ABSTRACT
Cellular senescence is a cell fate triggered in response to stress and is characterized by stable cell-cycle arrest and a hypersecretory state. It has diverse biological roles, ranging from tissue repair to chronic disease. The development of new tools to study senescence in vivo has paved the way for uncovering its physiological and pathological roles and testing senescent cells as a therapeutic target. However, the lack of specific and broadly applicable markers makes it difficult to identify and characterize senescent cells in tissues and living organisms. To address this, we provide practical guidelines called "minimum information for cellular senescence experimentation in vivo" (MICSE). It presents an overview of senescence markers in rodent tissues, transgenic models, non-mammalian systems, human tissues, and tumors and their use in the identification and specification of senescent cells. These guidelines provide a uniform, state-of-the-art, and accessible toolset to improve our understanding of cellular senescence in vivo.
Subject(s)
Cellular Senescence , Humans , Animals , Biomarkers/metabolism , Guidelines as Topic , Neoplasms/pathologyABSTRACT
Expression of the transcription factors OCT4, SOX2, KLF4, and cMYC (OSKM) reprograms somatic cells into induced pluripotent stem cells (iPSCs). Reprogramming is a slow and inefficient process, suggesting the presence of safeguarding mechanisms that counteract cell fate conversion. One such mechanism is senescence. To identify modulators of reprogramming-induced senescence, we performed a genome-wide shRNA screen in primary human fibroblasts expressing OSKM. In the screen, we identified novel mediators of OSKM-induced senescence and validated previously implicated genes such as CDKN1A We developed an innovative approach that integrates single-cell RNA sequencing (scRNA-seq) with the shRNA screen to investigate the mechanism of action of the identified candidates. Our data unveiled regulation of senescence as a novel way by which mechanistic target of rapamycin (mTOR) influences reprogramming. On one hand, mTOR inhibition blunts the induction of cyclin-dependent kinase (CDK) inhibitors (CDKIs), including p16INK4a, p21CIP1, and p15INK4b, preventing OSKM-induced senescence. On the other hand, inhibition of mTOR blunts the senescence-associated secretory phenotype (SASP), which itself favors reprogramming. These contrasting actions contribute to explain the complex effect that mTOR has on reprogramming. Overall, our study highlights the advantage of combining functional screens with scRNA-seq to accelerate the discovery of pathways controlling complex phenotypes.
Subject(s)
Cellular Reprogramming , Cellular Senescence , Gene Expression Profiling , RNA, Small Interfering , Sequence Analysis, RNA , TOR Serine-Threonine Kinases/physiology , Transcription Factors/metabolism , Animals , Cells, Cultured , Cyclin-Dependent Kinase Inhibitor p21/metabolism , Fibroblasts/cytology , Fibroblasts/metabolism , Humans , Kruppel-Like Factor 4 , Mice , Single-Cell Analysis , TOR Serine-Threonine Kinases/antagonists & inhibitorsABSTRACT
DNA is strictly compartmentalized within the nucleus to prevent autoimmunity; despite this, cyclic GMP-AMP synthase (cGAS), a cytosolic sensor of double-stranded DNA, is activated in autoinflammatory disorders and by DNA damage. Precisely how cellular DNA gains access to the cytoplasm remains to be determined. Here, we report that cGAS localizes to micronuclei arising from genome instability in a mouse model of monogenic autoinflammation, after exogenous DNA damage and spontaneously in human cancer cells. Such micronuclei occur after mis-segregation of DNA during cell division and consist of chromatin surrounded by its own nuclear membrane. Breakdown of the micronuclear envelope, a process associated with chromothripsis, leads to rapid accumulation of cGAS, providing a mechanism by which self-DNA becomes exposed to the cytosol. cGAS is activated by chromatin, and consistent with a mitotic origin, micronuclei formation and the proinflammatory response following DNA damage are cell-cycle dependent. By combining live-cell laser microdissection with single cell transcriptomics, we establish that interferon-stimulated gene expression is induced in micronucleated cells. We therefore conclude that micronuclei represent an important source of immunostimulatory DNA. As micronuclei formed from lagging chromosomes also activate this pathway, recognition of micronuclei by cGAS may act as a cell-intrinsic immune surveillance mechanism that detects a range of neoplasia-inducing processes.
Subject(s)
Genomic Instability/immunology , Immunity, Innate/genetics , Micronuclei, Chromosome-Defective , Nucleotidyltransferases/metabolism , Animals , Cell Cycle , Cell Line, Tumor , Chromatin/metabolism , Chromothripsis , Cytoplasm/enzymology , Cytoplasm/genetics , DNA/metabolism , DNA Damage , Female , Genomic Instability/genetics , Humans , Inflammation/enzymology , Inflammation/genetics , Lasers , Male , Mice , Microdissection , Mitosis , Nuclear Envelope/metabolism , Nucleotidyltransferases/genetics , Single-Cell Analysis , TranscriptomeABSTRACT
Senescence is a cellular stress response triggered by diverse stressors, including oncogene activation, where it serves as a bona-fide tumour suppressor mechanism. Senescence can be transmitted to neighbouring cells, known as paracrine secondary senescence. Secondary senescence was initially described as a paracrine mechanism, but recent evidence suggests a more complex scenario involving juxtacrine communication between cells. In addition, single-cell studies described differences between primary and secondary senescent end-points, which have thus far not been considered functionally distinct. Here we discuss emerging concepts in senescence transmission and heterogeneity in primary and secondary senescence on a cellular and organ level.
Subject(s)
Cellular Senescence/physiology , Oncogenes/genetics , Animals , CCAAT-Enhancer-Binding Protein-beta/metabolism , Humans , Jagged-1 Protein/metabolism , Paracrine Communication , Receptors, Notch/metabolism , Signal Transduction , Transforming Growth Factor beta/metabolismABSTRACT
Ageing is a major risk factor for the development of cardiovascular disease (CVD) and cancer. Whilst the cumulative effect of exposure to conventional cardiovascular risk factors is important, recent evidence highlights clonal haematopoiesis of indeterminant potential (CHIP) as a further key risk factor. CHIP reflects the accumulation of somatic, potentially pro-leukaemic gene mutations within haematopoietic stem cells over time. The most common mutations associated with CHIP and CVD occur in genes that also play central roles in the regulation of inflammation. While CHIP carriers have a low risk of haematological malignant transformation (<1% per year), their relative risk of mortality is increased by 40% and this reflects an excess of cardiovascular events. Evidence linking CHIP, inflammation and atherosclerotic disease has recently become better defined. However, there is a paucity of information about the role of CHIP in the development and progression of heart failure, particularly heart failure with preserved ejection fraction (HFpEF). While systemic inflammation plays a role in the pathophysiology of both heart failure with reduced and preserved ejection fraction (EF), it may be of greater relevance in the pathophysiology of HFpEF, which is also strongly associated with ageing. This review describes CHIP and its pathogenetic links with ageing, inflammation and CVD, while providing insight into its putative role in HFpEF.
Subject(s)
Cardiovascular Diseases , Clonal Hematopoiesis , Heart Failure , Inflammation , Aging , Humans , Risk Factors , Stroke VolumeABSTRACT
BACKGROUND: Little is known about the roles of myeloid cell subsets in kidney injury and in the limited ability of the organ to repair itself. Characterizing these cells based only on surface markers using flow cytometry might not provide a full phenotypic picture. Defining these cells at the single-cell, transcriptomic level could reveal myeloid heterogeneity in the progression and regression of kidney disease. METHODS: Integrated droplet- and plate-based single-cell RNA sequencing were used in the murine, reversible, unilateral ureteric obstruction model to dissect the transcriptomic landscape at the single-cell level during renal injury and the resolution of fibrosis. Paired blood exchange tracked the fate of monocytes recruited to the injured kidney. RESULTS: A single-cell atlas of the kidney generated using transcriptomics revealed marked changes in the proportion and gene expression of renal cell types during injury and repair. Conventional flow cytometry markers would not have identified the 12 myeloid cell subsets. Monocytes recruited to the kidney early after injury rapidly adopt a proinflammatory, profibrotic phenotype that expresses Arg1, before transitioning to become Ccr2+ macrophages that accumulate in late injury. Conversely, a novel Mmp12+ macrophage subset acts during repair. CONCLUSIONS: Complementary technologies identified novel myeloid subtypes, based on transcriptomics in single cells, that represent therapeutic targets to inhibit progression or promote regression of kidney disease.
Subject(s)
Kidney Diseases/etiology , Kidney Diseases/pathology , Myeloid Cells/physiology , Animals , Disease Models, Animal , Disease Progression , Kidney Diseases/metabolism , Macrophages/physiology , Male , Mice , Mice, Inbred C57BL , Sequence Analysis, RNA , Single-Cell Analysis , Ureteral Obstruction/etiologyABSTRACT
Senescence is a stress-responsive form of stable cell cycle exit. Senescent cells have a distinct gene expression profile, which is often accompanied by the spatial redistribution of heterochromatin into senescence-associated heterochromatic foci (SAHFs). Studying a key component of the nuclear lamina lamin B1 (LMNB1), we report dynamic alterations in its genomic profile and their implications for SAHF formation and gene regulation during senescence. Genome-wide mapping reveals that LMNB1 is depleted during senescence, preferentially from the central regions of lamina-associated domains (LADs), which are enriched for Lys9 trimethylation on histone H3 (H3K9me3). LMNB1 knockdown facilitates the spatial relocalization of perinuclear H3K9me3-positive heterochromatin, thus promoting SAHF formation, which could be inhibited by ectopic LMNB1 expression. Furthermore, despite the global reduction in LMNB1 protein levels, LMNB1 binding increases during senescence in a small subset of gene-rich regions where H3K27me3 also increases and gene expression becomes repressed. These results suggest that LMNB1 may contribute to senescence in at least two ways due to its uneven genome-wide redistribution: first, through the spatial reorganization of chromatin and, second, through gene repression.
Subject(s)
Cellular Senescence/genetics , Chromatin Assembly and Disassembly/genetics , Heterochromatin/metabolism , Lamin Type B/metabolism , Cell Line , Cell Nucleus/metabolism , Cells, Cultured , Gene Expression Regulation , Heterochromatin/chemistry , Histones/metabolism , Lamin Type B/genetics , Protein Binding , Protein Structure, TertiaryABSTRACT
Single-cell RNA-seq enables the quantitative characterization of cell types based on global transcriptome profiles. We present single-cell consensus clustering (SC3), a user-friendly tool for unsupervised clustering, which achieves high accuracy and robustness by combining multiple clustering solutions through a consensus approach (http://bioconductor.org/packages/SC3). We demonstrate that SC3 is capable of identifying subclones from the transcriptomes of neoplastic cells collected from patients.
Subject(s)
Gene Expression Profiling/methods , High-Throughput Nucleotide Sequencing/methods , Sequence Analysis, RNA/methods , Single-Cell Analysis/methods , Cluster Analysis , Datasets as Topic , Hematopoietic Stem Cells/cytology , Humans , Support Vector MachineABSTRACT
Senescence is a tumour suppressor mechanism which is cell-intrinsically activated in the context of cellular stress. Senescence can further be propagated to neighbouring cells, a process called secondary senescence induction. Secondary senescence was initially shown as a paracrine response to the secretion of cytokines from primary senescent cells. More recently, juxtacrine Notch signalling has been implicated in mediating secondary senescence induction. Primary and secondary senescent induction results in distinct transcriptional outcomes. In addition, cell type and the stimulus in which senescence is induced can lead to variations in the phenotype of the senescence response. It is unclear whether heterogeneous senescent end-points are associated with distinct cellular function in situ, presenting functional heterogeneity. Thus, understanding senescence heterogeneity could prove to be important when devising ways of targeting senescent cells by senolytics, senostatics or senogenics. In this review, we discuss a role for functional heterogeneity in senescence in tissue- and cell-type specific manners, highlighting potential differences in senescence outcomes of primary and secondary senescence.
Subject(s)
Cellular Senescence , Receptors, Notch/metabolism , Animals , Cytokines/metabolism , Diploidy , Fibroblasts/metabolism , Fibrosis , Humans , Insulin-Secreting Cells/metabolism , Kidney/cytology , Mice , Pancreas/cytology , Phenotype , Signal Transduction , Skin/cytology , Wound HealingABSTRACT
Cell-based therapeutics, such as in vitro manufactured red blood cells (mRBCs), are different to traditional biopharmaceutical products (the final product being the cells themselves as opposed to biological molecules such as proteins) and that presents a challenge of developing new robust and economically feasible manufacturing processes, especially for sample purification. Current purification technologies have limited throughput, rely on expensive fluorescent or magnetic immunolabeling with a significant (up to 70%) cell loss and quality impairment. To address this challenge, previously characterized mechanical properties of umbilical cord blood CD34+ cells undergoing in vitro erythropoiesis were used to develop an mRBC purification strategy. The approach consists of two main stages: (a) a microfluidic separation using inertial focusing for deformability-based sorting of enucleated cells (mRBC) from nuclei and nucleated cells resulting in 70% purity and (b) membrane filtration to enhance the purity to 99%. Herein, we propose a new route for high-throughput (processing millions of cells/min and mls of medium/min) purification process for mRBC, leading to high mRBC purity while maintaining cell integrity and no alterations in their global gene expression profile. Further adaption of this separation approach offers a potential route for processing of a wide range of cellular products.
Subject(s)
Cell Separation/instrumentation , Erythrocytes/cytology , Filtration/instrumentation , Microfluidic Analytical Techniques/instrumentation , Stem Cells/cytology , Cell Line , Equipment Design , HumansABSTRACT
The expansion of repressive epigenetic marks has been implicated in heterochromatin formation during embryonic development, but the general applicability of this mechanism is unclear. Here we show that nuclear rearrangement of repressive histone marks H3K9me3 and H3K27me3 into nonoverlapping structural layers characterizes senescence-associated heterochromatic foci (SAHF) formation in human fibroblasts. However, the global landscape of these repressive marks remains unchanged upon SAHF formation, suggesting that in somatic cells, heterochromatin can be formed through the spatial repositioning of pre-existing repressively marked histones. This model is reinforced by the correlation of presenescent replication timing with both the subsequent layered structure of SAHFs and the global landscape of the repressive marks, allowing us to integrate microscopic and genomic information. Furthermore, modulation of SAHF structure does not affect the occupancy of these repressive marks, nor vice versa. These experiments reveal that high-order heterochromatin formation and epigenetic remodeling of the genome can be discrete events.
Subject(s)
Chromatin/chemistry , Heterochromatin/chemistry , Histones/metabolism , Bromodeoxyuridine/pharmacology , Cellular Senescence , Chromosomes/ultrastructure , Epigenesis, Genetic , Fibroblasts/cytology , Gene Expression Regulation, Developmental , Gene Silencing , Genome , Genome-Wide Association Study , Histones/chemistry , Humans , Laser Scanning Cytometry/methods , Microscopy, Fluorescence/methodsABSTRACT
DNA methylation plays a critical role in the regulation and maintenance of cell-type specific transcriptional programs. Targeted epigenome editing is an emerging technology to specifically regulate cellular gene expression in order to modulate cell phenotypes or dissect the epigenetic mechanisms involved in their control. In this work, we employed a DNA methyltransferase Dnmt3a-Dnmt3L construct fused to the nuclease-inactivated dCas9 programmable targeting domain to introduce DNA methylation into the human genome specifically at the EpCAM, CXCR4 and TFRC gene promoters. We show that targeting of these loci with single gRNAs leads to efficient and widespread methylation of the promoters. Multiplexing of several guide RNAs does not increase the efficiency of methylation. Peaks of targeted methylation were observed around 25 bp upstream and 40 bp downstream of the PAM site, while 20-30 bp of the binding site itself are protected against methylation. Potent methylation is dependent on the multimerization of Dnmt3a/Dnmt3L complexes on the DNA. Furthermore, the introduced methylation causes transcriptional repression of the targeted genes. These new programmable epigenetic editors allow unprecedented control of the DNA methylation status in cells and will lead to further advances in the understanding of epigenetic signaling.
Subject(s)
DNA (Cytosine-5-)-Methyltransferases/metabolism , DNA Methylation , DNA/genetics , DNA/metabolism , Endonucleases/metabolism , Animals , Cell Line, Tumor , Cluster Analysis , CpG Islands , DNA (Cytosine-5-)-Methyltransferases/chemistry , DNA (Cytosine-5-)-Methyltransferases/genetics , Endonucleases/genetics , Epigenesis, Genetic , Epigenomics/methods , Gene Expression Regulation , High-Throughput Nucleotide Sequencing , Humans , Mice , Models, Biological , Promoter Regions, Genetic , Recombinant Fusion Proteins/genetics , Recombinant Fusion Proteins/metabolismABSTRACT
The downstream functions of the DNA binding tumor suppressor p53 vary depending on the cellular context, and persistent p53 activation has recently been implicated in tumor suppression and senescence. However, genome-wide information about p53-target gene regulation has been derived mostly from acute genotoxic conditions. Using ChIP-seq and expression data, we have found distinct p53 binding profiles between acutely activated (through DNA damage) and chronically activated (in senescent or pro-apoptotic conditions) p53. Compared to the classical 'acute' p53 binding profile, 'chronic' p53 peaks were closely associated with CpG-islands. Furthermore, the chronic CpG-island binding of p53 conferred distinct expression patterns between senescent and pro-apoptotic conditions. Using the p53 targets seen in the chronic conditions together with external high-throughput datasets, we have built p53 networks that revealed extensive self-regulatory 'p53 hubs' where p53 and many p53 targets can physically interact with each other. Integrating these results with public clinical datasets identified the cancer-associated lipogenic enzyme, SCD, which we found to be directly repressed by p53 through the CpG-island promoter, providing a mechanistic link between p53 and the 'lipogenic phenotype', a hallmark of cancer. Our data reveal distinct phenotype associations of chronic p53 targets that underlie specific gene regulatory mechanisms.
Subject(s)
DNA Methylation/genetics , DNA-Binding Proteins/genetics , Protein Interaction Maps/genetics , Tumor Suppressor Protein p53/genetics , Aging/genetics , Apoptosis/genetics , Cell Line , CpG Islands/genetics , DNA Damage/genetics , DNA-Binding Proteins/metabolism , Gene Expression Regulation , Genes, Tumor Suppressor , Humans , Phenotype , Stearoyl-CoA Desaturase/genetics , Stearoyl-CoA Desaturase/metabolism , Tumor Suppressor Protein p53/metabolismABSTRACT
In multicellular organisms, developmental changes to replication timing occur in 400-800 kb domains across half the genome. While examples of epigenetic control of replication timing have been described, a role for DNA sequence in mammalian replication-timing regulation has not been substantiated. To assess the role of DNA sequences in directing developmental changes to replication timing, we profiled replication timing in mice carrying a genetically rearranged Human Chromosome 21 (Hsa21). In two distinct mouse cell types, Hsa21 sequences maintained human-specific replication timing, except at points of Hsa21 rearrangement. Changes in replication timing at rearrangements extended up to 900 kb and consistently reconciled with the wild-type replication pattern at developmental boundaries of replication-timing domains. Our results are consistent with DNA sequence-driven regulation of Hsa21 replication timing during development and provide evidence that mammalian chromosomes consist of multiple independent units of replication-timing regulation.
Subject(s)
Chromosomes, Human, Pair 21/genetics , DNA Replication , Gene Expression Regulation , Gene Rearrangement , Mice/genetics , Animals , Cell Line , Female , Humans , Male , Mice, Inbred C57BL , Species SpecificityABSTRACT
DNA methylation rates have previously been found to broadly correlate with maximum lifespan in mammals, yet no precise relationship has been observed. We developed a statistically robust framework to compare methylation rates at conserved age-related sites across mammals. We found that methylation rates negatively scale with maximum lifespan in both blood and skin. The emergence of explicit scaling suggests that methylation rates are, or are linked to, an evolutionary constraint on maximum lifespan acting across diverse mammalian lineages.
Subject(s)
DNA Methylation , Longevity , Animals , Longevity/genetics , DNA Methylation/genetics , Mammals/genetics , Biological EvolutionABSTRACT
Cellular senescence is a cell surveillance mechanism that arrests the cell cycle in damaged cells. The senescent phenotype can spread from cell to cell through paracrine and juxtacrine signalling, but the dynamics of this process are not well understood. Although senescent cells are important in ageing, wound healing and cancer, it is unclear how the spread of senescence is contained in senescent lesions. In the absence of the immune system, senescence could theoretically spread infinitely from one cell to another, but this contradicts experimental evidence. To investigate this issue, we developed both a minimal mathematical model and a stochastic simulation of senescence spread. Our results suggest that differences in the number of signalling molecules secreted between subtypes of senescent cells can limit the spread of senescence. We found that dynamic, time-dependent paracrine signalling prevents the uncontrolled spread of senescence, and we demonstrate how model parameters can be determined using Bayesian inference in a proposed experiment.
Subject(s)
Cellular Senescence , Neoplasms , Humans , Bayes Theorem , Cellular Senescence/genetics , Neoplasms/pathology , PhenotypeABSTRACT
Recent studies suggest that epigenetic rejuvenation can be achieved using drugs that mimic calorie restriction and techniques such as reprogramming-induced rejuvenation. To effectively test rejuvenation in vivo, mouse models are the safest alternative. However, we have found that the recent epigenetic clocks developed for mouse reduced-representation bisulphite sequencing (RRBS) data have significantly poor performance when applied to external datasets. We show that the sites captured and the coverage of key CpGs required for age prediction vary greatly between datasets, which likely contributes to the lack of transferability in RRBS clocks. To mitigate these coverage issues in RRBS-based age prediction, we present two novel design strategies that use average methylation over large regions rather than individual CpGs, whereby regions are defined by sliding windows (e.g. 5 kb), or density-based clustering of CpGs. We observe improved correlation and error in our regional blood clocks (RegBCs) compared to published individual-CpG-based techniques when applied to external datasets. The RegBCs are also more robust when applied to low coverage data and detect a negative age acceleration in mice undergoing calorie restriction. Our RegBCs offer a proof of principle that age prediction of RRBS datasets can be improved by accounting for multiple CpGs over a region, which negates the lack of read depth currently hindering individual-CpG-based approaches.
Subject(s)
DNA Methylation , Epigenomics , Mice , Animals , DNA Methylation/genetics , CpG Islands/genetics , Sequence Analysis, DNA/methods , Epigenesis, GeneticABSTRACT
The accumulation of senescent cells in the tumor microenvironment can drive tumorigenesis in a paracrine manner through the senescence-associated secretory phenotype (SASP). Using a new p16-FDR mouse line, we show that macrophages and endothelial cells are the predominant senescent cell types in murine KRAS-driven lung tumors. Through single cell transcriptomics, we identify a population of tumor-associated macrophages that express a unique array of pro-tumorigenic SASP factors and surface proteins and are also present in normal aged lungs. Genetic or senolytic ablation of senescent cells, or macrophage depletion, result in a significant decrease in tumor burden and increased survival in KRAS-driven lung cancer models. Moreover, we reveal the presence of macrophages with senescent features in human lung pre-malignant lesions, but not in adenocarcinomas. Taken together, our results have uncovered the important role of senescent macrophages in the initiation and progression of lung cancer, highlighting potential therapeutic avenues and cancer preventative strategies.
Subject(s)
Cellular Senescence , Lung Neoplasms , Aged , Animals , Humans , Mice , Carcinogenesis/genetics , Carcinogenesis/metabolism , Cellular Senescence/genetics , Endothelial Cells , Lung Neoplasms/genetics , Lung Neoplasms/metabolism , Macrophages/metabolism , Proto-Oncogene Proteins p21(ras)/genetics , Proto-Oncogene Proteins p21(ras)/metabolism , Tumor MicroenvironmentABSTRACT
Progressive fibrosis is a feature of aging and chronic tissue injury in multiple organs, including the kidney and heart. Glioma-associated oncogene 1 expressing (Gli1+) cells are a major source of activated fibroblasts in multiple organs, but the links between injury, inflammation, and Gli1+ cell expansion and tissue fibrosis remain incompletely understood. We demonstrated that leukocyte-derived tumor necrosis factor (TNF) promoted Gli1+ cell proliferation and cardiorenal fibrosis through induction and release of Indian Hedgehog (IHH) from renal epithelial cells. Using single-cell-resolution transcriptomic analysis, we identified an "inflammatory" proximal tubular epithelial (iPT) population contributing to TNF- and nuclear factor κB (NF-κB)-induced IHH production in vivo. TNF-induced Ubiquitin D (Ubd) expression was observed in human proximal tubular cells in vitro and during murine and human renal disease and aging. Studies using pharmacological and conditional genetic ablation of TNF-induced IHH signaling revealed that IHH activated canonical Hedgehog signaling in Gli1+ cells, which led to their activation, proliferation, and fibrosis within the injured and aging kidney and heart. These changes were inhibited in mice by Ihh deletion in Pax8-expressing cells or by pharmacological blockade of TNF, NF-κB, or Gli1 signaling. Increased amounts of circulating IHH were associated with loss of renal function and higher rates of cardiovascular disease in patients with chronic kidney disease. Thus, IHH connects leukocyte activation to Gli1+ cell expansion and represents a potential target for therapies to inhibit inflammation-induced fibrosis.
Subject(s)
Hedgehog Proteins , Renal Insufficiency, Chronic , Animals , Humans , Mice , Fibrosis , Hedgehog Proteins/metabolism , Inflammation , NF-kappa B , Tumor Necrosis Factors , Zinc Finger Protein GLI1ABSTRACT
Melanocytes, the pigment-producing cells, are replenished from multiple stem cell niches in adult tissue. Although pigmentation traits are known risk factors for melanoma, we know little about melanocyte stem cell (McSC) populations other than hair follicle McSCs and lack key lineage markers with which to identify McSCs and study their function. Here we find that Tfap2b and a select set of target genes specify an McSC population at the dorsal root ganglia in zebrafish. Functionally, Tfap2b is required for only a few late-stage embryonic melanocytes, and is essential for McSC-dependent melanocyte regeneration. Fate mapping data reveal that tfap2b+ McSCs have multifate potential, and are the cells of origin for large patches of adult melanocytes, two other pigment cell types (iridophores and xanthophores), and nerve-associated cells. Hence, Tfap2b confers McSC identity in early development, distinguishing McSCs from other neural crest and pigment cell lineages, and retains multifate potential in the adult zebrafish.