Showing papers in "Nature Cell Biology in 2017"
TL;DR: It is shown that different EMT-TFs have complementary subfunctions in driving pancreatic tumour metastasis, and that Depletion of Zeb1 suppresses stemness, colonization capacity and in particular phenotypic/metabolic plasticity of tumour cells, probably causing the observed in vivo effects.
Abstract: Metastasis is the major cause of cancer-associated death. Partial activation of the epithelial-to-mesenchymal transition program (partial EMT) was considered a major driver of tumour progression from initiation to metastasis. However, the role of EMT in promoting metastasis has recently been challenged, in particular concerning effects of the Snail and Twist EMT transcription factors (EMT-TFs) in pancreatic cancer. In contrast, we show here that in the same pancreatic cancer model, driven by Pdx1-cre-mediated activation of mutant Kras and p53 (KPC model), the EMT-TF Zeb1 is a key factor for the formation of precursor lesions, invasion and notably metastasis. Depletion of Zeb1 suppresses stemness, colonization capacity and in particular phenotypic/metabolic plasticity of tumour cells, probably causing the observed in vivo effects. Accordingly, we conclude that different EMT-TFs have complementary subfunctions in driving pancreatic tumour metastasis. Therapeutic strategies should consider these potential specificities of EMT-TFs to target these factors simultaneously.
675 citations
TL;DR: Flow cytometric, transcriptomic and functional data at single-cell resolution are integrated to quantitatively map early differentiation of human HSCs towards lineage commitment and provide a basis for the understanding of haematopoietic malignancies.
Abstract: Blood formation is believed to occur through stepwise progression of haematopoietic stem cells (HSCs) following a tree-like hierarchy of oligo-, bi- and unipotent progenitors. However, this model is based on the analysis of predefined flow-sorted cell populations. Here we integrated flow cytometric, transcriptomic and functional data at single-cell resolution to quantitatively map early differentiation of human HSCs towards lineage commitment. During homeostasis, individual HSCs gradually acquire lineage biases along multiple directions without passing through discrete hierarchically organized progenitor populations. Instead, unilineage-restricted cells emerge directly from a 'continuum of low-primed undifferentiated haematopoietic stem and progenitor cells' (CLOUD-HSPCs). Distinct gene expression modules operate in a combinatorial manner to control stemness, early lineage priming and the subsequent progression into all major branches of haematopoiesis. These data reveal a continuous landscape of human steady-state haematopoiesis downstream of HSCs and provide a basis for the understanding of haematopoietic malignancies.
665 citations
TL;DR: A role for innate DNA sensing in the regulation of senescence and the SASP is defined and it is found that cyclic GMP-AMP synthase (cGAS) recognizes cytosolic chromatin fragments in senescent cells.
Abstract: Cellular senescence is triggered by various distinct stresses and characterized by a permanent cell cycle arrest. Senescent cells secrete a variety of inflammatory factors, collectively referred to as the senescence-associated secretory phenotype (SASP). The mechanism(s) underlying the regulation of the SASP remains incompletely understood. Here we define a role for innate DNA sensing in the regulation of senescence and the SASP. We find that cyclic GMP-AMP synthase (cGAS) recognizes cytosolic chromatin fragments in senescent cells. The activation of cGAS, in turn, triggers the production of SASP factors via stimulator of interferon genes (STING), thereby promoting paracrine senescence. We demonstrate that diverse stimuli of cellular senescence engage the cGAS-STING pathway in vitro and we show cGAS-dependent regulation of senescence following irradiation and oncogene activation in vivo. Our findings provide insights into the mechanisms underlying cellular senescence by establishing the cGAS-STING pathway as a crucial regulator of senescence and the SASP.
647 citations
TL;DR: How DNA repair processes, and DNA double-strand break repair in particular, are regulated during the cell cycle to optimize genomic integrity is reviewed.
Abstract: The correct duplication and transmission of genetic material to daughter cells is the primary objective of the cell division cycle. DNA replication and chromosome segregation present both challenges and opportunities for DNA repair pathways that safeguard genetic information. As a consequence, there is a profound, two-way connection between DNA repair and cell cycle control. Here, we review how DNA repair processes, and DNA double-strand break repair in particular, are regulated during the cell cycle to optimize genomic integrity.
524 citations
TL;DR: The findings show that a mechanically active heterophilic adhesion between CAFs and cancer cells enables cooperative tumour invasion.
Abstract: Cancer-associated fibroblasts (CAFs) promote tumour invasion and metastasis. We show that CAFs exert a physical force on cancer cells that enables their collective invasion. Force transmission is mediated by a heterophilic adhesion involving N-cadherin at the CAF membrane and E-cadherin at the cancer cell membrane. This adhesion is mechanically active; when subjected to force it triggers β-catenin recruitment and adhesion reinforcement dependent on α-catenin/vinculin interaction. Impairment of E-cadherin/N-cadherin adhesion abrogates the ability of CAFs to guide collective cell migration and blocks cancer cell invasion. N-cadherin also mediates repolarization of the CAFs away from the cancer cells. In parallel, nectins and afadin are recruited to the cancer cell/CAF interface and CAF repolarization is afadin dependent. Heterotypic junctions between CAFs and cancer cells are observed in patient-derived material. Together, our findings show that a mechanically active heterophilic adhesion between CAFs and cancer cells enables cooperative tumour invasion.
524 citations
TL;DR: Generation from hPSCs of lung bud organoids that contain mesoderm and pulmonary endoderm develop into branching airway and early alveolar structures after xenotransplantation and in Matrigel 3D culture and may provide a useful tool to model lung disease.
Abstract: Recapitulation of lung development from human pluripotent stem cells (hPSCs) in three dimensions (3D) would allow deeper insight into human development, as well as the development of innovative strategies for disease modelling, drug discovery and regenerative medicine. We report here the generation from hPSCs of lung bud organoids (LBOs) that contain mesoderm and pulmonary endoderm and develop into branching airway and early alveolar structures after xenotransplantation and in Matrigel 3D culture. Expression analysis and structural features indicated that the branching structures reached the second trimester of human gestation. Infection in vitro with respiratory syncytial virus, which causes small airway obstruction and bronchiolitis in infants, led to swelling, detachment and shedding of infected cells into the organoid lumens, similar to what has been observed in human lungs. Introduction of mutation in HPS1, which causes an early-onset form of intractable pulmonary fibrosis, led to accumulation of extracellular matrix and mesenchymal cells, suggesting the potential use of this model to recapitulate fibrotic lung disease in vitro. LBOs therefore recapitulate lung development and may provide a useful tool to model lung disease.
421 citations
TL;DR: These organoids expand long-term, are genetically stable and differentiate following treatment with reproductive hormones, and provide a foundation to study common diseases, such as endometriosis and endometrial cancer, as well as the physiology of early gestation.
Abstract: Turco et al. derive long-term genetically stable organoids from normal endometrium and the decidua that recapitulate characteristics of in vivo uterine glands, respond to hormones and differentiate into secretory and ciliated endometrial cells.
404 citations
TL;DR: A fully defined, synthetic hydrogel based on a four-armed, maleimide-terminated poly(ethylene glycol) macromer that supports robust and highly reproducible in vitro growth and expansion of HIOs, such that three-dimensional structures are never embedded in tumour-derived ECM is developed.
Abstract: In vitro differentiation of human intestinal organoids (HIOs) from pluripotent stem cells is an unparalleled system for creating complex, multicellular three-dimensional structures capable of giving rise to tissue analogous to native human tissue. Current methods for generating HIOs rely on growth in an undefined tumour-derived extracellular matrix (ECM), which severely limits the use of organoid technologies for regenerative and translational medicine. Here, we developed a fully defined, synthetic hydrogel based on a four-armed, maleimide-terminated poly(ethylene glycol) macromer that supports robust and highly reproducible in vitro growth and expansion of HIOs, such that three-dimensional structures are never embedded in tumour-derived ECM. We also demonstrate that the hydrogel serves as an injection vehicle that can be delivered into injured intestinal mucosa resulting in HIO engraftment and improved colonic wound repair. Together, these studies show proof-of-concept that HIOs may be used therapeutically to treat intestinal injury.
369 citations
TL;DR: As mechanics is increasingly revealed to play a fundamental role in cell function it is envisage that tools to quantify physical forces may soon become widely applied in life-sciences laboratories.
Abstract: Cells exert, sense, and respond to physical forces through an astounding diversity of mechanisms. Here we review recently developed tools to quantify the forces generated by cells. We first review technologies based on sensors of known or assumed mechanical properties, and discuss their applicability and limitations. We then proceed to draw an analogy between these human-made sensors and force sensing in the cell. As mechanics is increasingly revealed to play a fundamental role in cell function we envisage that tools to quantify physical forces may soon become widely applied in life-sciences laboratories.
363 citations
TL;DR: The biochemical and genetic principles of how metabolism can influence chromatin biology and epigenetics are described, the functional roles of this interplay in developmental and cancer biology are discussed, and future directions in this rapidly emerging area are presented.
Abstract: The substrates used to modify nucleic acids and chromatin are affected by nutrient availability and the activity of metabolic pathways. Thus, cellular metabolism constitutes a fundamental component of chromatin status and thereby of genome regulation. Here we describe the biochemical and genetic principles of how metabolism can influence chromatin biology and epigenetics, discuss the functional roles of this interplay in developmental and cancer biology, and present future directions in this rapidly emerging area.
353 citations
TL;DR: It is shown that the actin filament length regulators CFL1, CAPZB and DIAPH1 regulate mitotic cortex thickness and that both increasing and decreasing thickness decreases tension in mitosis.
Abstract: Animal cell shape is largely determined by the cortex, a thin actin network underlying the plasma membrane in which myosin-driven stresses generate contractile tension Tension gradients result in local contractions and drive cell deformations Previous cortical tension regulation studies have focused on myosin motors Here, we show that cortical actin network architecture is equally important First, we observe that actin cortex thickness and tension are inversely correlated during cell-cycle progression We then show that the actin filament length regulators CFL1, CAPZB and DIAPH1 regulate mitotic cortex thickness and find that both increasing and decreasing thickness decreases tension in mitosis This suggests that the mitotic cortex is poised close to a tension maximum Finally, using a computational model, we identify a physical mechanism by which maximum tension is achieved at intermediate actin filament lengths Our results indicate that actin network architecture, alongside myosin activity, is key to cell surface tension regulation
TL;DR: It is discovered that bone marrow adipocytes synthesize SCF, and deletion using Adipoq-Cre/ER inhibited haematopoietic regeneration after irradiation or 5-fluorouracil treatment, depleting HSCs and reducing mouse survival.
Abstract: Zhou et al. demonstrate that bone marrow adipocytes, but not intraperitoneal adipocytes, express high levels of stem cell factor (SCF), which is essential for the regeneration of haematopoietic stem cells and haematopoiesis after irradiation.
TL;DR: It is shown that the effects of cytokines regulating HSC functions are dependent on the producing cell sources, and distinct contributions of cytokine derived from perivascular cells in separate vascular niches to HSC maintenance are uncovered.
Abstract: Arterioles and sinusoids of the bone marrow (BM) are accompanied by stromal cells that express nerve/glial antigen 2 (NG2) and leptin receptor (LepR), and constitute specialized niches that regulate quiescence and proliferation of haematopoietic stem cells (HSCs). However, how niche cells differentially regulate HSC functions remains unknown. Here, we show that the effects of cytokines regulating HSC functions are dependent on the producing cell sources. Deletion of chemokine C-X-C motif ligand 12 (Cxcl12) or stem cell factor (Scf) from all perivascular cells marked by nestin-GFP dramatically depleted BM HSCs. Selective Cxcl12 deletion from arteriolar NG2+ cells, but not from sinusoidal LepR+ cells, caused HSC reductions and altered HSC localization in BM. By contrast, deletion of Scf in LepR+ cells, but not NG2+ cells, led to reductions in BM HSC numbers. These results uncover distinct contributions of cytokines derived from perivascular cells in separate vascular niches to HSC maintenance.
TL;DR: FRET-based assays that report on the lateral interactions between protofilaments are developed and find that αK40 acetylation directly weakens inter-protofilament interactions, which protects long-lived microtubules from mechanical ageing and enhances flexibility and resilience against repeated mechanical stresses.
Abstract: Long-lived microtubules endow the eukaryotic cell with long-range transport abilities. While long-lived microtubules are acetylated on Lys40 of α-tubulin (αK40), acetylation takes place after stabilization and does not protect against depolymerization. Instead, αK40 acetylation has been proposed to mechanically stabilize microtubules. Yet how modification of αK40, a residue exposed to the microtubule lumen and inaccessible to microtubule-associated proteins and motors, could affect microtubule mechanics remains an open question. Here we develop FRET-based assays that report on the lateral interactions between protofilaments and find that αK40 acetylation directly weakens inter-protofilament interactions. Congruently, αK40 acetylation affects two processes largely governed by inter-protofilament interactions, reducing the nucleation frequency and accelerating the shrinkage rate. Most relevant to the biological function of acetylation, microfluidics manipulations demonstrate that αK40 acetylation enhances flexibility and confers resilience against repeated mechanical stresses. Thus, unlike deacetylated microtubules that accumulate damage when subjected to repeated stresses, long-lived microtubules are protected from mechanical ageing through their acquisition of αK40 acetylation. In contrast to other tubulin post-translational modifications that act through microtubule-associated proteins, motors and severing enzymes, intraluminal acetylation directly tunes the compliance and resilience of microtubules.
TL;DR: It is proposed that DDR signalling sites, in addition to sharing a common pool of proteins, individually host a unique set of site-specific RNAs necessary for DDR activation.
Abstract: The DNA damage response (DDR) preserves genomic integrity. Small non-coding RNAs termed DDRNAs are generated at DNA double-strand breaks (DSBs) and are critical for DDR activation. Here we show that active DDRNAs specifically localize to their damaged homologous genomic sites in a transcription-dependent manner. Following DNA damage, RNA polymerase II (RNAPII) binds to the MRE11-RAD50-NBS1 complex, is recruited to DSBs and synthesizes damage-induced long non-coding RNAs (dilncRNAs) from and towards DNA ends. DilncRNAs act both as DDRNA precursors and by recruiting DDRNAs through RNA-RNA pairing. Together, dilncRNAs and DDRNAs fuel DDR focus formation and associate with 53BP1. Accordingly, inhibition of RNAPII prevents DDRNA recruitment, DDR activation and DNA repair. Antisense oligonucleotides matching dilncRNAs and DDRNAs impair site-specific DDR focus formation and DNA repair. We propose that DDR signalling sites, in addition to sharing a common pool of proteins, individually host a unique set of site-specific RNAs necessary for DDR activation.
TL;DR: Genetic experiments in postnatal mice show that the level of active Notch signalling is more important than the direct Dll4-mediated cell–cell communication between endothelial cells in controlling Notch-dependent vessel growth.
Abstract: Endothelial sprouting and proliferation are tightly coordinated processes mediating the formation of new blood vessels during physiological and pathological angiogenesis. Endothelial tip cells lead sprouts and are thought to suppress tip-like behaviour in adjacent stalk endothelial cells by activating Notch. Here, we show with genetic experiments in postnatal mice that the level of active Notch signalling is more important than the direct Dll4-mediated cell-cell communication between endothelial cells. We identify endothelial expression of VEGF-A and of the chemokine receptor CXCR4 as key processes controlling Notch-dependent vessel growth. Surprisingly, genetic experiments targeting endothelial tip cells in vivo reveal that they retain their function without Dll4 and are also not replaced by adjacent, Dll4-positive cells. Instead, activation of Notch directs tip-derived endothelial cells into developing arteries and thereby establishes that Dll4-Notch signalling couples sprouting angiogenesis and artery formation.
TL;DR: It is shown that L-OPA1 and cardiolipin (CL) cooperate in heterotypic mitochondrial IM fusion, and multiple OPA1 functions are modulated by local CL conditions for regulation of mitochondrial morphology and quality control.
Abstract: Ban et al. show that optic atrophy 1 (OPA1) and cardiolipin mediate mitochondrial fusion. In contrast, a homotypic trans-OPA1 interaction independent of cardiolipin mediates membrane tethering to form mitochondrial cristae.
TL;DR: It is shown that EZH2 localizes at stalled forks where it methylates Lys27 on histone 3 (H3K27me3), mediating recruitment of the MUS81 nuclease, which promotes PARPi resistance in BRCA2-deficient cells.
Abstract: The emergence of resistance to poly-ADP-ribose polymerase inhibitors (PARPi) poses a threat to the treatment of BRCA1 and BRCA2 (BRCA1/2)-deficient tumours. Stabilization of stalled DNA replication forks is a recently identified PARPi-resistance mechanism that promotes genomic stability in BRCA1/2-deficient cancers. Dissecting the molecular pathways controlling genomic stability at stalled forks is critical. Here we show that EZH2 localizes at stalled forks where it methylates Lys27 on histone 3 (H3K27me3), mediating recruitment of the MUS81 nuclease. Low EZH2 levels reduce H3K27 methylation, prevent MUS81 recruitment at stalled forks and cause fork stabilization. As a consequence, loss of function of the EZH2/MUS81 axis promotes PARPi resistance in BRCA2-deficient cells. Accordingly, low EZH2 or MUS81 expression levels predict chemoresistance and poor outcome in patients with BRCA2-mutated tumours. Moreover, inhibition of Ezh2 in a murine Brca2-/- breast tumour model is associated with acquired PARPi resistance. Our findings identify EZH2 as a critical regulator of genomic stability at stalled forks that couples histone modifications to nuclease recruitment. Our data identify EZH2 expression as a biomarker of BRCA2-deficient tumour response to chemotherapy.
TL;DR: It is proposed that primary tumour hypoxic microenvironments give rise to a subpopulation of dormant DTCs that evade therapy and may be the source of disease relapse and poor prognosis associated with hypoxia.
Abstract: Aguirre-Ghiso and colleagues report that hypoxia in the primary tumour microenvironment leads to upregulation of a dormancy signature in the tumour cells that persists after their dissemination to distant sites, permitting them to evade therapy.
TL;DR: PNUTs is a bifunctional RNA encoding both PNUTS mRNA and lncRNA-PNUTS, each eliciting distinct biological functions, and appears to be tightly regulated dependent on the status of hnRNP E1 and tumour context.
Abstract: The contribution of lncRNAs to tumour progression and the regulatory mechanisms driving their expression are areas of intense investigation. Here, we characterize the binding of heterogeneous nuclear ribonucleoprotein E1 (hnRNP E1) to a nucleic acid structural element located in exon 12 of PNUTS (also known as PPP1R10) pre-RNA that regulates its alternative splicing. HnRNP E1 release from this structural element, following its silencing, nucleocytoplasmic translocation or in response to TGFβ, allows alternative splicing and generates a non-coding isoform of PNUTS. Functionally the lncRNA-PNUTS serves as a competitive sponge for miR-205 during epithelial-mesenchymal transition (EMT). In mesenchymal breast tumour cells and in breast tumour samples, the expression of lncRNA-PNUTS is elevated and correlates with levels of ZEB mRNAs. Thus, PNUTS is a bifunctional RNA encoding both PNUTS mRNA and lncRNA-PNUTS, each eliciting distinct biological functions. While PNUTS mRNA is ubiquitously expressed, lncRNA-PNUTS appears to be tightly regulated dependent on the status of hnRNP E1 and tumour context.
TL;DR: The discovery of an ancient and conserved multiprotein complex that orchestrates cargo retrieval and recycling and, importantly, is biochemically and functionally distinct from the established retromer pathway is described.
Abstract: Following endocytosis into the endosomal network, integral membrane proteins undergo sorting for lysosomal degradation or are retrieved and recycled back to the cell surface. Here we describe the discovery of an ancient and conserved multiprotein complex that orchestrates cargo retrieval and recycling and, importantly, is biochemically and functionally distinct from the established retromer pathway. We have called this complex 'retriever'; it is a heterotrimer composed of DSCR3, C16orf62 and VPS29, and bears striking similarity to retromer. We establish that retriever associates with the cargo adaptor sorting nexin 17 (SNX17) and couples to CCC (CCDC93, CCDC22, COMMD) and WASH complexes to prevent lysosomal degradation and promote cell surface recycling of α5β1 integrin. Through quantitative proteomic analysis, we identify over 120 cell surface proteins, including numerous integrins, signalling receptors and solute transporters, that require SNX17-retriever to maintain their surface levels. Our identification of retriever establishes a major endosomal retrieval and recycling pathway.
TL;DR: It is demonstrated that limiting mitochondrial pyruvate metabolism is necessary and sufficient to maintain the proliferation of intestinal stem cells and to understand the role this transition from glycolysis to pyruVate oxidation plays in stem cell maintenance and differentiation.
Abstract: Most differentiated cells convert glucose to pyruvate in the cytosol through glycolysis, followed by pyruvate oxidation in the mitochondria. These processes are linked by the mitochondrial pyruvate carrier (MPC), which is required for efficient mitochondrial pyruvate uptake. In contrast, proliferative cells, including many cancer and stem cells, perform glycolysis robustly but limit fractional mitochondrial pyruvate oxidation. We sought to understand the role this transition from glycolysis to pyruvate oxidation plays in stem cell maintenance and differentiation. Loss of the MPC in Lgr5-EGFP-positive stem cells, or treatment of intestinal organoids with an MPC inhibitor, increases proliferation and expands the stem cell compartment. Similarly, genetic deletion of the MPC in Drosophila intestinal stem cells also increases proliferation, whereas MPC overexpression suppresses stem cell proliferation. These data demonstrate that limiting mitochondrial pyruvate metabolism is necessary and sufficient to maintain the proliferation of intestinal stem cells.
TL;DR: The data provide insights into the mechanistic regulation and linkage of the ROR1–HER3 and Hippo–YAP pathway in a cancer-specific context, and also imply valuable therapeutic targets for bone metastasis and possible therapy-resistant tumours.
Abstract: Li et al. show that ROR1–HER3 receptor tyrosine kinase signalling in breast cancer cells inhibits the MST1/2 Hippo pathway kinases through a lncRNA termed MAYA. The resulting activation of YAP promotes osteoclast differentiation for bone metastasis.
TL;DR: An oncofetal splicing factor is identified, MBNL3, which promotes tumorigenesis and indicates poor prognosis of hepatocellular carcinoma patients and detailed mechanistic links are demonstrated, which establish splicing factors and splicing events as potential therapeutic targets.
Abstract: Yuan et al. show that the MBNL3 splicing factor promotes alternative splicing of the lncRNA-PXN-AS1 antisense transcript of PXN, leading to the stabilization of PXN mRNA and increasing its protein levels to promote liver cancer growth.
TL;DR: It is reported that loss of the mitochondrial complex III subunit Rieske iron-sulfur protein (RISP) in fetal mouse HSCs allows them to proliferate but impairs their differentiation, resulting in anaemia and prenatal death.
Abstract: Adult and fetal haematopoietic stem cells (HSCs) display a glycolytic phenotype, which is required for maintenance of stemness; however, whether mitochondrial respiration is required to maintain HSC function is not known Here we report that loss of the mitochondrial complex III subunit Rieske iron-sulfur protein (RISP) in fetal mouse HSCs allows them to proliferate but impairs their differentiation, resulting in anaemia and prenatal death RISP-null fetal HSCs displayed impaired respiration resulting in a decreased NAD+/NADH ratio RISP-null fetal HSCs and progenitors exhibited an increase in both DNA and histone methylation associated with increases in 2-hydroxyglutarate (2HG), a metabolite known to inhibit DNA and histone demethylases RISP inactivation in adult HSCs also impaired respiration resulting in loss of quiescence concomitant with severe pancytopenia and lethality Thus, respiration is dispensable for adult or fetal HSC proliferation, but essential for fetal HSC differentiation and maintenance of adult HSC quiescence
TL;DR: It is shown that tumour-secreted DKK1 is a serological marker of breast cancer metastasis organotropism and inhibits lung metastasis and provides a rationale for new anti-metastasis approaches.
Abstract: Metastatic cancer is a systemic disease, and metastasis determinants might elicit completely different effects in various target organs. Here we show that tumour-secreted DKK1 is a serological marker of breast cancer metastasis organotropism and inhibits lung metastasis. DKK1 suppresses PTGS2-induced macrophage and neutrophil recruitment in lung metastases by antagonizing cancer cell non-canonical WNT/PCP-RAC1-JNK signalling. In the lungs, DKK1 also inhibits WNT/Ca2+-CaMKII-NF-κB signalling and suppresses LTBP1-mediated TGF-β secretion of cancer cells. In contrast, DKK1 promotes breast-to-bone metastasis by regulating canonical WNT signalling of osteoblasts. Importantly, targeting canonical WNT may not be beneficial to treatment of metastatic cancer, while combinatory therapy against JNK and TGF-β signalling effectively prevents metastasis to both the lungs and bone. Thus, DKK1 represents a class of Janus-faced molecules with dichotomous roles in organotropic metastasis, and our data provide a rationale for new anti-metastasis approaches.
TL;DR: It is found that ESCRT-III at the midbody of human cells rapidly turns over subunits with cytoplasmic pools while gradually forming larger assemblies, with broad implications for diverse cellular processes.
Abstract: The endosomal sorting complex required for transport (ESCRT)-III mediates membrane fission in fundamental cellular processes, including cytokinesis. ESCRT-III is thought to form persistent filaments that over time increase their curvature to constrict membranes. Unexpectedly, we found that ESCRT-III at the midbody of human cells rapidly turns over subunits with cytoplasmic pools while gradually forming larger assemblies. ESCRT-III turnover depended on the ATPase VPS4, which accumulated at the midbody simultaneously with ESCRT-III subunits, and was required for assembly of functional ESCRT-III structures. In vitro, the Vps2/Vps24 subunits of ESCRT-III formed side-by-side filaments with Snf7 and inhibited further polymerization, but the growth inhibition was alleviated by the addition of Vps4 and ATP. High-speed atomic force microscopy further revealed highly dynamic arrays of growing and shrinking ESCRT-III spirals in the presence of Vps4. Continuous ESCRT-III remodelling by subunit turnover might facilitate shape adaptions to variable membrane geometries, with broad implications for diverse cellular processes.
TL;DR: It is demonstrated that HFSCs utilize glycolytic metabolism and produce significantly more lactate than other cells in the epidermis, and small molecules that increase lactate production by stimulating Myc levels or inhibiting Mpc1 carrier activity and can topically induce the hair cycle are identified.
Abstract: Although normally dormant, hair follicle stem cells (HFSCs) quickly become activated to divide during a new hair cycle. The quiescence of HFSCs is known to be regulated by a number of intrinsic and extrinsic mechanisms. Here we provide several lines of evidence to demonstrate that HFSCs utilize glycolytic metabolism and produce significantly more lactate than other cells in the epidermis. Furthermore, lactate generation appears to be critical for the activation of HFSCs as deletion of lactate dehydrogenase (Ldha) prevented their activation. Conversely, genetically promoting lactate production in HFSCs through mitochondrial pyruvate carrier 1 (Mpc1) deletion accelerated their activation and the hair cycle. Finally, we identify small molecules that increase lactate production by stimulating Myc levels or inhibiting Mpc1 carrier activity and can topically induce the hair cycle. These data suggest that HFSCs maintain a metabolic state that allows them to remain dormant and yet quickly respond to appropriate proliferative stimuli.
TL;DR: It is shown by lineage tracing that Lgr5-expressing chief cells do not behave as corpus stem cells during homeostasis, but are recruited to function as stem cells to effect epithelial renewal following injury by activating Wnt signalling.
Abstract: The daily renewal of the corpus epithelium is fuelled by adult stem cells residing within tubular glands, but the identity of these stem cells remains controversial Lgr5 marks homeostatic stem cells and 'reserve' stem cells in multiple tissues Here, we report Lgr5 expression in a subpopulation of chief cells in mouse and human corpus glands Using a non-variegated Lgr5-2A-CreERT2 mouse model, we show by lineage tracing that Lgr5-expressing chief cells do not behave as corpus stem cells during homeostasis, but are recruited to function as stem cells to effect epithelial renewal following injury by activating Wnt signalling Ablation of Lgr5+ cells severely impairs epithelial homeostasis in the corpus, indicating an essential role for these Lgr5+ cells in maintaining the homeostatic stem cell pool We additionally define Lgr5+ chief cells as a major cell-of-origin of gastric cancer These findings reveal clinically relevant insights into homeostasis, repair and cancer in the corpus
TL;DR: An inducible Y centromere-selective inactivation strategy is developed by exploiting a CENP-A/histone H3 chimaera to directly examine the fate of missegregated chromosomes in otherwise diploid human cells, and initial errors in cell division can provoke further genomic instability through fragmentation of micronuclear DNAs coupled to NHEJ-mediated reassembly in the subsequent interphase.
Abstract: Ly et al. establish a method to selectively inactivate the centromere of the Y chromosome to follow chromosome shattering and micronuclei formation through several cell cycles, and suggest re-ligation of chromosome fragments is dependent on non-homologous end joining.