http://www.cell.com/article/S0092867421014847/pdf

Engineered virus-like particles for efficient in vivo delivery of therapeutic proteins

The CRISPR-Cas toolbox and gene editing technologies

Therapeutic in vivo delivery of gene editing agents

CRISPR screens are a powerful source of biological discovery, enabling the unbiased interrogation of gene function in a wide range of applications and species. In pooled CRISPR screens, various genetically encoded perturbations are introduced into pools of cells. The targeted cells proliferate under a biological challenge such as cell competition, drug treatment or viral infection. Subsequently, the perturbation-induced effects are evaluated by sequencing-based counting of the guide RNAs that specify each perturbation. The typical results of such screens are ranked lists of genes that confer sensitivity or resistance to the biological challenge of interest. Contributing to the broad utility of CRISPR screens, adaptations of the core CRISPR technology make it possible to activate, silence or otherwise manipulate the target genes. Moreover, high-content read-outs such as single-cell RNA sequencing and spatial imaging help characterize screened cells with unprecedented detail. Dedicated software tools facilitate bioinformatic analysis and enhance reproducibility. CRISPR screening has unravelled various molecular mechanisms in basic biology, medical genetics, cancer research, immunology, infectious diseases, microbiology and other fields. This Primer describes the basic and advanced concepts of CRISPR screening and its application as a flexible and reliable method for biological discovery, biomedical research and drug development — with a special emphasis on high-content methods that make it possible to obtain detailed biological insights directly as part of the screen. CRISPR screening is a high-throughput approach for identifying genes, pathways and mechanisms involved in a given phenotype or biological process. High-content read-outs of these screens, such as imaging and single-cell sequencing techniques, have further broadened its applicability. This Primer by Bock et al. describes the main concepts of CRISPR screening and gives examples of its application as a method for biological discovery, with a focus on the use of high-content read-outs. 

/pdf/high-content-crispr-screening-i8cufnnq.pdf

High-content CRISPR screening

Mapping the genetic landscape of DNA double-strand break repair.

Enhanced prime editing systems by manipulating cellular determinants of editing outcomes

Neuromesodermal progenitors represent a unique, bipotent population of progenitors residing in the tail bud of the developing embryo, which give rise to the caudal spinal cord cell types of neuroectodermal lineage as well as the adjacent paraxial somite cell types of mesodermal origin. With the advent of stem cell technologies, including induced pluripotent stem cells (iPSCs), the modeling of rare genetic disorders can be accomplished in vitro to interrogate cell‐type specific pathological mechanisms in human patient conditions. Stem cell‐derived models of neuromesodermal progenitors have been accomplished by several developmental biology groups; however, most employ a 2D monolayer format that does not fully reflect the complexity of cellular differentiation in the developing embryo. This article presents a dynamic 3D combinatorial method to generate robust populations of human pluripotent stem cell‐derived neuromesodermal organoids with multi‐cellular fates and regional identities. By utilizing a dynamic 3D suspension format for the differentiation process, the organoids differentiated by following this protocol display a hallmark of embryonic development that involves a morphological elongation known as axial extension. Furthermore, by employing a combinatorial screening assay, we dissect essential pathways for optimally directing the patterning of pluripotent stem cells into neuromesodermal organoids. This protocol highlights the influence of timing, duration, and concentration of WNT and fibroblast growth factor (FGF) signaling pathways on enhancing early neuromesodermal identity, and later, downstream cell fate specification through combined synergies of retinoid signaling and sonic hedgehog activation. Finally, through robust inhibition of the Notch signaling pathway, this protocol accelerates the acquisition of terminal cell identities. This enhanced organoid model can serve as a powerful tool for studying normal developmental processes as well as investigating complex neurodevelopmental disorders, such as neural tube defects. © 2022 Wiley Periodicals LLC.

Cidi Chen

Papers

Enhanced prime editing systems by manipulating cellular determinants of editing outcomes

Dynamic 3D Combinatorial Generation of hPSC‐Derived Neuromesodermal Organoids With Diverse Regional and Cellular Identities