While the catalog of mammalian transcripts and their expression levels in different cell types and disease states is rapidly expanding, our understanding of transcript function lags behind. Authors present a robust technology enabling systematic investigation of the cellular consequences of repressing or inducing individual transcripts. They identify rules for specific targeting of transcriptional repressors (CRISPRi), typically achieving 90%–99% knockdown with minimal off-target effects, and activators (CRISPRa) to endogenous genes via endonuclease-deficient Cas9. Together they enable modulation of gene expression over a ∼1,000-fold range. Using these rules, researchers construct genome-scale CRISPRi and CRISPRa libraries, each of which they validate with two pooled screens. Growth-based screens identify essential genes, tumor suppressors, and regulators of differentiation. Screens for sensitivity to a cholera-diphtheria toxin provide broad insights into the mechanisms of pathogen entry, retrotranslocation and toxicity. These results establish CRISPRi and CRISPRa as powerful tools that provide rich and complementary information for mapping complex pathways.
Reference:Luke A. Gilbert, Max A. Horlbeck, Britt Adamson, Jacqueline E. Villalta, Yuwen Chen, Evan H. Whitehead, Carla Guimaraes, Barbara Panning, Hidde L. Ploegh, Michael C. Bassik, Lei S. Qi, Martin Kampmann, Jonathan S. Weissman, Genome-Scale CRISPR-Mediated Control of Gene Repression and Activation, Cell, Available online 9 October 2014, ISSN 0092-8674, http://dx.doi.org/10.1016/j.cell.2014.09.029.
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