Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 13 de 13
Filtrar
1.
Hum Mol Genet ; 29(R2): R248-R254, 2020 10 20.
Artigo em Inglês | MEDLINE | ID: mdl-32821941

RESUMO

Changes of polarity in somatic stem cells upon aging or disease lead to a functional deterioration of stem cells and consequently loss of tissue homeostasis, likely due to changes in the mode (symmetry versus asymmetry) of stem cell divisions. Changes in polarity of epigenetic markers (or 'epi-polarity') in stem cells, which are linked to alterations in chromatin architecture, might explain how a decline in the frequency of epipolar stem cells can have a long-lasting impact on the function of especially aging stem cells. The drift in epipolarity might represent a novel therapeutic target to improve stem cell function upon aging or disease. Here we review basic biological principles of epigenetic polarity, with a special focus on epipolarity and aging of hematopoietic stem cells.


Assuntos
Envelhecimento , Polaridade Celular , Cromatina/genética , Metilação de DNA , Epigênese Genética , Células-Tronco Hematopoéticas/patologia , Homeostase , Humanos
2.
Haematologica ; 105(1): 22-37, 2020 01.
Artigo em Inglês | MEDLINE | ID: mdl-31806687

RESUMO

Hematopoietic stem cells (HSC) sustain blood production over the entire life-span of an organism. It is of extreme importance that these cells maintain self-renewal and differentiation potential over time in order to preserve homeostasis of the hematopoietic system. Many of the intrinsic aspects of HSC are affected by the aging process resulting in a deterioration in their potential, independently of their microenvironment. Here we review recent findings characterizing most of the intrinsic aspects of aged HSC, ranging from phenotypic to molecular alterations. Historically, DNA damage was thought to be the main cause of HSC aging. However, over recent years, many new findings have defined an increasing number of biological processes that intrinsically change with age in HSC. Epigenetics and chromatin architecture, together with autophagy, proteostasis and metabolic changes, and how they are interconnected, are acquiring growing importance for understanding the intrinsic aging of stem cells. Given the increase in populations of older subjects worldwide, and considering that aging is the primary risk factor for most diseases, understanding HSC aging becomes particularly relevant also in the context of hematologic disorders, such as myelodysplastic syndromes and acute myeloid leukemia. Research on intrinsic mechanisms responsible for HSC aging is providing, and will continue to provide, new potential molecular targets to possibly ameliorate or delay aging of the hematopoietic system and consequently improve the outcome of hematologic disorders in the elderly. The niche-dependent contributions to hematopoietic aging are discussed in another review in this same issue of the Journal.


Assuntos
Senescência Celular , Células-Tronco Hematopoéticas , Idoso , Envelhecimento , Diferenciação Celular , Homeostase , Humanos
3.
PLoS Genet ; 11(9): e1005517, 2015 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-26368543

RESUMO

Phosphorylation of histone H2AX by ATM and ATR establishes a chromatin recruitment platform for DNA damage response proteins. Phospho-H2AX (γH2AX) has been most intensively studied in the context of DNA double-strand breaks caused by exogenous clastogens, but recent studies suggest that DNA replication stress also triggers formation of γH2A (ortholog of γH2AX) in Schizosaccharomyces pombe. Here, a focused genetic screen in fission yeast reveals that γH2A is critical when there are defects in Replication Factor C (RFC), which loads proliferating cell nuclear antigen (PCNA) clamp onto duplex DNA. Surprisingly Chk1, Cds1/Chk2 and the Rad9-Hus1-Rad1 checkpoint clamp, which are crucial for surviving many genotoxins, are fully dispensable in RFC-defective cells. Immunoblot analysis confirms that Rad9-Hus1-Rad1 is not required for formation of γH2A by Rad3/ATR in S-phase. Defects in DNA polymerase epsilon, which binds PCNA in the replisome, also create an acute need for γH2A. These requirements for γH2A were traced to its role in docking with Brc1, which is a 6-BRCT-domain protein that is structurally related to budding yeast Rtt107 and mammalian PTIP. Brc1, which localizes at stalled replication forks by binding γH2A, prevents aberrant formation of Replication Protein A (RPA) foci in RFC-impaired cells, suggesting that Brc1-coated chromatin stabilizes replisomes when PCNA or DNA polymerase availability limits DNA synthesis.


Assuntos
Histonas/metabolismo , Fase S , Schizosaccharomyces/metabolismo , DNA Polimerase II/genética , DNA Polimerase II/metabolismo , DNA Fúngico/metabolismo , Mutação , Antígeno Nuclear de Célula em Proliferação/metabolismo , Ligação Proteica , Schizosaccharomyces/citologia , Schizosaccharomyces/genética , Proteínas de Schizosaccharomyces pombe/genética , Proteínas de Schizosaccharomyces pombe/metabolismo
4.
Biochim Biophys Acta ; 1859(10): 1314-21, 2016 10.
Artigo em Inglês | MEDLINE | ID: mdl-27345571

RESUMO

It is well established that eukaryotic genomes are pervasively transcribed producing cryptic unstable transcripts (CUTs). However, the mechanisms regulating pervasive transcription are not well understood. Here, we report that the fission yeast CENP-B homolog Abp1 plays an important role in preventing pervasive transcription. We show that loss of abp1 results in the accumulation of CUTs, which are targeted for degradation by the exosome pathway. These CUTs originate from different types of genomic features, but the highest increase corresponds to Tf2 retrotransposons and rDNA repeats, where they map along the entire elements. In the absence of abp1, increased RNAPII-Ser5P occupancy is observed throughout the Tf2 coding region and, unexpectedly, RNAPII-Ser5P is enriched at rDNA repeats. Loss of abp1 also results in Tf2 derepression and increased nucleolus size. Altogether these results suggest that Abp1 prevents pervasive RNAPII transcription of repetitive DNA elements (i.e., Tf2 and rDNA repeats) from internal cryptic sites.


Assuntos
Proteínas de Ligação a DNA/genética , Regulação Fúngica da Expressão Gênica , RNA Polimerase II/genética , Proteínas de Schizosaccharomyces pombe/genética , Schizosaccharomyces/genética , Transcrição Gênica , Nucléolo Celular/genética , Nucléolo Celular/metabolismo , Nucléolo Celular/ultraestrutura , Centrômero/metabolismo , Centrômero/ultraestrutura , Proteína B de Centrômero/genética , Proteína B de Centrômero/metabolismo , DNA Ribossômico/genética , DNA Ribossômico/metabolismo , Proteínas de Ligação a DNA/deficiência , Heterocromatina/metabolismo , Heterocromatina/ultraestrutura , RNA Polimerase II/metabolismo , Estabilidade de RNA , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Retroelementos , Schizosaccharomyces/metabolismo , Schizosaccharomyces/ultraestrutura , Proteínas de Schizosaccharomyces pombe/metabolismo
5.
J Biol Chem ; 290(9): 5661-72, 2015 Feb 27.
Artigo em Inglês | MEDLINE | ID: mdl-25555917

RESUMO

Gene- and cell-based therapies are promising strategies for the treatment of degenerative retinal diseases such as age-related macular degeneration, Stargardt disease, and retinitis pigmentosa. Cellular engineering before transplantation may allow the delivery of cellular factors that can promote functional improvements, such as increased engraftment or survival of transplanted cells. A current challenge in traditional DNA-based vector transfection is to find a delivery system that is both safe and efficient, but using mRNA as an alternative to DNA can circumvent these major roadblocks. In this study, we show that both unmodified and modified mRNA can be delivered to retinal pigmented epithelial (RPE) cells with a high efficiency compared with conventional plasmid delivery systems. On the other hand, administration of unmodified mRNA induced a strong innate immune response that was almost absent when using modified mRNA. Importantly, transfection of mRNA encoding a key regulator of RPE gene expression, microphthalmia-associated transcription factor (MITF), confirmed the functionality of the delivered mRNA. Immunostaining showed that transfection with either type of mRNA led to the expression of roughly equal levels of MITF, primarily localized in the nucleus. Despite these findings, quantitative RT-PCR analyses showed that the activation of the expression of MITF target genes was higher following transfection with modified mRNA compared with unmodified mRNA. Our findings, therefore, show that modified mRNA transfection can be applied to human embryonic stem cell-derived RPE cells and that the method is safe, efficient, and functional.


Assuntos
Células-Tronco Embrionárias/metabolismo , Células Epiteliais/metabolismo , Expressão Gênica , RNA Mensageiro/genética , Transfecção/métodos , Transporte Ativo do Núcleo Celular , Western Blotting , Diferenciação Celular/genética , Linhagem Celular , Núcleo Celular/metabolismo , Células-Tronco Embrionárias/citologia , Células Epiteliais/ultraestrutura , Células HEK293 , Humanos , Fator Regulador 3 de Interferon/genética , Fator Regulador 3 de Interferon/metabolismo , Fator de Transcrição Associado à Microftalmia/genética , Fator de Transcrição Associado à Microftalmia/metabolismo , Microscopia Confocal , Microscopia Eletrônica de Transmissão , Fatores de Transcrição Otx/genética , Fatores de Transcrição Otx/metabolismo , RNA Mensageiro/metabolismo , Epitélio Pigmentado da Retina/citologia , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Fator de Transcrição RelA/genética , Fator de Transcrição RelA/metabolismo , cis-trans-Isomerases/genética , cis-trans-Isomerases/metabolismo
6.
Zygote ; 24(6): 839-847, 2016 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-27702419

RESUMO

While vitrification has become the method of choice for preservation of human oocytes and embryos, cryopreservation of complex tissues and of large yolk-containing cells, remains largely unsuccessful. One critical step in such instances is appropriate permeation while avoiding potentially toxic concentrations of cryoprotectants. Permeation of water and small non-charged solutes, such as those used as cryoprotectants, occurs largely through membrane channel proteins termed aquaporins (AQPs). Substitution of a Thr by an Ala residue in the pore-forming motif of the zebrafish (Dario rerio) Aqp3b paralog resulted in a mutant (DrAqp3b-T85A) that when expressed in Xenopus or porcine oocytes increased their permeability to ethylene glycol at pH 7.5 and 8.5. The main objective of this study was to test whether ectopic expression of DrAqp3b-T85A also conferred higher resistance to cryoinjury. For this, DrAqp3b-T85A + eGFP (reporter) cRNA, or eGFP cRNA alone, was microinjected into in vivo fertilized 1-cell mouse zygotes. Following culture to the 2-cell stage, appropriate membrane expression of DrAqp3b-T85A was confirmed by immunofluorescence microscopy using a primary specific antibody directed against the C-terminus of DrAqp3b. Microinjected 2-cell embryos were then cryopreserved using a fast-freezing rate and low concentration (1.5 M) of ethylene glycol in order to highlight any benefits from DrAqp3b-T85A expression. Notably, post-thaw survival rates were higher (P<0.05) for T85A-eGFP-injected than for -uninjected or eGFP-injected embryos (73±7.3 vs. 28±7.3 or 14±6.7, respectively). We propose that ectopic expression of mutant AQPs may provide an avenue to improve cryopreservation results of large cells and tissues in which current vitrification protocols yield low survival.


Assuntos
Aquaporina 3/genética , Criopreservação/métodos , Crioprotetores/farmacologia , Proteínas de Peixe-Zebra/genética , Zigoto/fisiologia , Substituição de Aminoácidos , Animais , Animais Geneticamente Modificados , Aquaporina 3/metabolismo , Blastômeros , Etilenoglicol/farmacologia , Feminino , Proteínas de Fluorescência Verde/genética , Proteínas de Fluorescência Verde/metabolismo , Concentração de Íons de Hidrogênio , Masculino , Camundongos Endogâmicos , Mutação , Oócitos/fisiologia , Sus scrofa , Proteínas de Peixe-Zebra/metabolismo
7.
PLoS Genet ; 7(9): e1002271, 2011 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-21931565

RESUMO

The multifunctional Mre11-Rad50-Nbs1 (MRN) protein complex recruits ATM/Tel1 checkpoint kinase and CtIP/Ctp1 homologous recombination (HR) repair factor to double-strand breaks (DSBs). HR repair commences with the 5'-to-3' resection of DNA ends, generating 3' single-strand DNA (ssDNA) overhangs that bind Replication Protein A (RPA) complex, followed by Rad51 recombinase. In Saccharomyces cerevisiae, the Mre11-Rad50-Xrs2 (MRX) complex is critical for DSB resection, although the enigmatic ssDNA endonuclease activity of Mre11 and the DNA-end processing factor Sae2 (CtIP/Ctp1 ortholog) are largely unnecessary unless the resection activities of Exo1 and Sgs1-Dna2 are also eliminated. Mre11 nuclease activity and Ctp1/CtIP are essential for DSB repair in Schizosaccharomyces pombe and mammals. To investigate DNA end resection in Schizo. pombe, we adapted an assay that directly measures ssDNA formation at a defined DSB. We found that Mre11 and Ctp1 are essential for the efficient initiation of resection, consistent with their equally crucial roles in DSB repair. Exo1 is largely responsible for extended resection up to 3.1 kb from a DSB, with an activity dependent on Rqh1 (Sgs1) DNA helicase having a minor role. Despite its critical function in DSB repair, Mre11 nuclease activity is not required for resection in fission yeast. However, Mre11 nuclease and Ctp1 are required to disassociate the MRN complex and the Ku70-Ku80 nonhomologous end-joining (NHEJ) complex from DSBs, which is required for efficient RPA localization. Eliminating Ku makes Mre11 nuclease activity dispensable for MRN disassociation and RPA localization, while improving repair of a one-ended DSB formed by replication fork collapse. From these data we propose that release of the MRN complex and Ku from DNA ends by Mre11 nuclease activity and Ctp1 is a critical step required to expose ssDNA for RPA localization and ensuing HR repair.


Assuntos
Proteínas Cromossômicas não Histona/genética , Reparo do DNA por Junção de Extremidades/genética , Proteínas de Ligação a DNA/genética , Proteínas de Schizosaccharomyces pombe/genética , Schizosaccharomyces/genética , Quebras de DNA de Cadeia Dupla , DNA Helicases/genética , Reparo do DNA/genética , DNA de Cadeia Simples/genética , Exodesoxirribonucleases/genética , Recombinação Homóloga/genética , Complexos Multiproteicos/genética , Rad51 Recombinase/genética , Proteína de Replicação A/genética , Schizosaccharomyces/metabolismo
8.
PLoS Genet ; 6(7): e1001032, 2010 Jul 22.
Artigo em Inglês | MEDLINE | ID: mdl-20661445

RESUMO

Schizosaccharomyces pombe Rad3 checkpoint kinase and its human ortholog ATR are essential for maintaining genome integrity in cells treated with genotoxins that damage DNA or arrest replication forks. Rad3 and ATR also function during unperturbed growth, although the events triggering their activation and their critical functions are largely unknown. Here, we use ChIP-on-chip analysis to map genomic loci decorated by phosphorylated histone H2A (gammaH2A), a Rad3 substrate that establishes a chromatin-based recruitment platform for Crb2 and Brc1 DNA repair/checkpoint proteins. Unexpectedly, gammaH2A marks a diverse array of genomic features during S-phase, including natural replication fork barriers and a fork breakage site, retrotransposons, heterochromatin in the centromeres and telomeres, and ribosomal RNA (rDNA) repeats. gammaH2A formation at the centromeres and telomeres is associated with heterochromatin establishment by Clr4 histone methyltransferase. We show that gammaH2A domains recruit Brc1, a factor involved in repair of damaged replication forks. Brc1 C-terminal BRCT domain binding to gammaH2A is crucial in the absence of Rqh1(Sgs1), a RecQ DNA helicase required for rDNA maintenance whose human homologs are mutated in patients with Werner, Bloom, and Rothmund-Thomson syndromes that are characterized by cancer-predisposition or accelerated aging. We conclude that Rad3 phosphorylates histone H2A to mobilize Brc1 to critical genomic domains during S-phase, and this pathway functions in parallel with Rqh1 DNA helicase in maintaining genome integrity.


Assuntos
Proteínas de Ciclo Celular/fisiologia , Cromossomos Fúngicos/metabolismo , Instabilidade Genômica , Histonas/metabolismo , Proteínas Quinases/fisiologia , Fase S , Proteínas de Schizosaccharomyces pombe/fisiologia , Schizosaccharomyces/genética , Proteínas de Ciclo Celular/genética , Proteínas de Ciclo Celular/metabolismo , Quinase do Ponto de Checagem 2 , DNA Helicases , Fosforilação , Proteínas Quinases/genética , Proteínas Quinases/metabolismo , Proteínas de Schizosaccharomyces pombe/genética , Proteínas de Schizosaccharomyces pombe/metabolismo
9.
NPJ Regen Med ; 7(1): 78, 2022 Dec 29.
Artigo em Inglês | MEDLINE | ID: mdl-36581635

RESUMO

One goal of regenerative medicine is to rejuvenate tissues and extend lifespan by restoring the function of endogenous aged stem cells. However, evidence that somatic stem cells can be targeted in vivo to extend lifespan is still lacking. Here, we demonstrate that after a short systemic treatment with a specific inhibitor of the small RhoGTPase Cdc42 (CASIN), transplanting aged hematopoietic stem cells (HSCs) from treated mice is sufficient to extend the healthspan and lifespan of aged immunocompromised mice without additional treatment. In detail, we show that systemic CASIN treatment improves strength and endurance of aged mice by increasing the myogenic regenerative potential of aged skeletal muscle stem cells. Further, we show that CASIN modifies niche localization and H4K16ac polarity of HSCs in vivo. Single-cell profiling reveals changes in HSC transcriptome, which underlie enhanced lymphoid and regenerative capacity in serial transplantation assays. Overall, we provide proof-of-concept evidence that a short systemic treatment to decrease Cdc42 activity improves the regenerative capacity of different endogenous aged stem cells in vivo, and that rejuvenated HSCs exert a broad systemic effect sufficient to extend murine health- and lifespan.

10.
Stem Cell Reports ; 13(3): 515-529, 2019 09 10.
Artigo em Inglês | MEDLINE | ID: mdl-31402335

RESUMO

In vertebrates, GATA2 is a master regulator of hematopoiesis and is expressed throughout embryo development and in adult life. Although the essential role of GATA2 in mouse hematopoiesis is well established, its involvement during early human hematopoietic development is not clear. By combining time-controlled overexpression of GATA2 with genetic knockout experiments, we found that GATA2, at the mesoderm specification stage, promotes the generation of hemogenic endothelial progenitors and their further differentiation to hematopoietic progenitor cells, and negatively regulates cardiac differentiation. Surprisingly, genome-wide transcriptional and chromatin immunoprecipitation analysis showed that GATA2 bound to regulatory regions, and repressed the expression of cardiac development-related genes. Moreover, genes important for hematopoietic differentiation were upregulated by GATA2 in a mostly indirect manner. Collectively, our data reveal a hitherto unrecognized role of GATA2 as a repressor of cardiac fates, and highlight the importance of coordinating the specification and repression of alternative cell fates.


Assuntos
Fator de Transcrição GATA2/metabolismo , Hematopoese , Mesoderma/metabolismo , Diferenciação Celular , Fator de Transcrição GATA2/genética , Regulação da Expressão Gênica , Hemangioblastos/citologia , Hemangioblastos/metabolismo , Humanos , Células-Tronco Pluripotentes Induzidas/citologia , Células-Tronco Pluripotentes Induzidas/metabolismo , Mesoderma/citologia , Miócitos Cardíacos/citologia , Miócitos Cardíacos/metabolismo , Ligação Proteica , Análise de Célula Única
11.
Mol Cell Biol ; 25(19): 8755-61, 2005 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-16166653

RESUMO

Schizosaccharomyces pombe rRNA genes contain three replication fork barriers (RFB1-3) located in the nontranscribed spacer. RFB2 and RFB3 require binding of the transcription terminator factor Reb1p to two identical recognition sequences that colocalize with these barriers. RFB1, which is the strongest of the three barriers, functions in a Reb1p-independent manner, and cognate DNA-binding proteins for this barrier have not been identified yet. Here we functionally define RFB1 within a 78-bp sequence located near the 3' end of the rRNA coding region. A protein that specifically binds to this sequence was purified by affinity chromatography and identified as Sap1p by mass spectrometry. Specific binding to RFB1 was confirmed by using Sap1p expressed in Escherichia coli. Sap1p is essential for viability and is required for efficient mating-type switching. Mutations in RFB1 that precluded formation of the Sap1p-RFB1 complex systematically abolished replication barrier function, indicating that Sap1p is required for replication fork blockage at RFB1.


Assuntos
Proteínas de Ligação a DNA/fisiologia , Genes Fúngicos , RNA Ribossômico/química , Proteínas de Schizosaccharomyces pombe/fisiologia , Schizosaccharomyces/genética , Schizosaccharomyces/fisiologia , Sequência de Bases , Sítios de Ligação , Cromatografia de Afinidade , DNA/química , Replicação do DNA , Proteínas de Ligação a DNA/química , Proteínas de Ligação a DNA/metabolismo , Eletroforese em Gel Bidimensional , Escherichia coli/metabolismo , Espectrometria de Massas , Modelos Genéticos , Dados de Sequência Molecular , Mutação , Oligonucleotídeos/química , Plasmídeos/metabolismo , Reação em Cadeia da Polimerase , Ligação Proteica , RNA Ribossômico/genética , Proteínas de Schizosaccharomyces pombe/química , Proteínas de Schizosaccharomyces pombe/metabolismo , Fatores de Transcrição
12.
Cell Stem Cell ; 21(4): 431-447, 2017 10 05.
Artigo em Inglês | MEDLINE | ID: mdl-28985525

RESUMO

Determining causal relationships between distinct chromatin features and gene expression, and ultimately cell behavior, remains a major challenge. Recent developments in targetable epigenome-editing tools enable us to assign direct transcriptional and functional consequences to locus-specific chromatin modifications. This Protocol Review discusses the unprecedented opportunity that CRISPR/Cas9 technology offers for investigating and manipulating the epigenome to facilitate further understanding of stem cell biology and engineering of stem cells for therapeutic applications. We also provide technical considerations for standardization and further improvement of the CRISPR/Cas9-based tools to engineer the epigenome.


Assuntos
Sistemas CRISPR-Cas/genética , Epigênese Genética , Genoma , Animais , Cromatina/metabolismo , Humanos , Medicina Regenerativa , Células-Tronco/metabolismo
13.
Cell Rep ; 17(3): 671-683, 2016 10 11.
Artigo em Inglês | MEDLINE | ID: mdl-27732845

RESUMO

Current sources of platelets for transfusion are insufficient and associated with risk of alloimmunization and blood-borne infection. These limitations could be addressed by the generation of autologous megakaryocytes (MKs) derived in vitro from somatic cells with the ability to engraft and differentiate in vivo. Here, we show that overexpression of a defined set of six transcription factors efficiently converts mouse and human fibroblasts into MK-like progenitors. The transdifferentiated cells are CD41+, display polylobulated nuclei, have ploidies higher than 4N, form MK colonies, and give rise to platelets in vitro. Moreover, transplantation of MK-like murine progenitor cells into NSG mice results in successful engraftment and further maturation in vivo. Similar results are obtained using disease-corrected fibroblasts from Fanconi anemia patients. Our results combined demonstrate that functional MK progenitors with clinical potential can be obtained in vitro, circumventing the use of hematopoietic progenitors or pluripotent stem cells.


Assuntos
Diferenciação Celular , Fibroblastos/citologia , Células Progenitoras de Megacariócitos/citologia , Animais , Transdiferenciação Celular , Subunidade alfa 2 de Fator de Ligação ao Core/metabolismo , Anemia de Fanconi/patologia , Fibroblastos/metabolismo , Fator de Transcrição GATA2/metabolismo , Humanos , Células Progenitoras de Megacariócitos/transplante , Camundongos
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA