Mammalian embryogenesis is a complex process controlled by transcription factors that regulate the balance between pluripotency and differentiation. Transcription factor aryl hydrocarbon receptor ...(AhR) regulates OCT4/POU5F1 and NANOG, both essential controllers of pluripotency, stemness and early embryo development. Molecular mechanisms controlling OCT4/POU5F1 and NANOG during embryogenesis remain unidentified. We show that AhR regulates pluripotency factors and maintains the metabolic activity required for proper embryo differentiation. AhR-lacking embryos (AhR−/−) showed a pluripotent phenotype characterized by a delayed expression of trophectoderm differentiation markers. Accordingly, central pluripotency factors OCT4/POU5F1 and NANOG were overexpressed in AhR−/− embryos at initial developmental stages. An altered intracellular localization of these factors was observed in the absence of AhR and, importantly, Oct4 had an opposite expression pattern with respect to AhR from the two-cell stage to blastocyst, suggesting a negative regulation of OCT4/POU5F by AhR. We propose that AhR is a regulator of pluripotency and differentiation in early mouse embryogenesis.
•AhR regulates pluripotency factors OCT4 and NANOG during early embryo differentiation•AhR lacking embryos (AhR−/−) show a pluripotent phenotype•Pluripotent phenotype of AhR−/− embryos show enhanced glycolytic metabolism
In this article, Fernández-Salguero and colleagues show that transcription factor AhR regulates pluripotency factors and maintains the metabolic activity required for proper embryo differentiation. AhR-lacking embryos (AhR−/−) showed a pluripotent phenotype characterized by a delayed expression of trophectoderm differentiation markers. Accordingly, central pluripotency factors were overexpressed in AhR−/− embryos at initial developmental stages.
Understanding the cause of sex disparities in COVID-19 outcomes is a major challenge. We investigate sex hormone levels and their association with outcomes in COVID-19 patients, stratified by sex and ...age. This observational, retrospective, cohort study included 138 patients aged 18 years or older with COVID-19, hospitalized in Italy between February 1 and May 30, 2020. The association between sex hormones (testosterone, estradiol, progesterone, dehydroepiandrosterone) and outcomes (ARDS, severe COVID-19, in-hospital mortality) was explored in 120 patients aged 50 years and over. STROBE checklist was followed. The median age was 73.5 years IQR 61, 82; 55.8% were male. In older males, testosterone was lower if ARDS and severe COVID-19 were reported than if not (3.6
5.3 nmol/L, p =0.0378 and 3.7
8.5 nmol/L, p =0.0011, respectively). Deceased males had lower testosterone (2.4
4.8 nmol/L, p =0.0536) and higher estradiol than survivors (40
24 pg/mL, p = 0.0006). Testosterone was negatively associated with ARDS (OR 0.849 95% CI 0.734, 0.982), severe COVID-19 (OR 0.691 95% CI 0.546, 0.874), and in-hospital mortality (OR 0.742 95% CI 0.566, 0.972), regardless of potential confounders, though confirmed only in the regression model on males. Higher estradiol was associated with a higher probability of death (OR 1.051 95% CI 1.018, 1.084), confirmed in both sex models. In males, higher testosterone seems to be protective against any considered outcome. Higher estradiol was associated with a higher probability of death in both sexes.
Transcriptional repression of Nanog is an important hallmark of stem cell differentiation. Chromatin modifications have been linked to the epigenetic profile of the Nanog gene, but whether chromatin ...organization actually plays a causal role in Nanog regulation is still unclear. Here, we report that the formation of a chromatin loop in the Nanog locus is concomitant to its transcriptional downregulation during human NTERA-2 cell differentiation. We found that two Alu elements flanking the Nanog gene were bound by the aryl hydrocarbon receptor (AhR) and the insulator protein CTCF during cell differentiation. Such binding altered the profile of repressive histone modifications near Nanog likely leading to gene insulation through the formation of a chromatin loop between the two Alu elements. Using a dCAS9-guided proteomic screening, we found that interaction of the histone methyltransferase PRMT1 and the chromatin assembly factor CHAF1B with the Alu elements flanking Nanog was required for chromatin loop formation and Nanog repression. Therefore, our results uncover a chromatin-driven, retrotransposon-regulated mechanism for the control of Nanog expression during cell differentiation.
Recent experimental evidences from cellular systems and from mammalian and non-mammalian animal models highlight novel functions for the aryl hydrocarbon/dioxin receptor (AhR) in maintaining cell ...differentiation and tissue homeostasis. Notably, AhR depletion stimulates an undifferentiated and pluripotent phenotype likely associated to a mesenchymal transition in epithelial cells and to increased primary tumorigenesis and metastasis in melanoma. In this work, we have used a lung model of epithelial regeneration to investigate whether AhR regulates proper tissue repair by adjusting the expansion of undifferentiated stem-like cells. AhR-null mice developed a faster and more efficient repair of the lung bronchiolar epithelium upon naphthalene injury that required increased cell proliferation and the earlier activation of stem-like Clara, Basal and neuroepithelial cells precursors. Increased basal content in multipotent Sca1+/CD31−/CD4− cells and in cells expressing pluripotency factors NANOG and OCT4 could also improve re-epithelialization in AhR-null lungs. The reduced response of AhR-deficient lungs to Sonic Hedgehog (Shh) repression shortly after injury may also help their improved bronchiolar epithelium repair. These results support a role for AhR in the regenerative response against toxins, and open the possibility of modulating its activation level to favor recovery from lesions caused by environmental contaminants.
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•Dioxin receptor deficiency accelerates regeneration of the damaged lung epithelium.•Improved lung repair involves early activation of undifferentiated cell phenotypes.•Dioxin receptor may serve to adjust lung regeneration avoiding tissue overgrowth.
Resveratrol, a natural phytoalexin, has gained much interest on the basis of its potential chemopreventive activity against human cancer. In this work, using the human breast cancer cell lines MCF-7 ...and MDA-MB-231, we have analyzed a possible mechanism by which resveratrol could interfere with cell cycle control and induce cell death. Our results show that although resveratrol inhibited cell proliferation and viability in both cell lines, apoptosis was induced in a concentration- and cell-specific manner. In MDA-MB-231, resveratrol (up to 200
μM) lowered the expression and kinase activities of positive G1/S and G2/M cell cycle regulators and inhibited ribonucleotide reductase activity in a concentration dependent manner, without a significant effect on the low expression of tumor suppressors p21, p27, and p53. These cells died by a non-apoptotic process in the absence of a significant change in cell cycle distribution. In MCF-7, resveratrol produced a significant and transient (<50
μM) increase in the expression and kinase activities of positive G1/S and G2/M regulators. Simultaneously, p21 expression was markedly induced in presence of high levels of p27 and p53. These opposing effects resulted in cell cycle blockade at the S-phase and apoptosis induction in MCF-7 cells. Thus, the antiproliferative activity of resveratrol could take place through the differential regulation of the cell cycle leading to apoptosis or necrosis. This could be influenced, among other factors, by the concentration of this molecule and by the characteristics of the target cell.
2,3,7,8-Tetrachlorodibenzo-
p-dioxin (TCDD) is a potent toxicant that alters normal brain development and produces cognitive disability and motor dysfunction. However, after decades of intense study, ...the molecular mechanisms of TCDD-induced neurotoxicity, the signaling pathways involved and its molecular targets in neurons still remain unknown. TCDD acts as an exogenous ligand of the aryl hydrocarbon receptor (AhR) that becomes a key signaling molecule in the regulation of the toxic and carcinogenic properties of TCDD. We have used NGF-differentiated pheochromocytoma (dPC12) cells to determine the type of cell death that takes place by TCDD toxicity. TCDD induced cell death in dPC12 cultures with an EC
50 of 218
±
24
nM, similar to that obtained in undifferentiated PC12 cells, 171
±
31
nM. Nuclear fragmentation was observed after TCDD incubation in parallel to an increase in caspase-3 activity. Staurosporine, which readily induced apoptosis in dPC12 cells, showed a similar increase in caspase-3 activity and the characteristic pattern of nuclear fragmentation. Flow cytometry measurements showed that dPC12 cells in the presence of TCDD were positive for annexin V labeling but negative for propidium iodide staining. In addition, TCDD increased the area of the peak corresponding to hypodiploid (apoptotic) DNA content. All together these results support the hypothesis that TCDD toxicity in dPC12 cells takes place mainly through an apoptotic process.
The intrinsic features of retroelements, like their repetitive nature and disseminated presence in their host genomes, demand the use of advanced methodologies for their bioinformatic and functional ...study. The short length of SINE (short interspersed elements) retrotransposons makes such analyses even more complex. Next-generation sequencing (NGS) technologies are currently one of the most widely used tools to characterize the whole repertoire of gene expression in a specific tissue. In this chapter, we will review the molecular and computational methods needed to perform NGS analyses on SINE elements. We will also describe new methods of potential interest for researchers studying repetitive elements. We intend to outline the general ideas behind the computational analyses of NGS data obtained from SINE elements, and to stimulate other scientists to expand our current knowledge on SINE biology using RNA-seq and other NGS tools.
Aryl hydrocarbon receptor (AhR) deficiency alters tissue homeostasis. However, how AhR regulates organ maturation and differentiation remains mostly unknown. Liver differentiation entails a ...polyploidization process fundamental for cell growth, metabolism, and stress responses. Here, we report that AhR regulates polyploidization during the preweaning-to-adult mouse liver maturation. Preweaning AhR-null (AhR−/−) livers had smaller hepatocytes, hypercellularity, altered cell cycle regulation, and enhanced proliferation. Those phenotypes persisted in adult AhR−/− mice and correlated with compromised polyploidy, predominance of diploid hepatocytes, and enlarged centrosomes. Phosphatidylinositol-3-phosphate kinase (PI3K), extracellular signal-regulated kinase (ERK), and Wnt/β-catenin signaling remained upregulated from preweaning to adult AhR-null liver, likely increasing mammalian target of rapamycin (mTOR) activation. Metabolomics revealed the deregulation of mitochondrial oxidative phosphorylation intermediates succinate and fumarate in AhR−/− liver. Consistently, PI3K, ERK, and Wnt/β-catenin inhibition partially rescued polyploidy in AhR−/− mice. Thus, AhR may integrate survival, proliferation, and metabolism for liver polyploidization. Since tumor cells tend to be polyploid, AhR modulation could have therapeutic value in the liver.
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•AhR is required for liver polyploidization during preweaning-to-adult transition•INS-R/PI3K/AKT, ERK, Wnt/β-Cat and mTOR are downregulated during liver polyploidization•Reduced polyploidy relates with enhanced mitochondrial metabolism in AhR-null liver•Understanding how AhR modulates polyploidy may provide strategies against cancer
Developmental Biology; Cancer Systems Biology; Metabolomics
Transcription factor aryl hydrocarbon receptor (AHR) has emerged as one of the main regulators involved both in different homeostatic cell functions and tumor progression. Being a member of the ...family of basic-helix-loop-helix (bHLH) transcriptional regulators, this intracellular receptor has become a key member in differentiation, pluripotency, chromatin dynamics and cell reprogramming processes, with plenty of new targets identified in the last decade. Besides this role in tissue homeostasis, one enthralling feature of AHR is its capacity of acting as an oncogene or tumor suppressor depending on the specific organ, tissue and cell type. Together with its well-known modulation of cell adhesion and migration in a cell-type specific manner in epithelial-mesenchymal transition (EMT), this duality has also contributed to the arise of its clinical interest, highlighting a new potential as therapeutic tool, diagnosis and prognosis marker. Therefore, a deregulation of AHR-controlled pathways may have a causal role in contributing to physiological and homeostatic failures, tumor progression and dissemination. With that firmly in mind, this review will address the remarkable capability of AHR to exert a different function influenced by the phenotype of the target cell and its potential consequences.
Aryl hydrocarbon receptor (Ahr) is a transcriptional factor involved in detoxification responses to pollutants and in intrinsic biological processes of multicellular organisms. We recently described ...that Vav3, an activator of Rho/Rac GTPases, is an Ahr transcriptional target in embryonic fibroblasts. These results prompted us to compare the Ahr−/− and Vav3−/− mouse phenotypes to investigate the implications of this functional interaction in vivo. Here, we show that Ahr is important for Vav3 expression in kidney, lung, heart, liver, and brainstem regions. This process is not affected by the administration of potent Ahr ligands such as benzoapyrene. We also report that Ahr- and Vav3-deficient mice display hypertension, tachypnea, and sympathoexcitation. The Ahr gene deficiency also induces the GABAergic transmission defects present in the Vav3−/− ventrolateral medulla, a main cardiorespiratory brainstem center. However, Ahr−/− mice, unlike Vav3-deficient animals, display additional defects in fertility, perinatal growth, liver size and function, closure, spleen size, and peripheral lymphocytes. These results demonstrate that Vav3 is a bona fide Ahr target that is in charge of a limited subset of the developmental and physiological functions controlled by this transcriptional factor. Our data also reveal the presence of sympathoexcitation and new cardiorespiratory defects in Ahr−/− mice.
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