Gene Expression
Nebulas
Gene Expression NebulasSummary: Transcriptional enhancers orchestrate cell-type specific gene expression programs critical to eukaryotic development, physiology, and disease. However, despite the large number of enhancers now identified, only a small number have been functionally assessed. Here, we develop MOsaic Single-cell Analysis by Indexed CRISPR Sequencing (Mosaic-seq), a method that measures one direct phenotype of enhancer repression: change of the transcriptome, at the single cell level. Using dCas9-KRAB to suppress enhancer function, we first implement a multiplexed system to allow the simultaneous measurement of the transcriptome and detection of sgRNAs by single cell RNA sequencing. We validate this approach by targeting the HS2 enhancer in the well-studied beta-globin locus. Next, through computational simulation, we demonstrate strategies to robustly detect changes in gene expression in these single cell measurements. Finally, we use Mosaic-seq to target 71 hypersensitive regions belonging to 15 super-enhancers in K562 cells by utilizing a lentiviral library containing 241 unique-barcoded sgRNAs. Our results demonstrate that Mosaic-seq is a reliable approach to study enhancer function in single cells in a high-throughput manner.
Overall Design: The overall design consists of RNA sequencing in bulk and in single K562 cells. As a control, we performed single-cell RNA sequencing of K562 cells expressing dCas9-KRAB and a control sgRNA targeting the non-expressed HSBP1 gene in two biological replicates. As a pilot project, we performed single cell RNA-Seq of dCas9-KRAB K562 cells after pooled infection of a library of 10 sgRNA viruses targeting promoters and enhancers in the beta-globin locus. As controls for this experiment, we individually infected these 10 sgRNAs and either performed 1) bulk RNA sequencing or 2) single cell RNA sequencing after pooling the separately infected cells. Finally, we scaled this single-cell approach to measure transcriptome changes for a library of 241 sgRNAs spanning 71 hypersensitive sites from 15 super-enhancers in K562 cells.
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| Growth Protocol: | K562 were cultured in IMDM plus 10% FBS and pen/strep at 37C and 5% CO2. |
| Treatment Protocol: | HEK293T cells were cultured in DMEM with 10% FBS and pen/strep. For lentiviral packaging, 3X106 293T cells were seeded in a 6 cm dish one day before transfection. The indicated viral plasmid(s) were co-transfected with lentivirus packaging plasmids pMD2.G and psPAX2 (Addgene ID 12259 and 12260) with 4:2:3 ratio by using Lipofectamine 3000 (Thermo Fisher) according to the manufacturer's protocol. Twelve hours after transfection, media was changed to fresh DMEM with 10% FBS plus Pen/Strep. Seventy-two hours after transfection, virus-containing media was collected, passed through a 45 um filter, and aliquoted into 1.5ml tubes. Viruses were stored in -80掳C before infection or titration. For virus infection, 2X105 K562 cells were seeded in 24 well plate per well with 500 碌l complete medium plus 1碌g/ml polybrene. Titrated virus aliquot(s) were thawed to room temperature and one virus was added to each well. The plate was then centrifuged at 1000xg at 36 掳C and returned to the incubator. The following day, the media was changed to fresh complete medium with antibiotics to screen for infected cells. Cells were kept at ~30% confluence during antibiotic selection. One batch of cells were treated with TNF-alpha for 1 hour. Immediately prior to library construction, the TNF-alpha treated cells (labeled with sgRNA64) and mock treated cells (labeled with sgRNA63) were combined to a single tube in PBS/BSA. |
| Extract Protocol: | Single cell RNA sequencing was performed using the Drop-Seq method. Briefly, single cells, polyA-containing barcoded beads (ChemGenes), and droplet generation oil (Bio-Rad) were each flowed into individual input ports on a microfluidic device (NanoShift). Cells in droplets were lysed and hybridized to beads. Beads were isolated and subjected to reverse transcription (Thermo Fisher) and exonuclease I (NEB) treatment, followed by PCR of full length transcripts (Kapa). Final libraries were created by Tn5-mediated tagmentation of cDNA, and amplified by PCR (Kapa) and purified by SPRI beads. |
| Library Construction Protocol: | - |
| Molecule Type: | poly(A)+ RNA |
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| Library Layout: | PAIRED |
| Library Strand: | Forward |
| Platform: | ILLUMINA |
| Instrument Model: | Illumina NextSeq 550 |
| Strand-Specific: | Specific |
| Data Resource | GEN Sample ID | GEN Dataset ID | Project ID | BioProject ID | Sample ID | Sample Name | BioSample ID | Sample Accession | Experiment Accession | Release Date | Submission Date | Update Date | Species | Race | Ethnicity | Age | Age Unit | Gender | Source Name | Tissue | Cell Type | Cell Subtype | Cell Line | Disease | Disease State | Development Stage | Mutation | Phenotype | Case Detail | Control Detail | Growth Protocol | Treatment Protocol | Extract Protocol | Library Construction Protocol | Molecule Type | Library Layout | Strand-Specific | Library Strand | Spike-In | Strategy | Platform | Instrument Model | Cell Number | Reads Number | Gbases | AvgSpotLen1 | AvgSpotLen2 | Uniq Mapping Rate | Multiple Mapping Rate | Coverage Rate |
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