, Chromatin genetics, Chromatin metabolism, Chromosomes, Mammalian chemistry, Chromosomes, Mammalian metabolism, DNA chemistry, DNA genetics, DNA metabolism, Flow Cytometry, Genome, Humans, Male, Mice, Mice, Inbred C57BL, Nucleic Acid Conformation, Stereoisomerism, Chromosomes, Mammalian genetics, Gene Expression Regulation, Immunity, Cellular genetics, Mammals physiology
- Abstract
It has been proposed that interactions between mammalian chromosomes, or transchromosomal interactions (also known as kissing chromosomes), regulate gene expression and cell fate determination. Here we aimed to identify novel transchromosomal interactions in immune cells by high-resolution genome-wide chromosome conformation capture. Although we readily identified stable interactions in cis, and also between centromeres and telomeres on different chromosomes, surprisingly we identified no gene regulatory transchromosomal interactions in either mouse or human cells, including previously described interactions. We suggest that advances in the chromosome conformation capture technique and the unbiased nature of this approach allow more reliable capture of interactions between chromosomes than previous methods. Overall our findings suggest that stable transchromosomal interactions that regulate gene expression are not present in mammalian immune cells and that lineage identity is governed by cis, not trans chromosomal interactions., Competing Interests: The authors have declared that no competing interests exist.
- Published
- 2018
- Full Text
- View/download PDF
34. Batch effects in single-cell RNA-sequencing data are corrected by matching mutual nearest neighbors.
- Author
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Haghverdi L, Lun ATL, Morgan MD, and Marioni JC
- Subjects
- Algorithms, Cluster Analysis, Data Analysis, High-Throughput Nucleotide Sequencing methods, Sequence Analysis, RNA methods, Single-Cell Analysis methods
- Abstract
Large-scale single-cell RNA sequencing (scRNA-seq) data sets that are produced in different laboratories and at different times contain batch effects that may compromise the integration and interpretation of the data. Existing scRNA-seq analysis methods incorrectly assume that the composition of cell populations is either known or identical across batches. We present a strategy for batch correction based on the detection of mutual nearest neighbors (MNNs) in the high-dimensional expression space. Our approach does not rely on predefined or equal population compositions across batches; instead, it requires only that a subset of the population be shared between batches. We demonstrate the superiority of our approach compared with existing methods by using both simulated and real scRNA-seq data sets. Using multiple droplet-based scRNA-seq data sets, we demonstrate that our MNN batch-effect-correction method can be scaled to large numbers of cells.
- Published
- 2018
- Full Text
- View/download PDF
35. beachmat: A Bioconductor C++ API for accessing high-throughput biological data from a variety of R matrix types.
- Author
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Lun ATL, Pagès H, and Smith ML
- Subjects
- Algorithms, Databases, Genetic, Humans, Computational Biology methods, High-Throughput Nucleotide Sequencing methods, Sequence Analysis, RNA methods, Software
- Abstract
Biological experiments involving genomics or other high-throughput assays typically yield a data matrix that can be explored and analyzed using the R programming language with packages from the Bioconductor project. Improvements in the throughput of these assays have resulted in an explosion of data even from routine experiments, which poses a challenge to the existing computational infrastructure for statistical data analysis. For example, single-cell RNA sequencing (scRNA-seq) experiments frequently generate large matrices containing expression values for each gene in each cell, requiring sparse or file-backed representations for memory-efficient manipulation in R. These alternative representations are not easily compatible with high-performance C++ code used for computationally intensive tasks in existing R/Bioconductor packages. Here, we describe a C++ interface named beachmat, which enables agnostic data access from various matrix representations. This allows package developers to write efficient C++ code that is interoperable with dense, sparse and file-backed matrices, amongst others. We evaluated the performance of beachmat for accessing data from each matrix representation using both simulated and real scRNA-seq data, and defined a clear memory/speed trade-off to motivate the choice of an appropriate representation. We also demonstrate how beachmat can be incorporated into the code of other packages to drive analyses of a very large scRNA-seq data set.
- Published
- 2018
- Full Text
- View/download PDF
36. Isolation and Comparative Transcriptome Analysis of Human Fetal and iPSC-Derived Cone Photoreceptor Cells.
- Author
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Welby E, Lakowski J, Di Foggia V, Budinger D, Gonzalez-Cordero A, Lun ATL, Epstein M, Patel A, Cuevas E, Kruczek K, Naeem A, Minneci F, Hubank M, Jones DT, Marioni JC, Ali RR, and Sowden JC
- Subjects
- Cell Differentiation genetics, Fetus cytology, Fetus metabolism, Gene Expression Profiling methods, Gene Expression Regulation, Developmental genetics, Humans, Induced Pluripotent Stem Cells transplantation, Retina growth & development, Retina metabolism, Retina pathology, Retinal Cone Photoreceptor Cells transplantation, Retinal Degeneration pathology, Induced Pluripotent Stem Cells metabolism, Retinal Cone Photoreceptor Cells metabolism, Retinal Degeneration genetics, Rod Opsins genetics, Transcriptome genetics
- Abstract
Loss of cone photoreceptors, crucial for daylight vision, has the greatest impact on sight in retinal degeneration. Transplantation of stem cell-derived L/M-opsin cones, which form 90% of the human cone population, could provide a feasible therapy to restore vision. However, transcriptomic similarities between fetal and stem cell-derived cones remain to be defined, in addition to development of cone cell purification strategies. Here, we report an analysis of the human L/M-opsin cone photoreceptor transcriptome using an AAV2/9.pR2.1:GFP reporter. This led to the identification of a cone-enriched gene signature, which we used to demonstrate similar gene expression between fetal and stem cell-derived cones. We then defined a cluster of differentiation marker combination that, when used for cell sorting, significantly enriches for cone photoreceptors from the fetal retina and stem cell-derived retinal organoids, respectively. These data may facilitate more efficient isolation of human stem cell-derived cones for use in clinical transplantation studies., (Copyright © 2017 The Authors. Published by Elsevier Inc. All rights reserved.)
- Published
- 2017
- Full Text
- View/download PDF
37. Assessing the reliability of spike-in normalization for analyses of single-cell RNA sequencing data.
- Author
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Lun ATL, Calero-Nieto FJ, Haim-Vilmovsky L, Göttgens B, and Marioni JC
- Subjects
- Algorithms, Animals, Cell Line, Gene Expression Profiling standards, Gene Expression Regulation, Mice, Reproducibility of Results, Sequence Analysis, RNA standards, Single-Cell Analysis standards
- Abstract
By profiling the transcriptomes of individual cells, single-cell RNA sequencing provides unparalleled resolution to study cellular heterogeneity. However, this comes at the cost of high technical noise, including cell-specific biases in capture efficiency and library generation. One strategy for removing these biases is to add a constant amount of spike-in RNA to each cell and to scale the observed expression values so that the coverage of spike-in transcripts is constant across cells. This approach has previously been criticized as its accuracy depends on the precise addition of spike-in RNA to each sample. Here, we perform mixture experiments using two different sets of spike-in RNA to quantify the variance in the amount of spike-in RNA added to each well in a plate-based protocol. We also obtain an upper bound on the variance due to differences in behavior between the two spike-in sets. We demonstrate that both factors are small contributors to the total technical variance and have only minor effects on downstream analyses, such as detection of highly variable genes and clustering. Our results suggest that scaling normalization using spike-in transcripts is reliable enough for routine use in single-cell RNA sequencing data analyses., (© 2017 Lun et al.; Published by Cold Spring Harbor Laboratory Press.)
- Published
- 2017
- Full Text
- View/download PDF
38. Overcoming confounding plate effects in differential expression analyses of single-cell RNA-seq data.
- Author
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Lun ATL and Marioni JC
- Subjects
- Base Sequence, High-Throughput Nucleotide Sequencing, Humans, RNA, Single-Cell Analysis, Software, Transcriptome, Gene Expression Profiling, Models, Statistical, Sequence Analysis, RNA
- Abstract
An increasing number of studies are using single-cell RNA-sequencing (scRNA-seq) to characterize the gene expression profiles of individual cells. One common analysis applied to scRNA-seq data involves detecting differentially expressed (DE) genes between cells in different biological groups. However, many experiments are designed such that the cells to be compared are processed in separate plates or chips, meaning that the groupings are confounded with systematic plate effects. This confounding aspect is frequently ignored in DE analyses of scRNA-seq data. In this article, we demonstrate that failing to consider plate effects in the statistical model results in loss of type I error control. A solution is proposed whereby counts are summed from all cells in each plate and the count sums for all plates are used in the DE analysis. This restores type I error control in the presence of plate effects without compromising detection power in simulated data. Summation is also robust to varying numbers and library sizes of cells on each plate. Similar results are observed in DE analyses of real data where the use of count sums instead of single-cell counts improves specificity and the ranking of relevant genes. This suggests that summation can assist in maintaining statistical rigour in DE analyses of scRNA-seq data with plate effects., (© The Author 2017. Published by Oxford University Press.)
- Published
- 2017
- Full Text
- View/download PDF
39. Testing for differential abundance in mass cytometry data.
- Author
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Lun ATL, Richard AC, and Marioni JC
- Subjects
- Computer Simulation, Flow Cytometry methods, Image Processing, Computer-Assisted methods, Software
- Abstract
When comparing biological conditions using mass cytometry data, a key challenge is to identify cellular populations that change in abundance. Here, we present a computational strategy for detecting 'differentially abundant' populations by assigning cells to hyperspheres, testing for significant differences between conditions and controlling the spatial false discovery rate. Our method (http://bioconductor.org/packages/cydar) outperforms other approaches in simulations and finds novel patterns of differential abundance in real data.
- Published
- 2017
- Full Text
- View/download PDF
40. No counts, no variance: allowing for loss of degrees of freedom when assessing biological variability from RNA-seq data.
- Author
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Lun ATL and Smyth GK
- Subjects
- Base Sequence, Linear Models, RNA chemistry, Gene Expression Profiling methods, Sequence Analysis, RNA, Software
- Abstract
RNA sequencing (RNA-seq) is widely used to study gene expression changes associated with treatments or biological conditions. Many popular methods for detecting differential expression (DE) from RNA-seq data use generalized linear models (GLMs) fitted to the read counts across independent replicate samples for each gene. This article shows that the standard formula for the residual degrees of freedom (d.f.) in a linear model is overstated when the model contains fitted values that are exactly zero. Such fitted values occur whenever all the counts in a treatment group are zero as well as in more complex models such as those involving paired comparisons. This misspecification results in underestimation of the genewise variances and loss of type I error control. This article proposes a formula for the reduced residual d.f. that restores error control in simulated RNA-seq data and improves detection of DE genes in a real data analysis. The new approach is implemented in the quasi-likelihood framework of the edgeR software package. The results of this article also apply to RNA-seq analyses that apply linear models to log-transformed counts, such as those in the limma software package, and more generally to any count-based GLM where exactly zero fitted values are possible.
- Published
- 2017
- Full Text
- View/download PDF
41. RUNX2 Mediates Plasmacytoid Dendritic Cell Egress from the Bone Marrow and Controls Viral Immunity.
- Author
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Chopin M, Preston SP, Lun ATL, Tellier J, Smyth GK, Pellegrini M, Belz GT, Corcoran LM, Visvader JE, Wu L, and Nutt SL
- Abstract
Plasmacytoid dendritic cells (pDCs) represent a unique immune cell type that responds to viral nucleic acids through the rapid production of type I interferons. Within the hematopoietic system, the transcription factor RUNX2 is exclusively expressed in pDCs and is required for their peripheral homeostasis. Here, we show that RUNX2 plays an essential role in promoting pDC localization and function. RUNX2 is required for the appropriate expression of the integrin-mediated adhesion machinery, as well as for the down-modulation of the chemokine receptor CXCR4, which allows pDC egress into the circulation. RUNX2 also facilitates the robust response to viral infection through the control of IRF7, the major regulator of type I interferon production. Mice lacking one copy of Runx2 have reduced numbers of peripheral pDCs and IFN-α expression, which might contribute to the reported difficulties of individuals with cleidocranial dysplasia, who are haploinsufficient for RUNX2, to clear viral infections., (Copyright © 2016 The Authors. Published by Elsevier Inc. All rights reserved.)
- Published
- 2016
- Full Text
- View/download PDF
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