Project description:RNA Sequencing of H1 WT hESCs, H1 QSER1 KO hESCs, H1 TET1 KO hESCs, H1 QSER1/TET1 DKO hESCs, WT Day10 embryoid bodies (EBs), QSER1 KO Day10 EBs, TET1 KO Day10 EBs, QSER1/TET1 DKO Day10 EBs, WT pancreatic progenitors (PP1), QSER1 KO PP1, TET1 KO PP1, and QSER1/TET1 DKO PP1. DNA methylation is essential to mammalian development, and dysregulation can cause serious pathological conditions. Key enzymes responsible for deposition and removal of DNA methylation are known, but how they cooperate to tightly regulate the methylation landscape remains a central question. Utilizing a knockin DNA methylation reporter, we performed a genome-wide CRISPR/Cas screen in human embryonic stem cells to discover DNA methylation regulators. The top screen hit was an uncharacterized gene QSER1, which proved to be a key guardian of bivalent promoters and poised enhancers of developmental genes, especially those residing in DNA methylation valleys (or canyons). We further demonstrate cooperation of QSER1 and TET1 through genetic and biochemical interactions to inhibit DNMT3-mediated de novo methylation and safeguard developmental programs.
Project description:The TET enzymes oxidize 5-methylcytosine to 5-hydroxymethylcytosine, which can lead to DNA demethylation. However, direct connections between TET-mediated DNA demethylation and transcriptional output are difficult to establish due to challenges of distinguishing global versus locus-specific effects. Here we show that TET1/2/3 triple knockout (TKO) human embryonic stem cells (hESCs) exhibit preferential hypermethylation at bivalent promoters without corresponding gene expression changes in undifferentiated hESCs. In the absence of the TET proteins, abnormal accumulation of DNMT3B at bivalent promoters results in hypermethylation and impaired gene activation upon differentiation. Broadly, the competitive balance between the TET proteins and de novo methyltransferases at bivalent promoters could facilitate rapid changes of their methylation state to either activate or silence transcription in a cell-lineage and gene dependent manner.
Project description:The TET enzymes oxidize 5-methylcytosine to 5-hydroxymethylcytosine, which can lead to DNA demethylation. However, direct connections between TET-mediated DNA demethylation and transcriptional output are difficult to establish due to challenges of distinguishing global versus locus-specific effects. Here we show that TET1/2/3 triple knockout (TKO) human embryonic stem cells (hESCs) exhibit preferential hypermethylation at bivalent promoters without corresponding gene expression changes in undifferentiated hESCs. In the absence of the TET proteins, abnormal accumulation of DNMT3B at bivalent promoters results in hypermethylation and impaired gene activation upon differentiation. Broadly, the competitive balance between the TET proteins and de novo methyltransferases at bivalent promoters could facilitate rapid changes of their methylation state to either activate or silence transcription in a cell-lineage and gene dependent manner.
Project description:The TET enzymes oxidize 5-methylcytosine to 5-hydroxymethylcytosine, which can lead to DNA demethylation. However, direct connections between TET-mediated DNA demethylation and transcriptional output are difficult to establish due to challenges of distinguishing global versus locus-specific effects. Here we show that TET1/2/3 triple knockout (TKO) human embryonic stem cells (hESCs) exhibit preferential hypermethylation at bivalent promoters without corresponding gene expression changes in undifferentiated hESCs. In the absence of the TET proteins, abnormal accumulation of DNMT3B at bivalent promoters results in hypermethylation and impaired gene activation upon differentiation. Broadly, the competitive balance between the TET proteins and de novo methyltransferases at bivalent promoters could facilitate rapid changes of their methylation state to either activate or silence transcription in a cell-lineage and gene dependent manner.