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Genome-wide Programmable Transcriptional Memory by CRISPR-based Epigenome Editing

ABSTRACT: General approaches for heritably altering gene expression would enable many discovery and therapeutic efforts. Here, we present CRISPRoff— a programmable epigenetic memory writer consisting of a single dead Cas9 fusion protein that establishes DNA methylation and repressive histone modifications. Transient CRISPRoff expression initiates highly specific DNA methylation and gene repression that is maintained through cell division and differentiation of stem cells to neurons. Pairing CRISPRoff with genome-wide screens and analysis of chromatin marks enabled us to explore the rules for heritable silencing. We identify sgRNAs capable of silencing the large majority of genes including those lacking canonical CpG islands (CGIs) and reveal a wide targeting window extending beyond annotated CGIs. Our finding that targeted DNA methylation outside of CGIs leads to memorized gene silencing expands the canonical model of methylation-based silencing and broadly enables diverse applications including genome-wide screens, multiplexed cell engineering, enhancer silencing, and mechanistic exploration of epigenetic inheritance.

ORGANISM(S): Homo sapiens

PROVIDER: GSE168012 | GEO | 2021/04/12

REPOSITORIES: GEO

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Project description:A large-scale characterization of the methylation states of candidate CpG islands (CGIs) throughout the gastric cancer methylome has not previously been conducted. Genome-wide DNA methylation profiles were compared between 4 metastatic and 4 non-metastatic gastric carcinomas (GCs) and their surgical margins (SMs). The GC genome showed significantly higher proportions of hypomethylation in the promoter and exon-1 regions, as well as increased hypermethylation of intragenic fragments when compared to SMs. Differential methylation was observed in CGIs near transcription start sites of 546 genes between GCs and SMs, and 601 genes between metastatic and non-metastatic GCs. From the list of differentially methylated CGIs, 68 candidate genes and 10 known tumor-related genes were selected for further characterization based on their known molecular function using DHPLC. Significant differential methylation was validated in the CGIs of 15 genes between GCs and SMs (Ps<0.05) and confirmed using bisulfite-sequencing. These genes include BMP3, BNIP3, CDKN2A, ECEL1, ELK1, GFRA1, HOXD10, KCNH1, PSMD10, PTPRT, SIGIRR, SRF, TBX5, TFPI2, and ZNF382. Hypomethylation of CGIs correlated with up-regulation of GFRA1 expression in GCs, while hypermethylation of other genes inactivated their transcription. Most importantly, prevalence of GFRA1, SRF, and ZNF382 methylation alterations were inversely and coordinately associated with GC metastasis and the patients’ overall survival throughout discovery and testing cohorts in China as well as independent validation cohorts in Japan and Korea. In conclusion, methylation changes in the CGIs of 15 genes correlated strongly with GC development. GFRA1 hypomethylation and SRF and ZNF382 hypermethylation are potential synergistic biomarkers for the prediction of GC metastasis. To identify differential methylation of CGIs related to GC development and metastasis, genome-wide DNA methylation changes in 8 pairs of GC and SM samples were analysed using the MCAM assay with a 99K custom-designed Agilent oligonucleotide microarray composed of 99,027 probes targeting 6,177 unique protein-coding genes containing at least two methylation-sensitive/insensitive SmaI/ XmaI restriction sites (CCC|GGG/ C|CmCGGG) as described in Shen et al, PLoS Genet 3, 2023-2036 (2007).

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Genome-wide Programmable Transcriptional Memory by CRISPR-based Epigenome Editing

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