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Continuous expression of reprogramming factors OSKM induces and maintains mouse pluripotency without specific growth factors and signaling inhibitors

ABSTRACT: Derivation and maintenance of pluripotent stem cells (PSCs) including embryonic stem cells(ESCs) and (iPSCs) usually requires optimization of complex culture media, which hinders the generation of PSCs from various species. Expression of Oct4, Sox2, Klf4 and c-Myc (OSKM) can reprogram somatic cells into iPSCs, even for species possessing no optimal culture condition. Here we explored whether expression of OSKM could induce and maintain pluripotency without specific growth factors and signaling inhibitors. Tet-On-OSKM/Oct4-GFP Mouse ESCs (mESCs) were derived from the embryos obtained after mating of Tet-On-OSKM mouse and Oct4-GFP mouse under the 2iL ( N2B27 plus MEK inhibitor PD0325901, GSK3β inhibitor ChIR99021, and leukemia inhibitory factor) condition. Tet-On-OSKM mouse was Gt(ROSA)26Sor tm1(rtTA*M2)Jae Col1a1 tm3(tetO-Pou5f1,-Sox2,-Klf4,-Myc)Jae/J(The Jackson Laboratory,011004), and Oct4-GFP mouse was B6;CBA-Tg(Pou5f1-EGFP)2Mnn/J (The Jackson Laboratory,004654).The culture medium of Tet-On-OSKM/Oct4-GFP mouse ESCs was switched from 2iL to N2B27 plus Doxycycline medium (OSKM medium), under which OSKM trangene was activated. These above cells switched from 2iL to OSKM medium were called OSKM-ESCs. Meanwhile 2iL-ESCs (continuely cultured in 2iL) served as the positive control group. 2iL-ESCs and OSKM-ESCs collected at selective days (d18, 25 and 38) after medium switch were collected for RNA-Seq. Moreover, Tet-On-OSKM mouse embryonic fibroblast (MEF) cells were reprogrammed under OSKM medium (N2B27 plus Doxycycline) and 2iL medium, respectively. The resulting OSKM-iPSCs were reprogrammed and cultured under OSKM medium.The 2iL-iPSCs were reprogrammed under 2iL plus Doxycycline medium and cultured under 2iL medium (without Doxycycline)once clones were picked up.RNA-Seq of these above samples was conducted to analyze gene expression. We found that via continuous expression of OSKM,OSKM-ESCs and OSKM-iPSCs propagated stably, expressed pluripotency marker genes, and formed three germ layers in teratomas. Importantly, OSKM-iPSCs could produce gene-modified animals through germline transmission.Transcriptional landscapes of OSKM-iPSCs resembled 2iL-ESCs, and were more similar to those of ESCs cultured in serum/LIF.

ORGANISM(S): Mus musculus

PROVIDER: GSE173471 | GEO | 2021/08/24

REPOSITORIES: GEO

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Project description:Induced pluripotent stem cells (iPSCs) are commonly generated by transduction of Oct4, Sox2, Klf4 and Myc (OSKM) into somatic cells. Though iPSCs are pluripotent, they frequently exhibit high variation in their quality as measured by chimera contribution and tetraploid (4n) complementation. Thus, improving the quality of iPSCs is an indispensable prerequisite for future iPSC-based therapy. Here we show that one major determinant for iPSCs quality is the combination of reprograming factor selected. Ectopic expression of Sall4, Nanog, Esrrb and Lin28 (SNEL) in MEFs efficiently generated high quality iPSCs as compared to other combinations of factors. SNEL-iPSCs produced approximately 5 times more efficiently “all-iPSC” mice compared to OSKM-iPSCs. While differentially methylated regions, transcript number of master regulators, establishment of ESC-specific super enhancers, and global aneuploidy were comparable between the lines, aberrant expression of 1,765 genes, trisomy of chromosome 8 and abnormal H2A.X deposition were frequently observed in poor quality OSK-iPSCs and OSKM-iPSCs. Whole-genome single-base resolution MethylC sequencing collected from a variety of Mouse pluripotent cells To reveal the DNA methylation signature associated with developmental competence, we selected the following groups of iPSC lines for whole-genome bisulfite sequencing: i) "Poor quality" iPSCs: This group included the three OSKM-iPSC lines Nanog-GFP OSKM#2, Oct4-GFP OSKM#2 and KH2 OSKM(Stadtfeld et al., 2010), that either did not produce fully developed pups or produced very low number of pups; ii) "Good quality" iPSCs: This group included BC_2 OSKM (Carey et al., 2011) and Nanog-GFP SNEL#3, both of which gave rise to live, normal pups that survived only few hours; iii) "High quality" iPSCs consisting of Nanog-GFP SNEL#2 and Oct4-GFP SNEL#1, both of which generated live pups that survived postnatally (representative pups from each iPSC group are shown in Figure S3A). iv) As controls we used Nanog-GFP, Oct4-GFP and KH2 (Beard et al., 2006) ESCs. Note that all cells were cultured in 2i medium but not in mES medium.

Project description:The generation of induced pluripotent stem cells (iPSCs) by the forced expression of defined transcription factors in somatic cells holds great promise for the future of regenerative medicine. However, due to a poor understanding of the initial reprogramming mechanism, it is difficult to control the efficiency and quality of the iPSCs. Here we show that Zscan4, expressed transiently in 2-cell embryos and embryonic stem cells (ESCs), efficiently produces iPSCs from mouse embryo fibroblasts when coexpressed with Klf4, Oct4, and Sox2. Unlike other factors, Zscan4 is required only for the first few days of iPSC formation. Microarray analysis revealed transient and early induction of preimplantation-specific genes in a Zscan4-dependent manner. Our work indicates that Zscan4 is a previously unidentified potent natural factor that facilitates the reprogramming process through the recapitulation of the early embryonic program. Secondary MEFs were isolated from E13.5 embryos, which were harvested by tetraploid complementation. Secondary MEFs were plated on gelatin-coated 6-well plates at a density of 1x105 cells/well in the complete ES medium. After 24 h incubation, secondary MEFs were fed with complete ES medium with or without Dox (1.5 ?g/ml) and with or without 200 nM Tmx. Culture medium was changed every day. Withdrawal of drugs (Dox or Tmx) was always followed by 1x washing by PBS before changing culture medium. We cotransfected MEFs with PB-Tet-MKOS and either a PB-Tet-Zscan4 or PB-Tet-DsRed (control). These cells were subsequently cultured in the standard iPSC generation condition (Dox+). Unexpectedly, we found that MEFs transfected with a PB-Tet-Zscan4 show consistently higher efficiency of iPSC generation than MEFs transfected with a PB-Tet-DsRed (control). All selected iPSCs expressed pluripotent marker genes according to RT-PCR analysis and were positive for ALP, Nanog, and SSEA-1. These iPSCs also formed embryoid bodies in hanging drops without LIF and could be differentiated in vitro to cells of all three germ layers. We are currently studying whether the presence of Zscan4 has the beneficial effects on iPSCs in terms of genome stability.

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Continuous expression of reprogramming factors OSKM induces and maintains mouse pluripotency without specific growth factors and signaling inhibitors

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