Tet1 and Tet2 Regulate 5-Hydroxymethylcytosine Production and Cell Lineage Specification in Mouse Embryonic Stem Cells

Abstract

SUMMARY TET-family enzymes convert 5-methylcytosine (5mC) to 5-hydroxymethylcytosine (5hmC) in DNA. Here we show that Tet1 and Tet2 are Oct4-regulated enzymes that together sustain 5hmC in mouse embryonic stem (ES) cells, and are induced concomitantly with 5hmC during reprogramming of fibroblasts to induced pluripotent stem cells. ES cells depleted of Tet1 by RNAi show diminished expression of the Nodal antagonist Lefty1, and display hyperactive Nodal signalling and skewed differentiation into the endoderm-mesoderm lineage in embryoid bodies in vitro. In Fgf4- and heparin-supplemented culture conditions, Tet1-depleted ES cells activate the trophoblast stem cell lineage determinant Elf5 and can colonize the placenta in mid-gestation embryo chimeras. Consistent with these findings, Tet1-depleted ES cells form aggressive hemorrhagic teratomas with increased endoderm, reduced neuroectoderm and ectopic appearance of trophoblastic giant cells. Thus 5hmC is a novel epigenetic modification associated with the pluripotent state, and Tet1 functions to regulate the lineage differentiation potential of ES cells.

Nucleosome positioning changes during human embryonic stem cell differentiation

“…48 Notably, similar to our histone and DNA methylation findings, [16][17][18][19][20][21][22][23] our NP study indicates the uniqueness of hESC chromatin. At promoters and other notable genic sites, nucleosome occupany shows a stronger correlation with transcript abundance but is less influenced by the sequence content in hESC than its differenciated products.…”

“…[5][6][7][8][9][10][11][12][13][14][15] Indeed, studies have shown that hESCs bear unique chromatin composition compared to somatic cells, including prevalent bivalent histone modifications and DNA hydroxymethylation. [16][17][18][19][20][21][22][23] Additionally, changes in chromatin architecture, DNA methylation, and histone modification occur frequently and extensively throughout the course of differentiation. [5][6][7][8]13,17,18,21,22,24 Nucleosomes are the basic unit of chromatin.…”

“…[16][17][18][19][20][21][22][23] Additionally, changes in chromatin architecture, DNA methylation, and histone modification occur frequently and extensively throughout the course of differentiation. [5][6][7][8]13,17,18,21,22,24 Nucleosomes are the basic unit of chromatin. The canonical nucleosome is composed of 147 bp of DNA wrapped around a histone octamer core consisting of 2 copies each of histone H2A, H2B, H3, and H4.…”

Primordial Germ Cells in Mice

“…The TET proteins are therefore new candidate DNA demethylases in PGCs, where Tet1 and, to a lesser extent, Tet2, but not Tet3, are expressed (Hajkova et al 2010). Several studies have shown the roles of TET proteins, most typically the role of TET1 in ESCs (Ito et al 2010;Ficz et al 2011;Koh et al 2011;Pastor et al 2011;Song et al 2011;Williams et al 2011;Wu et al 2011;Xu et al 2011). Accordingly, one of the functions of TET1 would be to remove aberrant stochastic DNA methylation from promoters with high or intermediate CpG contents, thereby regulating DNA methylation fidelity in ESCs (Williams et al 2012).…”

Embryonic stem cell and induced pluripotent stem cell: an epigenetic perspective

“…passages [204] postimplantation lethality [129] DNA Parp1 Enhanced Reduced Knockout ESCs NA Normal development demethylation efficiency [147] efficiency [147] have been [205] established [205] Tet2 NA Reduced No effect [144] Lineage bias toward NA efficiency [147] neuroectoderm in teratoma [144] Seemingly contradictory results are indicated by asterisk. NA, not available; OSK, Oct4, Sox2 and Klf4; OSKM, OSK plus c-Myc; dKO, double knockout; EBs, embryoid bodies; RA, retinoic acid.…”