CD Biosynsis offers high-precision CHO (Chinese Hamster Ovary) Cells Gene Knock-in Services, enabling the stable, accurate integration of large expression cassettes and therapeutic genes into the host genome. CHO cells are the industry standard for producing complex biotherapeutics, monoclonal antibodies (mAbs), and recombinant proteins. Gene knock-in is a critical step in cell line development, utilized to achieve stable, high-level expression by inserting the gene of interest (GOI) at defined genomic safe harbor loci. Leveraging the precision of CRISPR-Cas9 to induce double-strand breaks (DSBs), our services rely on the cell's Homology-Directed Repair (HDR) pathway to integrate the desired DNA fragment accurately. We provide end-to-end solutions, from multi-gene cassette design to final clone screening, accelerating the development of superior CHO cell lines with enhanced titer, stability, and product quality.
Get a QuoteGene knock-in in CHO cells is designed to move beyond the instability and silencing issues associated with traditional random plasmid integration. Our strategy utilizes CRISPR-Cas9 to precisely cut a pre-selected genomic safe harbor locus (e.g., highly expressed or neutral sites). The cell then uses the provided large DNA donor template via the Homology-Directed Repair (HDR) pathway to integrate the gene of interest (e.g., mAb heavy and light chains) accurately. This ensures stable expression and eliminates the risk of position effects and transcriptional silencing, which is paramount for regulatory approval and commercial manufacturing stability.
Safe Harbor Targeting
Identification of optimal genomic safe harbor loci (e.g., highly transcribed genes or neutral sites) for integration, ensuring stable expression without disrupting essential host genes.
Large Donor Template Design
Design of large DNA repair templates (up to 10kb) with optimal promoter/enhancer elements and selection markers, flanked by long homology arms (HDR templates) to maximize integration rate.
Multi-Gene Cassette Insertion
Strategy for the single-step integration of multiple expression units (e.g., mAb heavy and light chains linked by a P2A sequence) to ensure balanced expression.
RNP Delivery System
Preference for Ribonucleoprotein (RNP) complexes (Cas9 protein + gRNA) for transient, high-efficiency, and low off-target delivery into CHO cells via electroporation.
High-Fidelity Cas9 Variants
Use of specialized Cas9 variants (e.g., Cas9-HF1) to further minimize off-target cleavage events, maintaining the integrity of the complex CHO genome.
Marker Selection System
Integration of selection markers (e.g., Puromycin, or DHFR/GS markers) into the donor cassette to enrich for cells that have successfully undergone the HDR-mediated knock-in event.
MAb Expression Cassette KI
Stable integration of genes encoding complex therapeutic proteins (e.g., bispecific antibodies) into defined safe harbor loci for consistent and high-level expression.
Glycosylation Pathway Insertion
Accurate knock-in of human glycosylation enzymes (e.g., GNT-V) to modify the host's native glycosylation machinery, ensuring desired product quality attributes.
Metabolic Pathway Integration
Insertion of genes to create new metabolic capabilities (e.g., enhanced nutrient utilization or cofactor regeneration) that boost cell growth and specific productivity (Qp).
A systematic process for achieving precise integration and stable cell line isolation.
1. Rational Design & RNP Preparation
2. Transfection & HDR Integration
3. Single Cell Cloning & Screening
4. Clone Verification & Delivery
Identify the genomic safe harbor or target locus. Design gRNA(s) for the Cas9 cut site.
Prepare the Cas9 enzyme/gRNA Ribonucleoprotein (RNP) complex for transient delivery.
Synthesize the large DNA donor template (up to 10kb) with selection markers and optimal homology arms.
Cotransfect the RNP complex and the large DNA donor into the CHO host cell line.
Culture cells to allow the Homology-Directed Repair (HDR) pathway to integrate the donor precisely.
Apply antibiotic selection or metabolic selection to enrich for stable integration events.
Genotype verification via junction PCR and definitive sequencing of the integration site to confirm precise HDR.
Phenotypic validation of the final clone for titer (Qp), stability over multiple passages, and product quality.
Delivery of the verified CHO master cell bank (MCB) and complete documentation.
Stable Chromosomal Expression
CRISPR-guided HDR integration into defined genomic safe harbor loci guarantees consistent, high-level expression and prevents gene silencing associated with random integration.
Large Fragment Integration
Ability to precisely insert large expression cassettes (up to 10kb or more), enabling the stable integration of multi-subunit proteins or full biosynthetic pathways in a single step.
High Precision HDR
Optimization of RNP delivery and donor template design maximizes the rate of accurate Homology-Directed Repair, minimizing random integration and undesirable indels.
Regulatory Compliance
Targeted integration and comprehensive genomic verification provide the necessary documentation to satisfy regulatory requirements for stable cell line development.
1. Why is stable chromosomal integration preferred over plasmid integration?
Chromosomal integration via HDR ensures the expression cassette is placed at a transcriptionally active site (safe harbor). This prevents gene silencing and plasmid loss, guaranteeing stable and consistent productivity over long culture periods, which is vital for commercial production.
2. What is a "genomic safe harbor" locus?
A genomic safe harbor is a known, non-essential region of the CHO genome that is highly transcribed. Inserting the gene of interest here ensures high-level expression without disrupting vital host cell functions or suffering from position effects.
3. Can you integrate both the heavy and light chains of an mAb simultaneously?
Yes. We integrate both chains in a single cassette, often linked by a self-cleaving peptide (e.g., P2A or F2A), into a safe harbor locus in one step. This ensures equimolar and balanced expression of both subunits, which is critical for antibody assembly.
4. What is the advantage of using RNP delivery for knock-in?
RNP delivery provides transient Cas9 activity, maximizing cutting efficiency while minimizing the lifespan of the Cas9 enzyme in the cell. This significantly reduces the risk of off-target cleavage that could interfere with the HDR process or host cell viability.
5. How is the knock-in verified at the genomic level?
Verification is comprehensive, using junction PCR to confirm successful integration at both the 5' and 3' ends of the targeted locus, followed by Sanger sequencing to confirm the integrity and sequence of the integrated gene cassette.
6. How do you select for cells that have undergone the knock-in?
The donor DNA cassette includes a selectable marker (e.g., antibiotic resistance gene or metabolic marker like DHFR). We apply the corresponding selection agent to enrich the cell population that has successfully integrated the entire expression cassette.
7. What is the role of the homology arms on the donor template?
Homology arms are DNA sequences (typically 500-1000 bp long) that match the genomic sequence flanking the Cas9 cut site. They guide the cell's Homology-Directed Repair (HDR) machinery to accurately integrate the therapeutic gene cassette at the specific target locus.
8. What input is required to start a gene knock-in project?
We require the specific CHO host cell line, the target genomic safe harbor locus (if known), and the full sequence of the expression cassette (including the gene of interest, promoter, and selection marker).
CRISPR-Cas9 technology represents a transformative advancement in gene editing techniques. The main function of the system is to precisely cut DNA sequences by combining guide RNA (gRNA) with the Cas9 protein. This technology became a mainstream genome editing tool quickly after its 2012 introduction because of its efficient, simple and low-cost nature.
The CRISPR gene editing system with its Cas9 version stands as a vital instrument for current biological research. CRISPR technology enables gene knockout (KO) through permanent gene expression blockage achieved by sequence disruption. Various scientific domains including disease modeling and drug screening employ this technology to study gene functions. CRISPR KO technology demonstrates high efficiency and precision but requires confirmation and verification post-implementation because unsatisfactory editing may produce off-target effects or incomplete gene knockouts which impact experimental result reliability. For precise and efficient Gene Editing Services - CD Biosynsis, Biosynsis offers comprehensive solutions tailored to your research needs.
The CRISPR-Cas9 knockout cell line was developed using CRISPR/Cas9 gene editing to allow scientists to remove genes accurately for research on gene function and disease models and pharmaceutical discovery. Genetic research considers this technology essential due to its high efficiency together with simple operation and broad usability.
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CD Biosynsis is a leading customer-focused biotechnology company dedicated to providing high-quality products, comprehensive service packages, and tailored solutions to support and facilitate the applications of synthetic biology in a wide range of areas.