Project description:Single-cell sequencing technologies are revolutionizing biology, but are limited by the need of dissociating fresh samples that can only be fixed at later stages. We present ACME (ACetic-MEthanol) dissociation, a species-versatile cell dissociation approach that fixes cells as they are being dissociated. ACME-dissociated cells have high RNA integrity, can be cryopreserved multiple times, can be sorted by Fluorescence-Activated Cell Sorting (FACS) and are permeable, enabling combinatorial approaches of single-cell transcriptomics. ACME is based on cheap reagents and it can be done in most labs and even sampling trips. As a proof of principle, we have performed SPLiT-seq with ACME cells to obtain around ~35K cells from two planarian species and identified all previously described cell types in similar proportions. This technique allows fixed, dissociated cells to be obtained from diverse organisms that can be cryopreserved and subjected to combinatorial barcoding methods for single-cell transcriptomics and thus will accelerate our knowledge of cell types across the tree of life.
Project description:The use of single-cell technologies for clinical applications requires disconnecting sampling from downstream processing steps. Early sample preservation can further increase robustness and reproducibility by avoiding artifacts introduced during specimen handling. We present FixNCut, a methodology for the reversible fixation of tissue followed by dissociation that overcomes current limitations. We applied FixNCut to human and mouse tissues to demonstrate the preservation of RNA integrity, sequencing library complexity, and cellular composition, while diminishing stress-related artifacts. Besides single-cell RNA sequencing, FixNCut is compatible with multiple single-cell and spatial technologies, making it a versatile tool for robust and flexible study designs.
Project description:Single-cell sequencing technologies are revolutionizing biology, but they are limited by the need to dissociate live samples. Here, we present ACME (ACetic-MEthanol), a dissociation approach for single-cell transcriptomics that simultaneously fixes cells. ACME-dissociated cells have high RNA integrity, can be cryopreserved multiple times, and are sortable and permeable. As a proof of principle, we provide single-cell transcriptomic data of different species, using both droplet-based and combinatorial barcoding single-cell methods. ACME uses affordable reagents, can be done in most laboratories and even in the field, and thus will accelerate our knowledge of cell types across the tree of life.
Project description:Single-cell transcriptomics methods have become very popular to study the cellular composition of organs and tissues and characterize the expression profiles of the individual cells that compose them. The main critical step for single-cell transcriptomics methods is sample preparation. Several methods have been developed to preserve cells after sample dissociation to uncouple sample handling from library preparation. Yet, the suitability of these methods depends on the types of cells to be processed. In this project, we perform a systematic comparison of preservation methods for droplet-based single-cell RNA-seq (scRNA-seq) on human neural progenitor cell populations derived from induced pluripotent stem cells (iPSCs) and highlight their strengths and weaknesses. We compared the cellular composition and expression profile of single-cell suspensions from fresh NPCs with that of NPCs preserved with Dimethyl Sulfoxide (DMSO), Methanol, vivoPHIX and Acetil-methanol (ACME). Our results show that while DMSO provides the highest cell quality in terms of RNA molecules and genes detected per cell. Yet, it strongly affects the cellular composition and the expression profile of the resulting datasets. In contrast, methanol fixed samples display a cellular composition like that of fresh samples while providing a good cell quality and smaller expression biases. Taken together, our results show that methanol fixation is the method of choice for performing droplet-based single-cell transcriptomics experiments on neural cell populations.
Project description:Next-generation sequencing has been widely used for the genome-wide profiling of histone modifications, transcription factor binding and gene expression through chromatin immunoprecipitated DNA sequencing (ChIP-seq) and cDNA sequencing (RNA-seq). Here, we describe a versatile library construction method that can be applied to both ChIP-seq and RNA-seq on the widely used Illumina platforms. Standard methods for ChIP-seq library construction require nanograms of starting DNA, substantially limiting its application to rare cell types or limited clinical samples. By minimizing the DNA purification steps that cause major sample loss, our method achieved a high sensitivity in ChIP-seq library preparation. Using this method, we achieved the following: (1) generated high-quality epigenomic and transcription factor-binding maps using ChIP-seq for murine adipocytes; (2) successfully prepared a ChIP-seq library from as little as 25 pg of starting DNA; (3) achieved paired-end sequencing of the ChIP-seq libraries; (4) systematically profiled gene expression dynamics during murine adipogenesis using RNA-seq; and (5) preserved the strand specificity of the transcripts in RNA-seq. Given its sensitivity and versatility in both double-stranded and single-stranded DNA library construction, this method has wide applications in genomic, epigenomic, transcriptomic and interactomic studies. Pre-adipocytes and mature adipocytes were collected. Their chromatin and RNA were subjected to ChIP and mRNA extraction. Sequencing libraries from ChIP DNA or mRNA were generated following either standard protocols or TELP method. The quality and features of TELP libraries were proved and demonstrated in comparison with standard libraries or other published data.
Project description:Background: Interest in single-cell whole transcriptome analysis is growing rapidly, especially for profiling rare or heterogeneous populations of cells. In almost all reported works, investigators have used live cells which represent several inconveniences and limitations. Some recent cell fixation methods did not work with most primary cells including immune cells. Methods: The methanol-fixation and new processing method was introduced to preserve PBMCs for single-cell RNA sequencing (scRNA-Seq) analysis on 10X Chromium platform. Results: When methanol fixation protocol was broken up into three steps, we found that PBMC RNA was degraded during rehydration with PBS, not at cell fixation and up to three-month storage steps. Resuspension but not rehydration in 3X saline sodium citrate (SSC) buffer instead of PBS preserved PBMC RNA integrity and prevented RNA leakage. Diluted SSC buffer did not interfere with full-length cDNA synthesis. The methanol-fixed PBMCs resuspended in 3X SSC were successfully implemented into 10X Chromium standard scRNA-seq workflows with no elevated low quality cells and cell doublets. The fixation process did not alter the single-cell transcriptional profiles and gene expression levels. Major subpopulations classified by marker genes could be identified in fixed PBMCs at a similar proportion as in live PBMCs. This new fixation processing protocol was validated in CD8+ T cell and several other cell types. Conclusions: We expect that the methanol-based cell fixation procedure presented here will substantially enable complex experimental design with primary cells at single cell resolution.
Project description:Long-read RNA sequencing (RNA-seq) is a powerful technology for transcriptome analysis, but the relatively low throughput of current long-read sequencing platforms limits transcript coverage. We present TEQUILA-seq, a versatile, easy-to-implement, and low-cost method for targeted long-read RNA-seq. TEQUILA-seq can be broadly used for targeted sequencing of full-length transcripts in diverse biomedical research settings.