Project description:As a potent and accurate genome-editing tool, CRISPR-Cas9 has been widely used in biomedical research and evaluated as gene therapy in treating human diseases. Although distinct engineered Cas9s, dCas9s and additional endonucleases have been identified, as these bacterial enzymes do not naturally express in mammalian cells, whether and how bacterial Cas9 proteins are regulated by mammalian hosts remains poorly understood. Here, we identified Keap1 as an endogenous E3 ligase that targets Cas9/dCas9/Fanzor1 for ubiquitination and degradation. Cas9-“ETGE” mutants evading Keap1 recognition displayed enhanced gene editing ability in cells. dCas9-“ETGE” mutants displayed extended protein half-life on chromatin, leading to significantly improved CRISPa and CRISPRi efficacy. Cas9 binding to Keap1 also inactivate Keap1 function via competing with Keap1 substrates or binding partners, while engineered Cas9 mutants showed less perturbation. Thus, our study reveals a mammalian specific Cas9 regulation and provides new Cas9 designs not only with enhanced gene regulatory capacity but also with minimal effects on disrupting endogenous Keap1 signaling.
Project description:we performed lentiviral CRISPR interference (CRISPRi) by recruiting dCas9 fused with the KRAB domain to the CSMD1 enhancer (fam3) in the neuronal precursor cell line – Lund human mesencephalic (LUHMES). Given that the expression of CSMD1 was not detectable in LUHMES cells we differentiated these cells into neurons. Differentiated neurons with CRISPRi of CSMD1 enhancer showed significantly higher expression of CSMD1 than control.
Project description:Comparisons of molecular phenotypes across primates provide unique information to understand human biology and evolution and single-cell RNA-seq CRISPR interference screens are a powerful approach to analyze them. Here, we generate and validate three human, three gorilla and two cynomolgus iPS cell lines that carry a dox-inducible KRAB-dCas9 construct in the AAVS1 locus. We show that despite variable expression levels of KRAB-dCas9 among lines, comparable downregulation of target genes and comparable phenotypic effects are observed in a single-cell RNA-seq CRISPR interference screen. Hence, we provide valuable resources for performing and further extending CRISPRi screens in human and non-human primates.
Project description:Comparisons of molecular phenotypes across primates provide unique information to understand human biology and evolution and single-cell RNA-seq CRISPR interference screens are a powerful approach to analyze them. Here, we generate and validate three human, three gorilla and two cynomolgus iPS cell lines that carry a dox-inducible KRAB-dCas9 construct in the AAVS1 locus. We show that despite variable expression levels of KRAB-dCas9 among lines, comparable downregulation of target genes and comparable phenotypic effects are observed in a single-cell RNA-seq CRISPR interference screen. Hence, we provide valuable resources for performing and further extending CRISPRi screens in human and non-human primates.
Project description:CRISPR interference (CRISPRi) is a powerful new tool used in different organisms that provides a fast, specific, and reliable way to knockdown gene expression. Caulobacter crescentus is a well-studied model bacterium, and although a variety of genetic tools have been developed, it currently takes several weeks to delete or deplete individual genes, which significantly limits genetic studies. Here, we optimized a CRISPRi approach to specifically downregulate the expression of genes in C. crescentus. Although the Streptococcus pyogenes CRISPRi system commonly used in other organisms does not work efficiently in Caulobacter, we demonstrate that a catalytically-dead version of Cas9 (dCas9) derived from the type II CRISPR3 module of Streptococcus thermophilus or from Streptococcus pasteurianus can each be effectively used in Caulobacter. We show that these CRISPRi systems can be used to rapidly and inducibly deplete ctrA or gcrA, two essential well-studied genes in Caulobacter, in either asynchronous or synchronized populations of cells. Additionally, we demonstrate the ability to multiplex CRISPRi-based gene knockdowns, opening new possibilities for systematic genetic interaction studies in Caulobacter.
Project description:CRISPR interference (CRISPRi) genetic screens use programmable repression of gene expression to systematically explore questions in cell biology and genetics. However, wider adoption of CRISPRi screening has been constrained by the large size of single guide RNA (sgRNA) libraries and lack of consensus on the choice of CRISPRi effector proteins. Here, we address these challenges to present next-generation CRISPRi sgRNA libraries and effectors. First, we combine empiric sgRNA selection with a dual sgRNA library design to generate an ultra-compact, highly active CRISPRi sgRNA library. Next, we rigorously compare CRISPRi effectors to show that the recently published Zim3-dCas9 provides an optimal balance between strong on-target knockdown and minimal nonspecific effects on cell growth or the transcriptome. Finally, we engineer a suite of cell lines which stably express Zim3-dCas9 and demonstrate robust on-target knockdown across these cell lines. Our results and publicly available reagents establish best practices for CRISPRi genetic screening.
Project description:Infinium MethylationEPIC (850K) BeadChip data for wildtype SUM159 cells (2 replicates), SUM159 cells transfected with plV-KRAB (dCas9 CRISPRi system; 3 replicates), and SUM159 cells transfected with dCas9-KRAB and 4 targeting gRNAs against the ZEB1 promoter (3 replicates)
