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  • Online Resource  (9)
  • Proceedings of the National Academy of Sciences  (9)
  • Biodiversity Research  (9)
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  • Online Resource  (9)
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  • Proceedings of the National Academy of Sciences  (9)
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  • 1
    Online Resource
    Online Resource
    Human embryonic stem cells with biological and epigenetic characteristics similar to those of mouse ESCs
    Proceedings of the National Academy of Sciences ; 2010
    In:  Proceedings of the National Academy of Sciences Vol. 107, No. 20 ( 2010-05-18), p. 9222-9227
    Details
    In: Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 107, No. 20 ( 2010-05-18), p. 9222-9227
    Abstract: Human and mouse embryonic stem cells (ESCs) are derived from blastocyst-stage embryos but have very different biological properties, and molecular analyses suggest that the pluripotent state of human ESCs isolated so far corresponds to that of mouse-derived epiblast stem cells (EpiSCs). Here we rewire the identity of conventional human ESCs into a more immature state that extensively shares defining features with pluripotent mouse ESCs. This was achieved by ectopic induction of Oct4, Klf4, and Klf2 factors combined with LIF and inhibitors of glycogen synthase kinase 3β (GSK3β) and mitogen-activated protein kinase (ERK1/2) pathway. Forskolin, a protein kinase A pathway agonist which can induce Klf4 and Klf2 expression, transiently substitutes for the requirement for ectopic transgene expression. In contrast to conventional human ESCs, these epigenetically converted cells have growth properties, an X-chromosome activation state (XaXa), a gene expression profile, and a signaling pathway dependence that are highly similar to those of mouse ESCs. Finally, the same growth conditions allow the derivation of human induced pluripotent stem (iPS) cells with similar properties as mouse iPS cells. The generation of validated “naïve” human ESCs will allow the molecular dissection of a previously undefined pluripotent state in humans and may open up new opportunities for patient-specific, disease-relevant research.
    Type of Medium: Online Resource
    ISSN: 0027-8424 , 1091-6490
    URL: Article
    DOI: 10.1073/pnas.1004584107
    RVK:
    TA 1000
    RVK:
    WA 15000
    Language: English
    Publisher: Proceedings of the National Academy of Sciences
    Publication Date: 2010
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    detail.hit.zdb_id: 1461794-8
    SSG: 11
    SSG: 12
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    Online Resource
  • 2
    Online Resource
    Online Resource
    Histone H3K27ac separates active from poised enhancers and predicts developmental state
    Proceedings of the National Academy of Sciences ; 2010
    In:  Proceedings of the National Academy of Sciences Vol. 107, No. 50 ( 2010-12-14), p. 21931-21936
    Details
    In: Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 107, No. 50 ( 2010-12-14), p. 21931-21936
    Abstract: Developmental programs are controlled by transcription factors and chromatin regulators, which maintain specific gene expression programs through epigenetic modification of the genome. These regulatory events at enhancers contribute to the specific gene expression programs that determine cell state and the potential for differentiation into new cell types. Although enhancer elements are known to be associated with certain histone modifications and transcription factors, the relationship of these modifications to gene expression and developmental state has not been clearly defined. Here we interrogate the epigenetic landscape of enhancer elements in embryonic stem cells and several adult tissues in the mouse. We find that histone H3K27ac distinguishes active enhancers from inactive/poised enhancer elements containing H3K4me1 alone. This indicates that the amount of actively used enhancers is lower than previously anticipated. Furthermore, poised enhancer networks provide clues to unrealized developmental programs. Finally, we show that enhancers are reset during nuclear reprogramming.
    Type of Medium: Online Resource
    ISSN: 0027-8424 , 1091-6490
    URL: Article
    DOI: 10.1073/pnas.1016071107
    RVK:
    TA 1000
    RVK:
    WA 15000
    Language: English
    Publisher: Proceedings of the National Academy of Sciences
    Publication Date: 2010
    detail.hit.zdb_id: 209104-5
    detail.hit.zdb_id: 1461794-8
    SSG: 11
    SSG: 12
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    Online Resource
  • 3
    Online Resource
    Online Resource
    Human iPSC-derived microglia assume a primary microglia-like state after transplantation into the neonatal mouse brain
    Proceedings of the National Academy of Sciences ; 2019
    In:  Proceedings of the National Academy of Sciences Vol. 116, No. 50 ( 2019-12-10), p. 25293-25303
    Details
    In: Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 116, No. 50 ( 2019-12-10), p. 25293-25303
    Abstract: Microglia are essential for maintenance of normal brain function, with dysregulation contributing to numerous neurological diseases. Protocols have been developed to derive microglia-like cells from human induced pluripotent stem cells (hiPSCs). However, primary microglia display major differences in morphology and gene expression when grown in culture, including down-regulation of signature microglial genes. Thus, in vitro differentiated microglia may not accurately represent resting primary microglia. To address this issue, we transplanted microglial precursors derived in vitro from hiPSCs into neonatal mouse brains and found that the cells acquired characteristic microglial morphology and gene expression signatures that closely resembled primary human microglia. Single-cell RNA-sequencing analysis of transplanted microglia showed similar cellular heterogeneity as primary human cells. Thus, hiPSCs-derived microglia transplanted into the neonatal mouse brain assume a phenotype and gene expression signature resembling that of resting microglia residing in the human brain, making chimeras a superior tool to study microglia in human disease.
    Type of Medium: Online Resource
    ISSN: 0027-8424 , 1091-6490
    URL: Article
    DOI: 10.1073/pnas.1913541116
    RVK:
    TA 1000
    RVK:
    WA 15000
    Language: English
    Publisher: Proceedings of the National Academy of Sciences
    Publication Date: 2019
    detail.hit.zdb_id: 209104-5
    detail.hit.zdb_id: 1461794-8
    SSG: 11
    SSG: 12
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    Online Resource
  • 4
    Online Resource
    Online Resource
    X-linked H3K27me3 demethylase Utx is required for embryonic development in a sex-specific manner
    Proceedings of the National Academy of Sciences ; 2012
    In:  Proceedings of the National Academy of Sciences Vol. 109, No. 32 ( 2012-08-07), p. 13004-13009
    Details
    In: Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 109, No. 32 ( 2012-08-07), p. 13004-13009
    Abstract: Embryogenesis requires the timely and coordinated activation of developmental regulators. It has been suggested that the recently discovered class of histone demethylases (UTX and JMJD3) that specifically target the repressive H3K27me3 modification play an important role in the activation of “bivalent” genes in response to specific developmental cues. To determine the requirements for UTX in pluripotency and development, we have generated Utx -null ES cells and mutant mice. The loss of UTX had a profound effect during embryogenesis. Utx -null embryos had reduced somite counts, neural tube closure defects and heart malformation that presented between E9.5 and E13.5. Unexpectedly, homozygous mutant female embryos were more severely affected than hemizygous mutant male embryos. In fact, we observed the survival of a subset of UTX-deficient males that were smaller in size and had reduced lifespan. Interestingly, these animals were fertile with normal spermatogenesis. Consistent with a midgestation lethality, UTX-null male and female ES cells gave rise to all three germ layers in teratoma assays, though sex-specific differences could be observed in the activation of developmental regulators in embryoid body assays. Lastly, ChIP-seq analysis revealed an increase in H3K27me3 in Utx -null male ES cells. In summary, our data demonstrate sex-specific requirements for this X-linked gene while suggesting a role for UTY during development.
    Type of Medium: Online Resource
    ISSN: 0027-8424 , 1091-6490
    URL: Article
    DOI: 10.1073/pnas.1210787109
    RVK:
    TA 1000
    RVK:
    WA 15000
    Language: English
    Publisher: Proceedings of the National Academy of Sciences
    Publication Date: 2012
    detail.hit.zdb_id: 209104-5
    detail.hit.zdb_id: 1461794-8
    SSG: 11
    SSG: 12
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    Online Resource
  • 5
    Online Resource
    Online Resource
    Replication-competent Moloney murine leukemia virus carrying a bacterial suppressor tRNA gene: selective cloning of proviral and flanking host sequences.
    Proceedings of the National Academy of Sciences ; 1985
    In:  Proceedings of the National Academy of Sciences Vol. 82, No. 4 ( 1985-02), p. 1141-1145
    Details
    In: Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 82, No. 4 ( 1985-02), p. 1141-1145
    Abstract: A bacterial suppressor tRNA gene was introduced into the long terminal repeat of the Moloney murine leukemia virus (Mo-MuLV) proviral genome to construct a retrovirus that allows easy cloning of the provirus with flanking host sequences. A replication competent virus, Mo-MuLV sup containing a tRNA amber suppressor gene, was derived that replicates to high titers in tissue culture cells and stably transduces the bacterial gene. The recombinant virus can efficiently replicate in vivo when microinjected into midgestation embryos or when injected into newborn mice and displays the same tissue tropism as wild-type Mo-MuLV. The suppressor gene in Mo-MuLV sup is functional in bacteria and allows efficient recovery of proviral genomes. This was shown by ligation of DNA from infected cells to phage lambda Charon 4A arms and selective growth of recombinant phages on su- host cells. All recovered phages contained Mo-MuLV proviral sequences and, because of the high cloning capacity of phage lambda, 1-11 kilobases of flanking host DNA. This virus should facilitate studying virus-host interactions in tissue culture cells and in animals.
    Type of Medium: Online Resource
    ISSN: 0027-8424 , 1091-6490
    URL: Article
    DOI: 10.1073/pnas.82.4.1141
    RVK:
    TA 1000
    RVK:
    WA 15000
    Language: English
    Publisher: Proceedings of the National Academy of Sciences
    Publication Date: 1985
    detail.hit.zdb_id: 209104-5
    detail.hit.zdb_id: 1461794-8
    SSG: 11
    SSG: 12
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    Online Resource
  • 6
    Online Resource
    Online Resource
    Mutagenicity of 5-aza-2′-deoxycytidine is mediated by the mammalian DNA methyltransferase
    Proceedings of the National Academy of Sciences ; 1997
    In:  Proceedings of the National Academy of Sciences Vol. 94, No. 9 ( 1997-04-29), p. 4681-4685
    Details
    In: Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 94, No. 9 ( 1997-04-29), p. 4681-4685
    Abstract: The cytosine analog 5-aza-2′-deoxycytidine has been used clinically to reactivate genes silenced by DNA methylation. In particular, patients with β-thalassemia show fetal globin expression after administration of this hypomethylating drug. In addition, silencing of tumor suppressor gene expression by aberrant DNA methylation in tumor cells may potentially be reversed by a similar regimen. Consistent with its function in maintaining tumor suppressor gene expression, 5-aza-2′-deoxycytidine significantly reduces intestinal tumor multiplicity in the predisposed Min mouse strain. Despite its utility as an anti-cancer agent, the drug is highly mutagenic by an unknown mechanism. To gain insight into how 5-aza-2′-deoxycytidine induces mutations in vivo , we examined the mutational spectrum in an Escherichia coli lac I transgene in colonic DNA from 5-aza-2′-deoxycytidine-treated mice. Mutations induced by 5-aza-2′-deoxycytidine were predominantly at CpG dinucleotides, which implicates DNA methyltransferase in the mutagenic mechanism. C:G→G:C transversions were the predominant class of mutations observed. We suggest a model for how the mammalian DNA methyltransferase may be involved in facilitating these mutations. The observation that 5-aza-2′-deoxycytidine-induced mutations are mediated by the enzyme suggests that novel inhibitors of DNA methyltransferase, which can inactivate the enzyme before its interaction with DNA, are needed for chemoprevention or long term therapy.
    Type of Medium: Online Resource
    ISSN: 0027-8424 , 1091-6490
    URL: Article
    DOI: 10.1073/pnas.94.9.4681
    RVK:
    TA 1000
    RVK:
    WA 15000
    Language: English
    Publisher: Proceedings of the National Academy of Sciences
    Publication Date: 1997
    detail.hit.zdb_id: 209104-5
    detail.hit.zdb_id: 1461794-8
    SSG: 11
    SSG: 12
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  • 7
    Online Resource
    Online Resource
    Deletion of the de novo DNA methyltransferase Dnmt3a promotes lung tumor progression
    Proceedings of the National Academy of Sciences ; 2011
    In:  Proceedings of the National Academy of Sciences Vol. 108, No. 44 ( 2011-11), p. 18061-18066
    Details
    In: Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 108, No. 44 ( 2011-11), p. 18061-18066
    Abstract: Alterations in DNA methylation have been associated with genome-wide hypomethylation and regional de novo methylation in numerous cancers. De novo methylation is mediated by the de novo methyltransferases Dnmt3a and 3b, but only Dnmt3b has been implicated in promoting cancer by silencing of tumor-suppressor genes. In this study, we have analyzed the role of Dnmt3a in lung cancer by using a conditional mouse tumor model. We show that Dnmt3a deficiency significantly promotes tumor growth and progression but not initiation. Changes in gene expression show that Dnmt3a deficiency affects key steps in cancer progression, such as angiogenesis, cell adhesion, and cell motion, consistent with accelerated and more malignant growth. Our results suggest that Dnmt3a may act like a tumor-suppressor gene in lung tumor progression and may be a critical determinant of lung cancer malignancy.
    Type of Medium: Online Resource
    ISSN: 0027-8424 , 1091-6490
    URL: Article
    DOI: 10.1073/pnas.1114946108
    RVK:
    TA 1000
    RVK:
    WA 15000
    Language: English
    Publisher: Proceedings of the National Academy of Sciences
    Publication Date: 2011
    detail.hit.zdb_id: 209104-5
    detail.hit.zdb_id: 1461794-8
    SSG: 11
    SSG: 12
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    Online Resource
  • 8
    Online Resource
    Online Resource
    Differentiation and virus expression in BALB/Mo mice: endogenous Moloney leukemia virus is not activated in hematopoietic cells.
    Proceedings of the National Academy of Sciences ; 1982
    In:  Proceedings of the National Academy of Sciences Vol. 79, No. 6 ( 1982-03), p. 1874-1878
    Details
    In: Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 79, No. 6 ( 1982-03), p. 1874-1878
    Abstract: The endogenous Moloney leukemia virus (M-MuLV) in the BALB/Mo substrain of mice is activated during the first week after birth. Virus replication occurs in cells of the lymphatic system. Lymphoid cells therefore represent the target cells for virus replication and leukemic transformation. To investigate whether virus activation occurs during lymphoid cell differentiation, hematopoietic stem cells carrying the endogenous Mov-1 genome were transplanted to sublethally irradiated BALB/c mice. Effective colonization of the recipients was demonstrated by Southern DNA hybridization. No activation of the endogenous Mov-1 genome occurred during a 4-month observation period after the transplantation. Thus the first step in development of disease in BALB/Mo mice involves activation of the Mov-1 locus in a nonhematopoietic cell followed by superinfection of lymphatic cells and subsequent virus replication and virus spread.
    Type of Medium: Online Resource
    ISSN: 0027-8424 , 1091-6490
    URL: Article
    DOI: 10.1073/pnas.79.6.1874
    RVK:
    TA 1000
    RVK:
    WA 15000
    Language: English
    Publisher: Proceedings of the National Academy of Sciences
    Publication Date: 1982
    detail.hit.zdb_id: 209104-5
    detail.hit.zdb_id: 1461794-8
    SSG: 11
    SSG: 12
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  • 9
    Online Resource
    Online Resource
    Reprogramming of murine and human somatic cells using a single polycistronic vector
    Proceedings of the National Academy of Sciences ; 2009
    In:  Proceedings of the National Academy of Sciences Vol. 106, No. 1 ( 2009-01-06), p. 157-162
    Details
    In: Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 106, No. 1 ( 2009-01-06), p. 157-162
    Abstract: Directed reprogramming of somatic cells by defined factors provides a novel method for the generation of patient-specific stem cells with the potential to bypass both the practical and ethical concerns associated with somatic cell nuclear transfer (SCNT) and human embryonic stem (hES) cells. Although the generation of induced pluripotent stem (iPS) cells has proven a robust technology in mouse and human, a major impediment to the use of iPS cells for therapeutic purposes has been the viral-based delivery of the reprogramming factors because multiple proviral integrations pose the danger of insertional mutagenesis. Here we report a novel approach to reduce the number of viruses necessary to reprogram somatic cells by delivering reprogramming factors in a single virus using 2A “self-cleaving” peptides, which support efficient polycistronic expression from a single promoter. We find that up to four reprogramming factors (Oct4, Sox2, Klf4, and c-Myc) can be expressed from a single virus to generate iPS cells in both embryonic and adult somatic mouse cells and we show that a single proviral copy is sufficient to generate iPS cells from mouse embryonic fibroblasts. In addition we have generated human induced pluripotent stem (hiPS) cell lines from human keratinocytes, demonstrating that a single polycistronic virus can reprogram human somatic cells.
    Type of Medium: Online Resource
    ISSN: 0027-8424 , 1091-6490
    URL: Article
    DOI: 10.1073/pnas.0811426106
    RVK:
    TA 1000
    RVK:
    WA 15000
    Language: English
    Publisher: Proceedings of the National Academy of Sciences
    Publication Date: 2009
    detail.hit.zdb_id: 209104-5
    detail.hit.zdb_id: 1461794-8
    SSG: 11
    SSG: 12
    Location Call Number Limitation Availability
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