Generation of Genomic Deletions in Mammalian Cell Lines via CRISPR/Cas9
January 3rd, 2015
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CRISPR/Cas9 is a robust system to produce disruption of genes and genetic elements. Here we describe a protocol for the efficient creation of genomic deletions in mammalian cell lines using CRISPR/Cas9.
Overview
This article describes a protocol for creating genomic deletions in mammalian cell lines using the CRISPR/Cas9 system. The method focuses on producing loss-of-function mutations through large deletions, which are more informative for studying genes and genetic elements.
Key Study Components
Area of Science
- Genetics
- Molecular Biology
- Cell Biology
Background
- CRISPR/Cas9 is a powerful tool for gene editing.
- Large deletions can provide clearer insights into gene function compared to smaller mutations.
- The method aims to simplify the screening process for deletion alleles.
- Electroporation is used to introduce CRISPR constructs into cells.
Purpose of Study
- To establish a reliable method for generating genomic deletions in mammalian cells.
- To enhance the efficiency of screening for deletion clones.
- To facilitate the study of gene function through loss-of-function mutations.
Methods Used
- Electroporation of CRISPR plasmids and a GFP reporter into mammalian cells.
- Fluorescence-activated cell sorting (FACS) to isolate GFP-positive cells.
- Limiting dilution to obtain single-cell clones.
- Conventional PCR to screen for deletion alleles.
Main Results
- Successful generation of bi-allelic deletion clones.
- Identification of deletion and non-deletion bands through PCR.
- Confirmation of gene expression loss in deletion clones.
- Demonstration of the method's efficiency and cost-effectiveness.
Conclusions
- The CRISPR/Cas9 system is effective for creating large genomic deletions.
- This method streamlines the process of generating and screening deletion alleles.
- It provides a valuable approach for studying gene function and non-coding elements.
Frequently Asked Questions
What is the main advantage of using CRISPR/Cas9 for gene editing?
CRISPR/Cas9 allows for precise and efficient editing of genes, enabling the creation of large deletions that can provide clearer insights into gene function.
How does fluorescence-activated cell sorting (FACS) contribute to this method?
FACS is used to isolate the top 3% of GFP-positive cells, enriching for those that have successfully taken up the CRISPR constructs.
What are the key steps in the protocol?
The protocol involves electroporation, FACS sorting, limiting dilution, and PCR screening for deletion alleles.
How long does it take to complete this method?
Once mastered, the entire process can be completed in a matter of weeks.
What types of mutations can be generated using this method?
The method primarily generates loss-of-function mutations through large genomic deletions.
Can this method be applied to other cell types?
Yes, the CRISPR/Cas9 system can be adapted for various mammalian cell lines.
Executive Industry Relevance
CRISPR/Cas9-mediated genomic deletion enables efficient loss-of-function studies in mammalian cell lines, offering predictive confidence in target validation by reducing mechanistic ambiguity. Large deletions provide clearer phenotypic readouts than small indels, supporting early discovery decisions and portfolio triage. This approach accelerates target de-risking by delivering biallelic modifications that are easily screened via conventional PCR.
Strategic Applications in Biopharma R&D
Early Discovery & Target Validation
- Scientific Value: Enables interrogation of therapeutic hypotheses through predictable loss-of-function alleles.
- Operational Value: Simplifies screening via PCR detection of deletion bands, reducing labor and cost.
- Predictive Value: Supports target confidence by ensuring complete gene disruption for functional analysis.
Screening & Assay Development
- Scientific Value: Generates isogenic deletion clones for reproducible compound screening assays.
- Operational Value: Uses FACS enrichment and limiting dilution to scale clonal isolation.
- Assay Readiness: Produces validated cell lines suitable for high-throughput phenotypic screening.
Translational & Preclinical Research
- Translational Value: Facilitates study of non-coding genetic elements with defined genomic boundaries.
- Preclinical Model: Enables isoform-specific disruption to assess target mechanism in disease-relevant systems.
- Risk Mitigation: Reduces false positives from off-target effects via multiple non-overlapping sgRNA pairs.
Pipeline & Workflow Integration
The method fits within the discovery continuum from target validation to lead identification, providing genetically engineered models for downstream screening and mechanistic follow-up.
- Discovery Biology: Supports hypothesis testing by creating defined genomic deletions that clarify gene function.
- Screening: Delivers assay-ready clonal lines with validated genotypes for compound evaluation.
- Analytics: Enables quantitative PCR and Sanger sequencing to confirm zygosity and breakpoint precision.
- Translational Research: Connects to biomarker studies by allowing deletion of regulatory regions or non-coding loci.
- Enterprise Reuse: Establishes a scalable platform for generating deletion alleles across multiple targets and cell lines.
Operational & Enterprise Impact
- Scientific Value: Predictive confidence in target validation through biallelic loss-of-function.
- Operational Value: Standardized workflow using electroporation, FACS, and PCR for reproducible results.
- Strategic Value: Improves go/no-go decisions by reducing biological ambiguity in target modulation.
- Portfolio Impact: Enables risk-adjusted prioritization via reliable functional genomics data.
Implementation Considerations
- Requires molecular cloning expertise for sgRNA design and plasmid construction.
- Depends on electroporation and FACS infrastructure for efficient delivery and enrichment.
- Necessitates PCR optimization and gel electrophoresis for deletion screening.
- Involves clonal expansion and validation steps to confirm biallelic modification.
- Benefits from using multiple sgRNA pairs to control for off-target effects and isoform-specific disruption.
Biopharma FAQs
Why does biallelic deletion improve target validation confidence?
Biallelic deletion ensures complete loss of gene function, reducing phenotypic variability and increasing confidence in target mechanism. This approach avoids confounding effects from monoallelic or partial disruption. It supports more reliable interpretation of screening and mechanistic data.
How does FACS enrichment of GFP-positive cells improve screening efficiency?
FACS isolates the top 3% of GFP-expressing cells, enriching for those with high CRISPR construct delivery. This increases the likelihood of obtaining deletion-positive clones. It reduces the number of wells needed for clonal screening, saving time and resources.
What enables rapid identification of deletion clones via conventional PCR?
Large deletions produce a predictable size shift in PCR amplicons, allowing clear distinction between deletion and non-deletion bands on agarose gel. This eliminates the need for sequencing every clone during initial screening. The method is cost-effective and accessible in standard molecular biology labs.
Why are replication requirements important for cross-functional collaboration?
Replication across multiple sgRNA pairs and clonal isolates ensures that observed phenotypes are due to the intended deletion and not off-target effects. This builds confidence in data shared between discovery, preclinical, and translational teams. It supports consistent decision-making in target advancement.
What statistical analysis is needed before implementing deletion screening at scale?
Teams should assess cloning efficiency, deletion frequency, and PCR signal-to-noise ratio to set quality thresholds. Analysis of replicate experiments helps define acceptable ranges for biallelic, monoallelic, and non-deletion outcomes. This informs go/no-go criteria for clone selection and downstream use.
Chapters in this video
0:05
Title
1:22
Transfecting CRISPRs into MEL Cells
2:35
Fluorescence Activated Cell Sorting of Transfected Cells
3:41
Primer Validation and Screening Bulk Cultures for CRISPR/Cas9-Mediated Deletion
5:26
Screening CRISPR/Cas9 Clones for Deletions and Clone Selection
7:10
Results: Deletion of Pim1 in MEL Cells
9:00
Conclusion
