Project description:CRISPR technology has demonstrated broad utility for controlling target gene expression. However, there remains a need for strategies capable of modulating expression via the precise editing of non-coding regulatory elements. Here we demonstrate that CRISPR base editors, a class of gene-modifying proteins capable of inducing single-base substitutions in DNA, can be harnessed to perturb target gene expression via the targeted mutagenesis of cis-acting sequences. Using the promoter region of the human huntingtin (HTT) gene as an initial target, we show that editing of the binding site for the transcription factor NF-κB led to a marked reduction in HTT gene expression. We find that these gene perturbations were persistent and specific, as a transcriptome-wide RNA-seq analysis revealed virtually no off-target effects. We further show that this base-editing platform could lower HTT in vivo, as its delivery to a mouse model of Huntington’s disease decreased HTT expression in striatal neurons, an outcome that we show also increased survival. Finally, we use this approach to target the amyloid-beta precursor protein, demonstrating that multiplexed editing of its promoter region could significantly perturb its expression, supporting the applicability of this method. These findings thus demonstrate the potential for base editors to regulate target gene expression.
Project description:Liver cancer susceptibility varies between strains of experimental animal models due to multiple genetic and epigenetic factors. We used DNase I hypersensitivity mapping and transcriptomic profiling to investigate cis-regulatory element and transcriptional perturbations associated with the early stages of phenobarbital (PB)-mediated liver tumor promotion in susceptible versus resistant mouse strains (B6C3F1 versus C57BL/6).
Project description:Adenine and cytosine base editors (ABEs and CBEs) represent a new genome editing technology that allows the programmable installation of A-to-G or C-to-T alterations on DNA. We engineered Streptococcus pyogenes Cas9-based adenine and cytosine base editor (SpACE) that enables efficient simultaneous introduction of A-to-G and C-to-T substitutions in the same base editing window on DNA.
Project description:RNA base editing applies endogenous or engineered adenosine deaminases to introduce adenosine-to-inosine changes into a target RNA in a highly programmable manner. Recently, notable success was achieved for the repair of disease-causing guanosine-to-adenosine mutations by means of RNA base editing. Here, we propose that RNA base editing could be broadly applied to perturb protein function by removal of regulatory sites of post-translational modification (PTM), like phosphorylation and/or acetylation sites. We demonstrate the feasibility of PTM interference (PTMi) on more than 70 PTM sites in various signaling proteins and identify key determinants for high editing efficiency and potent down-stream effects. Specifically, we demonstrate both negative and positive regulation of the JAK/STAT pathway by PTMi. To identify potent regulatory sites for PTMi, we applied an improved version of the SNAP-ADAR tool, which achieved high editing efficiency over a broad codon scope with tight control of bystander editing. The transient nature of RNA base editing enables the fast, dose-dependent (thus partial) and reversible manipulation of PTM sites, which is a key advantage over DNA editing approaches, where genetic compensation or lethality can conceal a phenotype. In summary, PTM interference might become a valuable field of application of RNA base editing in basic biology and medicine.
Project description:CRISPR tiling screens have advanced the identification and characterization of regulatory sequences but are limited by low resolution arising from the indirect readout of editing via guide RNA sequencing. This study introduces CRISPR-CLEAR, an end-to-end experimental assay and computational pipeline, which leverages targeted sequencing of CRISPR-introduced alleles at the endogenous target locus following dense base-editing mutagenesis. This approach enables the dissection of regulatory elements at nucleotide resolution, facilitating a direct assessment of genotype-phenotype effects.