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1.  SIRT7 Represses Myc Activity to Suppress ER Stress and Prevent Fatty Liver Disease 
Cell reports  2013;5(3):654-665.
SUMMARY
Nonalcoholic fatty liver disease is the most common chronic liver disorder in developed countries. Its pathogenesis is poorly understood, and therapeutic options are limited. Here we show that SIRT7, an NAD+-dependent H3K18Ac deacetylase, functions at chromatin to suppress ER stress and prevents the development of fatty liver disease. SIRT7 is induced upon ER stress and is stabilized at the promoters of ribosomal proteins through its interaction with the transcription factor Myc to silence gene expression and to relieve ER stress. SIRT7 deficient mice develop chronic hepatosteatosis resembling human fatty liver disease. Myc inactivation or pharmacological suppression of ER stress alleviates fatty liver caused by SIRT7 deficiency. Importantly, SIRT7 suppresses ER stress and reverts the fatty liver disease in diet-induced obese mice. Our study identifies SIRT7 as a cofactor of Myc for transcriptional repression and delineates a druggable regulatory branch of the ER stress response that prevents and reverts fatty liver disease.
doi:10.1016/j.celrep.2013.10.007
PMCID: PMC3888240  PMID: 24210820
2.  Multiple knockout mouse models reveal lincRNAs are required for life and brain development 
eLife  2013;2:e01749.
Many studies are uncovering functional roles for long noncoding RNAs (lncRNAs), yet few have been tested for in vivo relevance through genetic ablation in animal models. To investigate the functional relevance of lncRNAs in various physiological conditions, we have developed a collection of 18 lncRNA knockout strains in which the locus is maintained transcriptionally active. Initial characterization revealed peri- and postnatal lethal phenotypes in three mutant strains (Fendrr, Peril, and Mdgt), the latter two exhibiting incomplete penetrance and growth defects in survivors. We also report growth defects for two additional mutant strains (linc–Brn1b and linc–Pint). Further analysis revealed defects in lung, gastrointestinal tract, and heart in Fendrr−/− neonates, whereas linc–Brn1b−/− mutants displayed distinct abnormalities in the generation of upper layer II–IV neurons in the neocortex. This study demonstrates that lncRNAs play critical roles in vivo and provides a framework and impetus for future larger-scale functional investigation into the roles of lncRNA molecules.
DOI: http://dx.doi.org/10.7554/eLife.01749.001
eLife digest
The mammalian genome is comprised of DNA sequences that contain the templates for proteins, and other DNA sequences that do not code for proteins. The coding DNA sequences are transcribed to make messenger RNA molecules, which are then translated to make proteins. Researchers have known for many years that some of the noncoding DNA sequences are also transcribed to make other types of RNA molecules, such as transfer and ribosomal RNA. However, the true breadth and diversity of the roles played by these other RNA molecules have only recently begun to be fully appreciated.
Mammalian genomes contain thousands of noncoding DNA sequences that are transcribed. Recent in vitro studies suggest that the resulting long noncoding RNA molecules can act as regulators of transcription, translation, and cell cycle. In vitro studies also suggest that these long noncoding RNA molecules may play a role in mammalian development and disease. Yet few in vivo studies have been performed to support or confirm such hypotheses.
Now Sauvageau et al. have developed several lines of knockout mice to investigate a subset of noncoding RNA molecules known as long intergenic noncoding RNAs (lincRNAs). These experiments reveal that lincRNAs have a strong influence on the overall viability of mice, and also on a number of developmental processes, including the development of lungs and the cerebral cortex.
Given that the vast majority of the human genome is transcribed, the mouse models developed by Sauvageau et al. represent an important step in determining the physiological relevance, on a genetic level, of the noncoding portion of the genome in vivo.
DOI: http://dx.doi.org/10.7554/eLife.01749.002
doi:10.7554/eLife.01749
PMCID: PMC3874104  PMID: 24381249
long noncoding RNAs; knockout mouse models; lethality; developmental defect; brain development; Mouse
3.  Ric-8 Proteins Are Molecular Chaperones That Direct Nascent G Protein α Subunit Membrane Association 
Science signaling  2011;4(200):10.1126/scisignal.2002223.
Ric-8A (resistance to inhibitors of cholinesterase 8A) and Ric-8B are guanine nucleotide exchange factors that enhance different heterotrimeric guanine nucleotide–binding protein (G protein) signaling pathways by unknown mechanisms. Because transgenic disruption of Ric-8A or Ric-8B in mice caused early embryonic lethality, we derived viable Ric-8A– or Ric-8B–deleted embryonic stem (ES) cell lines from blastocysts of these mice. We observed pleiotropic G protein signaling defects in Ric-8A−/− ES cells, which resulted from reduced steady-state amounts of Gαi, Gαq, and Gα13 proteins to <5% of those of wild-type cells. The amounts of Gαs and total Gβ protein were partially reduced in Ric-8A−/− cells compared to those in wild-type cells, and only the amount of Gαs was reduced substantially in Ric-8B−/− cells. The abundances of mRNAs encoding the G protein α subunits were largely unchanged by loss of Ric-8A or Ric-8B. The plasma membrane residence of G proteins persisted in the absence of Ric-8 but was markedly reduced compared to that in wild-type cells. Endogenous Gαi and Gαq were efficiently translated in Ric-8A−/− cells but integrated into endomembranes poorly; however, the reduced amounts of G protein α subunits that reached the membrane still bound to nascent Gβγ. Finally, Gαi, Gαq, and Gβ1 proteins exhibited accelerated rates of degradation in Ric-8A−/− cells compared to those in wild-type cells. Together, these data suggest that Ric-8 proteins are molecular chaperones required for the initial association of nascent Gα subunits with cellular membranes.
doi:10.1126/scisignal.2002223
PMCID: PMC3870195  PMID: 22114146
4.  Interleukin-22 promotes fibroblast- mediated wound repair in the skin 
Skin wound repair requires complex and highly coordinated interactions between keratinocytes, fibroblasts and immune cells to restore the epidermal barrier and tissue architecture after acute injury. The cytokine interleukin-22 (IL-22) mediates unidirectional signaling from immune cells to epithelial cells during injury of peripheral tissues such as the liver and colon, where IL-22 causes epithelial cells to produce anti-bacterial proteins, express mucins, and enhance epithelial regeneration. In this study, we use IL-22−/− mice to investigate the in vivo role for IL-22 in acute skin wounding. We find that IL-22−/− mice display major defects in the skin’s dermal compartment after full thickness wounding. We find that IL-22 signaling is active in fibroblasts using in vitro assays with primary fibroblasts and that IL-22 directs extracellular matrix (ECM) gene expression as well as myofibroblast differentiation both in vitro and in vivo. These data define roles of IL-22 beyond epithelial crosstalk, and suggest that IL-22 plays a previously unidentified role in skin repair by mediating interactions between immune cells and fibroblasts.
doi:10.1038/jid.2012.463
PMCID: PMC3610794  PMID: 23223145
Interleukin 22; Wound Healing; Fibroblasts; extracellular matrix
5.  The mammalian gene function resource: the international knockout mouse consortium 
Bradley, Allan | Anastassiadis, Konstantinos | Ayadi, Abdelkader | Battey, James F. | Bell, Cindy | Birling, Marie-Christine | Bottomley, Joanna | Brown, Steve D. | Bürger, Antje | Bult, Carol J. | Bushell, Wendy | Collins, Francis S. | Desaintes, Christian | Doe, Brendan | Economides, Aris | Eppig, Janan T. | Finnell, Richard H. | Fletcher, Colin | Fray, Martin | Frendewey, David | Friedel, Roland H. | Grosveld, Frank G. | Hansen, Jens | Hérault, Yann | Hicks, Geoffrey | Hörlein, Andreas | Houghton, Richard | Hrabé de Angelis, Martin | Huylebroeck, Danny | Iyer, Vivek | de Jong, Pieter J. | Kadin, James A. | Kaloff, Cornelia | Kennedy, Karen | Koutsourakis, Manousos | Kent Lloyd, K. C. | Marschall, Susan | Mason, Jeremy | McKerlie, Colin | McLeod, Michael P. | von Melchner, Harald | Moore, Mark | Mujica, Alejandro O. | Nagy, Andras | Nefedov, Mikhail | Nutter, Lauryl M. | Pavlovic, Guillaume | Peterson, Jane L. | Pollock, Jonathan | Ramirez-Solis, Ramiro | Rancourt, Derrick E. | Raspa, Marcello | Remacle, Jacques E. | Ringwald, Martin | Rosen, Barry | Rosenthal, Nadia | Rossant, Janet | Ruiz Noppinger, Patricia | Ryder, Ed | Schick, Joel Zupicich | Schnütgen, Frank | Schofield, Paul | Seisenberger, Claudia | Selloum, Mohammed | Simpson, Elizabeth M. | Skarnes, William C. | Smedley, Damian | Stanford, William L. | Francis Stewart, A. | Stone, Kevin | Swan, Kate | Tadepally, Hamsa | Teboul, Lydia | Tocchini-Valentini, Glauco P. | Valenzuela, David | West, Anthony P. | Yamamura, Ken-ichi | Yoshinaga, Yuko | Wurst, Wolfgang
Mammalian Genome  2012;23(9-10):580-586.
In 2007, the International Knockout Mouse Consortium (IKMC) made the ambitious promise to generate mutations in virtually every protein-coding gene of the mouse genome in a concerted worldwide action. Now, 5 years later, the IKMC members have developed high-throughput gene trapping and, in particular, gene-targeting pipelines and generated more than 17,400 mutant murine embryonic stem (ES) cell clones and more than 1,700 mutant mouse strains, most of them conditional. A common IKMC web portal (www.knockoutmouse.org) has been established, allowing easy access to this unparalleled biological resource. The IKMC materials considerably enhance functional gene annotation of the mammalian genome and will have a major impact on future biomedical research.
doi:10.1007/s00335-012-9422-2
PMCID: PMC3463800  PMID: 22968824
6.  Mice completely lacking immunoproteasomes display major alterations in antigen presentation 
Nature Immunology  2011;13(2):129-135.
The importance of immunoproteasomes to antigen presentation has been unclear because animals totally lacking immunoproteasomes have not been previously developed. Here we show that dendritic cells from mice lacking the three immunoproteasome catalytic subunits display defects in presenting multiple major histocompatability (MHC) class I epitopes. During viral infection in vivo, the presentation of a majority of MHC class I epitopes is markedly reduced in immunoproteasome-deficient animals, while presentation of MHC class II peptides is unaffected. By mass spectrometry the repertoire of MHC class I-presented peptides is ~50% different and these differences are sufficient to stimulate robust transplant rejection of wild type cells in mutant mice. These results indicate that immunoproteasomes play a much more important role in antigen presentation than previously thought.
doi:10.1038/ni.2203
PMCID: PMC3262888  PMID: 22197977
7.  Innate and adaptive interleukin-22 protects mice from inflammatory bowel disease 
Immunity  2008;29(6):947-957.
Inflammatory bowel disease (IBD) is a chronic inflammatory disease thought to be mediated by dysfunctional innate and/or adaptive immunity. This aberrant immune response leads to the secretion of harmful cytokines that destroy the epithelium of the gastrointestinal tract leading to further inflammation. IL-22 is a Th17 T cell associated cytokine that is bi-functional with both pro-inflammatory and protective effects on tissues depending on the inflammatory context. We show herein that IL-22 protects mice from IBD. Interestingly, this protection is not only mediated by CD4 T cells, but IL-22 expressing NK cells also confer protection. In addition, IL-22 expression is differentially regulated between NK cell subsets. Thus, both the innate and adaptive immune responses have developed protective mechanisms to counteract the damaging effects of inflammation on tissues.
doi:10.1016/j.immuni.2008.11.003
PMCID: PMC3269819  PMID: 19100701
8.  Abnormal response to stress and impaired NPS-induced hyperlocomotion, anxiolytic effect and corticosterone increase in mice lacking NPSR1 
Psychoneuroendocrinology  2010;35(8):1119-1132.
Summary
NPSR1 is a G protein coupled receptor expressed in multiple brain regions involved in modulation of stress. Central administration of NPS, the putative endogenous ligand of NPSR1, can induce hyperlocomotion, anxiolytic effects and activation of the HPA axis. The role of NPSR1 in the brain remains unsettled. Here we used NPSR1 gene-targeted mice to define the functional role of NPSR1 under basal conditions on locomotion, anxiety- and/or depression-like behavior, corticosterone levels, acoustic startle with prepulse inhibition, learning and memory, and under NPS-induced locomotor activation, anxiolysis, and corticosterone release. Male, but not female, NPSR1-deficient mice exhibited enhanced depression-like behavior in a forced swim test, reduced acoustic startle response, and minor changes in the Morris water maze. Neither male nor female NPSR1-deficient mice showed alterations of baseline locomotion, anxiety-like behavior, or corticosterone release after exposure to a forced swim test or methamphetamine challenge in an open-field. After intracerebroventricular (ICV) administration of NPS, NPSR1-deficient mice failed to show normal NPS-induced increases in locomotion, anxiolysis, or corticosterone release compared with WT NPS-treated mice. These findings demonstrate that NPSR1 is essential in mediating NPS effects on behavior.
doi:10.1016/j.psyneuen.2010.01.012
PMCID: PMC2888805  PMID: 20171785
neuropeptide S; neuropeptide S receptor; NPSR1; stress; anxiety; depression; locomotor activity; corticosterone
9.  Postsymptomatic restoration of SMN rescues the disease phenotype in a mouse model of severe spinal muscular atrophy 
The Journal of Clinical Investigation  2011;121(8):3029-3041.
Spinal muscular atrophy (SMA) is a common neuromuscular disorder in humans. In fact, it is the most frequently inherited cause of infant mortality, being the result of mutations in the survival of motor neuron 1 (SMN1) gene that reduce levels of SMN protein. Restoring levels of SMN protein in individuals with SMA is perceived to be a viable therapeutic option, but the efficacy of such a strategy once symptoms are apparent has not been determined. We have generated mice harboring an inducible Smn rescue allele and used them in a model of SMA to investigate the effects of turning on SMN expression at different time points during the course of the disease. Restoring SMN protein even after disease onset was sufficient to reverse neuromuscular pathology and effect robust rescue of the SMA phenotype. Importantly, our findings also indicated that there was a therapeutic window of opportunity from P4 through P8 defined by the extent of neuromuscular synapse pathology and the ability of motor neurons to respond to SMN induction, following which restoration of the protein to the organism failed to produce therapeutic benefit. Nevertheless, our results suggest that even in severe SMA, timely reinstatement of the SMN protein may halt the progression of the disease and serve as an effective postsymptomatic treatment.
doi:10.1172/JCI57291
PMCID: PMC3148744  PMID: 21785219
10.  Role of the Leucine-rich Repeat (LRR) Domain of Cryopyrin/NALP3 in Monosodium Urate Crystal-induced Inflammation 
Arthritis and rheumatism  2010;62(7):2170-2179.
Objectives
The mechanism by which MSU crystals intracellularly activate the Cryopyrin inflammasome is unknown. Here, we used a mouse molecular genetics-based approach to test if the LRR domain of Cyopyrin is required for MSU crystal-induced inflammation.
Methods
Cryopyrin knockout lacZ (Cryo−Z/−Z) and LRR deletion lacZ (CryoΔLRR Z/ΔLRR Z) mice were generated using BAC-based targeting vectors, which allow for large genomic deletions. Bone marrow-derived macrophages (BMDMs) from CryoΔLRR Z/ΔLRR Z, Cryo−Z/−Z, and their congenic wildtype (WT) mice were challenged with endotoxin-free MSU crystals under serum-free conditions. Phagocytosis and cytokine expression were assessed by flow cytometry and ELISA analysis. MSU crystals also were injected into mouse synovial-like subcutaneous air pouches. The in vivo inflammatory responses were examined.
Results
Release of IL-1β, but not CXCL1 and TNFα, was impaired in CryoΔLRR Z/ΔLRR Z and Cryo−Z/−Z BMDMs compared to WT BMDMs in response to not only MSU crystals but also other known stumuli that activate the cryopyrin inflammasome. In addition, comparable percentage of MSU crystals taken up by each type of BMDMs was observed. Moreover, total leukocytes infiltrated in the air pouch and IL-1β production were attenuated in Cryo−Z/−Z and CryoΔLRR Z/ΔLRR Z mice at 6 h post-injection of MSU crystals compared to WT mice.
Conclusions
MSU crystal-induced inflammatory responses were comparably attenuated both in vitro and in vivo in CryoΔLRR Z/ΔLRR Z and Cryo−Z/−Z mice. Hence, the LRR domain of Cryopyrin plays a role in mediating MSU crystal-induced inflammation in this model.
doi:10.1002/art.27456
PMCID: PMC2929807  PMID: 20506351
11.  Slitrk5 deficiency impairs corticostriatal circuitry and leads to obsessive-compulsive–like behaviors in mice 
Nature medicine  2010;16(5):598-602.
Obsessive-compulsive disorder (OCD) is a common psychiatric disorder defined by the presence of obsessive thoughts and repetitive compulsive actions, and it often encompasses anxiety and depressive symptoms1,2. Recently, the corticostriatal circuitry has been implicated in the pathogenesis of OCD3,4. However, the etiology, pathophysiology and molecular basis of OCD remain unknown. Several studies indicate that the pathogenesis of OCD has a genetic component5–8. Here we demonstrate that loss of a neuron-specific transmembrane protein, SLIT and NTRK-like protein-5 (Slitrk5), leads to OCD-like behaviors in mice, which manifests as excessive self-grooming and increased anxiety-like behaviors, and is alleviated by the selective serotonin reuptake inhibitor fluoxetine. Slitrk5−/− mice show selective overactivation of the orbitofrontal cortex, abnormalities in striatal anatomy and cell morphology and alterations in glutamate receptor composition, which contribute to deficient corticostriatal neurotransmission. Thus, our studies identify Slitrk5 as an essential molecule at corticostriatal synapses and provide a new mouse model of OCD-like behaviors.
doi:10.1038/nm.2125
PMCID: PMC2907076  PMID: 20418887
12.  Angiomodulin is a specific marker of vasculature and regulates VEGF-A dependent neo-angiogenesis 
Circulation research  2009;105(2):201-208.
Blood vessel formation is controlled by the balance between pro- and anti-angiogenic pathways. Although much is known about the factors that drive sprouting of neovessels, the factors that stabilize and pattern neovessels are undefined. The expression of angiomodulin (AGM), a VEGF-A binding protein, was increased in the vasculature of several human tumors as compared to normal tissue, raising the hypothesis that AGM may modulate VEGF-A-dependent vascular patterning. To elucidate the expression pattern of AGM, we developed an AGM knockin reporter mouse (AGMlacZ/+) wherein we demonstrate that AGM is predominantly expressed in the vasculature of developing embryos and adult organs. During physiological and pathological angiogenesis, AGM is upregulated in the angiogenic vasculature. Using the zebrafish model, we found that AGM is restricted to developing vasculature by 17-22 hpf. Blockade of AGM activity with morpholino oligomers (MO) results in prominent angiogenesis defects in vascular sprouting and remodeling. Concurrent knockdown of both AGM and VEGF-A results in synergistic angiogenesis defects. When VEGF-A is overexpressed, the compensatory induction of the VEGF-A receptor, VEGFR-2/flk-1, is blocked by the simultaneous injection of AGM MO. These results demonstrate that the vascular-specific marker AGM modulates vascular remodeling in part by temporizing the pro-angiogenic effects of VEGF-A.
doi:10.1161/CIRCRESAHA.109.196790
PMCID: PMC2936249  PMID: 19542015
Angiomodulin; IGFBP-7; angiogenesis; VEGF; zebrafish
13.  Generation of functional multipotent adult stem cells from GPR125+ germline progenitors 
Nature  2007;449(7160):346-350.
Adult mammalian testis is a source of pluripotent stem cells1. However, the lack of specific surface markers has hampered identification and tracking of the unrecognized subset of germ cells that gives rise to multipotent cells2. Although embryonic-like cells can be derived from adult testis cultures after only several weeks in vitro1, it is not known whether adult self-renewing spermatogonia in long-term culture can generate such stem cells as well. Here, we show that highly proliferative adult spermatogonial progenitor cells (SPCs) can be efficiently obtained by cultivation on mitotically inactivated testicular feeders containing CD34+ stromal cells. SPCs exhibit testicular repopulating activity in vivo and maintain the ability in long-term culture to give rise to multi-potent adult spermatogonial-derived stem cells (MASCs). Furthermore, both SPCs and MASCs express GPR125, an orphan adhesion-type G-protein-coupled receptor. In knock-in mice bearing a GPR125–β-galactosidase (LacZ) fusion protein under control of the native Gpr125 promoter (GPR125–LacZ), expression in the testis was detected exclusively in spermatogonia and not in differentiated germ cells. Primary GPR125–LacZ SPC lines retained GPR125 expression, underwent clonal expansion, maintained the phenotype of germline stem cells, and reconstituted spermatogenesis in busulphan-treated mice. Long-term cultures of GPR125+ SPCs (GSPCs) also converted into GPR125+ MASC colonies. GPR125+MASCs generated derivatives of the three germ layers and contributed to chimaeric embryos, with concomitant downregulation of GPR125 during differentiation into GPR125− cells. MASCs also differentiated into contractile cardiac tissue in vitro and formed functional blood vessels in vivo. Molecular book marking by GPR125 in the adult mouse and, ultimately, in the human testis could enrich for a population of SPCs for derivation of GPR125+ MASCs, which may be employed for genetic manipulation, tissue regeneration and revascularization of ischaemic organs.
doi:10.1038/nature06129
PMCID: PMC2935199  PMID: 17882221
14.  TLR8 deficiency leads to autoimmunity in mice 
The Journal of Clinical Investigation  2010;120(10):3651-3662.
TLRs play an essential role in the induction of immune responses by detecting conserved molecular products of microorganisms. However, the function of TLR8 is largely unknown. In the current study, we investigated the role of TLR8 signaling in immunity in mice. We found that Tlr8–/– DCs overexpressed TLR7, were hyperresponsive to various TLR7 ligands, and showed stronger and faster NF-κB activation upon stimulation with the TLR7 ligand R848. Tlr8–/– mice showed splenomegaly, defective development of marginal zone (MZ) and B1 B cells, and increased serum levels of IgM and IgG2a. Furthermore, Tlr8–/– mice exhibited increased serum levels of autoantibodies against small nuclear ribonucleoproteins, ribonucleoprotein, and dsDNA and developed glomerulonephritis, whereas neither Tlr7–/– nor Tlr8–/–Tlr7–/– mice showed any of the phenotypes observed in Tlr8–/– mice. These data provide evidence for a pivotal role for mouse TLR8 in the regulation of mouse TLR7 expression and prevention of spontaneous autoimmunity.
doi:10.1172/JCI42081
PMCID: PMC2947223  PMID: 20811154
15.  Goblet Cell-Derived Resistin-Like Molecule β Augments CD4+ T Cell Production of IFN-γ and Infection-Induced Intestinal Inflammation1 
The secreted goblet cell-derived protein resistin-like molecule β (RELMβ) has been implicated in divergent functions, including a direct effector function against parasitic helminths and a pathogenic function in promoting inflammation in models of colitis and ileitis. However, whether RELMβ influences CD4+ T cell responses in the intestine is unknown. Using a natural model of intestinal inflammation induced by chronic infection with gastrointestinal helminth Trichuris muris, we identify dual functions for RELMβ in augmenting CD4+ Th1 cell responses and promoting infection-induced intestinal inflammation. Following exposure to low-dose Trichuris, wild-type C57BL/6 mice exhibit persistent infection associated with robust IFN-γ production and intestinal inflammation. In contrast, infected RELMβ−/− mice exhibited a significantly reduced expression of parasite-specific CD4+ T cell-derived IFN-γ and TNF-α and failed to develop Trichuris-induced intestinal inflammation. In in vitro T cell differentiation assays, recombinant RELMβ activated macrophages to express MHC class II and secrete IL-12/23p40 and enhanced their ability to mediate Ag-specific IFN-γ expression in CD4+ T cells. Taken together, these data suggest that goblet cell-macrophage cross-talk, mediated in part by RELMβ, can promote adaptive CD4+ T cell responses and chronic inflammation following intestinal helminth infection.
PMCID: PMC2819319  PMID: 18802073
16.  During muscle atrophy, thick, but not thin, filament components are degraded by MuRF1-dependent ubiquitylation 
The Journal of Cell Biology  2009;185(6):1083-1095.
Loss of myofibrillar proteins is a hallmark of atrophying muscle. Expression of muscle RING-finger 1 (MuRF1), a ubiquitin ligase, is markedly induced during atrophy, and MuRF1 deletion attenuates muscle wasting. We generated mice expressing a Ring-deletion mutant MuRF1, which binds but cannot ubiquitylate substrates. Mass spectrometry of the bound proteins in denervated muscle identified many myofibrillar components. Upon denervation or fasting, atrophying muscles show a loss of myosin-binding protein C (MyBP-C) and myosin light chains 1 and 2 (MyLC1 and MyLC2) from the myofibril, before any measurable decrease in myosin heavy chain (MyHC). Their selective loss requires MuRF1. MyHC is protected from ubiquitylation in myofibrils by associated proteins, but eventually undergoes MuRF1-dependent degradation. In contrast, MuRF1 ubiquitylates MyBP-C, MyLC1, and MyLC2, even in myofibrils. Because these proteins stabilize the thick filament, their selective ubiquitylation may facilitate thick filament disassembly. However, the thin filament components decreased by a mechanism not requiring MuRF1.
doi:10.1083/jcb.200901052
PMCID: PMC2711608  PMID: 19506036
18.  Alternatively activated macrophage-derived RELM-α is a negative regulator of type 2 inflammation in the lung 
Differentiation and recruitment of alternatively activated macrophages (AAMacs) are hallmarks of several inflammatory conditions associated with infection, allergy, diabetes, and cancer. AAMacs are defined by the expression of Arginase 1, chitinase-like molecules, and resistin-like molecule (RELM) α/FIZZ1; however, the influence of these molecules on the development, progression, or resolution of inflammatory diseases is unknown. We describe the generation of RELM-α–deficient (Retnla−/−) mice and use a model of T helper type 2 (Th2) cytokine-dependent lung inflammation to identify an immunoregulatory role for RELM-α. After challenge with Schistosoma mansoni (Sm) eggs, Retnla−/− mice developed exacerbated lung inflammation compared with their wild-type counterparts, characterized by excessive pulmonary vascularization, increased size of egg-induced granulomas, and elevated fibrosis. Associated with increased disease severity, Sm egg–challenged Retnla−/− mice exhibited elevated expression of pathogen-specific CD4+ T cell–derived Th2 cytokines. Consistent with immunoregulatory properties, recombinant RELM-α could bind to macrophages and effector CD4+ Th2 cells and inhibited Th2 cytokine production in a Bruton's tyrosine kinase–dependent manner. Additionally, Retnla−/− AAMacs promoted exaggerated antigen-specific Th2 cell differentiation. Collectively, these data identify a previously unrecognized role for AAMac-derived RELM-α in limiting the pathogenesis of Th2 cytokine-mediated pulmonary inflammation, in part through the regulation of CD4+ T cell responses.
doi:10.1084/jem.20082048
PMCID: PMC2715126  PMID: 19349464
19.  Unique functions of the type II interleukin 4 receptor identified in mice lacking the interleukin 13 receptor α1 chain 
Nature immunology  2007;9(1):25-33.
The interleukin 4 receptor (IL-4R) is a central mediator of T helper type 2 (TH2)–mediated disease and associates with either the common γ-chain to form the type I IL-4R or with the IL-13R α1 chain (IL-13Rα1) to form the type II IL-4R. Here we used Il13ra1−/− mice to characterize the distinct functions of type I and type II IL-4 receptors in vivo. In contrast to Il4ra−/− mice, which have weak TH2 responses, Il13ra1−/− mice had exacerbated TH2 responses. Il13ra1−/− mice showed much less mortality after infection with Schistosoma mansoni and much more susceptibility to Nippostrongylus brasiliensis. IL-13Rα1 was essential for allergen-induced airway hyperreactivity and mucus hypersecretion but not for fibroblast or alternative macrophage activation. Thus, type I and II IL-4 receptors exert distinct effects on immune responses.
doi:10.1038/ni1544
PMCID: PMC2692551  PMID: 18066066
20.  The transcription factor NFATc2 controls IL-6–dependent T cell activation in experimental colitis 
The Journal of Experimental Medicine  2008;205(9):2099-2110.
The nuclear factor of activated T cells (NFAT) family of transcription factors controls calcium signaling in T lymphocytes. In this study, we have identified a crucial regulatory role of the transcription factor NFATc2 in T cell–dependent experimental colitis. Similar to ulcerative colitis in humans, the expression of NFATc2 was up-regulated in oxazolone-induced chronic intestinal inflammation. Furthermore, NFATc2 deficiency suppressed colitis induced by oxazolone administration. This finding was associated with enhanced T cell apoptosis in the lamina propria and strikingly reduced production of IL-6, -13, and -17 by mucosal T lymphocytes. Further studies using knockout mice showed that IL-6, rather than IL-23 and -17, are essential for oxazolone colitis induction. Administration of hyper-IL-6 blocked the protective effects of NFATc2 deficiency in experimental colitis, suggesting that IL-6 signal transduction plays a major pathogenic role in vivo. Finally, adoptive transfer of IL-6 and wild-type T cells demonstrated that oxazolone colitis is critically dependent on IL-6 production by T cells. Collectively, these results define a unique regulatory role for NFATc2 in colitis by controlling mucosal T cell activation in an IL-6–dependent manner. NFATc2 in T cells thus emerges as a potentially new therapeutic target for inflammatory bowel diseases.
doi:10.1084/jem.20072484
PMCID: PMC2526204  PMID: 18710929
21.  CD133 expression is not restricted to stem cells, and both CD133+ and CD133– metastatic colon cancer cells initiate tumors  
The Journal of Clinical Investigation  2008;118(6):2111-2120.
Colon cancer stem cells are believed to originate from a rare population of putative CD133+ intestinal stem cells. Recent publications suggest that a small subset of colon cancer cells expresses CD133, and that only these CD133+ cancer cells are capable of tumor initiation. However, the precise contribution of CD133+ tumor-initiating cells in mediating colon cancer metastasis remains unknown. Therefore, to temporally and spatially track the expression of CD133 in adult mice and during tumorigenesis, we generated a knockin lacZ reporter mouse (CD133lacZ/+), in which the expression of lacZ is driven by the endogenous CD133 promoters. Using this model and immunostaining, we discovered that CD133 expression in colon is not restricted to stem cells; on the contrary, CD133 is ubiquitously expressed on differentiated colonic epithelium in both adult mice and humans. Using Il10–/–CD133lacZ mice, in which chronic inflammation in colon leads to adenocarcinomas, we demonstrated that CD133 is expressed on a full gamut of colonic tumor cells, which express epithelial cell adhesion molecule (EpCAM). Similarly, CD133 is widely expressed by human primary colon cancer epithelial cells, whereas the CD133– population is composed mostly of stromal and inflammatory cells. Conversely, CD133 expression does not identify the entire population of epithelial and tumor-initiating cells in human metastatic colon cancer. Indeed, both CD133+ and CD133– metastatic tumor subpopulations formed colonospheres in in vitro cultures and were capable of long-term tumorigenesis in a NOD/SCID serial xenotransplantation model. Moreover, metastatic CD133– cells form more aggressive tumors and express typical phenotypic markers of cancer-initiating cells, including CD44 (CD44+CD24–), whereas the CD133+ fraction is composed of CD44lowCD24+ cells. Collectively, our data suggest that CD133 expression is not restricted to intestinal stem or cancer-initiating cells, and during the metastatic transition, CD133+ tumor cells might give rise to the more aggressive CD133– subset, which is also capable of tumor initiation in NOD/SCID mice.
doi:10.1172/JCI34401
PMCID: PMC2391278  PMID: 18497886
22.  Mammalian Sir2 Homolog SIRT3 Regulates Global Mitochondrial Lysine Acetylation▿ †  
Molecular and Cellular Biology  2007;27(24):8807-8814.
Homologs of the Saccharomyces cerevisiae Sir2 protein, sirtuins, promote longevity in many organisms. Studies of the sirtuin SIRT3 have so far been limited to cell culture systems. Here, we investigate the localization and function of SIRT3 in vivo. We show that endogenous mouse SIRT3 is a soluble mitochondrial protein. To address the function and relevance of SIRT3 in the regulation of energy metabolism, we generated and phenotypically characterized SIRT3 knockout mice. SIRT3-deficient animals exhibit striking mitochondrial protein hyperacetylation, suggesting that SIRT3 is a major mitochondrial deacetylase. In contrast, no mitochondrial hyperacetylation was detectable in mice lacking the two other mitochondrial sirtuins, SIRT4 and SIRT5. Surprisingly, despite this biochemical phenotype, SIRT3-deficient mice are metabolically unremarkable under basal conditions and show normal adaptive thermogenesis, a process previously suggested to involve SIRT3. Overall, our results extend the recent finding of lysine acetylation of mitochondrial proteins and demonstrate that SIRT3 has evolved to control reversible lysine acetylation in this organelle.
doi:10.1128/MCB.01636-07
PMCID: PMC2169418  PMID: 17923681
23.  IL-22 but not IL-17 provides protection to hepatocytes during acute liver inflammation 
Immunity  2007;27(4):647-659.
Summary
The cytokine IL-22 is primarily expressed by Th17 CD4 T cells and is highly upregulated during chronic inflammatory diseases. IL-22 receptor expression is absent on immune cells, but is instead restricted to the tissues, providing signaling directionality from the immune system to the tissues. However, the role of IL-22 in inflammatory responses has been confounded by data suggesting both pro- and ant-inflammatory functions. Herein, we provide evidence that during inflammation IL-22 plays a protective role in preventing tissue injury. Hepatocytes from mice deficient in IL-22 are highly sensitive to the detrimental immune response associated with hepatitis. Additionally, IL-22 expressing Th17 cells can provide protection during hepatitis in IL-22 deficient mice. On the other hand, IL-17, which is co-expressed with IL-22 and can induce similar cellular responses, has no observable role in liver inflammation. Our data suggest that IL-22 serves as a protective molecule to counteract the destructive nature of the immune response to limit tissue damage.
doi:10.1016/j.immuni.2007.07.023
PMCID: PMC2149911  PMID: 17919941
24.  Resistin-like molecule β regulates innate colonic function: Barrier integrity and inflammation susceptibility 
Background:
Resistin-like molecule (RELM) β is a cysteine-rich cytokine expressed in the gastrointestinal tract and implicated in insulin resistance and gastrointestinal nematode immunity; however, its function primarily remains an enigma.
Objective:
We sought to elucidate the function of RELM-β in the gastrointestinal tract.
Methods:
We generated RELM-β gene-targeted mice and examined colonic epithelial barrier function, gene expression profiles, and susceptibility to acute colonic inflammation.
Results:
We show that RELM-β is constitutively expressed in the colon by goblet cells and enterocytes and has a role in homeostasis, as assessed by alterations in colon mRNA transcripts and epithelial barrier function in the absence of RELM-β. Using acute colonic inflammatory models, we demonstrate that RELM-β has a central role in the regulation of susceptibility to colonic inflammation. Mechanistic studies identify that RELM-β regulates expression of type III regenerating gene (REG) (REG3β and γ), molecules known to influence nuclear factor κB signaling.
Conclusions:
These data define a critical role for RELM-β in the maintenance of colonic barrier function and gastrointestinal innate immunity.
Clinical implications:
These findings identify RELM-β as an important molecule in homeostatic gastrointestinal function and colonic inflammation, and as such, these results have implications for a variety of human inflammatory gastrointestinal conditions, including allergic gastroenteropathies.
doi:10.1016/j.jaci.2006.04.039
PMCID: PMC1800427  PMID: 16815164
Allergy; colitis; gastrointestinal; inflammatory; innate; IL-13; mucosal; resistin

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