RESUMEN
Despite advances in defining diverse somatic mutations that cause myeloid malignancies, a significant heritable component for these cancers remains largely unexplained. Here, we perform rare variant association studies in a large population cohort to identify inherited predisposition genes for these blood cancers. CTR9, which encodes a key component of the PAF1 transcription elongation complex, is among the significant genes identified. The risk variants found in the cases cause loss of function and result in a â¼10-fold increased odds of acquiring a myeloid malignancy. Partial CTR9 loss of function expands human hematopoietic stem cells (HSCs) by increased super elongation complex-mediated transcriptional activity, which thereby increases the expression of key regulators of HSC self-renewal. By following up on insights from a human genetic study examining inherited predisposition to the myeloid malignancies, we define a previously unknown antagonistic interaction between the PAF1 and super elongation complexes. These insights could enable targeted approaches for blood cancer prevention.
Asunto(s)
Neoplasias Hematológicas , Fosfoproteínas , Elongación de la Transcripción Genética , Factores de Transcripción , Humanos , Neoplasias Hematológicas/genética , Células Madre Hematopoyéticas/metabolismo , Proteínas Nucleares/metabolismo , Factores de Transcripción/genética , Fosfoproteínas/genéticaRESUMEN
Hematopoietic stem cells (HSCs) have a number of unique physiologic adaptations that enable lifelong maintenance of blood cell production, including a highly regulated rate of protein synthesis. Yet, the precise vulnerabilities that arise from such adaptations have not been fully characterized. Here, inspired by a bone marrow failure disorder due to the loss of the histone deubiquitinase MYSM1, characterized by selectively disadvantaged HSCs, we show how reduced protein synthesis in HSCs results in increased ferroptosis. HSC maintenance can be fully rescued by blocking ferroptosis, despite no alteration in protein synthesis rates. Importantly, this selective vulnerability to ferroptosis not only underlies HSC loss in MYSM1 deficiency but also characterizes a broader liability of human HSCs. Increasing protein synthesis rates via MYSM1 overexpression makes HSCs less susceptible to ferroptosis, more broadly illustrating the selective vulnerabilities that arise in somatic stem cell populations as a result of physiologic adaptations.
Asunto(s)
Ferroptosis , Células Madre Hematopoyéticas , Humanos , Endopeptidasas/metabolismo , Hematopoyesis , Células Madre Hematopoyéticas/metabolismo , Transactivadores/metabolismo , Proteasas Ubiquitina-Específicas/metabolismoRESUMEN
Cellular lineage histories and their molecular states encode fundamental principles of tissue development and homeostasis. Current lineage-recording mouse models have insufficient barcode diversity and single-cell lineage coverage for profiling tissues composed of millions of cells. Here, we developed DARLIN, an inducible Cas9 barcoding mouse line that utilizes terminal deoxynucleotidyl transferase (TdT) and 30 CRISPR target sites. DARLIN is inducible, generates massive lineage barcodes across tissues, and enables the detection of edited barcodes in â¼70% of profiled single cells. Using DARLIN, we examined fate bias within developing hematopoietic stem cells (HSCs) and revealed unique features of HSC migration. Additionally, we established a protocol for joint transcriptomic and epigenomic single-cell measurements with DARLIN and found that cellular clonal memory is associated with genome-wide DNA methylation rather than gene expression or chromatin accessibility. DARLIN will enable the high-resolution study of lineage relationships and their molecular signatures in diverse tissues and physiological contexts.
Asunto(s)
Epigenómica , Transcriptoma , Animales , Ratones , Transcriptoma/genética , Linaje de la Célula/genética , Perfilación de la Expresión Génica , Modelos Animales de Enfermedad , ADNRESUMEN
Somatic mutations in nonmalignant tissues accumulate with age and injury, but whether these mutations are adaptive on the cellular or organismal levels is unclear. To interrogate genes in human metabolic disease, we performed lineage tracing in mice harboring somatic mosaicism subjected to nonalcoholic steatohepatitis (NASH). Proof-of-concept studies with mosaic loss of Mboat7, a membrane lipid acyltransferase, showed that increased steatosis accelerated clonal disappearance. Next, we induced pooled mosaicism in 63 known NASH genes, allowing us to trace mutant clones side by side. This in vivo tracing platform, which we coined MOSAICS, selected for mutations that ameliorate lipotoxicity, including mutant genes identified in human NASH. To prioritize new genes, additional screening of 472 candidates identified 23 somatic perturbations that promoted clonal expansion. In validation studies, liver-wide deletion of Tbx3, Bcl6, or Smyd2 resulted in protection against hepatic steatosis. Selection for clonal fitness in mouse and human livers identifies pathways that regulate metabolic disease.
Asunto(s)
Enfermedades Metabólicas , Enfermedad del Hígado Graso no Alcohólico , Animales , Humanos , Masculino , Ratones , N-Metiltransferasa de Histona-Lisina/genética , Hígado/metabolismo , Mosaicismo , Enfermedad del Hígado Graso no Alcohólico/genética , Enfermedad del Hígado Graso no Alcohólico/metabolismoRESUMEN
Normal tissues accumulate genetic changes with age, but it is unknown if somatic mutations promote clonal expansion of non-malignant cells in the setting of chronic degenerative diseases. Exome sequencing of diseased liver samples from 82 patients revealed a complex mutational landscape in cirrhosis. Additional ultra-deep sequencing identified recurrent mutations in PKD1, PPARGC1B, KMT2D, and ARID1A. The number and size of mutant clones increased as a function of fibrosis stage and tissue damage. To interrogate the functional impact of mutated genes, a pooled in vivo CRISPR screening approach was established. In agreement with sequencing results, examination of 147 genes again revealed that loss of Pkd1, Kmt2d, and Arid1a promoted clonal expansion. Conditional heterozygous deletion of these genes in mice was also hepatoprotective in injury assays. Pre-malignant somatic alterations are often viewed through the lens of cancer, but we show that mutations can promote regeneration, likely independent of carcinogenesis.
Asunto(s)
Hepatopatías/patología , Hígado/metabolismo , Regeneración , Animales , Enfermedad Crónica , Repeticiones Palindrómicas Cortas Agrupadas y Regularmente Espaciadas/genética , Proteínas de Unión al ADN/genética , Proteínas de Unión al ADN/metabolismo , Femenino , Humanos , Hidrolasas/deficiencia , Hidrolasas/genética , Hígado/patología , Cirrosis Hepática/inducido químicamente , Cirrosis Hepática/genética , Cirrosis Hepática/patología , Hepatopatías/genética , Masculino , Ratones , Ratones Noqueados , Persona de Mediana Edad , Mutación , Proteínas de Neoplasias/genética , Proteínas de Neoplasias/metabolismo , Proteínas Nucleares/genética , Proteínas Nucleares/metabolismo , Proteínas de Unión al ARN/genética , Proteínas de Unión al ARN/metabolismo , Regeneración/fisiología , Canales Catiónicos TRPP/genética , Canales Catiónicos TRPP/metabolismo , Factores de Transcripción/genética , Factores de Transcripción/metabolismo , Secuenciación del ExomaRESUMEN
Stromal cells in adult bone marrow that express leptin receptor (LEPR) are a critical source of growth factors, including stem cell factor (SCF), for the maintenance of haematopoietic stem cells and early restricted progenitors1-6. LEPR+ cells are heterogeneous, including skeletal stem cells and osteogenic and adipogenic progenitors7-12, although few markers have been available to distinguish these subsets or to compare their functions. Here we show that expression of an osteogenic growth factor, osteolectin13,14, distinguishes peri-arteriolar LEPR+ cells poised to undergo osteogenesis from peri-sinusoidal LEPR+ cells poised to undergo adipogenesis (but retaining osteogenic potential). Peri-arteriolar LEPR+osteolectin+ cells are rapidly dividing, short-lived osteogenic progenitors that increase in number after fracture and are depleted during ageing. Deletion of Scf from adult osteolectin+ cells did not affect the maintenance of haematopoietic stem cells or most restricted progenitors but depleted common lymphoid progenitors, impairing lymphopoiesis, bacterial clearance, and survival after acute bacterial infection. Peri-arteriolar osteolectin+ cell maintenance required mechanical stimulation. Voluntary running increased, whereas hindlimb unloading decreased, the frequencies of peri-arteriolar osteolectin+ cells and common lymphoid progenitors. Deletion of the mechanosensitive ion channel PIEZO1 from osteolectin+ cells depleted osteolectin+ cells and common lymphoid progenitors. These results show that a peri-arteriolar niche for osteogenesis and lymphopoiesis in bone marrow is maintained by mechanical stimulation and depleted during ageing.
Asunto(s)
Arteriolas , Linfopoyesis , Osteogénesis , Nicho de Células Madre , Tejido Adiposo/citología , Envejecimiento , Animales , Células de la Médula Ósea/citología , Huesos/citología , Femenino , Factores de Crecimiento de Célula Hematopoyética/metabolismo , Lectinas Tipo C/metabolismo , Linfocitos/citología , Masculino , Ratones , Receptores de Leptina/metabolismo , Factor de Células Madre , Células del Estroma/citologíaRESUMEN
BACKGROUND AND AIMS: The liver is remarkably regenerative and can completely recover even when 80% of its mass is surgically removed. Identification of secreted factors that regulate liver growth would help us understand how organ size and regeneration are controlled but also provide candidate targets to promote regeneration or impair cancer growth. APPROACH AND RESULTS: To enrich for secreted factors that regulate growth control, we induced massive liver overgrowth with either YAP or MYC . Differentially expressed secreted factors were identified in these livers using transcriptomic analysis. To rank candidates by functionality, we performed in vivo CRISPR screening using the Fah knockout model of tyrosinemia. We identified secreted phosphoprotein-2 (SPP2) as a secreted factor that negatively regulates regeneration. Spp2 -deficient mice showed increased survival after acetaminophen poisoning and reduced fibrosis after repeated carbon tetrachloride injections. We examined the impact of SPP2 on bone morphogenetic protein signaling in liver cells and found that SPP2 antagonized bone morphogenetic protein signaling in vitro and in vivo. We also identified cell-surface receptors that interact with SPP2 using a proximity biotinylation assay coupled with mass spectrometry. We showed that SPP2's interactions with integrin family members are in part responsible for some of the regeneration phenotypes. CONCLUSIONS: Using an in vivo CRISPR screening system, we identified SPP2 as a secreted factor that negatively regulates liver regeneration. This study provides ways to identify, validate, and characterize secreted factors in vivo.
Asunto(s)
Regeneración Hepática , Neoplasias , Ratones , Animales , Hígado/metabolismo , Hepatocitos/metabolismo , Transducción de SeñalRESUMEN
BACKGROUND & AIMS: Thirty to 90% of hepatocytes contain whole-genome duplications, but little is known about the fates or functions of these polyploid cells or how they affect development of liver disease. We investigated the effects of continuous proliferative pressure, observed in chronically damaged liver tissues, on polyploid cells. METHODS: We studied Rosa-rtTa mice (controls) and Rosa-rtTa;TRE-short hairpin RNA mice, which have reversible knockdown of anillin, actin binding protein (ANLN). Transient administration of doxycycline increases the frequency and degree of hepatocyte polyploidy without permanently altering levels of ANLN. Mice were then given diethylnitrosamine and carbon tetrachloride (CCl4) to induce mutations, chronic liver damage, and carcinogenesis. We performed partial hepatectomies to test liver regeneration and then RNA-sequencing to identify changes in gene expression. Lineage tracing was used to rule out repopulation from non-hepatocyte sources. We imaged dividing hepatocytes to estimate the frequency of mitotic errors during regeneration. We also performed whole-exome sequencing of 54 liver nodules from patients with cirrhosis to quantify aneuploidy, a possible outcome of polyploid cell divisions. RESULTS: Liver tissues from control mice given CCl4 had significant increases in ploidy compared with livers from uninjured mice. Mice with knockdown of ANLN had hepatocyte ploidy above physiologic levels and developed significantly fewer liver tumors after administration of diethylnitrosamine and CCl4 compared with control mice. Increased hepatocyte polyploidy was not associated with altered regenerative capacity or tissue fitness, changes in gene expression, or more mitotic errors. Based on lineage-tracing experiments, non-hepatocytes did not contribute to liver regeneration in mice with increased polyploidy. Despite an equivalent rate of mitosis in hepatocytes of differing ploidies, we found no lagging chromosomes or micronuclei in mitotic polyploid cells. In nodules of human cirrhotic liver tissue, there was no evidence of chromosome-level copy number variations. CONCLUSIONS: Mice with increased polyploid hepatocytes develop fewer liver tumors following chronic liver damage. Remarkably, polyploid hepatocytes maintain the ability to regenerate liver tissues during chronic damage without generating mitotic errors, and aneuploidy is not commonly observed in cirrhotic livers. Strategies to increase numbers of polypoid hepatocytes might be effective in preventing liver cancer.
Asunto(s)
Carcinoma Hepatocelular/genética , Hepatocitos/fisiología , Neoplasias Hepáticas/genética , Regeneración Hepática/genética , Poliploidía , Animales , Tetracloruro de Carbono/toxicidad , Carcinoma Hepatocelular/inducido químicamente , Carcinoma Hepatocelular/patología , Células Cultivadas , Enfermedad Hepática Inducida por Sustancias y Drogas/etiología , Enfermedad Hepática Inducida por Sustancias y Drogas/patología , Dietilnitrosamina/toxicidad , Femenino , Técnicas de Silenciamiento del Gen , Hepatectomía , Hepatocitos/efectos de los fármacos , Humanos , Hígado/citología , Hígado/efectos de los fármacos , Hígado/patología , Cirrosis Hepática/genética , Cirrosis Hepática/patología , Neoplasias Hepáticas/inducido químicamente , Neoplasias Hepáticas/patología , Neoplasias Hepáticas Experimentales/inducido químicamente , Neoplasias Hepáticas Experimentales/genética , Neoplasias Hepáticas Experimentales/patología , Regeneración Hepática/efectos de los fármacos , Masculino , Ratones , Ratones Transgénicos , Proteínas de Microfilamentos/genética , Proteínas de Microfilamentos/metabolismo , Cultivo Primario de Células , Factores Protectores , RNA-Seq , Secuenciación del ExomaRESUMEN
Gene fusions and fusion products were thought to be unique features of neoplasia. However, more and more studies have identified fusion RNAs in normal physiology. Through RNA sequencing of 27 human noncancer tissues, a large number of fusion RNAs were found. By analyzing fusion transcriptome, we observed close clusterings between samples of same or similar tissues, supporting the feasibility of using fusion RNA profiling to reveal connections between biological samples. To put the concept into use, we selected alveolar rhabdomyosarcoma (ARMS), a myogenic pediatric cancer whose exact cell of origin is not clear. PAX3-FOXO1 (paired box gene 3 fused with forkhead box O1) fusion RNA, which is considered a hallmark of ARMS, was recently found during normal muscle cell differentiation. We performed and analyzed RNA sequencing from various time points during myogenesis and uncovered many chimeric fusion RNAs. Interestingly, we found that the fusion RNA profile of RH30, an ARMS cell line, is most similar to the myogenesis time point when PAX3-FOXO1 is expressed. In contrast, full transcriptome clustering analysis failed to uncover this connection. Strikingly, all of the 18 chimeric RNAs in RH30 cells could be detected at the same myogenic time point(s). In addition, the seven chimeric RNAs that follow the exact transient expression pattern as PAX3-FOXO1 are specific to rhabdomyosarcoma cells. Further testing with clinical samples also confirmed their specificity to rhabdomyosarcoma. These results provide further support for the link between at least some ARMSs and the PAX3-FOXO1-expressing myogenic cells and demonstrate that fusion RNA profiling can be used to investigate the etiology of fusion-gene-associated cancers.
Asunto(s)
Fusión Génica , ARN/genética , Rabdomiosarcoma Alveolar/genética , Línea Celular Tumoral , Proteína Forkhead Box O1/genética , Perfilación de la Expresión Génica , Humanos , Células Madre Mesenquimatosas , Desarrollo de Músculos/genética , Factor de Transcripción PAX3/genética , Análisis de Secuencia de ARNRESUMEN
Gene fusions and their products (RNA and protein) were once thought to be unique features to cancer. However, chimeric RNAs can also be found in normal cells. Here, we performed, curated and analyzed nearly 300 RNA-Seq libraries covering 30 different non-neoplastic human tissues and cells as well as 15 mouse tissues. A large number of fusion transcripts were found. Most fusions were detected only once, while 291 were seen in more than one sample. We focused on the recurrent fusions and performed RNA and protein level validations on a subset. We characterized these fusions based on various features of the fusions, and their parental genes. They tend to be expressed at higher levels relative to their parental genes than the non-recurrent ones. Over half of the recurrent fusions involve neighboring genes transcribing in the same direction. A few sequence motifs were found enriched close to the fusion junction sites. We performed functional analyses on a few widely expressed fusions, and found that silencing them resulted in dramatic reduction in normal cell growth and/or motility. Most chimeras use canonical splicing sites, thus are likely products of 'intergenic splicing'. We also explored the implications of these non-pathological fusions in cancer and in evolution.
Asunto(s)
Fibroblastos/metabolismo , Fusión Génica , Células Madre Mesenquimatosas/metabolismo , Empalme del ARN , ARN Mensajero/genética , Animales , Astrocitos/citología , Astrocitos/metabolismo , Secuencia de Bases , Línea Celular Transformada , Biología Computacional , Evolución Molecular , Fibroblastos/citología , Biblioteca de Genes , Silenciador del Gen , Secuenciación de Nucleótidos de Alto Rendimiento , Humanos , Células Madre Mesenquimatosas/citología , Ratones , Datos de Secuencia Molecular , Cultivo Primario de Células , ARN Mensajero/antagonistas & inhibidores , ARN Mensajero/metabolismo , ARN Interferente Pequeño/genética , ARN Interferente Pequeño/metabolismo , Análisis de Secuencia de ARN , Especificidad de la EspecieRESUMEN
Mitochondria are critical for proper organ function and mechanisms to promote mitochondrial health during regeneration would benefit tissue homeostasis. We report that during liver regeneration, proliferation is suppressed in electron transport chain (ETC)-dysfunctional hepatocytes due to an inability to generate acetyl-CoA from peripheral fatty acids through mitochondrial ß-oxidation. Alternative modes for acetyl-CoA production from pyruvate or acetate are suppressed in the setting of ETC dysfunction. This metabolic inflexibility forces a dependence on ETC-functional mitochondria and restoring acetyl-CoA production from pyruvate is sufficient to allow ETC-dysfunctional hepatocytes to proliferate. We propose that metabolic inflexibility within hepatocytes can be advantageous by limiting the expansion of ETC-dysfunctional cells.
Asunto(s)
Acetilcoenzima A , Hepatocitos , Regeneración Hepática , Mitocondrias Hepáticas , Ácido Pirúvico , Animales , Hepatocitos/metabolismo , Acetilcoenzima A/metabolismo , Ratones , Ácido Pirúvico/metabolismo , Mitocondrias Hepáticas/metabolismo , Oxidación-Reducción , Proliferación Celular , Ácidos Grasos/metabolismo , Hígado/metabolismo , Transporte de Electrón , Ratones Endogámicos C57BL , Mitocondrias/metabolismo , MasculinoRESUMEN
Cancer cells exhibit distinct metabolic activities and nutritional dependencies compared to normal cells. Thus, characterization of nutrient demands by individual tumor types may identify specific vulnerabilities that can be manipulated to target the destruction of cancer cells. We find that MYC-driven liver tumors rely on augmented tryptophan (Trp) uptake, yet Trp utilization to generate metabolites in the kynurenine (Kyn) pathway is reduced. Depriving MYC-driven tumors of Trp through a No-Trp diet not only prevents tumor growth but also restores the transcriptional profile of normal liver cells. Despite Trp starvation, protein synthesis remains unhindered in liver cancer cells. We define a crucial role for the Trp-derived metabolite indole 3-pyruvate (I3P) in liver tumor growth. I3P supplementation effectively restores the growth of liver cancer cells starved of Trp. These findings suggest that I3P is a potential therapeutic target in MYC-driven cancers. Developing methods to target this metabolite represents a potential avenue for liver cancer treatment.
Asunto(s)
Carcinogénesis , Indoles , Neoplasias Hepáticas , Proteínas Proto-Oncogénicas c-myc , Triptófano , Triptófano/metabolismo , Animales , Neoplasias Hepáticas/metabolismo , Neoplasias Hepáticas/genética , Neoplasias Hepáticas/patología , Indoles/metabolismo , Indoles/farmacología , Humanos , Proteínas Proto-Oncogénicas c-myc/metabolismo , Proteínas Proto-Oncogénicas c-myc/genética , Ratones , Carcinogénesis/metabolismo , Carcinogénesis/genética , Línea Celular Tumoral , Quinurenina/metabolismo , Ratones Endogámicos C57BL , Hígado/metabolismo , Hígado/patología , MasculinoRESUMEN
Somatic mutations in non-malignant tissues accumulate with age and insult, but whether these mutations are adaptive on the cellular or organismal levels is unclear. To interrogate mutations found in human metabolic disease, we performed lineage tracing in mice harboring somatic mosaicism subjected to non-alcoholic steatohepatitis (NASH). Proof-of-concept studies with mosaic loss of Mboat7 , a membrane lipid acyltransferase, showed that increased steatosis accelerated clonal disappearance. Next, we induced pooled mosaicism in 63 known NASH genes, allowing us to trace mutant clones side-by-side. This in vivo tracing platform, which we coined MOSAICS, selected for mutations that ameliorate lipotoxicity, including mutant genes identified in human NASH. To prioritize new genes, additional screening of 472 candidates identified 23 somatic perturbations that promoted clonal expansion. In validation studies, liver-wide deletion of Bcl6, Tbx3, or Smyd2 resulted in protection against NASH. Selection for clonal fitness in mouse and human livers identifies pathways that regulate metabolic disease. Highlights: Mosaic Mboat7 mutations that increase lipotoxicity lead to clonal disappearance in NASH. In vivo screening can identify genes that alter hepatocyte fitness in NASH. Mosaic Gpam mutations are positively selected due to reduced lipogenesis. In vivo screening of transcription factors and epifactors identified new therapeutic targets in NASH.
RESUMEN
A fundamental issue in regenerative medicine is whether there exist endogenous regulatory mechanisms that limit the speed and efficiency of the repair process. We report the existence of a maturation checkpoint during muscle regeneration that pauses myofibers at a neonatal stage. This checkpoint is regulated by the mitochondrial protein mitofusin 2 (Mfn2), the expression of which is activated in response to muscle injury. Mfn2 is required for growth and maturation of regenerating myofibers; in the absence of Mfn2, new myofibers arrested at a neonatal stage, characterized by centrally nucleated myofibers and loss of H3K27me3 repressive marks at the neonatal myosin heavy chain gene. A similar arrest at the neonatal stage was observed in infantile cases of human centronuclear myopathy. Mechanistically, Mfn2 upregulation suppressed expression of hypoxia-induced factor 1α (HIF1α), which is induced in the setting of muscle damage. Sustained HIF1α signaling blocked maturation of new myofibers at the neonatal-to-adult fate transition, revealing the existence of a checkpoint that delays muscle regeneration. Correspondingly, inhibition of HIF1α allowed myofibers to bypass the checkpoint, thereby accelerating the repair process. We conclude that skeletal muscle contains a regenerative checkpoint that regulates the speed of myofiber maturation in response to Mfn2 and HIF1α activity.
Asunto(s)
Subunidad alfa del Factor 1 Inducible por Hipoxia , Proteínas Mitocondriales , Músculo Esquelético , Regeneración , Humanos , Recién Nacido , Fibras Musculares Esqueléticas/metabolismo , Músculo Esquelético/metabolismo , Cadenas Pesadas de Miosina , Transducción de Señal , Subunidad alfa del Factor 1 Inducible por Hipoxia/metabolismo , Proteínas Mitocondriales/metabolismoRESUMEN
Identifying new pathways that regulate mammalian regeneration is challenging due to the paucity of in vivo screening approaches. We employed pooled CRISPR knockout and activation screening in the regenerating liver to evaluate 165 chromatin regulatory proteins. Both screens identified the imitation-SWI chromatin remodeling components Baz2a and Baz2b, not previously implicated in regeneration. In vivo sgRNA, siRNA, and knockout strategies against either paralog confirmed increased regeneration. Distinct BAZ2-specific bromodomain inhibitors, GSK2801 and BAZ2-ICR, resulted in accelerated liver healing after diverse injuries. Inhibitor-treated mice also exhibited improved healing in an inflammatory bowel disease model, suggesting multi-tissue applicability. Transcriptomics on regenerating livers showed increases in ribosomal and cell cycle mRNAs. Surprisingly, CRISPRa screening to define mechanisms showed that overproducing Rpl10a or Rpl24 was sufficient to drive regeneration, whereas Rpl24 haploinsufficiency was rate limiting for BAZ2 inhibition-mediated regeneration. The discovery of regenerative roles for imitation-SWI components provides immediate strategies to enhance tissue repair.
Asunto(s)
Cromatina , Proteínas Cromosómicas no Histona , Regeneración Hepática , Animales , Proliferación Celular , Cromatina/metabolismo , Proteínas Cromosómicas no Histona/genética , Repeticiones Palindrómicas Cortas Agrupadas y Regularmente Espaciadas , Hepatocitos/metabolismo , Hígado/metabolismo , Ratones , Ratones Endogámicos ICRRESUMEN
The dynamic regulation of ß-cell abundance is poorly understood. Since chromatin remodeling plays critical roles in liver regeneration, these mechanisms could be generally important for regeneration in other tissues. Here, we show that the ARID1A mammalian SWI/SNF complex subunit is a critical regulator of ß-cell regeneration. Arid1a is highly expressed in quiescent ß-cells but is physiologically suppressed when ß-cells proliferate during pregnancy or after pancreas resection. Whole-body Arid1a knockout mice are protected against streptozotocin-induced diabetes. Cell-type and temporally specific genetic dissection show that ß-cell-specific Arid1a deletion can potentiate ß-cell regeneration in multiple contexts. Transcriptomic and epigenomic profiling of mutant islets reveal increased neuregulin-ERBB-NR4A signaling. Chemical inhibition of ERBB or NR4A1 blocks increased regeneration associated with Arid1a loss. Mammalian SWI/SNF (mSWI/SNF) complex activity is a barrier to ß-cell regeneration in physiologic and disease states.
Asunto(s)
Factor de Crecimiento Epidérmico , Proteínas Nucleares , Ratones , Animales , Embarazo , Femenino , Proteínas Nucleares/genética , Proteínas Nucleares/metabolismo , Ensamble y Desensamble de Cromatina , Transducción de Señal , Regeneración Hepática , Mamíferos/metabolismo , Proteínas de Unión al ADN/genética , Factores de Transcripción/genéticaRESUMEN
The liver is organized into zones in which hepatocytes express different metabolic enzymes. The cells most responsible for liver repopulation and regeneration remain undefined, because fate mapping has only been performed on a few hepatocyte subsets. Here, 14 murine fate-mapping strains were used to systematically compare distinct subsets of hepatocytes. During homeostasis, cells from both periportal zone 1 and pericentral zone 3 contracted in number, whereas cells from midlobular zone 2 expanded in number. Cells within zone 2, which are sheltered from common injuries, also contributed to regeneration after pericentral and periportal injuries. Repopulation from zone 2 was driven by the insulin-like growth factor binding protein 2-mechanistic target of rapamycin-cyclin D1 (IGFBP2-mTOR-CCND1) axis. Therefore, different regions of the lobule exhibit differences in their contribution to hepatocyte turnover, and zone 2 is an important source of new hepatocytes during homeostasis and regeneration.
Asunto(s)
Hepatocitos/fisiología , Regeneración Hepática , Hígado/fisiología , Animales , Sistema Biliar/citología , Enfermedades de las Vías Biliares/fisiopatología , Proliferación Celular , Ciclina D1/metabolismo , Técnicas de Sustitución del Gen , Homeostasis , Proteína 2 de Unión a Factor de Crecimiento Similar a la Insulina/metabolismo , Hígado/citología , Ratones , Serina-Treonina Quinasas TOR/metabolismoRESUMEN
SWI/SNF chromatin remodelers play critical roles in development and cancer. The causal links between SWI/SNF complex disassembly and carcinogenesis are obscured by redundancy between paralogous components. Canonical cBAF-specific paralogs ARID1A and ARID1B are synthetic lethal in some contexts, but simultaneous mutations in both ARID1s are prevalent in cancer. To understand if and how cBAF abrogation causes cancer, we examined the physiologic and biochemical consequences of ARID1A/ARID1B loss. In double knockout liver and skin, aggressive carcinogenesis followed de-differentiation and hyperproliferation. In double mutant endometrial cancer, add-back of either induced senescence. Biochemically, residual cBAF subcomplexes resulting from loss of ARID1 scaffolding were unexpectedly found to disrupt polybromo containing pBAF function. 37 of 69 mutations in the conserved scaffolding domains of ARID1 proteins observed in human cancer caused complex disassembly, partially explaining their mutation spectra. ARID1-less, cBAF-less states promote carcinogenesis across tissues, and suggest caution against paralog-directed therapies for ARID1-mutant cancer.
Asunto(s)
Carcinogénesis , Proteínas de Unión al ADN , Neoplasias , Factores de Transcripción , Carcinogénesis/genética , Cromatina , Proteínas de Unión al ADN/genética , Humanos , Mutación , Neoplasias/genética , Factores de Transcripción/genéticaRESUMEN
Multiple human polyomaviruses (HPyV) can infect the skin, but only Merkel cell polyomavirus (MCPyV) has been implicated in the development of a cancer, Merkel cell carcinoma (MCC). While expression of HPyV6, HPyV7, and MCPyV small T antigens (sT), all induced a senescence-associated secretory phenotype (SASP), MCPyV sT uniquely activated noncanonical NF-κB (ncNF-κB), instead of canonical NF-κB signaling, to evade p53-mediated cellular senescence. Through its large T stabilization domain, MCPyV sT activated ncNF-κB signaling both by inducing H3K4 trimethylation-mediated increases of NFKB2 and RELB transcription and also by promoting NFKB2 stabilization and activation through FBXW7 inhibition. Noncanonical NF-κB signaling was required for SASP cytokine secretion, which promoted the proliferation of MCPyV sT-expressing cells through autocrine signaling. Virus-positive MCC cell lines and tumors showed ncNF-κB pathway activation and SASP gene expression, and the inhibition of ncNF-κB signaling prevented VP-MCC cell growth in vitro and in xenografts. We identify MCPyV sT-induced ncNF-κB signaling as an essential tumorigenic pathway in MCC. IMPLICATIONS: This work is the first to identify the activation of ncNF-κB signaling by any polyomavirus and its critical role in MCC tumorigenesis.
Asunto(s)
Antígenos Virales de Tumores/metabolismo , Poliomavirus de Células de Merkel/genética , FN-kappa B/metabolismo , Oncogenes/genética , Infecciones por Polyomavirus/genética , Infecciones Tumorales por Virus/genética , Carcinogénesis , Humanos , Infecciones por Polyomavirus/patología , Transducción de Señal , Infecciones Tumorales por Virus/patologíaRESUMEN
Glioblastoma is a deadly cancer, with no effective therapies. Better understanding and identification of selective targets are urgently needed. We found that advillin (AVIL) is overexpressed in all the glioblastomas we tested including glioblastoma stem/initiating cells, but hardly detectable in non-neoplastic astrocytes, neural stem cells or normal brain. Glioma patients with increased AVIL expression have a worse prognosis. Silencing AVIL nearly eradicated glioblastoma cells in culture, and dramatically inhibited in vivo xenografts in mice, but had no effect on normal control cells. Conversely, overexpressing AVIL promoted cell proliferation and migration, enabled fibroblasts to escape contact inhibition, and transformed immortalized astrocytes, supporting AVIL being a bona fide oncogene. We provide evidence that the tumorigenic effect of AVIL is partly mediated by FOXM1, which regulates LIN28B, whose expression also correlates with clinical prognosis. AVIL regulates the cytoskeleton through modulating F-actin, while mutants disrupting F-actin binding are defective in its tumorigenic capabilities.