Wild-type Cas9 Research Articles

Nucleolus localization of SpyCas9 affects its stability and interferes with host protein translation in mammalian cells

The CRISPR/Cas9 system, originally derived from the prokaryotic adaptive immune system, has been developed as efficient genome editing tools. It enables precise gene manipulation on chromosomal DNA through the specific binding of programmable sgRNA to target DNA, and the Cas9 protein, which has endonuclease activity, will cut a double strand break at specific locus. However, Cas9 is a foreign protein in mammalian cells, and the potential risks associated with its introduction into mammalian cells are not fully understood. In this study, we performed pull-down and mass spectrometry (MS) analysis of Streptococcus pyogenes Cas9 (SpyCas9) interacting proteins in HEK293T cells and showed that the majority of Cas9-associated proteins identified by MS were localized in the nucleolus. Interestingly, we further discovered that the Cas9 protein contains a sequence encoding a nucleolus detention signal (NoDS). Compared with wild-type (WT) Cas9, NoDS-mutated variants of Cas9 (mCas9) are less stable, although their gene editing activity is minimally affected. Overexpression of WT Cas9, but not mCas9, causes general effects on transcription and protein translation in the host cell. Overall, identification of NoDS in Cas9 will improve the understanding of Cas9's biological function in vivo, and the removal of NoDS in Cas9 may enhance its safety for future clinical use.

Massively parallel kinetic profiling of natural and engineered CRISPR nucleases.

Engineered SpCas9s and AsCas12a cleave fewer off-target genomic sites than wild-type (wt) Cas9. However, understanding their fidelity, mechanisms and cleavage outcomes requires systematic profiling across mispaired target DNAs. Here we describe NucleaSeq-nuclease digestion and deep sequencing-a massively parallel platform that measures the cleavage kinetics and time-resolved cleavage products for over 10,000 targets containing mismatches, insertions and deletions relative to the guide RNA. Combining cleavage rates and binding specificities on the same target libraries, we benchmarked five SpCas9 variants and AsCas12a. A biophysical model built from these data sets revealed mechanistic insights into off-target cleavage. Engineered Cas9s, especially Cas9-HF1, dramatically increased cleavage specificity but not binding specificity compared to wtCas9. Surprisingly, AsCas12a cleavage specificity differed little from that of wtCas9. Initial DNA cleavage sites and end trimming varied by nuclease, guide RNA and the positions of mispaired nucleotides. More broadly, NucleaSeq enables rapid, quantitative and systematic comparisons of specificity and cleavage outcomes across engineered and natural nucleases.

CRISPR/Cas9 treatment causes extended TP53-dependent cell cycle arrest in human cells.

While the mechanism of CRISPR/Cas9 cleavage is understood, the basis for the large variation in mutant recovery for a given target sequence between cell lines is much less clear. We hypothesized that this variation may be due to differences in how the DNA damage response affects cell cycle progression. We used incorporation of EdU as a marker of cell cycle progression to analyze the response of several human cell lines to CRISPR/Cas9 treatment with a single guide directed to a unique locus. Cell lines with functionally wild-type TP53 exhibited higher levels of cell cycle arrest compared to lines without. Chemical inhibition of TP53 protein combined with TP53 and RB1 transcript silencing alleviated induced arrest in TP53+/+ cells. Using dCas9, we determined this arrest is driven in part by Cas9 binding to DNA. Additionally, wild-type Cas9 induced fewer 53BP1 foci in TP53+/+ cells compared to TP53−/− cells and DD-Cas9, suggesting that differences in break sensing are responsible for cell cycle arrest variation. We conclude that CRISPR/Cas9 treatment induces a cell cycle arrest dependent on functional TP53 as well as Cas9 DNA binding and cleavage. Our findings suggest that transient inhibition of TP53 may increase genome editing recovery in primary and TP53+/+ cell lines.

I-Silence, Please! An Alternative for Gene Disruption via Adenine Base Editors.

i-Silence, Please! An Alternative for Gene Disruption via Adenine Base Editors.

Systemic Delivery of CRISPR/Cas9 Targeting HPV Oncogenes Is Effective at Eliminating Established Tumors.

The recent advancements in CRISPR/Cas9 engineering have resulted in the development of more targeted and potentially safer gene therapies. The challenge in the cancer setting is knowing the driver oncogenes responsible, and the translation of these therapies is hindered by effective and safe delivery methods to target organs with minimal systemic toxicities, on-target specificity of gene editing, and demonstrated lack of long-term adverse events. Using a model system based on cervical cancer, which is driven by the ongoing expression of the human papillomavirus E6 and E7 proteins, we show that CRISPR/Cas9 delivered systemically invivo using PEGylated liposomes results in tumor elimination and complete survival in treated animals. We compared treatment and editing efficiency of two Cas9 variants, wild-type (WT) Cas9 and the highly specific FokI-dCas9, and showed that the latter was not effective. We also explored high-fidelity repair but found that repair was inefficient, occurring in 6%-8% of cells, whereas non-homologous end joining (NHEJ) was highly efficient, occurring in ∼80% of the cells. Finally, we explored the post gene-editing events in tumors and showed that cell death is induced by apoptosis. Overall, our work demonstrates that invivo CRISPR/Cas editing treatment of preexisting tumors is completely effective despite the large payloads.

Kinetic Basis for Improved Specificity of CRISPR/Cas9 High Fidelity Variants

CRISPR/Cas9-mediated is a powerful, programmable genome editing tool that has been widely used for many applications. While engineered Cas9s have been reported to minimize the off-target cleavage efficiency compared with wild type Cas9 in vivo, a rational mechanism for enhanced specificity has not been put forward. Here, we provide kinetic characterization of the Hyper-accurate Cas9 variant (HypaCas9) to provide a basis for improved discrimination against off-target cleavage. We show that chemistry is the rate-limiting step for off-target cleavage in HypaCas9 and is much slower than on-target cleavage in WTCas9, where DNA unwinding is the rate-limiting step. In addition, the intrinsic cleavage rate and non-productive DNA binding state has also greatly been affected in engineered Cas9s. We find that HypaCas9 gains discrimination mainly through slowing down chemistry and rebalancing kinetic partitioning to favor release rather than cleavage of the bound substrate. Support or Funding Information This work was supported in part by the Welch Foundation grants (F-1604) (to K.A.J.) and (F-1938) (to D.W.T.). Free energy profile for WTCas9 and HypaCas9 for on-target and off-target cleavage (A)kobs, HNH cleavage rates for on-target and off-target cleavage by WTCas9 and HypaCas9. (B)The two-steps for R-loop formation rates for on-target and off-target cleavage of WTCas9 and HypaCas9 were estimated by stopped-flow fluorescence measurements. (C)The free energy profile was calculated using transition state theory: ΔG‡ = RT[ln(kT/h) − ln(kobs)] kcal/mol using the equilibrium constants from globally fitting. This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Improving Plant Genome Editing with High-Fidelity xCas9 and Non-canonical PAM-Targeting Cas9-NG

Two recently engineered SpCas9 variants, namely xCas9 and Cas9-NG, show promising potential in improving targeting specificity and broadening the targeting range. In this study, we evaluated these Cas9 variants in the model and crop plant, rice. We first tested xCas9-3.7, the most effective xCas9 variant in mammalian cells, for targeted mutagenesis at 16 possible NGN PAM (protospacer adjacent motif) combinations in duplicates. xCas9 exhibited nearly equivalent editing efficiency to wild-type Cas9 (Cas9-WT) at most canonical NGG PAM sites tested, whereas it showed limited activity at non-canonical NGH (H = A, C, T) PAM sites. High editing efficiency of xCas9 at NGG PAMs was further demonstrated with C to T base editing by both rAPOBEC1 and PmCDA1 cytidine deaminases. With mismatched sgRNAs, we found that xCas9 had improved targeting specificity over the Cas9-WT. Furthermore, we tested two Cas9-NG variants, Cas9-NGv1 and Cas9-NG, for targeting NGN PAMs. Both Cas9-NG variants showed higher editing efficiency at most non-canonical NG PAM sites tested, and enabled much more efficient editing than xCas9 at AT-rich PAM sites such as GAT, GAA, and CAA. Nevertheless, we found that Cas9-NG variants showed significant reduced activity at the canonical NGG PAM sites. In stable transgenic rice lines, we demonstrated that Cas9-NG had much higher editing efficiency than Cas9-NGv1 and xCas9 at NG PAM sites. To expand the base-editing scope, we developed an efficient C to T base-editing system by making fusion of Cas9-NG nickase (D10A version), PmCDA1, and UGI. Taken together, our work benchmarked xCas9 as a high-fidelity nuclease for targeting canonical NGG PAMs and Cas9-NG as a preferred variant for targeting relaxed PAMs for plant genome editing.

Efficient Homologous Recombination in Mice Using Long Single Stranded DNA and CRISPR Cas9 Nickase.

The CRISPR/Cas9 nickase mutant is less prone to off-target double-strand (ds)DNA breaks than wild-type Cas9 because to produce dsDNA cleavage it requires two guide RNAs to target the nickase to nearby opposing strands. Like wild-type Cas9 lesions, these staggered lesions are repaired by either non-homologous end joining or, if a repair template is provided, by homologous recombination (HR). Here, we report very efficient (up to 100%) recovery of heterozygous insertions in Mus musculus produced by long (>300 nt), single-stranded DNA donor template-guided repair of paired-nickase lesions.

Targeted cytochrome P450 3045C1 (CYP3045C1) gene mutation via CRISPR-Cas9 ribonucleoproteins in the marine rotifer Brachionus koreanus

The CRISPR-Cas9 system has revolutionized genetic engineering and has been applied in numerous model organisms to date. To examine the capacity of the CRISPR-Cas9 system for generation of mutants in the marine rotifer Brachionus koreanus, we electroporated purified Cas9 proteins fused with GFP (Cas9-GFP) into rotifers. A dose-dependent increase in green fluorescent signal was highly detected in ovary and eggs. The purified Cas9-GFP proteins showed sustained fluorescence signals in rotifers at 24 h after electroporation, which also suggests stability of Cas9 ribonucleoproteins (RNPs) and the possibility of Cas9-mediated gene editing in rotifers. We electroporated B. koreanus with the wild-type Cas9 and single-guide RNAs targeting the endogenous Bk-CYP3045C1 gene and observed different insertion and deletion (indel) mutation profiles near the DNA cleavage sites using targeted deep sequencing. Although the indel rates were low in several salinity conditions (0.30% in 1 psu and 0.20% in 2 psu), these results confirm successful Cas9 RNP-induced mutations. Our results confirm that CRISPR-Cas9 can be applied to generate diverse mutants to demonstrate the functional roles of genes in rotifers.

Paired CRISPR/Cas9 Nickases Mediate Efficient Site-Specific Integration of F9 into rDNA Locus of Mouse ESCs.

Hemophilia B (HB) is an X-linked recessive bleeding disorder, caused by F9 gene deficiency. Gene therapy combined with the CRISPR/Cas9 technology offers a potential cure for hemophilia B. Now the Cas9 nickase (Cas9n) shows a great advantage in reducing off-target effect compared with wild-type Cas9. In this study, we found that in the multicopy ribosomal DNA (rDNA) locus, the homology directed recombination (HDR) efficiency induced by sgRNA-Cas9n was much higher than sgRNA-Cas9, meanwhile without off-target in six predicted sites. After co-transfection into mESCs with sgRNA-Cas9n and a non-viral rDNA targeting vector pMrnF9, harboring the homology donor template and the human F9 expression cassette, a recombination efficiency of 66.7% was achieved and all targeted clones were confirmed to be site-specific integration of F9 in the rDNA locus by PCR and southern blotting. Targeted mESCs retained the main pluripotent properties and were then differentiated into hepatic progenitor like cells (HPLCs) and mature hepatocytes, which were characterized by hepatic markers and functional assays. Importantly, the differentiated cells could transcribe exogenous F9 and secrete coagulation factor IX (FIX) proteins, suggesting active transcription and stable inheritance of transgenes in the rDNA locus. After intrasplenical transplantation in severe combined immune deficiency (SCID) mice, targeted HPLCs could survive and migrate from spleen to liver, resulting in secretion of exogenous FIX into blood. In summary, we demonstrate an efficient and site-specific gene targeting strategy in rDNA locus for stem cell-based gene therapy for hemophilia B.

Abstract LB-040: New conditional Kras-alleles generated by CRISPR-based genome editing to model tumor initiation

Abstract KRAS is the most frequently mutated oncogene in human cancers, and specific cancer types show a clear bias in the types and frequency of Kras alterations. However, we do not have a clear understanding of how distinct Kras mutations dictate tumor biology and response to therapy. The generation of conditional animal models, such as Lox-Stop-Lox (LSL) KrasG12D and LSL-KrasG12Vgeo mice, have provided important tools to dissect the impact of Kras mutation in tumor development, but these models alone do not recapitulate the spectrum of Kras alterations in human cancer. To better reflect the Kras mutational landscape in human cancers, we have developed a series of critical LSL-Kras mouse models that recapitulate common Kras alterations observed in colorectal (G13D), pancreatic (G12R), and lung cancer (G12C), allowing the direct interrogation of the effects of these Kras mutations on disease phenotype and treatment response. To do this, we targeted embryonic stem cells (ESCs) carrying the LSL-KrasG12D allele, by co-transfection of a modified high-fidelity Cas9 (Cas9-HFz), a LSL-Kras-targeted sgRNA, and an HDR template carrying the new mutation. While Cas9-HFz displayed a slight decrease in homology-directed repair (HDR) efficiency in comparison with wildtype Cas9, it enabled high specificity editing of only the LSL allele. Targeted deep sequencing revealed a significant reduction in ‘off-target' events in wildtype Kras locus in Cas9-HFz transfected samples compared to unmodified Cas9. We next generated transgenic mice by blastocyst injection and produced mice carrying each LSL-Kras variant, a pancreas specific Cre (p48-Cre) and a far-red fluorescent Cre-reporter (mKate2). We are now analyzing the impact of specific Kras alterations in tumor initiation in distinct tissues such as the pancreas, colon and lung. Together with available LSL-KrasG12D and LSL-KrasG12V already available, our new alleles will serve as critical tools for better dissect the genetic factors that dictate disease initiation, progression, and response to therapy. Citation Format: Maria Paz Zafra, Emma M. Schatoff, Teng Han, Lukas E. Dow. New conditional Kras-alleles generated by CRISPR-based genome editing to model tumor initiation [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr LB-040.

Improved sgRNA design in bacteria via genome-wide activity profiling.

CRISPR/Cas9 is a promising tool in prokaryotic genome engineering, but its success is limited by the widely varying on-target activity of single guide RNAs (sgRNAs). Based on the association of CRISPR/Cas9-induced DNA cleavage with cellular lethality, we systematically profiled sgRNA activity by co-expressing a genome-scale library (∼70 000 sgRNAs) with Cas9 or its specificity-improved mutant in Escherichia coli. Based on this large-scale dataset, we constructed a comprehensive and high-density sgRNA activity map, which enables selecting highly active sgRNAs for any locus across the genome in this model organism. We also identified ‘resistant’ genomic loci with respect to CRISPR/Cas9 activity, notwithstanding the highly accessible DNA in bacterial cells. Moreover, we found that previous sgRNA activity prediction models that were trained on mammalian cell datasets were inadequate when coping with our results, highlighting the key limitations and biases of previous models. We hence developed an integrated algorithm to accurately predict highly effective sgRNAs, aiming to facilitate CRISPR/Cas9-based genome engineering, screenings and antimicrobials design in bacteria. We also isolated the important sgRNA features that contribute to DNA cleavage and characterized their key differences among wild type Cas9 and its mutant, shedding light on the biophysical mechanisms of the CRISPR/Cas9 system.

Abstract A18: Generation of new conditional Kras-alleles by CRISPR-based genome editing

Abstract KRAS is the most frequently mutated oncogene in human cancers, and specific cancer types show a clear bias in the types and frequency of Kras alterations. However, we do not have a clear understanding of how distinct Kras mutations dictate tumor biology and response to therapy. The generation of conditional animal models, such as Lox-Stop-Lox (LSL) KrasG12D and LSL-KrasG12Vgeo mice, has provided important tools to dissect the impact of Kras mutation in tumor development, but these models alone do not recapitulate the spectrum of Kras alterations in human cancer. To better reflect the Kras mutational landscape in human cancers, we have developed a series of critical LSL-Kras mouse models that recapitulate common Kras alterations observed in colorectal (G13D), pancreatic (G12R), and lung cancer (G12C), allowing the direct interrogation of the effects of these Kras mutations on disease phenotype and treatment response. To do this, we targeted embryonic stem cells (ESCs) carrying the LSL-KrasG12D allele, by co-transfection of a modified high-fidelity Cas9 (Cas9-HFz), a LSL-Kras-targeted sgRNA, and an HDR template carrying the new mutation. While Cas9-HFz displayed a slight decrease in homology-directed repair (HDR) efficiency in comparison with wild-type Cas9, it enabled high specificity editing of only the LSL allele. Targeted deep sequencing revealed a significant reduction in “off-target” events in wild-type Kras locus in Cas9-HFz transfected samples compared to unmodified Cas9. We next generated transgenic mice by blastocyst injection and produced mice carrying each LSL-Kras variant, a pancreas-specific Cre (p48-Cre), and a far-red fluorescent Cre-reporter (mKate2). We are now analyzing the impact of specific Kras alterations in tumor initiation in distinct tissues such as the pancreas, colon, and lung. Together with available LSL-KrasG12D and LSL-KrasG12V already available, our new alleles will serve as critical tools for better dissecting the genetic factors that dictate disease initiation, progression, and response to therapy. Citation Format: Maria Paz Zafra, Emma M. Schatoff, Teng Han, Lukas E. Dow. Generation of new conditional Kras-alleles by CRISPR-based genome editing [abstract]. In: Proceedings of the AACR Special Conference: Advances in Modeling Cancer in Mice: Technology, Biology, and Beyond; 2017 Sep 24-27; Orlando, Florida. Philadelphia (PA): AACR; Cancer Res 2018;78(10 Suppl):Abstract nr A18.

COL7A1 Editing via CRISPR/Cas9 in Recessive Dystrophic Epidermolysis Bullosa

Designer nucleases allow specific and precise genomic modifications and represent versatile molecular tools for the correction of disease-associated mutations. In this study, we have exploited an ex vivo CRISPR/Cas9-mediated homology-directed repair approach for the correction of a frequent inherited mutation in exon 80 of COL7A1, which impairs type VII collagen expression, causing the severe blistering skin disease recessive dystrophic epidermolysis bullosa. Upon CRISPR/Cas9 treatment of patient-derived keratinocytes, using either the wild-type Cas9 or D10A nickase, corrected single-cell clones expressed and secreted similar levels of type VII collagen as control keratinocytes. Transplantation of skin equivalents grown from corrected keratinocytes onto immunodeficient mice showed phenotypic reversion with normal localization of type VII collagen at the basement membrane zone, compared with uncorrected keratinocytes, as well as fully stratified and differentiated skin layers without indication of blister development. Next-generation sequencing revealed on-target efficiency of up to 30%, whereas nuclease-mediated off-target site modifications at predicted genomic loci were not detected. These data demonstrate the potential of the CRISPR/Cas9 technology as a possible ex vivo treatment option for genetic skin diseases in the future.

RICE CRISPR: Rapidly increased cut ends by an exonuclease Cas9 fusion in zebrafish.

Application of CRISPR-Cas9 technology in diverse organisms has resulted in an explosion of genome modification efforts. To expand the toolbox of applications, we have created an E. coli Exonuclease I (sbcB)-Cas9 fusion that has altered enzymatic activity in zebrafish embryos. This Cas9 variant has increased mutation efficiency and favors longer deletions relative to wild-type Cas9. We anticipate that this variant will allow for more efficient screening for F0 phenotypes and mutation of a larger spectrum of genomic targets including deletion of regulatory regions and creating loss of function mutations in transcription units with poor sequence conservation such as lncRNAs where larger deletions may be required for loss of function.

CRISPR-STOP: gene silencing through base-editing-induced nonsense mutations.

CRISPR-Cas9-induced DNA damage may have deleterious effects at high-copy-number genomic regions. Here, we use CRISPR base editors to knock out genes by changing single nucleotides to create stop codons. We show that the CRISPR-STOP method is an efficient and less deleterious alternative to wild-type Cas9 for gene-knockout studies. Early stop codons can be introduced in ∼17,000 human genes. CRISPR-STOP-mediated targeted screening demonstrates comparable efficiency to WT Cas9, which indicates the suitability of our approach for genome-wide functional screenings.

Heritable Genomic Fragment Deletions and Small Indels in the Putative ENGase Gene Induced by CRISPR/Cas9 in Barley.

Targeted genome editing with the CRISPR/Cas9 system has been used extensively for the selective mutation of plant genes. Here we used CRISPR/Cas9 to disrupt the putative barley (Hordeum vulgare cv. “Golden Promise”) endo-N-acetyl-β-D-glucosaminidase (ENGase) gene. Five single guide RNAs (sgRNAs) were designed for different target sites in the upstream part of the ENGase coding region. Targeted fragment deletions were induced by co-bombarding selected combinations of sgRNA with wild-type cas9 using separate plasmids, or by co-infection with separate Agrobacterium tumefaciens cultures. Genotype screening was carried out in the primary transformants (T0) and their T1 progeny to confirm the presence of site-specific small insertions and deletions (indels) and genomic fragment deletions between pairs of targets. Cas9-induced mutations were observed in 78% of the plants, a higher efficiency than previously reported in barley. Notably, there were differences in performance among the five sgRNAs. The induced indels and fragment deletions were transmitted to the T1 generation, and transgene free (sgRNA:cas9 negative) genome-edited homozygous ENGase knock outs were identified among the T1 progeny. We have therefore demonstrated that mutant barley lines with a disrupted endogenous ENGase and defined fragment deletions can be produced efficiently using the CRISPR/Cas9 system even when this requires co-transformation with multiple plasmids by bombardment or Agrobacterium-mediated transformation. We confirm the specificity and heritability of the mutations and the ability to efficiently generate homozygous mutant T1 plants.

CRISPR-Cas9 system-driven site-specific selection pressure on Herpes simplex virus genomes

The CRISPR-Cas9 (clustered regularly interspaced short palindromic repeats and CRISPR-associated protein 9) system has been widely used for viral genome editing, transcription regulation and chromosomal localization in eukaryotic cells. In this study, a guide RNA (gRNA) that specifically recognizes HSV-1 viral genomes was used in the CRISPR-Cas9 system to inhibit viral replication. This inhibition could be achieved with both wild type Cas9 protein and Cas9 nickase (D10A). By targeting viral genomes containing sequences recognized by the gRNA, the CRISPR-Cas9 system distinguished between different viral genome sequences and provided single nucleotide-specific selection pressure to significantly change the proportions of viruses in a mixed viral pool. This finding indicates the utility of this tool for virus selection without the need for antibiotics or reporter genes, which could potentially save time compared to other methods used for screening and purifying mutant viruses.

Optimization of the production of knock-in alleles by CRISPR/Cas9 microinjection into the mouse zygote

Microinjection of the CRISPR/Cas9 system in zygotes is an efficient and comparatively fast method to generate genetically modified mice. So far, only few knock-in mice have been generated using this approach, and because no systematic study has been performed, parameters controlling the efficacy of CRISPR/Cas9-mediated targeted insertion are not fully established. Here, we evaluated the effect of several parameters on knock-in efficiency changing only one variable at a time. We found that knock-in efficiency was dependent on injected Cas9 mRNA and single-guide RNA concentrations and that cytoplasmic injection resulted in more genotypic complexity compared to pronuclear injection. Our results also indicated that injection into the pronucleus compared to the cytoplasm is preferable to generate knock-in alleles with an oligonucleotide or a circular plasmid. Finally, we showed that Cas9D10A nickase variant was less efficient than wild-type Cas9 for generating knock-in alleles and caused a higher rate of mosaicism. Thus, our study provides valuable information that will help to improve the future production of precise genetic modifications in mice.

Organoid technologies meet genome engineering.

Three-dimensional (3D) stem cell differentiation cultures recently emerged as a novel model system for investigating human embryonic development and disease progression in vitro, complementing existing animal and two-dimensional (2D) cell culture models. Organoids, the 3D self-organizing structures derived from pluripotent or somatic stem cells, can recapitulate many aspects of structural organization and functionality of their in vivo organ counterparts, thus holding great promise for biomedical research and translational applications. Importantly, faithful recapitulation of disease and development processes relies on the ability to modify the genomic contents in organoid cells. The revolutionary genome engineering technologies, CRISPR/Cas9 in particular, enable investigators to generate various reporter cell lines for prompt validation of specific cell lineages as well as to introduce disease-associated mutations for disease modeling. In this review, we provide historical overviews, and discuss technical considerations, and potential future applications of genome engineering in 3D organoid models.