Intrinsic Regulator Research Articles

Splenic hematopoietic stem cells display a pre-activated phenotype.

Splenic hematopoiesis is crucial to the pathogenesis of diseases including myocardial infarction and atherosclerosis. The spleen acts as a reservoir of myeloid cells, which are quickly expelled out in response to acute inflammation. In contrast to the well-defined bone marrow hematopoiesis, the cellular and molecular components sustaining splenic hematopoiesis are poorly understood. Surprisingly, we found that, unlike quiescent bone marrow hematopoietic stem cells (HSC), most of splenic HSC are in the G1 phase in C57BL/6 mice. Moreover, splenic HSC were enriched for genes involved in G0-G1 transition and expressed lower levels of genes responsible for G1-S transition. These data indicate that, at steady state, splenic HSC are pre-activated, which may expedite their cell cycle entry in emergency conditions. Consistently, in the acute phase of septic shock induced by LPS injection, splenic HSC entered the S-G2-M phase, whereas bone marrow HSC did not. Mobilization and transplantation experiments displayed that bone marrow HSC, once in the spleen, acquired cell cycle status similar to splenic HSC, strongly suggesting that the splenic microenvironment plays an important role in HSC pre-activation. In addition, we found that myeloid translocation gene 16 (Mtg16) deficiency in C57BL/6 mice resulted in significantly increased S-G2-M entry of splenic but not bone marrow HSC, suggesting that Mtg16 is an intrinsic negative regulator of G1-S transition in splenic HSC. Altogether, this study demonstrates that compared to bone marrow, splenic HSC are in a pre-activated state, which is driven by extracellular signals provided by splenic microenvironment and HSC intrinsic factor Mtg16.

Phosphorylation of G protein γ subunit Ste18 and the Ste5 scaffold form a braking system that governs pathway activation kinetics and switch‐like signaling in yeast

Heterotrimeric G proteins (Gαβγ) play a critical role as transducers in G protein signaling systems responsible for activating a wide range of physiological processes including neurotransmitter and hormone signaling. In yeast, G protein signaling differentially activates two distinct mitogen‐activated protein kinases (MAPKs) – Fus3 and Kss1 – a phenomenon that requires conformational switching of the scaffold protein Ste5. Here we show that rapid receptor‐activated phosphorylation of the intrinsically disordered N‐terminal tail of the yeast Gγ subunit (Ste18), in combination with MAPK phosphorylation of Ste5, serves as a brake system that controls the rate and stability of scaffold association at the plasma membrane. Disabling the brake by precise point mutation of Ste18 phosphorylation sites or a MAPK docking site on Ste5 differentially governs the kinetics and amplitude of MAPK activation as well as the switch‐like morphological response to the stimulus. Complete elimination of the brake results in a response that is 5 times faster and ~4 times amplified over the response in wild type cells. Finally, we show that phosphorylation of Ste18 appeared late in evolutionary history ‐ at the same time as the MAPK docking site on Ste5, suggesting the possibility that both sides of the brake co‐evolved. Since phosphorylated intrinsically disordered tails are structurally conserved elements found in all Gγ subunits, including mammals, these results provide compelling evidence that such tails may function as intrinsic regulators of G protein signaling by altering the interactions of Gβγ subunits with their binding partners.Support or Funding InformationThis work was supported by funding from NIH grant GM117400 to M.T.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Wnt3 and Gata4 regulate axon regeneration in adult mouse DRG neurons

Neurons in the adult central nervous system (CNS) have a poor intrinsic axon growth potential after injury, but the underlying mechanisms are largely unknown. Wingless-related mouse mammary tumor virus integration site (WNT) family members regulate neural stem cell proliferation, axon tract and forebrain development in the nervous system. Here we report that Wnt3 is an important modulator of axon regeneration. Downregulation or overexpression of Wnt3 in adult dorsal root ganglion (DRG) neurons enhances or inhibits their axon regeneration ability respectively in vitro and in vivo. Especially, we show that Wnt3 modulates axon regeneration by repressing mRNA translation of the important transcription factor Gata4 via binding to the three prime untranslated region (3′UTR). Downregulation of Gata4 could restore the phenotype exhibited by Wnt3 downregulation in DRG neurons. Taken together, these data indicate that Wnt3 is a key intrinsic regulator of axon growth ability of the nervous system.

Tailoring Immune Responses toward Autoimmunity: Transcriptional Regulators That Drive the Creation and Collusion of Autoreactive Lymphocytes.

T-dependent humoral immune responses to infection involve a collaboration between B and CD4 T cell activation, migration, and co-stimulation, thereby culminating in the formation of germinal centers (GCs) and eventual differentiation into memory cells and long-lived plasma cells (PCs). CD4 T cell-derived signals drive the formation of a tailored B cell response. Downstream of these signals are transcriptional regulators that are the critical enactors of immune cell programs. In particular, a core group of transcription factors regulate both B and T cell differentiation, identity, and function. The timing and expression levels of these transcription factors are tightly controlled, with dysregulated expression correlated to immune cell dysfunction in autoimmunity and lymphomagenesis. Recent studies have significantly advanced our understanding of both extrinsic and intrinsic regulators of autoreactive B cells and antibody-secreting PCs in systemic lupus erythematosus, rheumatoid arthritis, and other autoimmune conditions. Yet, there are still gaps in our understanding of the causative role these regulators play, as well as the link between lymphoid responses and peripheral damage. This review will focus on the genesis of immunopathogenic CD4 helper and GC B cells. In particular, we will detail the transcriptional regulation of cytokine and chemokine receptor signaling during the pathogenesis of GC-derived autoimmune conditions in both murine models and human patients.

The Mediator co-activator complex regulates Ty1 retromobility by controlling the balance between Ty1i and Ty1 promoters.

The Ty1 retrotransposons present in the genome of Saccharomyces cerevisiae belong to the large class of mobile genetic elements that replicate via an RNA intermediary and constitute a significant portion of most eukaryotic genomes. The retromobility of Ty1 is regulated by numerous host factors, including several subunits of the Mediator transcriptional co-activator complex. In spite of its known function in the nucleus, previous studies have implicated Mediator in the regulation of post-translational steps in Ty1 retromobility. To resolve this paradox, we systematically examined the effects of deleting non-essential Mediator subunits on the frequency of Ty1 retromobility and levels of retromobility intermediates. Our findings reveal that loss of distinct Mediator subunits alters Ty1 retromobility positively or negatively over a >10,000-fold range by regulating the ratio of an internal transcript, Ty1i, to the genomic Ty1 transcript. Ty1i RNA encodes a dominant negative inhibitor of Ty1 retromobility that blocks virus-like particle maturation and cDNA synthesis. These results resolve the conundrum of Mediator exerting sweeping control of Ty1 retromobility with only minor effects on the levels of Ty1 genomic RNA and the capsid protein, Gag. Since the majority of characterized intrinsic and extrinsic regulators of Ty1 retromobility do not appear to effect genomic Ty1 RNA levels, Mediator could play a central role in integrating signals that influence Ty1i expression to modulate retromobility.

A2AR Adenosine Signaling Suppresses Natural Killer Cell Maturation in the Tumor Microenvironment.

Extracellular adenosine is a key immunosuppressive metabolite that restricts activation of cytotoxic lymphocytes and impairs antitumor immune responses. Here, we show that engagement of A2A adenosine receptor (A2AR) acts as a checkpoint that limits the maturation of natural killer (NK) cells. Both global and NK-cell-specific conditional deletion of A2AR enhanced proportions of terminally mature NK cells at homeostasis, following reconstitution, and in the tumor microenvironment. Notably, A2AR-deficient, terminally mature NK cells retained proliferative capacity and exhibited heightened reconstitution in competitive transfer assays. Moreover, targeting A2AR specifically on NK cells also improved tumor control and delayed tumor initiation. Taken together, our results establish A2AR-mediated adenosine signaling as an intrinsic negative regulator of NK-cell maturation and antitumor immune responses. On the basis of these findings, we propose that administering A2AR antagonists concurrently with NK cell-based therapies may heighten therapeutic benefits by augmenting NK cell-mediated antitumor immunity.Significance: Ablating adenosine signaling is found to promote natural killer cell maturation and antitumor immunity and reduce tumor growth. Cancer Res; 78(4); 1003-16. ©2017 AACR.

Linc-RAM is required for FGF2 function in regulating myogenic cell differentiation

ABSTRACTMyogenic differentiation of skeletal muscle stem cells, also known satellite cells, is tightly orchestrated by extrinsic and intrinsic regulators. Basic fibroblast growth factor (FGF2) is well documented to be implicated in satellite cell self-renewal and differentiation by repressing MyoD. We recently identified a MyoD-regulated and skeletal muscle-specifically expressed long non-coding RNA Linc-RAM which enhances myogenic differentiation by facilitating MyoD/Baf60c/Brg1 complex assembly. Herein, we investigated the transcriptional regulation and intracellular signaling pathway in mediating Linc-RAM gene expression during muscle cell differentiation. Firstly, we demonstrate Linc-RAM is negatively regulated by FGF2 via Ras/Raf/Mek/Erk signaling pathway in muscle cells. Overexpression of MyoD significantly attenuates repression of Linc-RAM promoter activities in C2C12 cells treated with FGF2. Knockout of MyoD abolishes FGF2-mediated repression of Linc-RAM gene transcription in satellite cells sorted from skeletal muscle of MyoD−/−;Pax7-nGFP mice, suggesting inhibition of MyoD is required for FGF2-mediated expression of Linc-RAM. For the functional significance, we show that overexpression of Linc-RAM rescues FGF2-induced inhibition of C2C12 cell differentiation, indicating inhibition of Linc-RAM is required for FGF2-mediated suppression of myogenic differentiation. Consistently, we are able to further corroborate the requirement of Linc-RAM inhibition for FGF2-modulated repression of myogenic differentiation by using an ex vivo cultured single fiber system and satellite cells sorted from Linc-RAM−/−;Pax7-nGFP knockout mice. Collectively, the present study not only reveals the intracellular signaling in FGF2-mediated Linc-RAM gene expression but also demonstrate the functional significance of Linc-RAM in FGF2-mediated muscle cell differentiation.

CRABP1 protects the heart from isoproterenol-induced acute and chronic remodeling.

Excessive and/or persistent activation of calcium-calmodulin protein kinase II (CaMKII) is detrimental in acute and chronic cardiac injury. However, intrinsic regulators of CaMKII activity are poorly understood. We find that cellular retinoic acid-binding protein 1 (CRABP1) directly interacts with CaMKII and uncover a functional role for CRABP1 in regulating CaMKII activation. We generated Crabp1-null mice (CKO) in C57BL/6J background for pathophysiological studies. CKO mice develop hypertrophy as adults, exhibiting significant left ventricular dilation with reduced ejection fraction at the baseline cardiac function. Interestingly, CKO mice have elevated basal CaMKII phosphorylation at T287, and phosphorylation on its substrate phospholamban (PLN) at T17. Acute isoproterenol (ISO) challenge (80 mg/kg two doses in 1 day) causes more severe apoptosis and necrosis in CKO hearts, and treatment with a CaMKII inhibitor KN-93 protects CKO mice from this injury. Chronic (30 mg/kg/day) ISO challenge also significantly increases hypertrophy and fibrosis in CKO mice as compared to WT. In wild-type mice, CRABP1 expression is increased in early stages of ISO challenge and eventually reduces to the basal level. Mechanistically, CRABP1 directly inhibits CaMKII by competing with calmodulin (CaM) for CaMKII interaction. This study demonstrates increased susceptibility of CKO mice to ISO-induced acute and chronic cardiac injury due to, at least in part, elevated CaMKII activity. Deleting Crabp1 results in reduced baseline cardiac function and aggravated damage challenged with acute and persistent β-adrenergic stimulation. This is the first report of a physiological role of CRABP1 as an endogenous regulator of CaMKII, which protects the heart from ISO-induced damage.

Corrigendum] miRNA-1207-5p is associated with cancer progression by targeting stomatin-like protein 2 in esophageal carcinoma.

An interested reader drew to our attention that, in the above-mentioned article, there were two figures where identity in certain of the data was shared between panels within the same figure. First, in Fig.3B, the data shown for the EC9706 cell line/negative control (NC) experiment were derived from the same original source as those for the EC-1/Blank control experiment. Secondly, in Fig.6B the Bcl-2 bands for the two different cell lines, EC9706 and EC-1, were inadvertently duplicated (the data shown for the EC9706 cell line were correct). We have reviewed the original files and the individual figures for the submitted composite figures, and realize that the errors occurred when we produced the composite figures. The same images were accidentally inserted twice in Figs.3and6 without us being fully aware of the error. We have identified all the original images, and the corrected versions of Figs.3 and6 are shown opposite. We regret that these errors went unnoticed prior to publication, and thank the Editor for affording us the opportunity to publish this Corrigendum. We also regret any inconvenience caused to the readership of the journal. [the original article was published in the International Journal of Oncology 46: 2163-2171, 2015; DOI: 10.3892/ijo.2015.2900].

Cytoplasmic Linker Protein CLIP170 Negatively Regulates TLR4 Signaling by Targeting the TLR Adaptor Protein TIRAP.

Cytoplasmic linker protein 170 (CLIP170) is a CAP-Gly domain-containing protein that is associated with the plus end of growing microtubules and implicated in various cellular processes, including the regulation of microtubule dynamics, cell migration, and intracellular transport. Our studies revealed a previously unrecognized property and role of CLIP170. We identified CLIP170 as one of the interacting partners of Brucella effector protein TcpB that negatively regulates TLR2 and TLR4 signaling. In this study, we demonstrate that CLIP170 interacts with the TLR2 and TLR4 adaptor protein TIRAP. Furthermore, our studies revealed that CLIP170 induces ubiquitination and subsequent degradation of TIRAP to negatively regulate TLR4-mediated proinflammatory responses. Overexpression of CLIP170 in mouse macrophages suppressed the LPS-induced expression of IL-6 and TNF-α whereas silencing of endogenous CLIP170 potentiated the levels of proinflammatory cytokines. In vivo silencing of CLIP170 in C57BL/6 mice by CLIP170-specific small interfering RNA enhanced LPS-induced IL-6 and TNF-α expression. Furthermore, we found that LPS modulates the expression of CLIP170 in mouse macrophages. Overall, our experimental data suggest that CLIP170 serves as an intrinsic negative regulator of TLR4 signaling that targets TIRAP.

NANOS2 acts as an intrinsic regulator of gonocytes-to-spermatogonia transition in the murine testes

In the male mouse embryos, the primordial germ cells colonize the developing testes at E11.5. These resident germ cells termed gonocytes are the predecessors of spermatogonial stem cells (SSCs) and differentiating spermatogonia. Both of which are essential for male fertility where the former maintains the continuity of spermatogenesis and the latter generates pioneering waves of spermatozoa. Therefore the timely initiation of gonocytes-to-spermatogonia transition (GST) is an important process during which the cell fates of gonocytes might be segregated. However, it is unknown whether gonocytes are composed of a heterogeneous mixture of germ cells with distinct differentiation potentials during GST. Here, we find that gonocytes exhibit heterogeneity in terms of the expression pattern of at least three early spermatogonial marker genes namely Nanos2, Stra8 and Gfra1. NANOS2 expression levels are negatively correlated with those of STRA8 and GFRA1 before GST, while positive correlation with GFRA1 is established after GST. We further find that overexpression of NANOS2 results in the repression of GFRA1 and PLZF in gonocytes, leading to a delay in GST. On the other hand, loss of NANOS2 results in the up-regulation of GFRA1 and PLZF, indicating a precocious entry of GST. Taken together, our data suggest that NANOS2 functions as an intrinsic timekeeper of GST in the mouse testes.

TLX is an intrinsic regulator of the negative effects of IL-1β on proliferating hippocampal neural progenitor cells.

Hippocampal neurogenesis is a lifelong process whereby new neurons are produced and integrate into the host circuitry within the hippocampus. It is regulated by a multitude of extrinsic and intrinsic regulators and is believed to contribute to certain hippocampal-dependent cognitive tasks. Hippocampal neurogenesis and associated cognition have been demonstrated to be impaired after increases in the levels of proinflammatory cytokine IL-1β in the hippocampus, such as that which occurs in various neurodegenerative and psychiatric disorders. IL-1β also suppresses the expression of TLX (orphan nuclear receptor tailless homolog), which is an orphan nuclear receptor that functions to promote neural progenitor cell (NPC) proliferation and suppress neuronal differentiation; therefore, manipulation of TLX represents a potential strategy with which to prevent the antiproliferative effects of IL-1β. In this study, we assessed the mechanism that underlies IL-1β-induced changes in TLX expression and determined the protective capacity of TLX to mitigate the effects of IL-1β on embryonic rat hippocampal neurosphere expansion. We demonstrate that IL-1β activated the NF-κB pathway in proliferating NPCs and that this activation was responsible for IL-1β-induced changes in TLX expression. In addition, we report that enhancing TLX expression prevented the IL-1β-induced suppression of neurosphere expansion. Thus, we highlight TLX as a potential protective regulator of the antiproliferative effects of IL-1β on hippocampal neurogenesis.-Ó'Léime, C. S., Kozareva, D. A., Hoban, A. E., Long-Smith, C. M., Cryan, J. F., Nolan, Y. M. TLX is an intrinsic regulator of the negative effects of IL-1β on proliferating hippocampal neural progenitor cells.

Essential Role of c-MYC for Natural Killer Cell Development, Proliferation and Anti-Tumor Activity

Natural killer (NK) cells are the major component of innate immunity with both cytotoxicity and cytokine producing effector functions. NK cells also regulate the interplay between innate immunity and adaptive immunity by secreting certain cytokines. Extrinsic regulators of NK cell development and function, including diverse ligands of NK cell receptors and cytokines from the microenvironment, have been extensively studied. However, intrinsic regulators for NK cell biology are still less understood. In our previous study on aggressive NK cell leukemia (ANKL), genomics and transcriptomics analyses indicated that c-MYC was universally upregulated and responsible for the proliferation and survival in ANKL cells (Manuscript in revision). Furthermore, STAT5, as a transcriptional regulator of c-MYC, was found to be essential in the survival and development of NK cells (Eckelhart et al., Blood 2011). In this regard, we want to understand the physiological and oncological roles of c-MYC in NK cells.To achieve our goal, we made two mouse models including c-Myc loss-of-function (LOF) and c-Myc gain-of-function (GOF) in NK cells. Ncr1Cre knock-in mice, in which Cre recombinase was inserted into the Nkp46 locus, was used. We crossed the c-Mycf/f mice with Ncr1Cre mice to generate the NK cell specific c-Myc LOF model c-MycΔ/Δ/Ncr1Cre. To generate the c-Myc GOF model, we crossed the Tg(tetO-MYC) mice with Ncr1Cre and Rosa26-Loxp-Stop-Loxp(LSL)-rtTA-GFP mice to get the Tg(tetO-MYC)/ Ncr1Cre/LSL-rtTA-GFP (iMYC) mice, in which c-Myc expression can be induced in a doxycycline dependent manner in NK cells. c-MycΔ/Δ/Ncr1Cre mice were analyzed between 6 to 14-weeks old. iMYC mice were induced by doxycycline from 6-weeks old for over 2 months and then analyzed. Wild type littermates were used as controls. In both models, mice were born normally and showed no obvious difference in growth compared to their littermates.In c-MycΔ/Δ/Ncr1Cre mice, a significant reduction of NK1.1+/DX5+ NK cell percentages in peripheral blood (3.6 ± 0.4% vs. 0.5 ± 0.1%, P < 0.0001, N=7) and spleen (2.4 ± 0.5% vs. 0.7 ± 0.1%, P < 0.01, N=6) was detected. In addition, the percentage of CD11b+ mature NK cells in the NK1.1+/DX5+ population was also reduced. In bone marrow (BM), although the total percentage of NK1.1+/DX5+ NK cells did not change, an obvious block of NK cell development was seen, as the majority of NK1.1+/DX5+ cells in BM were CD27+/CD11b- cells, which represent an immature pattern. To assess whether the NK cell proliferation is altered in this model, we performed BrdU labeling assays and found that BrdU incorporation rates decreased dramatically both in peripheral NK cells and BM NK progenitors. Functionally, we measured the IFN-γ secretion of splenic NK cells after PMA/Ionomycin stimulation. We found that the percentage of IFN-γ positive NK cells decreased significantly in c-MycΔ/Δ/Ncr1Cre mice (77.1 ± 7.0% vs. 53.8 ± 1.0%, N=3). Consistent with these data, the tumor surveillance was also severely impaired in this LOF model, as the number of lung metastatic sites significantly increased compared to the control mice in a B16F10 transplantation assay.In contrast to the LOF model, in our GOF model, the NK1.1+/DX5+ NK cell number in peripheral blood increased (3.1 ± 0.2% vs. 4.4 ± 0.5%, P < 0.05, N=7). Additionally, a small increase in the percentage of CD27-/CD11b+ population in NK1.1+/DX5+ cells was seen. Interestingly, however, the ability of IFN-γ secretion of splenic NK cells after PMA/Ionomycin stimulation was decreased in iMYC mice (72.8 ± 0.3% vs. 58.7 ± 1.1%, N=3), which showed the same alteration observed in c-MycΔ/Δ/Ncr1Cre mice. This result is probably not due to the impaired maturation, but rather it is the result of the higher percentage of CD27-/CD11b+ cells, which were considered terminally differentiated NK cells with lower cytotoxic functions.In summary, we found that c-Myc is essential for NK cell development, proliferation, and tumor surveillance. NK cell maturation and proliferation were impaired in the c-Myc LOF models and were boosted in the c-Myc GOF models. Our results also provide a mechanism basis for the potential application of targeting c-Myc in NK cells ex vivo or in vivo expansion, and NK-mediated immunotherapy. Future studies are needed to delineate the underlying mechanisms and explore the applications. DisclosuresNo relevant conflicts of interest to declare.

The intrinsically disordered C-terminal linker of FtsZ regulates protofilament dynamics and superstructure in vitro

The bacterial tubulin FtsZ polymerizes to form a discontinuous ring that drives bacterial cell division by directing local cell wall synthesis. FtsZ comprises a polymerizing GTPase domain, an intrinsically disordered C-terminal linker (CTL), and a C-terminal conserved peptide (CTC). FtsZ protofilaments align circumferentially in the cell, with the CTC mediating attachment to membrane-associated division proteins. The assembly of FtsZ protofilaments into dynamic clusters is critical for cell division, but the interactions between protofilaments and regulatory mechanisms that mediate cluster assembly and dynamics are unknown. Here, we describe a role for the CTL of Caulobacter crescentus FtsZ as an intrinsic regulator of lateral interactions between protofilaments in vitro FtsZ lacking its CTL (ΔCTL) shows a dramatically increased propensity to form long multifilament bundles compared with wild type (WT). ΔCTL also displays a reduced GTP hydrolysis rate compared with WT, but this altered activity does not account for bundle formation, as reducing protofilament turnover in WT is not sufficient to induce bundling. Surprisingly, binding of the membrane-anchoring protein FzlC disrupts ΔCTL bundling in a CTC-dependent manner. Moreover, the CTL affects the ability of the FtsZ curving protein FzlA to promote formation of helical bundles. We conclude that the CTL of FtsZ influences polymer structure and dynamics both through intrinsic effects on lateral interactions and turnover and by influencing extrinsic regulation of FtsZ by binding partners. Our characterization of CTL function provides a biochemical handle for understanding the relationship between FtsZ-ring structure and function in bacterial cytokinesis.

MicroRNA-126 deficiency enhanced the activation and function of CD4+ T cells by elevating IRS-1 pathway.

Recent evidence has shown that microRNA-126 (miR-126) has been involved in the development and function of immune cells, which contributed to the pathogenesis of related clinical diseases. However, the potential role of miR-126 in the development and function of CD4+ T cells remains largely unknown. Here we first found that the activation and proliferation, as well as the expression of interferon (IFN)-γ, of CD4+ T cells from miR-126 knock-down (KD) mice using the miRNA-sponge technique were enhanced significantly in vitro, compared with those in CD4+ T cells from wild-type (WT) mice. To monitor further the possible effect of miR-126 deficiency on the function of CD4+ T cells in vivo, we used dextran sulphate sodium (DSS)-induced murine model of acute autoimmune colitis and found that miR-126 deficiency could elevate the pathology of colitis. Importantly, the proportion of CD4+ T cells in splenocytes increased significantly in miR-126KD mice. Moreover, the expression levels of CD69 and CD44 on CD4+ T cells increased significantly and the expression level of CD62L decreased significantly. Of note, adoptive cell transfer assay showed that the pathology of colitis was more serious in carboxyfluorescein succinimidyl ester (CFSE)-labelled miR-126KD CD4+ T cell-transferred group, compared with that in the CFSE-labelled WT CD4+ T cells transferred group. Consistently, the expression levels of CD69 and CD44 on CFSE+ cells increased significantly. Furthermore, both the proliferation and IFN-γ secretion of CFSE+ cells also increased significantly in the CFSE-labelled miR-126KD CD4+ T cell-transferred group. Mechanistic evidence showed that the expression of insulin receptor substrate 1 (IRS-1), as a functional target of miR-126, was elevated in CD4+ T cells from miR-126KD mice, accompanied by altered transduction of the extracellular regulated kinase, protein B (AKT) and nuclear factor kappa B (NF-κB) pathway. Our data revealed a novel role in which miR-126 was an intrinsic regulator in the function of CD4+ T cells, which provided preliminary basis for exploring further the role of miR-126 in the development, function of CD4+ T cells and related clinical diseases.

Hematopoietic (stem) cell development-how divergent are the roads taken?

The development of the hematopoietic system during early embryonic stages occurs in spatially and temporally distinct waves. Hematopoietic stem cells (HSC), the most potent and self-renewing cells of this system, are produced in the final 'definitive' wave of hematopoietic cell generation. In contrast to HSCs in the adult, which differentiate via intermediate progenitor populations to produce functional blood cells, the generation of hematopoietic cells in the embryo prior to HSC generation occurs in the early waves by producing blood cells without intermediate progenitors (such as the 'primitive' hematopoietic cells). The lineage relationship between the early hematopoietic cells and the cells giving rise to HSCs, the genetic networks controlling their emergence, and the precise temporal determination of HSC fate remain topics of intense research and debate. This Review article discusses the current knowledge on the step-wise embryonic establishment of the adult hematopoietic system, examines the roles of pivotal intrinsic regulators in this process, and raises questions concerning the temporal onset of HSC fate determination.

Wip1-dependent modulation of macrophage migration and phagocytosis

Macrophage accumulation within the vascular wall is a hallmark of atherosclerosis. Controlling macrophage conversion into foam cells remains a major challenge for treatment of atherosclerotic diseases. Here, we show that Wip1, a member of the PP2C family of Ser/Thr protein phosphatases, modulates macrophage migration and phagocytosis associated with atherosclerotic plaque formation. Wip1 deficiency increases migratory and phagocytic activities of the macrophage under stress conditions. Enhanced migration of Wip1-/- macrophages is mediated by Rac1-GTPase and PI3K/AKT signalling pathways. Elevated phagocytic ability of Wip1-/- macrophages is linked to CD36 plasma membrane recruitment that is regulated by AMPK activity. Our study identifies Wip1 as an intrinsic negative regulator of macrophage chemotaxis. We propose that Wip1-dependent control of macrophage function may provide avenues for preventing or eliminating plaque formation in atherosclerosis.

MicroRNA-150 controls differentiation of intraepithelial lymphocytes through TGF-β receptor II regulation

Intraepithelial lymphocytes (IELs) in the intestines play pivotal roles in maintaining the integrity of the mucosa, regulating immune cells, and protecting against pathogenic invasion. Although several extrinsic factors, such as TGF-β, have been identified to contribute to IEL generation, intrinsic regulatory factors have not been determined fully. Here we investigated the regulation of IEL differentiation and the underlying mechanisms in mice. We analyzed IELs and the expression of molecules associated with IEL differentiation in wild-type control and microRNA (miRNA)-150 knockout mice. Methotrexate was administered to mice lacking miR-150 and control mice. miR-150 deficiency reduced the IEL population in the small intestine and increased susceptibility to methotrexate-induced mucositis. Evaluation of expression of IEL differentiation-associated molecules showed that miR-150-deficient IELs exhibited decreased expression of TGF-β receptor (TGF-βR) II, CD103, CD8αα, and Runt-related transcription factor 3 in all the IEL subpopulations. The reduced expression of TGF-βRII in miR-150-deficient IELs was caused by increased expression of c-Myb/miR-20a. Restoration of miR-150 or inhibition of miR-20a recovered the TGF-βRII expression. miR-150 is an intrinsic regulator of IEL differentiation through TGF-βRII regulation. miR-150-mediated IEL generation is crucial for maintaining intestinal integrity against anticancer drug-induced mucositis.

An intrinsic mechanism controls reactivation of neural stem cells by spindle matrix proteins

The switch between quiescence and proliferation is central for neurogenesis and its alteration is linked to neurodevelopmental disorders such as microcephaly. However, intrinsic mechanisms that reactivate Drosophila larval neural stem cells (NSCs) to exit from quiescence are not well established. Here we show that the spindle matrix complex containing Chromator (Chro) functions as a key intrinsic regulator of NSC reactivation downstream of extrinsic insulin/insulin-like growth factor signalling. Chro also prevents NSCs from re-entering quiescence at later stages. NSC-specific in vivo profiling has identified many downstream targets of Chro, including a temporal transcription factor Grainy head (Grh) and a neural stem cell quiescence-inducing factor Prospero (Pros). We show that spindle matrix proteins promote the expression of Grh and repress that of Pros in NSCs to govern their reactivation. Our data demonstrate that nuclear Chro critically regulates gene expression in NSCs at the transition from quiescence to proliferation.

Abstract 419: OLA1 Regulates GSK3β/eIF2-alpha Signaling Axis in Angiotensin II-treated Human Ventricular Cardiomyocytes

Pathological cardiac hypertrophy in response to stress or disease such as hypertension, myocardial infarction, valvular disease or neurohomonal dysregulation often result in heart failure. Cardiac hypertrophy is associated with changes in key molecular features including protein synthesis, sarcomeric organization, fibrogenesis, cell death and energy metabolism. OBG like ATPase 1 (OLA1) belongs to the translation factor-related (TRAFAC) class, Obg family, and YchF subfamily of P-loop GTPases that play a crucial role in the regulation of diverse cellular processes including protein translation, intracellular transport, signal transduction and growth. Recent study has shown that OLA1 functions as an intrinsic regulator in cellular stress responses, such as oxidative stress and heat shock. However, its role in cardiac hypertrophy is unknown so far. Here, we investigated the effect of OLA1 deficiency on angiotensin II (ANG II)-induced hypertrophic signaling response in immortalized human ventricular cardiomyocytes (hCM) and in heart tissue from OLA1 knockout mice. We observed that ANG II-induced increase in cardiomyocyte cell size was lower in OLA1 knockdown hCM cells as compared to control transfected cells. Interestingly, OLA1 knockdown inhibits the above effect and increases phosphorylation of GSK3β and eIF2α (inactive state). Furthermore, OLA1 homozygous knockout mice showed increase in phosphorylation of GSK3β. Taken together, these findings show that OLA1 deficiency decreases ANG II-induced hypertrophy signaling response in ventricular cardiomyocytes. This study provides the first evidence for the role of OLA1 in ANG II-induced hypertrophic response of human ventricular cardiomyocytes.