Ten-Eleven Translocation 1 and 2 Confer Overlapping Transcriptional Programs for the Proliferation of Cultured Adult Neural Stem Cells

Induced hepatic stem cells maintain self-renewal through the high expression of Myc coregulated by TET1 and CTCF

Background

Induced hepatic stem cells (iHepSCs) with the capacities of self-renewal and bidifferentiation into hepatocytes and cholangiocytes were generated from mouse embryonic fibroblasts (MEFs) by lineage reprogramming in our previous research. However, the mechanism of iHepSC self-renewal has not been elucidated. Active demethylation regulated by Tet1 plays an important role in the self-renewal of stem cells, including pluripotent stem cells and adult stem cells. Here, we investigated the role and mechanism of Tet1-regulated demethylation in the self-renewal of iHepSCs.

Methods

The methylation levels and the expression of Tet1 in iHepSCs and MEFs were analyzed by immunofluorescent staining, quantitative reverse transcription PCR and western blotting. Then, the effects of Tet1 knockdown on the proliferation and self-renewal of iHepSCs were analyzed by CCK8, colony formation, and sphere formation assays. The mechanism by which Tet1 regulates the self-renewal of iHepSCs was investigated by chromatin immunoprecipitation, bisulfite sequence PCR, and methylation-sensitive restriction endonuclease-PCR.

Results

The high level of 5hmC and the low level of 5mC in iHepSCs were accompanied by high expression of Tet1. After Tet1 expression was knocked down by shRNA in iHepSCs, the proliferation and self-renewal capacities were inhibited, and the expression of Myc was also decreased. The higher expression level of Myc in iHepSCs maintained its self-renewal and was regulated by Tet1, which directly binds to CBS-1 and site A regions of the Myc promoter and demethylates the CpG cytosine. In addition, CTCF also binds to the CBS-1 and site A regions of the Myc promoter and regulates Myc expression along with TET1.

Conclusion

The self-renewal of iHepSCs was maintained by the higher expression of Myc, which was coregulated by TET1 and CTCF. This study may provide new insights into the self-renewal of stem cells, which can promote the research and application of ‘reprogrammed’ stem cells.

Tracing TET1 expression in prostate cancer: discovery of malignant cells with a distinct oncogenic signature

Background

Ten–eleven translocation methylcytosine dioxygenase 1 (TET1) is involved in DNA demethylation and transcriptional regulation, plays a key role in the maintenance of stem cell pluripotency, and is dysregulated in malignant cells. The identification of cancer stem cells (CSCs) driving tumor growth and metastasis is the primary objective of biomarker discovery in aggressive prostate cancer (PCa). In this context, we analyzed TET1 expression in PCa.

Methods

A large-scale immunohistochemical analysis of TET1 was performed in normal prostate (NOR) and PCa using conventional slides (50 PCa specimens) and tissue microarrays (669 NOR and 1371 PCa tissue cores from 371 PCa specimens). Western blotting, RT-qPCR, and 450 K methylation array analyses were performed on PCa cell lines. Genome-wide correlation, gene regulatory network, and functional genomics studies were performed using publicly available data sources and bioinformatics tools.

Results

In NOR, TET1 was exclusively expressed in normal cytokeratin 903 (CK903)–positive basal cells. In PCa, TET1 was frequently detected in alpha-methylacyl-CoA racemase (AMACR)–positive tumor cell clusters and was detectable at all tumor stages and Gleason scores. Pearson’s correlation analyses of PCa revealed 626 TET1-coactivated genes (r > 0.5) primarily encoding chromatin remodeling and mitotic factors. Moreover, signaling pathways regulating antiviral processes (62 zinc finger, ZNF, antiviral proteins) and the pluripotency of stem cells were activated. A significant proportion of detected genes exhibited TET1-correlated promoter hypomethylation. There were 161 genes encoding transcription factors (TFs), of which 133 were ZNF-TFs with promoter binding sites in TET1 and in the vast majority of TET1-coactivated genes.

Conclusions

TET1-expressing cells are an integral part of PCa and may represent CSCs with oncogenic potential.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13148-021-01201-7.

TET2 is involved in DNA hydroxymethylation, cell proliferation and inflammatory response in keratinocytes

DNA methylation and hydroxymethylation are the most common epigenetic modifications associated with the cell cycle and the inflammatory response. The present study aimed to investigate the role of 5-hydroxymethyl-cytosine (5-hmC) and ten-eleven translocation-2 (TET2) in keratinocytes. Following TET2 knockdown, dot blot analysis was performed to assess the levels of 5-hmC in keratinocytes, using HaCaT cells. Subsequently, the viability and cell cycle of HaCaT cells were assessed by MTT, Cell Counting Kit-8 assay and flow cytometric assays. Cyclin-dependent kinase inhibitor 2A and proinflammatory cytokine protein and mRNA expression levels were also detected. The present results suggested that TET2 may play an important role in regulating cellular proliferation by mediating DNA hydroxymethylation in HaCaT cells. In addition, TET2 knockdown decreased the production of proinflammatory cytokines, including lipocalin 2, S100 calcium binding protein A7, matrix metallopeptidase 9, C-X-C motif chemokine ligand 1, interferon regulatory factor 7 and interleukin-7 receptor. The present study suggested that TET2 regulated cell viability, apoptosis and the expression of inflammatory mediators in keratinocytes. Collectively, the results indicated that TET2 knockdown may relieve inflammatory responses in the skin.

Preterm Birth and the Risk of Neurodevelopmental Disorders - Is There a Role for Epigenetic Dysregulation?

Preterm Birth (PTB) accounts for approximately 11% of all births worldwide each year and is a profound physiological stressor in early life. The burden of neuropsychiatric and developmental impairment is high, with severity and prevalence correlated with gestational age at delivery. PTB is a major risk factor for the development of cerebral palsy, lower educational attainment and deficits in cognitive functioning, and individuals born preterm have higher rates of schizophrenia, autistic spectrum disorder and attention deficit/hyperactivity disorder. Factors such as gestational age at birth, systemic inflammation, respiratory morbidity, sub-optimal nutrition, and genetic vulnerability are associated with poor outcome after preterm birth, but the mechanisms linking these factors to adverse long term outcome are poorly understood. One potential mechanism linking PTB with neurodevelopmental effects is changes in the epigenome. Epigenetic processes can be defined as those leading to altered gene expression in the absence of a change in the underlying DNA sequence and include DNA methylation/hydroxymethylation and histone modifications. Such epigenetic modifications may be susceptible to environmental stimuli, and changes may persist long after the stimulus has ceased, providing a mechanism to explain the long-term consequences of acute exposures in early life. Many factors such as inflammation, fluctuating oxygenation and excitotoxicity which are known factors in PTB related brain injury, have also been implicated in epigenetic dysfunction. In this review, we will discuss the potential role of epigenetic dysregulation in mediating the effects of PTB on neurodevelopmental outcome, with specific emphasis on DNA methylation and the α-ketoglutarate dependent dioxygenase family of enzymes.

Decoding the role of TET family dioxygenases in lineage specification

Since the discovery of methylcytosine oxidase ten-eleven translocation (TET) proteins, we have witnessed an exponential increase in studies examining their roles in epigenetic regulation. TET family proteins catalyze the sequential oxidation of 5-methylcytosine (5mC) to oxidized methylcytosines including 5-hydroxymethylcytosine (5hmC), 5-formylcytosine, and 5-carboxylcytosine. TETs contribute to the regulation of lineage-specific gene expression via modulating DNA 5mC/5hmC balances at the proximal and distal regulatory elements of cell identity genes, and therefore enhance chromatin accessibility and gene transcription. Emerging evidence suggests that TET dioxygenases participate in the establishment and/or maintenance of hypomethylated bivalent domains at multiple differentiation-associated genes, and thus ensure developmental plasticity. Here, we review the current state of knowledge concerning TET family proteins, DNA hydroxymethylation, their distribution, and function in endoderm, mesoderm, and neuroectoderm specification. We will summarize the evidence pertaining to their crucial regulatory roles in lineage commitment and development.

Involvement of Nuclear Receptor REV-ERBβ in Formation of Neurites and Proliferation of Cultured Adult Neural Stem Cells

Neural stem cells (NSCs) serve as the source of both neurons and support cells, and neurogenesis is reportedly linked to the circadian clock. This study aimed to clarify the functional role of the circadian rhythm-related nuclear receptor, REV-ERBβ, in neurogenesis of NSCs from adult brain. Accordingly, Rev-erbβ expression and the effect of Rev-erbβ gene-specific knockdown on neurogenesis in vitro was examined in adult rodent NSCs. Initial experiments confirmed REV-ERBβ expression in cultured adult NSCs, while subsequent gene expression and gene ontogeny analyses identified functional genes upregulated or downregulated by REV-ERBβ. In particular, expression levels of factors associated with proliferation, stemness, and neural differentiation were affected. Knockdown of Rev-erbβ showed involvement of REV-ERBβ in regulation of cellular proliferation and self-renewal of cultured adult NSCs. Moreover, Rev-erbβ-knockdown cells formed neurons with a slightly shrunken morphology, fewer new primary neurites, and reduced length and branch formation of neurites. Altogether, this suggests that REV-ERBβ is involved in neurite formation during neuronal differentiation of cultured adult NSCs. In summary, REV-ERBβ is a known circadian regulatory protein that appears to be involved in neurogenesis via regulation of networks for cell proliferation and neural differentiation/maturation in adult NSCs.

A Critical Role of TET1/2 Proteins in Cell-Cycle Progression of Trophoblast Stem Cells

The ten-eleven translocation (TET) proteins are well known for their role in maintaining naive pluripotency of embryonic stem cells. Here, we demonstrate that, jointly, TET1 and TET2 also safeguard the self-renewal potential of trophoblast stem cells (TSCs) and have partially redundant roles in maintaining the epithelial integrity of TSCs. For the more abundantly expressed TET1, we show that this is achieved by binding to critical epithelial genes, notably E-cadherin, which becomes hyper-methylated and downregulated in the absence of TET1. The epithelial-to-mesenchymal transition phenotype of mutant TSCs is accompanied by centrosome duplication and separation defects. Moreover, we identify a role of TET1 in maintaining cyclin B1 stability, thereby acting as facilitator of mitotic cell-cycle progression. As a result, Tet1/2 mutant TSCs are prone to undergo endoreduplicative cell cycles leading to the formation of polyploid trophoblast giant cells. Taken together, our data reveal essential functions of TET proteins in the trophoblast lineage.

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TET1 and TET2 are critical for trophoblast stem cell (TSC) maintenance

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TET1 and TET2 safeguard TSC integrity by driving expression of epithelial genes

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TET1/2 null TSCs exhibit cell-cycle defects and become polyploid

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TET1 binds to and helps stabilize cyclin B1, thereby ensuring G2/M progression