MiR-138 inhibits EZH2 methyltransferase expression and methylation of histone H3 at lysine 27, and affects thermotolerance acquisition

Early-life environmental effects on birds: epigenetics and microbiome as mechanisms underlying long-lasting phenotypic changes

Although the long-lasting effects of variation in early-life environment have been well documented across organisms, the underlying causal mechanisms are only recently starting to be unraveled. Yet understanding the underlying mechanisms of long-lasting effects can help us predict how organisms will respond to changing environments. Birds offer a great system in which to study developmental plasticity and its underlying mechanisms owing to the production of large external eggs and variation in developmental trajectories, combined with a long tradition of applied, physiological, ecological and evolutionary research. Epigenetic changes (such as DNA methylation) have been suggested to be a key mechanism mediating long-lasting effects of the early-life environment across taxa. More recently, changes in the early-life gut microbiome have been identified as another potential mediator of developmental plasticity. As a first step in understanding whether these mechanisms contribute to developmental plasticity in birds, this Review summarizes how changes in early-life environment (both prenatal and postnatal) influence epigenetic markers and the gut microbiome. The literature shows how both early-life biotic (such as resources and social environment) and abiotic (thermal environment and various anthropogenic stressors) factors modify epigenetic markers and the gut microbiome in birds, yet data concerning many other environmental factors are limited. The causal links of these modifications to lasting phenotypic changes are still scarce, but changes in the hypothalamic-pituitary-adrenal axis have been identified as one putative pathway. This Review identifies several knowledge gaps, including data on the long-term effects, stability of the molecular changes, and lack of diversity in the systems studied, and provides directions for future research.

Pequi Oil (Caryocar brasiliense Camb.) Attenuates the Adverse Effects of Cyclical Heat Stress and Modulates the Oxidative Stress-Related Genes in Broiler Chickens

The present study was conducted to determine the possible antioxidant protection of pequi oil (PO) against cyclic heat stress in broiler chickens and to highlight the application of PO as a promising additive in broiler feed. A total of 400 one-day-old male broiler chicks (Cobb 500) were randomly assigned to 2 × 5 factorially arranged treatments: two temperature-controlled rooms (thermoneutral-TN or heat stress-HS for 8 h/day) and five dietary PO levels (0, 1.5, 3.0, 4.5, or 6.0 g/kg diet) for 42 days. Each treatment consisted of eight replicates of five birds. The results showed that HS increased glucose (p = 0.006), triglycerides (p < 0.001), and HDL (p = 0.042) at 21 days and reduced (p = 0.005) serum total cholesterol at 42 days. The results also showed that HS increased the contents of alanine aminotransferase (ALT) and aspartate aminotransferase (AST). In contrast, PO linearly decreased AST (p = 0.048) and ALT (p = 0.020) at 21 and 42 days, respectively. The heterophil-to-lymphocyte ratio in the birds under HS was higher than in those in the TN environment (p = 0.046). Heat stress decreased (p = 0.032) the relative weight of their livers at 21 days. The superoxide dismutase activity increased (p = 0.010) in the HS treatments in comparison to the TN treatments, while the glutathione peroxidase activity in the liver decreased (p < 0.001) at 42 days; however, the activity of catalase had no significant effects. Meanwhile, increasing the dietary PO levels linearly decreased plasma malondialdehyde (p < 0.001) in the birds in the HS environment. In addition, PO reduced (p = 0.027) the expression of Hsp 70 in the liver by 92% when compared to the TN treatment without PO, mainly at the 6.0 g/kg diet level. The expression of Nrf2 was upregulated by 37% (p = 0.049) in response to PO with the 6.0 g/kg diet compared to the HS treatment without PO. In conclusion, PO supplementation alleviated the adverse effects of HS on broilers due to its antioxidant action and modulation of the genes related to oxidative stress, providing insights into its application as a potential feed additive in broiler production.

Effects of Thermal Manipulation on mRNA Regulation of Response Genes Regarding Improvement of Thermotolerance Adaptation in Chickens during Embryogenesis

The phenomenon of increasing heat stress (HS) among animals is of particular significance when it is seen in economically significant industries, such as poultry. Due to the identification of the physiological, molecular, and genetic roots of HS responses in chickens, a substantial number of studies have focused on reducing the effects of HS in poultry through environmental management, dietary manipulation, and genetic alterations. Temperature manipulation (TM) during embryogenesis has been claimed to increase the thermal tolerance and well-being of chickens without affecting their capacity for future growth. There has been little investigation into the vulnerability of the epigenome involving TM during embryogenesis, although the cellular pathways activated by HS have been explored in chickens. Epigenetic changes caused by prenatal TM enhance postnatal temperature adaption and produce physiological memory. This work offers a thorough analysis that explains the cumulative impact of HS response genes, such as genes related to heat shock proteins, antioxidants, and immunological genes, which may aid in the enhanced adaptability of chickens that have undergone thermal manipulation during their embryonic stages.

Early-life thermal stress mediates long-term alterations in hypothalamic microglia

Stressful environmental events in early life have long-lasting consequences on later stress responses. We previously showed that heat conditioning of 3-day-old chicks during the critical period of heat-response development leads to heat vulnerability later in life. Here we assessed the role of early-life heat stress on the inflammatory response in the chick anterior hypothalamus (AH), focusing on hypothalamic microglia. We identified the microglial cell population in the chick AH using anti-KUL01 and anti-CD45 antibodies. Specific microglial features were also confirmed by expression of their signature genes. Under normal environmental conditions, hypothalamic microglia isolated from lipopolysaccharide (LPS)-injected chicks displayed a classical activated proinflammatory profile accompanied by a decreased homeostatic signature, demonstrating similarity of immune response with mammalian microglial cells. In accordance with our previous observations, conditioning of 3-day-old chicks under high ambient temperature decreased the number of newborn cells in the AH, among them microglial precursors. Although heat exposure did not affect microglial cell viability, it had a long-term impact on LPS-induced inflammatory response. Exposure to harsh heat led to heat vulnerability, and attenuated recruitment of peripheral monocytes and T cells into the AH following LPS challenge. Moreover, heat conditioning altered microglial reactivity, manifested as suppressed microglial activation in response to LPS. Innate immune memory developed by heat conditioning might underlie suppression of the microglial response to LPS challenge. We describe alterations in genome-wide CpG methylation profile of hypothalamic microglia, demonstrating probable epigenetic involvement in the reprogramming of microglial function, leading to heat-induced inflammatory cross-tolerance.

Chicken embryo as a model in epigenetic research

Epigenetics is defined as the study of changes in gene function that are mitotically or meiotically heritable and do not lead to a change in DNA sequence. Epigenetic modifications are important mechanisms that fine tune the expression of genes in response to extracellular signals and environmental changes. In vertebrates, crucial epigenetic reprogramming events occur during early embryogenesis and germ cell development. Chicken embryo, which develops external to the mother's body, can be easily manipulated in vivo and in vitro, and hence, it is an excellent model for performing epigenetic studies. Environmental factors such as temperature can affect the development of an embryo into the phenotype of an adult. A better understanding of the environmental impact on embryo development can be achieved by analyzing the direct effects of epigenetic modifications as well as their molecular background and their intergenerational and transgenerational inheritance. In this overview, the current possibility of epigenetic changes during chicken embryonic development and their effects on long-term postembryonic development are discussed.

Embryonic thermal manipulation impacts the postnatal transcriptome response of heat-challenged Japanese quails

Background

The thermal-manipulation (TM) during egg incubation is a cyclic exposure to hot or cold temperatures during embryogenesis that is associated to long-lasting effects on growth performance, physiology, metabolism and temperature tolerance in birds. An increase of the incubation temperature of Japanese quail eggs affected the embryonic and post-hatch survival, growth, surface temperatures and blood characteristics potentially related to thermoregulation capacities. To gain new insights in the molecular basis of TM in quails, we investigated by RNA-seq the hypothalamus transcriptome of 35 days-old male and female quails that were treated by TM or not (C, control) during embryogenesis and that were exposed (HC) or not (RT) to a 36 °C heat challenge for 7 h before sampling.

Results

For males, 76, 27, 47 and 0 genes were differentially expressed in the CHC vs. CRT, CRT vs. TMRT, TMHC vs. TMRT and CHC vs. TMHC comparisons, respectively. For females, 17, 0, 342 and 1 genes were differentially expressed within the same respective comparisons. Inter-individual variability of gene expression response was observed particularly when comparing RT and HC female animals. The differential expression of several genes was corroborated by RT-qPCR analysis. Gene Ontology functional analysis of the differentially expressed genes showed a prevalent enrichment of terms related to cellular responses to stimuli and gene expression regulation in both sexes. Gene Ontology terms related to the membrane transport, the endoplasmic reticulum and mitochondrial functions as well as DNA metabolism and repair were also identified in specific comparisons and sexes.

Conclusions

TM had little to no effect on the regulation of gene expression in the hypothalamus of 35 days-old Japanese quails. However, the consequences of TM on gene expression were revealed by the HC, with sex-specific and common functions altered. The effects of the HC on gene expression were most prominent in TM females with a ~ 20-fold increase of the number of differentially expressed genes, suggesting that TM may enhance the gene response during challenging conditions in female quail hypothalamus. TM may also promote new cellular strategies in females to help coping to the adverse conditions as illustrated by the identification of differentially expressed genes related to the mitochondrial and heat-response functions.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12864-021-07832-7.

Beyond maternal care: The effects of extra-maternal influences within the maternal environment on offspring neurodevelopment and later-life behavior

The early-life maternal environment has a profound and persistent effect on offspring neuroendocrine function, neurotransmitter systems, and behavior. Studies using rodent models suggest that early-life maternal care can influence the 'developmental programming' of offspring in part through altered epigenetic regulation of specific genes. The exploration of epigenetic regulation of these genes as a biological mechanism has been important to our understanding of how animals adapt to their environments and how these developmental trajectories may be altered. However, other non-maternal factors have been shown to act directly, or to interact with maternal care, to influence later-life phenotype. Based on accumulating evidence, including our research, we discuss other important influences on the developmental programming of offspring. We highlight early-life variations in temperature exposure and offspring genotype x environment interactions as prominent examples. We conclude with recommendations for future investigations on how early-life maternal care and extra-maternal influences lead to persistent changes in the brain and behavior of the offspring throughout development.

Global miRNA/proteomic analyses identify miRNAs at 14q32 and 3p21, which contribute to features of chronic iron-exposed fallopian tube epithelial cells

Malignant transformation of fallopian tube secretory epithelial cells (FTSECs) is a key contributing event to the development of high-grade serous ovarian carcinoma (HGSOC). Our recent findings implicate oncogenic transformative events in chronic iron-exposed FTSECs, including increased expression of oncogenic mediators, increased telomerase transcripts, and increased growth/migratory potential. Herein, we extend these studies by implementing an integrated transcriptomic and mass spectrometry-based proteomics approach to identify global miRNA and protein alterations, for which we also investigate a subset of these targets to iron-induced functional alterations. Proteomic analysis identified > 4500 proteins, of which 243 targets were differentially expressed. Sixty-five differentially expressed miRNAs were identified, of which 35 were associated with the “top” proteomic molecules (> fourfold change) identified by Ingenuity Pathway Analysis. Twenty of these 35 miRNAs are at the 14q32 locus (encoding a cluster of 54 miRNAs) with potential to be regulated by DNA methylation and histone deacetylation. At 14q32, miR-432-5p and miR-127-3p were ~ 100-fold downregulated whereas miR-138-5p was 16-fold downregulated at 3p21 in chronic iron-exposed FTSECs. Combinatorial treatment with methyltransferase and deacetylation inhibitors reversed expression of these miRNAs, suggesting chronic iron exposure alters miRNA expression via epigenetic alterations. In addition, PAX8, an important target in HGSOC and a potential miRNA target (from IPA) was epigenetically deregulated in iron-exposed FTSECs. However, both PAX8 and ALDH1A2 (another IPA-predicted target) were experimentally identified to be independently regulated by these miRNAs although TERT RNA was partially regulated by miR-138-5p. Interestingly, overexpression of miR-432-5p diminished cell numbers induced by long-term iron exposure in FTSECs. Collectively, our global profiling approaches uncovered patterns of miRNA and proteomic alterations that may be regulated by genome-wide epigenetic alterations and contribute to functional alterations induced by chronic iron exposure in FTSECs. This study may provide a platform to identify future biomarkers for early ovarian cancer detection and new targets for therapy.

Cross-tolerance: embryonic heat conditioning induces inflammatory resilience by affecting different layers of epigenetic mechanisms regulating IL6 expression later in life

A stressor can induce resilience in another, different stressor, a phenomenon known as cross-tolerance. To learn if cross-tolerance is governed by epigenetic regulation, we used embryonic heat conditioning (EHC) in chicks, during the development of the hypothalamus, to increase the immunization response. Indeed, EHC induced a lifelong systemic antibody response to immunization, in addition to reduced hypothalamic IL6 inflammatory expression following LPS challenge. Since the outcome of EHC was long-term cross-tolerance with the immune system, we studied possible epigenetic mechanisms. We first analysed the methylation and hydroxymethylation patterns of IL6. We found reduced hydroxymethylation on IL6 intron 1 in the EHC group, a segment enriched with CpGs and NFkB-binding sites. Luciferase assay in cell lines expressing NFkB showed that IL6 intron 1 is indeed an enhancer. ChiP in the same segment against NFkB in the hypothalamus presented reduced binding to IL6 intron 1 in the EHC group, before and during LPS challenge. In parallel, EHC chicks' IL6 intron 1 presented increased H3K27me3, a repressive translational modification mediated by EZH2. This histone modification occurred during embryonic conditioning and persisted later in life. Moreover, we showed reduced expression of miR-26a, which inhibits EZH2 transcription, during conditioning along with increased EZH2 expression. We demonstrate that stress cross-tolerance, which was indicated by EHC-induced inflammatory resilience and displayed by attenuated inflammatory expression of IL6, is regulated by different epigenetic layers.

Early-Life m6A RNA Demethylation by Fat Mass and Obesity-Associated Protein (FTO) Influences Resilience or Vulnerability to Heat Stress Later in Life

Early life heat stress leads to either resilience or vulnerability to a similar stress later in life. We have previously shown that this tuning of the stress response depends on neural network organization in the preoptic anterior hypothalamus (PO/AH) thermal response center and is regulated by epigenetic mechanisms. Here, we expand our understanding of stress response establishment describing a role for epitranscriptomic regulation of the epigenetic machinery. Specifically, we explore the role of N⁶-methyladenosine (m⁶A) RNA methylation in long-term response to heat stress. Heat conditioning of 3-d-old chicks diminished m⁶A RNA methylation in the hypothalamus, simultaneously with an increase in the mRNA levels of the m⁶A demethylase, fat mass and obesity-associated protein (FTO). Moreover, a week later, methylation of two heat stress-related transcripts, histone 3 lysine 27 (H3K27) methyltransferase, enhancer of zeste homolog 2 (EZH2) and brain-derived neurotrophic factor (BDNF), were downregulated in harsh-heat-conditioned chicks. During heat challenge a week after conditioning, there was a reduction of m⁶A levels in mild-heat-conditioned chicks and an elevation in harsh-heat-conditioned ones. This increase in m⁶A modification was negatively correlated with the expression levels of both BDNF and EZH2. Antisense “knock-down” of FTO caused an elevation of global m⁶A RNA methylation, reduction of EZH2 and BDNF mRNA levels, and decrease in global H3K27 dimethylation as well as dimethyl H3K27 level along BDNF coding region, and, finally, led to heat vulnerability. These findings emphasize the multilevel regulation of gene expression, including both epigenetic and epitranscriptomic regulatory mechanisms, fine-tuning the neural network organization in a response to stress.

Circular RNA SAMD4A controls adipogenesis in obesity through the miR-138-5p/EZH2 axis

A growing body of evidence has suggested that circular RNAs (circRNAs) are crucial for the regulation of gene expression and their dysregulation is implicated in several diseases. However, the function of circRNAs in obesity remains largely unexplored.

Methods: Global changes in the circRNA expression patterns were detected in adipose tissues derived from obese and lean individuals. In particular, circSAMD4A was identified as significantly differentially upregulated and was functionally analyzed, both in vitro and in vivo, using various approaches.

Results: CircSAMD4A overexpression was correlated with a poor prognosis in obese patients. By contrast, circSAMD4A knockdown inhibited differentiation in isolated preadipocytes. In high-fat diet (HFD) -induced obese mice, circSAMD4A knockdown reversed the associated weight gain, reduced food intake, lower body fat, and increased energy expenditure. These mice also exhibited increased insulin sensitivity and glucose tolerance. Furthermore, in vitro experiments indicated that circSAMD4A affected differentiation by binding to miR-138-5p and regulating EZH2 expression.

Conclusions: CircSAMD4A regulated preadipocyte differentiation by acting as a miR-138-5p sponge, and thus increasing EZH2 expression. These results suggested that circSAMD4A can serve as a potential target for obesity treatments and/or as a potential prognostic marker for obese patients following bariatric surgery.

Genomic regions and pathways associated with thermotolerance in layer-type strain Taiwan indigenous chickens

This study aimed to investigate genetic markers and candidate genes associated with thermotolerance in a layer-type strain Taiwan indigenous chickens exposed to acute heat stress. One hundred and ninety-two 30-week-old roosters were subjected to acute heat stress. Changes in body temperature (BT, ΔT) were calculated by measuring the difference between the initial BT and the highest BT during heat stress and the results were categorized into dead, susceptible, tolerant, and intermediate groups depending on their survival and ΔT values at the end of the experiment. A genome-wide association study on survival and ΔT values was conducted using the Cochran-Armitage trend test and Fisher's exact test. Association analyses identified 80 significant SNPs being annotated to 23 candidate genes, 440 SNPs to 71 candidate genes, 64 SNPs to 25 candidate genes, and 378 SNPs to 78 candidate genes in the dead versus survivor, tolerant versus susceptible, intermediate versus tolerant, and intermediate versus susceptible groups, respectively. The annotated genes were associated with apoptosis, cellular stress responses, DNA repair, and metabolic oxidative stress. In conclusion, the identified SNPs of candidate genes provide insights into the potential mechanisms underlying physiological responses to acute heat stress in chickens.

Thermal Manipulation During Embryogenesis Impacts H3K4me3 and H3K27me3 Histone Marks in Chicken Hypothalamus

Changes in gene activity through epigenetic alterations induced by early environmental challenges during embryogenesis are known to impact the phenotype, health, and disease risk of animals. Learning how environmental cues translate into persisting epigenetic memory may open new doors to improve robustness and resilience of developing animals. It has previously been shown that the heat tolerance of male broiler chickens was improved by cyclically elevating egg incubation temperature. The embryonic thermal manipulation enhanced gene expression response in muscle (P. major) when animals were heat challenged at slaughter age, 35 days post-hatch. However, the molecular mechanisms underlying this phenomenon remain unknown. Here, we investigated the genome-wide distribution, in hypothalamus and muscle tissues, of two histone post-translational modifications, H3K4me3 and H3K27me3, known to contribute to environmental memory in eukaryotes. We found 785 H3K4me3 and 148 H3K27me3 differential peaks in the hypothalamus, encompassing genes involved in neurodevelopmental, metabolic, and gene regulation functions. Interestingly, few differences were identified in the muscle tissue for which differential gene expression was previously described. These results demonstrate that the response to embryonic thermal manipulation (TM) in chicken is mediated, at least in part, by epigenetic changes in the hypothalamus that may contribute to the later-life thermal acclimation.

Interplay of miR-137 and EZH2 contributes to the genome-wide redistribution of H3K27me3 underlying the Pb-induced memory impairment

Compromised learning and memory is a common feature of multiple neurodegenerative disorders. A paradigm spatial memory impairment could be caused by developmental lead (Pb) exposure. Growing evidence implicates epigenetic modifications in the Pb-mediated memory deficits; however, how histone modifications exemplified by H3K27me3 (H3 Lys27 trimethylation) contribute to this pathogenesis remains poorly understood. Here we found that Pb exposure diminished H3K27me3 levels in vivo by suppressing EZH2 (enhancer of zeste homolog 2) expression at an early stage. EZH2 overexpression in Pb-treated rats rescued the H3K27me3 abundance and partially restored the normal spatial memory, as manifested by the rat performance in a Morris water maze test, and structural analysis of hippocampal spine densities. Furthermore, miR-137 and EZH2 constitute mutually inhibitory loop to regulate the H3K27me3 level, and this feedback regulation could be specifically activated by Pb treatment. Considering genes targeted by H3K27me3, ChIP-chip (chromatin immunoprecipitation on chip) studies revealed that Pb could remodel the genome-wide distribution of H3K27me3, represented by pathways like transcriptional regulation, developmental regulation, cell motion, and apoptosis, as well as a novel Wnt9b locus. As a Wnt isoform associated with canonical and noncanonical signaling, Wnt9b was regulated by the opposite modifications of H3K4me3 (H3 Lys4 trimethylation) and H3K27me3 in Pb-exposed neurons. Rescue trials further validated the contribution of Wnt9b to Pb-induced neuronal impairments, wherein canonical or noncanonical Wnt signaling potentially exhibited destructive or protective roles, respectively. In summary, the study reveals an epigenetic-based molecular change underlying Pb-triggered spatial memory deficits, and provides new potential avenues for our understanding of neurodegenerative diseases with environmental etiology.

Epigenetics in natural animal populations

Phenotypic plasticity is an important mechanism for populations to buffer themselves from environmental change. While it has long been appreciated that natural populations possess genetic variation in the extent of plasticity, a surge of recent evidence suggests that epigenetic variation could also play an important role in shaping phenotypic responses. Compared with genetic variation, epigenetic variation is more likely to have higher spontaneous rates of mutation and a more sensitive reaction to environmental inputs. In our review, we first provide an overview of recent studies on epigenetically encoded thermal plasticity in animals to illustrate environmentally-mediated epigenetic effects within and across generations. Second, we discuss the role of epigenetic effects during adaptation by exploring population epigenetics in natural animal populations. Finally, we evaluate the evolutionary potential of epigenetic variation depending on its autonomy from genetic variation and its transgenerational stability. Although many of the causal links between epigenetic variation and phenotypic plasticity remain elusive, new data has explored the role of epigenetic variation in facilitating evolution in natural populations. This recent progress in ecological epigenetics will be helpful for generating predictive models of the capacity of organisms to adapt to changing climates.

MiR-26a and miR-138 block the G1/S transition by targeting the cell cycle regulating network in prostate cancer cells

PURPOSE

The tumor-suppressive microRNAs miR-26a and miR-138 are significantly down-regulated in prostate cancer (PCa) and have been identified as direct regulators of enhancer of zeste homolog 2 (EZH2), which is a known oncogene in PCa. In the present study, the influence of miR-26a and miR-138 on EZH2 and cellular function including the impact on the cell cycle regulating network was evaluated in PCa cells.

METHODS

PC-3 and DU-145 PCa cells were transfected with 100 nM of miRNA mimics, siRNA against EZH2 (siR-EZH2) or control constructs for 4 h. Analyses of gene expression and cellular function were conducted 48 h after transfection.

RESULTS

Both miRNAs influenced the EZH2 expression and activity only marginally, whereas siR-EZH2 led to a notable decrease of the EZH2 expression and activity. Both miRNAs inhibited short- and/or long-term proliferation of PCa cells but showed no effect on viability and apoptosis. In PC-3 cells, miR-26a and miR-138 caused a significant surplus of cells in the G0/G1 phase of 6 and 12 %, respectively, thus blocking the G1/S-phase transition. Treatment with siR-EZH2 was without substantial influence on cellular function and cell cycle. Therefore, alternative target genes involved in cell cycle regulation were identified in silico. MiR-26a significantly diminished the expression of its targets CCNE1, CCNE2 and CDK6, whereas CCND1, CCND3 and CDK6 were suppressed by their regulator miR-138.

CONCLUSIONS

The present findings suggest an anti-proliferative role for miR-26a and miR-138 in PCa by blocking the G1/S-phase transition independent of EZH2 but via a concerted inhibition of crucial cell cycle regulators.

Thermal manipulation of the chicken embryo triggers differential gene expression in response to a later heat challenge

Background

Meat type chickens have limited capacities to cope with high environmental temperatures, this sometimes leading to mortality on farms and subsequent economic losses. A strategy to alleviate this problem is to enhance adaptive capacities to face heat exposure using thermal manipulation (TM) during embryogenesis. This strategy was shown to improve thermotolerance during their life span. The aim of this study was to determine the effects of TM (39.5 °C, 12 h/24 vs 37.8 °C from d7 to d16 of embryogenesis) and of a subsequent heat challenge (32 °C for 5 h) applied on d34 on gene expression in the Pectoralis major muscle (PM). A chicken gene expression microarray (8 × 60 K) was used to compare muscle gene expression profiles of Control (C characterized by relatively high body temperatures, Tb) and TM chickens (characterized by a relatively low Tb) reared at 21 °C and at 32 °C (CHC and TMHC, respectively) in a dye-swap design with four comparisons and 8 broilers per treatment. Real-time quantitative PCR (RT-qPCR) was subsequently performed to validate differential expression in each comparison. Gene ontology, clustering and network building strategies were then used to identify pathways affected by TM and heat challenge.

Results

Among the genes differentially expressed (DE) in the PM (1.5 % of total probes), 28 were found to be differentially expressed between C and TM, 128 between CHC and C, and 759 between TMHC and TM. No DE gene was found between TMHC and CHC broilers. The majority of DE genes analyzed by RT-qPCR were validated. In the TM/C comparison, DE genes were involved in energy metabolism and mitochondrial function, cell proliferation, vascularization and muscle growth; when comparing heat-exposed chickens to their own controls, TM broilers developed more specific pathways than C, especially involving genes related to metabolism, stress response, vascularization, anti-apoptotic and epigenetic processes.

Conclusions

This study improved the understanding of the long-term effects of TM on PM muscle. TM broilers displaying low Tb may have lower metabolic intensity in the muscle, resulting in decreased metabolic heat production, whereas modifications in vascularization may enhance heat loss. These specific changes could in part explain the better adaptation of TM broilers to heat.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-016-2661-y) contains supplementary material, which is available to authorized users.

Neural and behavioral epigenetics; what it is, and what is hype

The ability to examine epigenetic mechanisms in the brain has become readily available over the last 20 years. This has led to an explosion of research and interest in neural and behavioral epigenetics. Of particular interest to researchers, and indeed the lay public, is the possibility that epigenetic processes, such as changes in DNA-methylation and histone modification, may provide a biochemical record of environmental effects. This has led to some fascinating insights into how molecular changes in the brain can control behavior. However, some of this research has also attracted controversy and, as is dealt with here, some overblown claims. This latter problem is partly linked to the shifting sands of what is defined as 'epigenetics'. In this review, I provide an overview of what exactly epigenetics is, and what is hype, with the aim of opening up a debate as to how this exciting field moves forward.

The regulatory roles of non-coding RNAs in nerve injury and regeneration

Non-coding RNAs (ncRNAs), especially microRNAs (miRNAs) and long non-coding RNAs (lncRNAs), have attracted much attention since their regulatory roles in diverse cell processes were recognized. Emerging studies demonstrate that many ncRNAs are differentially expressed after injury to the nervous system, significantly affecting nerve regeneration. In this review, we compile the miRNAs and lncRNAs that have been reported to be dysregulated following a variety of central and peripheral nerve injuries, including acquired brain injury, spinal cord injury, and peripheral nerve injury. We also list investigations on how these miRNAs and lncRNAs exert the regulatory actions in neurodegenerative and neuroregenerative processes through different mechanisms involving their interaction with target coding genes. We believe that comprehension of the expression profiles and the possible functions of ncRNAs during the processes of nerve injury and regeneration will help understand the molecular mechanisms responsible for post-nerve-injury changes, and may contribute to the potential use of ncRNAs as a diagnostic marker and therapeutic target for nerve injury.

MicroRNA-138 promotes tau phosphorylation by targeting retinoic acid receptor alpha

Alzheimer's disease (AD) is a progressive neurodegenerative dementia characterized by Aβ deposition and neurofibrillary tangles (NFTs) composed of hyperphosphorylated tau. Emerging evidence shows that microRNAs (miRNAs) contribute to the pathogenesis of AD. Herein, we investigated the role of miR-138, a brain enriched miRNA, which is increased in AD patients. We found that miR-138 is increased in AD models, including N2a/APP and HEK293/tau cell lines. Overexpression of miR-138 activates glycogen synthase kinase-3β (GSK-3β), and increases tau phosphorylation in HEK293/tau cells. Furthermore, we confirm that retinoic acid receptor alpha (RARA) is a direct target of miR-138, and supplement of RARA substantially suppresses GSK-3β activity, and reduces tau phosphorylation induced by miR-138. In conclusion, our data suggest that miR-138 promotes tau phosphorylation by targeting the RARA/GSK-3β pathway.

MiR-138 induces renal carcinoma cell senescence by targeting EZH2 and is downregulated in human clear cell renal cell carcinoma

MiR-138 has been shown to be downregulated in various cancers, including head and neck squamous cell carcinoma (HNSCC) and clear cell renal carcinoma (ccRCC). In the present study, we aimed to reveal the mechanism of miR-138 induction of senescence in renal carcinoma cells and identify its specific target genes. We used qRT-PCR to analyze miR-138 expression levels in renal carcinoma cell lines and ccRCC samples. The activity of β-galactosidase was measured for functional analysis after miR-138 mimic transfection. To identify the targets of miR-138, we used three types of target prediction software to determine three candidate target genes. Furthermore, a 3'UTR luciferase assay was performed. Western blotting was used to detect the protein expression levels of candidate target genes. Additionally, knockdown of EZH2 by its siRNA was performed. The expression of miR-138 was downregulated in RCC cells lines and in tumor samples compared with their controls. Transfection of miR-138 mimic induced SN-12 cell senescence, decreased the protein expression of EZH2, and increased the protein expression of P16. Furthermore, miR-138 decreased the 3'UTR luciferase activity of EZH2. The knockdown of EZH2 by siRNA induced SN-12 cell senescence, decreased the protein expression level of EZH2, and increased the protein expression of P16. MiR-138 is a tumor-suppressor miRNA in ccRCC that induces SN-12 cell senescence by downregulating EZH2 expression and upregulating P16 expression.

Heat stress attenuates new cell generation in the hypothalamus: a role for miR-138

The anterior hypothalamus (Ant Hyp) of the brain serves as the main regulator of numerous homeostatic functions, among them body temperature. Fine-tuning of the thermal-response set point during the critical postnatal sensory-developmental period involves neuronal network remodeling which might also be accompanied by alterations in hypothalamic cell populations. Here we demonstrate that heat stress during the critical period of thermal-control establishment interferes with generation of new cells in the chick hypothalamus. Whereas conditioning of the 3-day-old chicks under high ambient temperatures for 24h diminished the number of newborn cells in anterior hypothalamic structures 1 week after the treatment, mild heat stress did not influence the amount of new cells. Phenotypic analysis of these newborn cells indicated a predominant decrease in non-neuronal cell precursors, i.e. cells that do not express doublecortin (DCX). Furthermore, heat challenge of 10-day-old previously high-temperature-conditioned chicks abolished hypothalamic neurogenesis and significantly decreased the number of cells of non-neural origin. As a potential regulatory mechanism for the underlying generation of new cells in the hypothalamus, we investigated the role of the microRNA (miRNA) miR-138, previously reported by us to promote hypothalamic cell migration in vitro and whose levels are reduced during heat stress. Intracranial injection into the third ventricle of miR-138 led to an increase in the number of newborn cells in the Ant Hyp, an effect which might be partially mediated by inhibition of its direct target reelin. These data demonstrate the role of ambient temperature on the generation of new cells in the hypothalamus during the critical period of thermal-control establishment and highlight the long-term effect of severe heat stress on hypothalamic cell population. Moreover, miRNAs, miR-138 in particular, can regulate new cell generation in the hypothalamus.

Transcriptome analysis of the hippocampus in novel rat model of febrile seizures

Febrile seizures (FS) are the most common type of convulsive events in infants and young children, but the precise underlying genetic mechanism remains to be explored. To investigate the underlying pathogenic factors in FS and subsequent epilepsy, alterations in gene expression between the two new strains of rats (hyperthermia-prone [HP] vs hyperthermia-resistant [HR]), were investigated by using the Whole Rat Genome Oligo Microarray. This process identified 1,140 differentially expressed genes (DEGs; 602 upregulated and 538 downregulated), which were analyzed to determine significant Gene Ontology (GO) categories, signaling pathways and gene networks. Based on the GO analyses, the modified genes are closely related to various FS pathogenesis factors, including immune and inflammatory responses and ion transport. Certain DEGs identified have not been previously examined in relation to FS pathogenesis. Among these genes is dipeptidyl peptidase 4 (DPP4), a gene closely linked to interleukin 6 (IL-6), which played a key role in the gene network analysis. Furthermore, sitagliptin, a DPP4 inhibitor significantly decreased epileptic discharge in rats, observed via electroencephalogram, suggesting an important role for DPP4 in FS. The effectiveness of sitagliptin in reducing seizure activity may occur through a mechanism that stabilizes cellular Ca²⁺ homeostasis. In addition, DPP4 expression may be regulated by DNA methylation. The hippocampal gene expression profiles in novel rat models of FS provides a large database of candidate genes and pathways, which will be useful for researchers interested in disorders of neuronal excitability.

Elevated expression of prostate cancer-associated genes is linked to down-regulation of microRNAs

Background

Recent evidence suggests that the prostate cancer (PCa)-specific up-regulation of certain genes such as AMACR, EZH2, PSGR, PSMA and TRPM8 could be associated with an aberrant expression of non-coding microRNAs (miRNA).

Methods

In silico analyses were used to search for miRNAs being putative regulators of PCa-associated genes. The expression of nine selected miRNAs (hsa-miR-101, -138, -186, -224, -26a, -26b, -374a, -410, -660) as well as of the aforementioned PCa-associated genes was analyzed by quantitative PCR using 50 malignant (Tu) and matched non-malignant (Tf) tissue samples from prostatectomy specimens as well as 30 samples from patients with benign prostatic hyperplasia (BPH). Then, correlations between paired miRNA and target gene expression levels were analyzed. Furthermore, the effect of exogenously administered miR-26a on selected target genes was determined by quantitative PCR and Western Blot in various PCa cell lines. A luciferase reporter assay was used for target validation.

Results

The expression of all selected miRNAs was decreased in PCa tissue samples compared to either control group (Tu vs Tf: -1.35 to -5.61-fold; Tu vs BPH: -1.17 to -5.49-fold). The down-regulation of most miRNAs inversely correlated with an up-regulation of their putative target genes with Spearman correlation coefficients ranging from -0.107 to -0.551. MiR-186 showed a significantly diminished expression in patients with non-organ confined PCa and initial metastases. Furthermore, over-expression of miR-26a reduced the mRNA and protein expression of its potential target gene AMACR in vitro. Using the luciferase reporter assay AMACR was validated as new target for miR-26a.

Conclusions

The findings of this study indicate that the expression of specific miRNAs is decreased in PCa and inversely correlates with the up-regulation of their putative target genes. Consequently, miRNAs could contribute to oncogenesis and progression of PCa via an altered miRNA-target gene-interaction.

Computational prediction and experimental validation of microRNAs in the brown alga Ectocarpus siliculosus

We used an in silico approach to predict microRNAs (miRNAs) genome-wide in the brown alga Ectocarpus siliculosus. As brown algae are phylogenetically distant from both animals and land plants, our approach relied on features shared by all known organisms, excluding sequence conservation, genome localization and pattern of base-pairing with the target. We predicted between 500 and 1500 miRNAs candidates, depending on the values of the energetic parameters used to filter the potential precursors. Using quantitative polymerase chain reaction assays, we confirmed the existence of 22 miRNAs among 72 candidates tested, and of 8 predicted precursors. In addition, we compared the expression of miRNAs and their precursors in two life cycle states (sporophyte, gametophyte) and under salt stress. Several miRNA precursors, Argonaute and DICER messenger RNAs were differentially expressed in these conditions. Finally, we analyzed the gene organization and the target functions of the predicted candidates. This showed that E. siliculosus miRNA genes are, like plant miRNA genes, rarely clustered and, like animal miRNA genes, often located in introns. Among the predicted targets, several widely conserved functional domains are significantly overrepresented, like kinesin, nucleotide-binding/APAF-1, R proteins and CED-4 (NB-ARC) and tetratricopeptide repeats. The combination of computational and experimental approaches thus emphasizes the originality of molecular and cellular processes in brown algae.

MicroRNA-138 and SIRT1 form a mutual negative feedback loop to regulate mammalian axon regeneration

Regulated gene expression determines the intrinsic ability of neurons to extend axons, and loss of such ability is the major reason for the failed axon regeneration in the mature mammalian CNS. MicroRNAs and histone modifications are key epigenetic regulators of gene expression, but their roles in mammalian axon regeneration are not well explored. Here we report microRNA-138 (miR-138) as a novel suppressor of axon regeneration and show that SIRT1, the NAD-dependent histone deacetylase, is the functional target of miR-138. Importantly, we provide the first evidence that miR-138 and SIRT1 regulate mammalian axon regeneration in vivo. Moreover, we found that SIRT1 also acts as a transcriptional repressor to suppress the expression of miR-138 in adult sensory neurons in response to peripheral nerve injury. Therefore, miR-138 and SIRT1 form a mutual negative feedback regulatory loop, which provides a novel mechanism for controlling intrinsic axon regeneration ability.

Epigenetics and phenotypic variability: some interesting insights from birds

Little is known about epigenetic mechanisms in birds with the exception of the phenomenon of dosage compensation of sex chromosomes, although such mechanisms could be involved in the phenotypic variability of birds, as in several livestock species. This paper reviews the literature on epigenetic mechanisms that could contribute significantly to trait variability in birds, and compares the results to the existing knowledge of epigenetic mechanisms in mammals. The main issues addressed in this paper are: (1) Does genomic imprinting exist in birds? (2) How does the embryonic environment influence the adult phenotype in avian species? (3) Does the embryonic environment have an impact on phenotypic variability across several successive generations? The potential for epigenetic studies to improve the performance of individual animals through the implementation of limited changes in breeding conditions or the addition of new parameters in selection models is still an open question.

Suppression of tumorigenicity by microRNA-138 through inhibition of EZH2-CDK4/6-pRb-E2F1 signal loop in glioblastoma multiforme

Deregulation of microRNAs (miRNAs) is implicated in tumor progression. We attempt to identify the tumor suppressive miRNA not only down-regulated in glioblastoma multiforme (GBM) but also potent to inhibit the oncogene EZH2, and then investigate the biological function and pathophysiologic role of the candidate miRNA in GBM. In this study, we show that miRNA-138 is reduced in both GBM clinical specimens and cell lines, and is effective to inhibit EZH2 expression. Moreover, high levels of miR-138 are associated with long overall and progression-free survival of GBM patients from The Cancer Genome Atlas dataset (TCGA) data portal. Ectopic expression of miRNA-138 effectively inhibits GBM cell proliferation in vitro and tumorigenicity in vivo through inducing cell cycles G1/S arrest. Mechanism investigation reveals that miRNA-138 acquires tumor inhibition through directly targeting EZH2, CDK6, E2F2 and E2F3. Moreover, an EZH2-mediated signal loop, EZH2-CDK4/6-pRb-E2F1, is probably involved in GBM tumorigenicity, and this loop can be blocked by miRNA-138. Additionally, miRNA-138 negatively correlates to mRNA levels of EZH2 and CDK6 among GBM clinical samples from both TCGA and our small amount datasets. In conclusion, our data demonstrate a tumor suppressive role of miRNA-138 in GBM tumorigenicity, suggesting a potential application in GBM therapy.

MiR-138 promotes induced pluripotent stem cell generation through the regulation of the p53 signaling

Induced pluripotent stem (iPS) cells, especially those reprogrammed from patient somatic cells, have a great potential usage in regenerative medicine. The expression of p53 has been proven as a key barrier limiting iPS cell generation, but how p53 is regulated during cell reprogramming remains unclear. In this study, we found that the ectopic expression of miR-138 significantly improved the efficiency of iPS cell generation via Oct4, Sox2, and Klf4, with or without c-Myc (named as OSKM or OSK, respectively), without sacrificing the pluripotent characteristics of the generated iPS cells. Exploration of the mechanism showed that miR-138 directly targeted the 3' untranslated region (UTR) of p53, significantly decreasing the expression of p53 and its downstream genes. Furthermore, the ectopic expression of p53 having a mutant 3'-UTR, which cannot be bound by miR-138, seriously impaired the effect of miR-138 on p53 signaling and OSKM-initiated somatic cell reprogramming. Combined with the fact that miR-138 is endogenously expressed in fibroblasts, iPS cells, and embryonic stem cells, our study demonstrated that regulation of the p53 signaling pathway and promotion of iPS cell generation represent an unrevealed important function of miR-138.

Role of microRNA-138 as a potential tumor suppressor in head and neck squamous cell carcinoma

Head and neck squamous cell carcinoma (HNSCC) is an aggressive life-threatening disease associated with high mortality rates. While efforts have been made to explore the molecular mechanisms that contribute to the initiation and progression of HNSCC, most studies focus on protein-coding genes. Understanding of the genomic aberrations associated with noncoding genes (such as microRNAs) and their effects on HNSCC is still relatively limited. Recent evidence suggests that deregulation of microRNA genes (such as downregulation of miR-138) plays an important role in HNSCC. While deregulation of miR-138 has been frequently observed in HNSCC and other cancer types, the precise roles of miR-138 in tumorigenesis remain elusive. Recent bioinformatics analyses and functional studies using in vitro and in vivo systems have identified a number of functional targets for miR-138. These include genes that participate in essential biological processes that are highly relevant to the initiation and progression of HNSCC, including cell migration, epithelial to mesenchymal transition, cell cycle progression, DNA damage response and repair, senescence, and differentiation. However, the biological systems, study design, and data interpretation from these studies are highly variable, which hinder our understanding of the role of miR-138 in tumorigenesis at molecular level. In this review, we will first introduce the significance of microRNA deregulation in HNSCC. We will then provide a comprehensive review and integrative analysis of the existing studies on miR-138, and aim to define its molecular mechanisms that contribute to the initiation and progression of HNSCC.

Evaluating the microRNA targeting sites by luciferase reporter gene assay

MicroRNAs are post-transcriptional regulators that control mRNA stability and the translation efficiency of their target genes. Mature microRNAs are approximately 22-nucleotide in length. They mediate post-transcriptional gene regulation by binding to the imperfect complementary sequences (a.k.a. microRNA regulatory elements, MRE) in the target mRNAs. It is estimated that more than one-third of the protein-coding genes in the human genome are regulated by microRNAs. The experimental methods to examine the interaction between the microRNA and its targeting site(s) in the mRNA are important for understanding microRNA functions. The luciferase reporter gene assay has recently been adapted to test the effect of microRNAs. In this chapter, we use a previously identified miR-138 targeting site in the 3'-untranslated region (3'-UTR) of the RhoC mRNA as an example to describe a quick method for testing the interaction of microRNA and mRNA.

MicroRNA-98 and microRNA-214 post-transcriptionally regulate enhancer of zeste homolog 2 and inhibit migration and invasion in human esophageal squamous cell carcinoma

Background

The enhancer of zeste homolog 2 (EZH2) was found to be overexpressed and associated with tumor metastasis in esophageal squamous cell carcinoma (ESCC). On the other hand, it was reported that miR-26a, miR-98, miR-101, miR-124, miR-138 and miR-214 could inhibit the expression of EZH2 in some tumors. However, the role of miRNAs in the regulation of EZH2 expression in human ESCC has not been documented. The aim of this study was to determine the role of these miRNAs in the regulation of tumor metastasis via EZH2 overexpression in human ESCC.

Methods and results

The expression of these miRNAs and EZH2 mRNA were examined by qPCR and the expression of EZH2 protein was detected by western blot. The role of these miRNAs in migration and invasion was studied in ESCC cell line (Eca109) transfected with miRNA mimics or cotransfected with miRNA mimics and pcDNA-EZH2 plasmid (without the 3’-UTR of EZH2). Through clinical investigation, we found that miR-98 and miR-214 expression was significantly lower in ESCC tissues than in matched normal tissues, and the expression level of miR-98 and miR-214 was inversely correlated to EZH2 protein expression and the clinical features such as pathological grade, tumor stage and lymph node metastasis in ESCC. In Eca109 cells, overexpression of miR-98 and miR-214 significantly inhibited the migration and invasion of ESCC cells, which was reversed by transfection of EZH2.

Conclusions

These findings suggest that decreased expression of miR-98 and miR-214 might promote metastasis of human ESCC by inducing accumulation of EZH2 protein.

The role of histone methyltransferase EZH2 in myelodysplastic syndromes

Previous epigenetics research in myelodysplastic syndromes (MDS) mainly focused on the DNA methylation of tumor suppressor genes. Recent studies reported that around 6% of MDS patients have several EZH2 mutations including missense, frameshift and truncated mutations. Histone methyltransferase EZH2 plays a critical role in epigenetic regulation as a bridge between histone methylation/deacetylation and DNA methylation. EZH2 is frequently overexpressed and considered to be an oncogene in cancers; nevertheless, EZH2 is considered as a candidate tumor suppressor gene in MDS due to EZH2 mutations associated with poor survival. Many questions still need further discussion. Moreover, 3-deazaneplanocin can reduce EZH2 levels and H3K27 trimethylation, and synergistic effects are seen in combination with DNA demethylation agents or histone deacetylation inhibitors. All of the above give us more chances to improve epigenetic therapy in MDS. Therefore, the molecular mechanisms of EZH2 in tumorigenesis and the role of EZH2 in MDS are studied.

MicroRNA-138 suppresses epithelial-mesenchymal transition in squamous cell carcinoma cell lines

Down-regulation of miR-138 (microRNA-138) has been frequently observed in various cancers, including HNSCC (head and neck squamous cell carcinoma). Our previous studies suggest that down-regulation of miR-138 is associated with mesenchymal-like cell morphology and enhanced cell migration and invasion. In the present study, we demonstrated that these miR-138-induced changes were accompanied by marked reduction in E-cad (E-cadherin) expression and enhanced Vim (vimentin) expression, characteristics of EMT (epithelial-mesenchymal transition). On the basis of a combined experimental and bioinformatics analysis, we identified a number of miR-138 target genes that are associated with EMT, including VIM, ZEB2 (zinc finger E-box-binding homeobox 2) and EZH2 (enhancer of zeste homologue 2). Direct targeting of miR-138 to specific sequences located in the mRNAs of the VIM, ZEB2 and EZH2 genes was confirmed using luciferase reporter gene assays. Our functional analyses (knock-in and knock-down) demonstrated that miR-138 regulates the EMT via three distinct pathways: (i) direct targeting of VIM mRNA and controlling the expression of VIM at a post-transcriptional level, (ii) targeting the transcriptional repressors (ZEB2) which in turn regulating the transcription activity of the E-cad gene, and (iii) targeting the epigenetic regulator EZH2 which in turn modulates its gene silencing effects on the downstream genes including E-cad. These results, together with our previously observed miR-138 effects on cell migration and invasion through targeting RhoC (Rho-related GTP-binding protein C) and ROCK2 (Rho-associated, coiled-coil-containing protein kinase 2) concurrently, suggest that miR-138 is a multi-functional molecular regulator and plays major roles in EMT and in HNSCC progression.

Sulforaphane suppresses polycomb group protein level via a proteasome-dependent mechanism in skin cancer cells

The polycomb group (PcG) genes encode a family of proteins that methylate and ubiquitinate histones to close chromatin and suppress gene expression. PcG proteins are present at elevated levels in cancer cells, and this is associated with reduced tumor suppressor protein level and enhanced cell survival. Agents that reduce PcG protein level are regarded as potentially cancer-preventative agents. Sulforaphane (SFN) is a biologically important isothiocyanate found in cruciferous vegetables that is an important candidate chemopreventive agent. However, the impact of SFN on the level and function of PcG proteins in skin cancer cells has not been assessed. We show that SFN treatment causes a concentration-dependent reduction in PcG protein (Bmi-1, Ezh2) expression in SCC-13 skin cancer cells and also reduces trimethylation of lysine 27 of histone H3. This is associated with accumulation of cells in G(2)/M phase; reduced levels of cyclin B1, cyclin A, cyclin dependent kinases 1 and 2; and increased p21(Cip1) expression. Sulforaphane treatment also increases cleavage of procaspase 3, 8, and 9 and enhances PARP cleavage and apoptosis. Similar results are observed in other skin-derived cell immortalized and transformed cell lines. Forced expression of the Bmi-1 polycomb protein in SCC-13 cells reverses these effects. The SFN-dependent loss of Bmi-1 and Ezh2 is due to proteasome-associated degradation. These results suggest that dietary isothiocyanates may suppress cancer progression by reducing PcG protein level via a proteasome-dependent mechanism, thereby inhibiting PcG-dependent pro-survival epigenetic events.

Minireview: The roles of small RNA pathways in reproductive medicine

The discovery of small noncoding RNA, including P-element-induced wimpy testis-interacting RNA, small interfering RNA, and microRNA, has energized research in reproductive medicine. In the two decades since the identification of small RNA, first in Caenorhabditis elegans and then in other animals, scientists in many disciplines have made significant progress in elucidating their biology. A powerful battery of tools, including knockout mice and small RNA mimics and antagonists, has facilitated investigation into the functional roles and therapeutic potential of these small RNA pathways. Current data indicate that small RNA play significant roles in normal development and physiology and pathological conditions of the reproductive tracts of females and males. Biologically plausible mRNA targets for these microRNA are aggressively being discovered. The next phase of research will focus on elucidating the clinical utility of small RNA-selective agonists and antagonists.

The role of epigenetics in resistance to Cisplatin chemotherapy in lung cancer

Non-small cell lung cancer (NSCLC) is the most common cause of cancer related death in the world. Cisplatin and carboplatin are the most commonly used cytotoxic chemotherapeutic agents to treat the disease. These agents, usually combined with drugs such as gemcitabine or pemetrexed, induce objective tumor responses in only 20-30% of patients. Aberrant epigenetic regulation of gene expression is a frequent event in NSCLC. In this article we review the emerging evidence that epigenetics and the cellular machinery involved with this type of regulation may be key elements in the development of cisplatin resistance in NSCLC.

Cell birth and survival following seasonal periods of cell proliferation in the chemosensory epithelia of red-backed salamanders, Plethodon cinereus

In addition to the continuous low levels of neurogenesis typical of adult vertebrates to replace damaged chemoreceptor cells, red-backed salamanders (Plethodon cinereus) experience an up-regulation of chemoreceptor epithelial cell proliferation on a seasonal basis. Significantly more cell division occurs in late spring than at any other time of the year, and we investigated the fate and life span of these newly generated cells. We used 5-bromo-2'-deoxyuridine (BrdU) immunocytochemical cell birth dating to examine cell proliferation and cell migration in the main olfactory and vomeronasal epithelia of red-backed salamanders collected in late spring who were allowed to survive for one hour or three, four, 25, 28, 42, 49 and 100 days post-injection. We examined new neuron growth in the vomeronasal and olfactory epithelia using antibodies against Growth Associated Protein-43 (GAP-43), a protein whose synthesis is up-regulated during axon growth. We also tracked apoptosis within both types of chemosensory epithelia using terminal deoxynucleotidyl transferase-mediated nick-end labeling (TUNEL). BrdU-immunoreactive cells were located extensively throughout the vomeronasal epithelia, particularly in the area posterior to the entrance of the nasolacrimal duct, not only after three days of survival, but also all of the longer experimental survival periods as well; BrdU-ir cells within the olfactory epithelia were rarely located after longer survival periods. Salamanders collected in late spring displayed extensive GAP-43 labeling in the vomeronasal epithelia posterior to the entrance of the nasolacrimal duct, indicating a large population of young vomeronasal receptor neurons. Finally, apoptotic cells were evident in this same post-nasolacrimal-duct-area of the vomeronasal organ and in the olfactory epithelium. We suggest that vomeronasal receptor neurons born in late spring function throughout the summer and may be associated with the animals' extensive territoriality during that period.