December 12, 2017
5 min read
CRISPR Screening sgRNA Libraries Made Easy
Planning an efficient CRISPR screen starts with the design of sgRNA libraries targeting the genes or loci of interest.
Use of CRISPR genome editing technology has grown exponentially over the last few years due to its ease of use, relatively low cost, and the speed and efficiency at which this system is able to introduce changes to the genome. CRISPR systems are now widely used across a diverse set of fields including gene therapy, functional genomics, agricultural biotech, and oncology research.
Planning an efficient CRISPR screen starts with the design of sgRNA libraries targeting the genes or loci of interest. Oligonucleotide pools corresponding to the sgRNA design are then synthesized, and either cloned into vectors to express the sgRNAs, or transcribed into RNA for transfection in the cell system where the screen will be conducted.
Twist Bioscience and Desktop Genetics have recently announced a partnership to provide integrated CRISPR library design and synthesis services to help researchers perform better CRISPR screens and accelerate their research with gene editing. This partnership provides CRISPR screeners with access to Desktop Genetics’ precision CRISPR design capabilities, and Twist Bioscience’s highly scalable DNA synthesis platform, enabling highly efficient CRISPR screening workflows for any experimental goal in any life science field.
With CRISPR sgRNA design dogma evolving regularly due to updates and improvements to the design programs being published, purchasing an “off the shelf” library can be a difficult choice. By the time these catalog libraries become available, the CRISPR field has moved on to newer sgRNA design methods.
Desktop Genetics solves this problem by offering custom sgRNA library design services that are optimized for each experiment, and are kept up to date with the latest design parameters from the literature. Their bioinformaticians can identify guides with the highest on-target activity while also carrying out robust off-target prediction, investigation of other experimentally validated design parameters, including sequence composition (such as GC%, homopolymeric stretches, and presence of SNPs), and specifically targeting functional domains of encoded proteins. Their philosophy is further guided by next-generation sequencing (NGS) and machine-learning tools. As such, they can design a sgRNA screening library that is built around your model organism or cell line, your targets, and your experimental needs. No CRISPR application is beyond their capabilities, and they can create knockout, CRISPRi, CRISPRa, and epigenetic CRISPR libraries, for loss-of-function, target discovery, target validation and other genomic screens in any cell line.
Following the design of sgRNA libraries, the next step in the CRISPR screening workflow is the synthesis of oligo pools that represent the sequences in the guide RNA library. Inherent shortcomings in traditional DNA synthesis methods such as limited throughput, high error rates, and non-uniform representation of each oligo sequence in the pool have previously limited CRISPR-based functional genomic screens.
The silicon-based DNA synthesis platform developed by Twist Bioscience has addressed all of these limitations. This technology enables maximized CRISPR screening efficiency and precision gene editing through synthesis of hundreds of thousands of unique oligonucleotide sequences per run, industry-leading low synthesis error rates, and uniform synthesis of all oligo sequences in the library. Increased DNA synthesis capacity allows larger and more complex screening libraries, while highly accurate synthesis ensures targeting specificity and high uniformity reduces bias in the screen.
To learn more about how the partnership between Desktop Genetics and Twist Bioscience is improving CRISPR screens, check out our webinar “Think Big, Screen Once: Genome-Scale Editing with Custom CRISPR Libraries”, hosted by Front Line Genomics, which is available to watch any time on-demand. Click here to watch now.
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