Journal: Nucleic Acids Research
Article Title: Optimized CRISPR-Cas9 system for efficient engineering of ecDNA in cancer cells
doi: 10.1093/nar/gkag005
Figure Lengend Snippet: Application of the safeguard sgRNA system in ecDNA-positive CORL23 cells. ( A ) AmpliconArchitect analysis showing the presence of ecDNA structures involving the MYC and PVT1 loci in CORL23 cells.( B ) IGV snapshot showing genome sequence profiles at the MYC and PVT1 loci. ( C ) Representative FISH images of CORL23 cells using an MYC locus probe (red) together with a chromosome 8 probe (green; control for the MYC -containing chromosome). Two representative single cells with different MYC ecDNA copy numbers are shown. Scale bar, 10 µm. ( D ) Schematic illustration of the proposed molecular mechanism by which safeguard sgRNAs fine-tune Cas9 activity. Cytosine extensions decrease Cas9 activity and attenuate Cas9-mediated DNA cleavage via multiple mechanisms, including reduced sgRNA synthesis and impaired target loading efficiency of Cas9–sgRNA RNP complexes (left). When using potent sgRNAs, [C]-extended sgRNAs exhibited decreased bi-allelic indels on chromosomal targets and increased mono-allelic indels in a length-dependent manner (right). This figure was adapted from Kawamata et al. , licensed under the CC BY 4.0. ( E ) Schematic of all-in-one CRISPR plasmids expressing standard and safeguard sgRNAs. ( F ) Western blot analysis of FLAG-tagged Cas9 proteins expressed from the indicated all-in-one plasmids in CORL23 cells. ( G ) Quantification of sgRNA expression levels by RT-qPCR. Left, normalized expression values; right, normalized values multiplied by 1000 and log 2 -transformed. Data represent mean ± SD for n = 3 technical replicates. Statistical significance was assessed using a two-sided Student’s t -test.
Article Snippet: Tracking of indels by decomposition (TIDE) analysis ( https://tide.nki.nl ) was performed using Sanger sequencing traces generated from target-specific PCR products by Eurofins [ ].
Techniques: Sequencing, Control, Activity Assay, CRISPR, Expressing, Western Blot, Quantitative RT-PCR, Transformation Assay