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Ageing is a degenerative process that leads to tissue dysfunction and death. A proposed cause of ageing is the accumulation of epigenetic noise that disrupts gene expression patterns, leading to decreases in tissue function and regenerative capacity 1 – 3 . Changes to DNA methylation patterns over time form the basis of ageing clocks 4 , but whether older individuals retain the information needed to restore these patterns—and, if so, whether this could improve tissue function—is not known. Over time, the central nervous system (CNS) loses function and regenerative capacity 5 – 7 . Using the eye as a model CNS tissue, here we show that ectopic expression of Oct4 (also known as Pou5f1 ), Sox2 and Klf4 genes (OSK) in mouse retinal ganglion cells restores youthful DNA methylation patterns and transcriptomes, promotes axon regeneration after injury, and reverses vision loss in a mouse model of glaucoma and in aged mice. The beneficial effects of OSK-induced reprogramming in axon regeneration and vision require the DNA demethylases TET1 and TET2. These data indicate that mammalian tissues retain a record of youthful epigenetic information—encoded in part by DNA methylation—that can be accessed to improve tissue function and promote regeneration in vivo. Expression of three Yamanaka transcription factors in mouse retinal ganglion cells restores youthful DNA methylation patterns, promotes axon regeneration after injury, and reverses vision loss in a mouse model of glaucoma and in aged mice, suggesting that mammalian tissues retain a record of youthful epigenetic information that can be accessed to improve tissue function.

Octamer-binding transcription factor 4 (Oct-4) is essential for maintenance and pluripotency of embryonic stem (ES) cells. Despite the structural similarities between Oct-4 and its homologs (Oct-1, Oct-2, and Oct-6), these homologs cannot serve as substitutes for Oct-4 when generating stem cell colonies. While nuclear receptor subfamily 5, group A, member 2 (Nr5a2) can temporarily serve as a substitute for Oct-4 during cellular reprogramming, it is insufficient to maintain these functions in ES cells. The EWS-Oct-4 fusion protein, which was identified in human tumors, is a viable alternative that can potentially sustain and enhance ES cell functions. This study used ZHBTc4 ES cells, which have tetracycline-regulated Oct-4 expression, to explore the capabilities of EWS-Oct-4. It employed a variety of assays, including western blotting, immunocytochemistry, RT-PCR, luciferase reporter assays, flow cytometry, and teratoma formation assays. EWS-Oct-4 preserved the self-renewal capacity of Oct-4-null ES cells, as demonstrated by their undifferentiated morphology and increased expression of pluripotency markers such as Sox2, Nanog, and SSEA-1. It also boosted cell proliferation and influenced cell cycle dynamics by downregulating p21 and upregulating Oct-4 target genes, including Rex-1 and fibroblast growth factor-4. Epithelial markers were upregulated and mesenchymal markers were downregulated, suggesting a shift toward an epithelial phenotype. Prominent teratoma formation further confirmed the functionality of EWS-Oct-4 in vivo. The integrity and specific functional domains of EWS-Oct-4 were critical for these effects. Finally, comparative transcriptomic analysis revealed that ES cells expressing EWS-Oct-4 and those expressing Oct-4 had highly similar global gene expression profiles, with distinct variations in differentially expressed genes. These findings indicate that EWS-Oct-4 can effectively replace Oct-4, which has significant implications for advancements in stem cell research and regenerative medicine.

H2020 European Research Council, Grant/Award Number: ERC-2014-AdG/669622; Fundación Científica Asociación Española Contra el Cáncer, Grant/Award Number: PROYE18061FERN; Ministerio de Ciencia e Innovación, Grant/Award Number: SAF2013-48256-R; the Asturias Regionla Government (PCTI) co-funding 2018- 2022/FEDER (IDI/2018/146), the Health Institute Carlos III (Plan Nacional de I+D+I) co-funding FEDER (PI18/01527)...

Copper serves as a co-factor for a host of metalloenzymes that contribute to malignant progression. The orally bioavailable copper chelating agent tetrathiomolybdate (TM) has been associated with a significant survival benefit in high-risk triple negative breast cancer (TNBC) patients. Despite these promising data, the mechanisms by which copper depletion impacts metastasis are poorly understood and this remains a major barrier to advancing TM to a randomized phase II trial. Here, using two independent TNBC models, we report a discrete subpopulation of highly metastatic SOX2/OCT4+ cells within primary tumors that exhibit elevated intracellular copper levels and a marked sensitivity to TM. Global proteomic and metabolomic profiling identifies TM-mediated inactivation of Complex IV as the primary metabolic defect in the SOX2/OCT4+ cell population. We also identify AMPK/mTORC1 energy sensor as an important downstream pathway and show that AMPK inhibition rescues TM-mediated loss of invasion. Furthermore, loss of the mitochondria-specific copper chaperone, COX17, restricts copper deficiency to mitochondria and phenocopies TM-mediated alterations. These findings identify a copper-metabolism-metastasis axis with potential to enrich patient populations in next-generation therapeutic trials. Copper depletion has been reported to improve survival in patients with triple negative breast cancer (TNBC) but the underlying mechanisms are not completely understood. Here, the authors show that copper chelation reduces mitochondrial oxidative phosphorylation leading to decreased TNBC metastasis.

N6-methyladenosine (m6A) RNA methylation contributes to the cancer stem cell (CSC) phenotype through regulating gene expression. YTHDF2, an m6A reader, was shown to be associated with hepatocellular carcinoma (HCC) patient prognosis. However, the effect of YTHDF2 on liver CSC and cancer metastasis and the molecular mechanism of this effect have not been documented. Here, we show that YTHDF2 expression is negatively correlated with HCC patient survival in both data from the Cancer Genome Atlas (TCGA) database and clinical data from our center. By detecting CD133+ cells and carrying out sphere culture assays, we found that knockdown of YTHDF2 led to impaired stemness in Hep3B and Huh7 cells. In contrast, overexpression of YTHDF2 increased the CSC phenotype. Mechanistically, the knockdown and overexpression of YTHDF2 in liver cancer cells resulted in decreased and increased m6A levels in the 5′-untranslated region (UTR) of OCT4 mRNA, respectively, leading to decreased and increased OCT4 protein expression, respectively. A luciferase activity assay showed that mutation of the corresponding m6A methylation sequence in the 5′-UTR of OCT4 mRNA caused significantly decreased gene expression, suggesting a role for YTHDF2-dependent m6A methylation in protein translation. Polysome profiling results also indicated the knockdown and overexpression of YTHDF2 could decrease and increase OCT4 translation, respectively. In particular, overexpression of OCT4 rescued the impaired stemness caused by YTHDF2 depletion, which confirmed the effect of YTHDF2 on CSC phenotype is dependent on OCT4. In vivo, the loss of YTHDF2 reduced tumor burden and inhibited lung metastasis following orthotopic transplantation in nude mice. Last, we demonstrated that YTHDF2 expression is positively correlated with OCT4 expression and m6A levels in the 5′-UTR of OCT4 mRNA in clinical HCC specimens. In conclusion, YTHDF2 promotes the CSC liver phenotype and cancer metastasis by modulating the m6A methylation of OCT4 mRNA.

Accumulating evidence indicates that circular RNAs (circRNAs) are abundant in the human transcriptome. However, their involvement in biological processes, including pluripotency, remains mostly undescribed. We identified a subset of circRNAs that are enriched in undifferentiated human embryonic stem cells (hESCs) and demonstrated that two, circBIRC6 and circCORO1C , are functionally associated with the pluripotent state. Mechanistically, we found that circBIRC6 is enriched in the AGO2 complex and directly interacts with microRNAs, miR-34a, and miR-145, which are known to modulate target genes that maintain pluripotency. Correspondingly, circBIRC6 attenuates the downregulation of these target genes and suppresses hESC differentiation. We further identified hESC-enriched splicing factors (SFs) and demonstrated that circBIRC6 biogenesis in hESCs is promoted by the SF ESRP1, whose expression is controlled by the core pluripotency-associated factors, OCT4 and NANOG. Collectively, our data suggest that circRNA serves as a microRNA “sponge” to regulate the molecular circuitry, which modulates human pluripotency and differentiation. Circular RNAs are abundant in the transcriptome and are implicated in the regulation of a range of biological processes. Here the authors identify circBIRC6 as a microRNA sponge that helps modulate human pluripotency and early lineage differentiation.

Bradley Cairns, Douglas Carrell, Stephen Tapscott and colleagues transcriptionally profile human oocytes and preimplantation embryos and highlight DUX4-family proteins as activators of cleavage-stage genes and repetitive elements. They show that Dux expression converts mouse embryonic stem cells into two-cell (2C) embryo-like cells, thus suggesting mouse DUX and human DUX4 as drivers of the mammalian cleavage/2C state. To better understand transcriptional regulation during human oogenesis and preimplantation development, we defined stage-specific transcription, which highlighted the cleavage stage as being highly distinctive. Here, we present multiple lines of evidence that a eutherian-specific multicopy retrogene, DUX4 , encodes a transcription factor that activates hundreds of endogenous genes (for example, ZSCAN4 , KDM4E and PRAMEF-family genes) and retroviral elements (MERVL/HERVL family) that define the cleavage-specific transcriptional programs in humans and mice. Remarkably, mouse Dux expression is both necessary and sufficient to convert mouse embryonic stem cells (mESCs) into 2-cell-embryo-like ('2C-like') cells, measured here by the reactivation of '2C' genes and repeat elements, the loss of POU5F1 (also known as OCT4) protein and chromocenters, and the conversion of the chromatin landscape (as assessed by transposase-accessible chromatin using sequencing (ATAC–seq)) to a state strongly resembling that of mouse 2C embryos. Thus, we propose mouse DUX and human DUX4 as major drivers of the cleavage or 2C state.

The basic helix–loop–helix (bHLH) family of transcription factors recognizes DNA motifs known as E-boxes (CANNTG) and includes 108 members 1 . Here we investigate how chromatinized E-boxes are engaged by two structurally diverse bHLH proteins: the proto-oncogene MYC-MAX and the circadian transcription factor CLOCK-BMAL1 (refs. 2 , 3 ). Both transcription factors bind to E-boxes preferentially near the nucleosomal entry–exit sites. Structural studies with engineered or native nucleosome sequences show that MYC-MAX or CLOCK-BMAL1 triggers the release of DNA from histones to gain access. Atop the H2A–H2B acidic patch 4 , the CLOCK-BMAL1 Per-Arnt-Sim (PAS) dimerization domains engage the histone octamer disc. Binding of tandem E-boxes 5 – 7 at endogenous DNA sequences occurs through direct interactions between two CLOCK-BMAL1 protomers and histones and is important for circadian cycling. At internal E-boxes, the MYC-MAX leucine zipper can also interact with histones H2B and H3, and its binding is indirectly enhanced by OCT4 elsewhere on the nucleosome. The nucleosomal E-box position and the type of bHLH dimerization domain jointly determine the histone contact, the affinity and the degree of competition and cooperativity with other nucleosome-bound factors. Cryo-EM structures and analysis provide insight into the mechanisms by which basic helix–loop–helix transcription factors access E-box DNA sequences that are embedded within nucleosomes, and cooperate with other transcription factors.

CRISPR-Cas9 genome editing is a promising technique for clinical applications, such as the correction of disease-associated alleles in somatic cells. The use of this approach has also been discussed in the context of heritable editing of the human germ line. However, studies assessing gene correction in early human embryos report low efficiency of mutation repair, high rates of mosaicism, and the possibility of unintended editing outcomes that may have pathologic consequences. We developed computational pipelines to assess single-cell genomics and transcriptomics datasets from OCT4 (POU5F1) CRISPR-Cas9–targeted and control human preimplantation embryos. This allowed us to evaluate on-target mutations that would be missed by more conventional genotyping techniques. We observed loss of heterozygosity in edited cells that spanned regions beyond the POU5F1 on-target locus, as well as segmental loss and gain of chromosome 6, on which the POU5F1 gene is located. Unintended genome editing outcomes were present in ∼16% of the human embryo cells analyzed and spanned 4–20 kb. Our observations are consistent with recent findings indicating complexity at on-target sites following CRISPR-Cas9 genome editing. Our work underscores the importance of further basic research to assess the safety of genome editing techniques in human embryos, which will inform debates about the potential clinical use of this technology.

Single-cell proteomics (SCP) promises to revolutionize biomedicine by providing an unparalleled view of the proteome in individual cells. Here, we present a high-sensitivity SCP workflow named Chip-Tip, identifying >5,000 proteins in individual HeLa cells. It also facilitated direct detection of post-translational modifications in single cells, making the need for specific post-translational modification-enrichment unnecessary. Our study demonstrates the feasibility of processing up to 120 label-free SCP samples per day. An optimized tissue dissociation buffer enabled effective single-cell disaggregation of drug-treated cancer cell spheroids, refining overall SCP analysis. Analyzing nondirected human-induced pluripotent stem cell differentiation, we consistently quantified stem cell markers OCT4 and SOX2 in human-induced pluripotent stem cells and lineage markers such as GATA4 (endoderm), HAND1 (mesoderm) and MAP2 (ectoderm) in different embryoid body cells. Our workflow sets a benchmark in SCP for sensitivity and throughput, with broad applications in basic biology and biomedicine for identification of cell type-specific markers and therapeutic targets. Chip-Tip is a label-free quantification-based single-cell proteomics workflow for deep single-cell proteomics, which identifies over 5,000 proteins and 40,000 peptides in single HeLa cells.