RESUMEN
Nuclear receptors (NRs), are a wide family of ligand-regulated transcription factors sharing a common modular structure composed by an N-terminal domain and a ligand-binding domain connected by a short hinge linker to a DNA-binding domain. NRs are involved in many physiological processes, including metabolism, reproduction and development. Most of them respond to small lipophilic ligands, such as steroids, retinoids, and phospholipids, which act as conformational switches. Some NRs are still "orphan" and the search for their ligands is still ongoing. Upon DNA binding, NRs can act both as transcriptional activators or repressors of their target genes. Theoretically, the possibility to modulate NRs activity with small molecules makes them ideal therapeutic targets, although the complexity of their signaling makes drug design challenging. In this review, we discuss the role of NRs in erythropoiesis, in both homeostatic and stress conditions. This knowledge is important in view of modulating red blood cells production in disease conditions, such as anemias, and for the expansion of erythroid cells in culture for research purposes and for reaching the long-term goal of cultured blood for transfusion.
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Eritropoyesis , Receptores Citoplasmáticos y Nucleares , ADN/metabolismo , Ligandos , Factores de Transcripción/metabolismoRESUMEN
The human fetal γ-globin gene is repressed in the adult stage through complex regulatory mechanisms involving transcription factors and epigenetic modifiers. Reversing γ-globin repression, or maintaining its expression by manipulating regulatory mechanisms, has become a major clinical goal in the treatment of ß-hemoglobinopathies. Here, we identify the orphan nuclear receptor Coup-TFII (NR2F2/ARP-1) as an embryonic/fetal stage activator of γ-globin expression. We show that Coup-TFII is expressed in early erythropoiesis of yolk sac origin, together with embryonic/fetal globins. When overexpressed in adult cells (including peripheral blood cells from human healthy donors and ß039 thalassemic patients) Coup-TFII activates the embryonic/fetal globins genes, overcoming the repression imposed by the adult erythroid environment. Conversely, the knock-out of Coup-TFII increases the ß/γ+ß globin ratio. Molecular analysis indicates that Coup-TFII binds in vivo to the ß-locus and contributes to its conformation. Overall, our data identify Coup-TFII as a specific activator of the γ-globin gene.
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Receptores Nucleares Huérfanos , gamma-Globinas , Factor de Transcripción COUP II/genética , Factor de Transcripción COUP II/metabolismo , Proteínas Portadoras/genética , Humanos , Regiones Promotoras Genéticas , gamma-Globinas/genéticaRESUMEN
Toll-like receptors (TLRs) are the best characterized pattern recognition receptors. Individual TLRs recruit diverse combinations of adaptor proteins, triggering signal transduction pathways and leading to the activation of various transcription factors, including nuclear factor kappaB, activation protein 1 and interferon regulatory factors. Interleukin-2 is one of the molecules produced by mouse dendritic cells after stimulation by different pattern recognition receptor agonists. By analogy with the events after T-cell receptor engagement leading to interleukin-2 production, it is therefore plausible that the stimulation of TLRs on dendritic cells may lead to activation of the Ca(2+)/calcineurin and NFAT (nuclear factor of activated T cells) pathway. Here we show that mouse dendritic cell stimulation with lipopolysaccharide (LPS) induces Src-family kinase and phospholipase Cgamma2 activation, influx of extracellular Ca(2+) and calcineurin-dependent nuclear NFAT translocation. The initiation of this pathway is independent of TLR4 engagement, and dependent exclusively on CD14. We also show that LPS-induced NFAT activation via CD14 is necessary to cause the apoptotic death of terminally differentiated dendritic cells, an event that is essential for maintaining self-tolerance and preventing autoimmunity. Consequently, blocking this pathway in vivo causes prolonged dendritic cell survival and an increase in T-cell priming capability. Our findings reveal novel aspects of molecular signalling triggered by LPS in dendritic cells, and identify a new role for CD14: the regulation of the dendritic cell life cycle through NFAT activation. Given the involvement of CD14 in disease, including sepsis and chronic heart failure, the discovery of signal transduction pathways activated exclusively via CD14 is an important step towards the development of potential treatments involving interference with CD14 functions.
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Células Dendríticas/citología , Células Dendríticas/inmunología , Receptores de Lipopolisacáridos/metabolismo , Lipopolisacáridos/inmunología , Factores de Transcripción NFATC/metabolismo , Animales , Apoptosis/efectos de los fármacos , Células de la Médula Ósea/efectos de los fármacos , Linfocitos T CD4-Positivos/efectos de los fármacos , Linfocitos T CD4-Positivos/inmunología , Calcio/metabolismo , Señalización del Calcio/efectos de los fármacos , Diferenciación Celular , Supervivencia Celular/efectos de los fármacos , Células Dendríticas/efectos de los fármacos , Células Dendríticas/metabolismo , Lipopolisacáridos/farmacología , Macrófagos/citología , Macrófagos/efectos de los fármacos , Macrófagos/inmunología , Ratones , Ratones Endogámicos C57BL , Fosfolipasa C gamma/metabolismo , Familia-src Quinasas/metabolismoRESUMEN
The transcription factor GATA1 is essential for erythroid and megakaryocytic cell differentiation. Gata1 hematopoietic regulatory domain (G1HRD) has been shown to recapitulate endogenous Gata1 gene expression in transgenic mouse assays in vivo. G1HRD contains a promoter-proximal enhancer composed of a GATA-palindrome motif, four CP2-binding sites and two CACCC boxes. We prepared transgenic reporter mouse lines in which green fluorescent protein and ß-galactosidase expression are driven by wild-type G1HRD (as a positive control) and the G1HRD harboring mutations within these cis-acting elements (as the experimental conditions), respectively. Exploiting this transgenic dual reporter (TDR) assay, we show here that in definitive erythropoiesis, G1HRD activity was markedly affected by individual mutations in the GATA-palindrome motif and the CACCC boxes. Mutation of CP2-binding sites also moderately decreased G1HRD activity. The combined mutation of the CP2-binding sites and the GATA-palindrome motif resulted in complete loss of G1HRD activity. In contrast, in primitive erythroid cells, individual mutations of each element did not affect G1HRD activity; G1HRD activity was abolished only when these three mutations were combined. These results thus show that all three elements independently and cooperatively contribute to G1HRD activity in vivo in definitive erythropoiesis, although these are contributing redundantly to primitive erythropoiesis.
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Elementos de Facilitación Genéticos , Factor de Transcripción GATA1/genética , Regiones Promotoras Genéticas , Animales , Sitios de Unión , Diferenciación Celular , Eritropoyesis , Factor de Transcripción GATA1/metabolismo , Genes Reporteros , Ratones , Ratones Transgénicos , Secuencias Reguladoras de Ácidos NucleicosRESUMEN
Hematopoietic stem cells (HSC) maintain blood production throughout life. Nevertheless, HSC functionality deteriorates upon physiological aging leading to the increased prevalence of haematological diseases and hematopoietic malignancies in the elderly. Deubiquitinating enzymes (DUBs) by reverting protein ubiquitination ensure proper proteostasis, a key process in HSC maintenance and fitness.
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The identification of regulatory networks contributing to fetal/adult gene expression switches is a major challenge in developmental biology and key to understand the aberrant proliferation of cancer cells, which often reactivate fetal oncogenes. One key example is represented by the developmental gene LIN28B, whose aberrant reactivation in adult tissues promotes tumor initiation and progression. Despite the prominent role of LIN28B in development and cancer, the mechanisms of its transcriptional regulation are largely unknown. Here, by using quantitative RT-PCR and single cell RNA sequencing data, we show that in erythropoiesis the expression of the transcription factor SOX6 matched a sharp decline of LIN28B mRNA during human embryo/fetal to adult globin switching. SOX6 overexpression repressed LIN28B not only in a panel of fetal-like erythroid cells (K562, HEL and HUDEP1; ≈92% p < 0.0001, 54% p = 0.0009 and ≈60% p < 0.0001 reduction, respectively), but also in hepatoblastoma HepG2 and neuroblastoma SH-SY5H cells (≈99% p < 0.0001 and ≈59% p < 0.0001 reduction, respectively). SOX6-mediated repression caused downregulation of the LIN28B/Let-7 targets, including MYC and IGF2BP1, and rapidly blocks cell proliferation. Mechanistically, Lin28B repression is accompanied by SOX6 physical binding within its locus, suggesting a direct mechanism of LIN28B downregulation that might contribute to the fetal/adult erythropoietic transition and restrict cancer proliferation.
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Proteínas de Unión al ARN , Factores de Transcripción SOXD , Humanos , Factores de Transcripción SOXD/genética , Factores de Transcripción SOXD/metabolismo , Proteínas de Unión al ARN/metabolismo , Proteínas de Unión al ARN/genética , Línea Celular Tumoral , Regulación del Desarrollo de la Expresión Génica , Eritropoyesis/genética , MicroARNs/genética , MicroARNs/metabolismo , Células Hep G2 , Células K562 , Regulación Neoplásica de la Expresión Génica , Células Eritroides/metabolismoRESUMEN
Sox6 belongs to the Sry (sex-determining region Y)-related high-mobility-group-box family of transcription factors, which control cell-fate specification of many cell types. Here, we explored the role of Sox6 in human erythropoiesis by its overexpression both in the erythroleukemic K562 cell line and in primary erythroid cultures from human cord blood CD34+ cells. Sox6 induced significant erythroid differentiation in both models. K562 cells underwent hemoglobinization and, despite their leukemic origin, died within 9 days after transduction; primary erythroid cultures accelerated their kinetics of erythroid maturation and increased the number of cells that reached the final enucleation step. Searching for direct Sox6 targets, we found SOCS3 (suppressor of cytokine signaling-3), a known mediator of cytokine response. Sox6 was bound in vitro and in vivo to an evolutionarily conserved regulatory SOCS3 element, which induced transcriptional activation. SOCS3 overexpression in K562 cells and in primary erythroid cells recapitulated the growth inhibition induced by Sox6, which demonstrates that SOCS3 is a relevant Sox6 effector.
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Células Precursoras Eritroides/fisiología , Eritropoyesis/genética , Factores de Transcripción SOXD/fisiología , Animales , Antígenos CD34/metabolismo , Diferenciación Celular/genética , Procesos de Crecimiento Celular/genética , Células Cultivadas , Ensayo de Unidades Formadoras de Colonias , Células Precursoras Eritroides/metabolismo , Eritropoyesis/fisiología , Regulación de la Expresión Génica/fisiología , Humanos , Células K562 , Ratones , Modelos Biológicos , Factores de Transcripción SOXD/genética , Factores de Transcripción SOXD/metabolismo , Proteína 3 Supresora de la Señalización de Citocinas , Proteínas Supresoras de la Señalización de Citocinas/genética , Proteínas Supresoras de la Señalización de Citocinas/metabolismo , Proteínas Supresoras de la Señalización de Citocinas/fisiología , TransfecciónRESUMEN
The Sox6 transcription factor plays critical roles in various cell types, including erythroid cells. Sox6-deficient mice are anemic due to impaired red cell maturation and show inappropriate globin gene expression in definitive erythrocytes. To identify new Sox6 target genes in erythroid cells, we used the known repressive double Sox6 consensus within the εy-globin promoter to perform a bioinformatic genome-wide search for similar, evolutionarily conserved motifs located within genes whose expression changes during erythropoiesis. We found a highly conserved Sox6 consensus within the Sox6 human gene promoter itself. This sequence is bound by Sox6 in vitro and in vivo, and mediates transcriptional repression in transient transfections in human erythroleukemic K562 cells and in primary erythroblasts. The binding of a lentiviral transduced Sox6FLAG protein to the endogenous Sox6 promoter is accompanied, in erythroid cells, by strong downregulation of the endogenous Sox6 transcript and by decreased in vivo chromatin accessibility of this region to the PstI restriction enzyme. These observations suggest that the negative Sox6 autoregulation, mediated by the double Sox6 binding site within its own promoter, may be relevant to control the Sox6 transcriptional downregulation that we observe in human erythroid cultures and in mouse bone marrow cells in late erythroid maturation.
Asunto(s)
Regulación hacia Abajo/genética , Células Eritroides/metabolismo , Eritropoyesis/genética , Regiones Promotoras Genéticas , Factores de Transcripción SOXD/genética , Animales , Secuencia de Bases , Sitios de Unión , Células Cultivadas , Secuencia Conservada , Humanos , Células K562 , Ratones , Factores de Transcripción SOXD/metabolismo , Transcripción GenéticaRESUMEN
BACKGROUND: During late differentiation, erythroid cells undergo profound changes involving actin filament remodeling. One of the proteins controlling actin dynamics is gelsolin, a calcium-activated actin filament severing and capping protein. Gelsolin-null (Gsn(-/-)) mice generated in a C57BL/6 background are viable and fertile.1 DESIGN AND METHODS: We analyzed the functional roles of gelsolin in erythropoiesis by: (i) evaluating gelsolin expression in murine fetal liver cells at different stages of erythroid differentiation (using reverse transcription polymerase chain reaction analysis and immunohistochemistry), and (ii) characterizing embryonic and adult erythropoiesis in Gsn(-/-) BALB/c mice (morphology and erythroid cultures). RESULTS: In the context of a BALB/c background, the Gsn(-/-) mutation causes embryonic death. Gsn(-/-) embryos show defective erythroid maturation with persistence of circulating nucleated cells. The few Gsn(-/-) mice reaching adulthood fail to recover from phenylhydrazine-induced acute anemia, revealing an impaired response to stress erythropoiesis. In in vitro differentiation assays, E13.5 fetal liver Gsn(-/-) cells failed to undergo terminal maturation, a defect partially rescued by Cytochalasin D, and mimicked by administration of Jasplakinolide to the wild-type control samples. CONCLUSIONS: In BALB/c mice, gelsolin deficiency alters the equilibrium between erythrocyte actin polymerization and depolymerization, causing impaired terminal maturation. We suggest a non-redundant role for gelsolin in terminal erythroid differentiation, possibly contributing to the Gsn(-/-) mice lethality observed in mid-gestation.
Asunto(s)
Células Madre Embrionarias/patología , Eritrocitos/patología , Eritropoyesis/genética , Gelsolina/genética , Hígado/patología , Actinas/antagonistas & inhibidores , Actinas/metabolismo , Anemia/inducido químicamente , Animales , Biomarcadores/metabolismo , Diferenciación Celular/efectos de los fármacos , Citocalasina D/farmacología , Depsipéptidos/farmacología , Embrión de Mamíferos , Células Madre Embrionarias/efectos de los fármacos , Células Madre Embrionarias/metabolismo , Eritrocitos/efectos de los fármacos , Eritrocitos/metabolismo , Feto , Gelsolina/deficiencia , Regulación del Desarrollo de la Expresión Génica/efectos de los fármacos , Hígado/efectos de los fármacos , Hígado/metabolismo , Ratones , Ratones Endogámicos BALB C , Ratones Noqueados , Fenilhidrazinas/toxicidadRESUMEN
Introduction: Diamond Blackfan anemia (DBA) is a rare congenital disease characterized by defective maturation of the erythroid progenitors in the bone marrow, for which treatment involves steroids, chronic transfusions, or hematopoietic stem cells transplantation. Diamond Blackfan anemia is caused by defective ribosome biogenesis due to heterozygous pathogenic variants in one of 19 ribosomal protein (RP) genes. The decreased number of functional ribosomes leads to the activation of pro-apoptotic pathways and to the reduced translation of key genes for erythropoiesis. Results and discussion: Here we characterized the phenotype of RPS26-deficiency in a cell line derived from human umbilical cord blood erythroid progenitors (HUDEP-1 cells). This model recapitulates cellular hallmarks of Diamond Blackfan anemia including: imbalanced production of ribosomal RNAs, upregulation of pro-apoptotic genes and reduced viability, and shows increased levels of intracellular calcium. Evaluation of the expression of erythroid markers revealed the impairment of erythroid differentiation in RPS26-silenced cells compared to control cells. Conclusions: In conclusion, for the first time we assessed the effect of RPS26 deficiency in a human erythroid progenitor cell line and demonstrated that these cells can be used as a scalable model system to study aspects of DBA pathophysiology that have been refractory to detailed investigation because of the paucity of specific cell types affected in this disorder.
RESUMEN
Myeloid neoplasms encompass a very heterogeneous family of diseases characterized by the failure of the molecular mechanisms that ensure a balanced equilibrium between hematopoietic stem cells (HSCs) self-renewal and the proper production of differentiated cells. The origin of the driver mutations leading to preleukemia can be traced back to HSC/progenitor cells. Many properties typical to normal HSCs are exploited by leukemic stem cells (LSCs) to their advantage, leading to the emergence of a clonal population that can eventually progress to leukemia with variable latency and evolution. In fact, different subclones might in turn develop from the original malignant clone through accumulation of additional mutations, increasing their competitive fitness. This process ultimately leads to a complex cancer architecture where a mosaic of cellular clones-each carrying a unique set of mutations-coexists. The repertoire of genes whose mutations contribute to the progression toward leukemogenesis is broad. It encompasses genes involved in different cellular processes, including transcriptional regulation, epigenetics (DNA and histones modifications), DNA damage signaling and repair, chromosome segregation and replication (cohesin complex), RNA splicing, and signal transduction. Among these many players, transcription factors, RNA splicing proteins, and deubiquitinating enzymes are emerging as potential targets for therapeutic intervention.
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The expression of the fetal Gγ- and Aγ-globin genes in normal development is confined to the fetal period, where two γ-globin chains assemble with two α-globin chains to form α2γ2 tetramers (HbF). HbF sustains oxygen delivery to tissues until birth, when ß-globin replaces γ-globin, leading to the formation of α2ß2 tetramers (HbA). However, in different benign and pathological conditions, HbF is expressed in adult cells, as it happens in the hereditary persistence of fetal hemoglobin, in anemias and in some leukemias. The molecular basis of γ-globin differential expression in the fetus and of its inappropriate activation in adult cells is largely unknown, although in recent years, a few transcription factors involved in this process have been identified. The recent discovery that fetal cells can persist to adulthood and contribute to disease raises the possibility that postnatal γ-globin expression could, in some cases, represent the signature of the fetal cellular origin.
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RNA-binding proteins (RBPs) are emerging as important effectors of the cellular DNA damage response (DDR). The RBP FUS is implicated in RNA metabolism and DNA repair, and it undergoes reversible liquid-liquid phase separation (LLPS) in vitro. Here, we demonstrate that FUS-dependent LLPS is necessary for the initiation of the DDR. Using laser microirradiation in FUS-knockout cells, we show that FUS is required for the recruitment to DNA damage sites of the DDR factors KU80, NBS1, and 53BP1 and of SFPQ, another RBP implicated in the DDR. The relocation of KU80, NBS1, and SFPQ is similarly impaired by LLPS inhibitors, or LLPS-deficient FUS variants. We also show that LLPS is necessary for efficient γH2AX foci formation. Finally, using superresolution structured illumination microscopy, we demonstrate that the absence of FUS impairs the proper arrangement of γH2AX nanofoci into higher-order clusters. These findings demonstrate the early requirement for FUS-dependent LLPS in the activation of the DDR and the proper assembly of DSB repair complexes.
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Reparación del ADN/genética , Proteína FUS de Unión a ARN/genética , Línea Celular , Línea Celular Tumoral , Daño del ADN/genética , Células HEK293 , Células HeLa , Humanos , Unión Proteica/genética , Dominios Proteicos/genética , Proteínas de Unión al ARN/genéticaRESUMEN
Hemoglobin is a tetrameric protein composed of two α and two ß chains, each containing a heme group that reversibly binds oxygen. The composition of hemoglobin changes during development in order to fulfill the need of the growing organism, stably maintaining a balanced production of α-like and ß-like chains in a 1:1 ratio. Adult hemoglobin (HbA) is composed of two α and two ß subunits (α2ß2 tetramer), whereas fetal hemoglobin (HbF) is composed of two γ and two α subunits (α2γ2 tetramer). Qualitative or quantitative defects in ß-globin production cause two of the most common monogenic-inherited disorders: ß-thalassemia and sickle cell disease. The high frequency of these diseases and the relative accessibility of hematopoietic stem cells make them an ideal candidate for therapeutic interventions based on genome editing. These strategies move in two directions: the correction of the disease-causing mutation and the reactivation of the expression of HbF in adult cells, in the attempt to recreate the effect of hereditary persistence of fetal hemoglobin (HPFH) natural mutations, which mitigate the severity of ß-hemoglobinopathies. Both lines of research rely on the knowledge gained so far on the regulatory mechanisms controlling the differential expression of globin genes during development.
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Amyotrophic lateral sclerosis (ALS) is a relentless and fatal neurological disease characterized by the selective degeneration of motor neurons. No effective therapy is available for this disease. Several lines of evidence indicate that alteration of RNA metabolism, including microRNA (miRNA) processing, is a relevant pathogenetic factor and a possible therapeutic target for ALS. Here, we showed that the abundance of components in the miRNA processing machinery is altered in a SOD1-linked cellular model, suggesting consequent dysregulation of miRNA biogenesis. Indeed, high-throughput sequencing of the small RNA fraction showed that among the altered miRNAs, miR-129-5p was increased in different models of SOD1-linked ALS and in peripheral blood cells of sporadic ALS patients. We demonstrated that miR-129-5p upregulation causes the downregulation of one of its targets: the RNA-binding protein ELAVL4/HuD. ELAVL4/HuD is predominantly expressed in neurons, where it controls several key neuronal mRNAs. Overexpression of pre-miR-129-1 inhibited neurite outgrowth and differentiation via HuD silencing in vitro, while its inhibition with an antagomir rescued the phenotype. Remarkably, we showed that administration of an antisense oligonucleotide (ASO) inhibitor of miR-129-5p to an ALS animal model, SOD1 (G93A) mice, result in a significant increase in survival and improved the neuromuscular phenotype in treated mice. These results identify miR-129-5p as a therapeutic target that is amenable to ASO modulation for the treatment of ALS patients.
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Esclerosis Amiotrófica Lateral/tratamiento farmacológico , Esclerosis Amiotrófica Lateral/metabolismo , MicroARNs/antagonistas & inhibidores , MicroARNs/metabolismo , Esclerosis Amiotrófica Lateral/genética , Animales , Modelos Animales de Enfermedad , Regulación hacia Abajo , Proteína 4 Similar a ELAV , Humanos , Ratones , MicroARNs/genética , Oligonucleótidos Antisentido/farmacología , Superóxido Dismutasa-1 , Regulación hacia ArribaRESUMEN
We observed that binding sites for the ubiquitously expressed transcription factor CP2 were present in regulatory regions of multiple erythroid genes. In these regions, the CP2 binding site was adjacent to a site for the erythroid factor GATA-1. Using three such regulatory regions (from genes encoding the transcription factors GATA-1, EKLF, and p45 NF-E2), we demonstrated the functional importance of the adjacent CP2/GATA-1 sites. In particular, CP2 binds to the GATA-1 HS2 enhancer, generating a ternary complex with GATA-1 and DNA. Mutations in the CP2 consensus greatly impaired HS2 activity in transient transfection assays with K562 cells. Similar results were obtained by transfection of EKLF and p45 NF-E2 mutant constructs. Chromatin immunoprecipitation with K562 cells showed that CP2 binds in vivo to all three regulatory elements and that both GATA-1 and CP2 were present on the same GATA-1 and EKLF regulatory elements. Adjacent CP2/GATA-1 sites may represent a novel module for erythroid expression of a number of genes. Additionally, coimmunoprecipitation and glutathione S-transferase pull-down experiments demonstrated a physical interaction between GATA-1 and CP2. This may contribute to the functional cooperation between these factors and provide an explanation for the important role of ubiquitous CP2 in the regulation of erythroid genes.
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Factor de Transcripción GATA1/metabolismo , Regulación de la Expresión Génica , Regiones Promotoras Genéticas , Proteínas Represoras/metabolismo , Factores de Transcripción/metabolismo , Secuencias de Aminoácidos , Secuencia de Aminoácidos , Secuencia de Bases , Sitios de Unión , Inmunoprecipitación de Cromatina , Ensayo de Cambio de Movilidad Electroforética , Elementos de Facilitación Genéticos , Factor de Transcripción GATA1/química , Factor de Transcripción GATA1/genética , Factor de Transcripción GATA1/aislamiento & purificación , Genes Reguladores , Genes Reporteros , Glutatión Transferasa/metabolismo , Humanos , Células K562 , Factores de Transcripción de Tipo Kruppel/química , Factores de Transcripción de Tipo Kruppel/genética , Factores de Transcripción de Tipo Kruppel/metabolismo , Luciferasas/metabolismo , Datos de Secuencia Molecular , Mutación , Subunidad p45 del Factor de Transcripción NF-E2/química , Subunidad p45 del Factor de Transcripción NF-E2/genética , Subunidad p45 del Factor de Transcripción NF-E2/metabolismo , Plásmidos/genética , Unión Proteica , Proteínas Recombinantes de Fusión/metabolismo , Proteínas Represoras/química , Proteínas Represoras/genética , Proteínas Represoras/aislamiento & purificación , Factores de Transcripción/química , Factores de Transcripción/genética , Factores de Transcripción/aislamiento & purificaciónRESUMEN
In the last few years, the advent of new technological approaches has led to a better knowledge of the ontogeny of erythropoiesis during development and of the journey leading from hematopoietic stem cells (HSCs) to mature red blood cells (RBCs). Our view of a well-defined hierarchical model of hematopoiesis with a near-homogeneous HSC population residing at the apex has been progressively challenged in favor of a landscape where HSCs themselves are highly heterogeneous and lineages separate earlier than previously thought. The coordination of these events is orchestrated by transcription factors (TFs) that work in a combinatorial manner to activate and/or repress their target genes. The development of next generation sequencing (NGS) has facilitated the identification of pathological mutations involving TFs underlying hematological defects. The examples of GATA1 and KLF1 presented in this review suggest that in the next few years the number of TF mutations associated with dyserythropoietic disorders will further increase.
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SOX6 is a HMG-box transcription factor expressed in a wide range of tissues. Recent data show that SOX6 expression is altered in different cancers, in the majority of cases being downregulated. To date, no data are available about SOX6 role in hematological malignancies. Here we demonstrate that SOX6 overexpressing BCR-ABL1+ B-ALL cells are unable to promote leukemia in a mouse model. Starting from this observation, we extended our study to a panel of human leukemic cells carrying genetic lesions distinctive of different types of leukemias and myeloproliferative disorders (the BCR-ABL1 translocation and the JAK2V617F amino acid substitution) to dissect the cellular events induced by SOX6. The inhibition of proliferation is the invariant outcome of SOX6 overexpression but it is achieved via two different cellular responses: terminal differentiation in erythroid-biased cells, irrespectively of their mutation, and apoptosis in megakaryocytic-primed and lymphoid cells. Within this context, cells carrying the highest copy number of the JAK2V617F allele better counteract the SOX6-imposed growth arrest. The interrogation of the GEPIA (Gene Expression Profiling Interactive Analysis) human dataset reveals that SOX6 is downregulated in a cohort of AML patients, uncovering a wide anti-proliferative role of SOX6 in a variety of mutant backgrounds.