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Despite direct reprogramming of human cardiac fibroblasts into induced cardiomyocytes (iCM) holds great potential for heart regeneration, the mechanisms are poorly understood. Whether other human somatic cells could be reprogrammed into cardiomyocytes is also unknown. Here, we report human urine cells (hUCs) could be converted into CM-like cells from different donors and the related chromatin accessibility dynamics (CAD) by assay for transposase accessible chromatin(ATAC)-seq. hUCs transduced by MEF2C, TBX5, MESP1 and MYOCD but without GATA4 expressed multiple cardiac specific genes, exhibited Ca

Each vertebrate species appears to have a unique timing mechanism for forming somites along the vertebral column, and the process in human remains poorly understood at the molecular level due to technical and ethical limitations. Here, we report the reconstitution of human segmentation clock by direct reprogramming. We first reprogrammed human urine epithelial cells to a presomitic mesoderm (PSM) state capable of long-term self-renewal and formation of somitoids with an anterior-to-posterior axis. By inserting the RNA reporter Pepper into HES7 and MESP2 loci of these iPSM cells, we show that both transcripts oscillate in the resulting somitoids at ~5 h/cycle. GFP-tagged endogenous HES7 protein moves along the anterior-to-posterior axis during somitoid formation. The geo-sequencing analysis further confirmed anterior-to-posterior polarity and revealed the localized expression of WNT, BMP, FGF, and RA signaling molecules and HOXA-D family members. Our study demonstrates the direct reconstitution of human segmentation clock from somatic cells, which may allow future dissection of the mechanism and components of such a clock and aid regenerative medicine.

BMP4 regulates a plethora of developmental processes, including the dorsal-ventral axis and neural patterning. Here, we report that BMP4 reconfigures the nuclear architecture during the primed-to-naive transition (PNT). We first established a BMP4-driven PNT and show that BMP4 orchestrates the chromatin accessibility dynamics during PNT. Among the loci opened early by BMP4, we identified Zbtb7a and Zbtb7b (Zbtb7a/b) as targets that drive PNT. ZBTB7A/B in turn facilitate the opening of naive pluripotent chromatin loci and the activation of nearby genes. Mechanistically, ZBTB7A not only binds to chromatin loci near to the genes that are activated, but also strategically occupies those that are silenced, consistent with a role of BMP4 in both activating and suppressing gene expression during PNT at the chromatin level. Our results reveal a previously unknown function of BMP4 in regulating nuclear architecture and link its targets ZBTB7A/B to chromatin remodelling and pluripotent fate control.

Forkhead box (Fox) transcription factors play important roles in mammalian development and disease. However, their function in mouse somatic cell reprogramming remains unclear. Here, we report that FoxD subfamily and FoxG1 accelerate induced pluripotent stem cells (iPSCs) generation from mouse fibroblasts as early as day4 while FoxA and FoxO subfamily impede this process obviously. More importantly, FoxD3, FoxD4 and FoxG1 can replace Oct4 respectively and generate iPSCs with germline transmission together with Sox2 and Klf4. On the contrary, FoxO6 almost totally blocks reprogramming through inhibiting cell proliferation, suppressing the expression of pluripotent genes and hindering the process of mesenchymal to epithelial transition (MET). Thus, our study uncovers unexpected roles of Fox transcription factors in reprogramming and offers new insights into cell fate transition. Supplementary Information The online version contains supplementary material available at 10.1186/s13619-021-00078-4.

The transition from pluripotent to somatic states marks a critical event in mammalian development, but remains largely unresolved. Here we report the identification of SS18 as a regulator for pluripotent to somatic transition or PST by CRISPR-based whole genome screens. Mechanistically, SS18 forms microscopic condensates in nuclei through a C-terminal intrinsically disordered region (IDR) rich in tyrosine, which, once mutated, no longer form condensates nor rescue SS18−/− defect in PST. Yet, the IDR alone is not sufficient to rescue the defect even though it can form condensates indistinguishable from the wild type protein. We further show that its N-terminal 70aa is required for PST by interacting with the Brg/Brahma-associated factor (BAF) complex, and remains functional even swapped onto unrelated IDRs or even an artificial 24 tyrosine polypeptide. Finally, we show that SS18 mediates BAF assembly through phase separation to regulate PST. These studies suggest that SS18 plays a role in the pluripotent to somatic interface and undergoes liquid-liquid phase separation through a unique tyrosine-based mechanism., Emerging evidence suggests that exit from pluripotency is a regulated, rather than passive process. Here the authors identify a requirement for SS18-mediated Brg/Brahma-associated factors (BAF) chromatin remodeling complex assembly during exit from pluripotency, and that SS18 promotes BAF assembly through liquidliquid phase separation.

Single cell analysis provides clarity unattainable with bulk approaches. Here we apply single cell RNA-seq to a newly established BMP4 induced mouse primed to naive transition (Bi-PNT) system and show that the reset is not a direct reversal of cell fate but through developmental intermediates. We first show that mEpiSCs bifurcate into c-Kit+ naïve and c-Kit- placenta-like cells, among which, the naive branch undergoes further transition through a primordial germ cell-like cells (PGCLCs) intermediate capable of spermatogenesis in vivo. Indeed, deficiency of Prdm1/Blimp1, the key regulator for PGC specification, blocks the induction of PGCLCs and naïve cells. Instead, Gata2 knockout arrests placenta-like fate, but facilitates the generation of PGCLCs. Our results not only reveal a newly cell fate dynamics between primed and naive states at single-cell resolution, but also provide a model system to explore mechanisms involved in regaining germline competence from primed pluripotency.

Summary Polycomb repressive complex 1 (PRC1) plays essential roles in cell-fate determination. Recent studies have found that the composition of mammalian PRC1 is particularly varied and complex; however, little is known about the functional consequences of these variant PRC1 complexes on cell-fate determination. Here, we show that Kdm2b promotes Oct4-induced somatic reprogramming through recruitment of a variant PRC1 complex (PRC1.1) to CpG islands (CGIs). Furthermore, we find that bone morphogenetic protein (BMP) represses Oct4/Kdm2b-induced somatic reprogramming selectively. Mechanistically, BMP-SMAD pathway attenuates PRC1.1 occupation and H2AK119 ubiquitination at genes linked to development, resulting in the expression of mesendodermal factors such as Sox17 and a consequent suppression of somatic reprogramming. These observations reveal that PRC1.1 participates in the establishment of pluripotency and identify BMP4 signaling as a modulator of PRC1.1 function.

BMP4 regulates a plethora of developmental processes, including the dorsal-ventral axis and neural patterning. Here, we report that BMP4 reconfigures the nuclear architecture during the primed-to-naive transition (PNT). We first established a BMP4-driven PNT and show that BMP4 orchestrates the chromatin accessibility dynamics during PNT. Among the loci opened early by BMP4, we identified Zbtb7a and Zbtb7b (Zbtb7a/b) as targets that drive PNT. ZBTB7A/B in turn facilitate the opening of naive pluripotent chromatin loci and the activation of nearby genes. Mechanistically, ZBTB7A not only binds to chromatin loci near to the genes that are activated, but also strategically occupies those that are silenced, consistent with a role of BMP4 in both activating and suppressing gene expression during PNT at the chromatin level. Our results reveal a previously unknown function of BMP4 in regulating nuclear architecture and link its targets ZBTB7A/B to chromatin remodelling and pluripotent fate control.

Safety issues associated with transcription factors or viruses may be avoided with the use of chemically induced pluripotent stem cells (CiPSCs), thus promoting their clinical application. Previously, we had successfully developed and standardized an induction method using small-molecule compound, with simple operation, uniform induction conditions, and clear constituents. In order to verify that the CiPSCs were indeed reprogrammed from mouse embryonic fibroblasts (MEFs), and further explore the underlying mechanisms, FSP-tdTomato mice were used to construct a fluorescent protein-tracking system of MEFs, for revealing the process of CiPSC reprogramming. CiPSCs were identified by morphological analysis, mRNA, and protein expression of pluripotency genes, as well as teratoma formation experiments. Results showed that after 40-day treatment of tdTomato-MEFs with small-molecule compounds, the cells were presented with prominent nucleoli, high core-to-cytoplasmic ratio, round shape, group and mass arrangement, and high expression of pluripotency gene. These cells could differentiate into three germ layer tissues in vivo. As indicated by the above results, tdTomato-MEFs could be reprogrammed into CiPSCs, a lineage that possesses pluripotency similar to mouse embryonic stem cells (mESCs), with the use of small-molecule compounds. The establishment of CiPSC lineage, tracked by fluorescent protein, would benefit further studies exploring its underlying mechanisms. With continuous expression of fluorescent proteins during cellular differentiation, this cell lineage could be used for tracking CiPSC transplantation and differentiation into functional cells.

We report here an approach to redirecting somatic cell fate under chemically defined conditions without transcription factors. We start by converting mouse embryonic fibroblasts to epithelial-like cells with chemicals and growth factors. Subsequent cell fate mapping reveals a robust induction of SOX17 in the resulting epithelial-like cells that can be further reprogrammed to endodermal progenitor cells. Interestingly, these cells can self-renew in vitro and further differentiate into albumin-producing hepatocytes that can rescue mice from acute liver injury. Our results demonstrate a rational approach to convert mouse embryonic fibroblasts to hepatocytes and suggest that this mechanism-driven approach may be generalized for other cells.

Clinical research in coronary artery disease (CAD) primarily focused on genetic variants located in protein-coding regions. Recently, mutations fall within non-coding regions have been suggested to be essential to the pathogenesis of human complex disease. Super enhancer is a densely spaced cluster of transcriptional enhancers located in non-coding regions, which is critical for regulating cell-type specific gene expression. However, the underlying mechanism of the super enhancer single-nucleotide polymorphisms (SNPs) affecting the risk of CAD remains unclear. By integrating genome-wide association study (GWAS) meta-analysis of CAD and cell/tissue-specific histone modification data set, we identified 366 potential CAD-associated super enhancer SNPs in 67 loci, including 94 SNPs that are involved in regulating chromatin interactive and/or affecting the transcription factors binding affinity. Interestingly, we found 7 novel functional loci (CBFA2T3, ZMIZ1, DIP2B, SCNN1D/ACAP3, TMEM105, CAMK2G, and MAPK1) that CAD-associated super enhancer SNPs were clustered into the same or neighboring super enhancers. Pathway analysis showed a significant enrichment in several well-known signaling and regulatory processes, e.g., cAMP signaling pathway and ErbB signaling pathway, which play a key role in CAD metabolism. Our results highlight the potential functional importance of CAD-associated super enhancer SNPs and provide the targets for further insights on the pathogenesis of CAD.

Summary: Reprogramming somatic cells to pluripotency by Oct4, Sox2, Klf4, and Myc represent a paradigm for cell fate determination. Here, we report a combination of Jdp2, Jhdm1b, Mkk6, Glis1, Nanog, Essrb, and Sall4 (7F) that reprogram mouse embryonic fibroblasts or MEFs to chimera competent induced pluripotent stem cells (iPSCs) efficiently. RNA sequencing (RNA-seq) and ATAC-seq reveal distinct mechanisms for 7F induction of pluripotency. Dropout experiments further reveal a highly cooperative process among 7F to dynamically close and open chromatin loci that encode a network of transcription factors to mediate reprogramming. These results establish an alternative paradigm for reprogramming that may be useful for analyzing cell fate control. : Wang et al. report a 7F reprogramming system for iPSC generation and the underlying mechanism for inducing pluripotency through a TF network, opening an alternative path for reprogramming cell fate.

Summary Despite its exciting potential, chemical induction of pluripotency (CIP) efficiency remains low and the mechanisms are poorly understood. We report the development of an efficient two-step serum- and replating-free CIP protocol and the associated chromatin accessibility dynamics (CAD) by assay for transposase-accessible chromatin (ATAC)-seq. CIP reorganizes the somatic genome to an intermediate state that is resolved under 2iL condition by re-closing previously opened loci prior to pluripotency acquisition with gradual opening of loci enriched with motifs for the OCT/SOX/KLF families. Bromodeoxyuridine, a critical ingredient of CIP, is responsible for both closing and opening critical loci, at least in part by preventing the opening of loci enriched with motifs for the AP1 family and facilitating the opening of loci enriched with SOX/KLF/GATA motifs. These changes differ markedly from CAD observed during Yamanaka-factor-driven reprogramming. Our study provides insights into small-molecule-based reprogramming mechanisms and reorganization of nuclear architecture associated with cell-fate decisions.

Oncogenic transcription factors are known to mediate the conversion of somatic cells to tumour or induced pluripotent stem cells (iPSCs). Here we report c-Jun as a barrier for iPSC formation. c-Jun is expressed by and required for the proliferation of mouse embryonic fibroblasts (MEFs), but not mouse embryonic stem cells (mESCs). Consistently, c-Jun is induced during mESC differentiation, drives mESCs towards the endoderm lineage and completely blocks the generation of iPSCs from MEFs. Mechanistically, c-Jun activates mesenchymal-related genes, broadly suppresses the pluripotent ones, and derails the obligatory mesenchymal to epithelial transition during reprogramming. Furthermore, inhibition of c-Jun by shRNA, dominant-negative c-Jun or Jdp2 enhances reprogramming and replaces Oct4 among the Yamanaka factors. Finally, Jdp2 anchors 5 non-Yamanaka factors (Id1, Jhdm1b, Lrh1, Sall4 and Glis1) to reprogram MEFs into iPSCs. Our studies reveal c-Jun as a guardian of somatic cell fate and its suppression opens the gate to pluripotency.

p-Type polycrystalline diamond films were prepared by hot-filament CVD method using a liquid cyclic organic borinate ester as the doping source. The obtained films were identified as diamond films by means of SEM and Raman spectroscopy. The resistivity of the doped films can be adjusted by changing the temperature of the boron source.

Nat. Cell Biol. 17, 856–867 (2015); published online 22 June 2015; corrected after print 10 August 2015 In the version of this Article originally published, panels from Fig. 8e were mistakenly reproduced as Fig. 6g. The correct panels for Fig. 6g (KS/Jdp2-iPSC) are shown here and have been amended in all online versions of the Article.