CRISPRi/CRISPRa gene-regulation editing
Materials Required
Principle
CRISPRi and CRISPRa use catalytically inactive Cas9, typically SpCas9 D10A/H840A, as an RNA-guided DNA-binding platform that targets genomic loci through sgRNA complementarity and an adjacent PAM without generating Cas9 nuclease-mediated DNA cleavage. CRISPRi represses transcription by recruiting dCas9 alone or dCas9 fused to repressor domains such as KRAB to promoters or transcription start site regions, while CRISPRa activates transcription by recruiting activation domains such as VP64, VPR, or SAM components to promoter-proximal regions. The primary readout is target-gene expression change, commonly measured by RT-qPCR, RNA-seq, reporter fluorescence, or protein-level assays, and the readout reflects transcriptional repression or activation at the targeted endogenous locus.
MCE has not independently verified the accuracy of these methods. They are for reference only.
Experimental Materials
• Use cultured cells appropriate for the biological question, expression constructs encoding dCas9, dCas9-KRAB, dCas9-VP64, dCas9-VPR, or SAM components, and sgRNA-expression constructs targeting promoter or TSS-proximal regions.
• Use sgRNAs designed near the transcription start site;
• CRISPRi activity is strongest in promoter/TSS-proximal windows, and CRISPRa guide performance depends strongly on guide position and sequence features.
• Use RT-qPCR reagents, RNA-seq library preparation reagents, reporter assays, or protein-detection reagents only when the experimental endpoint requires mRNA, transcriptome-wide, reporter, or protein-level readout.
• Use standard mammalian cell-culture equipment, nucleic-acid delivery equipment suitable for the selected cell type, a quantitative PCR instrument for RT-qPCR readout, sequencing access for RNA-seq or pooled-screen readout, and flow cytometry or fluorescence measurement instruments when reporter-based selection is used.
• Use sgRNAs designed near the transcription start site;
• CRISPRi activity is strongest in promoter/TSS-proximal windows, and CRISPRa guide performance depends strongly on guide position and sequence features.
• Use RT-qPCR reagents, RNA-seq library preparation reagents, reporter assays, or protein-detection reagents only when the experimental endpoint requires mRNA, transcriptome-wide, reporter, or protein-level readout.
• Use standard mammalian cell-culture equipment, nucleic-acid delivery equipment suitable for the selected cell type, a quantitative PCR instrument for RT-qPCR readout, sequencing access for RNA-seq or pooled-screen readout, and flow cytometry or fluorescence measurement instruments when reporter-based selection is used.
Experimental Procedure
• Select a CRISPRi or CRISPRa architecture before sgRNA design: dCas9-KRAB is supported for transcriptional repression, dCas9-VP64 and dCas9-VPR are supported for activation, and SAM uses sgRNAs containing MS2 aptamers with MS2-p65-HSF1 recruitment for stronger activation in reported systems.
• Design multiple sgRNAs per target gene because individual sgRNA activity varies by genomic position, promoter annotation, chromatin context, and guide sequence, and use non-targeting sgRNAs plus sgRNAs against genes with known expected expression effects as controls.
• Prepare cells so that dCas9-effector expression and sgRNA delivery can be assessed before endpoint measurement;
• Published protocols and screens commonly validate perturbation by measuring target mRNA or reporter change after delivery rather than assuming activity from construct presence alone.
• Introduce the dCas9-effector and sgRNA components into the chosen cells using a literature-supported delivery format for that cell system, then allow sufficient time for transcriptional repression or activation before measuring gene expression;
• Published studies used plasmid, lentiviral, or stable-expression formats depending on the experimental design.
• For CRISPRi, target sgRNAs to promoter or TSS-proximal regions when the goal is transcriptional repression, and confirm knockdown by comparing target-gene expression against non-targeting sgRNA controls.
• For CRISPRa, target sgRNAs to promoter-proximal regions and compare activation systems when needed, because VP64, VPR, and SAM differ in architecture and activation strength across loci.
• When multiplexing, deliver multiple sgRNAs only when the study design requires simultaneous regulation of multiple genes or stronger activation of one locus, because multiplexed CRISPRi and CRISPRa have been demonstrated but guide performance remains locus-dependent.
• Measure target-gene regulation relative to non-targeting sgRNA controls and, where possible, include positive-control sgRNAs with previously validated repression or activation behavior in the same cell type or assay format.
• Analyze expression by RT-qPCR for targeted validation, RNA-seq for transcriptome-wide specificity assessment, reporter fluorescence for reporter systems, or sequencing-based sgRNA enrichment/depletion for pooled screens.
• Interpret CRISPRi or CRISPRa results as transcriptional perturbation rather than DNA-sequence editing, because dCas9-based systems are designed to regulate gene expression without nuclease-mediated DNA cleavage.
• Design multiple sgRNAs per target gene because individual sgRNA activity varies by genomic position, promoter annotation, chromatin context, and guide sequence, and use non-targeting sgRNAs plus sgRNAs against genes with known expected expression effects as controls.
• Prepare cells so that dCas9-effector expression and sgRNA delivery can be assessed before endpoint measurement;
• Published protocols and screens commonly validate perturbation by measuring target mRNA or reporter change after delivery rather than assuming activity from construct presence alone.
• Introduce the dCas9-effector and sgRNA components into the chosen cells using a literature-supported delivery format for that cell system, then allow sufficient time for transcriptional repression or activation before measuring gene expression;
• Published studies used plasmid, lentiviral, or stable-expression formats depending on the experimental design.
• For CRISPRi, target sgRNAs to promoter or TSS-proximal regions when the goal is transcriptional repression, and confirm knockdown by comparing target-gene expression against non-targeting sgRNA controls.
• For CRISPRa, target sgRNAs to promoter-proximal regions and compare activation systems when needed, because VP64, VPR, and SAM differ in architecture and activation strength across loci.
• When multiplexing, deliver multiple sgRNAs only when the study design requires simultaneous regulation of multiple genes or stronger activation of one locus, because multiplexed CRISPRi and CRISPRa have been demonstrated but guide performance remains locus-dependent.
• Measure target-gene regulation relative to non-targeting sgRNA controls and, where possible, include positive-control sgRNAs with previously validated repression or activation behavior in the same cell type or assay format.
• Analyze expression by RT-qPCR for targeted validation, RNA-seq for transcriptome-wide specificity assessment, reporter fluorescence for reporter systems, or sequencing-based sgRNA enrichment/depletion for pooled screens.
• Interpret CRISPRi or CRISPRa results as transcriptional perturbation rather than DNA-sequence editing, because dCas9-based systems are designed to regulate gene expression without nuclease-mediated DNA cleavage.
Troubleshooting
Problem: Target-gene repression or activation is weak.
• Possible cause: sgRNA position or sequence is ineffective.• Literature-supported solution: Test multiple sgRNAs near the TSS or promoter-proximal region and prioritize designs supported by CRISPRi/CRISPRa activity rules.
Problem: CRISPRa activation is modest.
• Possible cause: dCas9-VP64 alone may be insufficient at some loci.• Literature-supported solution: Evaluate stronger activation architectures such as SAM or dCas9-VPR when compatible with the experimental system.
Problem: Expression changes are difficult to attribute to the intended target.
• Possible cause: sgRNA-specific or locus-context effects.• Literature-supported solution: Use multiple independent sgRNAs per gene and confirm the phenotype by direct expression measurement of the intended target.
References:
- [1]. Qi LS, et al. Repurposing CRISPR as an RNA-guided platform for sequence-specific control of gene expression. Cell. 2013;152(5):1173-1183. [Content Brief]
- [2]. Gilbert LA, Larson MH, Morsut L, Liu Z, Brar GA, Torres SE, et al. CRISPR-mediated modular RNA-guided regulation of transcription in eukaryotes. Cell. 2013;154(2):442-451. [Content Brief]
- [3]. Gilbert LA, Horlbeck MA, Adamson B, Villalta JE, Chen Y, Whitehead EH, et al. Genome-scale CRISPR-mediated control of gene repression and activation. Cell. 2014;159(3):647-661. [Content Brief]
- [4]. Konermann S, Brigham MD, Trevino AE, Joung J, Abudayyeh OO, Barcena C, et al. Genome-scale transcriptional activation by an engineered CRISPR-Cas9 complex. Nature. 2015;517(7536):583-588. [Content Brief]
- [5]. Chavez A, Scheiman J, Vora S, Pruitt BW, Tuttle M, Iyer EPR, et al. Highly efficient Cas9-mediated transcriptional programming. Nat Methods. 2015;12(4):326-328. [Content Brief]
- [6]. Horlbeck MA, Gilbert LA, Villalta JE, Adamson B, Pak RA, Chen Y, et al. Compact and highly active next-generation libraries for CRISPR-mediated gene repression and activation. eLife. 2016;5:e19760. [Content Brief]
- [7]. Radzisheuskaya A, et al. Optimizing sgRNA position markedly improves the efficiency of CRISPR/dCas9-mediated transcriptional repression. Nucleic Acids Res. 2016;44(18):e141. [Content Brief]
- [8]. Joung J, Konermann S, Gootenberg JS, Abudayyeh OO, Platt RJ, Brigham MD, et al. Genome-scale CRISPR-Cas9 knockout and transcriptional activation screening. Nat Protoc. 2017;12(4):828-863. [Content Brief]
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