Epigenetic regulation of Cyprinus carpio ribosomal cistron during the acclimatization process

Ribosomal RNA synthesis is the major transcriptional activity in a cell, required for ribosome biogenesis, and it is critical to ensure the supply of ribosomal RNA in order to meet the cellular needs for protein synthesis. Considerable evidence indicates that epigenetics is an important regulatory mechanism for this intricate process. In addition, cells must also have the ability to maintain their functions by constantly sensing and adapting to environmental variations (homeostasis). Seasonal acclimatization of the fish Cyprinus carpio (common carp) requires the implementation of complex molecular and cellular mechanisms to coordinate “phenotypic plasticity.” This process involves a reprogramming of gene expression, which in turn integrates the homeostatic response. Our laboratory has reported that in different cell types of the carp, the nucleolus undergoes a dramatic rearrangement of its molecular structure. During winter, fibrillar and granular components of the nucleolus are segregated and surrounded by a thick layer of heterochromatin, which is an ultrastructural feature accompanied by a transient repression of ribosomal RNA transcription. In contrast, this condition is reversed during the summer, and is associated with a recovery of active ribosomal biosynthesis. Thus, the process of seasonal adaptation in the carp certainly involves a fine modulation of the transcriptional activity of ribosomal genes (rDNA). Recent studies on the regulation of ribosomal genes indicate that the numerous copies of rDNA are comprised of at least two distinct transcriptional states: active or silenced. The two states can be differentiated by their chromatin configuration and may require specific triggers to be interconverted. Thus, the use of epigenetic mechanisms to control chromatin architecture may represent an important strategy to modulate and switch the transcriptional activity of rDNA during seasonal adaptation. In this context, the protein TTF-I has been described as playing a central role in the transcriptional modulation of ribosomal genes through its interaction with epigenetic modifiers, such as the nucleolar remodeling complex (NoRC), thus playing an active role in the silencing of rDNA transcription. Most of the conclusions regarding regulatory mechanisms that control rRNA transcription have been proposed based on in vitro approaches. Thus, the natural cyclic modulation of rRNA transcriptional activity observed during carp acclimatization emerges as a valuable model towards studying the overall phenomenon in a living organism. Therefore, the general purpose of this thesis consists in studying the epigenetic regulation of the ribosomal cistron during the acclimatization process of the Cyprinus carpio. Consequently, our hypothesis proposes that "The factor TTF-I and the chromatin remodeling complex NoRC contribute significantly to the negative regulation of transcriptional expression of rRNAs during the seasonal adaptation of Cyprinus carpio.” Thus our results represent a first approach in epigenetic control involved in the expression of ribosomal genes in a natural context, where the factor TTF-I and NoRC complex play a fundamental role during the carp acclimatization process

Differential enrichment of TTF-I and Tip5 in the T-like promoter structures of the rDNA contribute to the epigenetic response of Cyprinus carpio during environmental adaptation

To ensure homeostasis, ectothermic organisms adapt to environmental variations through molecular mechanisms. We previously reported that during the seasonal acclimatization of the common carp Cyprinus carpio, molecular and cellular functions are reprogrammed, resulting in distinctive traits. Importantly, the carp undergoes a drastic rearrangement of nucleolar components during adaptation. This ultrastructural feature reflects a fine modulation of rRNA gene transcription. Specifically, we identified the involvement of the transcription termination factor I (TTF-I) and Tip-5 (member of nucleolar remodeling complex, NoRC) in the control of rRNA transcription. Our results suggest that differential Tip5 enrichment is essential for silencing carp ribosomal genes and that the T-0 element is key for regulating the ribosomal gene during the acclimatization process. Interestingly, the expression and content of Tip5 were significantly higher in winter than in summer. Since carp ribosomal gene expression is lower in the winter than in summer, and considering that expression concomitantly occurs with nucleolar ultrastructural changes of the acclimatization process, these results indicate that Tip5 importantly contributes to silencing the ribosomal genes. In conclusion, the current study provides novel evidence on the contributions of TTF-I and NoRC in the environmental reprogramming of ribosomal genes during the seasonal adaptation process in carp

The nuclear phenotypic plasticity observed in fish during rRNA regulation entails Cajal bodies dynamics.

Cajal bodies (CBs) are small mobile organelles found throughout the nucleoplasm of animal and plant cells. The dynamics of these organelles involves interactions with the nucleolus. The later has been found to play a substantial role in the compensatory response that evolved in eurythermal fish to adapt to the cyclic seasonal habitat changes, i.e., temperature and photoperiod. Contrary to being constitutive, rRNA synthesis is dramatically regulated between summer and winter, thus affecting ribosomal biogenesis which plays a central role in the acclimatization process. To examine whether CBs, up to now, never described in fish, were also sustaining the phenotypic plasticity observed in nuclei of fish undergoing seasonal acclimatization, we identified these organelles both, by transmission electronic microscopy and immunodetection with the marker protein p80-coilin. We found transcripts in all tissues analyzed. Furthermore we assessed that p80-coilin gene expression was always higher in summer-acclimatized fish when compared to that adapted to the cold season, indicating that p80-coilin expression is modulated upon seasonal acclimatization. Concurrently, CBs were more frequently found in summer-acclimatized carp which suggests that the organization of CBs is involved in adaptive processes and contribute to the phenotypic plasticity of fish cell nuclei observed concomitantly with profound reprogramming of nucleolar components and regulation of ribosomal rRNAs

The Olfactory Organ Is a Unique Site for Neutrophils in the Brain

In the vertebrate olfactory tract new neurons are continuously produced throughout life. It is widely believed that neurogenesis contributes to learning and memory and can be regulated by immune signaling molecules. Proteins originally identified in the immune system have subsequently been localized to the developing and adult nervous system. Previously, we have shown that olfactory imprinting, a specific type of long-term memory, is correlated with a transcriptional response in the olfactory organs that include up-regulation of genes associated with the immune system. To better understand the immune architecture of the olfactory organs we made use of cell-specific fluorescent reporter lines in dissected, intact adult brains of zebrafish to examine the association of the olfactory sensory neurons with neutrophils and blood-lymphatic vasculature. Surprisingly, the olfactory organs contained the only neutrophil populations observed in the brain; these neutrophils were localized in the neural epithelia and were associated with the extensive blood vasculature of the olfactory organs. Damage to the olfactory epithelia resulted in a rapid increase of neutrophils both within the olfactory organs as well as the central nervous system. Analysis of cell division during and after damage showed an increase in BrdU labeling in the neural epithelia and a subset of the neutrophils. Our results reveal a unique population of neutrophils in the olfactory organs that are associated with both the olfactory epithelia and the lymphatic vasculature suggesting a dual olfactory-immune function for this unique sensory system

Downregulation of the Polycomb-Associated Methyltransferase Ezh2 during Maturation of Hippocampal Neurons Is Mediated by MicroRNAs Let-7 and miR-124

Ezh2 is a catalytic subunit of the polycomb repressive complex 2 (PRC2) which mediates epigenetic gene silencing through depositing the mark histone H3 lysine 27 trimethylation (H3K27me3) at target genomic sequences. Previous studies have demonstrated that Enhancer of Zeste Homolog 2 (Ezh2) was differentially expressed during maturation of hippocampal neurons; in immature neurons, Ezh2 was abundantly expressed, whereas in mature neurons the expression Ezh2 was significantly reduced. Here, we report that Ezh2 is downregulated by microRNAs (miRs) that are expressed during the hippocampal maturation process. We show that, in mature hippocampal neurons, lethal-7 (let-7) and microRNA-124 (miR-124) are robustly expressed and can target cognate motifs at the 3′-UTR of the Ezh2 gene sequence to downregulate Ezh2 expression. Together, these data demonstrate that the PRC2 repressive activity during hippocampal maturation is controlled through a post-transcriptional mechanism that mediates Ezh2 downregulation in mature neurons

Long Noncoding RNA TALAM1 Is a Transcriptional Target of the RUNX2 Transcription Factor in Lung Adenocarcinoma

Background: Lung cancer is the leading cause of cancer death worldwide. It has been reported that genetic and epigenetic factors play a crucial role in the onset and evolution of lung cancer. Previous reports have shown that essential transcription factors in embryonic development contribute to this pathology. Runt-related transcription factor (RUNX) proteins belong to a family of master regulators of embryonic developmental programs. Specifically, RUNX2 is the master transcription factor (TF) of osteoblastic differentiation, and it can be involved in pathological conditions such as prostate, thyroid, and lung cancer by regulating apoptosis and mesenchymal–epithelial transition processes. In this paper, we identified TALAM1 (Metastasis Associated Lung Adenocarcinoma Transcript 1) as a genetic target of the RUNX2 TF in lung cancer and then performed functional validation of the main findings. Methods: We performed ChIP-seq analysis of tumor samples from a patient diagnosed with lung adenocarcinoma to evaluate the target genes of the RUNX2 TF. In addition, we performed shRNA-mediated knockdown of RUNX2 in this lung adenocarcinoma cell line to confirm the regulatory role of RUNX2 in TALAM1 expression. Results: We observed RUNX2 overexpression in cell lines and primary cultured lung cancer cells. Interestingly, we found that lncRNA TALAM1 was a target of RUNX2 and that RUNX2 exerted a negative regulatory effect on TALAM1 transcription

Expression of proinflammatory cytokines and receptors by human fallopian tubes in organ culture following challenge with Neisseria gonorrhoeae

Infection of the Fallopian tubes (FT) by Neisseria gonorrhoeae can lead to acute salpingitis, an inflammatory condition, which is a major cause of infertility. Challenge of explants of human FT with gonococci induced mRNA expression and protein secretion for the proinflammatory cytokines interleukin (IL)-1alpha, IL-1beta, and tumor necrosis factor alpha (TNF-alpha) but not for granulocyte-macrophage colony-stimulating factor. In contrast, FT expression of IL-6 and of the cytokine receptors IL-6R, TNF receptor I (TNF-RI), and TNF-RII was constitutive and was not increased by gonococcal challenge. These studies suggest that several proinflammatory cytokines are likely to contribute to the cell and tissue damage observed in gonococcal salpingitis

The role of long non-coding rnas in trophoblast regulation in preeclampsia and intrauterine growth restriction

10.3390/genes12070970Genes12797

An RNF12-USP26 amplification loop drives germ cell specification and is disrupted by disease-associated mutations

The E3 ubiquitin ligase RNF12 plays essential roles during development, and the gene encoding it, RLIM, is mutated in the X-linked human developmental disorder Tonne-Kalscheuer syndrome (TOKAS). Substrates of RNF12 include transcriptional regulators such as the pluripotency-associated transcriptional repressor REX1. Using global quantitative proteomics in male mouse embryonic stem cells (mESCs), we identified the deubiquitylase USP26 as a putative downstream target of RNF12 activity. RNF12 relieved REX1-mediated repression of Usp26, leading to an increase in USP26 abundance and the formation of RNF12-USP26 complexes. Interaction with USP26 prevented RNF12 autoubiquitylation and proteasomal degradation, thereby establishing a transcriptional feed-forward loop that amplified RNF12-dependent derepression of REX1 targets. We showed that the RNF12-USP26 axis operated specifically in mouse testes and was required for the expression of gametogenesis genes and for germ cell differentiation in vitro. Furthermore, this RNF12-USP26 axis was disrupted by RLIM and USP26 variants found in TOKAS and infertility patients, respectively. This work reveals synergy within the ubiquitylation cycle that controls a key developmental process in gametogenesis and that is disrupted in human genetic disorders