Project description:Pluripotent stem cell lines derived from embryos of different stages have distinct pluripotent ground states, but similar levels of the transcription factor Oct4. Epiblast-derived pluripotent stem cells (EpiSCs), in contrast to embryonic stem (ES) cells, cannot form chimeras. We show that EpiSCs express lower levels of the transcription factors Sox2 and Klf4 than ES cells and have limited reprogramming potential, as shown by cell fusion. Sox2 overexpression dramatically increases the reprogramming potential, chimera formation, and germline contribution of EpiSCs. Therefore, although Oct4 is essential for reprogramming, the level of Sox2 defines both the reprogramming capability and the pluripotent ground states.
Project description:Pluripotent stem cell lines derived from embryos of different stages have distinct pluripotent ground states, but similar levels of the transcription factor Oct4. Epiblast-derived pluripotent stem cells (EpiSCs), in contrast to embryonic stem (ES) cells, cannot form chimeras. We show that EpiSCs express lower levels of the transcription factors Sox2 and Klf4 than ES cells and have limited reprogramming potential, as shown by cell fusion. Sox2 overexpression dramatically increases the reprogramming potential, chimera formation, and germline contribution of EpiSCs. Therefore, although Oct4 is essential for reprogramming, the level of Sox2 defines both the reprogramming capability and the pluripotent ground states. RNA samples to be analyzed on microarrays were prepared using Qiagen RNeasy columns with on-column DNA digestion. 300 ng of total RNA per sample was used as input into a linear amplification protocol (Ambion), which involved synthesis of T7-linked double-stranded cDNA and 12 hrs of in-vitro transcription incorporating biotin-labelled nucleotides. Purified and labelled cRNA was then hybridized for 18 hrs onto MouseRef-8 v2 expression BeadChips (Illumina) according to the manufacturer's instructions. After washing, as recommended, chips were stained with streptavidin-Cy3 (GE Healthcare) and scanned using the iScan reader (Illumina) and accompanying software. Samples were hybridized as biological replicates. 12 sample types were analyzed, each of them in duplicate. ESCm: Mouse ESC male; ESCf: Mouse ESC OG2 female; F9 EC: F9 EC (mouse embryonic carcinoma cell); F9-Sox2: F9 EC (mouse embryonic carcinoma cell) overexpressing wild type Sox2; EpiSCf: Mouse EpiSC OG2 female; Epi-Sox2f: Mouse EpiSC Sox2 (OG2 female) overexpressing wild type Sox2; P19 EC: P19 EC (mouse embryonic carcinoma cell); P19-Sox2: P19 EC (mouse embryonic carcinoma cell) overexpressing wild type Sox2; EpiSCm: Mouse EpiSC (GOF18 male) (duplicates); EpiSox2mL2: Mouse EpiSC Sox2 (GOF18 male) overexpressing wild type Sox2 cultured in condition EpiSC medium (CM); EpiSox2mE1: Mouse EpiSC Sox2 (GOF18 male) overexpressing wild type Sox2 cultured in ESC medium (ESC like1); EpiSox2mE2: Mouse EpiSC Sox2 (GOF18 male) overexpressing wild type Sox2 cultured in ESC medium (ESC like2).
Project description:PGCs undergo two distinct stages of demethylation before reaching a hypomethylated ground state at E13.5. Stage 1 occurs between E7.25- E9.5 in which PGCs experience a global loss of cytosine methylation. However, discreet loci escape this global loss of methylation and between E10.5-E13.5, stage 2 of demethylation takes place. In this stage these loci are targeted by Tet1 and Tet2 leading to the loss of the remaining methylation and resulting in the epigenetic ground state. Our data shows that Dnmt1 is responsible for maintaining the methylation of loci that escape stage 1 demethylation, and that it functions in a UHRF1 independent manner. Our data further demonstrates that when these loci lose methylation prior to stage 2 it results in early activation of the meiotic program, which leads to precocious differentiation of the germ line resulting in a decreased pool of PGCs in the embryo and subsequent infertility in adult mice.
Project description:Somatic cells can be reprogrammed to Induced Pluripotent Stem Cells (iPSCs) by expressing four transcription factors, Oct4, Sox2, Klf4 and c-Myc. Co-expressing Rarg (retinoic acid receptor gamma) and Lrh-1 (liver receptor homolog 1, Nr5a2) with the four factors greatly accelerated reprogramming so that reprogramming of mouse embryonic fibroblast cells (MEFs) to ground state iPSCs requires only four days’ induction of these six factors. The six-factor combination readily reprogrammed primary human neonatal and adult fibroblast cells to exogenous-factor-independent iPSCs, which resembled ground state mouse ES cells in growth properties, gene expression and signalling dependency. Our findings demonstrate that signalling through RARs has critical roles in molecular reprogramming and the synergistic interaction between Rarg and Lrh1 directs reprogramming towards ground state pluripotency.
Project description:Unique transcriptomes define naïve, primed and paused embryonic pluripotent states. Here we perform calibrated transient transcription sequencing (TT-seq) to de novo define and quantify coding and non-coding transcription units (TUs) in different pluripotent states. We observe a global reduction of RNA synthesis, total RNA amount and turnover rates in ground state (2i) and paused pluripotency (mTORi). We demonstrate that elongation speed can be reliably estimated from TT-seq nascent RNA and RNA Polymerase II occupancy levels, and observe a transcriptome-wide attenuation of elongation speeds in these two inhibitor-induced states. Comparing closely related transcriptional states with different elongation speeds, we also discover a relationship between elongation speed and termination read-through distance. Our analysis suggests that steady-state transcriptomes in mouse ESC cells are controlled predominantly on the level of RNA synthesis and signaling pathways governing different pluripotent states directly control key parameters of transcription.