bims-crepig Biomed News
on Chromatin regulation and epigenetics in cell fate and cancer
Issue of 2020‒03‒29
fifty-two papers selected by
Connor Rogerson
University of Cambridge, MRC Cancer Unit


  1. Mol Reprod Dev. 2020 Mar 25.
    Zhou Q, Meng QR, Meng TG, He QL, Zhao ZH, Li QN, Lei WL, Liu SZ, Schatten H, Wang ZB, Sun QY.
      BRG1-associated factor 250a (BAF250a) is a component of the SWI/SNF adenosine triphosphate-dependent chromatin remodeling complex, which has been shown to control chromatin structure and transcription. BAF250a was reported to be a key component of the gene regulatory machinery in embryonic stem cells controlling self-renewal, differentiation, and cell lineage decisions. Here we constructed Baf250aF/F ;Gdf9-cre (Baf250aCKO ) mice to specifically delete BAF250a in oocytes to investigate the role of maternal BAF250a in female germ cells and embryo development. Our results showed that BAF250a deletion did not affect folliculogenesis, ovulation, and fertilization, but it caused late embryonic death. RNA sequencing analysis showed that the expression of genes involved in cell proliferation and differentiation, tissue morphogenesis, histone modification, and nucleosome remodeling were perturbed in Baf250aCKO MII oocytes. We showed that covalent histone modifications such as H3K27me3 and H3K27ac were also significantly affected in oocytes, which may reduce oocyte quality and lead to birth defects. In addition, the DNA methylation level of Igf2r, Snrpn, and Peg3 differentially methylated regions was decreased in Baf250aCKO oocytes. Quantitative real-time polymerase chain reaction analysis showed that the relative messenger RNA (mRNA) expression levels of Igf2r and Snrpn were significantly increased. The mRNA expression level of Dnmt1, Dnmt3a, Dnmt3l, and Uhrf1 was decreased, and the protein expression in these genes was also reduced, which might be the cause for impaired imprinting establishment. In conclusion, our results demonstrate that BAF250a plays an important role in oocyte transcription regulation, epigenetic modifications, and embryo development.
    Keywords:  BAF250a; SWI/SNF complex; epigenetic modification; oocyte maturation
    DOI:  https://doi.org/10.1002/mrd.23339
  2. Gene. 2020 Mar 18. pii: S0378-1119(20)30275-4. [Epub ahead of print] 144606
    Hori N, Kubo S, Sakasegawa T, Sakurai C, Hatsuzawa K.
      DNA demethylation and suppression of de novo DNA methylation are activities that maintain hypomethylation. However, the strength of these two activities at the same locus has not been separately estimated. The association between these two activities and hypomethylation remains unclear. Octamer-binding transcription factors-binding sequences (OBSs) and CCCTC-binding factor (CTCF)-binding sequences (CBSs) within the mouse H19-imprinted control region (ICR) are involved in the induction of DNA demethylation and maintenance of hypomethylation in mouse undifferentiated embryonic cell lines. To reveal the association between the two cis-elements and the two hypomethylation maintenance activities in maintaining ICR hypomethylation, we evaluated altered DNA methylation levels at sites that were initially completely- or un-methylated using a stable transfection-based assay, and estimated the strength of the two hypomethylation maintenance activities separately via a Poisson process model that described the DNA methylation state regulatory process. Although DNA demethylation depending on OBSs affected almost the entire ICR, DNA demethylation depending on CBSs occurred near CBSs, resulting in CBS regions redundantly demethylated. Detailed analysis of the CBS4 region suggested that OBSs were required to induce both hypomethylation maintenance activities and that CBSs-dependent activities contributed, but diminished during incubation when protection of the CBS4 region by OBSs-dependent activities was absent. Analysis via the Poisson process model indicated that hypomethylation at the CBS4 region was maintained by OBSs-dependent suppression of de novo DNA methylation rather than DNA demethylation. We propose that the hierarchical regulation of redundant protection of the CBS region via cooperation between two hypomethylation maintenance activities is a potential function of the ICR that effectively maintains allele-specific methylation status in the same DNA sequence.
    Keywords:  CTCF-binding sequence; Cis-acting element; Direct bisulfite sequencing; Octamer-binding transcription factor-binding sequence; Poisson process model; Sox-Oct motif
    DOI:  https://doi.org/10.1016/j.gene.2020.144606
  3. Cell Rep. 2020 Mar 24. pii: S2211-1247(20)30295-3. [Epub ahead of print]30(12): 3989-3995.e4
    Bar-Ziv R, Brodsky S, Chapal M, Barkai N.
      Genome replication perturbs the DNA regulatory environment by displacing DNA-bound proteins, replacing nucleosomes, and introducing dosage imbalance between regions replicating at different S-phase stages. Recently, we showed that these effects are integrated to maintain transcription homeostasis: replicated genes increase in dosage, but their expression remains stable due to replication-dependent epigenetic changes that suppress transcription. Here, we examine whether reduced transcription from replicated DNA results from limited accessibility to regulatory factors by measuring the time-resolved binding of RNA polymerase II (Pol II) and specific transcription factors (TFs) to DNA during S phase in budding yeast. We show that the Pol II binding pattern is largely insensitive to DNA dosage, indicating limited binding to replicated DNA. In contrast, binding of three TFs (Reb1, Abf1, and Rap1) to DNA increases with the increasing DNA dosage. We conclude that the replication-specific chromatin environment remains accessible to regulatory factors but suppresses RNA polymerase recruitment.
    Keywords:  DNA; RNA polymerase; chromatin; replication; transcription; transcription factor
    DOI:  https://doi.org/10.1016/j.celrep.2020.02.114
  4. Genes Dev. 2020 Mar 26.
    Lu D, Sin HS, Lu C, Fuller MT.
      Cell type-specific transcriptional programs that drive differentiation of specialized cell types are key players in development and tissue regeneration. One of the most dramatic changes in the transcription program in Drosophila occurs with the transition from proliferating spermatogonia to differentiating spermatocytes, with >3000 genes either newly expressed or expressed from new alternative promoters in spermatocytes. Here we show that opening of these promoters from their closed state in precursor cells requires function of the spermatocyte-specific tMAC complex, localized at the promoters. The spermatocyte-specific promoters lack the previously identified canonical core promoter elements except for the Inr. Instead, these promoters are enriched for the binding site for the TALE-class homeodomain transcription factors Achi/Vis and for a motif originally identified under tMAC ChIP-seq peaks. The tMAC motif resembles part of the previously identified 14-bp β2UE1 element critical for spermatocyte-specific expression. Analysis of downstream sequences relative to transcription start site usage suggested that ACA and CNAAATT motifs at specific positions can help promote efficient transcription initiation. Our results reveal how promoter-proximal sequence elements that recruit and are acted upon by cell type-specific chromatin binding complexes help establish a robust, cell type-specific transcription program for terminal differentiation.
    Keywords:  Drosophila; core promoter elements; spermatogenesis; tMAC; transcription
    DOI:  https://doi.org/10.1101/gad.335331.119
  5. Nat Genet. 2020 Mar 23.
    Izzo F, Lee SC, Poran A, Chaligne R, Gaiti F, Gross B, Murali RR, Deochand SD, Ang C, Jones PW, Nam AS, Kim KT, Kothen-Hill S, Schulman RC, Ki M, Lhoumaud P, Skok JA, Viny AD, Levine RL, Kenigsberg E, Abdel-Wahab O, Landau DA.
      Mutations in genes involved in DNA methylation (DNAme; for example, TET2 and DNMT3A) are frequently observed in hematological malignancies1-3 and clonal hematopoiesis4,5. Applying single-cell sequencing to murine hematopoietic stem and progenitor cells, we observed that these mutations disrupt hematopoietic differentiation, causing opposite shifts in the frequencies of erythroid versus myelomonocytic progenitors following Tet2 or Dnmt3a loss. Notably, these shifts trace back to transcriptional priming skews in uncommitted hematopoietic stem cells. To reconcile genome-wide DNAme changes with specific erythroid versus myelomonocytic skews, we provide evidence in support of differential sensitivity of transcription factors due to biases in CpG enrichment in their binding motif. Single-cell transcriptomes with targeted genotyping showed similar skews in transcriptional priming of DNMT3A-mutated human clonal hematopoiesis bone marrow progenitors. These data show that DNAme shapes the topography of hematopoietic differentiation, and support a model in which genome-wide methylation changes are transduced to differentiation skews through biases in CpG enrichment of the transcription factor binding motif.
    DOI:  https://doi.org/10.1038/s41588-020-0595-4
  6. Nat Genet. 2020 Mar 16.
    Iwafuchi M, Cuesta I, Donahue G, Takenaka N, Osipovich AB, Magnuson MA, Roder H, Seeholzer SH, Santisteban P, Zaret KS.
      Gene network transitions in embryos and other fate-changing contexts involve combinations of transcription factors. A subset of fate-changing transcription factors act as pioneers; they scan and target nucleosomal DNA and initiate cooperative events that can open the local chromatin. However, a gap has remained in understanding how molecular interactions with the nucleosome contribute to the chromatin-opening phenomenon. Here we identified a short α-helical region, conserved among FOXA pioneer factors, that interacts with core histones and contributes to chromatin opening in vitro. The same domain is involved in chromatin opening in early mouse embryos for normal development. Thus, local opening of chromatin by interactions between pioneer factors and core histones promotes genetic programming.
    DOI:  https://doi.org/10.1038/s41588-020-0591-8
  7. Transl Oncol. 2020 Mar 21. pii: S1936-5233(20)30005-X. [Epub ahead of print]13(4): 100758
    Sun C, Xiao L, Zhao Y, Shi J, Yuan Y, Gu Y, Zhang F, Gao X, Yang Y, Yang R, Qin J, Zhang J, Wang C, Wang Y, Wang Z, Hu P, Chang T, Wang L, Wang G, Chen H, Li Z, Ye J.
      Isocitrate dehydrogenase (IDH) mutations occur frequently in lower-grade gliomas, which result in genome-wide epigenetic alterations. The wild-type IDH1 is reported to participate in lipid biosynthesis and amino acid metabolism, but its role in tumorigenesis is still unclear. In this study, the expressions of IDH1 and podoplanin (Pdpn) were determined in IDH-mutated and IDH-wild-type gliomas, and their relationships in glioma were further analyzed. In addition, the regulation of wild-type IDH1 and mutant IDH1 on Pdpn expression was investigated by luciferase assays and promoter methylation analysis. Our study showed that Pdpn was almost undetectable in IDH-mutated glioma but strongly expressed in higher-grade IDH-wild-type glioma. Pdpn overexpression promoted the migration of glioma cells but had little effect on cell growth. Moreover, Pdpn expression was positively correlated with the increased wild-type IDH1 levels in IDH-wild-type glioma. Consistently, the wild-type IDH1 greatly promoted the transcription and expression of Pdpn, but the mutant IDH1 and D-2-hydroxyglutarate significantly suppressed Pdpn expression in glioma cells. Besides, our results revealed that the methylation of CpG islands in the Pdpn promoter was opposingly regulated by wild-type and mutant IDH1 in glioma. Collectively, our results indicated that wild-type and mutant IDH1 opposingly controlled the Pdpn expression in glioma by regulating its promoter methylation, which provides a basis for understanding the relationship between wild-type and mutant IDH1 in epigenetic regulation and tumorigenesis.
    DOI:  https://doi.org/10.1016/j.tranon.2020.100758
  8. Stem Cell Res. 2020 Mar 17. pii: S1873-5061(20)30075-1. [Epub ahead of print]44 101771
    Jung YJ, Park W, Noh JM, Kang KP, Nguyen-Thanh T, Han MK, Kim W.
      SIRT1 (NAD+-dependent deacetylase) plays a suppressive role during the late stages of adipogenesis. However, the effects of SIRT1 on the early phases of adipogenic differentiation from embryonic stem cells (ESCs) are poorly understood. We employed Sirt1+/+ and Sirt1-/- mouse embryonic stem cells (mESCs) to evaluate the role of SIRT1 during the early stage mESC differentiation to adipocytes in response to retinoic acid (RA) treatment. Treatment with EX527 (a SIRT1 inhibitor) during the early phase and SIRT1 knockout both significantly diminished differentiation to mature adipocytes. Expressions of marker genes of preadipocytes, brown adipocytes, and brite cells were significantly lower in Sirt1-/- mESCs than in Sirt1+/+ mESCs. Furthermore, SIRT1 knockout reduced RA-induced RA receptor (RAR)α and RARβ mRNA and protein expressions during early adipocyte differentiation. Nuclear receptor corepressor 1 (NCOR1), a negative regulator of RAR signaling, expression, and acetylation levels were higher in Sirt1-/- than in Sirt1+/+ mESCs. After RA treatment, chromatin immunoprecipitation assays using an antibody against NCOR1, revealed that NCOR1 binding to RARβ promoters was significantly lower in Sirt1-/- mESCs than in Sirt1+/+ mESCs, and luciferase reporter assays showed SIRT1 knockdown decreased RA-induced RARα activity. Taken together, these observations show SIRT1 is required during the early phase of mESC adipogenesis and that SIRT1 deficiency inhibits adipogenesis by increasing NCOR1 acetylation and down-regulating the expressions of RARα and RARβ.
    Keywords:  Adipogenesis; Embryonic stem cell; NCOR1; SIRT1
    DOI:  https://doi.org/10.1016/j.scr.2020.101771
  9. Oncogene. 2020 Mar 23.
    Liu J, He D, Cheng L, Huang C, Zhang Y, Rao X, Kong Y, Li C, Zhang Z, Liu J, Jones K, Napier D, Lee EY, Wang C, Liu X.
      Blockade of programmed death-ligand 1 (PD-L1) by therapeutic antibodies has shown to be a promising strategy in cancer therapy, yet clinical response in many types of cancer, including prostate cancer (PCa), is limited. Tumor cells secrete PD-L1 through exosomes or splice variants, which has been described as a new mechanism for the resistance to PD-L1 blockade therapy in multiple cancers, including PCa. This suggests that cutting off the secretion or expression of PD-L1 might improve the response rate of PD-L1 blockade therapy in PCa treatment. Here we report that p300/CBP inhibition by a small molecule p300/CBP inhibitor dramatically enhanced the efficacy of PD-L1 blockade treatment in a syngeneic model of PCa by blocking both the intrinsic and IFN-γ-induced PD-L1 expression. Mechanistically, p300/CBP could be recruited to the promoter of CD274 (encoding PD-L1) by the transcription factor IRF-1, which induced the acetylation of Histone H3 at CD274 promoter followed by the transcription of CD274. A485, a p300/CBP inhibitor, abrogated this process and cut off the secretion of exosomal PD-L1 by blocking the transcription of CD274, which combined with the anti-PD-L1 antibody to reactivate T cells function for tumor attack. This finding reports a new mechanism of how cancer cells regulate PD-L1 expression through epigenetic factors and provides a novel therapeutic approach to enhance the efficacy of immune checkpoint inhibitors treatment.
    DOI:  https://doi.org/10.1038/s41388-020-1270-z
  10. Mol Metab. 2020 Feb 15. pii: S2212-8778(20)30008-9. [Epub ahead of print] 100942
    Wiese M, Bannister AJ.
      BACKGROUND: Virtually all eukaryotic cells contain spatially distinct genomes, a single nuclear genome that harbours the vast majority of genes and much smaller genomes found in mitochondria present at thousands of copies per cell. To generate a coordinated gene response to various environmental cues, the genomes must communicate with each another. Much of this bi-directional crosstalk relies on epigenetic processes, including DNA, RNA, and histone modification pathways. Crucially, these pathways, in turn depend on many metabolites generated in specific pools throughout the cell, including the mitochondria. They also involve the transport of metabolites as well as the enzymes that catalyse these modifications between nuclear and mitochondrial genomes.SCOPE OF REVIEW: This study examines some of the molecular mechanisms by which metabolites influence the activity of epigenetic enzymes, ultimately affecting gene regulation in response to metabolic cues. We particularly focus on the subcellular localisation of metabolite pools and the crosstalk between mitochondrial and nuclear proteins and RNAs. We consider aspects of mitochondrial-nuclear communication involving histone proteins, and potentially their epigenetic marks, and discuss how nuclear-encoded enzymes regulate mitochondrial function through epitranscriptomic pathways involving various classes of RNA molecules within mitochondria.
    MAJOR CONCLUSIONS: Epigenetic communication between nuclear and mitochondrial genomes occurs at multiple levels, ultimately ensuring a coordinated gene expression response between different genetic environments. Metabolic changes stimulated, for example, by environmental factors, such as diet or physical activity, alter the relative abundances of various metabolites, thereby directly affecting the epigenetic machinery. These pathways, coupled to regulated protein and RNA transport mechanisms, underpin the coordinated gene expression response. Their overall importance to the fitness of a cell is highlighted by the identification of many mutations in the pathways we discuss that have been linked to human disease including cancer.
    Keywords:  Chromatin; Enzymes; Epigenetics; Histones; Metabolites; Mitochondria; RNA modification
    DOI:  https://doi.org/10.1016/j.molmet.2020.01.006
  11. Int J Biol Sci. 2020 ;16(8): 1324-1334
    Gao L, Yang M, Wei Z, Gu M, Yang L, Bai C, Wu Y, Li G.
      Myostatin (MSTN) is mostly expressed in skeletal muscle and plays crucial roles in the negative regulation of muscle mass development. The methylation and demethylation of myogenesis-specific genes are major regulatory factors in muscle satellite cell differentiation. The present study was designed to investigate the mechanism of myogenic differentiation regulated by MSTN mutation (MT) and the methylation/demethylation state of downstream genes. The results showed that, in the MSTN -/+ satellite cells, a higher myotube fusion index and a larger myotube length were observed compared to the wild type controls; the genes associated with myogenesis were all up-regulated compared to the WT controls. The methylation of the promoters and gene bodies of PAX3, PAX7, MyoD, and MyoG were all down-regulated, while the expression of the key demethylase TET1 was significantly promoted. ChIP-qPCR was used to demonstrate that the SMAD2/SMAD3 complex combined with the promoter of TET1 to inhibit the activity of TET1 promoter, indicating that MSTN may regulate TET1 via SMAD2/SMAD3. The overexpression of TET1 in wild type cells promoted myogenic differentiation, increased the myotube index, and reduced the methylation of the associated genes. On the contrary, the knockdown of TET1 in the MSTN mutant cells resulted in the opposite phenomena as in the overexpressed cells. In conclusion, the myostatin mutant showed an increased transcriptional activity of TET1, inducing higher levels of demethylation and improving the transcriptional activity levels of myogenic differentiation-associated genes. The binding of SMAD2/SMAD3 directly to the TET1 promoter region indicated that the MSTN mutant demethylated the myogenesis-specific genes by up-regulating TET1, which is directly controlled by SMAD2/SMAD3.
    Keywords:  DNA methylation; MSTN mutant; SMAD2/SMAD3; myogenic differentiation; ten-eleven translocation methylcytosine dioxygenase 1 (TET1)
    DOI:  https://doi.org/10.7150/ijbs.40551
  12. Mol Cell. 2020 Mar 17. pii: S1097-2765(20)30150-7. [Epub ahead of print]
    Hsieh TS, Cattoglio C, Slobodyanyuk E, Hansen AS, Rando OJ, Tjian R, Darzacq X.
      Whereas folding of genomes at the large scale of epigenomic compartments and topologically associating domains (TADs) is now relatively well understood, how chromatin is folded at finer scales remains largely unexplored in mammals. Here, we overcome some limitations of conventional 3C-based methods by using high-resolution Micro-C to probe links between 3D genome organization and transcriptional regulation in mouse stem cells. Combinatorial binding of transcription factors, cofactors, and chromatin modifiers spatially segregates TAD regions into various finer-scale structures with distinct regulatory features including stripes, dots, and domains linking promoters-to-promoters (P-P) or enhancers-to-promoters (E-P) and bundle contacts between Polycomb regions. E-P stripes extending from the edge of domains predominantly link co-expressed loci, often in the absence of CTCF and cohesin occupancy. Acute inhibition of transcription disrupts these gene-related folding features without altering higher-order chromatin structures. Our study uncovers previously obscured finer-scale genome organization, establishing functional links between chromatin folding and gene regulation.
    Keywords:  30 nm chromatin fiber; 3D genome; CTCF; Micro-C; Pol II; TAD; enhancer-promoter (E-P) interactions; loop extrusion; transcription
    DOI:  https://doi.org/10.1016/j.molcel.2020.03.002
  13. Nat Cell Biol. 2020 Mar 23.
    Lu Y, Wu T, Gutman O, Lu H, Zhou Q, Henis YI, Luo K.
      TAZ promotes growth, development and tumorigenesis by regulating the expression of target genes. However, the manner in which TAZ orchestrates the transcriptional responses is poorly defined. Here we demonstrate that TAZ forms nuclear condensates through liquid-liquid phase separation to compartmentalize its DNA-binding cofactor TEAD4, coactivators BRD4 and MED1, and the transcription elongation factor CDK9 for transcription. TAZ forms phase-separated droplets in vitro and liquid-like nuclear condensates in vivo, and this ability is negatively regulated by Hippo signalling through LATS-mediated phosphorylation and is mediated by the coiled-coil (CC) domain. Deletion of the TAZ CC domain or substitution with the YAP CC domain prevents the phase separation of TAZ and its ability to induce the expression of TAZ-specific target genes. Thus, we identify a mechanism of transcriptional activation by TAZ and demonstrate that pathway-specific transcription factors also engage the phase-separation mechanism for efficient and specific transcriptional activation.
    DOI:  https://doi.org/10.1038/s41556-020-0485-0
  14. Bioengineered. 2020 Dec;11(1): 449-462
    Li QM, Li JL, Feng ZH, Lin HC, Xu Q.
      Human dental pulp cells (hDPCs) possess the capacity to differentiate into odontoblast-like cells in response to exogenous stimuli. Histone methylation is one of the most robust epigenetic marks and is essential for the regulation of multiple cellular processes. Previous studies have shown that histone methyltransferases (HMTs) and histone demethylases (HDMs) are crucial for the osteogenic differentiation of human bone marrow, adipose tissue, and tooth tissue. However, little is known about the role of histone methylation in hDPC differentiation. Here, the expression levels of HMTs and HDMs were profiled in hDPCs undergoing odontogenic induction. Among several differentially expressed enzymes, HDM KDM5A demonstrated significantly enhanced expression during cytodifferentiation. Furthermore, KDM5A expression increased during early passages and in a time-dependent manner during odontogenic induction. Using a shRNA-expressing lentivirus, KDM5A was knocked down in hDPCs. KDM5A depletion resulted in greater alkaline phosphatase activity and more mineral deposition formation. Meanwhile, the expression levels of the odontogenic markers DMP1, DSPP, OSX, and OCN were increased by KDM5A knockdown. As a histone demethylase specific for tri- and dimethylated histone H3 at lysine 4 (H3K4me3/me2), KDM5A deficiency led to a significant increment in total H3K4me3 levels, whereas no significant difference was found for H3K4 me2. H3K4me3 levels on the promoters of the odontogenic markers increased after KDM5A knockdown in hDPCs. These results demonstrated that KDM5A is present in hDPCs and inhibits the odontogenic differentiation potentiality of hDPCs by removing H3K4me3 from specific gene promoters, suggesting that KDM5A-dependent histone demethylation may play an important role in reparative dentinogenesis.
    Keywords:  H3K4me3; KDM5A; histone methylation; human dental pulp cells; odontogenic differentiation
    DOI:  https://doi.org/10.1080/21655979.2020.1743536
  15. Cancer Res. 2020 Mar 25. pii: canres.2104.2019. [Epub ahead of print]
    Bruschi M, Garnier L, Cleroux E, Giordano A, Dumas M, Bardet AF, Kergrohen T, Quesada S, Cesses P, Weber M, Gerbe F, Jay P.
      Colorectal cancer (CRC) initiation and progression result from the accumulation of genetic and epigenetic alterations. Although aberrant gene expression and DNA methylation profiles are considered hallmarks of CRC development, the precise timing at which these are produced during tumor establishment remains elusive. Here we investigated the early transcriptional and epigenetic changes induced by Apc inactivation in intestinal crypts. Hyper-activation of the Wnt pathway via Apc inactivation in crypt base columnar (CBC) intestinal stem cells (ISC) led to their rapid accumulation driven by an impaired molecular commitment to differentiation, which was associated with discrete alterations in DNA methylation. Importantly, inhibiting the enzymes responsible for de novo DNA methylation restored the responsiveness of Apc-deficient intestinal organoids to stimuli regulating the proliferation-to-differentiation transition in ISC. This work reveals that early DNA methylation changes play critical roles in the establishment of the impaired fate decision program consecutive to Apc loss-of-function.
    DOI:  https://doi.org/10.1158/0008-5472.CAN-19-2104
  16. Nat Cell Biol. 2020 Mar 23.
    Zhao J, Wang M, Chang L, Yu J, Song A, Liu C, Huang W, Zhang T, Wu X, Shen X, Zhu B, Li G.
      Stable propagation of epigenetic information is important for maintaining cell identity in multicellular organisms. However, it remains largely unknown how mono-ubiquitinated histone H2A on lysine 119 (H2AK119ub1) is established and stably propagated during cell division. In this study, we found that the proteins RYBP and YAF2 each specifically bind H2AK119ub1 to recruit the RYBP-PRC1 or YAF2-PRC1 complex to catalyse the ubiquitination of H2A on neighbouring nucleosomes through a positive-feedback model. Additionally, we demonstrated that histone H1-compacted chromatin enhances the distal propagation of H2AK119ub1, thereby reinforcing the inheritance of H2AK119ub1 during cell division. Moreover, we showed that either disruption of RYBP/YAF2-PRC1 activity or impairment of histone H1-dependent chromatin compaction resulted in a significant defect of the maintenance of H2AK119ub1. Therefore, our results suggest that histone H1-dependent chromatin compaction plays a critical role in the stable propagation of H2AK119ub1 by RYBP/YAF2-PRC1 during cell division.
    DOI:  https://doi.org/10.1038/s41556-020-0484-1
  17. Genes Dev. 2020 Mar 26.
    Ignatova VV, Stolz P, Kaiser S, Gustafsson TH, Lastres PR, Sanz-Moreno A, Cho YL, Amarie OV, Aguilar-Pimentel A, Klein-Rodewald T, Calzada-Wack J, Becker L, Marschall S, Kraiger M, Garrett L, Seisenberger C, Hölter SM, Borland K, Van De Logt E, Jansen PWTC, Baltissen MP, Valenta M, Vermeulen M, Wurst W, Gailus-Durner V, Fuchs H, de Angelis MH, Rando OJ, Kellner SM, Bultmann S, Schneider R.
      Covalent chemical modifications of cellular RNAs directly impact all biological processes. However, our mechanistic understanding of the enzymes catalyzing these modifications, their substrates and biological functions, remains vague. Amongst RNA modifications N6-methyladenosine (m6A) is widespread and found in messenger (mRNA), ribosomal (rRNA), and noncoding RNAs. Here, we undertook a systematic screen to uncover new RNA methyltransferases. We demonstrate that the methyltransferase-like 5 (METTL5) protein catalyzes m6A in 18S rRNA at position A1832 We report that absence of Mettl5 in mouse embryonic stem cells (mESCs) results in a decrease in global translation rate, spontaneous loss of pluripotency, and compromised differentiation potential. METTL5-deficient mice are born at non-Mendelian rates and develop morphological and behavioral abnormalities. Importantly, mice lacking METTL5 recapitulate symptoms of patients with DNA variants in METTL5, thereby providing a new mouse disease model. Overall, our biochemical, molecular, and in vivo characterization highlights the importance of m6A in rRNA in stemness, differentiation, development, and diseases.
    Keywords:  m6A; methyltransferase; pluripotency
    DOI:  https://doi.org/10.1101/gad.333369.119
  18. Nat Commun. 2020 Mar 24. 11(1): 1545
    Sarkar TJ, Quarta M, Mukherjee S, Colville A, Paine P, Doan L, Tran CM, Chu CR, Horvath S, Qi LS, Bhutani N, Rando TA, Sebastiano V.
      Aging is characterized by a gradual loss of function occurring at the molecular, cellular, tissue and organismal levels. At the chromatin level, aging associates with progressive accumulation of epigenetic errors that eventually lead to aberrant gene regulation, stem cell exhaustion, senescence, and deregulated cell/tissue homeostasis. Nuclear reprogramming to pluripotency can revert both the age and the identity of any cell to that of an embryonic cell. Recent evidence shows that transient reprogramming can ameliorate age-associated hallmarks and extend lifespan in progeroid mice. However, it is unknown how this form of rejuvenation would apply to naturally aged human cells. Here we show that transient expression of nuclear reprogramming factors, mediated by expression of mRNAs, promotes a rapid and broad amelioration of cellular aging, including resetting of epigenetic clock, reduction of the inflammatory profile in chondrocytes, and restoration of youthful regenerative response to aged, human muscle stem cells, in each case without abolishing cellular identity.
    DOI:  https://doi.org/10.1038/s41467-020-15174-3
  19. Cell Rep. 2020 Mar 24. pii: S2211-1247(20)30231-X. [Epub ahead of print]30(12): 4165-4178.e7
    Yang M, Lin X, Segers F, Suganthan R, Hildrestrand GA, Rinholm JE, Aas PA, Sousa MML, Holm S, Bolstad N, Warren D, Berge RK, Johansen RF, Yndestad A, Kristiansen E, Klungland A, Luna L, Eide L, Halvorsen B, Aukrust P, Bjørås M.
      Oxidation resistance gene 1 (OXR1) protects cells against oxidative stress. We find that male mice with brain-specific isoform A knockout (Oxr1A-/-) develop fatty liver. RNA sequencing of male Oxr1A-/- liver indicates decreased growth hormone (GH) signaling, which is known to affect liver metabolism. Indeed, Gh expression is reduced in male mice Oxr1A-/- pituitary gland and in rat Oxr1A-/- pituitary adenoma cell-line GH3. Oxr1A-/- male mice show reduced fasting-blood GH levels. Pull-down and proximity ligation assays reveal that OXR1A is associated with arginine methyl transferase PRMT5. OXR1A-depleted GH3 cells show reduced symmetrical dimethylation of histone H3 arginine 2 (H3R2me2s), a product of PRMT5 catalyzed methylation, and chromatin immunoprecipitation (ChIP) of H3R2me2s shows reduced Gh promoter enrichment. Finally, we demonstrate with purified proteins that OXR1A stimulates PRMT5/MEP50-catalyzed H3R2me2s. Our data suggest that OXR1A is a coactivator of PRMT5, regulating histone arginine methylation and thereby GH production within the pituitary gland.
    Keywords:  Arginine Methylation; Growth hormone; H3R2me2s; NAFLD; Non-alcoholic fatty liver disease; OXR1; Oxidation resistance gene 1; PRMT1; PRMT5; brain-liver axis; epigenetic regulation; neuroendocrine regulation; pituitary gland; protein arginine methyltransferase
    DOI:  https://doi.org/10.1016/j.celrep.2020.02.063
  20. Mol Metab. 2020 Feb 14. pii: S2212-8778(20)30002-8. [Epub ahead of print] 100936
    Allum F, Grundberg E.
      BACKGROUND: Metabolic diseases such as obesity are known to be driven by both environmental and genetic factors. Although genome-wide association studies of common variants and their impact on complex traits have provided some biological insight into disease etiology, identified genetic variants have been found to contribute only a small proportion to disease heritability, and to map mainly to non-coding regions of the genome. To link variants to function, association studies of cellular traits, such as epigenetic marks, in disease-relevant tissues are commonly applied.SCOPE OF THE REVIEW: We review large-scale efforts to generate genome-wide maps of coordinated epigenetic marks and their utility in complex disease dissection with a focus on DNA methylation. We contrast DNA methylation profiling methods and discuss the advantages of using targeted methods for single-base resolution assessments of methylation levels across tissue-specific regulatory regions to deepen our understanding of contributing factors leading to complex diseases.
    MAJOR CONCLUSIONS: Large-scale assessments of DNA methylation patterns in metabolic disease-linked study cohorts have provided insight into the impact of variable epigenetic variants in disease etiology. In-depth profiling of epigenetic marks at regulatory regions, particularly at tissue-specific elements, will be key to dissect the genetic and environmental components contributing to metabolic disease onset and progression.
    Keywords:  Adipose tissue; DNA methylation; Epigenomics; Metabolic diseases; Next-generation sequencing; Regulatory elements
    DOI:  https://doi.org/10.1016/j.molmet.2019.12.016
  21. Gene. 2020 Mar 18. pii: S0378-1119(20)30262-6. [Epub ahead of print] 144593
    Beacon TH, Xu W, Davie JR.
      Protein arginine methyltransferase 1 (PRMT1) and the product of this enzyme (histone H4 asymmetrically dimethylated at Arg 3; H4R3me2a) are important in the establishment and maintenance of chicken and murine erythrocyte transcriptionally active chromatin. Silencing the expression of PRMT1 results in loss of acetylated histones H3 and H4 and methylated H3K4 and prevents erythropoiesis. Here, we show that H4R3me2a and the PRMT5-catalyzed histone H3 symmetrically dimethylated at Arg 2 (H3R2me2s) locate largely to introns of expressed genes and intergenic regions, with both marks co-localizing in the chicken polychromatic erythrocyte genome. H4R3me2a and H3R2me2s were associated with histone marks of active promoters and enhancers, as well as with the body of genes that have an atypical chromatin structure, with nucleosome depleted regions. H4R3me2a co-localized with acetylated H3K27. Previous studies have shown that PRMT1 was bound to CBP/p300, suggesting a role of PRMT1-mediated H4R3me2a in CBP/p300 recruitment and H3K27 acetylation. Moreover, PRMT1 might be a key enzyme affected when S-adenosyl methionine levels are reduced in metabolic disorders.
    Keywords:  Chromatin; Histone acetylation; Histone arginine methylation; Hypomethylation; Nucleosome; Protein arginine methyl transferase
    DOI:  https://doi.org/10.1016/j.gene.2020.144593
  22. Nat Struct Mol Biol. 2020 Mar 16.
    Han X, Yu D, Gu R, Jia Y, Wang Q, Jaganathan A, Yang X, Yu M, Babault N, Zhao C, Yi H, Zhang Q, Zhou MM, Zeng L.
      BRD4, a major tandem-bromodomain-containing transcription regulator, has two isoforms. The long isoform (BRD4L) has an extended C terminus that binds transcription cofactors, while the short isoform (BRD4S) lacks this C-terminal extension. Unlike BRD4L, the role of BRD4S in gene transcription remains unclear. Here, we report that, in human cancer cells, BRD4S forms nuclear puncta that possess liquid-like properties and that colocalize with BRD4L, MED1 and sites of histone H3 lysine 27 acetylation. BRD4 puncta are correlated with BRD4S but not BRD4L expression levels. BRD4S knockdown reduces BRD4S condensation, and ectopic expression promotes puncta formation and target gene transcription. BRD4S nuclear condensation is mediated by its intrinsically disordered regions and binding of its bromodomains to DNA and acetylated chromatin, respectively, and BRD4S phosphorylation diminishes BRD4 condensation. Our study illuminates a previously unappreciated role of BRD4S in organizing chromatin and transcription factors through phase separation to sustain gene transcription in chromatin for cancer cell proliferation.
    DOI:  https://doi.org/10.1038/s41594-020-0394-8
  23. Genes Dis. 2020 Jun;7(2): 172-184
    Wang Y, Dong C, Zhou BP.
      Epithelial-mesenchymal Transition (EMT) is a de-differentiation program that imparts tumor cells with the phenotypic and cellular plasticity required for drug resistance, metastasis, and recurrence. This dynamic and reversible events is governed by a network of EMT-transcription factors (EMT-TFs) through epigenetic regulation. Many chromatin modifying-enzymes utilize metabolic intermediates as cofactors or substrates; this suggests that EMT is subjected to the metabolic regulation. Conversely, EMT rewires metabolic program to accommodate cellular changes during EMT. Here we summarize the latest findings regarding the epigenetic regulation of EMT, and discuss the mutual interactions among metabolism, epigenetic regulation, and EMT. Finally, we provide perspectives of how this interplay contributes to cellular plasticity, which may result in the clinical manifestation of tumor heterogeneity.
    Keywords:  Epigenetics; Epithelial-mesenchymal transition; Heterogeneity; Metabolism; Plasticity
    DOI:  https://doi.org/10.1016/j.gendis.2019.09.012
  24. Front Immunol. 2020 ;11 414
    Gong H, Tai H, Huang N, Xiao P, Mo C, Wang X, Han X, Zhou J, Chen H, Tang X, Zhao T, Xu W, Gong C, Zhang G, Yang Y, Wang S, Xiao H.
      Signal transducer and activator of transcription 3 (STAT3) is implicated in inflammation processing, but the mechanism of its regulation mostly remains limited to Janus kinase (JAK)-mediated phosphorylation. Although AMP-activated protein kinase (AMPK)-mediated STAT3 inactivation has got documented, the molecular signaling cascade connecting STAT3 inactivation and the anti-inflammatory role of AMPK is far from established. In the present study, we addressed the interplay between AMPK and STAT3, and revealed the important role of STAT3 inactivation in the anti-inflammatory function of AMPK in lipopolysaccharide-stressed macrophages and mice. Firstly, we found that pharmacological inhibition of STAT3 can improve the anti-inflammatory effect of AMPK in wild-type mice, and the expression of STAT3 in macrophage of mice is a prerequisite for the anti-inflammatory effect of AMPK. As to the molecular signaling cascade linking AMPK to STAT3, we disclosed that AMPK suppressed STAT3 not only by attenuating JAK signaling but also by activating nuclear factor erythroid-2-related factor-2 (Nrf2), a redox-regulating transcription factor, which consequently increased the expression of small heterodimer protein (SHP), thus repressing the transcriptional activity of STAT3. In summary, this study provided a unique set of evidence showing the relationship between AMPK and STAT3 signaling and explored a new mechanism of AMPK-driven STAT3 inactivation that involves Nrf2-SHP signaling cascade. These findings expand our understanding of the interplay between pro- and anti-inflammatory signaling pathways and are beneficial for the therapeutic development of sepsis treatments.
    Keywords:  AMPK; LPS; Nrf2; SHP; STAT3; inflammation
    DOI:  https://doi.org/10.3389/fimmu.2020.00414
  25. Nat Methods. 2020 Mar 16.
    Xie L, Dong P, Chen X, Hsieh TS, Banala S, De Marzio M, English BP, Qi Y, Jung SK, Kieffer-Kwon KR, Legant WR, Hansen AS, Schulmann A, Casellas R, Zhang B, Betzig E, Lavis LD, Chang HY, Tjian R, Liu Z.
      To image the accessible genome at nanometer scale in situ, we developed three-dimensional assay for transposase-accessible chromatin-photoactivated localization microscopy (3D ATAC-PALM) that integrates an assay for transposase-accessible chromatin with visualization, PALM super-resolution imaging and lattice light-sheet microscopy. Multiplexed with oligopaint DNA-fluorescence in situ hybridization (FISH), RNA-FISH and protein fluorescence, 3D ATAC-PALM connected microscopy and genomic data, revealing spatially segregated accessible chromatin domains (ACDs) that enclose active chromatin and transcribed genes. Using these methods to analyze genetically perturbed cells, we demonstrated that genome architectural protein CTCF prevents excessive clustering of accessible chromatin and decompacts ACDs. These results highlight 3D ATAC-PALM as a useful tool to probe the structure and organizing mechanism of the genome.
    DOI:  https://doi.org/10.1038/s41592-020-0775-2
  26. Mol Cell. 2020 Mar 13. pii: S1097-2765(20)30152-0. [Epub ahead of print]
    Haws SA, Yu D, Ye C, Wille CK, Nguyen LC, Krautkramer KA, Tomasiewicz JL, Yang SE, Miller BR, Liu WH, Igarashi K, Sridharan R, Tu BP, Cryns VL, Lamming DW, Denu JM.
      S-adenosylmethionine (SAM) is the methyl-donor substrate for DNA and histone methyltransferases that regulate epigenetic states and subsequent gene expression. This metabolism-epigenome link sensitizes chromatin methylation to altered SAM abundance, yet the mechanisms that allow organisms to adapt and protect epigenetic information during life-experienced fluctuations in SAM availability are unknown. We identified a robust response to SAM depletion that is highlighted by preferential cytoplasmic and nuclear mono-methylation of H3 Lys 9 (H3K9) at the expense of broad losses in histone di- and tri-methylation. Under SAM-depleted conditions, H3K9 mono-methylation preserves heterochromatin stability and supports global epigenetic persistence upon metabolic recovery. This unique chromatin response was robust across the mouse lifespan and correlated with improved metabolic health, supporting a significant role for epigenetic adaptation to SAM depletion in vivo. Together, these studies provide evidence for an adaptive response that enables epigenetic persistence to metabolic stress.
    Keywords:  SAM; aging; chromatin; epigenetics; histone; metabolism; methionine; methylation; persistence
    DOI:  https://doi.org/10.1016/j.molcel.2020.03.004
  27. Cell Rep. 2020 Mar 24. pii: S2211-1247(20)30299-0. [Epub ahead of print]30(12): 4152-4164.e6
    Cao X, Chen Y, Wu B, Wang X, Xue H, Yu L, Li J, Wang Y, Wang W, Xu Q, Mao H, Peng C, Han G, Chen CD.
      Histone methyl groups can be removed by demethylases. Although LSD1 and JmjC domain-containing proteins have been identified as histone demethylases, enzymes for many histone methylation states or sites are still unknown. Here, we perform a screening of a cDNA library containing 2,500 nuclear proteins and identify hHR23A as a histone H4K20 demethylase. Overexpression of hHR23A reduces the levels of H4K20me1/2/3 in cells. In vitro, hHR23A specifically demethylates H4K20me1/2/3 and generates formaldehyde. The enzymatic activity requires Fe(II) and α-ketoglutarate as cofactors and the UBA domains of hHR23A. hHR23B, a protein homologous to hHR23A, also demethylates H4K20me1/2/3 in vitro and in vivo. We further demonstrate that hHR23A/B activate the transcription of coding genes by demethylating H4K20me1 and the transcription of repetitive elements by demethylating H4K20me3. Nuclear magnetic resonance (NMR) analyses demonstrate that an HxxxE motif in the UBA1 domain is crucial for iron binding and demethylase activity. Thus, we identify two hHR23 proteins as histone demethylases.
    Keywords:  H4K20 demethylase; H4K20 methylation; UBA domain-containing proteins; histone demethylase
    DOI:  https://doi.org/10.1016/j.celrep.2020.03.001
  28. Mol Metab. 2020 Feb 12. pii: S2212-8778(20)30023-5. [Epub ahead of print] 100951
    Lindermayr C, Rudolf EE, Durner J, Groth M.
      BACKGROUND: One of the fascinating aspects of epigenetic regulation is that it provides means to rapidly adapt to environmental change. This is particularly relevant in the plant kingdom, where most species are sessile and exposed to increasing habitat fluctuations due to global warming. Although the inheritance of epigenetically controlled traits acquired through environmental impact is a matter of debate, it is well documented that environmental cues lead to epigenetic changes, including chromatin modifications, that affect cell differentiation or are associated with plant acclimation and defense priming. Still, in most cases, the mechanisms involved are poorly understood. An emerging topic that promises to reveal new insights is the interaction between epigenetics and metabolism.SCOPE OF REVIEW: This study reviews the links between metabolism and chromatin modification, in particular histone acetylation, histone methylation, and DNA methylation, in plants and compares them to examples from the mammalian field, where the relationship to human diseases has already generated a larger body of literature. This study particularly focuses on the role of reactive oxygen species (ROS) and nitric oxide (NO) in modulating metabolic pathways and gene activities that are involved in these chromatin modifications. As ROS and NO are hallmarks of stress responses, we predict that they are also pivotal in mediating chromatin dynamics during environmental responses.
    MAJOR CONCLUSIONS: Due to conservation of chromatin-modifying mechanisms, mammals and plants share a common dependence on metabolic intermediates that serve as cofactors for chromatin modifications. In addition, plant-specific non-CG methylation pathways are particularly sensitive to changes in folate-mediated one-carbon metabolism. Finally, reactive oxygen and nitrogen species may fine-tune epigenetic processes and include similar signaling mechanisms involved in environmental stress responses in plants as well as animals.
    Keywords:  Chromatin; DNA methylation; Folate metabolism; Histone modification; Methionine cycle; Nitric oxide; Plants; Reactive oxygen species; Redox modification
    DOI:  https://doi.org/10.1016/j.molmet.2020.01.015
  29. Nat Chem Biol. 2020 Mar 23.
    Musheev MU, Baumgärtner A, Krebs L, Niehrs C.
      The proposal that N6-methyl-deoxyadenosine (m6dA) acts as an epigenetic mark in mammals remains controversial. Using isotopic labeling coupled to ultrasensitive mass spectrometry, we confirm the presence of low-level m6dA in mammalian DNA. However, the bulk of genomic m6dA originates from ribo-N6-methyladenosine, which is processed via the nucleotide-salvage pathway and misincorporated by DNA polymerases. Our results argue against m6dA acting as a heritable, epigenetic DNA mark in mammalian cells.
    DOI:  https://doi.org/10.1038/s41589-020-0504-2
  30. Mol Cell. 2020 Mar 19. pii: S1097-2765(20)30146-5. [Epub ahead of print]77(6): 1159-1161
    Kriaucionis S, Klose RJ.
      Distal regulatory elements control gene expression during differentiation. In this issue of Molecular Cell, Barnett et al. (2020) develop a new technology, called ATAC-Me, and discover that removal of DNA methylation is not a pre-requisite for the creation of accessible chromatin at active gene regulatory elements during cellular differentiation.
    DOI:  https://doi.org/10.1016/j.molcel.2020.02.026
  31. Mol Metab. 2020 Feb 14. pii: S2212-8778(20)30007-7. [Epub ahead of print] 100941
    Trefely S, Lovell CD, Snyder NW, Wellen KE.
      BACKGROUND: Many metabolites serve as important signalling molecules to adjust cellular activities and functions based on nutrient availability. Links between acetyl-CoA metabolism, histone lysine acetylation, and gene expression have been documented and studied over the past decade. In recent years, several additional acyl modifications to histone lysine residues have been identified, which depend on acyl-coenzyme A thioesters (acyl-CoAs) as acyl donors. Acyl-CoAs are intermediates of multiple distinct metabolic pathways, and substantial evidence has emerged that histone acylation is metabolically sensitive. Nevertheless, the metabolic sources of acyl-CoAs used for chromatin modification in most cases remain poorly understood. Elucidating how these diverse chemical modifications are coupled to and regulated by cellular metabolism is important in deciphering their functional significance.SCOPE OF REVIEW: In this article, we review the metabolic pathways that produce acyl-CoAs, as well as emerging evidence for functional roles of diverse acyl-CoAs in chromatin regulation. Because acetyl-CoA has been extensively reviewed elsewhere, we will focus on four other acyl-CoA metabolites integral to major metabolic pathways that are also known to modify histones: succinyl-CoA, propionyl-CoA, crotonoyl-CoA, and butyryl-CoA. We also briefly mention several other acyl-CoA species, which present opportunities for further research; malonyl-CoA, glutaryl-CoA, 3-hydroxybutyryl-CoA, 2-hydroxyisobutyryl-CoA, and lactyl-CoA. Each acyl-CoA species has distinct roles in metabolism, indicating the potential to report shifts in the metabolic status of the cell. For each metabolite, we consider the metabolic pathways in which it participates and the nutrient sources from which it is derived, the compartmentalisation of its metabolism, and the factors reported to influence its abundance and potential nuclear availability. We also highlight reported biological functions of these metabolically-linked acylation marks. Finally, we aim to illuminate key questions in acyl-CoA metabolism as they relate to the control of chromatin modification.
    MAJOR CONCLUSIONS: A majority of acyl-CoA species are annotated to mitochondrial metabolic processes. Since acyl-CoAs are not known to be directly transported across mitochondrial membranes, they must be synthesized outside of mitochondria and potentially within the nucleus to participate in chromatin regulation. Thus, subcellular metabolic compartmentalisation likely plays a key role in the regulation of histone acylation. Metabolite tracing in combination with targeting of relevant enzymes and transporters will help to map the metabolic pathways that connect acyl-CoA metabolism to chromatin modification. The specific function of each acyl-CoA may be determined in part by biochemical properties that affect its propensity for enzymatic versus non-enzymatic protein modification, as well as the various enzymes that can add, remove and bind each modification. Further, competitive and inhibitory effects of different acyl-CoA species on these enzymes make determining the relative abundance of acyl-CoA species in specific contexts important to understand the regulation of chromatin acylation. An improved and more nuanced understanding of metabolic regulation of chromatin and its roles in physiological and disease-related processes will emerge as these questions are answered.
    Keywords:  Acyl-CoA; Acylation; Compartmentalisation; Histone; Metabolism
    DOI:  https://doi.org/10.1016/j.molmet.2020.01.005
  32. Nat Genet. 2020 Mar 23.
    Kloetgen A, Thandapani P, Ntziachristos P, Ghebrechristos Y, Nomikou S, Lazaris C, Chen X, Hu H, Bakogianni S, Wang J, Fu Y, Boccalatte F, Zhong H, Paietta E, Trimarchi T, Zhu Y, Van Vlierberghe P, Inghirami GG, Lionnet T, Aifantis I, Tsirigos A.
      Differences in three-dimensional (3D) chromatin architecture can influence the integrity of topologically associating domains (TADs) and rewire specific enhancer-promoter interactions, impacting gene expression and leading to human disease. Here we investigate the 3D chromatin architecture in T cell acute lymphoblastic leukemia (T-ALL) by using primary human leukemia specimens and examine the dynamic responses of this architecture to pharmacological agents. Systematic integration of matched in situ Hi-C, RNA-seq and CTCF ChIP-seq datasets revealed widespread differences in intra-TAD chromatin interactions and TAD boundary insulation in T-ALL. Our studies identify and focus on a TAD 'fusion' event associated with absence of CTCF-mediated insulation, enabling direct interactions between the MYC promoter and a distal super-enhancer. Moreover, our data also demonstrate that small-molecule inhibitors targeting either oncogenic signal transduction or epigenetic regulation can alter specific 3D interactions found in leukemia. Overall, our study highlights the impact, complexity and dynamic nature of 3D chromatin architecture in human acute leukemia.
    DOI:  https://doi.org/10.1038/s41588-020-0602-9
  33. R Soc Open Sci. 2020 Jan;7(1): 191048
    Karia D, Gilbert RCG, Biasutto AJ, Porcher C, Mancini EJ.
      Chromatin remodelling and transcription factors play important roles in lineage commitment and development through control of gene expression. Activation of selected lineage-specific genes and repression of alternative lineage-affiliated genes result in tightly regulated cell differentiation transcriptional programmes. However, the complex functional and physical interplay between transcription factors and chromatin-modifying enzymes remains elusive. Recent evidence has implicated histone demethylases in normal haematopoietic differentiation as well as in malignant haematopoiesis. Here, we report an interaction between H3K4 demethylase JARID1A and the haematopoietic-specific master transcription proteins SCL and GATA1 in red blood cells. Specifically, we observe a direct physical contact between GATA1 and the second PHD domain of JARID1A. This interaction has potential implications for normal and malignant haematopoiesis.
    Keywords:  haematopoiesis; histone demethylase; protein–protein interaction; transcription factors
    DOI:  https://doi.org/10.1098/rsos.191048
  34. Mol Cancer. 2020 Mar 24. 19(1): 64
    Yang X, Liu M, Li M, Zhang S, Hiju H, Sun J, Mao Z, Zheng M, Feng B.
      Empowered by recent advances of sequencing techniques, transcriptome-wide studies have characterized over 150 different types of post-transcriptional chemical modifications of RNA, ranging from methylations of single base to complex installing reactions catalyzed by coordinated actions of multiple modification enzymes. These modifications have been shown to regulate the function and fate of RNAs and further affecting various cellular events. However, the current understanding of their biological functions in human diseases, especially in cancers, is still limited. Once regarded as "junk" or "noise" of the transcriptome, noncoding RNA (ncRNA) has been proved to be involved in a plethora of cellular signaling pathways especially those regulating cancer initiation and progression. Accumulating evidence has demonstrated that ncRNAs manipulate multiple phenotypes of cancer cells including proliferation, metastasis and chemoresistance and may become promising biomarkers and targets for diagnosis and treatment of cancer. Importantly, recent studies have mapped plenty of modified residues in ncRNA transcripts, indicating the existence of epigenetic modulation of ncRNAs and the potential effects of RNA modulation on cancer progression. In this review, we briefly introduced the characteristics of several main epigenetic marks on ncRNAs and summarized their consecutive effects on cancer cells. We found that ncRNAs could act both as regulators and targets of epigenetic enzymes, which indicated a cross-regulating network in cancer cells and unveil a novel dimension of cancer biology. Moreover, by epitomizing the knowledge of RNA epigenetics, our work may pave the way for the design of patient-tailored therapeutics of cancers.
    Keywords:  Cancer progression; Cancer treatment; Noncoding RNA; RNA epigenetics
    DOI:  https://doi.org/10.1186/s12943-020-01159-9
  35. Curr Opin Genet Dev. 2020 Mar 17. pii: S0959-437X(20)30020-4. [Epub ahead of print]61 1-8
    Ibrahim DM, Mundlos S.
      The causal relationship between 3D chromatin domains and gene regulation has been of considerable debate in recent years. Initial Hi-C studies profiling the 3D chromatin structure of the genome described evolutionarily conserved Topologically Associating Domains (TADs) that correlated with gene expression. Subsequent evidence from mouse models and human disease directly linked TADs to gene regulation. However, a number of focused genetic and genome-wide studies questioned the relevance of 3D chromatin domains for orchestrating gene expression, ultimately yielding a more multi-layered view of 3D chromatin structure and gene regulation. We review the evidence for and against the importance of 3D chromatin structure for gene regulation and argue for a more comprehensive classification of regulatory chromatin domains that integrates 3D chromatin structure with genomic, functional, and evolutionary conservation.
    DOI:  https://doi.org/10.1016/j.gde.2020.02.015
  36. Sci Adv. 2020 03;6(12): eaay3324
    Omori H, Nishio M, Masuda M, Miyachi Y, Ueda F, Nakano T, Sato K, Mimori K, Taguchi K, Hikasa H, Nishina H, Tashiro H, Kiyono T, Mak TW, Nakao K, Nakagawa T, Maehama T, Suzuki A.
      Head-and-neck squamous cell carcinoma (HNSCC) is the sixth most common group of cancers in the world, and patients have a poor prognosis. Here, we present data indicating that YAP1 may be a strong driver of the onset and progression of oral SCC (OSCC), a major subtype of HNSCC. Mice with tongue-specific deletion of Mob1a/b and thus endogenous YAP1 hyperactivation underwent surprisingly rapid and highly reproducible tumorigenesis, developing tongue carcinoma in situ within 2 weeks and invasive SCC within 4 weeks. In humans, precancerous tongue dysplasia displays YAP1 activation correlating with reduced patient survival. Combinations of molecules mutated in OSCC may increase and sustain YAP1 activation to the point of oncogenicity. Strikingly, siRNA or pharmacological inhibition of YAP1 blocks murine OSCC onset in vitro and in vivo. Our work justifies targeting YAP1 as therapy for OSCC and perhaps HNSCC, and our mouse model represents a powerful tool for evaluating these agents.
    DOI:  https://doi.org/10.1126/sciadv.aay3324
  37. Nat Cell Biol. 2020 Mar 23.
    Nishida J, Momoi Y, Miyakuni K, Tamura Y, Takahashi K, Koinuma D, Miyazono K, Ehata S.
      Advanced clear cell renal cell carcinoma (ccRCC) frequently causes systemic inflammation. Recent studies have shown that cancer cells reshape the immune landscape by secreting cytokines or chemokines. This phenotype, called cancer-cell-intrinsic inflammation, triggers a metastatic cascade. Here, we identified the functional role and regulatory mechanism of inflammation driven by advanced ccRCC cells. The inflammatory nature of advanced ccRCC was recapitulated in a preclinical model of ccRCC. Amplification of cancer-cell-intrinsic inflammation during ccRCC progression triggered neutrophil-dependent lung metastasis. Massive expression of inflammation-related genes was transcriptionally activated by epigenetic remodelling through mechanisms such as DNA demethylation and super-enhancer formation. A bromodomain and extra-terminal motif inhibitor synchronously suppressed C-X-C-type chemokines in ccRCC cells and decreased neutrophil-dependent lung metastasis. Overall, our findings provide insight into the nature of inflammatory ccRCC, which triggers metastatic cascades, and suggest a potential therapeutic strategy.
    DOI:  https://doi.org/10.1038/s41556-020-0491-2
  38. Cells. 2020 Mar 24. pii: E789. [Epub ahead of print]9(3):
    Libetti D, Bernardini A, Sertic S, Messina G, Dolfini D, Mantovani R.
      NF-YA, the regulatory subunit of the trimeric transcription factor (TF) NF-Y, is regulated by alternative splicing (AS) generating two major isoforms, "long" (NF-YAl) and "short" (NF-YAs). Muscle cells express NF-YAl. We ablated exon 3 in mouse C2C12 cells by a four-guide CRISPR/Cas9n strategy, obtaining clones expressing exclusively NF-YAs (C2-YAl-KO). C2-YAl-KO cells grow normally, but are unable to differentiate. Myogenin and-to a lesser extent, MyoD- levels are substantially lower in C2-YAl-KO, before and after differentiation. Expression of the fusogenic Myomaker and Myomixer genes, crucial for the early phases of the process, is not induced. Myomaker and Myomixer promoters are bound by MyoD and Myogenin, and Myogenin overexpression induces their expression in C2-YAl-KO. NF-Y inactivation reduces MyoD and Myogenin, but not directly: the Myogenin promoter is CCAAT-less, and the canonical CCAAT of the MyoD promoter is not bound by NF-Y in vivo. We propose that NF-YAl, but not NF-YAs, maintains muscle commitment by indirectly regulating Myogenin and MyoD expression in C2C12 cells. These experiments are the first genetic evidence that the two NF-YA isoforms have functionally distinct roles.
    Keywords:  C2C12 cells; CRISPR-Cas9; NF-Y; exon deletion; muscle differentiation; splicing isoforms
    DOI:  https://doi.org/10.3390/cells9030789
  39. Cell Cycle. 2020 Mar 24. 1-11
    Liu W, Ji Y, Zhang B, Chu H, Yin C, Xiao Y.
      Previous studies reported that Stat5 promotes adipogenesis and white adipocyte differentiation. However, the role of Stat5 in brown adipocyte development is poorly understood. We found Stat5a was higher expressed in brown adipocytes than in white adipocytes, and its level was increased during the process of brown adipocyte differentiation. In addition, Stat5a expression was affected by cold stress and high-fat diet-feeding, suggesting a potential role in thermogenesis. Knockdown of Stat5a induced downregulation of brown fat specific genes (UCP1, PGC-1α, Acox-1 and Cidea), while overexpression of Stat5a did the opposite effect. What is more, bioinformatics analysis, ChIP assay and Luciferase activity assay all verified that Stat5a directly bind and transactivate Kdm6a promoter (Lysine-specific demethylase 6A). Further, we found that Stat5a overexpression promoted the expression of Kdm6a and inhibited the trimethylation of H3K27. While inhibiting of Kdm6a reversed the promoting effect of Stat5a overexpression on the expression of brown fat specific genes. Therefore, we conclude that Stat5a participated in brown adipocyte differentiation and thermogenic program through binding and transactivating the Kdm6a promoter.Abbreviations: Stat5: Signal transducers and activators of transcription 5; BAT: brown adipose tissue; WAT; white adipose tissue; eWAT: epididymal white adipose tissue; sWAT: subcutaneous white adipose tissue; SVFs: stromal vascular fractions; UCP1: Uncoupling protein 1; PGC-1α: Peroxisome proliferator-activated receptor gamma coactivator 1-alpha; Acox-1: Peroxisomal acyl-coenzyme A oxidase 1; Cidea: Cell death activator CIDE-A; ChIP: Chromatin Immunoprecipitation; HFD: High fat diet; FBS: Fetal bovine serum; siStat5a: Stat5a siRNA; siKdm6: Kdm6a siRNA; pcDNA-Stat5a: over expression of Stat5a pcDNA3.1 vector; IgG: mouse immunoglobulin G; Kdm6a: Lysine-specific demethylase 6A; H3K27me3: trimethylated H3K27.
    Keywords:  Stat5a/Kdm6a axis; brown adipocyte differentiation; thermogenic program
    DOI:  https://doi.org/10.1080/15384101.2020.1731644
  40. Biochem Biophys Res Commun. 2020 Mar 21. pii: S0006-291X(20)30571-4. [Epub ahead of print]
    Li C, Tan YH, Sun J, Deng FM, Liu YL.
      Aberrant activation of Hedgehog signaling is considered as the key player in hepatic stellate cell (HSC) activation involved in liver fibrosis (LF). The glioma-associated protein gene (GLI) has a predicted paired box 6 (PAX6)-binding site within its transcribed region. Therefore, this study aimed to investigate the relationship between PAX6 and GLI and their contribution to HSC activation and proliferation. PAX6 expression was upregulated in platelet-derived growth factor-BB (PDGF-BB)-induced LX-2 cells. The activation and proliferation of HSC were inhibited by interference of PAX6 with short hairpin RNA (shPAX6) via curbing Hedgehog signaling. Notably, PAX6 directly bound to the promoter sequence of GLI1 independent of the PTCH/SMO axis. Therefore, we propose that PAX6 upregulation induces HSC activation and proliferation through crosstalk with GLI1 signaling. Thus, these novel mechanistic insights involving the PAX6-mediated regulation of the activation and proliferation of HSC may provide a new therapeutic target for LF.
    Keywords:  Hedgehog; Hepatic stellate cell; Liver fibrosis; PAX6
    DOI:  https://doi.org/10.1016/j.bbrc.2020.03.086
  41. Cancer Res. 2020 Mar 26. pii: canres.3268.2019. [Epub ahead of print]
    Wong CH, Lou UK, Li Y, Chan SL, Tong JHM, To KF, Chen Y.
      The detailed biological functions of circular RNA (circRNA) are largely unexplored. Using circRNA sequencing, we identified 169 differentially expressed circRNA in pancreatic ductal adenocarcinoma (PDAC) cells compared to non-tumor human pancreatic ductal epithelial (HPDE) cells. Among them, circFOXK2 was validated with significant upregulation in PDAC cells and 63 % of primary tumors (53 out of 84). circFOXK2 promoted cell growth, migration, and invasion and was involved in cell cycle progression and apoptosis. circFOXK2 contained multiple miRNA binding sites, functioning as a sponge for miR-942, which in turn promoted expression of ANK1, GDNF, and PAX6. A novel and highly specific circRNA-pulldown followed by mass spectrometry analysis identified 94 circFOXK2-interacting proteins, which were involved in cell adhesion, mRNA splicing, and structural molecule activity. Of these, circFOKX2 interactions with YBX1 and hnRNPK enhanced expression of oncogenes NUF2 and PDXK. Knockdown of circFOXK2 reduced binding of YBX1 and hnRNPK to NUF2 and PDXK, in turn decreasing their expression. Collectively, our findings demonstrate that circFOXK2 in complex with YBX1 and hnRNPK promotes expression of oncogenic proteins that contribute to PDAC progression.
    DOI:  https://doi.org/10.1158/0008-5472.CAN-19-3268
  42. Biochem Biophys Res Commun. 2020 Mar 18. pii: S0006-291X(20)30532-5. [Epub ahead of print]
    Shen C, Chen JH, Oh H, Park JH.
      Elucidating the mechanism underlying osteoclast differentiation is important to improve our understanding of the pathophysiologies related to skeletal diseases and osteolytic metastasis in cancer. Sex-determining region Y-box containing gene 2 (SOX2), a stemness marker, is known to affect osteoblast differentiation and cancer metastasis. However, its role in osteoclastogenesis has not been investigated to date. Here, we report that SOX2 protein and mRNA expression was upregulated during osteoclast differentiation. The overexpression or knockdown of SOX2 in osteoclast precursor cells enhanced or suppressed, respectively, receptor activator of nuclear factor κB ligand (RANKL)-induced osteoclast differentiation and migration, and nuclear factor of activated T-cell c1 (NFATc1) and factor-associated suicide ligand (FASL) expression. In addition, epidermal growth factor receptor (EGFR) and extracellular signal-regulated kinase (ERK) activation were regulated by SOX2 expression; both EGFR and ERK inhibitors abrogated the SOX2 overexpression-induced increase in osteoclast differentiation and NFATc1 expression under RANKL stimulation. Overall, these results suggest SOX2 as a positive regulatory factor during osteoclast differentiation partly through the EGFR and ERK signaling pathways, highlighting a new potential target for restoring abnormal osteoclast activation.
    Keywords:  EGFR; Mitogen-activated protein kinases; NFATc1; Osteoclast; SOX2
    DOI:  https://doi.org/10.1016/j.bbrc.2020.03.052
  43. Genome Biol. 2020 Mar 23. 21(1): 66
    Li Y, Yang H, Zhang H, Liu Y, Shang H, Zhao H, Zhang T, Tu Q.
      Many differential gene expression analyses are conducted with an inadequate number of biological replicates. We describe an easy and effective RNA-seq approach using molecular barcoding to enable profiling of a large number of replicates simultaneously. This approach significantly improves the performance of differential gene expression analysis. Using this approach in medaka (Oryzias latipes), we discover novel genes with sexually dimorphic expression and genes necessary for germ cell development. Our results also demonstrate why the common practice of using only three replicates in differential gene expression analysis should be abandoned.
    Keywords:  Differential expression; Germ cell; Medaka; RNA-seq; Replication
    DOI:  https://doi.org/10.1186/s13059-020-01966-9
  44. PLoS Pathog. 2020 Mar 24. 16(3): e1008429
    Wang J, Li GL, Ming SL, Wang CF, Shi LJ, Su BQ, Wu HT, Zeng L, Han YQ, Liu ZH, Jiang DW, Du YK, Li XD, Zhang GP, Yang GY, Chu BB.
      Chromatin dynamics regulated by epigenetic modification is crucial in genome stability and gene expression. Various epigenetic mechanisms have been identified in the pathogenesis of human diseases. Here, we examined the effects of ten epigenetic agents on pseudorabies virus (PRV) infection by using GFP-reporter assays. Inhibitors of bromodomain protein 4 (BRD4), which receives much more attention in cancer than viral infection, was found to exhibit substantial anti-viral activity against PRV as well as a range of DNA and RNA viruses. We further demonstrated that BRD4 inhibition boosted a robust innate immune response. BRD4 inhibition also de-compacted chromatin structure and induced the DNA damage response, thereby triggering the activation of cGAS-mediated innate immunity and increasing host resistance to viral infection both in vitro and in vivo. Mechanistically, the inhibitory effect of BRD4 inhibition on viral infection was mainly attributed to the attenuation of viral attachment. Our findings reveal a unique mechanism through which BRD4 inhibition restrains viral infection and points to its potent therapeutic value for viral infectious diseases.
    DOI:  https://doi.org/10.1371/journal.ppat.1008429
  45. Front Plant Sci. 2020 ;11 262
    Hugues A, Jacobs CS, Roudier F.
      Maintenance of gene repression by Polycomb Repressive Complex 2 (PRC2) that catalyzes the trimethylation of histone H3 at lysine 27 (H3K27me3) is integral to the orchestration of developmental programs in most multicellular eukaryotes. Faithful inheritance of H3K27me3 patterns across replication ensures the stability of PRC2-mediated transcriptional silencing over cell generations, thereby safeguarding cellular identities. In this review, we discuss the molecular and mechanistic principles that underlie H3K27me3 restoration after the passage of the replication fork, considering recent advances in different model systems. In particular, we aim at emphasizing parallels and differences between plants and other organisms, focusing on the recycling of parental histones and the replenishment of H3K27me3 patterns post-replication thanks to the remarkable properties of the PRC2 complex. We then discuss the necessity for fine-tuning this genuine epigenetic memory system so as to allow for cell fate and developmental transitions. We highlight recent insights showing that genome-wide destabilization of the H3K27me3 landscape during chromatin replication participates in achieving this flexible stability and provides a window of opportunity for subtle transcriptional reprogramming.
    Keywords:  H3K27me3 inheritance; chromatin; epigenetic memory; polycomb repressive complex 2; replication
    DOI:  https://doi.org/10.3389/fpls.2020.00262
  46. Oncogene. 2020 Mar 24.
    Grassi ES, Pantazopoulou V, Pietras A.
      Glioblastoma multiforme is characterized in part by severe hypoxia associated with tumor necrosis. The cellular response to hypoxia can influence several properties of tumor cells associated with aggressive tumor growth, including metabolic adaptations and tumor cell migration and invasion. Here, we found that Delta Like Non-Canonical Notch Ligand 1 (DLK1) expression was elevated as compared with normal brain in a genetically engineered mouse model of glioma, and that DLK1 expression increased with tumor grade in human glioma samples. DLK1 expression was highest in hypoxic and perivascular tumor areas, and we found that hypoxia induced the release and nuclear translocation of an intracellular fragment of DLK1 in murine glioma as well as in human glioma cultures. Release of the intracellular fragment was dependent on ADAM17 and Hypoxia-inducible Factor 1alpha and 2alpha (HIF-1alpha/HIF-2alpha), as ADAM17 inhibitors and HIF1A/HIF2A siRNA blocked DLK1 cleavage. Expression of a cleavable form of DLK1 amplified several hypoxia-induced traits of glioma cells such as colony formation, stem cell marker gene expression, a PI3K-pathway-mediated metabolic shift, and enhanced invasiveness. Effects of DLK1 were dependent on DLK1-cleavage by ADAM17, as expression of non-cleavable DLK1 could not replicate the DLK1-induced hypoxic phenotype. Finally, forced expression of DLK1 resulted in more invasive tumor growth in a PDGFB-induced glioma mouse model without affecting overall survival. Together, our findings suggest a previously undescribed role for DLK1 as an intracellular signaling molecule.
    DOI:  https://doi.org/10.1038/s41388-020-1273-9
  47. Front Genet. 2020 ;11 117
    Yeh SJ, Chen SW, Chen BS.
      Colorectal cancer (CRC) is the third most commonly diagnosed type of cancer worldwide. The mechanisms leading to the progression of CRC are involved in both genetic and epigenetic regulations. In this study, we applied systems biology methods to identify potential biomarkers and conduct drug discovery in a computational approach. Using big database mining, we constructed a candidate protein-protein interaction network and a candidate gene regulatory network, combining them into a genome-wide genetic and epigenetic network (GWGEN). With the assistance of system identification and model selection approaches, we obtain real GWGENs for early-stage, mid-stage, and late-stage CRC. Subsequently, we extracted core GWGENs for each stage of CRC from their real GWGENs through a principal network projection method, and projected them to the Kyoto Encyclopedia of Genes and Genomes pathways for further analysis. Finally, we compared these core pathways resulting in different molecular mechanisms in each stage of CRC and identified carcinogenic biomarkers for the design of multiple-molecule drugs to prevent the progression of CRC. Based on the identified gene expression signatures, we suggested potential compounds combined with known CRC drugs to prevent the progression of CRC with querying Connectivity Map (CMap).
    Keywords:  colorectal cancer; drug discovery; genome-wide genetic and epigenetic network; system identification; system model selection; system modeling; systems biology
    DOI:  https://doi.org/10.3389/fgene.2020.00117
  48. Cognition. 2020 Mar 19. pii: S0010-0277(20)30085-8. [Epub ahead of print]200 104266
    Tong Y, Sun J, Wright ND, Li J.
      Despite intricate interactions between emotion and decision making, the underlying cognitive mechanisms that govern their relationship remain elusive. Recent theoretical and empirical advances suggest that preferences in risky decision making can arise from the computation of subjective utility (value-dependent) or direct approach-avoidance action tendencies (value-independent). Here, 48 participants performed two gambling tasks (accept/reject and choice selection tasks) under the emotion manipulation (neutral versus disgust) to investigate how decision context and emotion may influence risk preference via the value-dependent and -independent pathways. The results showed that the decision context affected the degree to which both value-dependent and -independent systems were engaged. Crucially, however, the disgust emotion had a selective effect on participants' choices in the accept/reject task. Furthermore, computational analyses revealed that this specific effect resulted from a reduced propensity to gamble for potential gains by engaging only the value-independent system. These results indicate dissociative effects of decision context and emotion and suggest a specific route by which disgust influences choice preference in risky decision making.
    Keywords:  Approach-avoidance; Decision making; Disgust; Emotion; Risk; Value-independent
    DOI:  https://doi.org/10.1016/j.cognition.2020.104266
  49. Genome Biol. 2020 Mar 26. 21(1): 79
    Trieu T, Martinez-Fundichely A, Khurana E.
      Non-coding variants have been shown to be related to disease by alteration of 3D genome structures. We propose a deep learning method, DeepMILO, to predict the effects of variants on CTCF/cohesin-mediated insulator loops. Application of DeepMILO on variants from whole-genome sequences of 1834 patients of twelve cancer types revealed 672 insulator loops disrupted in at least 10% of patients. Our results show mutations at loop anchors are associated with upregulation of the cancer driver genes BCL2 and MYC in malignant lymphoma thus pointing to a possible new mechanism for their dysregulation via alteration of insulator loops.
    Keywords:  3D genome; BCL2; Cancer; Deep learning; MYC; Non-coding mutation
    DOI:  https://doi.org/10.1186/s13059-020-01987-4
  50. Nature. 2020 Mar 25.
    Han X, Zhou Z, Fei L, Sun H, Wang R, Chen Y, Chen H, Wang J, Tang H, Ge W, Zhou Y, Ye F, Jiang M, Wu J, Xiao Y, Jia X, Zhang T, Ma X, Zhang Q, Bai X, Lai S, Yu C, Zhu L, Lin R, Gao Y, Wang M, Wu Y, Zhang J, Zhan R, Zhu S, Hu H, Wang C, Chen M, Huang H, Liang T, Chen J, Wang W, Zhang D, Guo G.
      Single-cell analysis is a valuable tool to dissect cellular heterogeneity in complex systems1. Yet, a comprehensive single-cell atlas has not been achieved for humans. We used single-cell mRNA sequencing to determine the cell-type composition of all major human organs and constructed a scheme for the human cell landscape (HCL). We revealed a single-cell hierarchy for many tissues that have not been well characterised. We established a 'single-cell HCL analysis' pipeline that helps to define human cell identity. Finally, we performed a single-cell comparative analysis of landscapes from both human and mouse to reveal the conserved genetic networks. We found that stem and progenitor cells exhibit strong transcriptomic stochasticity, while the differentiated cells are more distinct. Our study provides a valuable resource for human biology.
    DOI:  https://doi.org/10.1038/s41586-020-2157-4
  51. Leukemia. 2020 Mar 25.
    Kaiser A, Schmidt M, Huber O, Frietsch JJ, Scholl S, Heidel FH, Hochhaus A, Müller JP, Ernst T.
      Molecular alterations within the hematopoietic system influence cellular longevity and development of age-related myeloid stem-cell disorders like acute myeloid leukemia (AML) and chronic myeloid leukemia (CML). A reduced SIRT7-expression in aged murine hematopoietic stem cells (HSC) resulted in reduced longevity and increased proliferation. In this study we investigated age-related changes of SIRT7-expression in healthy humans and relevant pathomechanisms in AML and CML. SIRT7-expression in leukocytes of healthy people decreased in an age-dependent manner. Low SIRT7 mRNA levels were also detected in AML and CML patients. With positive treatment response, SIRT7-expression increased, but showed reduction when patients progressed or relapsed. Pharmacologic inhibition of driver mutations in AML (FLT3-ITD) or CML (BCR-ABL) also restored SIRT7 levels in cell lines and patient samples. Furthermore, SIRT7-expression increased with time during PMA-mediated monocyte differentiation of THP-1 cells. SIRT7-overexpression in THP-1 cells resulted in increased expression of differentiation markers. BCR-ABL, FLT3-ITD, and differentiation-associated SIRT7-expression in general were positively regulated by C/EBPα, -β, and -ε binding to two different C/EBP-binding sites within the SIRT7 promoter. SIRT7 is important in human hematopoietic cell aging and longevity. It might act as tumor suppressor and could potentially serve as general biomarker for monitoring treatment response in myeloid stem-cell disorders.
    DOI:  https://doi.org/10.1038/s41375-020-0803-3
  52. Nat Commun. 2020 Mar 24. 11(1): 1537
    Dorrity MW, Saunders LM, Queitsch C, Fields S, Trapnell C.
      Dimensionality reduction is often used to visualize complex expression profiling data. Here, we use the Uniform Manifold Approximation and Projection (UMAP) method on published transcript profiles of 1484 single gene deletions of Saccharomyces cerevisiae. Proximity in low-dimensional UMAP space identifies groups of genes that correspond to protein complexes and pathways, and finds novel protein interactions, even within well-characterized complexes. This approach is more sensitive than previous methods and should be broadly useful as additional transcriptome datasets become available for other organisms.
    DOI:  https://doi.org/10.1038/s41467-020-15351-4