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  • Proceedings of the National Academy of Sciences  (45)
  • Biology  (45)
  • 1
    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
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    WA 15000
    Language: English
    Publisher: Proceedings of the National Academy of Sciences
    Publication Date: 2019
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  • 2
    Online Resource
    Online Resource
    Expression of MeCP2 in postmitotic neurons rescues Rett syndrome in mice
    Proceedings of the National Academy of Sciences ; 2004
    In:  Proceedings of the National Academy of Sciences Vol. 101, No. 16 ( 2004-04-20), p. 6033-6038
    Details
    In: Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 101, No. 16 ( 2004-04-20), p. 6033-6038
    Abstract: Mutations in MECP2 are the cause of Rett syndrome (RTT) in humans, a neurodevelopmental disorder that affects mainly girls. MeCP2 is a protein that binds CpG dinucleotides and is thought to act as a global transcriptional repressor. It is highly expressed in neurons, but not in glia, of the postnatal brain. The timing of MeCP2 activation correlates with the maturation of the central nervous system, and recent reports suggest that MeCP2 may be involved in the formation of synaptic contacts and may function in activity-dependent neuronal gene expression. Deletion or targeted mutation of Mecp2 in mice leads to a Rett-like phenotype. Selective mutation of Mecp2 in postnatal neurons leads to a similar, although delayed, phenotype, suggesting that MeCP2 plays a role in postmitotic neurons. Here we test the hypothesis that the symptoms of RTT are exclusively caused by a neuronal MeCP2 deficiency by placing Mecp2 expression under the control of a neuron-specific promoter. Expression of the Mecp2 transgene in postmitotic neurons resulted in symptoms of severe motor dysfunction. Transgene expression in Mecp2 mutant mice, however, rescued the RTT phenotype.
    Type of Medium: Online Resource
    ISSN: 0027-8424 , 1091-6490
    URL: Article
    DOI: 10.1073/pnas.0401626101
    RVK:
    TA 1000
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    WA 15000
    Language: English
    Publisher: Proceedings of the National Academy of Sciences
    Publication Date: 2004
    detail.hit.zdb_id: 209104-5
    detail.hit.zdb_id: 1461794-8
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  • 3
    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
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    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
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  • 4
    Online Resource
    Online Resource
    Reprogramming of murine fibroblasts to induced pluripotent stem cells with chemical complementation of Klf4
    Proceedings of the National Academy of Sciences ; 2009
    In:  Proceedings of the National Academy of Sciences Vol. 106, No. 22 ( 2009-06-02), p. 8912-8917
    Details
    In: Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 106, No. 22 ( 2009-06-02), p. 8912-8917
    Abstract: Ectopic expression of defined transcription factors can reprogram somatic cells to induced pluripotent stem (iPS) cells, but the utility of iPS cells is hampered by the use of viral delivery systems. Small molecules offer an alternative to replace virally transduced transcription factors with chemical signaling cues responsible for reprogramming. In this report we describe a small-molecule screening platform applied to identify compounds that functionally replace the reprogramming factor Klf4. A series of small-molecule scaffolds were identified that activate Nanog expression in mouse fibroblasts transduced with a subset of reprogramming factors lacking Klf4. Application of one such molecule, kenpaullone, in lieu of Klf4 gave rise to iPS cells that are indistinguishable from murine embryonic stem cells. This experimental platform can be used to screen large chemical libraries in search of novel compounds to replace the reprogramming factors that induce pluripotency. Ultimately, such compounds may provide mechanistic insight into the reprogramming process.
    Type of Medium: Online Resource
    ISSN: 0027-8424 , 1091-6490
    URL: Article
    DOI: 10.1073/pnas.0903860106
    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
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  • 5
    Online Resource
    Online Resource
    ES cells derived from cloned and fertilized blastocysts are transcriptionally and functionally indistinguishable
    Proceedings of the National Academy of Sciences ; 2006
    In:  Proceedings of the National Academy of Sciences Vol. 103, No. 4 ( 2006-01-24), p. 933-938
    Details
    In: Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 103, No. 4 ( 2006-01-24), p. 933-938
    Abstract: Reproductive cloning is uniformly rejected as a valid technology in humans because of the severely abnormal phenotypes seen in cloned animals. Gene expression aberrations observed in tissues of cloned animals have also raised concerns regarding the therapeutic application of “customized” embryonic stem (ES) cells derived by nuclear transplantation (NT) from a patient's somatic cells. Although previous experiments in mice have demonstrated that the developmental potential of ES cells derived from cloned blastocysts (NT-ES cells) is identical to that of ES cells derived from fertilized blastocysts, a systematic molecular characterization of NT-ES cell lines is lacking. To investigate whether transcriptional aberrations, similar to those observed in tissues of cloned mice, also occur in NT-ES cells, we have compared transcriptional profiles of 10 mouse NT- and fertilization-derived-ES cell lines. We report here that the ES cell lines derived from cloned and fertilized mouse blastocysts are indistinguishable based on their transcriptional profiles, consistent with their normal developmental potential. Our results indicate that, in contrast to embryonic and fetal development of clones, the process of NT-ES cell derivation rigorously selects for those immortal cells that have erased the “epigenetic memory” of the donor nucleus and, thus, become functionally equivalent. Our findings support the notion that ES cell lines derived from cloned or fertilized blastocysts have an identical therapeutic potential.
    Type of Medium: Online Resource
    ISSN: 0027-8424 , 1091-6490
    URL: Article
    DOI: 10.1073/pnas.0510485103
    RVK:
    TA 1000
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    WA 15000
    Language: English
    Publisher: Proceedings of the National Academy of Sciences
    Publication Date: 2006
    detail.hit.zdb_id: 209104-5
    detail.hit.zdb_id: 1461794-8
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  • 6
    Online Resource
    Online Resource
    T-cell receptor-driven lymphomagenesis in mice derived from a reprogrammed T cell
    Proceedings of the National Academy of Sciences ; 2010
    In:  Proceedings of the National Academy of Sciences Vol. 107, No. 44 ( 2010-11-02), p. 18939-18943
    Details
    In: Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 107, No. 44 ( 2010-11-02), p. 18939-18943
    Abstract: The conversion of mature somatic cells into pluripotent stem cells, both by nuclear transfer and transduction with specific “reprogramming” genes, represents a major advance in regenerative medicine. Pluripotent stem cell lines can now be generated from an individual's own cells, facilitating the generation of immunologically acceptable stem cell-based therapeutics. Many cell types can undergo nuclear reprogramming, leading to the question of whether the identity of the reprogrammed cell of origin has a biological consequence. Peripheral blood, containing a mixture of T, B, NK, and myeloid cell types, represents one potential source of reprogrammable cells. In this study, we describe the unique case of mice derived from a reprogrammed T cell. These mice have prerearranged T-cell receptor (TCR) genes in all cells. Surprisingly, ≈50% of mice with prerearranged TCR genes develop spontaneous T cell lymphomas, which originate in the thymus. The lymphomas arise from developing T cells, and contain activated Notch1, similar to most human and mouse T-cell acute lymphoblastic lymphomas. Furthermore, lymphomagenesis requires the expression of both prerearranged TCRα and TCRβ genes, indicating a critical role for TCR signaling. Furthermore, inhibitors of multiple branches of TCR signaling suppress lymphoma growth, implicating TCR signaling as an essential component in lymphoma proliferation. The lymphomagenesis in mice derived from a reprogrammed T cell demonstrates the deleterious consequences of misregulation of the TCR rearrangement and signaling pathways and illustrates one case of cellular reprogramming where the identity of the cell of origin has profound consequences.
    Type of Medium: Online Resource
    ISSN: 0027-8424 , 1091-6490
    URL: Article
    DOI: 10.1073/pnas.1013230107
    RVK:
    TA 1000
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    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
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  • 7
    Online Resource
    Online Resource
    Chromatin proteomic profiling reveals novel proteins associated with histone-marked genomic regions
    Proceedings of the National Academy of Sciences ; 2015
    In:  Proceedings of the National Academy of Sciences Vol. 112, No. 12 ( 2015-03-24), p. 3841-3846
    Details
    In: Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 112, No. 12 ( 2015-03-24), p. 3841-3846
    Abstract: More than a thousand proteins are thought to contribute to mammalian chromatin and its regulation, but our understanding of the genomic occupancy and function of most of these proteins is limited. Here we describe an approach, which we call “chromatin proteomic profiling,” to identify proteins associated with genomic regions marked by specifically modified histones. We used ChIP-MS to identify proteins associated with genomic regions marked by histones modified at specific lysine residues, including H3K27ac, H3K4me3, H3K79me2, H3K36me3, H3K9me3, and H4K20me3, in ES cells. We identified 332 known and 114 novel proteins associated with these histone-marked genomic segments. Many of the novel candidates have been implicated in various diseases, and their chromatin association may provide clues to disease mechanisms. More than 100 histone modifications have been described, so similar chromatin proteomic profiling studies should prove to be valuable for identifying many additional chromatin-associated proteins in a broad spectrum of cell types.
    Type of Medium: Online Resource
    ISSN: 0027-8424 , 1091-6490
    URL: Article
    DOI: 10.1073/pnas.1502971112
    RVK:
    TA 1000
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    WA 15000
    Language: English
    Publisher: Proceedings of the National Academy of Sciences
    Publication Date: 2015
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    detail.hit.zdb_id: 1461794-8
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  • 8
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    Online Resource
    Human neural crest cells contribute to coat pigmentation in interspecies chimeras after in utero injection into mouse embryos
    Proceedings of the National Academy of Sciences ; 2016
    In:  Proceedings of the National Academy of Sciences Vol. 113, No. 6 ( 2016-02-09), p. 1570-1575
    Details
    In: Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 113, No. 6 ( 2016-02-09), p. 1570-1575
    Abstract: The neural crest (NC) represents multipotent cells that arise at the interphase between ectoderm and prospective epidermis of the neurulating embryo. The NC has major clinical relevance because it is involved in both inherited and acquired developmental abnormalities. The aim of this study was to establish an experimental platform that would allow for the integration of human NC cells (hNCCs) into the gastrulating mouse embryo. NCCs were derived from pluripotent mouse, rat, and human cells and microinjected into embryonic-day-8.5 embryos. To facilitate integration of the NCCs, we used recipient embryos that carried a c -Kit mutation ( W sh /W sh ), which leads to a loss of melanoblasts and thus eliminates competition from the endogenous host cells. The donor NCCs migrated along the dorsolateral migration routes in the recipient embryos. Postnatal mice derived from injected embryos displayed pigmented hair, demonstrating differentiation of the NCCs into functional melanocytes. Although the contribution of human cells to pigmentation in the host was lower than that of mouse or rat donor cells, our results indicate that hNCCs, injected in utero , can integrate into the embryo and form mature functional cells in the animal. This mouse–human chimeric platform allows for a new approach to study NC development and diseases.
    Type of Medium: Online Resource
    ISSN: 0027-8424 , 1091-6490
    URL: Article
    DOI: 10.1073/pnas.1525518113
    RVK:
    TA 1000
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    WA 15000
    Language: English
    Publisher: Proceedings of the National Academy of Sciences
    Publication Date: 2016
    detail.hit.zdb_id: 209104-5
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  • 9
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    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
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    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
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  • 10
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    Online Resource
    Vascular tumors in livers with targeted inactivation of the von Hippel–Lindau tumor suppressor
    Proceedings of the National Academy of Sciences ; 2001
    In:  Proceedings of the National Academy of Sciences Vol. 98, No. 4 ( 2001-02-13), p. 1583-1588
    Details
    In: Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 98, No. 4 ( 2001-02-13), p. 1583-1588
    Abstract: von Hippel–Lindau (VHL) disease is a pleomorphic familial tumor syndrome that is characterized by the development of highly vascularized tumors. Homozygous disruption of the VHL gene in mice results in embryonic lethality. To investigate VHL function in the adult we have generated a conditional VHL null allele (2- lox allele) and null allele (1- lox allele) by Cre-mediated recombination in embryonic stem cells. We show here that mice heterozygous for the 1- lox allele develop cavernous hemangiomas of the liver, a rare manifestation of the human disease. Histologically these tumors were associated with hepatocellular steatosis and focal proliferations of small vessels. To study the cellular origin of these lesions we inactivated VHL tissue-specifically in hepatocytes. Deletion of VHL in the liver resulted in severe steatosis, many blood-filled vascular cavities, and foci of increased vascularization within the hepatic parenchyma. These histopathological changes were similar to those seen in livers from mice heterozygous for the 1- lox allele. Hypoxia-inducible mRNAs encoding vascular endothelial growth factor, glucose transporter 1, and erythropoietin were up-regulated. We thus provide evidence that targeted inactivation of mouse VHL can model clinical features of the human disease and underline the importance of the VHL gene product in the regulation of hypoxia-responsive genes in vivo .
    Type of Medium: Online Resource
    ISSN: 0027-8424 , 1091-6490
    URL: Article
    DOI: 10.1073/pnas.98.4.1583
    RVK:
    TA 1000
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    WA 15000
    Language: English
    Publisher: Proceedings of the National Academy of Sciences
    Publication Date: 2001
    detail.hit.zdb_id: 209104-5
    detail.hit.zdb_id: 1461794-8
    SSG: 11
    SSG: 12
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