Cell Lineage Fate Research Articles

Epigenetic control of cell fate - an interview with Maria-Elena Torres-Padilla.

Maria-Elena Torres-Padilla's research is focused on how cell fate arises from a single-cell embryo, the fertilized egg or zygote. After the initial divisions, cell potency becomes restricted, originating the first cell lineage fates. She studies how epigenetic information controls transitions in cell identity and cellular reprogramming during embryonic development. Currently, she is the founding Director of the Institute of Epigenetics and Stem Cells, Helmholtz Centre, and Professor of Stem Cell Biology at the Ludwigs Maximilians University in Munich. In this interview, Maria-Elena Torres-Padilla talks to us about her beginnings in the biology field in Mexico. She also tells us about how she became interested in the control of genome regulation within the nucleus during the transition from totipotency to pluripotency and how the control of gene regulation and chromatin organization during the early stages of cell fate decision in the one-cell embryo occurs. She considers that science has no borders; visiting Mexico gives her the possibility to discuss her work with colleagues and the new generation of students trained in Mexico.

An overview of signaling pathways regulating YAP/TAZ activity.

YAP and TAZ are ubiquitously expressed homologous proteins originally identified as penultimate effectors of the Hippo signaling pathway, which plays a key role in maintaining mammalian tissue/organ size. Presently, it is known that YAP/TAZ also interact with various non-Hippo signaling pathways, and have diverse roles in multiple biological processes, including cell proliferation, tissue regeneration, cell lineage fate determination, tumorigenesis, and mechanosensing. In this review, we first examine the various microenvironmental cues and signaling pathways that regulate YAP/TAZ activation, through the Hippo and non-Hippo signaling pathways. This is followed by a brief summary of the interactions of YAP/TAZ with TEAD1-4 and a diverse array of other non-TEAD transcription factors. Finally, we offer a critical perspective on how increasing knowledge of the regulatory mechanisms of YAP/TAZ signaling might open the door to novel therapeutic applications in the interrelated fields of biomaterials, tissue engineering, regenerative medicine and synthetic biology.

Role of YAP/TAZ in Cell Lineage Fate Determination and Related Signaling Pathways.

The penultimate effectors of the Hippo signaling pathways YAP and TAZ, are transcriptional co-activator proteins that play key roles in many diverse biological processes, ranging from cell proliferation, tumorigenesis, mechanosensing and cell lineage fate determination, to wound healing and regeneration. In this review, we discuss the regulatory mechanisms by which YAP/TAZ control stem/progenitor cell differentiation into the various major lineages that are of interest to tissue engineering and regenerative medicine applications. Of particular interest is the key role of YAP/TAZ in maintaining the delicate balance between quiescence, self-renewal, proliferation and differentiation of endogenous adult stem cells within various tissues/organs during early development, normal homeostasis and regeneration/healing. Finally, we will consider how increasing knowledge of YAP/TAZ signaling might influence the trajectory of future progress in regenerative medicine.

Single-cell Transcriptome Profiling reveals Dermal and Epithelial cell fate decisions during Embryonic Hair Follicle Development.

It is estimated that 50% of men and 25% of women worldwide suffer from hair loss, and therefore it is of great significance to investigate the molecular pathways driving hair follicle de novo morphogenesis. However, due to high cellular heterogeneity and the asynchronous development of hair follicles, our current understanding of the molecular mechanisms involved in follicle development remains limited.Methods: Single-cell suspensions from the dorsal skin of E13.5 (induction stage), E16.5 (organogenesis) fetal mice, and newborn mice (cytodifferentiation stage, postnatal day 0, P0) were prepared for unbiased single-cell RNA sequencing. To delineate the single-cell transcriptional landscape during hair follicle de novo morphogenesis, we performed t-distributed Stochastic Neighbor Embedding (tSNE), pseudotime cell trajectory inference, and regulon enrichment analysis to dissect cellular heterogeneity and reveal the molecular pathways underlying major cell type cell fate decisions. To validate our analysis, we further performed immunohistochemistry analysis of the key molecules involved during hair follicle morphogenesis. Meanwhile, intercellular communication between different cell populations was inferred based on a priori knowledge of ligand-receptor pairs.Results: Based on tSNE analysis, we identified 14 cell clusters from skin tissue and delineated their cellular identity from specific gene expression profiles. By using pseudotime ordering analysis, we successfully constructed the epithelium/dermal cell lineage differentiation trajectory. For dermal cell lineage, our analysis here recapitulated the dynamic gene expression profiles during dermal condensate (DC) cell fate commitment and delineated the heterogeneity of the different dermal papilla (DP) cell populations during in utero hair follicle development. For the epithelium cell lineage, our analysis revealed the dynamic gene expression profiles of the underappreciated matrix, interfollicular epidermis (IFE), hair shaft and inner root sheath (IRS) cell populations. Furthermore, single-cell regulatory network inference and clustering analysis revealed key regulons during cell fate decisions. Finally, intercellular communication analysis demonstrated that strong intercellular communication was involved during early hair follicle development.Conclusions: Our findings here provide a molecular landscape during hair follicle epithelium/dermal cell lineage fate decisions, and recapitulate the sequential activation of core regulatory transcriptional factors (TFs) in different cell populations during hair follicle morphogenesis. More importantly, our study here represents a valuable resource for understanding the molecular pathways involved during hair follicle de novo morphogenesis, which will have implications for future hair loss treatments.

GMCSF-neuroantigen vaccines engender FOXP3+ regulatory T cell responses through low-efficiency self-antigen recognition events integrated through diminished CD40L-CD40 signaling

Abstract Neuroantigen (NAg)-specific tolerogenic vaccines that induce myelin-specific FOXP3+ regulatory T cells (Tregs) may be an effective treatment for Multiple Sclerosis. Previous studies showed that fusion proteins comprised of GM-CSF and NAg (GMCSF-NAg) are potent tolerogens that inhibit several rodent models of experimental autoimmune encephalomyelitis. GMCSF-NAg-induced T cell responses were investigated in vivo by use of 2D2-FIG mice, which have a FOXP3 GFP reporter (FIG) and a transgenic TCR (2D2) which recognizes myelin oligodendrocyte glycoprotein peptide 35–55 (MOG) as a low-efficiency antigen and neurofilament medium peptide 13–37 (NFM) as a high-efficiency antigen. A single subcutaneous vaccination of 2D2-FIG mice with GMCSF-MOG resulted in high numbers and percentages of Tregs in the blood, spleen, and lymph nodes, whereas GMCSF-NFM elicited a dominant conventional T cell (Tcon) response. To determine how low and high-efficiency TCR responses regulate cell lineage fate, we investigated TCR-induced CD40L expression. GMCSF-NFM, but not GMCSF-MOG, induced significant CD40L expression when cultured with 2D2 responder T cells. Pretreatment of 2D2-FIG mice with an agonistic anti-CD40 monoclonal antibody prevented GMCSF-MOG induction of Tregs and favored Tcon responses. MOG35–55 was a partial TCR antagonist that blocked NFM stimulation of CD40L expression in 2D2 T cell cultures. Similarly, GMCSF-MOG was functionally dominant and induced Tregs in 2D2-FIG mice when mixed with an equimolar dose of GMCSF-NFM. These data indicated that low-efficiency antigen recognition is a key parameter for the induction of Treg responses and is in part controlled through CD40L-CD40 signaling pathways to determine T cell lineage fate.

Single-cell lineage tracing by endogenous mutations enriched in transposase accessible mitochondrial DNA.

Simultaneous measurement of cell lineage and cell fates is a longstanding goal in biomedicine. Here we describe EMBLEM, a strategy to track cell lineage using endogenous mitochondrial DNA variants in ATAC-seq data. We show that somatic mutations in mitochondrial DNA can reconstruct cell lineage relationships at single cell resolution with high sensitivity and specificity. Using EMBLEM, we define the genetic and epigenomic clonal evolution of hematopoietic stem cells and their progenies in patients with acute myeloid leukemia. EMBLEM extends lineage tracing to any eukaryotic organism without genetic engineering.

Convergence of TGFβ and BMP signaling in regulating human bone marrow stromal cell differentiation

Targeting regulatory signaling pathways that control human bone marrow stromal (skeletal or mesenchymal) stem cell (hBMSC) differentiation and lineage fate determination is gaining momentum in the regenerative medicine field. Therefore, to identify the central regulatory mechanism of osteoblast differentiation of hBMSCs, the molecular phenotypes of two clonal hBMSC lines exhibiting opposite in vivo phenotypes, namely, bone forming (hBMSC+bone) and non-bone forming (hBMSC−Bone) cells, were studied. Global transcriptome analysis revealed significant downregulation of several TGFβ responsive genes, namely, TAGLN, TMP1, ACTA2, TGFβ2, SMAD6, SMAD9, BMP2, and BMP4 in hBMSC−Bone cells and upregulation on SERPINB2 and NOG. Transcriptomic data was associated with marked reduction in SMAD2 protein phosphorylation, which thereby implies the inactivation of TGFβ and BMP signaling in those cells. Concordantly, activation of TGFβ signaling in hBMSC−Bone cells using either recombinant TGFβ1 protein or knockdown of SERPINB2 TGFβ-responsive gene partially restored their osteoblastic differentiation potential. Similarly, the activation of BMP signaling using exogenous BMP4 or via siRNA-mediated knockdown of NOG partially restored the differentiation phenotype of hBMSC−Bone cells. Concordantly, recombinant NOG impaired ex vivo osteoblastic differentiation of hBMSC+Bone cells, which was associated with SERBINB2 upregulation. Our data suggests the existence of reciprocal relationship between TGFB and BMP signaling that regulates hBMSC lineage commitment and differentiation, whilst provide a plausible strategy for generating osteoblastic committed cells from hBMSCs for clinical applications.

Metabolic Reprogramming of Myeloid Cells in Response to Factors of “Emergency” Myelopoiesis By Myeloid-Specific PD-1 Ablation, Regulates Myeloid Lineage Fate Commitment and Anti-Tumor Immunity

PD-1 is a T cell inhibitor for which blocking agents have achieved success as anti-cancer therapeutics. The current view is that cancer limits host immune responses by upregulating PD-L1 in the tumor microenvironment (TME) thereby causing PD-1 ligation and inactivation of CD8+ Teff cells. However, PD-L1 expression in the TME does not always correlate with therapeutic response. Thus, the mechanism(s) by which PD-1 blockade reverses compromised anti-tumor immunity are poorly understood. The rapid increase in hematopoietic cell output that occurs in response to immunologic stress is known as emergency myelopoiesis. Low-level stimulation by cancer-generated factors induces modest but continuous expansion of myeloid progenitors (MP) (common myeloid progenitors (CMP) and granulocyte/macrophage progenitors (GMP)) albeit with hindered differentiation, leading to output of tumor-promoting myeloid-derived suppressor cells (MDSCs). We determined that myeloid cells expanding during cancer-driven emergency myelopoiesis in tumor-bearing mice express PD-1 and PD-L1. Using PD-1 KO mice we found that PD-1 deletion prevented the accumulation of GMP and stimulated the output of Ly6Chi effector monocytes, macrophages and dendritic cells (DC). To determine whether these outcomes were mediated by a myeloid-intrinsic impact of PD-1 ablation or by the effects of PD-1neg T cells on myeloid cells, we generated mice with conditional targeting of the Pdcd1 gene (PD-1f/f) and selectively eliminated PD-1 in myeloid cells (PD-1f/fLysMcre) or T cells (PD-1f/fCD4cre). Myeloid-specific, but not T cell-specific PD-1 ablation, prevented the accumulation of GMP while promoting the output of effector-like myeloid cells expressing CD80, CD86, CD16/32 (FcRII/III) and CD88 (C5aR). Myeloid cells with PD-1 ablation had elevated expression of IRF8 that drives monocyte and DC differentiation and decreased expression of the MDSC hallmark markers IL-4R, CD206, ARG1 and CD38. Nutrient utilization has a decisive role on the fate of hematopoietic progenitors (HP) and MP. Stemness and pluripotency are regulated by maintenance of glycolysis whereas switch to mitochondrial metabolism is associated with differentiation. To examine whether PD-1 ablation affected these metabolic proceces, bone marrow (BM) from PD-1f/f and PD-1f/fLysMcre mice was cultured with G-CSF/GM-CSF/IL-6, key drivers of emergency myelopoiesis. MP differentiation was documented by decrease of Linneg and increase of Linpos cells, which was more prominent in PD-1f/fLysMcre BM cultures. This coincided with increase of CD45+CD11b+ and dominance of Ly6C+ monocytic cells consistent with a cell-intrinsic mechanism of monocytic lineage commitment. PD-1f/fLysMcre MP had elevated mTORC1, Erk1/2 and Stat1 activation, and enhanced glucose uptake and mitochondrial biogenesis. Bioenergetics studies showed robust development of a mitochondrial-dominant profile, consistent with metabolism-driven enhanced differentiation of MP. Mass spectrometry revealed enhanced intermediates of glycolysis, PPP and TCA cycle, but the most prominent difference was the increased cholesterol. Because mTORC1 signaling, which was enhanced in PD-1f/fLysMcre MP, activates de novo lipid and cholesterol synthesis via SREBP1, we examined the mevalonate pathway of cholesterol synthesis. mRNA for genes mediating cholesterol synthesis and uptake was increased whereas mRNA for genes mediating cholesterol metabolism was decreased. Cholesterol induces a proinflammatory program in myeloid cells, drives differentiation of monocytes, macrophages and DC and promotes antigen-presenting function. We examined how such changes in myeloid cells might affect the function of T cells, which are key anti-tumor mediators. Compared to tumor-bearing PD-1f/f mice, PD-1f/fLysMcre tumor-bearers had no quantitative T cell differences but had an increase in IFNγ- IL-17-, and IL-10-expressing CD8+ Teff-mem and IL-2-expressing Tcentral-mem cells, consistent with superior functionality. These changes correlated with enhanced anti-tumor protection despite preserved PD-1 expression in T cells. Our findings reveal a previously unidentified role of PD-1 in metabolism-driven myeloid cell lineage fate commitment and differentiation and suggest that switch to effector myeloid cells might be a key mechanism by which PD-1 blockade mediates systemic anti-tumor immunity. DisclosuresNo relevant conflicts of interest to declare.

TET mediated epigenetic regulation of iNKT cell lineage fate choice and function

During the last years, intensive research has shed light in the transcriptional networks that shape the invariant NKT (iNKT) cell lineage and guide the choices towards functionally distinct iNKT cell subsets (Constantinides and Bendelac, 2013; Engel and Kronenberg, 2014; Gapin, 2016; Kim et al., 2015). However, the epigenetic players that regulate gene expression and orchestrate the iNKT cell lineage choices remain poorly understood. Here, we summarize recent advances in our understanding of epigenetic regulation of iNKT cell development and lineage choice. Particular emphasis is placed on DNA modifications and the Ten Eleven Translocation (TET) family of DNA demethylases.

SOX9 is dispensable for the initiation of epigenetic remodeling and the activation of marker genes at the onset of chondrogenesis.

SOX9 controls cell lineage fate and differentiation in major biological processes. It is known as a potent transcriptional activator of differentiation-specific genes, but its earliest targets and its contribution to priming chromatin for gene activation remain unknown. Here, we address this knowledge gap using chondrogenesis as a model system. By profiling the whole transcriptome and the whole epigenome of wild-type and Sox9-deficient mouse embryo limb buds, we uncover multiple structural and regulatory genes, including Fam101a, Myh14, Sema3c and Sema3d, as specific markers of precartilaginous condensation, and we provide evidence of their direct transactivation by SOX9. Intriguingly, we find that SOX9 helps remove epigenetic signatures of transcriptional repression and establish active-promoter and active-enhancer marks at precartilage- and cartilage-specific loci, but is not absolutely required to initiate these changes and activate transcription. Altogether, these findings widen our current knowledge of SOX9 targets in early chondrogenesis and call for new studies to identify the pioneer and transactivating factors that act upstream of or along with SOX9 to prompt chromatin remodeling and specific gene activation at the onset of chondrogenesis and other processes.

Effects of Nutrients, Mainly from Mediterranean Dietary Foods, on Mesenchymal Stem Derived Cells: Growth or Differentiation

During the last decade the interest for the mesenchymal cells is growing due to their possible uses in therapies to treat certain degenerative pathologies. Mesenchymal stem cells have been found in the bone marrow and they have been shown to be responsible for bone repair and fat cells production. Mesenchymal stromal cells can be obtained from a wide variety of tissues in addition to bone marrow and can differentiate into many other cell types. The study of cell differentiation and programming provides new models for drug discovery and cell therapy that now overcomes gene therapy. Senescence, cancer development and degenerative diseases depend on mesenchymal cells contribution to tissue homeostasis. On the other hand, diet and life style are included among risk factors, which can contribute to the success of pharmacological treatments. This review focuses on nutrients from Mediterranean diet and supplements, which have been shown to influence mesenchymal stem cells and cells derived from them. Dietary intake of nutrients impairs both in vitro and in vivo observations, this review aims to gather the results about the effects of food compounds on mesenchymal cells from which adipocytes and osteoblasts derive. Amino acids and proteins, carbohydrates, lipids, fatty acids and vegetable secondary metabolites, differently act on mesenchymal cells bearing on modulation of gene expression and controlling the fate of cell lineages. Remarkable, the analysis of literature shows that the main effect of nutrients on mesenchymal cells is the stimulation of transcription factors which address the cells toward proliferation or differentiation. For instance, carbohydrates, simple or complex, and lipids appear to stimulate the PPAR receptors, whereas proteins and amino acids result to act on the mTOR system and they can also stimulate the MyoD-1 transcription factor and cooperating proteins. In conclusion, nutrients can promote cell growth and differentiation of mesenchymal cells.

Specialized Vacuoles of Myrosin Cells: Chemical Defense Strategy in Brassicales Plants.

Plant vacuoles display many versatile functions. Vacuoles in vegetative tissues are generally involved in protein degradation, and are called lytic vacuoles. However, vegetative vacuoles in specialized cells can accumulate large concentrations of proteins, such as those in idioblast myrosin cells along veins in the order Brassicales, which store large amounts of myrosinases (thioglucoside glucohydrolase and thioglucoside glucohydrolase). Myrosinases cleave the bond between sulfur and glucose in sulfur-rich compounds (glucosinolates) to produce toxic compounds (isothiocyanates) when plants are damaged by pests. This defense strategy is called the myrosinase-glucosinolate system. Recent studies identified atypical myrosinases, PENETRATION 2 (PEN2) and PYK10, along with key components for development of myrosin cells. In this review, we discuss three topics in the myrosinase-glucosinolate system. First, we summarize the complexity and importance of the myrosinase-glucosinolate system, including classical myrosinases, atypical myrosinases and the system that counteracts the myrosinase-glucosinolate system. Secondly, we describe molecular machineries underlying myrosin cell development, including specific reporters, cell lineage, cell differentiation and cell fate determination. The master regulators for myrosin cell differentiation, FAMA and SCREAM, are key transcription factors involved in guard cell differentiation. This indicates that myrosin cells and guard cells share similar transcriptional networks. Finally, we hypothesize that the myrosinase-glucosinolate system may have originated in stomata of ancestral Brassicales plants and, after that, plants co-opted this defense strategy into idioblasts near veins at inner tissue layers.

Cell lineage and cell cycling analyses of the 4d micromere using live imaging in the marine annelid Platynereis dumerilii.

Cell lineage, cell cycle, and cell fate are tightly associated in developmental processes, but in vivo studies at single-cell resolution showing the intricacies of these associations are rare due to technical limitations. In this study on the marine annelid Platynereis dumerilii, we investigated the lineage of the 4d micromere, using high-resolution long-term live imaging complemented with a live-cell cycle reporter. 4d is the origin of mesodermal lineages and the germline in many spiralians. We traced lineages at single-cell resolution within 4d and demonstrate that embryonic segmental mesoderm forms via teloblastic divisions, as in clitellate annelids. We also identified the precise cellular origins of the larval mesodermal posterior growth zone. We found that differentially-fated progeny of 4d (germline, segmental mesoderm, growth zone) display significantly different cell cycling. This work has evolutionary implications, sets up the foundation for functional studies in annelid stem cells, and presents newly established techniques for live imaging marine embryos.

Exploiting Heparan Sulfate Proteoglycans in Human Neurogenesis-Controlling Lineage Specification and Fate.

Unspecialized, self-renewing stem cells have extraordinary application to regenerative medicine due to their multilineage differentiation potential. Stem cell therapies through replenishing damaged or lost cells in the injured area is an attractive treatment of brain trauma and neurodegenerative neurological disorders. Several stem cell types have neurogenic potential including neural stem cells (NSCs), embryonic stem cells (ESCs), induced pluripotent stem cells (iPSCs), and mesenchymal stem cells (MSCs). Currently, effective use of these cells is limited by our lack of understanding and ability to direct lineage commitment and differentiation of neural lineages. Heparan sulfate proteoglycans (HSPGs) are ubiquitous proteins within the stem cell microenvironment or niche and are found localized on the cell surface and in the extracellular matrix (ECM), where they interact with numerous signaling molecules. The glycosaminoglycan (GAG) chains carried by HSPGs are heterogeneous carbohydrates comprised of repeating disaccharides with specific sulfation patterns that govern ligand interactions to numerous factors including the fibroblast growth factors (FGFs) and wingless-type MMTV integration site family (Wnts). As such, HSPGs are plausible targets for guiding and controlling neural stem cell lineage fate. In this review, we provide an overview of HSPG family members syndecans and glypicans, and perlecan and their role in neurogenesis. We summarize the structural changes and subsequent functional implications of heparan sulfate as cells undergo neural lineage differentiation as well as outline the role of HSPG core protein expression throughout mammalian neural development and their function as cell receptors and co-receptors. Finally, we highlight suitable biomimetic approaches for exploiting the role of HSPGs in mammalian neurogenesis to control and tailor cell differentiation into specific lineages. An improved ability to control stem cell specific neural lineage fate and produce abundant cells of lineage specificity will further advance stem cell therapy for the development of improved repair of neurological disorders. We propose a deeper understanding of HSPG-mediated neurogenesis can potentially provide novel therapeutic targets of neurogenesis.

Nonsense-Mediated RNA Decay Influences Human Embryonic Stem Cell Fate.

SummaryNonsense-mediated RNA decay (NMD) is a highly conserved pathway that selectively degrades specific subsets of RNA transcripts. Here, we provide evidence that NMD regulates early human developmental cell fate. We found that NMD factors tend to be expressed at higher levels in human pluripotent cells than in differentiated cells, raising the possibility that NMD must be downregulated to permit differentiation. Loss- and gain-of-function experiments in human embryonic stem cells (hESCs) demonstrated that, indeed, NMD downregulation is essential for efficient generation of definitive endoderm. RNA-seq analysis identified NMD target transcripts induced when NMD is suppressed in hESCs, including many encoding signaling components. This led us to test the role of TGF-β and BMP signaling, which we found NMD acts through to influence definitive endoderm versus mesoderm fate. Our results suggest that selective RNA decay is critical for specifying the developmental fate of specific human embryonic cell lineages.

The transcription factor IRF8 regulates natural killer cell development and response to cytomegalovirus infection

Abstract Interferon regulatory factor 8 (IRF8) is a transcription factor critical for specifying monocyte and dendritic cell lineage fate and for directing B cell development, yet its function in natural killer (NK) cells is not understood. NK cells are innate lymphocytes that develop in the bone marrow and are capable of antigen-specific clonal proliferation. We observe in mixed bone marrow chimeric mice that despite a prevalent NK progenitor (NKP) population compared to wild-type, peripheral Irf8−/− NK cells exhibit proper maturation and full functionality. However, using an adoptive transfer system, we demonstrate that IRF8 is indispensable for robust expansion of NK cells in response to mouse cytomegalovirus (MCMV). Consistent with this finding, Ly49H+ NK cells upregulate Irf8 transcript during the early stages of MCMV infection. Furthermore, the Irf8 locus is dynamically regulated upon activation, showing extensive STAT4 binding at promoter and enhancer regions, and upregulation of the activating epigenetic marks H3K4me3 and H3K4Ac27. Thus, our work elucidates the functional contribution of IRF8 during NK cell development and antiviral responses.

Concise Review: Plasma and Nuclear Membranes Convey Mechanical Information to Regulate Mesenchymal Stem Cell Lineage.

Numerous factors including chemical, hormonal, spatial, and physical cues determine stem cell fate. While the regulation of stem cell differentiation by soluble factors is well-characterized, the role of mechanical force in the determination of lineage fate is just beginning to be understood. Investigation of the role of force on cell function has largely focused on "outside-in" signaling, initiated at the plasma membrane. When interfaced with the extracellular matrix, the cell uses integral membrane proteins, such as those found in focal adhesion complexes to translate force into biochemical signals. Akin to these outside-in connections, the internal cytoskeleton is physically linked to the nucleus, via proteins that span the nuclear membrane. Although structurally and biochemically distinct, these two forms of mechanical coupling influence stem cell lineage fate and, when disrupted, often lead to disease. Here we provide an overview of how mechanical coupling occurs at the plasma and nuclear membranes. We also discuss the role of force on stem cell differentiation, with focus on the biochemical signals generated at the cell membrane and the nucleus, and how those signals influence various diseases. While the interaction of stem cells with their physical environment and how they respond to force is complex, an understanding of the mechanical regulation of these cells is critical in the design of novel therapeutics to combat diseases associated with aging, cancer, and osteoporosis. Stem Cells 2016;34:1455-1463.

Epigenetic Regulation Shapes the Stem Cells State.

Epigenetic Regulation Shapes the Stem Cells State.

When Family History Matters: The Importance of Lineage Analyses and Fate Maps for Explaining Animal Development.

Initial interest in understanding how the fertilized egg becomes a multicellular animal suggested two possible answers: either the embryo came from preformed components or it arose through epigenetic processes. Extensive research during the past few decades has identified aspects of development that depend on preformed elements, such as cytoplasmic components and a cell's lineage; it also has identified aspects that depend on epigenetic processes, such as cell interactions and morphogen gradients. These advances have depended on understanding embryonic cell lineage and cell fate. This essay explains how lineage analysis and fate mapping have contributed to our current understanding of embryonic development.

Asymmetric Allospecific Signals Shape iNKT Cell Lineage Fate Decisions

Invariant NKT (iNKT) cells are glycolipid-reactive alpha/beta T cells which have an important role in the regulation of GVHD after allogeneic bone marrow transplantation. During thymic development, murine iNKT cells divide into three transcriptionally distinct lineages-NKT1, NKT2, and NKT17 that differ in their cytokine expression profile both at rest and upon antigen recognition via their TCR. Given that the lineage profile of iNKT cells varies dramatically between inbred strains of mice, it has been postulated that recognition of allospecific glycolipids determines iNKT cell lineage-fate decisions. Therefore, we challenged this hypothesis in a murine model of prenatal allogeneic transplantation to determine if the lineage commitment of immature iNKT cells was intrinsically programmed or extrinsically regulated by the allospecific environment during development.Prenatal allogeneic chimeras were established by in utero transplantation of E14 fetal liver light density cells into age-matched allogeneic fetal recipients (Balb/c to B6 or B6 to Balb/c). In this model, immature iNKT cells of both donor and host origin have the capacity to participate in education as CD1d on bone marrow-derived cells regulate the maturation of developing iNKT cells. This permitted an analysis of the impact of either host-to-donor or donor-to-host environmental cues in directing iNKT cell lineage-fate decisions. iNKT cell populations were identified using flow cytometric analysis of the transcription factors PLZF and T-bet. The lineage profile for donor and host thymic iNKT cells from chimeric mice were compared to the thymic iNKT cell population in naïve controls.As shown, B6 iNKT cells in prenatal chimeras exhibited a predominance of the NKT1 lineage in either the donor or the host situation similar to their frequency in naïve B6 controls (figure A). Conversely, Balb/c iNKT cells in both the donor and the host situation exhibited skewing toward an NKT1 lineage profile and away from the NKT2 lineage bias seen in naïve Balb/c controls (figure B). Furthermore, the expression of the H-2d MHC class I-reactive Ly49A receptor by Balb/c iNKT cells strongly correlates with the NKT1 lineage fate in control animals. However, both donor and host Balb/c cells demonstrated reduced correlation between Ly49A expression and NKT1 lineage fate indicating that the presence of H-2b expressing B6 cells diminished the ability of H-2d -reactive Ly49A to dictate lineage fate decisions.This study uniquely demonstrates the potential for cell-extrinsic signals in guiding iNKT cell lineage fate in an asymmetric fashion. Specifically, we find that: 1) the B6 iNKT lineage profile is intrinsically determined and unaffected by exposure to allogeneic Balb/c cells during development; 2) the Balb/c iNKT cell lineage profile is extrinsically determined and dominantly skewed toward an NKT1 lineage by exposure to even small numbers of B6 cells during development; and 3) the exposure to B6 cells overrides the contribution of Ly49A to developmental decisions made by Balb/c iNKT cells. Future studies will explore the regulatory interactions that govern allospecific iNKT cell lineage fate decisions and the resulting impact on the pro-inflammatory or immunoregulatory function of iNKT cells in clinically-relevant models. [Display omitted] DisclosuresNo relevant conflicts of interest to declare.