immunofluorescence staining and high-resolution confocal microscopy of crispr/cas9-mediated cenp-e knockout hela cells

Centromere-Associated Protein-E Gene Editing Using the CRISPR/Cas9 System

Engineered genome editing mediates the targeted modifications of genes in a variety of cells and organisms. In eukaryotes, site-specific mutagenesis can be introduced by the applications of sequence-specific nucleases that stimulate homologous recombination of target DNA1. In recent years, several genome editing technologies, including zinc finger nucleases (ZFNs)2,3, transcription activator-like effector nucleases (TALENs)4,5, and homing meganucleases6,7, have been engineered to cleave genomes at specific sites, but these approaches require complex protein engineering and redundant experimental procedures. Studies have shown that the type II prokaryotic clustered regularly interspaced short palindromic repeats (CRISPR)/Cas system is an efficient gene editing technology, which specifically mediates RNA-guided, site-specific DNA cleavage in a wide variety of cells and species8,9,10,11. The CRISPR/Cas9 gene knockout technology has revolutionized the fields of basic biology, biotechnology, and medicine12.
Bacteria and most archaea have evolved an RNA-based adaptive immune system that uses CRISPR and Cas proteins to identify and destroy viruses and plasmids13. Streptococcus pyogenes Cas9 (SpCas9) endonuclease contains the RuvC-like Holliday junction resolvase (RuvC) and His-Asn-His (HNH) domain, which can efficiently mediate sequence-specific, double-stranded breaks (DSBs) by providing a synthetic single-guide RNA (sgRNA) containing CRISPR RNAs (crRNA) and trans-activating crRNA (tracrRNA)14,15,16. DSBs can be repaired through the indel-forming non-homologous end joining (NHEJ) or homology-directed repair (HDR) pathway, which introduces multiple mutations, including insertions, deletions, or scar-less single nucleotide substitutions, in mammalian cells1,8. Both the error-prone NHEJ and the high-fidelity HDR pathway can be used to mediate gene knockout through insertions or deletions, which can cause frameshift mutations and premature stop codons10.
Kinesin-7 CENP-E is required for kinetochore-microtubule attachment and chromosome alignment during cell division17,18,19. Antibody microinjection20,21, siRNA depletion22,23, chemical inhibition24,25,26, and genetic deletion27,28,29 of CENP-E leads to chromosome misalignment, the activation of spindle assembly checkpoint and mitotic defects, which results in aneuploidy and chromosomal instability19,30. In mice, CENP-E deletion results in abnormal development and embryonic lethality at the very early stages of development27,29,31. Genetic deletion of CENP-E usually leads to chromosome misalignment and cell death26,27,29, which is an obstacle in studying the functions and mechanisms of the CENP-E proteins.
A recent study has established a conditional CENP-E knockout cell line using an Auxin-inducible CRISPR/Cas9 gene-editing method32, which enables rapid degradation of CENP-E proteins in a relatively short time33. However, to date, stable CENP-E knockout cell lines have not been established, which is an unresolved technical challenge in CENP-E biology. Considering genetic robustness34, genetic compensation responses35,36,37, and complex intracellular environments, as the direct consequences of complete deletion of CENP-E may be complex and unpredictable, it is important to establish CENP-E knockout cell lines for the investigation of mechanisms of chromosome alignment, spindle assembly checkpoint, and downstream signaling pathways.
The discovery and applications of CENP-E inhibitors are important for cancer treatment. To date, seven types of CENP-E inhibitors have been found and synthesized, including GSK923295 and its derivatives24,25, PF-277138,39, imidazo[1,2-a]pyridine scaffold derivatives40,41, compound-A42,43, syntelin44,45, UA6278446, and benzo[d]pyrrolo[2,1-b]thiazole derivatives47. Among these inhibitors, GSK923295 is an allosteric and efficient CENP-E inhibitor that binds to the motor domain of CENP-E and inhibits CENP-E microtubule-stimulated ATPase activity with a Ki of 3.2 &#177; 0.2 nM24,25. However, compared with the inhibitory effects of GSK923295 on cultured cancer cells, the therapeutic effects of GSK923295 in clinical cancer patients are not ideal48,49, which also raised concerns about the specificity of GSK923295 for CENP-E. Moreover, the specificity and side effects of other CENP-E inhibitors on the CENP-E proteins are key issues in cancer research.
In this study, we have completely knocked out the CENP-E gene in HeLa cells using the CRISPR/Cas9 system. Three optimized phenotype-based screening strategies have been established, including cell colony screening, chromosome alignment phenotypes, and the fluorescent intensities of CENP-E proteins, to improve the screening efficiency and success rate of CENP-E gene editing. Furthermore, CENP-E knockout cell lines can be used to test the specificity of candidate compounds for CENP-E.

Author Spotlight: Establishing &lt;em&gt;CENP-E&lt;/em&gt; Knockout HeLa Cells &amp;#8211; A Novel Approach to Study Kinesin-7 &lt;em&gt;CENP-E&lt;/em&gt; Biology and its Inhibitors

Generation of Centromere-Associated Protein-E CENP-E-/- Knockout Cell Lines using the CRISPR/Cas9 System

Genetic deletion of Kinesin-7 and CENP usually results in cell cycle arrest and cell death. The construction of stable CENP knockout cell lines is an important unresolved issue in CENP biology. In this study, we generated CENP knockout HeLa cells using a CRISPR/Cas9 system, and established three optimized screening strategies.Recently, several genome editing technologies, including zinc-finger nucleases, transcription activator-like effector nucleases, and how we make our nucleases, has been engineered to cleave genomes at a specific size. The CRISPR/Cas9 gene knockout technology has revolutionized basic biology, biotechnology, and medicine. CENP is essential for attaching kinetochores to microtubules and aligning chromosomes.Disrupting CENP, whether through antibody microinjection, sgRNA deletion, chemical inhibition, or genetic deletion, result in chromosome misalignment, mitotic defects, and often cell death, complicating the study of CENP protein mechanisms. In this study, three optimized phenotype-based screening strategies were established, including cell colony screening, chromosome alignment of phenotypes, and the fluorescent intensities of CENP proteins, which improved the screening efficiency and the experimental success rate. Importantly, CENP deletion results in chromosome misalignment, the abnormal location of BubR1 proteins, and mitotic defects.The interaction modes and the molecular mechanisms of CENP and its inhibitors are important research fields in cell biology and cancer research. In this study, the CENP knockout HeLa cell line has been established as a valuable tool for the validation of the specificity and the toxicity of CENP inhibitors.

Immunofluorescence Staining and High-Resolution Confocal Microscopy of CRISPR/Cas9-Mediated CENP-E Knockout HeLa Cells

To begin, take a plate of wild type and CENP-E mutant HeLa cells growing on a cover slip. Fix the cells with 4%paraformaldehyde and PBS fixative solution at room temperature for 10 minutes. Then, immerse in PBS for two rounds of five minutes each.Next, permeabilize the cells with 0.25%Triton X-100 and PBS at room temperature for 10 minutes. Immerse them in PBS for two rounds of five minutes each. Proceed to block the cells with 1%BSA PBS with 0.1%Tween 20 at room temperature for one hour.Dilute the primary antibodies in 1%BSA and PBST and incubate the samples at four degrees Celsius for 12 hours. Discard the primary antibody solutions. Then, rinse the cells three times for five minutes each with PBS.Add diluted secondary antibodies to the cell and incubate at room temperature for two hours. Next, discard the secondary antibodies. Then rinse the cells with PBS three times for five minutes each.Stain the nuclei using DAPI at room temperature for five minutes. Mount the slides with the mounting medium and seal them with nail polish. Observe the fluorescence images using a scanning confocal microscope, fitted with a 63 times magnification, 1.40 numerical aperture objective, and record them for further analysis.Immunofluorescence staining of the control and CENP-E mutant groups showed that the fluorescence intensities of the CENP-E proteins were completely knocked out in the CENP-E mutant Clone 1 cells and significantly decreased in CENP-E mutant Clone 3 cells. The ratios of metaphase cells with chromosome misalignment increased in Clones 1 and 3 compared to the control cells. Meanwhile, the ratios of metaphase cells increased significantly in Clone 1 cells and Clone 3 cells.In addition, the ratio of interphase cells slightly increased in Clone 1 and 3 groups after CENP-E deletion, compared with the control group. The rates of prophase, anaphase, and telophase cells were slightly decreased after CENP-E deletion, whereas the rates of metaphase cells increased after CENP-E deletion.

immunofluorescence-staining-high-resolution-confocal-microscopy

Research

JoVE Journal

Biology

53 vistas.  Fujian Medical University. Para empezar, tome una placa de células HeLa de tipo salvaje y mutantes CENP-E que crecen en un cubreobjetos. Fije las células con paraformaldehído al 4% y solución fijadora de PBS a temperatura ambiente durante 10 minutos. Luego, sumérgete en PBS durante dos rondas de cinco minutos cada una.A continuación, permeabilice las células con Triton X-100 al 0,25% y PBS a temperatura ambiente durante 10 minutos. Sumérgelos en PBS durante dos rondas de cinco minutos cada una. Proceda a...