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Stem Cells
Addressing the ethical issues raised by synthetic human entities with embryo-like features
May 12, 2017   ELife
Aach J, Lunshof J, Iyer E, Church GM
Addressing the ethical issues raised by synthetic human entities with embryo-like features
May 12, 2017
ELife
The "14-day rule" for embryo research stipulates that experiments with intact human embryos must not allow them to develop beyond 14 days or the appearance of the primitive streak. However, recent experiments showing that suitably cultured human pluripotent stem cells can self-organize and recapitulate embryonic features have highlighted difficulties with the 14-day rule and led to calls for its reassessment. Here we argue that these and related experiments raise more foundational issues that cannot be fixed by adjusting the 14-day rule, because the framework underlying the rule cannot adequately describe the ways by which synthetic human entities with embryo-like features (SHEEFs) might develop morally concerning features through altered forms of development. We propose that limits on research with SHEEFs be based as directly as possible on the generation of such features, and recommend that the research and bioethics communities lead a wide-ranging inquiry aimed at mapping out solutions to the ethical problems raised by them.
Accreditation of Biosafe Clinical-Grade Human Embryonic Stem Cells According to Chinese Regulations
May 16, 2017   Stem Cell Reports
Gu Q, Wang J, Wang L, Liu ZX, Zhu WW,   . . . . . .   , Li W, Zhao XY, Hu BY, Hao J, Zhou Q
Accreditation of Biosafe Clinical-Grade Human Embryonic Stem Cells According to Chinese Regulations
May 16, 2017
Stem Cell Reports
Human embryonic stem cells (hESCs) are promising in regenerative medicine. Although several hESC-based clinical trials are under way, a widely accepted standard of clinical-grade cells remains obscure. To attain a completely xeno-free clinical-grade cell line, the system must be free of xenogenic components, the cells must have a comprehensive set of functions, and good manufacturing practice conditions must be used. In this study, following these criteria, we successfully derived two hESC lines, which were thereby considered "clinical-grade embryonic stem cells". In addition to the primary capacity for pluripotency, these two cell lines were efficiently differentiated into various types of clinical-grade progeny. Importantly, the cells were recognized by the National Institutes for Food and Drug Control of China for further eligible accreditation. These data indicate that we have established completely xeno-free clinical-grade hESC lines and their derivatives, which will be valuable for the foundation of an international standard for clinical-grade cells for therapy. Copyright © 2017 The Authors. Published by Elsevier Inc. All rights reserved.
On the slope of the regression between stem cell divisions and cancer risk, and the lack of correlation between stem cell divisions and environmental factors-associated cancer risk
May 18, 2017   PloS One
Tomasetti C, Vogelstein B
Blood: Education for stem cells
May 17, 2017   Nature Add nature.com free-link Cancel
Guibentif C, Göttgens B
PD-1 expression by tumour-associated macrophages inhibits phagocytosis and tumour immunity
May 17, 2017   Nature Add nature.com free-link Cancel
Gordon SR, Maute RL, Dulken BW, Hutter G, George BM, McCracken MN, Gupta R, Tsai JM, Sinha R, Corey D, Ring AM, Connolly AJ, Weissman IL
PD-1 expression by tumour-associated macrophages inhibits phagocytosis and tumour immunity
May 17, 2017
Nature
Programmed cell death protein 1 (PD-1) is an immune checkpoint receptor that is upregulated on activated T cells for the induction of immune tolerance. Tumour cells frequently overexpress the ligand for PD-1, programmed cell death ligand 1 (PD-L1), facilitating their escape from the immune system. Monoclonal antibodies that block the interaction between PD-1 and PD-L1, by binding to either the ligand or receptor, have shown notable clinical efficacy in patients with a variety of cancers, including melanoma, colorectal cancer, non-small-cell lung cancer and Hodgkin's lymphoma. Although it is well established that PD-1-PD-L1 blockade activates T cells, little is known about the role that this pathway may have in tumour-associated macrophages (TAMs). Here we show that both mouse and human TAMs express PD-1. TAM PD-1 expression increases over time in mouse models of cancer and with increasing disease stage in primary human cancers. TAM PD-1 expression correlates negatively with phagocytic potency against tumour cells, and blockade of PD-1-PD-L1 in vivo increases macrophage phagocytosis, reduces tumour growth and lengthens the survival of mice in mouse models of cancer in a macrophage-dependent fashion. This suggests that PD-1-PD-L1 therapies may also function through a direct effect on macrophages, with substantial implications for the treatment of cancer with these agents.
Haematopoietic stem and progenitor cells from human pluripotent stem cells
May 17, 2017   Nature Add nature.com free-link Cancel
Sugimura R, Jha DK, Han A, Soria-Valles C, da Rocha EL,   . . . . . .   , Keller G, Engelman AN, Snapper SB, Doulatov S, Daley GQ
Haematopoietic stem and progenitor cells from human pluripotent stem cells
May 17, 2017
Nature
A variety of tissue lineages can be differentiated from pluripotent stem cells by mimicking embryonic development through stepwise exposure to morphogens, or by conversion of one differentiated cell type into another by enforced expression of master transcription factors. Here, to yield functional human haematopoietic stem cells, we perform morphogen-directed differentiation of human pluripotent stem cells into haemogenic endothelium followed by screening of 26 candidate haematopoietic stem-cell-specifying transcription factors for their capacity to promote multi-lineage haematopoietic engraftment in mouse hosts. We recover seven transcription factors (ERG, HOXA5, HOXA9, HOXA10, LCOR, RUNX1 and SPI1) that are sufficient to convert haemogenic endothelium into haematopoietic stem and progenitor cells that engraft myeloid, B and T cells in primary and secondary mouse recipients. Our combined approach of morphogen-driven differentiation and transcription-factor-mediated cell fate conversion produces haematopoietic stem and progenitor cells from pluripotent stem cells and holds promise for modelling haematopoietic disease in humanized mice and for therapeutic strategies in genetic blood disorders.
Conversion of adult endothelium to immunocompetent haematopoietic stem cells
May 17, 2017   Nature Add nature.com free-link Cancel
Lis R, Karrasch CC, Poulos MG, Kunar B, Redmond D,   . . . . . .   , Elemento O, Speck NA, Butler JM, Scandura JM, Rafii S
Conversion of adult endothelium to immunocompetent haematopoietic stem cells
May 17, 2017
Nature
Developmental pathways that orchestrate the fleeting transition of endothelial cells into haematopoietic stem cells remain undefined. Here we demonstrate a tractable approach for fully reprogramming adult mouse endothelial cells to haematopoietic stem cells (rEC-HSCs) through transient expression of the transcription-factor-encoding genes Fosb, Gfi1, Runx1, and Spi1 (collectively denoted hereafter as FGRS) and vascular-niche-derived angiocrine factors. The induction phase (days 0-8) of conversion is initiated by expression of FGRS in mature endothelial cells, which results in endogenous Runx1 expression. During the specification phase (days 8-20), RUNX1+ FGRS-transduced endothelial cells commit to a haematopoietic fate, yielding rEC-HSCs that no longer require FGRS expression. The vascular niche drives a robust self-renewal and expansion phase of rEC-HSCs (days 20-28). rEC-HSCs have a transcriptome and long-term self-renewal capacity similar to those of adult haematopoietic stem cells, and can be used for clonal engraftment and serial primary and secondary multi-lineage reconstitution, including antigen-dependent adaptive immune function. Inhibition of TGFβ and CXCR7 or activation of BMP and CXCR4 signalling enhanced generation of rEC-HSCs. Pluripotency-independent conversion of endothelial cells into autologous authentic engraftable haematopoietic stem cells could aid treatment of haematological disorders.
KDM1A/LSD1 regulates the differentiation and maintenance of spermatogonia in mice
May 12, 2017   PloS One
Myrick DA, Christopher MA, Scott AM, Simon AK, Donlin-Asp PG, Kelly WG, Katz DJ
KDM1A/LSD1 regulates the differentiation and maintenance of spermatogonia in mice
May 12, 2017
PloS One
The proper regulation of spermatogenesis is crucial to ensure the continued production of sperm and fertility. Here, we investigated the function of the H3K4me2 demethylase KDM1A/LSD1 during spermatogenesis in developing and adult mice. Conditional deletion of Kdm1a in the testis just prior to birth leads to fewer spermatogonia and germ cell loss before 3 weeks of age. These results demonstrate that KDM1A is required for spermatogonial differentiation, as well as germ cell survival, in the developing testis. In addition, inducible deletion of Kdm1a in the adult testis results in the abnormal accumulation of meiotic spermatocytes, as well as apoptosis and progressive germ cell loss. These results demonstrate that KDM1A is also required during adult spermatogenesis. Furthermore, without KDM1A, the stem cell factor OCT4 is ectopically maintained in differentiating germ cells. This requirement for KDM1A is similar to what has been observed in other stem cell populations, suggesting a common function. Taken together, we propose that KDM1A is a key regulator of spermatogenesis and germ cell maintenance in the mouse.
Discovery of microRNAs during early spermatogenesis in chicken
May 22, 2017   PloS One
Xu L, Guo Q, Chang G, Qiu L, Liu X, Bi Y, Zhang Y, Wang H, Lu W, Ren L, Chen Y, Zhang Y, Xu Q, Chen G
Discovery of microRNAs during early spermatogenesis in chicken
May 22, 2017
PloS One
Spermatogenesis is a complex process that involves many elements. However, until now, little is known at the molecular level about spermatogenesis in poultry. Here we investigated microRNAs and their target genes that may be involved in germ cell development and spermatogonial in chicken. We used next-generation sequencing to analyze miRNA expression profiles in three types of germline cells: primordial germ cells (PGCs), spermatogonial stem cells (SSCs), and spermatogonia (Sp) during early stage of spermatogenesis. After validated the candidate miRNAs and corresponding genes' expression in three types of cells, we found 15 miRNAs that were enriched 21 target genes that may be involved in spermatogenesis. Among the enriched miRNAs, miR-202-5p/3p were up-regulated in the Sp library and down-regulated in the PGCs library. Through RT-qPCR and Dual-Luciferase reporter assay, we confirmed that miR-202-5p bind to LIMK2 and involved in germ cell development. Collectively, we firstly discover the novel miRNAs, like miR-202-5p, and its related genes and pathways, expressed during the early spermatogonial stage in chicken, which will provide new clues for deciphering the molecular mechanism of the miRNAs regulating germline stem cell differentiation and spermatogenesis in chicken.
Extracellular matrix nitration alters growth factor release and activates bioactive complement in human retinal pigment epithelial cells
May 15, 2017   PloS One
Fields MA, Bowrey HE, Gong J, Moreira EF, Cai H, Del Priore LV
Extracellular matrix nitration alters growth factor release and activates bioactive complement in human retinal pigment epithelial cells
May 15, 2017
PloS One
We have shown previously that non-enzymatic nitration (NEN) of the extracellular matrix (ECM), which serves as a model of Bruch's membrane (BM) aging, has a profound effect on the behavior of the overlying retinal pigment epithelial (RPE) cells, including altered phagocytic ability, reduced cell adhesion, and inhibition of proliferation. We know that transplanted RPE monolayers will encounter a hostile sub-RPE environment, including age-related alterations in BM that may compromise cell function and survival. Here we use our previous NEN model of BM aging to determine the effects of NEN of the ECM on growth factor release and complement activation in RPE cells. Human induced-pluripotent stem cells (iPSCs) were differentiated into RPE cells, and confirmed by immunohistochemistry, confocal microscopy, and polymerase chain reaction. IPSC-derived RPE cells were plated onto RPE-derived ECM under untreated or nitrite-modified conditions. Cells were cultured for 7 days and barrier function measured by transepithelial resistance (TER). Vascular endothelial growth factor (VEGF), pigment epithelium-derived factor (PEDF), and complement component C3a were measured using enzyme-linked immunosorbent assay (ELISA). On average nitrite-modified ECM increased VEGF release both apically and basally by 0.15 ± 0.014 ng/mL (p
Human decellularized bone scaffolds from aged donors show improved osteoinductive capacity compared to young donor bone
May 15, 2017   PloS One
Smith CA, Board TN, Rooney P, Eagle MJ, Richardson SM, Hoyland JA
Human decellularized bone scaffolds from aged donors show improved osteoinductive capacity compared to young donor bone
May 15, 2017
PloS One
To improve the safe use of allograft bone, decellularization techniques may be utilized to produce acellular scaffolds. Such scaffolds should retain their innate biological and biomechanical capacity and support mesenchymal stem cell (MSC) osteogenic differentiation. However, as allograft bone is derived from a wide age-range, this study aimed to determine whether donor age impacts on the ability an osteoinductive, acellular scaffold produced from human bone to promote the osteogenic differentiation of bone marrow MSCs (BM-MSC). BM-MSCs from young and old donors were seeded on acellular bone cubes from young and old donors undergoing osteoarthritis related hip surgery. All combinations resulted in increased osteogenic gene expression, and alkaline phosphatase (ALP) enzyme activity, however BM-MSCs cultured on old donor bone displayed the largest increases. BM-MSCs cultured in old donor bone conditioned media also displayed higher osteogenic gene expression and ALP activity than those exposed to young donor bone conditioned media. ELISA and Luminex analysis of conditioned media demonstrated similar levels of bioactive factors between age groups; however, IGF binding protein 1 (IGFBP1) concentration was significantly higher in young donor samples. Additionally, structural analysis of old donor bone indicated an increased porosity compared to young donor bone. These results demonstrate the ability of a decellularized scaffold produced from young and old donors to support osteogenic differentiation of cells from young and old donors. Significantly, the older donor bone produced greater osteogenic differentiation which may be related to reduced IGFBP1 bioavailability and increased porosity, potentially explaining the excellent clinical results seen with the use of allograft from aged donors.
Role of NF-E2 related factor 2 (Nrf2) on chemotherapy resistance in acute myeloid leukemia (AML) and the effect of pharmacological inhibition of Nrf2
May 15, 2017   PloS One
Karathedath S, Rajamani BM, Musheer Aalam SM, Abraham A, Varatharajan S, Krishnamurthy P, Mathews V, Velayudhan SR, Balasubramanian P
Role of NF-E2 related factor 2 (Nrf2) on chemotherapy resistance in acute myeloid leukemia (AML) and the effect of pharmacological inhibition of Nrf2
May 15, 2017
PloS One
Cytarabine (Ara-C) and Daunorubicin (Dnr) forms the backbone of acute myeloid leukemia (AML) therapy. Drug resistance and toxic side effects pose a major threat to treatment success and hence alternate less toxic therapies are warranted. NF-E2 related factor-2 (Nrf2), a master regulator of antioxidant response is implicated in chemoresistance in solid tumors. However, little is known about the role of Nrf2 in AML chemoresistance and the effect of pharmacological inhibitor brusatol in modulating this resistance. Primary AML samples with high ex-vivo IC50 to Ara-C, ATO, Dnr had significantly high NRF2 RNA expression. Gene-specific knockdown of NRF2 improved sensitivity to these drugs in resistant AML cell lines by decreasing the expression of downstream antioxidant targets of Nrf2 by compromising the cell's ability to scavenge the ROS. Treatment with brusatol, a pharmacological inhibitor of Nrf2, improved sensitivity to Ara-C, ATO, and Dnr and reduced colony formation capacity. AML cell lines stably overexpressing NRF2 showed increased resistance to ATO, Dnr and Ara-C and increased expression of downstream targets. This study demonstrates that Nrf2 could be an ideal druggable target in AML, more so to the drugs that function through ROS, suggesting the possibility of using Nrf2 inhibitors in combination with chemotherapeutic agents to modulate drug resistance in AML.
Infectious disease ward admission positively influences P. jiroveci pneumonia (PjP) outcome: A retrospective analysis of 116 HIV-positive and HIV-negative immunocompromised patients
May 15, 2017   PloS One
Ricciardi A, Gentilotti E, Coppola L, Maffongelli G, Cerva C,   . . . . . .   , Toschi N, Di Cave D, Parisi SG, Andreoni M, Sarmati L
Infectious disease ward admission positively influences P. jiroveci pneumonia (PjP) outcome: A retrospective analysis of 116 HIV-positive and HIV-negative immunocompromised patients
May 15, 2017
PloS One
P. jiroveci (Pj) causes a potentially fatal pneumonia in immunocompromised patients and the factors associated with a bad outcome are poorly understood. A retrospective analysis on Pj pneumonia (PjP) cases occurring in Tor Vergata University Hospital, Italy, during the period 2011-2015. The patients' demographic, clinical and radiological characteristics and the Pj genotypes were considered. The study population included 116 patients, 37.9% of whom had haematological malignancy or underwent haematological stem cell transplantation (HSCT), 22.4% had HIV infection, 16.4% had chronic lung diseases (CLD), 7.8% had a solid cancer, and 3.4% underwent a solid organ transplant (SOT). The remaining 12.1% had a miscellaneous other condition. At univariate analysis, being older than 60 years was significantly correlated with a severe PjP (OR [95%CI] 2.52 [0.10-5.76]; p = 0.031) and death (OR [95%CI] 2.44 [1.05-5.70]; p = 0.036), while a previous trimethoprim/sulfamethoxazole (TMP/SMX) prophylaxis were significantly associated with a less severe pneumonia (OR[95%CI] 0.35 [0.15-0.84], p = 0.023); moreover, death due to PjP was significantly more frequent in patients with CLD (OR[95%CI] 3.26 [1.17-9.05]; p = 0.019) while, admission to the Infectious Diseases Unit was significantly associated with fewer deaths (OR[95%CI] 0.10 [0.03-0.36], p = 0.002). At multivariate analysis, a better PjP outcome was observed in patients taking TMP/SMX prophylaxis and that were admitted to the Infectious Diseases Unit (OR[95%CI] 0.27 [0.07-1.03], p = 0.055, OR[95%CI] 0.16 [0.05-0.55]; p = 0.004, respectively). In conclusion, in our study population, TMP/SMX prophylaxis and infectious disease specialist approach were variables correlated with a better PjP outcome.
The mitochondrial respiratory chain is essential for haematopoietic stem cell function
May 15, 2017   Nature Cell Biology Add nature.com free-link Cancel
Ansó E, Weinberg SE, Diebold LP, Thompson BJ, Malinge S, Schumacker PT, Liu X, Zhang Y, Shao Z, Steadman M, Marsh KM, Xu J, Crispino JD, Chandel NS
The mitochondrial respiratory chain is essential for haematopoietic stem cell function
May 15, 2017
Nature Cell Biology
Adult and fetal haematopoietic stem cells (HSCs) display a glycolytic phenotype, which is required for maintenance of stemness; however, whether mitochondrial respiration is required to maintain HSC function is not known. Here we report that loss of the mitochondrial complex III subunit Rieske iron-sulfur protein (RISP) in fetal mouse HSCs allows them to proliferate but impairs their differentiation, resulting in anaemia and prenatal death. RISP-null fetal HSCs displayed impaired respiration resulting in a decreased NAD+/NADH ratio. RISP-null fetal HSCs and progenitors exhibited an increase in both DNA and histone methylation associated with increases in 2-hydroxyglutarate (2HG), a metabolite known to inhibit DNA and histone demethylases. RISP inactivation in adult HSCs also impaired respiration resulting in loss of quiescence concomitant with severe pancytopenia and lethality. Thus, respiration is dispensable for adult or fetal HSC proliferation, but essential for fetal HSC differentiation and maintenance of adult HSC quiescence.
Lineage-specific functions of TET1 in the postimplantation mouse embryo
May 15, 2017   Nature Genetics Add nature.com free-link Cancel
Khoueiry R, Sohni A, Thienpont B, Luo X, Velde JV, Bartoccetti M, Boeckx B, Zwijsen A, Rao A, Lambrechts D, Koh KP
Lineage-specific functions of TET1 in the postimplantation mouse embryo
May 15, 2017
Nature Genetics
The mammalian TET enzymes catalyze DNA demethylation. While they have been intensely studied as major epigenetic regulators, little is known about their physiological roles and the extent of functional redundancy following embryo implantation. Here we define non-redundant roles for TET1 at an early postimplantation stage of the mouse embryo, when its paralogs Tet2 and Tet3 are not detectably expressed. TET1 regulates numerous genes defining differentiation programs in the epiblast and extraembryonic ectoderm. In epiblast cells, TET1 demethylates gene promoters via hydroxymethylation and maintains telomere stability. Surprisingly, TET1 represses a majority of epiblast target genes independently of methylation changes, in part through regulation of the gene encoding the transcriptional repressor JMJD8. Dysregulated gene expression in the absence of TET1 causes embryonic defects, which are partially penetrant in an inbred strain but fully lethal in non-inbred mice. Collectively, our study highlights an interplay between the catalytic and non-catalytic activities of TET1 that is essential for normal development.
Notch ligands regulate the muscle stem-like state ex vivo but are not sufficient for retaining regenerative capacity
May 12, 2017   PloS One
Sakai H, Fukuda S, Nakamura M, Uezumi A, Noguchi YT, Sato T, Morita M, Yamada H, Tsuchida K, Tajbakhsh S, Fukada SI
Notch ligands regulate the muscle stem-like state ex vivo but are not sufficient for retaining regenerative capacity
May 12, 2017
PloS One
Myogenic stem cells are a promising avenue for the treatment of muscular disorders. Freshly isolated muscle stem cells have a remarkable engraftment ability in vivo, but their cell number is limited. Current conventional culture conditions do not allow muscle stem cells to expand in vitro with their bona fide engraftment efficiency, requiring the improvement of culture procedures for achieving successful cell-therapy for muscle disorders. Here we expanded mouse muscle stem cells and human myoblasts with Notch ligands, DLL1, DLL4, and JAG1 to activate Notch signaling in vitro and to investigate whether these cells could retain their engraftment efficiency. Notch signaling promotes the expansion of Pax7+MyoD- mouse muscle stem-like cells and inhibits differentiation even after passage in vitro. Treatment with Notch ligands induced the Notch target genes and generated PAX7+MYOD- stem-like cells from human myoblasts previously cultured on conventional culture plates. However, cells treated with Notch ligands exhibit a stem cell-like state in culture, yet their regenerative ability was less than that of freshly isolated cells in vivo and was comparable to that of the control. These unexpected findings suggest that artificial maintenance of Notch signaling alone is insufficient for improving regenerative capacity of mouse and human donor-muscle cells and suggest that combinatorial events are critical to achieve muscle stem cell and myoblast engraftment potential.
Plastic roles of pericytes in the blood-retinal barrier
May 16, 2017   Nature Communications
Park DY, Lee J, Kim J, Kim K, Hong S, Han S, Kubota Y, Augustin HG, Ding L, Kim JW, Kim H, He Y, Adams RH, Koh GY
Plastic roles of pericytes in the blood-retinal barrier
May 16, 2017
Nature Communications
The blood-retinal barrier (BRB) consists of tightly interconnected capillary endothelial cells covered with pericytes and glia, but the role of the pericytes in BRB regulation is not fully understood. Here, we show that platelet-derived growth factor (PDGF)-B/PDGF receptor beta (PDGFRβ) signalling is critical in formation and maturation of BRB through active recruitment of pericytes onto growing retinal vessels. Impaired pericyte recruitment to the vessels shows multiple vascular hallmarks of diabetic retinopathy (DR) due to BRB disruption. However, PDGF-B/PDGFRβ signalling is expendable for maintaining BRB integrity in adult mice. Although selective pericyte loss in stable adult retinal vessels surprisingly does not cause BRB disintegration, it sensitizes retinal vascular endothelial cells (ECs) to VEGF-A, leading to upregulation of angiopoietin-2 (Ang2) in ECs through FOXO1 activation and triggering a positive feedback that resembles the pathogenesis of DR. Accordingly, either blocking Ang2 or activating Tie2 greatly attenuates BRB breakdown, suggesting potential therapeutic approaches to reduce retinal damages upon DR progression.
Joint morphogenetic cells in the adult mammalian synovium
May 16, 2017   Nature Communications
Roelofs AJ, Zupan J, Riemen AHK, Kania K, Ansboro S, White N, Clark SM, De Bari C
Joint morphogenetic cells in the adult mammalian synovium
May 16, 2017
Nature Communications
The stem cells that safeguard synovial joints in adulthood are undefined. Studies on mesenchymal stromal/stem cells (MSCs) have mainly focused on bone marrow. Here we show that lineage tracing of Gdf5-expressing joint interzone cells identifies in adult mouse synovium an MSC population largely negative for the skeletal stem cell markers Nestin-GFP, Leptin receptor and Gremlin1. Following cartilage injury, Gdf5-lineage cells underpin synovial hyperplasia through proliferation, are recruited to a Nestin-GFPhigh perivascular population, and contribute to cartilage repair. The transcriptional co-factor Yap is upregulated after injury, and its conditional ablation in Gdf5-lineage cells prevents synovial lining hyperplasia and decreases contribution of Gdf5-lineage cells to cartilage repair. Cultured Gdf5-lineage cells exhibit progenitor activity for stable chondrocytes and are able to self-organize three-dimensionally to form a synovial lining-like layer. Finally, human synovial MSCs transduced with Bmp7 display morphogenetic properties by patterning a joint-like organ in vivo. Our findings further the understanding of the skeletal stem/progenitor cells in adult life.
Temporal dynamics of gene expression and histone marks at the Arabidopsis shoot meristem during flowering
May 17, 2017   Nature Communications
You Y, Sawikowska A, Neumann M, Posé D, Capovilla G, Langenecker T, Neher RA, Krajewski P, Schmid M
Temporal dynamics of gene expression and histone marks at the Arabidopsis shoot meristem during flowering
May 17, 2017
Nature Communications
Plants can produce organs throughout their entire life from pluripotent stem cells located at their growing tip, the shoot apical meristem (SAM). At the time of flowering, the SAM of Arabidopsis thaliana switches fate and starts producing flowers instead of leaves. Correct timing of flowering in part determines reproductive success, and is therefore under environmental and endogenous control. How epigenetic regulation contributes to the floral transition has eluded analysis so far, mostly because of the poor accessibility of the SAM. Here we report the temporal dynamics of the chromatin modifications H3K4me3 and H3K27me3 and their correlation with transcriptional changes at the SAM in response to photoperiod-induced flowering. Emphasizing the importance of tissue-specific epigenomic analyses we detect enrichments of chromatin states in the SAM that were not apparent in whole seedlings. Furthermore, our results suggest that regulation of translation might be involved in adjusting meristem function during the induction of flowering.
Ccl2/Ccr2 signalling recruits a distinct fetal microchimeric population that rescues delayed maternal wound healing
May 18, 2017   Nature Communications
Castela M, Nassar D, Sbeih M, Jachiet M, Wang Z, Aractingi S
Ccl2/Ccr2 signalling recruits a distinct fetal microchimeric population that rescues delayed maternal wound healing
May 18, 2017
Nature Communications
Foetal microchimeric cells (FMCs) traffic into maternal circulation during pregnancy and persist for decades after delivery. Upon maternal injury, FMCs migrate to affected sites where they participate in tissue healing. However, the specific signals regulating the trafficking of FMCs to injury sites had to be identified. Here we report that, in mice, a subset of FMCs implicated in tissue repair displays CD11b+ CD34+ CD31+ phenotype and highly express C-C chemokine receptor 2 (Ccr2). The Ccr2 ligand chemokine ligand 2 (Ccl2) enhances the recruitment of FMCs to maternal wounds where these cells transdifferentiate into endothelial cells and stimulate angiogenesis through Cxcl1 secretion. Ccl2 administration improves delayed maternal wound healing in pregnant and postpartum mice but never in virgin ones. This role of Ccl2/Ccr2 signalling opens new strategies for tissue repair through natural stem cell therapy, a concept that can be later applied to other types of maternal diseases.
ASXL2 is essential for haematopoiesis and acts as a haploinsufficient tumour suppressor in leukemia
May 18, 2017   Nature Communications
Micol JB, Pastore A, Inoue D, Duployez N, Kim E,   . . . . . .   , Koche R, Solary E, Sinha A, Preudhomme C, Abdel-Wahab O
ASXL2 is essential for haematopoiesis and acts as a haploinsufficient tumour suppressor in leukemia
May 18, 2017
Nature Communications
Additional sex combs-like (ASXL) proteins are mammalian homologues of additional sex combs (Asx), a regulator of trithorax and polycomb function in Drosophila. While there has been great interest in ASXL1 due to its frequent mutation in leukemia, little is known about its paralog ASXL2, which is frequently mutated in acute myeloid leukemia patients bearing the RUNX1-RUNX1T1 (AML1-ETO) fusion. Here we report that ASXL2 is required for normal haematopoiesis with distinct, non-overlapping effects from ASXL1 and acts as a haploinsufficient tumour suppressor. While Asxl2 was required for normal haematopoietic stem cell self-renewal, Asxl2 loss promoted AML1-ETO leukemogenesis. Moreover, ASXL2 target genes strongly overlapped with those of RUNX1 and AML1-ETO and ASXL2 loss was associated with increased chromatin accessibility at putative enhancers of key leukemogenic loci. These data reveal that Asxl2 is a critical regulator of haematopoiesis and mediates transcriptional effects that promote leukemogenesis driven by AML1-ETO.
Concerted regulation of retinal pigment epithelium basement membrane and barrier function by angiocrine factors
May 19, 2017   Nature Communications
Benedicto I, Lehmann GL, Ginsberg M, Nolan DJ, Bareja R,   . . . . . .   , Rabbany SY, Maminishkis A, Miller SS, Rafii S, Rodriguez-Boulan E
Concerted regulation of retinal pigment epithelium basement membrane and barrier function by angiocrine factors
May 19, 2017
Nature Communications
The outer blood-retina barrier is established through the coordinated terminal maturation of the retinal pigment epithelium (RPE), fenestrated choroid endothelial cells (ECs) and Bruch's membrane, a highly organized basement membrane that lies between both cell types. Here we study the contribution of choroid ECs to this process by comparing their gene expression profile before (P5) and after (P30) the critical postnatal period when mice acquire mature visual function. Transcriptome analyses show that expression of extracellular matrix-related genes changes dramatically over this period. Co-culture experiments support the existence of a novel regulatory pathway: ECs secrete factors that remodel RPE basement membrane, and integrin receptors sense these changes triggering Rho GTPase signals that modulate RPE tight junctions and enhance RPE barrier function. We anticipate our results will spawn a search for additional roles of choroid ECs in RPE physiology and disease.
Hit and go CAS9 delivered through a lentiviral based self-limiting circuit
May 22, 2017   Nature Communications
Petris G, Casini A, Montagna C, Lorenzin F, Prandi D, Romanel A, Zasso J, Conti L, Demichelis F, Cereseto A
Hit and go CAS9 delivered through a lentiviral based self-limiting circuit
May 22, 2017
Nature Communications
In vivo application of the CRISPR-Cas9 technology is still limited by unwanted Cas9 genomic cleavages. Long-term expression of Cas9 increases the number of genomic loci non-specifically cleaved by the nuclease. Here we develop a Self-Limiting Cas9 circuit for Enhanced Safety and specificity (SLiCES) which consists of an expression unit for Streptococcus pyogenes Cas9 (SpCas9), a self-targeting sgRNA and a second sgRNA targeting a chosen genomic locus. The self-limiting circuit results in increased genome editing specificity by controlling Cas9 levels. For its in vivo utilization, we next integrate SLiCES into a lentiviral delivery system (lentiSLiCES) via circuit inhibition to achieve viral particle production. Upon delivery into target cells, the lentiSLiCES circuit switches on to edit the intended genomic locus while simultaneously stepping up its own neutralization through SpCas9 inactivation. By preserving target cells from residual nuclease activity, our hit and go system increases safety margins for genome editing.
Notch-mediated conversion of activated T cells into stem cell memory-like T cells for adoptive immunotherapy
May 22, 2017   Nature Communications
Kondo T, Morita R, Okuzono Y, Nakatsukasa H, Sekiya T, Chikuma S, Shichita T, Kanamori M, Kubo M, Koga K, Miyazaki T, Kassai Y, Yoshimura A
Notch-mediated conversion of activated T cells into stem cell memory-like T cells for adoptive immunotherapy
May 22, 2017
Nature Communications
Adoptive T-cell immunotherapy is a promising approach to cancer therapy. Stem cell memory T (TSCM) cells have been proposed as a class of long-lived and highly proliferative memory T cells. CD8+ TSCM cells can be generated in vitro from naive CD8+ T cells via Wnt signalling; however, methods do not yet exist for inducing TSCM cells from activated or memory T cells. Here, we show a strategy for generating TSCM-like cells in vitro (iTSCM cells) from activated CD4+ and CD8+ T cells in mice and humans by coculturing with stromal cells that express a Notch ligand. iTSCM cells lose PD-1 and CTLA-4 expression, and produce a large number of tumour-specific effector cells after restimulation. This method could therefore be used to generate antigen-specific effector T cells for adoptive immunotherapy.
YAP/TAZ link cell mechanics to Notch signalling to control epidermal stem cell fate
May 17, 2017   Nature Communications
Totaro A, Castellan M, Battilana G, Zanconato F, Azzolin L, Giulitti S, Cordenonsi M, Piccolo S
YAP/TAZ link cell mechanics to Notch signalling to control epidermal stem cell fate
May 17, 2017
Nature Communications
How the behaviour of somatic stem cells (SCs) is influenced by mechanical signals remains a black-box in cell biology. Here we show that YAP/TAZ regulation by cell shape and rigidity of the extracellular matrix (ECM) dictates a pivotal SC decision: to remain undifferentiated and grow, or to activate a terminal differentiation programme. Notably, mechano-activation of YAP/TAZ promotes epidermal stemness by inhibition of Notch signalling, a key factor for epidermal differentiation. Conversely, YAP/TAZ inhibition by low mechanical forces induces Notch signalling and loss of SC traits. As such, mechano-dependent regulation of YAP/TAZ reflects into mechano-dependent regulation of Notch signalling. Mechanistically, at least in part, this is mediated by YAP/TAZ binding to distant enhancers activating the expression of Delta-like ligands, serving as 'in cis' inhibitors of Notch. Thus YAP/TAZ mechanotransduction integrates with cell-cell communication pathways for fine-grained orchestration of SC decisions.

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