Project description:BackgroundDNA methylation has widespread effects on gene expression during development. However, our ability to assign specific function to regions of DNA methylation is limited by the poor correlation between global patterns of DNA methylation and gene expression.ResultsHere, we utilize nuclease-deactivated Cas9 protein fused to repetitive peptide epitopes (SunTag) recruiting multiple copies of antibody-fused de novo DNA methyltransferase 3A (DNMT3A) (dCas9-SunTag-DNMT3A) to amplify the local DNMT3A concentration to methylate genomic sites of interest. We demonstrate that dCas9-SunTag-DNMT3A dramatically increases CpG methylation at the HOXA5 locus in human embryonic kidney (HEK293T) cells. Furthermore, using a single guide RNA, dCas9-SunTag-DNMT3A is able to methylate a 4.5-kb genomic region and repress HOXA5 gene expression. Reduced representation bisulfite sequencing and RNA-seq show that dCas9-SunTag-DNMT3A methylates regions of interest with minimal impact on the global DNA methylome and transcriptome.ConclusionsThis effective and precise tool enables site-specific manipulation of DNA methylation and may be used to address the relationship between DNA methylation and gene expression.
Project description:We demonstrate that dCas9-SunTag-DNMT3A dramatically increased CpG methylation at the HOXA5 locus in human embryonic kidney 293T cells (HEK293T). Furthermore, using a single sgRNA, dCas9-SunTag-DNMT3A was able to methylate a 4.5 kb genomic region and repress HOXA5 gene expression. Reduced representation bisulfite sequencing (RRBS) and RNA-seq showed that dCas9-SunTag-DNMT3A methylated regions of interest with minimal impact on the global DNA methylome and transcriptome.
Project description:We demonstrate that dCas9-SunTag-DNMT3A dramatically increased CpG methylation at the HOXA5 locus in human embryonic kidney 293T cells (HEK293T). Furthermore, using a single sgRNA, dCas9-SunTag-DNMT3A was able to methylate a 4.5 kb genomic region and repress HOXA5 gene expression. Reduced representation bisulfite sequencing (RRBS) and RNA-seq showed that dCas9-SunTag-DNMT3A methylated regions of interest with minimal impact on the global DNA methylome and transcriptome.
Project description:Here, we demonstrate that dCas9-SunTag-DNMT3A dramatically increased CpG methylation at the HOXA5 locus in human embryonic kidney 293T cells (HEK293T). Furthermore, using a single sgRNA, dCas9-SunTag-DNMT3A was able to methylate a 4.5 kb genomic region and repress HOXA5 gene expression. Reduced representation bisulfite sequencing (RRBS) and RNA-seq showed that dCas9-SunTag-DNMT3A methylated regions of interest with minimal impact on the global DNA methylome and transcriptome.
Project description:We demonstrate that dCas9-SunTag-DNMT3A dramatically increased CpG methylation at the HOXA5 locus in human embryonic kidney 293T cells (HEK293T). Furthermore, using a single sgRNA, dCas9-SunTag-DNMT3A was able to methylate a 4.5 kb genomic region and repress HOXA5 gene expression. Reduced representation bisulfite sequencing (RRBS) and RNA-seq showed that dCas9-SunTag-DNMT3A methylated regions of interest with minimal impact on the global DNA methylome and transcriptome.
Project description:Detection of DNA methylation in the genome has been possible for decades; however, the ability to deliberately and specifically manipulate local DNA methylation states in the genome has been extremely limited. Consequently, this has impeded our understanding of the direct effect of DNA methylation on transcriptional regulation and transcription factor binding in the native chromatin context. Thus, highly specific targeted epigenome editing tools are needed to address this. Recent adaptations of genome editing technologies, including fusion of the DNMT3A DNA methyltransferase catalytic domain to catalytically inactive Cas9 (dC9-D3A), have aimed to alter DNA methylation at desired loci. Here, we show that these tools exhibit consistent off-target DNA methylation deposition in the genome, limiting their capabilities to unambiguously assess the functional consequences of DNA methylation. To address this, we developed a modular dCas9-SunTag (dC9Sun-D3A) system that can recruit multiple DNMT3A catalytic domains to a target site for editing DNA methylation. dC9Sun-D3A is tunable, specific, and exhibits much higher induction of DNA methylation at target sites than the dC9-D3A direct fusion protein. Importantly, genome-wide characterization of dC9Sun-D3A binding sites and DNA methylation revealed minimal off-target protein binding and induction of DNA methylation with dC9Sun-D3A, compared to pervasive off-target methylation by dC9-D3A. Furthermore, we used dC9Sun-D3A to demonstrate the binding sensitivity to DNA methylation for CTCF and NRF1 in situ. Overall, this modular dC9Sun-D3A system enables precise DNA methylation deposition with the lowest off-target DNA methylation levels reported to date, allowing accurate functional determination of the role of DNA methylation at single loci.
Project description:Clustered regularly interspaced short palindromic repeats and CRISPR-associated proteins (CRISPR-Cas) has revolutionized genome editing and has great potential for many applications, such as correcting human genetic disorders. To increase the safety of genome editing applications, CRISPR-Cas may benefit from strict control over Cas enzyme activity. Previously, anti-CRISPR proteins and designed oligonucleotides have been proposed to modulate CRISPR-Cas activity. In this study, we report on the potential of guide-complementary DNA oligonucleotides as controlled inhibitors of Cas9 ribonucleoprotein complexes. First, we show that DNA oligonucleotides inhibit Cas9 activity in human cells, reducing both on- and off-target cleavage. We then used in vitro assays to better understand how inhibition is achieved and under which conditions. Two factors were found to be important for robust inhibition: the length of the complementary region and the presence of a protospacer adjacent motif-loop on the inhibitor. We conclude that DNA oligonucleotides can be used to effectively inhibit Cas9 activity both ex vivo and in vitro.
Project description:Eliminating or silencing a gene's level of activity is one of the classic approaches developmental biologists employ to determine a gene's function. A recently developed method of gene perturbation called CRISPR-Cas, which was derived from a prokaryotic adaptive immune system, has been adapted for use in eukaryotic cells. This technology has been established in several model organisms as a powerful and efficient tool for knocking out or knocking down the function of a gene of interest. It has been recently shown that CRISPR-Cas functions with fidelity and efficiency in Ciona robusta. Here, we show that in C. robusta CRISPR-Cas mediated genomic knock-ins can be efficiently generated. Electroporating a tissue-specific transgene driving Cas9 and a U6-driven gRNA transgene together with a fluorescent protein-containing homology directed repair (FP-HDR) template results in gene-specific patterns of fluorescence consistent with a targeted genomic insertion. Using the Tyrosinase locus to optimize reagents, we first characterize a new Pol III promoter for expressing gRNAs from the Ciona savignyi H1 gene, and then adapt technology that flanks gRNAs by ribozymes allowing cell-specific expression from Pol II promoters. Next, we examine homology arm-length efficiencies of FP-HDR templates. Reagents were then developed for targeting Brachyury and Pou4 that resulted in expected patterns of fluorescence, and sequenced PCR amplicons derived from single embryos validated predicted genomic insertions. Finally, using two differentially colored FP-HDR templates, we show that biallelic FP-HDR template insertion can be detected in live embryos of the F0 generation.
Project description:CRISPR-Cas is an efficient method for genome editing in organisms from bacteria to human cells. We describe a transgene-free method for CRISPR-Cas-mediated cleavage in nematodes, enabling RNA-homology-targeted deletions that cause loss of gene function; analysis of whole-genome sequencing indicates that the nuclease activity is highly specific.