Investigation of the Transcriptional Role of a RUNX1 Intronic Silencer by CRISPR/Cas9 Ribonucleoprotein in Acute Myeloid Leukemia Cells
September 1st, 2019
6.7K views
Direct delivery of preassembled Cas9/guide RNA ribonucleoprotein complexes is a fast and efficient means for genome editing in hematopoietic cells. Here, we utilize this approach to delete a RUNX1 intronic silencer and examine the transcriptional responses in OCI-AML3 leukemic cells.
Overview
This study demonstrates a protocol for genome editing in hematopoietic cells using preassembled Cas9/guide RNA ribonucleoprotein complexes. The focus is on deleting a RUNX1 intronic silencer and assessing the transcriptional responses in OCI-AML3 leukemic cells.
Key Study Components
Area of Science
- Genome Editing
- Hematopoietic Cell Biology
- Leukemia Research
Background
- Cis-regulatory elements are crucial for gene expression.
- Traditional methods for studying these elements are often complex and time-consuming.
- CRISPR technology offers a streamlined approach to investigate gene regulation.
- Electroporation enhances the delivery of CRISPR components into difficult-to-transfect cells.
Purpose of Study
- To utilize CRISPR for examining the role of a RUNX1 intronic silencer.
- To improve editing efficiency and cell viability in hematopoietic cells.
- To provide a simple protocol for fast assessments of gene regulatory functions.
Methods Used
- Designing CRISPR RNAs flanking the target cis-regulatory element.
- Electroporating preassembled Cas9/gRNA complexes into OCI-AML3 cells.
- Using fragment analysis for screening mutant clones.
- Performing real-time PCR for transcript quantification.
Main Results
- The RUNX1 intronic silencer was successfully deleted.
- Capillary gel electrophoresis confirmed the deletion.
- Mutant levels greater than 95% were achieved in selected clones.
- Transcriptional responses were assessed post-deletion.
Conclusions
- This protocol provides an efficient method for genome editing in hematopoietic cells.
- It allows for rapid evaluation of gene regulatory elements in their endogenous context.
- The approach minimizes off-target effects and enhances cell viability.
Frequently Asked Questions
What is the main advantage of using CRISPR in this study?
CRISPR allows for precise editing of the RUNX1 intronic silencer with improved efficiency and reduced off-target effects.
How does electroporation improve the delivery of CRISPR components?
Electroporation enhances the uptake of the Cas9/gRNA complexes into hematopoietic cells, which are typically hard to transfect.
What are the expected sizes of the PCR products?
The wild-type PCR product is approximately 500 base pairs, while the mutant product is about 230 base pairs.
How is the success of the gene editing confirmed?
Success is confirmed through capillary gel electrophoresis and analysis of mutant levels.
What is the significance of the RUNX1 gene in leukemia?
RUNX1 is a critical regulator of hematopoiesis, and its dysregulation is often implicated in leukemia.
Can this protocol be applied to other genes?
Yes, the protocol can be adapted for editing other cis-regulatory elements in different genes.
Executive Industry Relevance
Understanding cis-regulatory elements such as silencers is critical for de-risking target validation in oncology drug discovery. This CRISPR-based approach enables rapid, endogenous interrogation of gene repression mechanisms in hematopoietic models, supporting mechanistic insights that inform early-stage therapeutic hypothesis testing. The method addresses a key bottleneck in studying non-coding regulatory variants linked to leukemia and other malignancies.
Strategic Applications in Biopharma R&D
Early Discovery & Target Validation
- Scientific Value: Enables functional validation of non-coding regulatory elements like silencers that modulate oncogene or tumor suppressor expression.
- Operational Value: Uses plasmid- and virus-free RNP delivery to overcome transfection challenges in primary and leukemic hematopoietic cells.
- Predictive Value: Supports assessment of silencer impact on alternative promoter-driven isoforms, informing isoform-specific target strategies.
Screening & Assay Development
- Scientific Value: Fragment analysis allows high-throughput screening of clonal deletions with quantitative estimation of editing efficiency.
- Operational Value: Electroporation of preassembled RNPs improves editing efficiency and viability while reducing off-target risks in sensitive blood-derived lines.
- Assay Readiness: Enables generation of isogenic clonal models for downstream functional and phenotypic screening workflows.
Translational & Preclinical Research
- Scientific Value: Links silencer deletion to transcriptional changes in RUNX1 isoforms, providing insight into regulatory mechanisms relevant to leukemogenesis.
- Operational Value: Real-time PCR with isoform-specific probes enables precise quantification of promoter-dependent transcriptional responses.
- Translational Continuity: Supports biomarker-aligned studies by connecting non-coding variant effects to gene expression outputs in disease-relevant cells.
Pipeline & Workflow Integration
This method fits within the discovery-to-preclinical continuum by enabling early functional annotation of non-coding variants, which can inform target selection and lead optimization decisions in hematologic malignancies.
- Discovery Biology: Facilitates hypothesis-driven interrogation of silencer elements to clarify repressive mechanisms in gene regulatory networks.
- Screening: Generates validated clonal models with >95% editing efficiency for use in compound sensitivity or phenotypic assays.
- Analytics: Provides quantitative transcript measurements via qPCR to assess dose-dependent or time-dependent regulatory effects.
- Translational Research: Connects non-coding edits to mRNA isoform changes, supporting mechanistic de-risking before preclinical investment.
- Enterprise Reuse: The CRISPR-RNP/fragment analysis/qPCR workflow is adaptable to other CREs and genes, promoting platform-level standardization.
Operational & Enterprise Impact
- Scientific Value: Reduces mechanistic ambiguity in non-coding gene regulation, improving confidence in target-disease linkages.
- Operational Value: Standardized, reproducible workflow for editing hard-to-transfect hematopoietic cells using electroporation-delivered RNPs.
- Strategic Value: Enables faster go/no-go decisions by providing early functional evidence of regulatory element impact on oncogenic pathways.
- Portfolio Impact: Supports risk-adjusted prioritization of targets based on validated cis-regulatory function in disease-relevant models.
Implementation Considerations
- Requires expertise in CRISPR design, RNP complex formation, and electroporation optimization for hematopoietic systems.
- Depends on access to capillary electrophoresis or fragment analysis tools for clonal screening and validation.
- Necessitates molecular biology resources for RNA extraction, cDNA synthesis, and TaqMan-based qPCR assay development.
- Must account for potential indel variability at cut sites when interpreting clonal heterogeneity and editing outcomes.
- Adaptation to other cell types may require optimization of electroporation conditions and RNP concentrations.
Biopharma FAQs
Why is deletion of a RUNX1 intronic silencer important for target validation in AML?
Deleting the silencer allows assessment of its repressive effect on RUNX1 isoform expression, which is critical for understanding transcriptional dysregulation in leukemia. This functional validation supports target confidence by linking non-coding elements to gene output in a disease-relevant model.
How does isolating the silencer as an independent variable improve discovery pipeline efficiency?
By using CRISPR to delete only the intronic silencer while preserving the endogenous RUNX1 locus, the study isolates its specific transcriptional impact. This enables clear cause-effect interpretation without confounding effects from overexpression or artificial reporter systems.
What quantitative measurements enable assessment of silencer function post-deletion?
Real-time qPCR with isoform-specific primers and probes quantifies changes in RUNX1a, RUNX1b, and RUNX1c transcripts. Normalization to housekeeping genes allows precise comparison of promoter-dependent expression across edited and wild-type clones.
Why are replication and clonal validation required for cross-functional collaboration in target validation?
Selecting clones with >95% deletion efficiency and confirming edits via capillary electrophoresis ensures genetic consistency across experiments. This reproducibility allows screening, chemistry, and biology teams to rely on isogenic models for downstream assays.
What statistical and analytical capabilities are needed before implementing this CRE editing approach?
Teams require fragment analysis tools to quantify editing efficiency and qPCR platforms for transcript quantification. Basic statistical comparison of normalized copy numbers between control and edited groups is sufficient to assess significant transcriptional changes.
Chapters in this video
0:04
Title
1:16
crRNA Design and Preparation of Cas9/gRNA RNP Complexes
2:16
Electroporation of RNP Complexes into OCI-AML3 Cells
3:12
Screening and Selection of Cell Clones with Biallelic Deletions
5:51
Functional Analyses of Silencer Deletions with Real-time Quantitative RT-PCR
7:18
Results: RUNX1 Intronic Silencer Deletion
8:16
Conclusion
