Project description:The ability to perturb genes in human cells is crucial for elucidating gene function and holds great potential for finding therapeutic targets for diseases such as cancer. To extend the catalog of human core and context- dependent fitness genes, we have developed a high-complexity second-generation genome-scale CRISPR-Cas9 gRNA library and applied it to fitness screens in five human cell lines. Using an improved Bayesian analytical approach, we consistently discover 5-fold more fitness genes than were previously observed. We present a list of 1,580 human core fitness genes and describe their general properties. Moreover, we demonstrate that context-dependent fitness genes accurately recapitulate pathway-specific genetic vulnerabilities induced by known oncogenes and reveal cell-type-specific dependencies for specific receptor tyrosine kinases, even in oncogenic KRAS backgrounds. Thus, rigorous identification of human cell line fitness genes using a high-complexity CRISPR-Cas9 library affords a high-resolution view of the genetic vulnerabilities of a cell. Additional data can be found at tko.ccbr.utoronto.ca RNAseq of five human cell lines with Cas9 knock-ins.
Project description:<p>Due to the paucity of patient derived models in rare cancers, identification of therapeutic targets remains challenging. We developed a patient derived model, CLF-PED-015-T, from a patient with an undifferentiated sarcoma. From this model, we performed pooled RNAi and CRISPR-Cas9 negative selection screens and integrated that with a small molecule screen. Integration of these data identified CDK4 and XPO1 as potential therapeutic targets.</p>
Project description:Uncovering the genetic basis of molecular processes is essential for understanding a broad range of biological phenomena. CRIPSR-Cas9 approaches enable this discovery through programable and systematic profiling of regulatory genes underlying diverse cellular behaviors. A key challenge for dissecting genetic networks is expanding CRISPR-based screens to interrogate specific phenotypes with high precision. Here, we use a quantitative, sequencing-based CRISPRi platform to enhance the scope and sensitivity of genome-wide screens. We first systematically explore how technical variations distort guide effects and correct for these factors by using RNA reporters and normalizers expressed from closely matched promoters. We then combine this platform with a recombinase-based integration system to interrogate protein and RNA-level phenotypes. We find our approach accurately captures known regulators of protein or RNA quality control with high accuracy and minimal background. These barcode-based CRISPR systems provide a powerful and generalizable platform for dissecting critical cellular regulatory pathways.
Project description:Cas12a CRISPR technology, unlike Cas9, allows for multiplexing guide RNAs from a single transcript, simplifying combinatorial perturbations. While Cas12a has been implemented for multiplexed knockout genetic screens, it has yet to be optimized for CRISPR activation (CRISPRa) screens in human cells. Here we develop a new Cas12a-based transactivation domain (TAD) recruitment system using the ALFA nanobody and demonstrate simultaneous activation of up to four genes. We screen a genome-wide library to identify modulators of growth and MEK inhibition, and we compare these results to those obtained with open reading frame (ORF) overexpression and Cas9-based CRISPRa. We find that the activity of multiplexed arrays is largely predictable from the best-performing guide and we provide criteria for selecting active guides. We anticipate that these results will greatly accelerate the exploration of gene function and combinatorial phenotypes at scale.
Project description:Cas12a CRISPR technology, unlike Cas9, allows for multiplexing guide RNAs from a single transcript, simplifying combinatorial perturbations. While Cas12a has been implemented for multiplexed knockout genetic screens, it has yet to be optimized for CRISPR activation (CRISPRa) screens in human cells. Here we develop a new Cas12a-based transactivation domain (TAD) recruitment system using the ALFA nanobody and demonstrate simultaneous activation of up to four genes. We screen a genome-wide library to identify modulators of growth and MEK inhibition, and we compare these results to those obtained with open reading frame (ORF) overexpression and Cas9-based CRISPRa. We find that the activity of multiplexed arrays is largely predictable from the best-performing guide and we provide criteria for selecting active guides. We anticipate that these results will greatly accelerate the exploration of gene function and combinatorial phenotypes at scale.
Project description:Here we apply integrated epigenomic and transcriptomic profiling to uncover super-enhancer heterogeneity between breast cancer subtypes, and provide clinically relevant biological insights towards TNBC. Using CRISPR/Cas9-mediated gene editing, we identify genes that are specifically regulated by TNBC-specific super-enhancers, including FOXC1 and MET, thereby unveiling a mechanism for specific overexpression of the key oncogenes in TNBC. We also identify ANLN as a novel TNBC-specific gene regulated by super-enhancer. Our studies reveal a TNBC-specific epigenomic landscape, contributing to the dysregulated oncogene expression in breast tumorigenesis.