Overview
In this video, we demonstrate all-in-one CRISPR-Cas9 based genome editing in cultured cells where Cas9 and sgRNA are provided as a single plasmid construct to the cells. The CRISPR-Cas9 system and desired gene to be inserted was introduced in cells through electroporation technique to facilitate successful gene editing.
Protocol
1. Electroporation of Macrophage and T Cell Lines
- Prepare cell cultures for electroporation
- Prepare Roswell Park Memorial Institute (RPMI) 1640 supplemented with 10% fetal bovine serum (FBS) as complete growth medium for Jurkat T cells. Prepare Dulbecco's Modified Eagle Medium (DMEM) with 10% FBS for culturing RAW264.7 macrophages. Supplement all complete growth media with 100 U/mL penicillin and 100 µg/mL streptomycin (Pen/Strep) except for media used for post-transfection incubation before cell sorting.
- Perform subculturing of RAW264.7 and Jurkat T cells according to the supplier's instructions (See Table of Materials). When subculturing RAW264.7 cells, use trypsin-EDTA solution (0.25%) to detach cells. Use FBS supplemented with 10% (v/v) DMSO as a cryopreservation medium for RAW264.7 and Jurkat cells.
- Collect cells at 250 × g for 5 min for RAW264.7 macrophages and 90 × g for 8 min for Jurkat T cells. Then wash with 5-10 mL of 1× DPBS (without Ca2+ or Mg2+ ions). Remove the DPBS.
- Resuspend the cell pellet using 2 mL of 1× DPBS. Use 10 µL of cells and mix with an equal volume of 0.2% trypan blue to estimate the cell count and viability.
NOTE: Ensure that the cell culture has >90% viability on the day of transfection. - For a single knock-in experiment, perform electroporation with 10 µL nucleofection tips with five repetitions. Calculate the volume needed for 2.0 × 106 cells and pellet the cells by centrifugation. Wash the cell pellet again with 1× DPBS as described in step 1.1.2.
NOTE: When using 10 µL nucleofection tips, 4.0 × 105 cells are needed per electroporation. Accordingly, prepare at least 2.0 × 106 cells for one knock-in experiment. - Prepare a 24-well plate with 0.5 mL of complete growth medium (prepared in step 1.1.1) per well without Pen/Strep and prewarm in a 37 °C incubator.
2. Electroporation of CRISPR/Cas9 components and the targeting vector
- Turn on the electroporation system. Use electroporation parameters optimized as follows: 1,400 V/20 ms/2 pulses for RAW264.7 macrophages and 1350 V/20 ms/2 pulses for Jurkat T cells.
- Accounting for sample loss due to pipetting, prepare a 55 µL electroporation mixture in a sterile 1.5 mL microcentrifuge tube containing 2.5 µg of each CRISPR/Cas9 vector (pDsR-mR26-sg1 and pDsR-mR26-sg2 for mRosa26 locus knock-in, and pDsR-hR26-sg1 and pDsR-hR26-sg2 for the hROSA26 locus), 2.4 µg of the linearized targeting vector (pKR26-POI-iBFP or pKhR26-POI-iBFP for mRosa26 and hROSA26 knock-in, linearized by EcoRI or BamHI), and the Resuspension Buffer R.
NOTE: To save time, the electroporation mixture can be prepared during centrifugation (step 1.1.5). - Resuspend 2.0 × 106 cells (prepared in step 1.1.5) in the 55 µL electroporation mixture from step 1.2.2.
- Aspirate the cell/electroporation mixture from step 1.2.3 using a 10 µL nucleofection tip with a pipette.
NOTE: During pipetting, avoid introducing air bubbles, which may cause electroporation failure. - Add the sample to a tube filled with 3 mL of Buffer E from the electroporation kit.
- Apply the electroporation parameters for the two cell types as described in step 1.2.1.
- Transfer the sample into one well of the 24-well plate with prewarmed medium from step 1.1.6.
- Repeat steps 1.2.4-1.2.7 for the other four repetitions as well as for the targeting vector only and CRISPR expression vector only controls.
NOTE: Change the nucleofection tip and tube when switching to a different cell type/plasmid DNA. - Culture the transfected cells for 48-72 h to allow for recovery after electroporation and expression of CRISPR/Cas9 components prior to flow cytometry analysis or fluorescence-activated cell sorting (FACS).
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Materials
Name | Company | Catalog Number | Comments |
Ampicillin, sodium salt | MP Biomedicals | 194526 | |
Cellometer Mini Automated Cell Counter | Nexcelom Bioscience | ||
DPBS (10X), no calcium, no magnesium | ThermoFisher Scientific | 14200075 | |
Dulbecco's Modified Eagle Medium (DMEM) with high glucose | HyClone | SH30022.01 | |
Falcon 5 ml polystyrene round bottom test tube | BD Biosciences | 352003 | |
Fetal bovine serum (FBS) | ThermoFisher Scientific | 10099141 | |
Jurkat | ATCC | TIB-152 | https://www.atcc.org/ |
Kanamycin sulfate | MP Biomedicals | 194531 | |
Multi-channel Pipette (30-300 μL) | Eppendorf, or similar | ||
Neon Transfection System | ThermoFisher Scientific | MPK5000 | |
Neon Transfection System, 10 μL kit | ThermoFisher Scientific | MPK1096 | |
Nunc 15 mL Conical Sterile Centrifuge Tubes | ThermoFisher Scientific | 339651 | |
Pipette tip 0.1-20µl | Eppendorf, or similar | 0030 075.005 | |
Pipette tip 2-200µl | Eppendorf, or similar | 0030 075.021 | |
Pipette tip 50-1000µl | Eppendorf, or similar | 0030 075.064 | |
pX458-DsRed2 | Addgene | 112219 | |
RAW264.7 | ATCC | TIB-71 | https://www.atcc.org/ |
RPMI 1640 Medium | HyClone | SH30027.01 | |
Penicillin-Streptomycin | ThermoFisher Scientific | 15140122 | |
Trypan Blue Solution, 0.4% | ThermoFisher Scientific | 15250061 | |
1.5 mL microtubes, PCR-clean | Eppendorf, or similar | 0030 125.215 | |
24-well Clear TC-treated Multiple Well Plates | Corning | 3524 |