Nature | Letter
Bidirectional developmental potential in reprogrammed cells with acquired pluripotency
- Journal name:
- Nature
- Volume:
- 505,
- Pages:
- 676–680
- Date published:
- DOI:
- doi:10.1038/nature12969
- Received
- Accepted
- Published online
We recently discovered an unexpected phenomenon of somatic cell reprogramming into pluripotent cells by exposure to sublethal stimuli, which we call stimulus-triggered acquisition of pluripotency (STAP)1. This reprogramming does not require nuclear transfer2, 3 or genetic manipulation4. Here we report that reprogrammed STAP cells, unlike embryonic stem (ES) cells, can contribute to both embryonic and placental tissues, as seen in a blastocyst injection assay. Mouse STAP cells lose the ability to contribute to the placenta as well as trophoblast marker expression on converting into ES-like stem cells by treatment with adrenocorticotropic hormone (ACTH) and leukaemia inhibitory factor (LIF). In contrast, when cultured with Fgf4, STAP cells give rise to proliferative stem cells with enhanced trophoblastic characteristics. Notably, unlike conventional trophoblast stem cells, the Fgf4-induced stem cells from STAP cells contribute to both embryonic and placental tissues in vivo and transform into ES-like cells when cultured with LIF-containing medium. Taken together, the developmental potential of STAP cells, shown by chimaera formation and in vitro cell conversion, indicates that they represent a unique state of pluripotency.
Subject terms:
At a glance
Figures
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Figure 1: STAP cells contribute to both embryonic and placental tissues in vivo. a, b, E12.5 embryos from blastocysts injected with ES cells (a) and STAP cells (b). Both cells are genetically labelled with GFP driven by a constitutive promoter. Progeny of STAP cells also contributed to placental tissues and fetal membranes (b), whereas ES-cell-derived cells were not found in these tissues (a). Scale bar, 5.0 mm. c, Percentages of fetuses in which injected cells contributed only to the embryonic portion (red) or also to placental and yolk sac tissues (blue). ***P < 0.001 with Fisher’s exact test. d, qPCR analysis of FACS-sorted Oct4-GFP-strong STAP cells for pluripotent marker genes (left) and trophoblast marker genes (right). Values are shown as ratio to the expression level in ES cells. Error bars represent s.d. e, Contribution to placental tissues. Unlike parental STAP cells and trophoblast stem (TS) cells, STAP stem cells (STAP-SCs) did not retain the ability for placental contributions. Three independent lines were tested and all showed substantial contributions to the embryonic portions. f, qPCR analysis of trophoblast marker gene expression in STAP stem cells. Error bars represent s.d.
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Figure 2: Fgf4 treatment induces some trophoblast-lineage character in STAP cells. a, Schematic of Fgf4 treatment to induce Fgf4-induced stem cells from STAP cells. b, Fgf4 treatment promoted the generation of flat cell clusters that expressed Oct4-GFP at moderate levels (right). Top and middle: days 1 and 7 of culture with Fgf4, respectively. Bottom: culture after the first passage. Scale bar, 50 μm. c, d, Immunostaining of Fgf4-induced cells with the trophoblast stem cell markers integrin α7 (c) and eomesodermin (d). Scale bar, 50 μm. e, qPCR analysis of marker expression. f, g, Placental contribution of Fgf4-induced stem cells (FI-SCs) (genetically labelled with constitutive GFP expression). Scale bars: 5.0 mm (f (left panel) and g); 50 µm (f, right panel). In addition to placental contribution, Fgf4-induced stem cells contributed to the embryonic portion at a moderate level (g). h, Quantification of placental contribution by FACS analysis. Unlike Fgf4-induced cells, ES cells did not contribute to placental tissues at a detectable level. i, Cluster tree diagram from hierarchical clustering of global expression profiles. Red, approximately unbiased P values. j, qPCR analysis of Fgf4-induced cells (cultured under feeder-free conditions) with or without JAK inhibitor (JAKi) treatment for pluripotent marker genes. k, qPCR analysis of FI-SCs with or without JAK inhibitor (JAKi) treatment for trophoblast marker genes. Values are shown as ratio to the expression level in ES cells (j) or trophoblast stem cells (k). ***P < 0.001; NS, not significant; t-test for each gene between groups with and without JAK inhibitor treatment. n = 3. Statistical significance was all the same with three pluripotency markers. None of the trophoblast marker genes showed statistical significance. Error bars represent s.d.
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Figure 3: Fgf4 treatment induces some trophoblast-lineage character in STAP cells. a, Culture of Oct4-GFP Fgf4-induced cells in LIF + 20% FBS medium. b, qPCR analysis of ES-like cells derived from Fgf4-induced cells for pluripotent marker genes (left) and trophoblast marker genes (right). Values are shown as ratio to the expression level in ES cells (left) or trophoblast stem (TS) cells (right). c, d, Culture of Oct4-GFP Fgf4-induced cells sorted by FACS for strong integrin α7 (Itga7) expression in LIF + 20% FBS medium. d, Formation frequency (shown by percentage) of Oct4-GFP+ colonies from cells plated on gelatin-coated dishes at a clonal density. **P < 0.01; t-test; n = 3. e, f, Culture of Oct4-GFP Fgf4-induced cells (dissociated) in LIF + 20% FBS medium with MEK inhibitor. **P < 0.01; NS, not significant; Tukey’s test; n = 3. e, No substantial formation of Oct4-GFP+ colonies was seen from Fgf4-induced cells in the presence of MEK inhibitor (left), whereas colonies frequently formed when cells were co-plated with Oct4-GFP ES cells (right; plated cells were 1/20 of Fgf4-induced cells). f, Quantification of colony formation per plated cells (1 × 103 Fgf4-induced cells and/or 1 × 103 ES cells). Unlike Fgf4-induced cells, ES cells formed colonies (regardless of co-plating with FI-SCs) in the presence of MEK inhibitor. Bars and error bars represent mean values and s.d., respectively (b, d, f). Scale bars: 100 μm (a, c, e).
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Figure 4: Differentiation potential and epigenetic state of STAP and STAP-derived stem cells. a, Schematic diagram of stem-cell conversion cultures from STAP cells under different conditions. b, ChIP-sequencing results of histone H3K4 (green) and H3K27 (red) trimethylation at the loci of pluripotent marker genes (left), bivalent pattern genes (middle) and trophoblast marker genes (right). Scale bars indicate 10 kb for pluripotency marker genes and trophoblast marker genes, and 20 kb for bivalent pattern genes.
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Extended Data Fig. 1: Placental contribution of STAP cells. a, Chimaeric mouse with STAP cells derived from CD45+ cells of B6GFP × 129/Sv mice (B6GFP, C57BL/6 line with cag-gfp transgene). Arrows indicate a placenta and a yolk sac. b, Cross-sections of yolk sac (top) and placenta (bottom). GFP-positive cells (arrows) were seen only in yolk sac and placenta of the STAP cell chimaera. Scale bars, 50 μm. c, Co-immunostaining showed that these GFP-positive cells (right) were found in the extra-embryonic endoderm-derived epithelial cells (pan-cytokeratin+ and overlying laminin+ basement membrane; left) of the yolk sac. Scale bar, 10 μm.
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Extended Data Fig. 2: Trophoblast differentiation potential of Fgf4-induced stem cells. a, b, Immunostaining (cross-section) of placentae obtained in the blastocyst injection assay with GFP (constitutive)-labelled ES cells (upper) or Fgf4-induced stem cells (bottom). Brown shows pan-cytokeratin and red shows GFP (ES cell or Fgf4-induced stem cell contribution). Regions indicated in a are shown in b. Fgf4-induced stem cells contributed to all layers of placentae, whereas no contribution was observed with ES cells. a, Scale bars, 5 mm. b, Scale bars, 50 μm. c, Pluripotent marker expression of Fgf4-induced stem cells. Scale bars, 50 μm. d, e, Effects of Fgf4 withdrawal from Fgf4-induced stem cell culture. Unlike trophoblast stem cells (d, left), which generated multi-nucleated large cells (arrow) in the absence of Fgf4, Fgf4-induced stem cells (d, right) simply stopped proliferation and gradually died on Fgf4 withdrawal. Scale bars, 50 μm. This finding suggests that placental differentiation of Fgf4-induced stem cells in vivo may involve more than just Fgf4 signal suppression. e, The number of 4N and 8N cells increased within 6 days of Fgf4 withdrawal in trophoblast stem cells but not in Fgf4-induced stem cells.
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Extended Data Fig. 3: Transcriptome analyses of STAP cells shown by heat maps. a, Heat maps of expression profiles of top-ranked up- and downregulated genes in STAP cells (Oct4-GFP+ clusters converted from CD45+ cells) compared to ES cells. Their respective expression levels in STAP stem cells, trophoblast stem cells and Fgf4-induced stem cells are shown. Absolute expression values are scaled by log2. The genes expressed differentially between ES cells and STAP cells tended to show more similar expression profiles to ES cells in STAP stem cells and Fgf4-induced stem cells than in trophoblast stem cells. Expression of some early endodermal lineage genes such as Gata4 and Sox17 was moderately elevated in STAP cells as compared to ES cells, whereas its biological significance remains elusive (these genes are shown to be strongly expressed in Oct4-GFP-dim cells1). b, Heat maps of expression profiles of top-ranked up- and downregulated genes in ES cells compared to CD45+ cells and their respective expression levels in STAP cells. The genes expressed differentially between CD45+ and ES cells tended to show similar expression profiles in ES cells and STAP cells. c, Heat maps of expression profiles of representative genes implicated in haematopoietic lineage development in CD45+, ES and STAP cells. No strong correlation was seen between CD45+ cells and STAP cells in their expression profiles (a similar tendency of no correlation was seen for the data in b).
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Extended Data Fig. 4: Transcriptome analyses for genes implicated in cell-cycle control and induced pluripotent stem-cell conversion. a, Comparison of expression values of genes involved in cell-cycle control in ES and STAP cells; the G to M cell cycle phases (upper), the cell cycle checkpoint and cell cycle arrest (middle), and the cell cycle regulation (bottom) are shown. Expression level was measured by log2 of mean normalized counts. b, Heat map for upregulated genes in cells undergoing reprogramming by ‘Yamanaka factors’14. c, Heat maps for upregulated genes in pre-iPS cells15 (top) and in partially reprogrammed cells by Yamanaka factors (bottom)14. Expression level was measured by log2 of mean normalized counts. Differentially expressed genes were identified by the DESeq package21 and only genes with a false discovery rate of 1% were selected for comparison, unless mentioned otherwise.
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Extended Data Fig. 5: Responses of Fgf4-induced stem cells to signal modifications. a–f, JAK inhibitor treatment assay for Fgf4-induced stem cells. Fgf4-induced stem cells were cultured under feeder-free conditions and treated with 0.6 μM JAK inhibitor for 48 h. JAK inhibitor treatment assay eliminated ES cells (Oct4-GFP+) from the culture (a, b). The level of Oct4-GFP expression in Fgf4-induced stem cells, which was moderate, was maintained even after JAK inhibitor treatment (c, d; three independent experiments). Scale bar, 100 μm. e, f, For an additional control, Fgf4-induced stem cells were plated in trophoblast stem-cell medium containing Fgf4 together with Oct4-GFP ES cells that constitutively expressed BFP (the number of plated cells was one-tenth of that of plated Fgf4-induced stem cells). Whereas BFP-expressing colonies (ES-cell-derived) still expressed Oct4-GFP in trophoblast stem-cell culture medium after 2 days (e), no Oct4-GFP+ colonies from BFP-expressing ES cells were observed in the JAK-inhibitor-treated culture (f). g, FACS analysis of integrin α7 expression in Fgf4-induced stem cells. Over 40% of Fgf4-induced stem cells strongly expressed both the pluripotency marker Oct4-GFP and the trophoblast marker integrin α7. The bottom panel shows an isotype control for integrin α7 antibody. In ES cells, integrin-α7-expressing cells were less than 0.1% (data not shown; three independent ES cell lines were examined).
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Extended Data Fig. 6: Characterization of ES-like cells converted from Fgf4-induced stem cells and comparison of STAP cells with early embryos. a, Immunohistochemistry of ES-like cells for trophoblast and pluripotency markers. ES-like cells converted from Fgf4-induced stem cells no longer expressed the trophoblast marker (integrin alpha 7), but they did express the pluripotency markers (Oct4, Nanog and SSEA-1). Scale bar, 100 μm. b, Pluripotency of ES-like cells converted from Fgf4-induced stem cells as shown by teratoma formation. Those cells successfully formed teratomas containing tissues from all three germ layers: neuroepithelium (left, arrow indicates), muscle tissue (middle, arrow indicates) and bronchial-like epithelium (right). Scale bar, 100 μm. c, MEK inhibitor treatment assay for Oct4-gfp Fgf4-induced stem cells in trophoblast stem-cell medium containing Fgf4. No substantial formation of Oct4-GFP+ colonies was observed from dissociated Fgf4-induced stem cells in MEK-inhibitor-containing medium. Scale bar, 100 μm. d, Cluster tree diagram from hierarchical clustering of global expression profiles. Red, AU P values. As this analysis included morula and blastocyst embryos from which only small amounts of RNA could be obtained, we used pre-amplification with the SMARTer Ultra Low RNA kit for Illumina Sequencing (Clontech Laboratories). e, f, Volcano plot of the expression profile of STAP cells compared to the morula (e) and blastocyst (f). Genes showing greater than 10-fold change and P value 1.0 × 10−6 are highlighted in red and are considered up- (or down-) regulated in the STAP cells.
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Comment posted on behalf of the authors: "The multiple BioSample accession numbers associated with the RNA-seq and ChIP-seq data that were reported in the published Letter have now been replaced by a single SRA accession number: SRP038104."