LIF-independent JAK signalling to chromatin in embryonic stem cells uncovered from an adult stem cell disease

Computational simulation of JAK/STAT signaling in somatic versus germline stem cells

BACKGROUND

The Janus kinase/signal transducer and activator of transcription (JAK/STAT) signaling pathway regulates a variety of cellular processes. A major activation event in this pathway involves the phosphorylation of a tyrosine of STAT, converting unphosphorylated STAT (uSTAT) to phosphorylated STAT (pSTAT), an active transcription factor. In a noncanonical role, uSTAT contributes to the maintenance of heterochromatin stability. As such, an increase in pSTAT concurrently reduces uSTAT, resulting in heterochromatin loss, as observed in Drosophila somatic tissues. Paradoxically, an opposing phenomenon occurs in Drosophila male germline stem cells (GSCs), where the JAK/STAT pathway remains persistently active due to a continuous supply of ligands. Here, computational simulations were employed to dissect JAK/STAT pathway activation under different cellular contexts, mimicking somatic and germline cells. In these simulations, ordinary differential equations were leveraged to replicate the chemical reactions governing JAK/STAT signaling under different conditions.

RESULTS

The outcomes indicate that transient ligand stimulation, typical in somatic tissues, led to a momentary reduction in uSTAT levels. Conversely, sustained ligand stimulation, a characteristic feature of the GSC niche, resulted in elevated uSTAT levels at equilibrium.

CONCLUSION

The simulation suggests that the duration of ligand exposure could explain the observed opposite effects of JAK/STAT activation on heterochromatin in somatic versus GSCs.

FERM domain-containing proteins are active components of the cell nucleus

The FERM domain is a conserved and widespread protein module that appeared in the common ancestor of amoebae, fungi, and animals, and is therefore now found in a wide variety of species. The primary function of the FERM domain is localizing to the plasma membrane through binding lipids and proteins of the membrane; thus, for a long time, FERM domain-containing proteins (FDCPs) were considered exclusively cytoskeletal. Although their role in the cytoplasm has been extensively studied, the recent discovery of the presence and importance of cytoskeletal proteins in the nucleus suggests that FDCPs might also play an important role in nuclear function. In this review, we collected data on their nuclear localization, transport, and possible functions, which are still scattered throughout the literature, with special regard to the role of the FERM domain in these processes. With this, we would like to draw attention to the exciting, new dimension of the role of FDCPs, their nuclear activity, which could be an interesting novel direction for future research.

Myosin-5 varies its steps along the irregular F-actin track

Molecular motors employ chemical energy to generate unidirectional mechanical output against a track. By contrast to the majority of macroscopic machines, they need to navigate a chaotic cellular environment, potential disorder in the track and Brownian motion. Nevertheless, decades of nanometer-precise optical studies suggest that myosin-5a, one of the prototypical molecular motors, takes uniform steps spanning 13 subunits (36 nm) along its F-actin track. Here, we use high-resolution interferometric scattering (iSCAT) microscopy to reveal that myosin takes strides spanning 22 to 34 actin subunits, despite walking straight along the helical actin filament. We show that cumulative angular disorder in F-actin accounts for the observed proportion of each stride length, akin to crossing a river on variably-spaced stepping stones. Electron microscopy revealed the structure of the stepping molecule. Our results indicate that both motor and track are soft materials that can adapt to function in complex cellular conditions.

Removal of a genomic duplication by double-nicking CRISPR restores synaptic transmission and behavior in the MyosinVA mutant mouse Flailer

Copy number variations, and particularly duplications of genomic regions, have been strongly associated with various neurodegenerative conditions including autism spectrum disorder (ASD). These genetic variations have been found to have a significant impact on brain development and function, which can lead to the emergence of neurological and behavioral symptoms. Developing strategies to target these genomic duplications has been challenging, as the presence of endogenous copies of the duplicate genes often complicates the editing strategies. Using the ASD and anxiety mouse model Flailer, that contains a duplication working as a dominant negative for MyoVa, we demonstrate the use of DN-CRISPRs to remove a 700bp genomic duplication in vitro and in vivo . Importantly, DN-CRISPRs have not been used to remove more gene regions <100bp successfully and with high efficiency. We found that editing the flailer gene in primary cortical neurons reverts synaptic transport and transmission defects. Moreover, long-term depression (LTD), disrupted in Flailer animals, is recovered after gene edition. Delivery of DN-CRISPRs in vivo shows that local delivery to the ventral hippocampus can rescues some of the mutant behaviors, while intracerebroventricular delivery, completely recovers Flailer animal phenotype associated to anxiety and ASD. Our results demonstrate the potential of DN-CRISPR to efficiently (>60% editing in vivo) remove large genomic duplications, working as a new gene therapy approach for treating neurodegenerative diseases.

IL-1β derived from mixed-polarized macrophages activates fibroblasts and synergistically forms a cancer-promoting microenvironment

BACKGROUND

Remodeling the tumor microenvironment (TME) to benefit cancer cells is crucial for tumor progression. Although diffuse-type gastric cancer (DGC) preferentially interacts with the TME, the precise mechanism of the complicated network remains unknown. This study aimed to investigate the mutual activation mechanism underlying DGC progression.

METHODS

Mass cytometry analysis of co-cultured macrophages, noncancerous fibroblasts (NFs), and DGC cells was performed. RNA sequencing was applied to examine gene expression in fibroblasts. DGC cells were treated with cytokines to examine their effect on characteristic changes. The TCGA and Kumamoto University cohorts were used to evaluate the clinical relevance of the in vitro findings.

RESULTS

Cohort analysis revealed that DGC patients had a poor prognosis. The fibroblasts and macrophages interacted with DGC cells to form a cell cluster in the invasive front of DGC tissue. The original 3D triple co-culture system determined the promotional effects of nonmalignant cells on DGC invasive growth. We notably identified a mixed-polarized macrophage cell type with M1/M2 cell surface markers in a triple co-culture system. IL-1β from mixed-polarized macrophages induced the conversion of NFs to cancer-associated fibroblast-like (CAF-like) cells, promoting the malignant phenotype of DGC cells by inducing the secretion of IL-6, IL-24, and leukemia inhibitory factor (LIF). Moreover, IL-6 and colony stimulating factor 2 (GM-CSF) cooperated to maintain the stable state of mixed-polarized macrophages. Finally, we found that mixed-polarized macrophages were frequently detected in DGC tissues.

CONCLUSION

These findings demonstrated that mixed-polarized macrophages exist as a novel subtype through the reciprocal interaction between DGC cells and nonmalignant cells.

Pharmacological Modulation of the Crosstalk between Aberrant Janus Kinase Signaling and Epigenetic Modifiers of the Histone Deacetylase Family to Treat Cancer

Hyperactivated Janus kinase (JAK) signaling is an appreciated drug target in human cancers. Numerous mutant JAK molecules as well as inherent and acquired drug resistance mechanisms limit the efficacy of JAK inhibitors (JAKi). There is accumulating evidence that epigenetic mechanisms control JAK-dependent signaling cascades. Like JAKs, epigenetic modifiers of the histone deacetylase (HDAC) family regulate the growth and development of cells and are often dysregulated in cancer cells. The notion that inhibitors of histone deacetylases (HDACi) abrogate oncogenic JAK-dependent signaling cascades illustrates an intricate crosstalk between JAKs and HDACs. Here, we summarize how structurally divergent, broad-acting as well as isoenzyme-specific HDACi, hybrid fusion pharmacophores containing JAKi and HDACi, and proteolysis targeting chimeras for JAKs inactivate the four JAK proteins JAK1, JAK2, JAK3, and tyrosine kinase-2. These agents suppress aberrant JAK activity through specific transcription-dependent processes and mechanisms that alter the phosphorylation and stability of JAKs. Pharmacological inhibition of HDACs abrogates allosteric activation of JAKs, overcomes limitations of ATP-competitive type 1 and type 2 JAKi, and interacts favorably with JAKi. Since such findings were collected in cultured cells, experimental animals, and cancer patients, we condense preclinical and translational relevance. We also discuss how future research on acetylation-dependent mechanisms that regulate JAKs might allow the rational design of improved treatments for cancer patients. SIGNIFICANCE STATEMENT: Reversible lysine-ɛ-N acetylation and deacetylation cycles control phosphorylation-dependent Janus kinase-signal transducer and activator of transcription signaling. The intricate crosstalk between these fundamental molecular mechanisms provides opportunities for pharmacological intervention strategies with modern small molecule inhibitors. This could help patients suffering from cancer.

Regulation of Embryonic Stem Cell Self-Renewal

Embryonic stem cells (ESCs) are a type of cells capable of self-renewal and multi-directional differentiation. The self-renewal of ESCs is regulated by factors including signaling pathway proteins, transcription factors, epigenetic regulators, cytokines, and small molecular compounds. Similarly, non-coding RNAs, small RNAs, and microRNAs (miRNAs) also play an important role in the process. Functionally, the core transcription factors interact with helper transcription factors to activate the expression of genes that contribute to maintaining pluripotency, while suppressing the expression of differentiation-related genes. Additionally, cytokines such as leukemia suppressor factor (LIF) stimulate downstream signaling pathways and promote self-renewal of ESCs. Particularly, LIF binds to its receptor (LIFR/gp130) to trigger the downstream Jak-Stat3 signaling pathway. BMP4 activates the downstream pathway and acts in combination with Jak-Stat3 to promote pluripotency of ESCs in the absence of serum. In addition, activation of the Wnt-FDZ signaling pathway has been observed to facilitate the self-renewal of ESCs. Small molecule modulator proteins of the pathway mentioned above are widely used in in vitro culture of stem cells. Multiple epigenetic regulators are involved in the maintenance of ESCs self-renewal, making the epigenetic status of ESCs a crucial factor in this process. Similarly, non-coding RNAs and cellular energetics have been described to promote the maintenance of the ESC's self-renewal. These factors regulate the self-renewal and differentiation of ESCs by forming signaling networks. This review focused on the role of major transcription factors, signaling pathways, small molecular compounds, epigenetic regulators, non-coding RNAs, and cellular energetics in ESC's self-renewal.

BET proteins are essential for the specification and maintenance of the epiblast lineage in mouse preimplantation embryos

Background

During mammalian preimplantation development, as the fertilized egg develops and differentiates, three cell lineages become specified: trophectoderm (TE), epiblast, and primitive endoderm (PrE). Through two steps of cell fate decisions, 16-cell blastomeres develop into TE and an inner cell mass (ICM), and thereafter, the latter differentiates into pluripotent epiblast and PrE. Although bromodomain and extra-terminal domain (BET) proteins, such as BRD4, are necessary for the transcriptional activation of genes involved in the maintenance of mouse embryonic stem cells by occupying their enhancers, their roles in the development of mouse preimplantation are unknown.

Results

To evaluate the effect of BET protein deficiency on cell lineage formation, we cultured preimplantation embryos in the presence of JQ1, which blocks the binding of BET bromodomains to acetylated-histones. We found BET inhibition blocked the transcriptional activation of genes, such as Nanog, Otx2, and Sox2, important for the formation of the epiblast lineage in blastocysts. Expression studies with lineage-specific markers in morulae and blastocysts revealed BET proteins were essential for the specification and maintenance of the epiblast lineage but were dispensable for the formation of primarily extraembryonic TE and PrE lineages. Additional Ingenuity Pathway Analysis and expression studies with a transcriptionally active form of signal transducer and activator of the transcription 3 (STAT3) suggested BET-dependent activation was partly associated with the STAT3-dependent pathway to maintain the epiblast lineage. To identify BET proteins involved in the formation of the epiblast lineage, we analyzed mutant embryos deficient in Brd4, Brd2, and double mutants. Abolishment of NANOG-positive epiblast cells was only evident in Brd4/Brd2 double-deficient morulae. Thus, the phenotype of JQ1-treated embryos is reproduced not by a Brd4- or Brd2-single deficiency, but only Brd4/Brd2-double deficiency, demonstrating the redundant roles of BRD2 and BRD4 in the specification of the epiblast lineage.

Conclusions

BET proteins are essential to the specification and maintenance of the epiblast lineage by activating lineage-specific core transcription factors during mouse preimplantation development. Among BET proteins, BRD4 plays a central role and BRD2 a complementary role in the specification and maintenance of epiblast lineages. Additionally, BET-dependent maintenance of the epiblast lineage may be partly associated with the STAT3-dependent pathway.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12915-022-01251-0.

Association of Aberrant DNA Methylation Level in the CD4 and JAK-STAT-Pathway-Related Genes with Mastitis Indicator Traits in Chinese Holstein Dairy Cattle

The present study was designed to evaluate the gene expression and DNA methylation level in the promoter region of the CD4 and the JAK-STAT-pathway-related genes. A total of 24 samples were deployed in the gene expression and 118 samples were used in the DNA methylation study. Student's t-tests were used to analyze the gene expression and DNA methylation. The evaluation of DNA methylation in promoter regions of JAK2 and STAT5A revealed hypo-methylation levels of CpG sites and higher gene expression in cows diagnosed with mastitis as compared to the healthy control, and vice versa in those with CD4. DNA methylation was negatively correlated with gene expression in JAK2, STAT5A, and CD4 genes. Six, two, and four active transcription factors were identified on the CpG sites in the promoter regions of JAK2, STAT5A, and CD4 genes, respectively. Regarding correlation analysis, the DNA methylation levels of CD4 showed significantly higher positive correlations with somatic cell counts (p < 0.05). Findings of the current study inferred that aberrant DNA methylation in the CpG sites at the 1 kb promoter region in JAK2, STAT5A, and CD4 genes due to mastitis in cows can be used as potential epigenetic markers to estimate bovine mastitis susceptibility in dairy cattle.

Functional Consequences of Mutations in Myeloproliferative Neoplasms

Driver mutations occur in Janus kinase 2 (JAK2), thrombopoietin receptor (MPL), and calreticulin (CALR) in BCR-ABL1 negative myeloproliferative neoplasms (MPNs). From mutations leading to one amino acid substitution in JAK2 or MPL, to frameshift mutations in CALR resulting in a protein with a different C-terminus, all the mutated proteins lead to pathologic and persistent JAK2-STAT5 activation. The most prevalent mutation, JAK2 V617F, is associated with the 3 entities polycythemia vera (PV), essential thrombocythemia (ET), and myelofibrosis (MF), while CALR and MPL mutations are associated only with ET and MF. Triple negative ET and MF patients may harbor noncanonical mutations in JAK2 or MPL. One major fundamental question is whether the conformations of JAK2 V617F, MPL W515K/L/A, or CALR mutants differ from those of their wild type counterparts so that a specific treatment could target the clone carrying the mutated driver and spare physiological hematopoiesis. Of great interest, a set of epigenetic mutations can co-exist with the phenotypic driver mutations in 35%–40% of MPNs. These epigenetic mutations, such as TET2, EZH2, ASXL1, or DNMT3A mutations, promote clonal hematopoiesis and increased fitness of aged hematopoietic stem cells in both clonal hematopoiesis of indeterminate potential (CHIP) and MPNs. Importantly, the main MPN driver mutation JAK2 V617F is also associated with CHIP. Accumulation of several epigenetic and splicing mutations favors progression of MPNs to secondary acute myeloid leukemia. Another major fundamental question is how epigenetic rewiring due to these mutations interacts with persistent JAK2-STAT5 signaling. Answers to these questions are required for better therapeutic interventions aimed at preventing progression of ET and PV to MF, and transformation of these MPNs in secondary acute myeloid leukemia.

CRISPR/Cas9 in epigenetics studies of health and disease

Epigenetics is the heritable phenotypic changes without altering the genotype. Epigenetic processes are such as histone methylation, acetylation, ubiquitination, sumoylation, phosphorylation, ADP ribosylation, DNA methylation and non-coding RNAs interactions associated with structural changes in chromatin. The change of structure is either open chromatin for "active" state or closed chromatin for "inactive" state, that regulates important biological phenomenon like chromatin condensation, gene expression, DNA repair, cellular development, differentiation and homeostasis, etc. However, dysregulation of epigenetic patterns causes diseases like cancer, diabetes, neurological disorder, infectious diseases, autoimmunity etc. Besides, the most important clinical uses of Epigenetics studies are i. identification of disease biomarkers and ii. development of their therapeutics. Epigenetic therapies include epi-drugs, combinatorial therapy, nanocarriers, plant-derived products that are being used for changing the epigenetic pattern to reverse gene expression. However, the developed epi- drugs cause off-target gene and transposable elements activation; promote mutagenesis and carcinogenesis in normal cells, are the major hurdles regarding their clinical use. Therefore, advanced epigenetic therapeutics are required to develop target-specific epigenetic modifications to reverse gene expression pattern. CRISPR-Cas9 (Clustered Regularly Interspaced Palindrome Repeats-associated protein 9) system-mediated gene activation mechanism paves new methods of target-specific epigenetic therapeutics to cure diseases. In this chapter, we discuss how CRISPR/Cas9 and dCas9 have recently been engineered for epigenome editing. Different strategies have been discussed used for epigenome editing based on their efficacy and complexity. Last but not least we have discussed the limitations, different uses of CRISPR/Cas9 and dCas9 in the area of genetic engineering.

LIF maintains mouse embryonic stem cells pluripotency by modulating TET1 and JMJD2 activity in a JAK2-dependent manner

The LIF-JAK2-STAT3 pathway is the central signal transducer that maintains undifferentiated mouse embryonic stem cells (mESCs), which is achieved by the recruitment of activated STAT3 to the master pluripotency genes and activation of the gene transcriptions. It remains unclear, however, how the epigenetic status required for the master gene transcriptions is built into LIF-treated mESC cultures. In this study, Jak2, but not Stat3, in the LIF canonical pathway, establishes an open epigenetic status in the pluripotency gene promoter regions. Upon LIF activation, cytosolic JAK2 was translocalized into the nucleus of mESCs, and reduced DNA methylation (5mC levels) along with increasing DNA hydroxymethylation (5hmC) in the pluripotent gene (Nanog/Pou5f1) promoter regions. In addition, the repressive histone codes H3K9m3/H3K27m3 were reduced by JAK2. Activated JAK2 directly interacted with the core epigenetic enzymes TET1 and JMJD2, modulating its activity and promotes the DNA and histone demethylation, respectively. The JAK2 effects were attained by tyrosine phosphorylation on the epigenetic enzymes. The effects of JAK2 phosphorylation on the enzymes were diverse, but all were merged to the epigenetic signatures associated with open DNA/chromatin structures. Taken together, these results reveal a previously unrecognized epigenetic regulatory role of JAK2 as an important mediator of mESC maintenance.

New insights into Vitamin C function: Vitamin C induces JAK2 activation through its receptor-like transporter SVCT2

Vitamin C (VitC) is a requisite nutrient for humans and other primates. Extensive research continuously illustrates the applications of VitC in promoting cell reprogramming, fine-tuning embryonic stem cell function, and fighting diseases. Given its chemical reduction property, VitC predominantly acts as an antioxidant to reduce reactive oxygen species (ROS) and as a cofactor for certain dioxygenases involved in epigenetic regulation. Here, we propose that VitC is also a bio-signaling molecule based on the finding that sodium-dependent VitC transporter (SVCT) 2 is a novel receptor-like transporter of VitC that possesses dual activities in mediating VitC uptake and Janus kinase (JAK) 2/signal transducer and activator of transcription (STAT) 2 signaling pathway. Through interaction, SVCT2 induces JAK2 phosphorylation while transporting VitC into cells. Activated JAK2 phosphorylates the C-terminus of SVCT2, resulting in the recruitment and activation of STAT2. As a highlight, our results suggest that the activation of JAK2 synergistically promotes regulation of VitC in ROS scavenging and epigenetic modifications through phosphorylating pyruvate dehydrogenase kinase 1, ten-eleven translocation enzyme 3, and histone H3 Tyr⁴¹. Furthermore, VitC-activated JAK2 exhibits bidirectional effects in regulating cell pluripotency and differentiation. Our results thus reveal that the SVCT2-mediated JAK2 activation facilitates VitC functions in a previously unknown manner.

Gene expression profiling of CD34(+) cells from patients with myeloproliferative neoplasms

Myeloproliferative neoplasms (MPN) are clonal disorders characterized by the increased proliferation of hematopoietic stem cell precursors and mature blood cells. Mutations of Janus kinase 2 (JAK2), Calreticulin (CALR) and MPL (myeloproliferative leukemia virus) are key driver mutations in MPN. However, the molecular profile of triple negative MPN has been a subject of ambiguity over the past few years. Mutations of, methylcytosine dioxygenase TET2, polycomb group protein ASXL1 and histone-lysine N-methyltransferase EZH2 genes have accounted for certain subsets of triple negative MPNs but the driving cause for majority of cases is still unexplored. The present study performed a microarray-based transcriptomic profile analysis of bone marrow-derived CD34(+) cells from seven MPN samples. A total of 21,448 gene signatures were obtained, which were further filtered into 472 upregulated and 202 downregulated genes. Gene ontology and protein-protein interaction (PPI) network analysis highlighted an upregulation of genes involved in cell cycle and chromatin modification in JAK2V617F negative vs. positive MPN samples. Out of the upregulated genes, seven were associated with the hematopoietic stem cell signature, while forty-seven were associated with the embryonic stem cell signature. The majority of the genes identified were under the control of NANOG and E2F4 transcription factors. The PPI network indicated a strong interaction between chromatin modifiers and cell cycle genes, such as histone-lysine N-methyltransferase SUV39H1, SWI/SNF complex subunit SMARCC2, SMARCE2, chromatin remodeling complex subunit SS18, tubulin β (TUBB) and cyclin dependent kinase CDK1. Among the upregulated epigenetic markers, there was a ~10-fold increase in MYB expression in JAK2V617F negative samples. A significant increase in total CD34 counts in JAK2V617F negative vs. positive samples (P<0.05) was also observed. Overall, the present data showed a distinct pattern of expression in JAK2V617F negative vs. positive samples with upregulated genes involved in epigenetic modification.

STAT3 Is an Upstream Regulator of Granzyme G in the Maternal-To-Zygotic Transition of Mouse Embryos

The maternal-to-zygotic transition (MZT), which controls maternal signaling to synthesize zygotic gene products, promotes the preimplantation development of mouse zygotes to the two-cell stage. Our previous study reported that mouse granzyme g (Gzmg), a serine-type protease, is required for the MZT. In this study, we further identified the maternal factors that regulate the Gzmg promoter activity in the zygote to the two-cell stage of mouse embryos. A full-length Gzmg promoter from mouse genomic DNA, FL-pGzmg (−1696~+28 nt), was cloned, and four deletion constructs of this Gzmg promoter, Δ1-pGzmg (−1369~+28 nt), Δ2-pGzmg (−939~+28 nt), Δ3-pGzmg (−711~+28 nt) and Δ4-pGzmg (−417~+28 nt), were subsequently generated. Different-sized Gzmg promoters were used to perform promoter assays of mouse zygotes and two-cell stage embryos. The results showed that Δ4-pGzmg promoted the highest expression level of the enhanced green fluorescent protein (EGFP) reporter in the zygotes and two-cell embryos. The data suggested that time-specific transcription factors upregulated Gzmg by binding cis-elements in the −417~+28-nt Gzmg promoter region. According to the results of the promoter assay, the transcription factor binding sites were predicted and analyzed with the JASPAR database, and two transcription factors, signal transducer and activator of transcription 3 (STAT3) and GA-binding protein alpha (GABPα), were identified. Furthermore, STAT3 and GABPα are expressed and located in zygote pronuclei and two-cell nuclei were confirmed by immunofluorescence staining; however, only STAT3 was recruited to the mouse zygote pronuclei and two-cell nuclei injected with the Δ4-pGzmg reporter construct. These data indicated that STAT3 is a maternal transcription factor and may upregulate Gzmg to promote the MZT. Furthermore, treatment with a STAT3 inhibitor, S3I-201, caused mouse embryonic arrest at the zygote and two-cell stages. These results suggest that STAT3, a maternal protein, is a critical transcription factor and regulates Gzmg transcription activity in preimplantation mouse embryos. It plays an important role in the maternal-to-zygotic transition during early embryonic development.

No Easy Way Out for EZH2: Its Pleiotropic, Noncanonical Effects on Gene Regulation and Cellular Function

Enhancer of zeste homolog 2 (EZH2) plays critical roles in a range of biological processes including organ development and homeostasis, epigenomic and transcriptomic regulation, gene repression and imprinting, and DNA damage repair. A widely known function of EZH2 is to serve as an enzymatic subunit of Polycomb repressive complex 2 (PRC2) and catalyze trimethylation of histone H3 lysine 27 (H3K27me3) for repressing target gene expression. However, an increasing body of evidence demonstrates that EZH2 has many "non-conventional" functions that go beyond H3K27 methylation as a Polycomb factor. First, EZH2 can methylate a number of nonhistone proteins, thereby regulating cellular processes in an H3K27me3-independent fashion. Furthermore, EZH2 relies on both methyltransferase-dependent and methyltransferase-independent mechanisms for modulating gene-expression programs and/or epigenomic patterns of cells. Importantly, independent of PRC2, EZH2 also forms physical interactions with a number of DNA-binding factors and transcriptional coactivators to context-dependently influence gene expression. The purpose of this review is to detail the complex, noncanonical roles of EZH2, which are generally less appreciated in gene and (epi)genome regulation. Because EZH2 deregulation is prevalent in human diseases such as cancer, there is increased dependency on its noncanonical function, which shall have important implications in developing more effective therapeutics.

PHB regulates meiotic recombination via JAK2-mediated histone modifications in spermatogenesis

Previously, we have shown that human sperm Prohibitin (PHB) expression is significantly negatively correlated with mitochondrial ROS levels but positively correlated with mitochondrial membrane potential and motility. However, the possible role of PHB in mammalian spermatogenesis has not been investigated. Here we document the presence of PHB in spermatocytes and its functional roles in meiosis by generating the first male germ cell-specific Phb-cKO mouse. Loss of PHB in spermatocytes resulted in complete male infertility, associated with not only meiotic pachytene arrest with accompanying apoptosis, but also apoptosis resulting from mitochondrial morphology and function impairment. Our mechanistic studies show that PHB in spermatocytes regulates the expression of STAG3, a key component of the meiotic cohesin complex, via a non-canonical JAK/STAT pathway, and consequently promotes meiotic DSB repair and homologous recombination. Furthermore, the PHB/JAK2 axis was found as a novel mechanism in the maintenance of stabilization of meiotic STAG3 cohesin complex and the modulation of heterochromatin formation in spermatocytes during meiosis. The observed JAK2-mediated epigenetic changes in histone modifications, reflected in a reduction of histone 3 tyrosine 41 phosphorylation (H3Y41ph) and a retention of H3K9me3 at the Stag3 locus, could be responsible for Stag3 dysregulation in spermatocytes with the loss of PHB.

USP9X promotes the proliferation, invasion and metastasis of liver cancer cells through regulating the JAK2/STAT3 signaling

X-linked ubiquitin-specific peptidase 9 (USP9X) serves important roles in the development and progression of various human cancers. However, its role and molecular mechanism in liver cancer require further elucidation. In the present study, USP9X was found to be upregulated in liver cancer tissues. At the same time, overexpression of USP9X promoted the proliferation, invasiveness and migration of liver cancer cells, which were subsequently suppressed by USP9X silencing. On a molecular level, the results revealed that USP9X knockdown suppressed elements of the Janus kinase 2 (JAK2)/STAT3 signaling pathway, including JAK2, STAT3, matrix metalloproteinase-2 and c-Myc. By contrast, overexpression of USP9X had the opposite effect. In conclusion, the results of the present study suggest that USP9X is upregulated in patients with liver cancer, which may accelerate the proliferation, invasiveness and migration of liver cancer cells by regulating the JAK2/STAT3 signaling pathway.

Unphosphorylated STAT3 in heterochromatin formation and tumor suppression in lung cancer

BACKGROUND

Aberrant JAK/STAT activation has been detected in many types of human cancers. The role of JAK/STAT activation in cancer has been mostly attributed to direct transcriptional regulation of target genes by phosphorylated STAT (pSTAT), while the unphosphorylated STAT (uSTAT) is believed to be dormant and reside in the cytoplasm. However, several studies have shown that uSTATs can be found in the nucleus. In addition, it has been shown that tissue-specific loss of STAT3 or STAT5 in mice promotes cancer growth in certain tissues, and thus these STAT proteins can act as tumor suppressors. However, no unifying mechanism has been shown for the tumor suppressor function of STATs to date. We have previously demonstrated a non-canonical mode of JAK/STAT signaling for Drosophila STAT and human STAT5A, where a fraction of uSTAT is in the nucleus and associated with Heterochromatin Protein 1 (HP1); STAT activation (by phosphorylation) causes its dispersal, leading to HP1 delocalization and heterochromatin loss.

METHODS

We used a combination of imaging, cell biological assays, and mouse xenografts to investigate the role of STAT3 in lung cancer development.

RESULTS

We found that uSTAT3 has a function in promoting heterochromatin formation in lung cancer cells, suppressing cell proliferation in vitro, and suppressing tumor growth in mouse xenografts.

CONCLUSIONS

Thus, uSTAT3 possesses noncanonical function in promoting heterochromatin formation, and the tumor suppressor function of STAT3 is likely attributable to the heterochromatin-promoting activity of uSTAT3 in the non-canonical JAK/STAT pathway.

The role of the thrombopoietin receptor MPL in myeloproliferative neoplasms: recent findings and potential therapeutic applications

Introduction: Classical Myeloproliferative Neoplasms (MPNs) include three disorders: Polycythemia Vera (PV), Essential Thrombocythemia (ET) and Primary Myelofibrosis (PMF). MPNs are associated with constitutive activation of JAK2 leading to persistent cell signaling downstream of the dimeric myeloid cytokine receptors due to mutations in three genes encoding JAK2, calreticulin (CALR) and the thrombopoietin (TPO) receptor (MPL or TPOR). CALR and MPL mutants induce JAK2 activation that depends on MPL expression, thus explaining why they induce megakaryocyte pathologies including ET and PMF, but not PV. In contrast, JAK2 V617F drives all three diseases as it induces persistent signaling via EPOR, G-CSFR (CSF3R) and MPL. Areas Covered: Here, we review how different pathogenic mutations of MPL are translated into active receptors by inducing stable dimerization. We focus on the unique role of MPL on the hematopoietic stem cell (HSC), explaining why MPL is indispensable for the development of all MPNs. Last but not least, we describe how CALR mutants are pathogenic via binding and activation of MPL. Expert Opinion: Altogether, we believe that MPL is an important, but challenging, therapeutic target in MPNs that requires novel strategies to interrupt the specific conformational changes induced by each mutation or pathologic interaction without compromising the key functions of wild type MPL.

SOHO State of the Art Updates and Next Questions: Myelofibrosis

The discovery of a mutation in the Janus Kinase 2 gene in 2005 spurred significant progress in the field of myeloproliferative neoplasms. A comprehensive description of genomic factors at play in the malignant clone in myeloproliferative neoplasms, particularly myelofibrosis (MF), have recently led to more precise, personalized prognostic tools. Despite this, understanding of the disease pathogenesis remains relatively limited. We continue to lack a detailed description of the interaction between the hematopoietic stem cell clone, abnormal bone marrow niche cells, and circulating signaling molecules and an understanding of how they cooperate to promote cell proliferation, fibrogenesis, and extramedullary hematopoiesis. Despite our knowledge gaps, recent research in MF has led to promising clinical translation. In this article, we summarize recent insights into MF pathophysiology, progress in the development of novel therapeutics, and opportunities for further advancement of the field.

JAK/STAT signaling in stem cells and regeneration: from Drosophila to vertebrates

The JAK/STAT pathway is a conserved metazoan signaling system that transduces cues from extracellular cytokines into transcriptional changes in the nucleus. JAK/STAT signaling is best known for its roles in immunity. However, recent work has demonstrated that it also regulates critical homeostatic processes in germline and somatic stem cells, as well as regenerative processes in several tissues, including the gonad, intestine and appendages. Here, we provide an overview of JAK/STAT signaling in stem cells and regeneration, focusing on Drosophila and highlighting JAK/STAT pathway functions in proliferation, survival and cell competition that are conserved between Drosophila and vertebrates.

KDM3A histone demethylase functions as an essential factor for activation of JAK2-STAT3 signaling pathway

Janus tyrosine kinase 2 (JAK2)-signal transducer and activator of transcription 3 (STAT3) signaling pathway is essential for modulating cellular development, differentiation, and homeostasis. Thus, dysregulation of JAK2-STAT3 signaling pathway is frequently associated with human malignancies. Here, we provide evidence that lysine-specific demethylase 3A (KDM3A) functions as an essential epigenetic enzyme for the activation of JAK2-STAT3 signaling pathway. KDM3A is tyrosine-phosphorylated by JAK2 in the nucleus and functions as a STAT3-dependent transcriptional coactivator. JAK2-KDM3A signaling cascade induced by IL-6 leads to alteration of histone H3K9 methylation as a predominant epigenetic event, thereby providing the functional and mechanistic link between activation of JAK2-STAT3 signaling pathway and its epigenetic control. Together, our findings demonstrate that inhibition of KDM3A phosphorylation could be a potent therapeutic strategy to control oncogenic effect of JAK2-STAT3 signaling pathway.

Gene and protein expression in the reproductive tract of Brazilian Somalis rams

Brazilian Somalis is a locally-adapted breed of rams raised in tropical climate and native pastures. The present study was conducted to evaluate gene expression and proteome of the reproductive tract of such rams. Samples were collected from testes, epididymides, seminal vesicles and bulbourethral glands of four rams. Expression of clusterin (CLU), osteopontin (OPN) and prostaglandin D2 synthase (PGDS) genes were evaluated in all samples by real-time PCR. Shotgun proteomic analysis was performed using samples from the head, corpus and cauda epididymides and from all other structures as well. Gene ontology terms and protein interactions were obtained from UniProtKB databases and MetaCore v.6.8 platform. CLU trasncripts were detected in the testes, epididymides, seminal vesicles and bulbourethral glands of the Somalis rams. The initial region and body of the epididymis had the greatest CLU expression. OPN mRNA was localized in all tissues of the ram reproductive tract. PGDS mRNA was detected in the testes and epididymides. Lable-free mass spectrometry allowed the identification of 137 proteins in all samples. Proteins of the epididymis head mainly participate in cellular processes and response to stimulus, participating in catalityc activity and binding. Proteins of epididymis body acted as regulatory proteins and in cellular processes, with binding and catalytic activity. Cauda epididymis molecules were associated with cellular processes and regulation, with binding function and catalytic activity as well. Testis proteins were mainly linked to cell processes and response to stimuli, and had catalytic function. Seminal vesicle proteins were involved in regulation and mainly with binding functions. Most bulbourethral gland proteins participated in cellular processes. The present study is the first to evaluate the proteome and gene expressions in the reproductive tract of Brazilian Somalis rams. Such pieces of information bring significant cointribution for the understanding of the reproductive physiology of locally-adapted livestock.

Momelotinib decreased cancer stem cell associated tumor burden and prolonged disease-free remission period in a mouse model of human ovarian cancer

Despite a good initial response to front-line chemotherapy, majority of the ovarian cancer patients relapse with consecutive phases of recurrences; and nearly 60% die within 5 years due to the development of a chemoresistant disease. This study investigated whether inhibition of the Janus kinase 2 (JAK2)-signal transducer and activator of transcription 3 (STAT3) pathway by momelotinib is sufficient in suppressing tumor burden and prolonging the disease-free survival period in a mouse model of ovarian cancer. We demonstrate that paclitaxel treatment enhanced JAK2/STAT3 activation which resulted in the enrichment of cancer stem cell (CSC)-like phenotype in the surviving ovarian cancer cells in vitro and in in vivo mouse xenografts. Combined treatment with paclitaxel and momelotinib inhibited paclitaxel-induced JAK2/STAT3 activation and CSC-like development in mice xenografts, and consequently reduced the tumor burden significantly greater than that achieved by paclitaxel-treatment alone. However, robust recurrent tumor growth with enhanced JAK2/STAT3 activation and CSC-like phenotype was observed in all mice groups after termination of treatments, but was delayed significantly in the paclitaxel and momelotinib treated group compared to other treatment groups. Daily oral gavage of momelotinib after termination of paclitaxel treatment showed sustained inhibition of tumor growth and a prolonged disease-free survival period in 50% of the mice. The other 50% of mice that developed tumors with ongoing momelotinib treatment also showed significantly increased survival benefit and a smaller tumor burden. These preliminary findings may have a profound clinical impact in developing an effective momelotinib-based ‘maintenance-therapy’ in ovarian cancer patients' post-chemotherapy treatment.

Myosin-Driven Intracellular Transport

The delivery of intracellular material within cells is crucial for maintaining normal function. Myosins transport a wide variety of cargo, ranging from vesicles to ribonuclear protein particles (RNPs), in plants, fungi, and metazoa. The properties of a given myosin transporter are adapted to move on different actin filament tracks, either on the disordered actin networks at the cell cortex or along highly organized actin bundles to distribute their cargo in a localized manner or move it across long distances in the cell. Transport is controlled by selective recruitment of the myosin to its cargo that also plays a role in activation of the motor.

The role of the cytoskeleton in biomineralisation in haptophyte algae

The production of calcium carbonate by coccolithophores (haptophytes) contributes significantly to global biogeochemical cycling. The recent identification of a silicifying haptophyte, Prymnesium neolepis, has provided new insight into the evolution of biomineralisation in this lineage. However, the cellular mechanisms of biomineralisation in both calcifying and silicifying haptophytes remain poorly understood. To look for commonalities between these two biomineralisation systems in haptophytes, we have determined the role of actin and tubulin in the formation of intracellular biomineralised scales in the coccolithophore, Coccolithus braarudii and in P. neolepis. We find that disruption of the actin network interferes with secretion of the biomineralised elements in both C. braarudii and P. neolepis. In contrast, disruption of the microtubule network does not prevent secretion of the silica scales in P. neolepis but results in production of abnormally small silica scales and also results in the increased formation of malformed coccoliths in C. braarudii. We conclude that the cytoskeleton plays a crucial role in biomineralisation in both silicifying and calcifying haptophytes. There are some important similarities in the contribution of the cytoskeleton to these different forms of biomineralisation, suggesting that common cellular mechanisms may have been recruited to perform similar roles in both lineages.

HiJAKing the epigenome in leukemia and lymphoma

The Janus kinase (JAK)/signal transducer and activator of transcription (STAT) pathway is central to signaling by receptors of diverse cytokines, growth factors, and other related molecules. Many of these receptors transmit anti-apoptosis, proliferation, and differentiation signals that are critical for normal hematopoiesis and immune response. However, the JAK/STAT signaling pathway is deregulated in many hematologic malignancies, and as such is co-opted by malignant cells to promote their survival and proliferation. It has recently come to light that an alternative mechanism, wherein nuclear JAKs epigenetically modify the chromatin to increase gene expression independent of STATs, also plays an important role in the pathogenesis of many hematologic malignancies. In this review, we will focus on common genetic alterations of the JAK family members in leukemia and lymphoma, and provide examples in which JAKs regulate gene expression by targeting the cancer epigenome.

Hitchhiking vesicular transport routes to the vacuole: Amyloid recruitment to the Insoluble Protein Deposit (IPOD)

Sequestration of aggregates into specialized deposition sites occurs in many species across all kingdoms of life ranging from bacteria to mammals and is commonly believed to have a cytoprotective function. Yeast cells possess at least 3 different spatially separated deposition sites, one of which is termed “Insoluble Protein Deposit (IPOD)” and harbors amyloid aggregates. We have recently discovered that recruitment of amyloid aggregates to the IPOD uses an actin cable based recruitment machinery that also involves vesicular transport.¹ Here we discuss how different proteins known to be involved in vesicular transport processes to the vacuole might act to guide amyloid aggregates to the IPOD. These factors include the Myosin V motor protein Myo2 involved in transporting vacuolar vesicles along actin cables, the transmembrane protein Atg9 involved in the recruitment of large precursor hydrolase complexes to the vacuole, the phosphatidylinositol/ phosphatidylcholine (PI/PC) transfer protein Sec 14 and the SNARE chaperone Sec 18. Furthermore, we present new data suggesting that the yeast dynamin homolog Vps1 is also crucial for faithful delivery of the amyloid model protein PrD-GFP to the IPOD. This is in agreement with a previously identified role for Vps1 in recruitment of heat-denatured aggregates to a perivacuolar deposition site.²

Mechanisms Regulating Stemness and Differentiation in Embryonal Carcinoma Cells

Just over ten years have passed since the seminal Takahashi-Yamanaka paper, and while most attention nowadays is on induced, embryonic, and cancer stem cells, much of the pioneering work arose from studies with embryonal carcinoma cells (ECCs) derived from teratocarcinomas. This original work was broad in scope, but eventually led the way for us to focus on the components involved in the gene regulation of stemness and differentiation. As the name implies, ECCs are malignant in nature, yet maintain the ability to differentiate into the 3 germ layers and extraembryonic tissues, as well as behave normally when reintroduced into a healthy blastocyst. Retinoic acid signaling has been thoroughly interrogated in ECCs, especially in the F9 and P19 murine cell models, and while we have touched on this aspect, this review purposely highlights how some key transcription factors regulate pluripotency and cell stemness prior to this signaling. Another major focus is on the epigenetic regulation of ECCs and stem cells, and, towards that end, this review closes on what we see as a new frontier in combating aging and human disease, namely, how cellular metabolism shapes the epigenetic landscape and hence the pluripotency of all stem cells.

Nuclear Import of JAK1 Is Mediated by a Classical NLS and Is Required for Survival of Diffuse Large B-cell Lymphoma

JAKs are non-receptor tyrosine kinases that are generally found in association with cytokine receptors. In the canonical pathway, roles of JAKs have well been established in activating STATs in response to cytokine stimulation to modulate gene transcription. In contrast, a noncanonical role of JAK2 has recently been discovered, in which JAK2 in the nucleus imparts the epigenetic regulation of gene transcription through phosphorylation of tyrosine 41 on the histone protein H3. Recent work further demonstrated that this noncanonical mechanism is conserved with JAK1, which is activated by the autocrine cytokines IL6 and IL10 in activated B-cell-like diffuse large B-cell lymphoma (ABC DLBCL), a cancer type that is particularly difficult to treat and has poor prognosis. However, how JAK1 gains access to the nucleus to enable epigenetic regulation remains undefined. Here, we investigated this question and revealed that JAK1 has a classical nuclear localization signal toward the N-terminal region, which can be recognized by multiple importin α isoforms. Moreover, the nuclear import of JAK1 is independent of its kinase activity but is required for the optimal expansion of ABC DLBCL cells in vitroImplications: This study demonstrates that the nuclear import of JAK1 is essential for the optimal fitness of ABC DLBCL cells, and targeting JAK1 nuclear localization is a potential therapeutic strategy for ABC DLBCL. Mol Cancer Res; 15(3); 348-57. ©2016 AACR.

Epigenetics of cell fate reprogramming and its implications for neurological disorders modelling

The reprogramming of human induced pluripotent stem cells (hiPSCs) proceeds in a stepwise manner with reprogramming factors binding and epigenetic composition changes during transition to maintain the epigenetic landscape, important for pluripotency. There arises a question as to whether the aberrant epigenetic state after reprogramming leads to epigenetic defects in induced stem cells causing unpredictable long term effects in differentiated cells. In this review, we present a comprehensive view of epigenetic alterations accompanying reprogramming, cell maintenance and differentiation as factors that influence applications of hiPSCs in stem cell based technologies. We conclude that sample heterogeneity masks DNA methylation signatures in subpopulations of cells and thus believe that beside a genetic evaluation, extensive epigenomic screening should become a standard procedure to ensure hiPSCs state before they are used for genome editing and differentiation into neurons of interest. In particular, we suggest that exploitation of the single-cell composition of the epigenome will provide important insights into heterogeneity within hiPSCs subpopulations to fast forward development of reliable hiPSC-based analytical platforms in neurological disorders modelling and before completed hiPSC technology will be implemented in clinical approaches.

Epigenetic gene regulation by Janus kinase 1 in diffuse large B-cell lymphoma

Janus kinases (JAKs) classically signal by activating STAT transcription factors but can also regulate gene expression by epigenetically phosphorylating histone H3 on tyrosine 41 (H3Y41-P). In diffuse large B-cell lymphomas (DLBCLs), JAK signaling is a feature of the activated B-cell (ABC) subtype and is triggered by autocrine production of IL-6 and IL-10. Whether this signaling involves STAT activation, epigenetic modification of chromatin, or both mechanisms is unknown. Here we use genetic and pharmacological inhibition to show that JAK1 signaling sustains the survival of ABC DLBCL cells. Whereas STAT3 contributed to the survival of ABC DLBCL cell lines, forced STAT3 activity could not protect these cells from death following JAK1 inhibition, suggesting epigenetic JAK1 action. JAK1 regulated the expression of nearly 3,000 genes in ABC DLBCL cells, and the chromatin surrounding many of these genes was modified by H3Y41-P marks that were diminished by JAK1 inhibition. These JAK1 epigenetic target genes encode important regulators of ABC DLBCL proliferation and survival, including IRF4, MYD88, and MYC. A small molecule JAK1 inhibitor cooperated with the BTK inhibitor ibrutinib in reducing IRF4 levels and acted synergistically to kill ABC DLBCL cells, suggesting that this combination should be evaluated in clinical trials.

Mathematical Models of Pluripotent Stem Cells: At the Dawn of Predictive Regenerative Medicine

Regenerative medicine, ranging from stem cell therapy to organ regeneration, is promising to revolutionize treatments of diseases and aging. These approaches require a perfect understanding of cell reprogramming and differentiation. Predictive modeling of cellular systems has the potential to provide insights about the dynamics of cellular processes, and guide their control. Moreover in many cases, it provides alternative to experimental tests, difficult to perform for practical or ethical reasons. The variety and accuracy of biological processes represented in mathematical models grew in-line with the discovery of underlying molecular mechanisms. High-throughput data generation led to the development of models based on data analysis, as an alternative to more established modeling based on prior mechanistic knowledge. In this chapter, we give an overview of existing mathematical models of pluripotency and cell fate, to illustrate the variety of methods and questions. We conclude that current approaches are yet to overcome a number of limitations: Most of the computational models have so far focused solely on understanding the regulation of pluripotency, and the differentiation of selected cell lineages. In addition, models generally interrogate only a few biological processes. However, a better understanding of the reprogramming process leading to ESCs and iPSCs is required to improve stem-cell therapies. One also needs to understand the links between signaling, metabolism, regulation of gene expression, and the epigenetics machinery.

Modeling heterogeneity in the pluripotent state: A promising strategy for improving the efficiency and fidelity of stem cell differentiation

Pluripotency can be considered a functional characteristic of pluripotent stem cells (PSCs) populations and their niches, rather than a property of individual cells. In this view, individual cells within the population independently adopt a variety of different expression states, maintained by different signaling, transcriptional, and epigenetics regulatory networks. In this review, we propose that generation of integrative network models from single cell data will be essential for getting a better understanding of the regulation of self-renewal and differentiation. In particular, we suggest that the identification of network stability determinants in these integrative models will provide important insights into the mechanisms mediating the transduction of signals from the niche, and how these signals can trigger differentiation. In this regard, the differential use of these stability determinants in subpopulation-specific regulatory networks would mediate differentiation into different cell fates. We suggest that this approach could offer a promising avenue for the development of novel strategies for increasing the efficiency and fidelity of differentiation, which could have a strong impact on regenerative medicine.

Beyond transcription factors: how oncogenic signalling reshapes the epigenetic landscape

Cancer, once thought to be caused largely by genetic alterations, is now considered to be a mixed genetic and epigenetic disease. The epigenetic landscape, which is dictated by covalent DNA and histone modifications, is profoundly altered in transformed cells. These abnormalities may arise from mutations in, or altered expression of, chromatin modifiers. Recent reports on the interplay between cellular signalling pathways and chromatin modifications add another layer of complexity to the already complex regulation of the epigenome. In this Review, we discuss these new studies and how the insights they provide can contribute to a better understanding of the molecular pathogenesis of neoplasia.

Cytokine-induced megakaryocytic differentiation is regulated by genome-wide loss of a uSTAT transcriptional program

Metazoan development is regulated by transcriptional networks, which must respond to extracellular cues including cytokines. The JAK/STAT pathway is a highly conserved regulatory module, activated by many cytokines, in which tyrosine-phosphorylated STATs (pSTATs) function as transcription factors. However, the mechanisms by which STAT activation modulates lineage-affiliated transcriptional programs are unclear. We demonstrate that in the absence of thrombopoietin (TPO), tyrosine-unphosphorylated STAT5 (uSTAT5) is present in the nucleus where it colocalizes with CTCF and represses a megakaryocytic transcriptional program. TPO-mediated phosphorylation of STAT5 triggers its genome-wide relocation to STAT consensus sites with two distinct transcriptional consequences, loss of a uSTAT5 program that restrains megakaryocytic differentiation and activation of a canonical pSTAT5-driven program which includes regulators of apoptosis and proliferation. Transcriptional repression by uSTAT5 reflects restricted access of the megakaryocytic transcription factor ERG to target genes. These results identify a previously unrecognized mechanism of cytokine-mediated differentiation.

Carboxyl-terminal domain of MUC16 imparts tumorigenic and metastatic functions through nuclear translocation of JAK2 to pancreatic cancer cells

MUC16 (CA125) is a type-I transmembrane glycoprotein that is up-regulated in multiple cancers including pancreatic cancer (PC). However, the existence and role of carboxyl-terminal MUC16 generated following its cleavage in PC is unknown. Our previous study using a systematic dual-epitope tagged domain deletion approach of carboxyl-terminal MUC16 has demonstrated the generation of a 17-kDa cleaved MUC16 (MUC16-Cter). Here, we demonstrate the functional significance of MUC16-Cter in PC using the dual-epitope tagged version (N-terminal FLAG- and C-terminal HA-tag) of 114 carboxyl-terminal residues of MUC16 (F114HA). In vitro analyses using F114HA transfected MiaPaCa-2 and T3M4 cells showed enhanced proliferation, motility and increased accumulation of cells in the G2/M phase with apoptosis resistance, a feature associated with cancer stem cells (CSCs). This was supported by enrichment of ALDH⁺ CSCs along with enhanced drug-resistance. Mechanistically, we demonstrate a novel function of MUC16-Cter that promotes nuclear translocation of JAK2 resulting in phosphorylation of Histone-3 up-regulating stemness-specific genes LMO2 and NANOG. Jak2 dependence was demonstrated using Jak2^+/+ and Jak2^−/− cells. Using eGFP-Luciferase labeled cells, we demonstrate enhanced tumorigenic and metastatic potential of MUC16-Cter in vivo. Taken together, we demonstrate that MUC16-Cter mediated enrichment of CSCs is partly responsible for tumorigenic, metastatic and drug-resistant properties of PC cells.

Integration of Signaling Pathways with the Epigenetic Machinery in the Maintenance of Stem Cells

Stem cells balance their self-renewal and differentiation potential by integrating environmental signals with the transcriptional regulatory network. The maintenance of cell identity and/or cell lineage commitment relies on the interplay of multiple factors including signaling pathways, transcription factors, and the epigenetic machinery. These regulatory modules are strongly interconnected and they influence the pattern of gene expression of stem cells, thus guiding their cellular fate. Embryonic stem cells (ESCs) represent an invaluable tool to study this interplay, being able to indefinitely self-renew and to differentiate towards all three embryonic germ layers in response to developmental cues. In this review, we highlight those mechanisms of signaling to chromatin, which regulate chromatin modifying enzymes, histone modifications, and nucleosome occupancy. In addition, we report the molecular mechanisms through which signaling pathways affect both the epigenetic and the transcriptional state of ESCs, thereby influencing their cell identity. We propose that the dynamic nature of oscillating signaling and the different regulatory network topologies through which those signals are encoded determine specific gene expression programs, leading to the fluctuation of ESCs among multiple pluripotent states or to the establishment of the necessary conditions to exit pluripotency.

Potential Gene Interactions in the Cell Cycles of Gametes, Zygotes, Embryonic Stem Cells and the Development of Cancer

OBJECTIVES

This review is to explore whether potential gene interactions in the cell cycles of gametes, zygotes, and embryonic stem (ES) cells are associated with the development of cancer.

METHODS

MEDPILOT at the Central Library of the University of Cologne, Germany (Zentralbibliothek Köln) that covers 5,800 international medical journals and 4,300 E-journals was used to collect data. The initial searches were done in December 2012 and additional searches in October 2013-May 2015. The search terms included "cancer development," "gene interaction," and "ES cells," and the time period was between 1998 and 2015. A total of 147 articles in English language only were included in this review.

RESULTS

Transgenerational gene translation is implemented in the zygote through interactions of epigenetic isoforms of transcription factors (TFs) from parental gametes, predominantly during the first two zygote cleavages. Pluripotent transcription factors may provide interacting links with mutated genes during zygote-to-ES cell switches. Translation of post-transcriptional carcinogenic genes is implemented by abnormally spliced, tumor-specific isoforms of gene-encoded mRNA/non-coding RNA variants of TFs employing de novo gene synthesis and neofunctionalization. Post-translationally, mutated genes are preserved in pre-neoplastic ES cell subpopulations that can give rise to overt cancer stem cells. Thus, TFs operate as cell/disease-specific epigenetic messengers triggering clinical expression of neoplasms.

CONCLUSION

Potential gene interactions in the cell cycle of gametes, zygotes, and ES cells may play some roles in the development of cancer.

LIF signal in mouse embryonic stem cells

Since the establishment of mouse embryonic stem cells (mESCs) in the 1980s, a number of important notions on the self-renewal of pluripotent stem cells in vitro have been found. In serum containing conventional culture, an exogenous cytokine, leukemia inhibitory factor (LIF), is absolutely essential for the maintenance of pluripotency. In contrast, in serum-free culture with simultaneous inhibition of Map-kinase and Gsk3 (so called 2i-culture), LIF is no longer required. However, recent findings also suggest that LIF may have a role not covered by the 2i for the maintenance of naïve pluripotency. These suggest that LIF functions for the maintenance of naïve pluripotency in a context dependent manner. We summarize how LIF-signal pathway is converged to maintain the naïve state of pluripotency.

Histone core phosphorylation regulates DNA accessibility

Nucleosome unwrapping dynamics provide transient access to the complexes involved in DNA transcription, repair, and replication, whereas regulation of nucleosome unwrapping modulates occupancy of these complexes. Histone H3 is phosphorylated at tyrosine 41 (H3Y41ph) and threonine 45 (H3T45ph). H3Y41ph is implicated in regulating transcription, whereas H3T45ph is involved in DNA replication and apoptosis. These modifications are located in the DNA-histone interface near where the DNA exits the nucleosome, and are thus poised to disrupt DNA-histone interactions. However, the impact of histone phosphorylation on nucleosome unwrapping and accessibility is unknown. We find that the phosphorylation mimics H3Y41E and H3T45E, and the chemically correct modification, H3Y41ph, significantly increase nucleosome unwrapping. This enhances DNA accessibility to protein binding by 3-fold. H3K56 acetylation (H3K56ac) is also located in the same DNA-histone interface and increases DNA unwrapping. H3K56ac is implicated in transcription regulation, suggesting that H3Y41ph and H3K56ac could function together. We find that the combination of H3Y41ph with H3K56ac increases DNA accessibility by over an order of magnitude. These results suggest that phosphorylation within the nucleosome DNA entry-exit region increases access to DNA binding complexes and that the combination of phosphorylation with acetylation has the potential to significantly influence DNA accessibility to transcription regulatory complexes.

Deregulated JAK/STAT signalling in lymphomagenesis, and its implications for the development of new targeted therapies

Gene expression profiling has implicated several intracellular signalling cascades, including the JAK/STAT pathway, in the pathogenesis of particular subtypes of lymphoma. In marked contrast to the situation in patients with either acute lymphoblastic leukaemia or a myeloproliferative neoplasm, JAK2 coding sequence mutations are rare in lymphoma patients with an activated JAK/STAT "signature". This is instead the consequence of mutational events that result in the increased expression of non-mutated JAK2; positively or negatively affect the activity of other components of the JAK/STAT pathway; or establish an autocrine signalling loop that drives JAK-mediated cytokine-independent proliferation. Here, we detail these genetic lesions, their functional consequences, and impact on patient outcome. In light of the approval of a JAK1/JAK2 inhibitor for the treatment of myelofibrosis, and preliminary studies evaluating the efficacy of other JAK inhibitors, the therapeutic potential of compounds that target JAK/STAT signalling in the treatment of patients with lymphoma is also discussed.

SPREDs (Sprouty related proteins with EVH1 domain) promote self-renewal and inhibit mesodermal differentiation in murine embryonic stem cells

BACKGROUND

Pluripotency, self-renewal, and differentiation are special features of embryonic stem (ES) cells, thereby providing valuable perspectives in regenerative medicine. Developmental processes require a fine-tuned organization, mainly regulated by the well-known JAK/STAT, PI3K/AKT, and ERK/MAPK pathways. SPREDs (Sprouty related proteins with EVH1 domain) were discovered as inhibitors of the ERK/MAPK signaling pathway, whereas nothing was known about their functions in ES cells and during early differentiation, so far.

RESULTS

We generated SPRED1 and SPRED2 overexpressing and SPRED2 knockout murine ES cells to analyze the functions of SPRED proteins in ES cells and during early differentiation. Overexpression of SPREDs increases significantly the self-renewal and clonogenicity of murine ES cells, whereas lack of SPRED2 reduces proliferation and increases apoptosis. During early differentiation in embryoid bodies, SPREDs promote the pluripotent state and inhibit differentiation whereby mesodermal differentiation into cardiomyocytes is considerably delayed and inhibited. LIF- and growth factor-stimulation revealed that SPREDs inhibit ERK/MAPK activation in murine ES cells. However, no effects were detectable on LIF-induced activation of the JAK/STAT3, or PI3K/AKT signaling pathway by SPRED proteins.

CONCLUSIONS

We show that SPREDs promote self-renewal and inhibit mesodermal differentiation of murine ES cells by selective suppression of the ERK/MAPK signaling pathway in pluripotent cells.

Analysis of the interactions between Rab GTPases and class V myosins

Myosins are actin-based motor proteins that are involved in a wide variety of cellular processes such as membrane transport, muscle contraction, and cell division. Humans have over 40 myosins that can be placed into 18 classes, the malfunctioning of a number of which can lead to disease. There are three members of the human class V myosin family, myosins Va, Vb, and Vc. People lacking functional myosin Va suffer from a rare autosomal recessive disease called Griscelli's Syndrome type I (GS1) that is characterized by severe neurological defects and partial albinism. Mutations in the myosin Vb gene lead to an epithelial disorder called microvillus inclusion disease (MVID) that is often fatal in infants. The class V myosins have been implicated in the transport of diverse cargoes such as melanosomes in pigment cells, synaptic vesicles in neurons, RNA transcripts in a variety of cell types, and organelles such as the endoplasmic reticulum. The Rab GTPases play a critical role in recruiting class V myosins to their cargo. We recently published a study in which we used the yeast two-hybrid system to systematically test myosin Va for its ability to interact with each member of the human Rab GTPase family. We present here a detailed description of this yeast two-hybrid "living chip" assay. Furthermore, we present a protocol for validating positive interactions obtained from this screen by coimmunoprecipitation.

Role of leukemia inhibitory factor in the nervous system and its pathology

Leukemia inhibitory factor (LIF) is a multifunction cytokine that has various effects on different tissues and cell types in rodents and humans; however, its insufficiency has a relatively mild impact. This could explain why only some aspects of LIF activity are in the limelight, whereas other aspects are not well known. In this review, the LIF structure, signaling pathway, and primary roles in the development and function of an organism are reviewed, and the effects of LIF on stem cell growth and differentiation, which are important for its use in cell culturing, are described. The focus is on the roles of LIF in central nervous system development and on the modulation of its physiological functions as well as the involvement of LIF in the pathogenesis of brain diseases and injuries. Finally, LIF and its signaling pathway are discussed as potential targets of therapeutic interventions to influence both negative phenomena and regenerative processes following brain injury.

Revisiting STAT3 signalling in cancer: new and unexpected biological functions

The Janus kinases (JAKs) and signal transducer and activator of transcription (STAT) proteins, particularly STAT3, are among the most promising new targets for cancer therapy. In addition to interleukin-6 (IL-6) and its family members, multiple pathways, including G-protein-coupled receptors (GPCRs), Toll-like receptors (TLRs) and microRNAs were recently identified to regulate JAK-STAT signalling in cancer. Well known for its role in tumour cell proliferation, survival, invasion and immunosuppression, JAK-STAT3 signalling also promotes cancer through inflammation, obesity, stem cells and the pre-metastatic niche. In addition to its established role as a transcription factor in cancer, STAT3 regulates mitochondrion functions, as well as gene expression through epigenetic mechanisms. Newly identified regulators and functions of JAK-STAT3 in tumours are important targets for potential therapeutic strategies in the treatment of cancer.