Effect of Tet1-knockdown on gene expression in mouse ES cells cultured in ES and TS cell culture conditions

TET-family enzymes convert 5-methylcytosine (5mC) to 5-hydroxymethylcytosine (5hmC) in DNA. Tet1 and Tet2 are Oct4-regulated enzymes that together sustain 5hmC in mouse embryonic stem (ES) 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 that favor derivation of trophoblast stem (TS) cells, 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 Tet1 functions to regulate the lineage differentiation potential of ES cells. Here, we performed whole-genome transcriptome profiling of ES cells stably depleted of Tet1 by shRNA knockdown (Tet1-kd) cultured in either standard ES cell or in TS cell culture conditions. Gene expression changes in Tet1-kd ES cells were fairly modest compared to control (GFP-kd) cells, although gene ontology (GO) analysis of differentially expressed genes yielded many terms related to embryonic development and cell cycle regulation. In TS cell culture conditions, a core set of genes defining trophectodermal cell differentiation, including Cdx2, Eomes and Tead4, was enriched in Tet1-kd compared to GFP-kd cells.