Showing papers on "Cellular differentiation published in 2014"
TL;DR: Monocle is described, an unsupervised algorithm that increases the temporal resolution of transcriptome dynamics using single-cell RNA-Seq data collected at multiple time points that revealed switch-like changes in expression of key regulatory factors, sequential waves of gene regulation, and expression of regulators that were not known to act in differentiation.
Abstract: Defining the transcriptional dynamics of a temporal process such as cell differentiation is challenging owing to the high variability in gene expression between individual cells. Time-series gene expression analyses of bulk cells have difficulty distinguishing early and late phases of a transcriptional cascade or identifying rare subpopulations of cells, and single-cell proteomic methods rely on a priori knowledge of key distinguishing markers. Here we describe Monocle, an unsupervised algorithm that increases the temporal resolution of transcriptome dynamics using single-cell RNA-Seq data collected at multiple time points. Applied to the differentiation of primary human myoblasts, Monocle revealed switch-like changes in expression of key regulatory factors, sequential waves of gene regulation, and expression of regulators that were not known to act in differentiation. We validated some of these predicted regulators in a loss-of function screen. Monocle can in principle be used to recover single-cell gene expression kinetics from a wide array of cellular processes, including differentiation, proliferation and oncogenic transformation.
4,119 citations
TL;DR: There has been dramatic advances in this young field, but there is much to be learned about Tfh cell biology in the interest of applying that knowledge to biomedical needs.
1,397 citations
TL;DR: It is shown that senescent fibroblasts and endothelial cells appear very early in response to a cutaneous wound, where they accelerate wound closure by inducing myofibroblast differentiation through the secretion of platelet-derived growth factor AA (PDGF-AA).
1,288 citations
TL;DR: The results confirmed the basic outlines of the classical model of epithelial cell-type diversity in the distal lung and led to the discovery of many previously unknown cell- type markers, including transcriptional regulators that discriminate between the different populations.
Abstract: The mammalian lung is a highly branched network in which the distal regions of the bronchial tree transform during development into a densely packed honeycomb of alveolar air sacs that mediate gas exchange. Although this transformation has been studied by marker expression analysis and fate-mapping, the mechanisms that control the progression of lung progenitors along distinct lineages into mature alveolar cell types are still incompletely known, in part because of the limited number of lineage markers and the effects of ensemble averaging in conventional transcriptome analysis experiments on cell populations. Here we show that single-cell transcriptome analysis circumvents these problems and enables direct measurement of the various cell types and hierarchies in the developing lung. We used microfluidic single-cell RNA sequencing (RNA-seq) on 198 individual cells at four different stages encompassing alveolar differentiation to measure the transcriptional states which define the developmental and cellular hierarchy of the distal mouse lung epithelium. We empirically classified cells into distinct groups by using an unbiased genome-wide approach that did not require a priori knowledge of the underlying cell types or the previous purification of cell populations. The results confirmed the basic outlines of the classical model of epithelial cell-type diversity in the distal lung and led to the discovery of many previously unknown cell-type markers, including transcriptional regulators that discriminate between the different populations. We reconstructed the molecular steps during maturation of bipotential progenitors along both alveolar lineages and elucidated the full life cycle of the alveolar type 2 cell lineage. This single-cell genomics approach is applicable to any developing or mature tissue to robustly delineate molecularly distinct cell types, define progenitors and lineage hierarchies, and identify lineage-specific regulatory factors.
1,247 citations
TL;DR: In mice, mammary tumor growth induces the accumulation of tumor-associated macrophage that are phenotypically and functionally distinct from mammary tissue macrophages, which reveal the ontogeny of TAMs and a discrete tumor-elicited inflammatory response, which may provide new opportunities for cancer immunotherapy.
Abstract: Long recognized as an evolutionarily ancient cell type involved in tissue homeostasis and immune defense against pathogens, macrophages are being rediscovered as regulators of several diseases, including cancer. Here we show that in mice, mammary tumor growth induces the accumulation of tumor-associated macrophages (TAMs) that are phenotypically and functionally distinct from mammary tissue macrophages (MTMs). TAMs express the adhesion molecule Vcam1 and proliferate upon their differentiation from inflammatory monocytes, but do not exhibit an "alternatively activated" phenotype. TAM terminal differentiation depends on the transcriptional regulator of Notch signaling, RBPJ; and TAM, but not MTM, depletion restores tumor-infiltrating cytotoxic T cell responses and suppresses tumor growth. These findings reveal the ontogeny of TAMs and a discrete tumor-elicited inflammatory response, which may provide new opportunities for cancer immunotherapy.
1,053 citations
TL;DR: The widespread importance of Wnt signaling in driving tissue renewal has been revealed by the identification of Axin2 and Lgr5, genes expressed in cells that are responding to Wnt signals, and this crucial role in stem cell self renewal is reviewed.
Abstract: BACKGROUND In adult mammalian organisms, multiple tissues—including the skin, blood, stomach, and intestines—are entrapped in a state of permanent regeneration; older cells are constantly shed, and the tissue is continuously being regenerated from resident stem cells. This phenomenon of “tissue renewal” was appreciated by Leblond in 1956, but the underlying mechanism has been unclear. It is now evident that a class of extracellular developmental signaling proteins, known as Wnt signals, animate the continued renewal of several mammalian tissues by fuelling stem cell activity. If the Wnt pathway is inhibited, tissue renewal is crippled. This signaling pathway is an ancient evolutionary program dating from when Wnt signals arose in the simplest multicellular organisms, in which Wnts acted as primordial symmetry-breaking signals crucial for the generation of patterned tissues during embryogenesis. In vertebrates, these signals also function in pattern maintenance: They sustain tissue renewal, enabling tissues to be continuously replenished and maintained over a lifetime. Multiple adult organs are in a state of continual regeneration. In tissues such as the skin, intestines, brain, and mammary glands, Wnt signaling proteins sustain this constant regeneration by inducing stem cells (green cells in the illustration) to grow. This leads to the robust supply of new cells (green) in order to replenish and maintain the tissue. [Image credits are available in the full article online.] ADVANCES In contrast to traditional “long-range” developmental signals, Wnts seem to act as short-range intercellular signals—acting mostly between adjacent cells. Lending credence to this notion, a membrane-tethered Wnt protein variant can fulfill most functions of a normal Wnt protein in Drosophila . Likely explaining the short-range nature of these signals, Wnt proteins are attached to a lipid and therefore are hydrophobic; they cannot freely traverse the extracellular space by themselves. This provides insight into how tissue renewal is regulated. It implies that Wnt signals emanating from the stem cell microenvironment (the “niche”) may influence adjacent stem cells without affecting a broad field of cells located farther away. The concept of an external niche, however, may have to be refined because it is clear that stem cells can sometimes act as their own niche and have unexpected developmental self-organizing capacities. Last, the widespread importance of Wnt signaling in driving tissue renewal has been revealed by the identification of Axin2 and Lgr5 , genes expressed in cells that are responding to Wnt signals. Genetically labeling Axin2 + or Lgr5 + cells in a variety of tissues has revealed that such cells fuel tissue renewal in the intestines, mammary gland, skin, and brain, among other organs. OUTLOOK The amazing continuous self-regeneration of various mammalian tissues over years and decades continues to be an enigmatic terra incognita in biology. For instance, visualization of stem cells in real-time in vivo (through intravital microscopy) has shown that when some stem cells are ablated, they are replaced by more differentiated cells that are recalled to the stem cell niche, whereupon they regain stem cell identity to effect tissue repair. Therefore, lineage barriers between stem cell and differentiated fates are not always stringent and can be traversed during times of tissue damage. Reactivated Wnt signals may be instrumental in this process, and perhaps such signals could be exploited in order to enkindle tissue regeneration after injury or disease. From a pragmatic perspective, Wnt signals have already found practical use in manipulating stem cells, enabling propagation of stem cells in vitro as self-renewing cell populations and as organoids.
1,032 citations
TL;DR: These exciting new insights into the biology of intestinal stem cells have the potential to accelerate the development of stem cell-based therapies and ameliorate cancer treatments.
Abstract: Small populations of adult stem cells are responsible for the remarkable ability of the epithelial lining of the intestine to be efficiently renewed and repaired throughout life. The recent discovery of specific markers for these stem cells, together with the development of new technologies to track endogenous stem cell activity in vivo and to exploit their ability to generate new epithelia ex vivo, has greatly improved our understanding of stem cell-driven homeostasis, regeneration and cancer in the intestine. These exciting new insights into the biology of intestinal stem cells have the potential to accelerate the development of stem cell-based therapies and ameliorate cancer treatments.
976 citations
TL;DR: Mapping the m( 6)A methylome in mouse and human embryonic stem cells reveals the evolutionary conservation and function of m(6)A, a mark of transcriptome flexibility required for stem cells to differentiate to specific lineages.
906 citations
TL;DR: It is concluded that stem cells possess mechanical memory - with YAP/TAZ acting as an intracellular mechanical rheostat - that stores information from past physical environments and influences the cells’ fate.
Abstract: Mechanical cues from the local cellular microenvironment can direct cell fate. Now, experiments with human mesenchymal stem cells cultured on phototunable soft poly(ethylene glycol) hydrogels show that the cells remember past physical environments—with the transcriptional co-activators YAP and TAZ acting as a mechanical rheostat—and therefore that appropriate doses of mechanical cues can be used to manipulate the cells’ fate.
885 citations
TL;DR: A lncRNA expressed exclusively in human dendritic cells (DC), called lnc-DC, is identified that is required for optimal DC differentiation from human monocytes and that regulates DC activation of T cells.
Abstract: Long noncoding RNAs (lncRNAs) play important roles in diverse biological processes; however, few have been identified that regulate immune cell differentiation and function. Here, we identified lnc-DC, which was exclusively expressed in human conventional dendritic cells (DCs). Knockdown of lnc-DC impaired DC differentiation from human monocytes in vitro and from mouse bone marrow cells in vivo and reduced capacity of DCs to stimulate T cell activation. lnc-DC mediated these effects by activating the transcription factor STAT3 (signal transducer and activator of transcription 3). lnc-DC bound directly to STAT3 in the cytoplasm, which promoted STAT3 phosphorylation on tyrosine-705 by preventing STAT3 binding to and dephosphorylation by SHP1. Our work identifies a lncRNA that regulates DC differentiation and also broadens the known mechanisms of lncRNA action.
871 citations
TL;DR: Investigation into the molecular mechanisms and metabolic pathways underlying stem cell self-renewal and differentiation hold great therapeutic promise.
Abstract: A distinctive feature of stem cells is their capacity to self-renew to maintain pluripotency. Studies of genetically-engineered mouse models and recent advances in metabolomic analysis, particularly in haematopoietic stem cells, have deepened our understanding of the contribution made by metabolic cues to the regulation of stem cell self-renewal. Many types of stem cells heavily rely on anaerobic glycolysis, and stem cell function is also regulated by bioenergetic signalling, the AKT-mTOR pathway, Gln metabolism and fatty acid metabolism. As maintenance of a stem cell pool requires a finely-tuned balance between self-renewal and differentiation, investigations into the molecular mechanisms and metabolic pathways underlying these decisions hold great therapeutic promise.
TL;DR: How oxygen sensing in the immune microenvironment shapes immunological response is discussed and how HIF and the hypoxia pathway control innate and adaptive immunity is examined.
TL;DR: It is shown that varying substrate porosity did not significantly change protein tethering, substrate deformations, or the osteogenic and adipogenic differentiation of human adipose-derived stromal cells and marrow-derived mesenchymalStem cells.
Abstract: Stem cells regulate their fate by binding to, and contracting against, the extracellular matrix. Recently, it has been proposed that in addition to matrix stiffness and ligand type, the degree of coupling of fibrous protein to the surface of the underlying substrate, that is, tethering and matrix porosity, also regulates stem cell differentiation. By modulating substrate porosity without altering stiffness in polyacrylamide gels, we show that varying substrate porosity did not significantly change protein tethering, substrate deformations, or the osteogenic and adipogenic differentiation of human adipose-derived stromal cells and marrow-derived mesenchymal stromal cells. Varying protein-substrate linker density up to 50-fold changed tethering, but did not affect osteogenesis, adipogenesis, surface-protein unfolding or underlying substrate deformations. Differentiation was also unaffected by the absence of protein tethering. Our findings imply that the stiffness of planar matrices regulates stem cell differentiation independently of protein tethering and porosity.
TL;DR: It is shown that group 2 innate lymphoid cells (ILC2s) are required to mount a robust Th2 cell response to the protease-allergen papain, suggesting a common pathway in the initiation of Th 2 cell responses to allergen.
TL;DR: There is a switch after birth, when AT2 cells function as stem cells that contribute to alveolar renewal, repair and cancer, and it is proposed that local signals regulate AT2 stem-cell activity.
Abstract: Alveoli are gas-exchange sacs lined by squamous alveolar type (AT) 1 cells and cuboidal, surfactant-secreting AT2 cells. Classical studies suggested that AT1 arise from AT2 cells, but recent studies propose other sources. Here we use molecular markers, lineage tracing and clonal analysis to map alveolar progenitors throughout the mouse lifespan. We show that, during development, AT1 and AT2 cells arise directly from a bipotent progenitor, whereas after birth new AT1 cells derive from rare, self-renewing, long-lived, mature AT2 cells that produce slowly expanding clonal foci of alveolar renewal. This stem-cell function is broadly activated by AT1 injury, and AT2 self-renewal is selectively induced by EGFR (epidermal growth factor receptor) ligands in vitro and oncogenic Kras(G12D) in vivo, efficiently generating multifocal, clonal adenomas. Thus, there is a switch after birth, when AT2 cells function as stem cells that contribute to alveolar renewal, repair and cancer. We propose that local signals regulate AT2 stem-cell activity: a signal transduced by EGFR-KRAS controls self-renewal and is hijacked during oncogenesis, whereas another signal controls reprogramming to AT1 fate.
TL;DR: The de novo generation of three-dimensional human gastric tissue in vitro through the directed differentiation of human pluripotent stem cells is reported, describing a new and robust in vitro system for elucidating the mechanisms underlying human stomach development and disease.
Abstract: Gastric diseases, including peptic ulcer disease and gastric cancer, affect 10% of the world's population and are largely due to chronic Helicobacter pylori infection Species differences in embryonic development and architecture of the adult stomach make animal models suboptimal for studying human stomach organogenesis and pathogenesis, and there is no experimental model of normal human gastric mucosa Here we report the de novo generation of three-dimensional human gastric tissue in vitro through the directed differentiation of human pluripotent stem cells We show that temporal manipulation of the FGF, WNT, BMP, retinoic acid and EGF signalling pathways and three-dimensional growth are sufficient to generate human gastric organoids (hGOs) Developing hGOs progressed through molecular and morphogenetic stages that were nearly identical to the developing antrum of the mouse stomach Organoids formed primitive gastric gland- and pit-like domains, proliferative zones containing LGR5-expressing cells, surface and antral mucous cells, and a diversity of gastric endocrine cells We used hGO cultures to identify novel signalling mechanisms that regulate early endoderm patterning and gastric endocrine cell differentiation upstream of the transcription factor NEUROG3 Using hGOs to model pathogenesis of human disease, we found that H pylori infection resulted in rapid association of the virulence factor CagA with the c-Met receptor, activation of signalling and induction of epithelial proliferation Together, these studies describe a new and robust in vitro system for elucidating the mechanisms underlying human stomach development and disease
TL;DR: Endogenous c-kit+ cells did produce new cardiomyocytes within the heart, although at a percentage of approximately 0.03 or less, and if a preponderance towards cellular fusion is considered, the percentage falls to belowapproximately 0.008.
Abstract: If and how the heart regenerates after an injury event is highly debated. c-kit-expressing cardiac progenitor cells have been reported as the primary source for generation of new myocardium after injury. Here we generated two genetic approaches in mice to examine whether endogenous c-kit(+) cells contribute differentiated cardiomyocytes to the heart during development, with ageing or after injury in adulthood. A complementary DNA encoding either Cre recombinase or a tamoxifen-inducible MerCreMer chimaeric protein was targeted to the Kit locus in mice and then bred with reporter lines to permanently mark cell lineage. Endogenous c-kit(+) cells did produce new cardiomyocytes within the heart, although at a percentage of approximately 0.03 or less, and if a preponderance towards cellular fusion is considered, the percentage falls to below approximately 0.008. By contrast, c-kit(+) cells amply generated cardiac endothelial cells. Thus, endogenous c-kit(+) cells can generate cardiomyocytes within the heart, although probably at a functionally insignificant level.
TL;DR: A high-sensitivity indexing-first chromatin immunoprecipitation approach to profile the dynamics of four chromatin modifications across 16 stages of hematopoietic differentiation and reveals that lineage commitment involves de novo establishment of 17,035 lineage-specific enhancers.
Abstract: Chromatin modifications are crucial for development, yet little is known about their dynamics during differentiation. Hematopoiesis provides a well-defined model to study chromatin state dynamics; however, technical limitations impede profiling of homogeneous differentiation intermediates. We developed a high-sensitivity indexing-first chromatin immunoprecipitation approach to profile the dynamics of four chromatin modifications across 16 stages of hematopoietic differentiation. We identify 48,415 enhancer regions and characterize their dynamics. We find that lineage commitment involves de novo establishment of 17,035 lineage-specific enhancers. These enhancer repertoire expansions foreshadow transcriptional programs in differentiated cells. Combining our enhancer catalog with gene expression profiles, we elucidate the transcription factor network controlling chromatin dynamics and lineage specification in hematopoiesis. Together, our results provide a comprehensive model of chromatin dynamics during development.
TL;DR: It is demonstrated that the intrinsic tendency of stem cells to make patterns can be harnessed by controlling colony geometries and provide a quantitative assay for studying paracrine signaling in early development.
Abstract: Embryos allocate cells to the three germ layers in a spatially ordered sequence. Human embryonic stem cells (hESCs) can generate the three germ layers in culture; however, differentiation is typically heterogeneous and spatially disordered. We show that geometric confinement is sufficient to trigger self-organized patterning in hESCs. In response to BMP4, colonies reproducibly differentiated to an outer trophectoderm-like ring, an inner ectodermal circle and a ring of mesendoderm expressing primitive-streak markers in between. Fates were defined relative to the boundary with a fixed length scale: small colonies corresponded to the outer layers of larger ones. Inhibitory signals limited the range of BMP4 signaling to the colony edge and induced a gradient of Activin-Nodal signaling that patterned mesendodermal fates. These results demonstrate that the intrinsic tendency of stem cells to make patterns can be harnessed by controlling colony geometries and provide a quantitative assay for studying paracrine signaling in early development.
TL;DR: A novel subset of lymphoid precursors in mouse fetal liver and adult bone marrow that transiently express high amounts of PLZF, a transcription factor previously associated with NK T cell development, is identified and identified, establishing novel lineage relationships between ILC, NK and LTi cells, and identifying the common precursor to ILCs, termed ILCP.
Abstract: Innate lymphoid cells (ILCs) specialize in the rapid secretion of polarized sets of cytokines and chemokines to combat infection and promote tissue repair at mucosal barriers. Their diversity and similarities with previously characterized natural killer (NK) cells and lymphoid tissue inducers (LTi) have prompted a provisional classification of all innate lymphocytes into groups 1, 2 and 3 solely on the basis of cytokine properties, but their developmental pathways and lineage relationships remain elusive. Here we identify and characterize a novel subset of lymphoid precursors in mouse fetal liver and adult bone marrow that transiently express high amounts of PLZF, a transcription factor previously associated with NK T cell development, by using lineage tracing and transfer studies. PLZF(high) cells were committed ILC progenitors with multiple ILC1, ILC2 and ILC3 potential at the clonal level. They excluded classical LTi and NK cells, but included a peculiar subset of NK1.1(+)DX5(-) 'NK-like' cells residing in the liver. Deletion of PLZF markedly altered the development of several ILC subsets, but not LTi or NK cells. PLZF(high) precursors also expressed high amounts of ID2 and GATA3, as well as TOX, a known regulator of PLZF-independent NK and LTi lineages. These findings establish novel lineage relationships between ILC, NK and LTi cells, and identify the common precursor to ILCs, termed ILCP. They also reveal the broad, defining role of PLZF in the differentiation of innate lymphocytes.
TL;DR: Using a de novo targeting assay in mouse embryonic stem cells, it is found that PRC1-dependent H2AK119ub1 leads to recruitment of PRC2 and H3K27me3 to effectively initiate a polycomb domain, providing a surprising PRC 1-dependent logic forPRC2 occupancy at target sites in vivo.
TL;DR: This study has successfully directed the differentiation of human embryonic stem cells (hESCs) through posterior primitive streak and IM under fully chemically defined monolayer culture conditions using growth factors used during normal embryogenesis, resulting in the synchronous induction of UB and MM that forms a self-organizing structure, including nephron formation, in vitro.
Abstract: With the prevalence of end-stage renal disease rising 8% per annum globally, there is an urgent need for renal regenerative strategies. The kidney is a mesodermal organ that differentiates from the intermediate mesoderm (IM) through the formation of a ureteric bud (UB) and the interaction between this bud and the adjacent IM-derived metanephric mesenchyme (MM). The nephrons arise from a nephron progenitor population derived from the MM (ref. ). The IM itself is derived from the posterior primitive streak. Although the developmental origin of the kidney is well understood, nephron formation in the human kidney is completed before birth. Hence, there is no postnatal stem cell able to replace lost nephrons. In this study, we have successfully directed the differentiation of human embryonic stem cells (hESCs) through posterior primitive streak and IM under fully chemically defined monolayer culture conditions using growth factors used during normal embryogenesis. This differentiation protocol results in the synchronous induction of UB and MM that forms a self-organizing structure, including nephron formation, in vitro. Such hESC-derived components show broad renal potential ex vivo, illustrating the potential for pluripotent-stem-cell-based renal regeneration.
TL;DR: It is proposed that the transition of quiescent stem cells into GAlert functions as an ‘alerting’ mechanism, an adaptive response that positions stem cells to respond rapidly under conditions of injury and stress, priming them for cell cycle entry.
Abstract: A mouse study reveals that the stem cell quiescent state is composed of two distinct phases, G0 and GAlert; stem cells reversibly transition between these two phases in response to systemic environmental stimuli acting through the mTORC1 pathway. This paper demonstrates that the in vivo stem-cell quiescent state is composed of distinct phases, much like the phases of the cell cycle. Thomas Rando and colleagues studied stem-cell quiescence in muscle stem cells in vivo and identified a quiescent phase that they call GAlert, which is distinct from the familiar G0 state and is stable, reversible and regulated by environmental stimuli through mTORC1. The authors propose that the transition of quiescent stem cells into GAlert functions as an 'alerting' mechanism by which stem cells can rapidly respond to injury and stress without requiring cell cycle entry or a cell fate commitment. A unique property of many adult stem cells is their ability to exist in a non-cycling, quiescent state1. Although quiescence serves an essential role in preserving stem cell function until the stem cell is needed in tissue homeostasis or repair, defects in quiescence can lead to an impairment in tissue function2. The extent to which stem cells can regulate quiescence is unknown. Here we show that the stem cell quiescent state is composed of two distinct functional phases, G0 and an ‘alert’ phase we term GAlert. Stem cells actively and reversibly transition between these phases in response to injury-induced systemic signals. Using genetic mouse models specific to muscle stem cells (or satellite cells), we show that mTORC1 activity is necessary and sufficient for the transition of satellite cells from G0 into GAlert and that signalling through the HGF receptor cMet is also necessary. We also identify G0-to-GAlert transitions in several populations of quiescent stem cells. Quiescent stem cells that transition into GAlert possess enhanced tissue regenerative function. We propose that the transition of quiescent stem cells into GAlert functions as an ‘alerting’ mechanism, an adaptive response that positions stem cells to respond rapidly under conditions of injury and stress, priming them for cell cycle entry.
TL;DR: The issue of cell polarity is discussed, as well as specific subcellular features of these cells that are relevant for their modes of division and daughter cell fate, which help gain insight into key developmental and evolutionary mechanisms underlying neocortex expansion.
Abstract: Neural stem and progenitor cells have a central role in the development and evolution of the mammalian neocortex. In this review, we first provide a set of criteria to classify the various types of cortical stem and progenitor cells. We then discuss the issue of cell polarity, as well as specific subcellular features of these cells that are relevant for their modes of division and daughter cell fate. In addition, cortical stem and progenitor cell behavior is placed into a tissue context, with consideration of extracellular signals and cell-cell interactions. Finally, the differences across species regarding cortical stem and progenitor cells are dissected to gain insight into key developmental and evolutionary mechanisms underlying neocortex expansion.
TL;DR: Genome-wide profiling of pluripotent cells and differentiated cells suggests global chromatin remodelling during differentiation, which results in a progressive transition from a fairly open chromatin configuration to a more compact state, rather than merely stabilizing the gene expression changes that are driven by developmental transcription factors.
Abstract: This Review describes the diverse roles for histone-modifying and chromatin-remodelling enzymes in mammalian differentiation. These enzymes are involved in both maintaining pluripotency and specifying cell lineage commitment. Recent progress includes their functional characterization in mouse modelsin vivoand a new appreciation of their multifaceted molecular functions. Cellular differentiation is, by definition, epigenetic. Genome-wide profiling of pluripotent cells and differentiated cells suggests global chromatin remodelling during differentiation, which results in a progressive transition from a fairly open chromatin configuration to a more compact state. Genetic studies in mouse models show major roles for a variety of histone modifiers and chromatin remodellers in key developmental transitions, such as the segregation of embryonic and extra-embryonic lineages in blastocyst stage embryos, the formation of the three germ layers during gastrulation and the differentiation of adult stem cells. Furthermore, rather than merely stabilizing the gene expression changes that are driven by developmental transcription factors, there is emerging evidence that chromatin regulators have multifaceted roles in cell fate decisions.
TL;DR: T cells from patients with heterozygous for three different germline, gain-of-function mutations in PIK3CD exhibited increased phosphorylation of the kinase Akt and hyperactivation of the metabolic checkpoint kinase mTOR, enhanced glucose uptake and terminal effector differentiation in vitro.
Abstract: The p110δ subunit of phosphatidylinositol-3-OH kinase (PI(3)K) is selectively expressed in leukocytes and is critical for lymphocyte biology. Here we report fourteen patients from seven families who were heterozygous for three different germline, gain-of-function mutations in PIK3CD (which encodes p110δ). These patients presented with sinopulmonary infections, lymphadenopathy, nodular lymphoid hyperplasia and viremia due to cytomegalovirus (CMV) and/or Epstein-Barr virus (EBV). Strikingly, they had a substantial deficiency in naive T cells but an over-representation of senescent effector T cells. In vitro, T cells from patients exhibited increased phosphorylation of the kinase Akt and hyperactivation of the metabolic checkpoint kinase mTOR, enhanced glucose uptake and terminal effector differentiation. Notably, treatment with rapamycin to inhibit mTOR activity in vivo partially restored the abundance of naive T cells, largely 'rescued' the in vitro T cell defects and improved the clinical course.
TL;DR: It is suggested that autologous hiPSC-RPE cell sheets may serve as a useful form of graft for use in tissue replacement therapy for AMD.
Abstract: Age-related macular degeneration (AMD) causes severe visual impairment due in part to age-dependent impairment of retinal pigment epithelium (RPE). It has been suggested that autologous human induced pluripotent stem cells (hiPSCs) may represent a useful cell source for the generation of graft RPE. We generated hiPSC-derived RPE (hiPSC-RPE) cell sheets optimized to meet clinical use requirements, including quality, quantity, consistency, and safety. These cell sheets are generated as a monolayer of cells without any artificial scaffolds, express typical RPE markers, form tight junctions that exhibit polarized secretion of growth factors, and show phagocytotic ability and gene-expression patterns similar to those of native RPE. Additionally, upon transplantation, autologous nonhuman primate iPSC-RPE cell sheets showed no immune rejection or tumor formation. These results suggest that autologous hiPSC-RPE cell sheets may serve as a useful form of graft for use in tissue replacement therapy for AMD.
TL;DR: Three distinct states of CD8 T cell dysfunction are discussed, with an emphasis on: (i) T cell tolerance to self-antigens (self-tolerance); (ii) Tcell exhaustion during chronic infections; and (iii) tumor-induced Tcell dysfunction.
TL;DR: A hierarchy of stem and progenitor cells has been shown to exist among the mammary epithelium, and there is accumulating evidence for a heterogeneous MaSC compartment comprising fetal MaSCs, slow-cycling cells, and both long-term and short-term repopulating cells.
Abstract: The mammary epithelium is highly responsive to local and systemic signals, which orchestrate morphogenesis of the ductal tree during puberty and pregnancy. Based on transplantation and lineage tracing studies, a hierarchy of stem and progenitor cells has been shown to exist among the mammary epithelium. Lineage tracing has highlighted the existence of bipotent mammary stem cells (MaSCs) in situ as well as long-lived unipotent cells that drive morphogenesis and homeostasis of the ductal tree. Moreover, there is accumulating evidence for a heterogeneous MaSC compartment comprising fetal MaSCs, slow-cycling cells, and both long-term and short-term repopulating cells. In parallel, diverse luminal progenitor subtypes have been identified in mouse and human mammary tissue. Elucidation of the normal cellular hierarchy is an important step toward understanding the "cells of origin" and molecular perturbations that drive breast cancer.
TL;DR: A comprehensive integrated genomic analysis of young and aged HSCs showed increased DNA methylation at transcription factor binding sites associated with differentiation-promoting genes combined with a reduction at genes associated with HSC maintenance, paralleling phenotypic HSC aging behavior.