A new age in functional genomics using CRISPR/Cas9 in arrayed library screening

Advancements in CRISPR screens for the development of cancer immunotherapy strategies

CRISPR screen technology enables systematic and scalable interrogation of gene function by using the CRISPR-Cas9 system to perturb gene expression. In the field of cancer immunotherapy, this technology has empowered the discovery of genes, biomarkers, and pathways that regulate tumor development and progression, immune reactivity, and the effectiveness of immunotherapeutic interventions. By conducting large-scale genetic screens, researchers have successfully identified novel targets to impede tumor growth, enhance anti-tumor immune responses, and surmount immunosuppression within the tumor microenvironment (TME). Here, we present an overview of CRISPR screens conducted in tumor cells for the purpose of identifying novel therapeutic targets. We also explore the application of CRISPR screens in immune cells to propel the advancement of cell-based therapies, encompassing T cells, natural killer cells, dendritic cells, and macrophages. Furthermore, we outline the crucial components necessary for the successful implementation of immune-specific CRISPR screens and explore potential directions for future research.

Manipulating and studying gene function in human pluripotent stem cell models

Human pluripotent stem cells (hPSCs) are uniquely suited to study human development and disease and promise to revolutionize regenerative medicine. These applications rely on robust methods to manipulate gene function in hPSC models. This comprehensive review aims to both empower scientists approaching the field and update experienced stem cell biologists. We begin by highlighting challenges with manipulating gene expression in hPSCs and their differentiated derivatives, and relevant solutions (transfection, transduction, transposition, and genomic safe harbor editing). We then outline how to perform robust constitutive or inducible loss-, gain-, and change-of-function experiments in hPSCs models, both using historical methods (RNA interference, transgenesis, and homologous recombination) and modern programmable nucleases (particularly CRISPR/Cas9 and its derivatives, i.e., CRISPR interference, activation, base editing, and prime editing). We further describe extension of these approaches for arrayed or pooled functional studies, including emerging single-cell genomic methods, and the related design and analytical bioinformatic tools. Finally, we suggest some directions for future advancements in all of these areas. Mastering the combination of these transformative technologies will empower unprecedented advances in human biology and medicine.

New Target Gene Screening Using Shortened and Random sgRNA Libraries in Microbial CRISPR Interference

CRISPR interference (CRISPRi) screening has been used for identification of target genes related to specific phenotypes using single-molecular guide RNA (sgRNA) libraries. In CRISPRi screening, the sizes of random sgRNA libraries contained with the original target recognition sequences are large (∼10¹²). Here, we demonstrated that the length of the target recognition sequence (TRS) can be shortened in sgRNAs from the original 20 nucleotides (N₂₀) to 9 nucleotides (N₉) that is still sufficient for dCas9 to repress target genes in the xylose operon of Escherichia coli, regardless of binding to a promoter or open reading frame region. Based on the results, we constructed random sgRNA plasmid libraries with 5'-shortened TRS lengths, and identified xylose metabolic target genes by Sanger sequencing of sgRNA plasmids purified from Xyl^- phenotypic cells. Next, the random sgRNA libraries were harnessed to screen for target genes to enhance violacein pigment production in synthetic E. coli cells. Seventeen target genes were selected by analyzing the redundancy of the TRS in sgRNA plasmids in dark purple colonies. Among them, seven genes (tyrR, pykF, cra, ptsG, pykA, sdaA, and tnaA) have been known to increase the intracellular l-tryptophan pool, the precursor of a violacein. Seventeen cells with a single deletion of each target gene exhibited a significant increase in violacein production. These results indicate that using shortened random TRS libraries for CRISPRi can be simple and cost-effective for phenotype-based target gene screening.

Automated high-content imaging in iPSC-derived neuronal progenitors

Induced pluripotent stem cells (iPSCs) have great potential as physiological disease models for human disorders where access to primary cells is difficult, such as neurons. In recent years, many protocols have been developed for the generation of iPSCs and the differentiation into specialised cell subtypes of interest. More recently, these models have been modified to allow large-scale phenotyping and high-content screening of small molecule compounds in iPSC-derived neuronal cells. Here, we describe the automated seeding of day 11 ventral midbrain progenitor cells into 96-well plates, administration of compounds, automated staining for immunofluorescence, the acquisition of images on a high-content screening platform and workflows for image analysis.

Understanding neural development and diseases using CRISPR screens in human pluripotent stem cell-derived cultures

The brain is arguably the most complex part of the human body in form and function. Much remains unclear about the molecular mechanisms that regulate its normal and pathological physiology. This lack of knowledge largely stems from the inaccessible nature of the human brain, and the limitation of animal models. As a result, brain disorders are difficult to understand and even more difficult to treat. Recent advances in generating human pluripotent stem cells (hPSCs)-derived 2-dimensional (2D) and 3-dimensional (3D) neural cultures have provided an accessible system to model the human brain. Breakthroughs in gene editing technologies such as CRISPR/Cas9 further elevate the hPSCs into a genetically tractable experimental system. Powerful genetic screens, previously reserved for model organisms and transformed cell lines, can now be performed in human neural cells. Combined with the rapidly expanding single-cell genomics toolkit, these technological advances culminate to create an unprecedented opportunity to study the human brain using functional genomics. This review will summarize the current progress of applying CRISPR-based genetic screens in hPSCs-derived 2D neural cultures and 3D brain organoids. We will also evaluate the key technologies involved and discuss their related experimental considerations and future applications.

The Trend of CRISPR-Based Technologies in COVID-19 Disease: Beyond Genome Editing

Biotechnological approaches have always sought to utilize novel and efficient methods in the prevention, diagnosis, and treatment of diseases. This science has consistently tried to revolutionize medical science by employing state-of-the-art technologies in genomic and proteomic engineering. CRISPR-Cas system is one of the emerging techniques in the field of biotechnology. To date, the CRISPR-Cas system has been extensively applied in gene editing, targeting genomic sequences for diagnosis, treatment of diseases through genomic manipulation, and in creating animal models for preclinical researches. With the emergence of the COVID-19 pandemic in 2019, there is need for the development and modification of novel tools such as the CRISPR-Cas system for use in diagnostic emergencies. This system can compete with other existing biotechnological methods in accuracy, precision, and wide performance that could guarantee its future in these conditions. In this article, we review the various platforms of the CRISPR-Cas system meant for SARS-CoV-2 diagnosis, anti-viral therapeutic procedures, producing animal models for preclinical studies, and genome-wide screening studies toward drug and vaccine development.

A Landscape of CRISPR/Cas Technique for Emerging Viral Disease Diagnostics and Therapeutics: Progress and Prospects

Viral diseases have emerged as a serious threat to humanity and as a leading cause of morbidity worldwide. Many viral diagnostic methods and antiviral therapies have been developed over time, but we are still a long way from treating certain infections caused by viruses. Acquired immunodeficiency syndrome (AIDS) is one of the challenges where current medical science advancements fall short. As a result, new diagnostic and treatment options are desperately needed. The CRISPR/Cas9 system has recently been proposed as a potential therapeutic approach for viral disease treatment. CRISPR/Cas9 is a specialised, effective, and adaptive gene-editing technique that can be used to modify, delete, or correct specific DNA sequences. It has evolved into an advanced, configurable nuclease-based single or multiple gene-editing tool with a wide range of applications. It is widely preferred simply because its operational procedures are simple, inexpensive, and extremely efficient. Exploration of infectious virus genomes is required for a comprehensive study of infectious viruses. Herein, we have discussed the historical timeline-based advancement of CRISPR, CRISPR/Cas9 as a gene-editing technology, the structure of CRISPR, and CRISPR as a diagnostic tool for studying emerging viral infections. Additionally, utilizing CRISPR/Cas9 technology to fight viral infections in plants, CRISPR-based diagnostics of viruses, pros, and cons, and bioethical issues of CRISPR/Cas9-based genomic modification are discussed.

Multi-hallmark long noncoding RNA maps reveal non-small cell lung cancer vulnerabilities

Long noncoding RNAs (lncRNAs) are widely dysregulated in cancer, yet their functional roles in cancer hallmarks remain unclear. We employ pooled CRISPR deletion to perturb 831 lncRNAs detected in KRAS-mutant non-small cell lung cancer (NSCLC) and measure their contribution to proliferation, chemoresistance, and migration across two cell backgrounds. Integrative analysis of these data outperforms conventional "dropout" screens in identifying cancer genes while prioritizing disease-relevant lncRNAs with pleiotropic and background-independent roles. Altogether, 80 high-confidence oncogenic lncRNAs are active in NSCLC, which tend to be amplified and overexpressed in tumors. A follow-up antisense oligonucleotide (ASO) screen shortlisted two candidates, Cancer Hallmarks in Lung LncRNA 1 (CHiLL1) and GCAWKR, whose knockdown consistently suppressed cancer hallmarks in two- and three-dimension tumor models. Molecular phenotyping reveals that CHiLL1 and GCAWKR control cellular-level phenotypes via distinct transcriptional networks. This work reveals a multi-dimensional functional lncRNA landscape underlying NSCLC that contains potential therapeutic vulnerabilities.

High-Throughput CRISPR Screening in Hematological Neoplasms

CRISPR is becoming an indispensable tool in biological research, revolutionizing diverse fields of medical research and biotechnology. In the last few years, several CRISPR-based genome-targeting tools have been translated for the study of hematological neoplasms. However, there is a lack of reviews focused on the wide uses of this technology in hematology. Therefore, in this review, we summarize the main CRISPR-based approaches of high throughput screenings applied to this field. Here we explain several libraries and algorithms for analysis of CRISPR screens used in hematology, accompanied by the most relevant databases. Moreover, we focus on (1) the identification of novel modulator genes of drug resistance and efficacy, which could anticipate relapses in patients and (2) new therapeutic targets and synthetic lethal interactions. We also discuss the approaches to uncover novel biomarkers of malignant transformations and immune evasion mechanisms. We explain the current literature in the most common lymphoid and myeloid neoplasms using this tool. Then, we conclude with future directions, highlighting the importance of further gene candidate validation and the integration and harmonization of the data from CRISPR screening approaches.

Multiplexed high-throughput localized electroporation workflow with deep learning-based analysis for cell engineering

Manipulation of cells for applications such as biomanufacturing and cell-based therapeutics involves introducing biomolecular cargoes into cells. However, successful delivery is a function of multiple experimental factors requiring several rounds of optimization. Here, we present a high-throughput multiwell-format localized electroporation device (LEPD) assisted by deep learning image analysis that enables quick optimization of experimental factors for efficient delivery. We showcase the versatility of the LEPD platform by successfully delivering biomolecules into different types of adherent and suspension cells. We also demonstrate multicargo delivery with tight dosage distribution and precise ratiometric control. Furthermore, we used the platform to achieve functional gene knockdown in human induced pluripotent stem cells and used the deep learning framework to analyze protein expression along with changes in cell morphology. Overall, we present a workflow that enables combinatorial experiments and rapid analysis for the optimization of intracellular delivery protocols required for genetic manipulation.

Bridging Glycomics and Genomics: New Uses of Functional Genetics in the Study of Cellular Glycosylation

All living cells are coated with a diverse collection of carbohydrate molecules called glycans. Glycans are key regulators of cell behavior and important therapeutic targets for human disease. Unlike proteins, glycans are not directly templated by discrete genes. Instead, they are produced through multi-gene pathways that generate a heterogenous array of glycoprotein and glycolipid antigens on the cell surface. This genetic complexity has sometimes made it challenging to understand how glycosylation is regulated and how it becomes altered in disease. Recent years, however, have seen the emergence of powerful new functional genomics technologies that allow high-throughput characterization of genetically complex cellular phenotypes. In this review, we discuss how these techniques are now being applied to achieve a deeper understanding of glyco-genomic regulation. We highlight specifically how methods like ChIP-seq, RNA-seq, CRISPR genomic screening and scRNA-seq are being used to map the genomic basis for various cell-surface glycosylation states in normal and diseased cell types. We also offer a perspective on how emerging functional genomics technologies are likely to create further opportunities for studying cellular glycobiology in the future. Taken together, we hope this review serves as a primer to recent developments at the glycomics-genomics interface.

Paired guide RNA CRISPR-Cas9 screening for protein-coding genes and lncRNAs involved in transdifferentiation of human B-cells to macrophages

CRISPR-Cas9 screening libraries have arisen as a powerful tool to identify protein-coding (pc) and non-coding genes playing a role along different processes. In particular, the usage of a nuclease active Cas9 coupled to a single gRNA has proven to efficiently impair the expression of pc-genes by generating deleterious frameshifts. Here, we first demonstrate that targeting the same gene simultaneously with two guide RNAs (paired guide RNAs, pgRNAs) synergistically enhances the capacity of the CRISPR-Cas9 system to knock out pc-genes. We next design a library to target, in parallel, pc-genes and lncRNAs known to change expression during the transdifferentiation from pre-B cells to macrophages. We show that this system is able to identify known players in this process, and also predicts 26 potential novel ones, of which we select four (two pc-genes and two lncRNAs) for deeper characterization. Our results suggest that in the case of the candidate lncRNAs, their impact in transdifferentiation may be actually mediated by enhancer regions at the targeted loci, rather than by the lncRNA transcripts themselves. The CRISPR-Cas9 coupled to a pgRNAs system is, therefore, a suitable tool to simultaneously target pc-genes and lncRNAs for genomic perturbation assays.

Computational analyses of mechanism of action (MoA): data, methods and integration

The elucidation of a compound's Mechanism of Action (MoA) is a challenging task in the drug discovery process, but it is important in order to rationalise phenotypic findings and to anticipate potential side-effects. Bioinformatic approaches, advances in machine learning techniques and the increasing deposition of high-throughput data in public databases have significantly contributed to recent advances in the field, but it is not straightforward to decide which data and methods are most suitable to use in a given case. In this review, we focus on these methods and data and their applications in generating MoA hypotheses for subsequent experimental validation. We discuss compound-specific data such as -omics, cell morphology and bioactivity data, as well as commonly used supplementary prior knowledge such as network and pathway data, and provide information on databases where this data can be accessed. In terms of methodologies, we discuss both well-established methods (connectivity mapping, pathway enrichment) as well as more developing methods (neural networks and multi-omics integration). Finally, we review case studies where the MoA of a compound was successfully suggested from computational analysis by incorporating multiple data modalities and/or methodologies. Our aim for this review is to provide researchers with insights into the benefits and drawbacks of both the data and methods in terms of level of understanding, biases and interpretation - and to highlight future avenues of investigation which we foresee will improve the field of MoA elucidation, including greater public access to -omics data and methodologies which are capable of data integration.

Challenges of CRISPR-Based Gene Editing in Primary T Cells

Adaptive T-cell immunotherapy holds great promise for the successful treatment of leukemia, as well as other types of cancers. More recently, it was also shown to be an effective treatment option for chronic virus infections in immunosuppressed patients. Autologous or allogeneic T cells used for immunotherapy are usually genetically modified to express novel T-cell or chimeric antigen receptors. The production of such cells was significantly simplified with the CRISPR/Cas system, allowing for the deletion or insertion of novel genes at specific locations within the genome. In this review, we describe recent methodological breakthroughs that were important for the conduction of these genetic modifications, summarize crucial points to be considered when conducting such experiments, and highlight the potential pitfalls of these approaches.

Human Organoid and Supporting Technologies for Cancer and Toxicological Research

Recent progress in the field of organoid-based cell culture systems has enabled the use of patient-derived cells in conditions that resemble those in cancer tissue, which are better than two-dimensional (2D) cultured cell lines. In particular, organoids allow human cancer cells to be handled in conditions that resemble those in cancer tissue, resulting in more efficient establishment of cells compared with 2D cultured cell lines, thus enabling the use of multiple patient-derived cells with cells from different genetic background, in keeping with the heterogeneity of the cells. One of the most valuable points of using organoids is that human cells from either healthy or cancerous tissue can be used. Using genome editing technology such as clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein, organoid genomes can be modified to, for example, cancer-prone genomes. The normal, cancer, or genome-modified organoids can be used to evaluate whether chemicals have genotoxic or non-genotoxic carcinogenic activity by evaluating the cancer incidence, cancer progression, and cancer metastasis. In this review, the organoid technology and the accompanying technologies were summarized and the advantages of organoid-based toxicology and its application to pancreatic cancer study were discussed.

Exploring liver cancer biology through functional genetic screens

As the fourth leading cause of cancer-related death in the world, liver cancer poses a major threat to human health. Although a growing number of therapies have been approved for the treatment of hepatocellular carcinoma in the past few years, most of them only provide a limited survival benefit. Therefore, an urgent need exists to identify novel targetable vulnerabilities and powerful drug combinations for the treatment of liver cancer. The advent of functional genetic screening has contributed to the advancement of liver cancer biology, uncovering many novel genes involved in tumorigenesis and cancer progression in a high-throughput manner. In addition, this unbiased screening platform also provides an efficient tool for the exploration of the mechanisms involved in therapy resistance as well as identifying potential targets for therapy. In this Review, we describe how functional screens can help to deepen our understanding of liver cancer and guide the development of new therapeutic strategies.

CRISPR Screens in Toxicology Research: An Overview

The use of genome editing tools is expanding our understanding of various human diseases by providing insight into gene-disease interactions. Despite the recognized role of toxicants in the development of human health issues and conditions, there is currently limited characterization of their mechanisms of action, and the application of CRISPR-based genome editing to the study of toxicants could help in the identification of novel gene-environment interactions. CRISPR-based functional screens enable identification of cellular mechanisms fundamental for response and susceptibility to a given toxicant. The aim of this review is to inform future directions in the application of CRISPR technologies in toxicological studies. We review and compare different types of CRISPR-based methods including pooled, anchored, combinatorial, and perturb-sequencing screens in vitro, in addition to pooled screenings in model organisms. © 2021 Wiley Periodicals LLC.

Determining the Biological Mechanisms of Action for Environmental Exposures: Applying CRISPR/Cas9 to Toxicological Assessments

Toxicology is a constantly evolving field, especially in the area of developing alternatives to animal testing. Toxicological research must evolve and utilize adaptive technologies in an effort to improve public, environmental, and occupational health. The most commonly cited mechanisms of toxic action after exposure to a chemical or particle test substance is oxidative stress. However, because oxidative stress involves a plethora of genes and proteins, the exact mechanism(s) are not commonly defined. Exact mechanisms of toxicity can be revealed using an emerging laboratory technique referred to as CRISPR (clustered regularly interspaced short palindromic repeats). This article reviews the most common CRISPR techniques utilized today and how each may be applied in Toxicological Sciences. Specifically, the CRISPR/CRISPR-associated protein complex is used for single gene knock-outs, whereas CRISPR interference/activation is used for silencing or activating (respectively) ribonucleic acid. Finally, CRISPR libraries are used for knocking-out entire gene pathways. This review highlights the application of CRISPR in toxicology to elucidate the exact mechanism through which toxicants perturb normal cellular functions.

ER-mitochondria contact sites in neurodegeneration: genetic screening approaches to investigate novel disease mechanisms

Mitochondria-ER contact sites (MERCS) are known to underpin many important cellular homoeostatic functions, including mitochondrial quality control, lipid metabolism, calcium homoeostasis, the unfolded protein response and ER stress. These functions are known to be dysregulated in neurodegenerative diseases, including Parkinson's disease (PD), Alzheimer's disease (AD) and amyloid lateral sclerosis (ALS), and the number of disease-related proteins and genes being associated with MERCS is increasing. However, many details regarding MERCS and their role in neurodegenerative diseases remain unknown. In this review, we aim to summarise the current knowledge regarding the structure and function of MERCS, and to update the field on current research in PD, AD and ALS. Furthermore, we will evaluate high-throughput screening techniques, including RNAi vs CRISPR/Cas9, pooled vs arrayed formats and how these could be combined with current techniques to visualise MERCS. We will consider the advantages and disadvantages of each technique and how it can be utilised to uncover novel protein pathways involved in MERCS dysfunction in neurodegenerative diseases.

CRISPR-Cas technology in corn: a new key to unlock genetic knowledge and create novel products

Since its inception in 2012, CRISPR-Cas technologies have taken the life science community by storm. Maize genetics research is no exception. Investigators around the world have adapted CRISPR tools to advance maize genetics research in many ways. The principle application has been targeted mutagenesis to confirm candidate genes identified using map-based methods. Researchers are also developing tools to more effectively apply CRISPR-Cas technologies to maize because successful application of CRISPR-Cas relies on target gene identification, guide RNA development, vector design and construction, CRISPR-Cas reagent delivery to maize tissues, and plant characterization, each contributing unique challenges to CRISPR-Cas efficacy. Recent advances continue to chip away at major barriers that prevent more widespread use of CRISPR-Cas technologies in maize, including germplasm-independent delivery of CRISPR-Cas reagents and production of high-resolution genomic data in relevant germplasm to facilitate CRISPR-Cas experimental design. This has led to the development of novel breeding tools to advance maize genetics and demonstrations of how CRISPR-Cas technologies might be used to enhance maize germplasm.

Supplementary Information

The online version contains supplementary material available at 10.1007/s11032-021-01200-9.

Genetic engineering in organoids

Three-dimensional organoids have been widely used for developmental and disease modeling. Organoids are derived from both adult and pluripotent stem cells. Various types are available for mimicking almost all major organs and tissues in the mouse and human. While culture protocols for stepwise differentiation and long-term expansion are well established, methods for genetic manipulation in organoids still need further standardization. In this review, we summarized different methods for organoid genetics and provide the pros and cons of each method for designing an optimal strategy.

DGK and DZHK position paper on genome editing: basic science applications and future perspective

For a long time, gene editing had been a scientific concept, which was limited to a few applications. With recent developments, following the discovery of TALEN zinc-finger endonucleases and in particular the CRISPR/Cas system, gene editing has become a technique applicable in most laboratories. The current gain- and loss-of function models in basic science are revolutionary as they allow unbiased screens of unprecedented depth and complexity and rapid development of transgenic animals. Modifications of CRISPR/Cas have been developed to precisely interrogate epigenetic regulation or to visualize DNA complexes. Moreover, gene editing as a clinical treatment option is rapidly developing with first trials on the way. This article reviews the most recent progress in the field, covering expert opinions gathered during joint conferences on genome editing of the German Cardiac Society (DGK) and the German Center for Cardiovascular Research (DZHK). Particularly focusing on the translational aspect and the combination of cellular and animal applications, the authors aim to provide direction for the development of the field and the most frequent applications with their problems.

Genome editing technologies: CRISPR, LEAPER, RESTORE, ARCUT, SATI, and RESCUE

Genome editing technologies include techniques used for desired genetic modifications and allow the insertion, modification or deletion of specific DNA fragments. Recent advances in genome biology offer unprecedented promise for interdisciplinary collaboration and applications in gene editing. New genome editing technologies enable specific and efficient genome modifications. The sources that inspire these modifications and already exist in the genome are DNA degradation enzymes and DNA repair pathways. Six of these recent technologies are the clustered regularly interspaced short palindromic repeats (CRISPR), leveraging endogenous ADAR for programmable editing of RNA (LEAPER), recruiting endogenous ADAR to specific transcripts for oligonucleotide-mediated RNA editing (RESTORE), chemistry-based artificial restriction DNA cutter (ARCUT), single homology arm donor mediated intron-targeting integration (SATI), RNA editing for specific C-to-U exchange (RESCUE). These technologies are widely used from various biomedical researches to clinics, agriculture, and allow you to rearrange genomic sequences, create cell lines and animal models to solve human diseases. This review emphasizes the characteristics, superiority, limitations, also whether each technology can be used in different biological systems and the potential application of these systems in the treatment of several human diseases.

A Gene Expression High-Throughput Screen (GE-HTS) for Coordinated Detection of Functionally Similar Effectors in Cancer

Genome-wide, loss-of-function screening can be used to identify novel vulnerabilities upon which specific tumor cells depend for survival. Functional Signature Ontology (FUSION) is a gene expression-based high-throughput screening (GE-HTS) method that allows researchers to identify functionally similar proteins, small molecules, and microRNA mimics, revealing novel therapeutic targets. FUSION uses cell-based high-throughput screening and computational analysis to match gene expression signatures produced by natural products to those produced by small interfering RNA (siRNA) and synthetic microRNA libraries to identify putative protein targets and mechanisms of action (MoA) for several previously undescribed natural products. We have used FUSION to screen for functional analogues to Kinase suppressor of Ras 1 (KSR1), a scaffold protein downstream of Ras in the Raf-MEK-ERK kinase cascade, and biologically validated several proteins with functional similarity to KSR1. FUSION incorporates bioinformatics analysis that may offer higher resolution of the endpoint readout than other screens which utilize Boolean outputs regarding a single pathway activation (i.e., synthetic lethal and cell proliferation). Challenges associated with FUSION and other high-content genome-wide screens include variation, batch effects, and controlling for potential off-target effects. In this review, we discuss the efficacy of FUSION to identify novel inhibitors and oncogene-induced changes that may be cancer cell-specific as well as several potential pitfalls within FUSION and best practices to avoid them.

Screening Cancer Immunotherapy: When Engineering Approaches Meet Artificial Intelligence

Immunotherapy is a class of promising anticancer treatments that has recently gained attention due to surging numbers of FDA approvals and extensive preclinical studies demonstrating efficacy. Nevertheless, further clinical implementation has been limited by high variability in patient response to different immunotherapeutic agents. These treatments currently do not have reliable predictors of efficacy and may lead to side effects. The future development of additional immunotherapy options and the prediction of patient-specific response to treatment require advanced screening platforms associated with accurate and rapid data interpretation. Advanced engineering approaches ranging from sequencing and gene editing, to tumor organoids engineering, bioprinted tissues, and organs-on-a-chip systems facilitate the screening of cancer immunotherapies by recreating the intrinsic and extrinsic features of a tumor and its microenvironment. High-throughput platform development and progress in artificial intelligence can also improve the efficiency and accuracy of screening methods. Here, these engineering approaches in screening cancer immunotherapies are highlighted, and a discussion of the future perspectives and challenges associated with these emerging fields to further advance the clinical use of state-of-the-art cancer immunotherapies are provided.

A review of CRISPR associated genome engineering: application, advances and future prospects of genome targeting tool for crop improvement

The Cas9 nuclease initiates double-stranded breaks at the target position in DNA, which are repaired by the intracellular restoration pathways to eliminate or insert pieces of DNA. CRISPR-Cas9 is proficient and cost-effective since cutting is guided by a piece of RNA instead of protein. Emphasis on this technology, in contrast with two recognized genome editing platforms (i.e., ZFNs and TALENs), is provided. This review evaluates the benefits of chemically synthesized gRNAs as well as the integration of chemical amendments to improve gene editing efficiencies. CRISPR is an indispensable means in biological investigations and is now as well transforming varied fields of biotechnology and agriculture. Recent advancement in targetable epigenomic-editing tools allows researchers to dispense direct functional and transcriptional significance to locus-explicit chromatin adjustments encompassing gene regulation and editing. An account of diverse sgRNA design tools is provided, principally on their target competence prediction model, off-target recognition algorithm, and generation of instructive annotations. The modern systems that have been utilized to deliver CRISPR-Cas9 in vivo and in vitro for crop improvement viz. nutritional enhancement, production of drought-tolerant and disease-resistant plants, are also highlighted. The conclusion is focused on upcoming directions, biosafety concerns, and expansive prospects of CRISPR technologies.

A Novel Screening Approach for the Dissection of Cellular Regulatory Networks of NF-κB Using Arrayed CRISPR gRNA Libraries

CRISPR/Cas9 is increasingly being used as a tool to prosecute functional genomic screens. However, it is not yet possible to apply the approach at scale across a full breadth of cell types and endpoints. In order to address this, we developed a novel and robust workflow for array-based lentiviral CRISPR/Cas9 screening. We utilized a β-lactamase reporter gene assay to investigate mediators of TNF-α-mediated NF-κB signaling. The system was adapted for CRISPR/Cas9 through the development of a cell line stably expressing Cas9 and application of a lentiviral gRNA library comprising mixtures of four gRNAs per gene. We screened a 743-gene kinome library whereupon hits were independently ranked by percent inhibition, Z' score, strictly standardized mean difference, and T statistic. A consolidated and optimized ranking was generated using Borda-based methods. Screening data quality was above acceptable limits (Z' ≥ 0.5). In order to determine the contribution of individual gRNAs and to better understand false positives and negatives, a subset of gRNAs, against 152 genes, were profiled in singlicate format. We highlight the use of known reference genes and high-throughput, next-generation amplicon and RNA sequencing to assess screen data quality. Screening with singlicate gRNAs was more successful than screening with mixtures at identifying genes with known regulatory roles in TNF-α-mediated NF-κB signaling and was found to be superior to previous RNAi-based methods. These results add to the available data on TNF-α-mediated NF-κB signaling and establish a high-throughput functional genomic screening approach, utilizing a vector-based arrayed gRNA library, applicable across a wide variety of endpoints and cell types at a genome-wide scale.

Delivering Robust Candidates to the Drug Pipeline through Computational Analysis of Arrayed CRISPR Screens

Genome-wide arrayed CRISPR screening is a powerful method for drug target identification as it enables exploration of the effect of individual gene perturbations using diverse highly multiplexed functional and phenotypic assays. Using high-content imaging, we can measure changes in biomarker expression, intracellular localization, and cell morphology. Here we present the computational pipeline we have developed to support the analysis and interpretation of arrayed CRISPR screens. This includes evaluating the quality of guide RNA libraries, performing image analysis, evaluating assay results quality, data processing, hit identification, ranking, visualization, and biological interpretation.

CRISPR Tools for Physiology and Cell State Changes: Potential of Transcriptional Engineering and Epigenome Editing

Given the large amount of genome-wide data that have been collected during the last decades, a good understanding of how and why cells change during development, homeostasis, and disease might be expected. Unfortunately, the opposite is true; triggers that cause cellular state changes remain elusive, and the underlying molecular mechanisms are poorly understood. Although genes with the potential to influence cell states are known, the historic dependency on methods that manipulate gene expression outside the endogenous chromatin context has prevented us from understanding how cells organize, interpret, and protect cellular programs. Fortunately, recent methodological innovations are now providing options to answer these outstanding questions, by allowing to target and manipulate individual genomic and epigenomic loci. In particular, three experimental approaches are now feasible due to DNA targeting tools, namely, activation and/or repression of master transcription factors in their endogenous chromatin context; targeting transcription factors to endogenous, alternative, or inaccessible sites; and finally, functional manipulation of the chromatin context. In this article, we discuss the molecular basis of DNA targeting tools and review the potential of these new technologies before we summarize how these have already been used for the manipulation of cellular states and hypothesize about future applications.

Arrayed CRISPR Screening Identifies Novel Targets That Enhance the Productive Delivery of mRNA by MC3-Based Lipid Nanoparticles

Modified messenger RNAs (mRNAs) hold great potential as therapeutics by using the body’s own processes for protein production. However, a key challenge is efficient delivery of therapeutic mRNA to the cell cytosol and productive protein translation. Lipid nanoparticles (LNPs) are the most clinically advanced system for nucleic acid delivery; however, a relatively narrow therapeutic index makes them unsuitable for many therapeutic applications. A key obstacle to the development of more potent LNPs is a limited mechanistic understanding of the interaction of LNPs with cells. To address this gap, we performed an arrayed CRISPR screen to identify novel pathways important for the functional delivery of MC3 lipid-based LNP encapsulated mRNA (LNP-mRNA). Here, we have developed and validated a robust, high-throughput screening–friendly phenotypic assay to identify novel targets that modulate productive LNP-mRNA delivery. We screened the druggable genome (7795 genes) and validated 44 genes that either increased (37 genes) or inhibited (14 genes) the productive delivery of LNP-mRNA. Many of these genes clustered into families involved with host cell transcription, protein ubiquitination, and intracellular trafficking. We show that both UDP-glucose ceramide glucosyltransferase and V-type proton ATPase can significantly modulate the productive delivery of LNP-mRNA, increasing and decreasing, respectively, with both genetic perturbation and by small-molecule inhibition. Taken together, these findings shed new light into the molecular machinery regulating the delivery of LNPs into cells and improve our mechanistic understanding of the cellular processes modulating the interaction of LNPs with cells.

A Whole Genome-Wide Arrayed CRISPR Screen in Primary Organ Fibroblasts to Identify Regulators of Kidney Fibrosis

Kidney fibrosis presents a hallmark of chronic kidney disease. With ever-increasing patient numbers and limited treatment options available, novel strategies for therapeutic intervention in kidney disease are warranted. Fibrosis commonly results from a wound healing response to repeated or chronic tissue damage, irrespective of the underlying etiology, and can occur in virtually any solid organ or tissue. In order to identify targets relevant for kidney fibrosis, we aimed to employ CRISPR screening in primary human kidney fibroblasts. We demonstrate that CRISPR technology can be applied in primary kidney fibroblasts and can furthermore be used to conduct arrayed CRISPR screening using a high-content imaging readout in a whole genome-wide manner. Hits coming out of this screen were validated using orthogonal approaches and present starting points for validation of novel targets relevant to kidney disease.

Multiparametric Assays for Accelerating Early Drug Discovery

Drug discovery campaigns are hampered by substantial attrition rates largely due to a lack of efficacy and safety reasons associated with candidate drugs. This is true in particular for genetically complex diseases, where insufficient knowledge of the modulatory actions of candidate drugs on targets and entire target pathways further adds to the problem of attrition. To better profile compound actions on targets, potential off-targets, and disease-linked pathways, new innovative technologies need to be developed that can elucidate the complex cellular signaling networks in health and disease. Here, we discuss progress in genetically encoded multiparametric assays and mass spectrometry (MS)-based proteomics, which both represent promising toolkits to profile multifactorial actions of drug candidates in disease-relevant cellular systems to promote drug discovery and personalized medicine.

A benchmark of algorithms for the analysis of pooled CRISPR screens

Genome-wide pooled CRISPR-Cas-mediated knockout, activation, and repression screens are powerful tools for functional genomic investigations. Despite their increasing importance, there is currently little guidance on how to design and analyze CRISPR-pooled screens. Here, we provide a review of the commonly used algorithms in the computational analysis of pooled CRISPR screens. We develop a comprehensive simulation framework to benchmark and compare the performance of these algorithms using both synthetic and real datasets. Our findings inform parameter choices of CRISPR screens and provide guidance to researchers on the design and analysis of pooled CRISPR screens.

Rapid identification of human mast cell degranulation regulators using functional genomics coupled to high-resolution confocal microscopy

Targeted functional genomics represents a powerful approach for studying gene function in vivo and in vitro. However, its application to gene expression studies in human mast cells has been hampered by low yields of human mast cell cultures and their poor transfection efficiency. We developed an imaging system in which mast cell degranulation can be visualized in single cells subjected to shRNA knockdown or CRISPR-Cas 9 gene editing. By using high resolution confocal microscopy and a fluorochrome-labeled avidin probe, one can directly assess the suppression of functional responses, i.e. degranulation, in single human mast cells. The elimination of a drug or marker selection step avoids the use of potentially toxic treatment procedures and the short hands-on time of the functional analysis step enables the high-throughput screening of shRNA or CRISPR-Cas9 constructs to identify genes that regulate human mast cell degranulation. The ability to analyse single cells significantly reduces the total number of cells required, and allows for the parallel visualization of the degranulation profile of both edited and non-edited mast cells, offering a consistent internal control not found in other protocols. Moreover, our protocol offers a flexible choice between RNA interference and CRISPR-Cas9 genome editing for perturbation of gene expression using our human mast cell single-cell imaging system. Perturbation of gene expression, acquisition of microscopy data, and image analysis can be completed within 5 days, requiring only standard laboratory equipment and expertise.

This protocol presents an an imaging system in which mast cell degranulation can be visualized in single cells subjected to shRNA knockdown or CRISPR-Cas 9 gene editing using high resolution confocal microscopy with a fluorochrome-labeled avidin probe.

A Universal, Genomewide GuideFinder for CRISPR/Cas9 Targeting in Microbial Genomes

The CRISPR/Cas system has significant potential to facilitate gene editing in a variety of bacterial species. CRISPR interference (CRISPRi) and CRISPR activation (CRISPRa) represent modifications of the CRISPR/Cas9 system utilizing a catalytically inactive Cas9 protein for transcription repression and activation, respectively. While CRISPRi and CRISPRa have tremendous potential to systematically investigate gene function in bacteria, few programs are specifically tailored to identify guides in draft bacterial genomes genomewide. Furthermore, few programs offer open-source code with flexible design parameters for bacterial targeting. To address these limitations, we created GuideFinder, a customizable, user-friendly program that can design guides for any annotated bacterial genome. GuideFinder designs guides from NGG protospacer-adjacent motif (PAM) sites for any number of genes by the use of an annotated genome and FASTA file input by the user. Guides are filtered according to user-defined design parameters and removed if they contain any off-target matches. Iteration with lowered parameter thresholds allows the program to design guides for genes that did not produce guides with the more stringent parameters, one of several features unique to GuideFinder. GuideFinder can also identify paired guides for targeting multiplicity, whose validity we tested experimentally. GuideFinder has been tested on a variety of diverse bacterial genomes, finding guides for 95% of genes on average. Moreover, guides designed by the program are functionally useful-focusing on CRISPRi as a potential application-as demonstrated by essential gene knockdown in two staphylococcal species. Through the large-scale generation of guides, this open-access software will improve accessibility to CRISPR/Cas studies of a variety of bacterial species.IMPORTANCE With the explosion in our understanding of human and environmental microbial diversity, corresponding efforts to understand gene function in these organisms are strongly needed. CRISPR/Cas9 technology has revolutionized interrogation of gene function in a wide variety of model organisms. Efficient CRISPR guide design is required for systematic gene targeting. However, existing tools are not adapted for the broad needs of microbial targeting, which include extraordinary species and subspecies genetic diversity, the overwhelming majority of which is characterized by draft genomes. In addition, flexibility in guide design parameters is important to consider the wide range of factors that can affect guide efficacy, many of which can be species and strain specific. We designed GuideFinder, a customizable, user-friendly program that addresses the limitations of existing software and that can design guides for any annotated bacterial genome with numerous features that facilitate guide design in a wide variety of microorganisms.

Application of CRISPR genetic screens to investigate neurological diseases

The adoption of CRISPR-Cas9 technology for functional genetic screens has been a transformative advance. Due to its modular nature, this technology can be customized to address a myriad of questions. To date, pooled, genome-scale studies have uncovered genes responsible for survival, proliferation, drug resistance, viral susceptibility, and many other functions. The technology has even been applied to the functional interrogation of the non-coding genome. However, applications of this technology to neurological diseases remain scarce. This shortfall motivated the assembly of a review that will hopefully help researchers moving in this direction find their footing. The emphasis here will be on design considerations and concepts underlying this methodology. We will highlight groundbreaking studies in the CRISPR-Cas9 functional genetics field and discuss strengths and limitations of this technology for neurological disease applications. Finally, we will provide practical guidance on navigating the many choices that need to be made when implementing a CRISPR-Cas9 functional genetic screen for the study of neurological diseases.

Chemogenetic interactions in human cancer cells

Chemogenetic profiling enables the identification of genes that enhance or suppress the phenotypic effect of chemical compounds. Using this approach in cancer therapies could improve our ability to predict the response of specific tumor genotypes to chemotherapeutic agents, thus accelerating the development of personalized drug therapy. In the not so distant past, this strategy was only applied in model organisms because there was no feasible technology to thoroughly exploit desired genetic mutations and their impact on drug efficacy in human cells. Today, with the advent of CRISPR gene-editing technology and its application to pooled library screens in mammalian cells, chemogenetic screens are performed directly in human cell lines with high sensitivity and specificity. Chemogenetic profiling provides insights into drug mechanism-of-action, genetic vulnerabilities, and resistance mechanisms, all of which will help to accurately deliver the right drug to the right target in the right patient while minimizing side effects.

Genome-wide CRISPR screening identifies new regulators of glycoprotein secretion

Background: The fundamental process of protein secretion from eukaryotic cells has been well described for many years, yet gaps in our understanding of how this process is regulated remain. Methods: With the aim of identifying novel genes involved in the secretion of glycoproteins, we used a screening pipeline consisting of a pooled genome-wide CRISPR screen, followed by secondary siRNA screening of the hits to identify and validate several novel regulators of protein secretion. Results: We present approximately 50 novel genes not previously associated with protein secretion, many of which also had an effect on the structure of the Golgi apparatus. We further studied a small selection of hits to investigate their subcellular localisation. One of these, GPR161, is a novel Golgi-resident protein that we propose maintains Golgi structure via an interaction with golgin A5. Conclusions: This study has identified new factors for protein secretion involved in Golgi homeostasis.

Genome-wide CRISPR screening identifies new regulators of glycoprotein secretion

Background: The fundamental process of protein secretion from eukaryotic cells has been well described for many years, yet gaps in our understanding of how this process is regulated remain.

Methods: With the aim of identifying novel genes involved in the secretion of glycoproteins, we used a screening pipeline consisting of a pooled genome-wide CRISPR screen, followed by secondary siRNA screening of the hits to identify and validate several novel regulators of protein secretion.

Results: We present approximately 50 novel genes not previously associated with protein secretion, many of which also had an effect on the structure of the Golgi apparatus. We further studied a small selection of hits to investigate their subcellular localisation. One of these, GPR161, is a novel Golgi-resident protein that we propose maintains Golgi structure via an interaction with golgin A5.

Conclusions: This study has identified new factors for protein secretion involved in Golgi homeostasis.

Identification of Novel Inhibitors of DLK Palmitoylation and Signaling by High Content Screening

After axonal insult and injury, Dual leucine-zipper kinase (DLK) conveys retrograde pro-degenerative signals to neuronal cell bodies via its downstream target c-Jun N-terminal kinase (JNK). We recently reported that such signals critically require modification of DLK by the fatty acid palmitate, via a process called palmitoylation. Compounds that inhibit DLK palmitoylation could thus reduce neurodegeneration, but identifying such inhibitors requires a suitable assay. Here we report that DLK subcellular localization in non-neuronal cells is highly palmitoylation-dependent and can thus serve as a proxy readout to identify inhibitors of DLK palmitoylation by High Content Screening (HCS). We optimized an HCS assay based on this readout, which showed highly robust performance in a 96-well format. Using this assay we screened a library of 1200 FDA-approved compounds and found that ketoconazole, the compound that most dramatically affected DLK localization in our primary screen, dose-dependently inhibited DLK palmitoylation in follow-up biochemical assays. Moreover, ketoconazole significantly blunted phosphorylation of c-Jun in primary sensory neurons subjected to trophic deprivation, a well known model of DLK-dependent pro-degenerative signaling. Our HCS platform is thus capable of identifying novel inhibitors of DLK palmitoylation and signalling that may have considerable therapeutic potential.

Using stem cell-derived neurons in drug screening for neurological diseases

Induced pluripotent stem cells and their derivatives have become an important tool for researching disease mechanisms. It is hoped that they could be used to discover new therapies by providing the most reliable and relevant human in vitro disease models for drug discovery. This review will summarize recent efforts to use stem cell-derived neurons for drug screening. We also explain the current hurdles to using these cells for high-throughput pharmaceutical screening and developments that may help overcome these hurdles. Finally, we critically discuss whether induced pluripotent stem cell-derived neurons will come to fruition as a model that is regularly used to screen for drugs to treat neurological diseases.

Functional Genomics via CRISPR-Cas

RNA-guided CRISPR (clustered regularly interspaced short palindromic repeat)-associated Cas proteins have recently emerged as versatile tools to investigate and engineer the genome. The programmability of CRISPR-Cas has proven especially useful for probing genomic function in high-throughput. Facile single-guide RNA library synthesis allows CRISPR-Cas screening to rapidly investigate the functional consequences of genomic, transcriptomic, and epigenomic perturbations. Furthermore, by combining CRISPR-Cas perturbations with downstream single-cell analyses (flow cytometry, expression profiling, etc.), forward screens can generate robust data sets linking genotypes to complex cellular phenotypes. In the following review, we highlight recent advances in CRISPR-Cas genomic screening while outlining protocols and pitfalls associated with screen implementation. Finally, we describe current challenges limiting the utility of CRISPR-Cas screening as well as future research needed to resolve these impediments. As CRISPR-Cas technologies develop, so too will their clinical applications. Looking ahead, patient centric functional screening in primary cells will likely play a greater role in disease management and therapeutic development.

CRISPR-Mediated Approaches to Regulate YAP/TAZ Levels

The advent of CRISPR has revolutionized genomic engineering, and harnessing its power to regulate levels of the transcriptional co-activators YAP and TAZ represents an exciting new opportunity in the field of Hippo signaling. Initially repurposed from the microbial immune system to perform highly specific gene knockouts, CRISPR technology has now been expanded to modulate the transcriptional activity of any gene of interest in mammalian systems. Here, we describe strategies to employ CRISPR to genetically knock out the genes encoding for YAP (YAP1) or TAZ (WWTR1) in mammalian cell lines, as well as briefly outline an approach for utilizing CRISPR to transcriptionally modulate YAP/TAZ levels.

Nanoliter Centrifugal Liquid Dispenser Coupled with Superhydrophobic Microwell Array Chips for High-Throughput Cell Assays

Microfluidic systems have been regarded as a potential platform for high-throughput screening technology in drug discovery due to their low sample consumption, high integration, and easy operation. The handling of small-volume liquid is an essential operation in microfluidic systems, especially in investigating large-scale combination conditions. Here, we develop a nanoliter centrifugal liquid dispenser (NanoCLD) coupled with superhydrophobic microwell array chips for high-throughput cell-based assays in the nanoliter scale. The NanoCLD consists of a plastic stock block with an array of drilled through holes, a reagent microwell array chip (reagent chip), and an alignment bottom assembled together in a fixture. A simple centrifugation at 800 rpm can dispense ~160 nL reagents into microwells in 5 min. The dispensed reagents are then delivered to cells by sandwiching the reagent chip upside down with another microwell array chip (cell chip) on which cells are cultured. A gradient of doxorubicin is then dispensed to the cell chip using the NanoCLD for validating the feasibility of performing drug tests on our microchip platform. This novel nanoliter-volume liquid dispensing method is simple, easy to operate, and especially suitable for repeatedly dispensing many different reagents simultaneously to microwells.

Aspergillus flavus Secondary Metabolites: More than Just Aflatoxins

Aspergillus flavus is best known for producing the family of potent carcinogenic secondary metabolites known as aflatoxins. However, this opportunistic plant and animal pathogen also produces numerous other secondary metabolites, many of which have also been shown to be toxic. While about forty of these secondary metabolites have been identified from A. flavus cultures, analysis of the genome has predicted the existence of at least 56 secondary metabolite gene clusters. Many of these gene clusters are not expressed during growth of the fungus on standard laboratory media. This presents researchers with a major challenge of devising novel strategies to manipulate the fungus and its genome so as to activate secondary metabolite gene expression and allow identification of associated cluster metabolites. In this review, we discuss the genetic, biochemical and bioinformatic methods that are being used to identify previously uncharacterized secondary metabolite gene clusters and their associated metabolites. It is important to identify as many of these compounds as possible to determine their bioactivity with respect to fungal development, survival, virulence and especially with respect to any potential synergistic toxic effects with aflatoxin.

High-Content Screening Approaches That Minimize Confounding Factors in RNAi, CRISPR, and Small Molecule Screening

Screening arrayed libraries of reagents, particularly small molecules began as a vehicle for drug discovery, but the in last few years it has become a cornerstone of biological investigation, joining RNAi and CRISPR as methods for elucidating functional relationships that could not be anticipated, and illustrating the mechanisms behind basic and disease biology, and therapeutic resistance. However, these approaches share some common challenges, especially with respect to specificity or selectivity of the reagents as they are scaled to large protein families or the genome. High-content screening (HCS) has emerged as an important complement to screening, mostly the result of a wide array of specific molecular events, such as protein kinase and transcription factor activation, morphological changes associated with stem cell differentiation or the epithelial-mesenchymal transition of cancer cells. Beyond the range of cellular events that can be screened by HCS, image-based screening introduces new processes for differentiating between specific and nonspecific effects on cells. This chapter introduces these complexities and discusses strategies available in image-based screening that can mitigate the challenges they can bring to screening.