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- Volume 123, Issue 5
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On the cover: Neuropathy-associated intermediate filament aggregation
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Science in Medicine
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Abstract
Many neurodegenerative disorders, including Alzheimer’s disease, Parkinson’s disease, Huntington’s disease, and frontotemporal dementia, are proteinopathies that are associated with the aggregation and accumulation of misfolded proteins. While remarkable progress has been made in understanding the triggers of these conditions, several challenges have hampered the translation of preclinical therapies targeting pathways downstream of the initiating proteinopathies. Clinical trials in symptomatic patients using therapies directed toward initiating trigger events have met with little success, prompting concerns that such therapeutics may be of limited efficacy when used in advanced stages of the disease rather than as prophylactics. Herein, we discuss gaps in our understanding of the pathological processes downstream of the trigger and potential strategies to identify common features of the downstream degenerative cascade in multiple CNS proteinopathies, which could potentially lead to the development of common therapeutic targets for multiple disorders.
Authors
Todd E. Golde, David R. Borchelt, Benoit I. Giasson, Jada Lewis
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Review Series
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Abstract
The liver has a unique and extraordinary capacity for regeneration, even in adult organisms. This regenerative potential has traditionally been attributed to the replicative capabilities of mature hepatocytes and cholangiocytes, though emerging evidence suggests that other resident liver cell types such as progenitors, liver sinusoidal endothelial cells, and hepatic stellate cells respond to liver injury and contribute to repair. These other cells types are also associated with liver scarring, dysfunction, and carcinogenesis, which suggests that appropriate regulation of these cells is a major determinant of response to liver injury. The Reviews in this series explore possible contributions of liver progenitor cells, liver sinusoidal endothelial cells, and hepatic stellate cells to liver homeostasis and repair and highlight how these processes can go awry in chronic liver injury, fibrosis, and liver cancer.
Authors
Anna Mae Diehl, John Chute
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Liver sinusoidal endothelial cells (LSECs) have long been noted to contribute to liver regeneration after liver injury. In normal liver, the major cellular source of HGF is the hepatic stellate cell, but after liver injury, HGF expression has been thought to increase markedly in proliferating LSECs. However, emerging data suggest that even after injury, LSEC expression of HGF does not increase greatly. In contrast, bone marrow progenitor cells of LSECs (BM SPCs), which are rich in HGF, are recruited to the liver after injury. This Review examines liver regeneration from the perspective that BM SPCs that have been recruited to the liver, rather than mature LSECs, drive liver regeneration.
Authors
Laurie D. DeLeve
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The liver is a complex organ that requires multiple rounds of cell fate decision for development and homeostasis throughout the lifetime. During the earliest phases of organogenesis, the liver acquires a separate lineage from the pancreas and the intestine, and subsequently, the liver bud must appropriately differentiate to form metabolic hepatocytes and cholangiocytes for proper hepatic physiology. In addition, throughout life, the liver is bombarded with chemical and pathological insults, which require the activation and correct differentiation of adult progenitor cells. This Review seeks to provide an overview of the complex signaling relationships that allow these tightly regulated processes to occur.
Authors
Luke Boulter, Wei-Yu Lu, Stuart J. Forbes
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Stem cell niches are special microenvironments that maintain stem cells and control their behavior to ensure tissue homeostasis and regeneration throughout life. The liver has a high regenerative capacity that involves stem/progenitor cells when the proliferation of hepatocytes is impaired. In recent years progress has been made in the identification of potential hepatic stem cell niches. There is evidence that hepatic progenitor cells can originate from niches in the canals of Hering; in addition, the space of Disse may also serve as a stem cell niche during fetal hematopoiesis and constitute a niche for stellate cells in adults.
Authors
Claus Kordes, Dieter Häussinger
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Recent advances in developmental biology have greatly expanded our understanding of progenitor cell programming and the fundamental roles that Sox9 plays in liver and pancreas organogenesis. In the last 2 years, several studies have dissected the behavior of the Sox9+ duct cells in adult organs, but conflicting results have left unanswered the long-standing question of whether physiologically functioning progenitors exist in adult liver and pancreas. On the other hand, increasing evidence suggests that duct cells function as progenitors in the tissue restoration process after injury, during which embryonic programs are sometimes reactivated. This article discusses the role of Sox9 in programming liver and pancreatic progenitors as well as controversies in the field.
Authors
Yoshiya Kawaguchi
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Fibrosis is an intrinsic response to chronic injury, maintaining organ integrity when extensive necrosis or apoptosis occurs. With protracted damage, fibrosis can progress toward excessive scarring and organ failure, as in liver cirrhosis. To date, antifibrotic treatment of fibrosis represents an unconquered area for drug development, with enormous potential but also high risks. Preclinical research has yielded numerous targets for antifibrotic agents, some of which have entered early-phase clinical studies, but progress has been hampered due to the relative lack of sensitive and specific biomarkers to measure fibrosis progression or reversal. Here we focus on antifibrotic approaches for liver that address specific cell types and functional units that orchestrate fibrotic wound healing responses and have a sound preclinical database or antifibrotic activity in early clinical trials. We also touch upon relevant clinical study endpoints, optimal study design, and developments in fibrosis imaging and biomarkers.
Authors
Detlef Schuppan, Yong Ook Kim
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Hepatic stellate cells are liver-specific mesenchymal cells that play vital roles in liver physiology and fibrogenesis. They are located in the space of Disse and maintain close interactions with sinusoidal endothelial cells and hepatic epithelial cells. It is becoming increasingly clear that hepatic stellate cells have a profound impact on the differentiation, proliferation, and morphogenesis of other hepatic cell types during liver development and regeneration. In this Review, we summarize and evaluate the recent advances in our understanding of the formation and characteristics of hepatic stellate cells, as well as their function in liver development, regeneration, and cancer. We also discuss how improved knowledge of these processes offers new perspectives for the treatment of patients with liver diseases.
Authors
Chunyue Yin, Kimberley J. Evason, Kinji Asahina, Didier Y.R. Stainier
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Liver cancer is an aggressive disease with a poor outcome. Several hepatic stem/progenitor markers are useful for isolating a subset of liver cells with stem cell features, known as cancer stem cells (CSCs). These cells are responsible for tumor relapse, metastasis, and chemoresistance. Liver CSCs dictate a hierarchical organization that is shared in both organogenesis and tumorigenesis. An increased understanding of the molecular signaling events that regulate cellular hierarchy and stemness, and success in defining key CSC-specific genes, have opened up new avenues to accelerate the development of novel diagnostic and treatment strategies. This Review highlights recent advances in understanding the pathogenesis of liver CSCs and discusses unanswered questions about the concept of liver CSCs.
Authors
Taro Yamashita, Xin Wei Wang
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Hindsight
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Abstract
Advances made during the last 35 years have improved our understanding of the mechanisms of steroid hormone action on bone and how physiologic, pathologic, or iatrogenic changes in hormone levels can lead to increased fracture risk. Estrogens, androgens, and glucocorticoids alter the cellular composition of bone by regulating the supply and lifespan of osteoclasts and osteoblasts. Additionally, they influence the survival of osteocytes, long-lived cells that are entombed within the mineralized matrix and mediate the homeostatic adaptation of bone to mechanical forces. Altered redox balance is a proximal underlying mechanism of some of these effects, and sex steroid deficiency or glucocorticoid excess contributes to the aging of the skeleton.
Authors
Stavros C. Manolagas
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Commentaries
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Abstract
For people with diabetes, recurrent episodes of hypoglycemia limit the brain’s ability to sense dangerously low blood sugar levels. In this issue of the
JCI , the mechanisms behind this clinical problem of hypoglycemia unawareness are addressed by Herzog et al. The authors provide compelling evidence that recurrent hypoglycemia enhances transport of lactate into the brain and, although not itself a major alternative fuel source, lactate may preserve neuronal function during hypoglycemia by maintaining neuronal glucose metabolism. These findings redefine our understanding of the brain’s metabolic adaptations that result from recurrent hypoglycemia.Authors
Marina Litvin, Amy L. Clark, Simon J. Fisher
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For decades, peripartum cardiomyopathy has remained an enigma. Despite extensive research, our understanding of how a previously healthy woman can develop lethal heart failure in the context of pregnancy remains vague. Recent work suggests that inadequacy of the cardiac microvasculature may be the primary abnormality and has implicated an antiangiogenic fragment of the nursing hormone prolactin as playing an important role. In this issue of the
JCI , Halkein et al. explore signaling downstream of this prolactin fragment and demonstrate that miR-146a is a critical mediator of the antiangiogenic effects in endothelial cells. In addition, the study uncovers unexpected exosomal transfer of this microRNA to cardiomyocytes that may affect myocardial metabolism.Authors
Ying Yang, Jessica E. Rodriguez, Richard N. Kitsis
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Autoimmunity is the consequence of the combination of genetic predisposition and environmental effects, such as infection, injury, and constitution of the gut microbiome. In this edition of the
JCI , Dai et al. describe the use of knockin technology to test the mechanism of action of a polymorphism in the protein tyrosine phosphatase nonreceptor 22 (PTPN22 ) (LYP) that is associated with susceptibility to multiple autoimmune diseases. The function of this allele, and that of a disproportionate number of autoimmune disease risk alleles, suggests that inhibitory signaling pathways that maintain B lymphocyte immune tolerance may represent an Achilles’ heel in the prevention of autoimmunity.Authors
John C. Cambier
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Muscular dystrophies are characterized by progressive muscle weakness and wasting. Among the key obstacles to the development of therapies is the absence of an assay to monitor disease progression in live animals. In this issue of the
JCI , Maguire and colleagues use noninvasive bioluminescence imaging to monitor luciferase activity in mice expressing an inducible luciferase reporter gene in satellite cells. These cells proliferate in response to degeneration, therefore increasing the level of luciferase expression in dystrophic muscle.Authors
Jennifer R. Levy, Kevin P. Campbell
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Essential hypertension, which accounts for 90%–95% of all cases of hypertension seen in the clinic, is also referred to as idiopathic hypertension, because we simply don’t understand the cause(s). Although many theories have been advanced, in the current issue of the
JCI , Gonzalez-Villalobos et al. present further evidence implicating the intrarenal renin-angiotensin system and take us one step further by proposing a mechanism underlying this pathology.Authors
Timothy L. Reudelhuber
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Evidence that the pool of insulin-producing β cells in the pancreas is reduced in both major forms of diabetes mellitus has led to efforts to understand β cell turnover in the adult pancreas. Unfortunately, previous studies have reached opposing conclusions regarding the source of new β cells during regeneration in the adult pancreas. In this issue of the
JCI , Xiao et al. use a novel mouse model for detecting new β cells derived from non–β cells to demonstrate the absence of β cell neogenesis from non–β cells during normal postnatal growth and in models of β cell regeneration. This work adds to mounting evidence that in most physiological and pathological conditions, β cell neogenesis may not make large contributions to the postnatal β cell pool — at least not in rodents.Authors
Michael S. German
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Research Articles
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Abstract
Atrial fibrillation (AF) is a highly prevalent arrhythmia with pronounced morbidity and mortality. Inward-rectifier K+ current (
IK1 ) is believed to be an important regulator of reentrant-spiral dynamics and a major component of AF-related electrical remodeling. MicroRNA-26 (miR-26) is predicted to target the gene encoding KIR2.1,KCNJ2 . We found that miR-26 was downregulated in atrial samples from AF animals and patients and this downregulation was accompanied by upregulation ofIK1 /KIR2.1 protein. miR-26 overexpression suppressed expression ofKCNJ2 /KIR2.1. In contrast, miR-26 knockdown, inhibition, or binding-site mutation enhancedKCNJ2 /KIR2.1 expression, establishingKCNJ2 as a miR-26 target. Knockdown of endogenous miR-26 promoted AF in mice, whereas adenovirus-mediated expression of miR-26 reduced AF vulnerability.Kcnj2 -specific miR-masks eliminated miR-26–mediated reductions inKcnj2 , abolishing miR-26’s protective effects, while coinjection of aKcnj2 -specific miR-mimic prevented miR-26 knockdown-associated AF in mice. Nuclear factor of activated T cells (NFAT), a known actor in AF-associated remodeling, was found to negatively regulate miR-26 transcription. Our results demonstrate that miR-26 controls the expression ofKCNJ2 and suggest that this downregulation may promote AF.Authors
Xiaobin Luo, Zhenwei Pan, Hongli Shan, Jiening Xiao, Xuelin Sun, Ning Wang, Huixian Lin, Ling Xiao, Ange Maguy, Xiao-Yan Qi, Yue Li, Xu Gao, Deli Dong, Yong Zhang, Yunlong Bai, Jing Ai, Lihua Sun, Hang Lu, Xiao-Yan Luo, Zhiguo Wang, Yanjie Lu, Baofeng Yang, Stanley Nattel
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Critically short telomeres activate p53-mediated apoptosis, resulting in organ failure and leading to malignant transformation. Mutations in genes responsible for telomere maintenance are linked to a number of human diseases. We derived induced pluripotent stem cells (iPSCs) from 4 patients with aplastic anemia or hypocellular bone marrow carrying heterozygous mutations in the telomerase reverse transcriptase (
TERT ) or the telomerase RNA component (TERC ) telomerase genes. Both mutant and control iPSCs upregulatedTERT andTERC expression compared with parental fibroblasts, but mutant iPSCs elongated telomeres at a lower rate compared with healthy iPSCs, and the deficit correlated with the mutations’ impact on telomerase activity. There was no evidence for alternative lengthening of telomere (ALT) pathway activation. Elongation varied among iPSC clones derived from the same patient and among clones from siblings harboring identical mutations. Clonal heterogeneity was linked to genetic and environmental factors, but was not influenced by residual expression of reprogramming transgenes. Hypoxia increased telomere extension in both mutant and normal iPSCs. Additionally, telomerase-mutant iPSCs showed defective hematopoietic differentiation in vitro, mirroring the clinical phenotype observed in patients and demonstrating that human telomere diseases can be modeled utilizing iPSCs. Our data support the necessity of studying multiple clones when using iPSCs to model disease.Authors
Thomas Winkler, So Gun Hong, Jake E. Decker, Mary J. Morgan, Chuanfeng Wu, William M. Hughes V, Yanqin Yang, Danny Wangsa, Hesed M. Padilla-Nash, Thomas Ried, Neal S. Young, Cynthia E. Dunbar, Rodrigo T. Calado
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Giant axonal neuropathy (GAN) is an early-onset neurological disorder caused by mutations in the
GAN gene (encoding for gigaxonin), which is predicted to be an E3 ligase adaptor. In GAN, aggregates of intermediate filaments (IFs) represent the main pathological feature detected in neurons and other cell types, including patients’ dermal fibroblasts. The molecular mechanism by which these mutations cause IFs to aggregate is unknown. Using fibroblasts from patients and normal individuals, as well asGan–/– mice, we demonstrated that gigaxonin was responsible for the degradation of vimentin IFs. Gigaxonin was similarly involved in the degradation of peripherin and neurofilament IF proteins in neurons. Furthermore, proteasome inhibition by MG-132 reversed the clearance of IF proteins in cells overexpressing gigaxonin, demonstrating the involvement of the proteasomal degradation pathway. Together, these findings identify gigaxonin as a major factor in the degradation of cytoskeletal IFs and provide an explanation for IF aggregate accumulation, the subcellular hallmark of this devastating human disease.Authors
Saleemulla Mahammad, S.N. Prasanna Murthy, Alessandro Didonna, Boris Grin, Eitan Israeli, Rodolphe Perrot, Pascale Bomont, Jean-Pierre Julien, Edward Kuczmarski, Puneet Opal, Robert D. Goldman
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CD8+ T cells (TCD8) confer protective immunity against many infectious diseases, suggesting that microbial TCD8 determinants are promising vaccine targets. Nevertheless, current T cell antigen identification approaches do not discern which epitopes drive protective immunity during active infection — information that is critical for the rational design of TCD8-targeted vaccines. We employed a proteomics-based approach for large-scale discovery of naturally processed determinants derived from a complex pathogen, vaccinia virus (VACV), that are presented by the most frequent representatives of four major HLA class I supertypes. Immunologic characterization revealed that many previously unidentified VACV determinants were recognized by smallpox-vaccinated human peripheral blood cells in a variegated manner. Many such determinants were recognized by HLA class I–transgenic mouse immune TCD8 too and elicited protective TCD8 immunity against lethal intranasal VACV infection. Notably, efficient processing and stable presentation of immune determinants as well as the availability of naive TCD8 precursors were sufficient to drive a multifunctional, protective TCD8 response. Our approach uses fundamental insights into T cell epitope processing and presentation to define targets of protective TCD8 immunity within human pathogens that have complex proteomes, suggesting that this approach has general applicability in vaccine sciences.
Authors
Pavlo Gilchuk, Charles T. Spencer, Stephanie B. Conant, Timothy Hill, Jennifer J. Gray, Xinnan Niu, Mu Zheng, John J. Erickson, Kelli L. Boyd, K. Jill McAfee, Carla Oseroff, Sine R. Hadrup, Jack R. Bennink, William Hildebrand, Kathryn M. Edwards, James E. Crowe Jr., John V. Williams, Søren Buus, Alessandro Sette, Ton N.M. Schumacher, Andrew J. Link, Sebastian Joyce
×Abstract
Hypoglycemia occurs frequently during intensive insulin therapy in patients with both type 1 and type 2 diabetes and remains the single most important obstacle in achieving tight glycemic control. Using a rodent model of hypoglycemia, we demonstrated that exposure to antecedent recurrent hypoglycemia leads to adaptations of brain metabolism so that modest increments in circulating lactate allow the brain to function normally under acute hypoglycemic conditions. We characterized 3 major factors underlying this effect. First, we measured enhanced transport of lactate both into as well as out of the brain that resulted in only a small increase of its contribution to total brain oxidative capacity, suggesting that it was not the major fuel. Second, we observed a doubling of the glucose contribution to brain metabolism under hypoglycemic conditions that restored metabolic activity to levels otherwise only observed at euglycemia. Third, we determined that elevated lactate is critical for maintaining glucose metabolism under hypoglycemia, which preserves neuronal function. These unexpected findings suggest that while lactate uptake was enhanced, it is insufficient to support metabolism as an alternate substrate to replace glucose. Lactate is, however, able to modulate metabolic and neuronal activity, serving as a “metabolic regulator” instead.
Authors
Raimund I. Herzog, Lihong Jiang, Peter Herman, Chen Zhao, Basavaraju G. Sanganahalli, Graeme F. Mason, Fahmeed Hyder, Douglas L. Rothman, Robert S. Sherwin, Kevin L. Behar
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Spontaneous antigen-specific T cell responses can be generated in hosts harboring a variety of solid malignancies, but are subverted by immune evasion mechanisms active within the tumor microenvironment. In contrast to solid tumors, the mechanisms that regulate T cell activation versus tolerance to hematological malignancies have been underexplored. A murine acute myeloid leukemia (AML) model was used to investigate antigen-specific T cell responses against AML cells inoculated i.v. versus s.c. Robust antigen-specific T cell responses were generated against AML cells after s.c., but not i.v., inoculation. In fact, i.v. AML cell inoculation prevented functional T cell activation in response to subsequent s.c. AML cell challenge. T cell dysfunction was antigen specific and did not depend on Tregs or myeloid-derived suppressor cells (MDSCs). Antigen-specific TCR-Tg CD8+ T cells proliferated, but failed to accumulate, and expressed low levels of effector cytokines in hosts after i.v. AML induction, consistent with abortive T cell activation and peripheral tolerance. Administration of agonistic anti-CD40 Ab to activate host APCs enhanced accumulation of functional T cells and prolonged survival. Our results suggest that antigen-specific T cell tolerance is a potent immune evasion mechanism in hosts with AML that can be reversed in vivo after CD40 engagement.
Authors
Long Zhang, Xiufen Chen, Xiao Liu, Douglas E. Kline, Ryan M. Teague, Thomas F. Gajewski, Justin Kline
×Abstract
Activation of the intrarenal renin-angiotensin system (RAS) can elicit hypertension independently from the systemic RAS. However, the precise mechanisms by which intrarenal Ang II increases blood pressure have never been identified. To this end, we studied the responses of mice specifically lacking kidney angiotensin-converting enzyme (ACE) to experimental hypertension. Here, we show that the absence of kidney ACE substantially blunts the hypertension induced by Ang II infusion (a model of high serum Ang II) or by nitric oxide synthesis inhibition (a model of low serum Ang II). Moreover, the renal responses to high serum Ang II observed in wild-type mice, including intrarenal Ang II accumulation, sodium and water retention, and activation of ion transporters in the loop of Henle (NKCC2) and distal nephron (NCC, ENaC, and pendrin) as well as the transporter activating kinases SPAK and OSR1, were effectively prevented in mice that lack kidney ACE. These findings demonstrate that ACE metabolism plays a fundamental role in the responses of the kidney to hypertensive stimuli. In particular, renal ACE activity is required to increase local Ang II, to stimulate sodium transport in loop of Henle and the distal nephron, and to induce hypertension.
Authors
Romer A. Gonzalez-Villalobos, Tea Janjoulia, Nicholas K. Fletcher, Jorge F. Giani, Mien T.X. Nguyen, Anne D. Riquier-Brison, Dale M. Seth, Sebastien Fuchs, Dominique Eladari, Nicolas Picard, Sebastian Bachmann, Eric Delpire, Janos Peti-Peterdi, L. Gabriel Navar, Kenneth E. Bernstein, Alicia A. McDonough
×Abstract
Multiple autoimmune diseases, including type 1 diabetes, rheumatoid arthritis, Graves disease, and systemic lupus erythematosus, are associated with an allelic variant of protein tyrosine phosphatase nonreceptor 22 (
PTPN22 ), which encodes the protein LYP. To model the human disease-linked variant LYP-R620W, we generated knockin mice expressing the analogous mutation, R619W, in the murine ortholog PEST domain phosphatase (PEP). In contrast with a previous report, we found that this variant exhibits normal protein stability, but significantly alters lymphocyte function. Aged knockin mice exhibited effector T cell expansion and transitional, germinal center, and age-related B cell expansion as well as the development of autoantibodies and systemic autoimmunity. Further, PEP-R619W affected B cell selection and B lineage–restricted variant expression and was sufficient to promote autoimmunity. Consistent with these features, PEP-R619W lymphocytes were hyperresponsive to antigen-receptor engagement with a distinct profile of tyrosine-phosphorylated substrates. Thus, PEP-R619W uniquely modulates T and B cell homeostasis, leading to a loss in tolerance and autoimmunity.Authors
Xuezhi Dai, Richard G. James, Tania Habib, Swati Singh, Shaun Jackson, Socheath Khim, Randall T. Moon, Denny Liggitt, Alejandro Wolf-Yadlin, Jane H. Buckner, David J. Rawlings
×Abstract
Increased airway smooth muscle (ASM) contractility and the development of airway hyperresponsiveness (AHR) are cardinal features of asthma, but the signaling pathways that promote these changes are poorly understood. Tyrosine phosphorylation is tightly regulated by the opposing actions of protein tyrosine kinases and phosphatases, but little is known about whether tyrosine phosphatases influence AHR. Here, we demonstrate that genetic inactivation of receptor-like protein tyrosine phosphatase J (
Ptprj ), which encodes CD148, protected mice from the development of increased AHR in two different asthma models. Surprisingly, CD148 deficiency minimally affected the inflammatory response to allergen, but significantly altered baseline pulmonary resistance. Mice specifically lacking CD148 in smooth muscle had decreased AHR, and the frequency of calcium oscillations in CD148-deficient ASM was substantially attenuated, suggesting that signaling pathway alterations may underlie ASM contractility. Biochemical analysis of CD148-deficient ASM revealed hyperphosphorylation of the C-terminal inhibitory tyrosine of SRC family kinases (SFKs), implicating CD148 as a critical positive regulator of SFK signaling in ASM. The effect of CD148 deficiency on ASM contractility could be mimicked by treatment of both mouse trachea and human bronchi with specific SFK inhibitors. Our studies identify CD148 and the SFKs it regulates in ASM as potential targets for the treatment of AHR.Authors
Tamiko R. Katsumoto, Makoto Kudo, Chun Chen, Aparna Sundaram, Elliott C. Callahan, Jing W. Zhu, Joseph Lin, Connor E. Rosen, Boryana N. Manz, Jae W. Lee, Michael A. Matthay, Xiaozhu Huang, Dean Sheppard, Arthur Weiss
×Abstract
Human
ATRX mutations are associated with cognitive deficits, developmental abnormalities, and cancer. We show that theAtrx -null embryonic mouse brain accumulates replicative damage at telomeres and pericentromeric heterochromatin, which is exacerbated by loss of p53 and linked to ATM activation. ATRX-deficient neuroprogenitors exhibited higher incidence of telomere fusions and increased sensitivity to replication stress–inducing drugs. Treatment ofAtrx -null neuroprogenitors with the G-quadruplex (G4) ligand telomestatin increased DNA damage, indicating that ATRX likely aids in the replication of telomeric G4-DNA structures. Unexpectedly, mutant mice displayed reduced growth, shortened life span, lordokyphosis, cataracts, heart enlargement, and hypoglycemia, as well as reduction of mineral bone density, trabecular bone content, and subcutaneous fat. We show that a subset of these defects can be attributed to loss of ATRX in the embryonic anterior pituitary that resulted in low circulating levels of thyroxine and IGF-1. Our findings suggest that loss of ATRX increases DNA damage locally in the forebrain and anterior pituitary and causes tissue attrition and other systemic defects similar to those seen in aging.Authors
L. Ashley Watson, Lauren A. Solomon, Jennifer Ruizhe Li, Yan Jiang, Matthew Edwards, Kazuo Shin-ya, Frank Beier, Nathalie G. Bérubé
×Abstract
Duchenne muscular dystrophy (DMD) is a degenerative skeletal muscle disease caused by mutations in dystrophin. The degree of functional deterioration in muscle stem cells determines the severity of DMD. The mitogen-activated protein kinases (MAPKs), which are inactivated by MAPK phosphatases (MKPs), represent a central signaling node in the regulation of muscle stem cell function. Here we show that the dual-specificity protein phosphatase DUSP10/MKP-5 negatively regulates muscle stem cell function in mice. MKP-5 controlled JNK to coordinate muscle stem cell proliferation and p38 MAPK to control differentiation. Genetic loss of
Mkp5 in mice improved regenerative myogenesis and dystrophin-deficientmdx mice lackingMkp5 exhibited an attenuated dystrophic muscle phenotype. Hence, enhanced promyogenic MAPK activity preserved muscle stem cell function even in the absence of dystrophin and ultimately curtailed the pathogenesis associated with DMD. These results identify MKP-5 as an essential negative regulator of the promyogenic actions of the MAPKs and suggest that MKP-5 may serve as a target to promote muscle stem cell function in the treatment of degenerative skeletal muscle diseases.Authors
Hao Shi, Mayank Verma, Lei Zhang, Chen Dong, Richard A. Flavell, Anton M. Bennett
×Abstract
Malignant melanoma is characterized by a propensity for early lymphatic and hematogenous spread. The hypoxia-inducible factor (HIF) family of transcription factors is upregulated in melanoma by key oncogenic drivers. HIFs promote the activation of genes involved in cancer initiation, progression, and metastases. Hypoxia has been shown to enhance the invasiveness and metastatic potential of tumor cells by regulating the genes involved in the breakdown of the ECM as well as genes that control motility and adhesion of tumor cells. Using a
Pten -deficient,Braf -mutant genetically engineered mouse model of melanoma, we demonstrated that inactivation of HIF1α or HIF2α abrogates metastasis without affecting primary tumor formation. HIF1α and HIF2α drive melanoma invasion and invadopodia formation through PDGFRα and focal adhesion kinase–mediated (FAK-mediated) activation of SRC and by coordinating ECM degradation via MT1-MMP and MMP2 expression. These results establish the importance of HIFs in melanoma progression and demonstrate that HIF1α and HIF2α activate independent transcriptional programs that promote metastasis by coordinately regulating cell invasion and ECM remodeling.Authors
Sara C. Hanna, Bhavani Krishnan, Sean T. Bailey, Stergios J. Moschos, Pei-Fen Kuan, Takeshi Shimamura, Lukas D. Osborne, Marni B. Siegel, Lyn M. Duncan, E. Tim O’Brien III, Richard Superfine, C. Ryan Miller, M. Celeste Simon, Kwok-Kin Wong, William Y. Kim
×Abstract
Myopia is by far the most common human eye disorder that is known to have a clear, albeit poorly defined, heritable component. In this study, we describe an autosomal-recessive syndrome characterized by high myopia and sensorineural deafness. Our molecular investigation in 3 families led to the identification of 3 homozygous nonsense mutations (p.R181X, p.S297X, and p.Q414X) in SLIT and NTRK-like family, member 6 (
SLITRK6 ), a leucine-rich repeat domain transmembrane protein. All 3 mutant SLITRK6 proteins displayed defective cell surface localization. High-resolution MRI of WT andSlitrk6 -deficient mouse eyes revealed axial length increase in the mutant (the endophenotype of myopia). Additionally, mutant mice exhibited auditory function deficits that mirrored the human phenotype. Histological investigation of WT andSlitrk6 -deficient mouse retinas in postnatal development indicated a delay in synaptogenesis inSlitrk6 -deficient animals. Taken together, our results showed that SLITRK6 plays a crucial role in the development of normal hearing as well as vision in humans and in mice and that its disruption leads to a syndrome characterized by severe myopia and deafness.Authors
Mustafa Tekin, Barry A. Chioza, Yoshifumi Matsumoto, Oscar Diaz-Horta, Harold E. Cross, Duygu Duman, Haris Kokotas, Heather L. Moore-Barton, Kazuto Sakoori, Maya Ota, Yuri S. Odaka, Joseph Foster II, F. Basak Cengiz, Suna Tokgoz-Yilmaz, Oya Tekeli, Maria Grigoriadou, Michael B. Petersen, Ajith Sreekantan-Nair, Kay Gurtz, Xia-Juan Xia, Arti Pandya, Michael A. Patton, Juan I. Young, Jun Aruga, Andrew H. Crosby
×Abstract
PCBP2 is a member of the poly(C)-binding protein (PCBP) family, which plays an important role in posttranscriptional and translational regulation by interacting with single-stranded poly(C) motifs in target mRNAs. Several PCBP family members have been reported to be involved in human malignancies. Here, we show that PCBP2 is upregulated in human glioma tissues and cell lines. Knockdown of PCBP2 inhibited glioma growth in vitro and in vivo through inhibition of cell-cycle progression and induction of caspase-3–mediated apoptosis. Thirty-five mRNAs were identified as putative PCBP2 targets/interactors using RIP-ChIP protein-RNA interaction arrays in a human glioma cell line, T98G. Four-and-a-half LIM domain 3 (
FHL3 ) mRNA was downregulated in human gliomas and was identified as a PCBP2 target. Knockdown ofPCBP2 enhanced the expression of FHL3 by stabilizing its mRNA. Overexpression of FHL3 attenuated cell growth and induced apoptosis. This study establishes a link between PCBP2 and FHL3 proteins and identifies a new pathway for regulating glioma progression.Authors
Wei Han, Zhongshuai Xin, Zhiqiang Zhao, Wen Bao, Xihua Lin, Bin Yin, Jizong Zhao, Jiangang Yuan, Boqin Qiang, Xiaozhong Peng
×Abstract
Platinum compounds display clinical activity against a wide variety of solid tumors; however, resistance to these agents is a major limitation in cancer therapy. Reduced platinum uptake and increased platinum export are examples of resistance mechanisms that limit the extent of DNA damage. Here, we report the discovery and characterization of the role of ATP11B, a P-type ATPase membrane protein, in cisplatin resistance. We found that
ATP11B expression was correlated with higher tumor grade in human ovarian cancer samples and with cisplatin resistance in human ovarian cancer cell lines.ATP11B gene silencing restored the sensitivity of ovarian cancer cell lines to cisplatin in vitro. Combined therapy of cisplatin andATP11B -targeted siRNA significantly decreased cancer growth in mice bearing ovarian tumors derived from cisplatin-sensitive and -resistant cells. In vitro mechanistic studies on cellular platinum content and cisplatin efflux kinetics indicated that ATP11B enhances the export of cisplatin from cells. The colocalization of ATP11B with fluorescent cisplatin and with vesicular trafficking proteins, such as syntaxin-6 (STX6) and vesicular-associated membrane protein 4 (VAMP4), strongly suggests that ATP11B contributes to secretory vesicular transport of cisplatin from Golgi to plasma membrane. In conclusion, inhibition ofATP11B expression could serve as a therapeutic strategy to overcome cisplatin resistance.Authors
Myrthala Moreno-Smith, J.B. Halder, Paul S. Meltzer, Tamas A. Gonda, Lingegowda S. Mangala, Rajesha Rupaimoole, Chunhua Lu, Archana S. Nagaraja, Kshipra M. Gharpure, Yu Kang, Cristian Rodriguez-Aguayo, Pablo E. Vivas-Mejia, Behrouz Zand, Rosemarie Schmandt, Hua Wang, Robert R. Langley, Nicholas B. Jennings, Cristina Ivan, Jeremy E. Coffin, Guillermo N. Armaiz, Justin Bottsford-Miller, Sang Bae Kim, Margaret S. Halleck, Mary J.C. Hendrix, William Bornman, Menashe Bar-Eli, Ju-Seog Lee, Zahid H. Siddik, Gabriel Lopez-Berestein, Anil K. Sood
×Abstract
The ordered migration of thymocytes from the cortex to the medulla is critical for the appropriate selection of the mature T cell repertoire. Most studies of thymocyte migration rely on mouse models, but we know relatively little about how human thymocytes find their appropriate anatomical niches within the thymus. Moreover, the signals that retain CD4+CD8+ double-positive (DP) thymocytes in the cortex and prevent them from entering the medulla prior to positive selection have not been identified in mice or humans. Here, we examined the intrathymic migration of human thymocytes in both mouse and human thymic stroma and found that human thymocyte subsets localized appropriately to the cortex on mouse thymic stroma and that MHC-dependent interactions between human thymocytes and mouse stroma could maintain the activation and motility of DP cells. We also showed that CXCR4 was required to retain human DP thymocytes in the cortex, whereas CCR7 promoted migration of mature human thymocytes to the medulla. Thus, 2 opposing chemokine gradients control the migration of thymocytes from the cortex to the medulla. These findings point to significant interspecies conservation in thymocyte-stroma interactions and provide the first evidence that chemokines not only attract mature thymocytes to the medulla, but also play an active role in retaining DP thymocytes in the cortex prior to positive selection.
Authors
Joanna Halkias, Heather J. Melichar, Kayleigh T. Taylor, Jenny O. Ross, Bonnie Yen, Samantha B. Cooper, Astar Winoto, Ellen A. Robey
×Abstract
Peripartum cardiomyopathy (PPCM) is a life-threatening pregnancy-associated cardiomyopathy in previously healthy women. Although PPCM is driven in part by the 16-kDa N-terminal prolactin fragment (16K PRL), the underlying molecular mechanisms are poorly understood. We found that 16K PRL induced microRNA-146a (miR-146a) expression in ECs, which attenuated angiogenesis through downregulation of
NRAS . 16K PRL stimulated the release of miR-146a–loaded exosomes from ECs. The exosomes were absorbed by cardiomyocytes, increasing miR-146a levels, which resulted in a subsequent decrease in metabolic activity and decreased expression ofErbb4 ,Notch1 , andIrak1 . Mice with cardiomyocyte-restrictedStat3 knockout (CKO mice) exhibited a PPCM-like phenotype and displayed increased cardiac miR-146a expression with coincident downregulation ofErbb4 ,Nras ,Notch1 , andIrak1 . Blocking miR-146a with locked nucleic acids or antago-miRs attenuated PPCM in CKO mice without interrupting full-length prolactin signaling, as indicated by normal nursing activities. Finally, miR-146a was elevated in the plasma and hearts of PPCM patients, but not in patients with dilated cardiomyopathy. These results demonstrate that miR-146a is a downstream-mediator of 16K PRL that could potentially serve as a biomarker and therapeutic target for PPCM.Authors
Julie Halkein, Sebastien P. Tabruyn, Melanie Ricke-Hoch, Arash Haghikia, Ngoc-Quynh-Nhu Nguyen, Michaela Scherr, Karolien Castermans, Ludovic Malvaux, Vincent Lambert, Marc Thiry, Karen Sliwa, Agnes Noel, Joseph A. Martial, Denise Hilfiker-Kleiner, Ingrid Struman
×Abstract
The mechanisms underlying adaptive resistance of melanoma to targeted therapies remain unclear. By combining ChIP sequencing with microarray-based gene profiling, we determined that
ERBB3 is upregulated by FOXD3, a transcription factor that promotes resistance to RAF inhibitors in melanoma. Enhanced ERBB3 signaling promoted resistance to RAF pathway inhibitors in cultured melanoma cell lines and in mouse xenograft models. ERBB3 signaling was dependent on ERBB2; targeting ERBB2 with lapatinib in combination with the RAF inhibitor PLX4720 reduced tumor burden and extended latency of tumor regrowth in vivo versus PLX4720 alone. These results suggest that enhanced ERBB3 signaling may serve as a mechanism of adaptive resistance to RAF and MEK inhibitors in melanoma and that cotargeting this pathway may enhance the clinical efficacy and extend the therapeutic duration of RAF inhibitors.Authors
Ethan V. Abel, Kevin J. Basile, Curtis H. Kugel III, Agnieszka K. Witkiewicz, Kaitlyn Le, Ravi K. Amaravadi, Giorgos C. Karakousis, Xiaowei Xu, Wei Xu, Lynn M. Schuchter, Jason B. Lee, Adam Ertel, Paolo Fortina, Andrew E. Aplin
×Abstract
Large regions of recurrent genomic loss are common in cancers; however, with a few well-characterized exceptions, how they contribute to tumor pathogenesis remains largely obscure. Here we identified primate-restricted imprinting of a gene cluster on chromosome 20 in the region commonly deleted in chronic myeloid malignancies. We showed that a single heterozygous 20q deletion consistently resulted in the complete loss of expression of the imprinted genes
L3MBTL1 andSGK2 , indicative of a pathogenetic role for loss of the active paternally inherited locus. Concomitant loss of bothL3MBTL1 andSGK2 dysregulated erythropoiesis and megakaryopoiesis, 2 lineages commonly affected in chronic myeloid malignancies, with distinct consequences in each lineage. We demonstrated that L3MBTL1 and SGK2 collaborated in the transcriptional regulation ofMYC by influencing different aspects of chromatin structure. L3MBTL1 is known to regulate nucleosomal compaction, and we here showed that SGK2 inactivated BRG1, a key ATP-dependent helicase within the SWI/SNF complex that regulates nucleosomal positioning. These results demonstrate a link between an imprinted gene cluster and malignancy, reveal a new pathogenetic mechanism associated with acquired regions of genomic loss, and underline the complex molecular and cellular consequences of “simple” cancer-associated chromosome deletions.Authors
Athar Aziz, E. Joanna Baxter, Carol Edwards, Clara Yujing Cheong, Mitsuteru Ito, Anthony Bench, Rebecca Kelley, Yvonne Silber, Philip A. Beer, Keefe Chng, Marilyn B. Renfree, Kirsten McEwen, Dionne Gray, Jyoti Nangalia, Ghulam J. Mufti, Eva Hellstrom-Lindberg, Jean-Jacques Kiladjian, Mary Frances McMullin, Peter J. Campbell, Anne C. Ferguson-Smith, Anthony R. Green
×Abstract
While the induction of a neutralizing antibody response against HIV remains a daunting goal, data from both natural infection and vaccine-induced immune responses suggest that it may be possible to induce antibodies with enhanced Fc effector activity and improved antiviral control via vaccination. However, the specific features of naturally induced HIV-specific antibodies that allow for the potent recruitment of antiviral activity and the means by which these functions are regulated are poorly defined. Because antibody effector functions are critically dependent on antibody Fc domain glycosylation, we aimed to define the natural glycoforms associated with robust Fc-mediated antiviral activity. We demonstrate that spontaneous control of HIV and improved antiviral activity are associated with a dramatic shift in the global antibody-glycosylation profile toward agalactosylated glycoforms. HIV-specific antibodies exhibited an even greater frequency of agalactosylated, afucosylated, and asialylated glycans. These glycoforms were associated with enhanced Fc-mediated reduction of viral replication and enhanced Fc receptor binding and were consistent with transcriptional profiling of glycosyltransferases in peripheral B cells. These data suggest that B cell programs tune antibody glycosylation actively in an antigen-specific manner, potentially contributing to antiviral control during HIV infection.
Authors
Margaret E. Ackerman, Max Crispin, Xiaojie Yu, Kavitha Baruah, Austin W. Boesch, David J. Harvey, Anne-Sophie Dugast, Erin L. Heizen, Altan Ercan, Ickwon Choi, Hendrik Streeck, Peter A. Nigrovic, Chris Bailey-Kellogg, Chris Scanlan, Galit Alter
×Abstract
Retinal vessel homeostasis ensures normal ocular functions. Consequently, retinal hypovascularization and neovascularization, causing a lack and an excess of vessels, respectively, are hallmarks of human retinal pathology. We provide evidence that EC-specific genetic ablation of either the transcription factor SRF or its cofactors MRTF-A and MRTF-B, but not the SRF cofactors ELK1 or ELK4, cause retinal hypovascularization in the postnatal mouse eye. Inducible, EC-specific deficiency of SRF or MRTF-A/MRTF-B during postnatal angiogenesis impaired endothelial tip cell filopodia protrusion, resulting in incomplete formation of the retinal primary vascular plexus, absence of the deep plexi, and persistence of hyaloid vessels. All of these features are typical of human hypovascularization-related vitreoretinopathies, such as familial exudative vitreoretinopathies including Norrie disease. In contrast, conditional EC deletion of
Srf in adult murine vessels elicited intraretinal neovascularization that was reminiscent of the age-related human pathologies retinal angiomatous proliferation and macular telangiectasia. These results indicate that angiogenic homeostasis is ensured by differential stage-specific functions of SRF target gene products in the developing versus the mature retinal vasculature and suggest that the actin-directed MRTF-SRF signaling axis could serve as a therapeutic target in the treatment of human vascular retinal diseases.Authors
Christine Weinl, Heidemarie Riehle, Dongjeong Park, Christine Stritt, Susanne Beck, Gesine Huber, Hartwig Wolburg, Eric N. Olson, Mathias W. Seeliger, Ralf H. Adams, Alfred Nordheim
×Abstract
Whether facultative β cell progenitors exist in the adult pancreas is a major unsolved question. To date, lineage-tracing studies have provided conflicting results. To track β cell neogenesis in vivo, we generated transgenic mice that transiently coexpress mTomato and GFP in a time-sensitive, nonconditional Cre-mediated manner, so that insulin-producing cells express GFP under control of the insulin promoter, while all other cells express mTomato (INSCremTmG mice). Newly differentiated β cells were detected by flow cytometry and fluorescence microscopy, taking advantage of their transient coexpression of GFP and mTomato fluorescent proteins. We found that β cell neogenesis predominantly occurs during embryogenesis, decreases dramatically shortly after birth, and is completely absent in adults across various models of β cell loss, β cell growth and regeneration, and inflammation. Moreover, we demonstrated upregulation of neurogenin 3 (NGN3) in both proliferating ducts and preexisting β cells in the ligated pancreatic tail after pancreatic ductal ligation. These results are consistent with some recent reports, but argue against the widely held belief that NGN3 marks cells undergoing endocrine neogenesis in the pancreas. Our data suggest that β cell neogenesis in the adult pancreas occurs rarely, if ever, under either normal or pathological conditions.
Authors
Xiangwei Xiao, Zean Chen, Chiyo Shiota, Krishna Prasadan, Ping Guo, Yousef El-Gohary, Jose Paredes, Carey Welsh, John Wiersch, George K. Gittes
×Abstract
During complement activation the C3 protein is cleaved, and C3 activation fragments are covalently fixed to tissues. Tissue-bound C3 fragments are a durable biomarker of tissue inflammation, and these fragments have been exploited as addressable binding ligands for targeted therapeutics and diagnostic agents. We have generated cross-reactive murine monoclonal antibodies against human and mouse C3d, the final C3 degradation fragment generated during complement activation. We developed 3 monoclonal antibodies (3d8b, 3d9a, and 3d29) that preferentially bind to the iC3b, C3dg, and C3d fragments in solution, but do not bind to intact C3 or C3b. The same 3 clones also bind to tissue-bound C3 activation fragments when injected systemically. Using mouse models of renal and ocular disease, we confirmed that, following systemic injection, the antibodies accumulated at sites of C3 fragment deposition within the glomerulus, the renal tubulointerstitium, and the posterior pole of the eye. To detect antibodies bound within the eye, we used optical imaging and observed accumulation of the antibodies within retinal lesions in a model of choroidal neovascularization (CNV). Our results demonstrate that imaging methods that use these antibodies may provide a sensitive means of detecting and monitoring complement activation–associated tissue inflammation.
Authors
Joshua M. Thurman, Liudmila Kulik, Heather Orth, Maria Wong, Brandon Renner, Siranush A. Sargsyan, Lynne M. Mitchell, Dennis E. Hourcade, Jonathan P. Hannan, James M. Kovacs, Beth Coughlin, Alex S. Woodell, Matthew C. Pickering, Bärbel Rohrer, V. Michael Holers
×Abstract
Chronic pancreatitis is an inflammatory disease that causes progressive destruction of pancreatic acinar cells and, ultimately, loss of pancreatic function. We investigated the role of IκB kinase α (IKKα) in pancreatic homeostasis. Pancreas-specific ablation of IKKα (
Ikk αΔpan ) caused spontaneous and progressive acinar cell vacuolization and death, interstitial fibrosis, inflammation, and circulatory release of pancreatic enzymes, clinical signs resembling those of human chronic pancreatitis. Loss of pancreatic IKKα causes defective autophagic protein degradation, leading to accumulation of p62-mediated protein aggregates and enhanced oxidative and ER stress in acinar cells, but none of these effects is related to NF-κB. Pancreas-specific p62 ablation prevented ER and oxidative stresses and attenuated pancreatitis inIkk αΔpan mice, suggesting that cellular stress induced by p62 aggregates promotes development of pancreatitis. Importantly, downregulation of IKKα and accumulation of p62 aggregates were also observed in chronic human pancreatitis. Our studies demonstrate that IKKα, which may control autophagic protein degradation through its interaction with ATG16L2, plays a critical role in maintaining pancreatic acinar cell homeostasis, whose dysregulation promotes pancreatitis through p62 aggregate accumulation.Authors
Ning Li, Xuefeng Wu, Ryan G. Holzer, Jun-Hee Lee, Jelena Todoric, Eek-Joong Park, Hisanobu Ogata, Anna S. Gukovskaya, Ilya Gukovsky, Donald P. Pizzo, Scott VandenBerg, David Tarin, Çiǧdem Atay, Melek C. Arkan, Thomas J. Deerinck, Jorge Moscat, Maria Diaz-Meco, David Dawson, Mert Erkan, Jörg Kleeff, Michael Karin
×Abstract
NF-κB is a master regulator of inflammation and has been implicated in the pathogenesis of immune disorders and cancer. Its regulation involves a variety of steps, including the controlled degradation of inhibitory IκB proteins. In addition, the inactivation of DNA-bound NF-κB is essential for its regulation. This step requires a factor known as copper metabolism Murr1 domain–containing 1 (COMMD1), the prototype member of a conserved gene family. While COMMD proteins have been linked to the ubiquitination pathway, little else is known about other family members. Here we demonstrate that all COMMD proteins bind to CCDC22, a factor recently implicated in X-linked intellectual disability (XLID). We showed that an XLID-associated
CCDC22 mutation decreased CCDC22 protein expression and impaired its binding to COMMD proteins. Moreover, some affected individuals displayed ectodermal dysplasia, a congenital condition that can result from developmental NF-κB blockade. Indeed, patient-derived cells demonstrated impaired NF-κB activation due to decreased IκB ubiquitination and degradation. In addition, we found that COMMD8 acted in conjunction with CCDC22 to direct the degradation of IκB proteins. Taken together, our results indicate that CCDC22 participates in NF-κB activation and that its deficiency leads to decreased IκB turnover in humans, highlighting an important regulatory component of this pathway.Authors
Petro Starokadomskyy, Nathan Gluck, Haiying Li, Baozhi Chen, Mathew Wallis, Gabriel N. Maine, Xicheng Mao, Iram W. Zaidi, Marco Y. Hein, Fiona J. McDonald, Steffen Lenzner, Agnes Zecha, Hans-Hilger Ropers, Andreas W. Kuss, Julie McGaughran, Jozef Gecz, Ezra Burstein
×Abstract
Metastatic melanoma is one of the most aggressive forms of cutaneous cancers. Although recent therapeutic advances have prolonged patient survival, the prognosis remains dismal. C-MER proto-oncogene tyrosine kinase (MERTK) is a receptor tyrosine kinase with oncogenic properties that is often overexpressed or activated in various malignancies. Using both protein immunohistochemistry and microarray analyses, we demonstrate that MERTK expression correlates with disease progression. MERTK expression was highest in metastatic melanomas, followed by primary melanomas, while the lowest expression was observed in nevi. Additionally, over half of melanoma cell lines overexpressed
MERTK compared with normal human melanocytes; however, overexpression did not correlate with mutations inBRAF orRAS . Stimulation of melanoma cells with the MERTK ligand GAS6 resulted in the activation of several downstream signaling pathways including MAPK/ERK, PI3K/AKT, and JAK/STAT. MERTK inhibition via shRNA reduced MERTK-mediated downstream signaling, reduced colony formation by up to 59%, and diminished tumor volume by 60% in a human melanoma murine xenograft model. Treatment of melanoma cells with UNC1062, a novel MERTK-selective small-molecule tyrosine kinase inhibitor, reduced activation of MERTK-mediated downstream signaling, induced apoptosis in culture, reduced colony formation in soft agar, and inhibited invasion of melanoma cells. This work establishes MERTK as a therapeutic target in melanoma and provides a rationale for the continued development of MERTK-targeted therapies.Authors
Jennifer Schlegel, Maria J. Sambade, Susan Sather, Stergios J. Moschos, Aik-Choon Tan, Amanda Winges, Deborah DeRyckere, Craig C. Carson, Dimitri G. Trembath, John J. Tentler, S. Gail Eckhardt, Pei-Fen Kuan, Ronald L. Hamilton, Lyn M. Duncan, C. Ryan Miller, Nana Nikolaishvili-Feinberg, Bentley R. Midkiff, Jing Liu, Weihe Zhang, Chao Yang, Xiaodong Wang, Stephen V. Frye, H. Shelton Earp, Janiel M. Shields, Douglas K. Graham
×Abstract
Treating neuropathic pain is a major clinical challenge, and the underlying mechanisms of neuropathic pain remain elusive. We hypothesized that neuropathic pain–inducing nerve injury may elicit neuronal alterations that recapitulate events that occur during development. Here, we report that WNT signaling, which is important in developmental processes of the nervous system, plays a critical role in neuropathic pain after sciatic nerve injury and bone cancer in rodents. Nerve injury and bone cancer caused a rapid-onset and long-lasting expression of WNTs, as well as activation of WNT/frizzled/β-catenin signaling in the primary sensory neurons, the spinal dorsal horn neurons, and astrocytes. Spinal blockade of WNT signaling pathways inhibited the production and persistence of neuropathic pain and the accompanying neurochemical alterations without affecting normal pain sensitivity and locomotor activity. WNT signaling activation stimulated production of the proinflammatory cytokines IL-18 and TNF-α and regulated the NR2B glutamate receptor and Ca2+-dependent signals through the β-catenin pathway in the spinal cord. These findings indicate a critical mechanism underlying the pathogenesis of neuropathic pain and suggest that targeting the WNT signaling pathway may be an effective approach for treating neuropathic pain, including bone cancer pain.
Authors
Yan-Kai Zhang, Zhi-Jiang Huang, Su Liu, Yue-Peng Liu, Angela A. Song, Xue-Jun Song
×Abstract
Atopic asthma is a chronic inflammatory disease of the lungs generally marked by excessive Th2 inflammation. The role of allergen-specific IgG in asthma is still controversial; however, a receptor of IgG–immune complexes (IgG-ICs), FcγRIII, has been shown to promote Th2 responses through an unknown mechanism. Herein, we demonstrate that allergen-specific IgG-ICs, formed upon reexposure to allergen, promoted Th2 responses in two different models of IC-mediated inflammation that were independent of a preformed T cell memory response. Development of Th2-type airway inflammation was shown to be both FcγRIII and TLR4 dependent, and T cells were necessary and sufficient for this process to occur, even in the absence of type 2 innate lymphoid cells. We sought to identify downstream targets of FcγRIII signaling that could contribute to this process and demonstrated that bone marrow–derived DCs, alveolar macrophages, and respiratory DCs significantly upregulated IL-33 when activated through FcγRIII and TLR4. Importantly, IC-induced Th2 inflammation was dependent on the ST2/IL-33 pathway. Our results suggest that allergen-specific IgG can enhance secondary responses by ligating FcγRIII on antigen-presenting cells to augment development of Th2-mediated responses in the lungs via an IL-33–dependent mechanism.
Authors
Melissa Y. Tjota, Jesse W. Williams, Tiffany Lu, Bryan S. Clay, Tiara Byrd, Cara L. Hrusch, Donna C. Decker, Claudia Alves de Araujo, Paul J. Bryce, Anne I. Sperling
×Abstract
Muscular dystrophies are a class of disorders that cause progressive muscle wasting. A major hurdle for discovering treatments for the muscular dystrophies is a lack of reliable assays to monitor disease progression in animal models. We have developed a novel mouse model to assess disease activity noninvasively in mice with muscular dystrophies. These mice express an inducible luciferase reporter gene in muscle stem cells. In dystrophic mice, muscle stem cells activate and proliferate in response to muscle degeneration, resulting in an increase in the level of luciferase expression, which can be monitored by noninvasive, bioluminescence imaging. We applied this noninvasive imaging to assess disease activity in a mouse model of the human disease limb girdle muscular dystrophy 2B (LGMD2B), caused by a mutation in the dysferlin gene. We monitored the natural history and disease progression in these dysferlin-deficient mice up to 18 months of age and were able to detect disease activity prior to the appearance of any overt disease manifestation by histopathological analyses. Disease activity was reflected by changes in luciferase activity over time, and disease burden was reflected by cumulative luciferase activity, which paralleled disease progression as determined by histopathological analysis. The ability to monitor disease activity noninvasively in mouse models of muscular dystrophy will be invaluable for the assessment of disease progression and the effectiveness of therapeutic interventions.
Authors
Katie K. Maguire, Leland Lim, Sedona Speedy, Thomas A. Rando
×Abstract
Eosinophils are abundant in inflammatory demyelinating lesions in neuromyelitis optica (NMO). We used cell culture, ex vivo spinal cord slices, and in vivo mouse models of NMO to investigate the role of eosinophils in NMO pathogenesis and the therapeutic potential of eosinophil inhibitors. Eosinophils cultured from mouse bone marrow produced antibody-dependent cell-mediated cytotoxicity (ADCC) in cell cultures expressing aquaporin-4 in the presence of NMO autoantibody (NMO-IgG). In the presence of complement, eosinophils greatly increased cell killing by a complement-dependent cell-mediated cytotoxicity (CDCC) mechanism. NMO pathology was produced in NMO-IgG–treated spinal cord slice cultures by inclusion of eosinophils or their granule toxins. The second-generation antihistamines cetirizine and ketotifen, which have eosinophil-stabilizing actions, greatly reduced NMO-IgG/eosinophil–dependent cytotoxicity and NMO pathology. In live mice, demyelinating NMO lesions produced by continuous intracerebral injection of NMO-IgG and complement showed marked eosinophil infiltration. Lesion severity was increased in transgenic hypereosinophilic mice. Lesion severity was reduced in mice made hypoeosinophilic by anti–IL-5 antibody or by gene deletion, and in normal mice receiving cetirizine orally. Our results implicate the involvement of eosinophils in NMO pathogenesis by ADCC and CDCC mechanisms and suggest the therapeutic utility of approved eosinophil-stabilizing drugs.
Authors
Hua Zhang, A.S. Verkman
×Abstract
Heterozygous loss-of-function
SMAD3 (Mothers against decapentaplegic homolog 3) mutations lead to aneurysm-osteoarthritis syndrome (AOS). In the present study, we found that mice lackingSmad3 had a vascular phenotype similar to AOS, marked by the progressive development of aneurysms. These aneurysms were associated with various pathological changes in transmural inflammatory cell infiltration. Bone marrow transplants fromSmad3–/– mice induced aortitis and aortic root dilation in irradiated WT recipient mice. Transplantation of CD4+ T cells fromSmad3–/– mice also induced aortitis inSmad3+/+ recipient mice, while depletion of CD4+ T cells inSmad3–/– mice reduced the infiltration of inflammatory cells in the aortic root. Furthermore, IFN-γ deficiency increased, while IL-17 deficiency decreased, disease severity inSmad3+/– mice. Cytokine secretion was measured using a cytokine quantibody array, andSmad3–/– CD4+ T cells secreted more GM-CSF thanSmad3+/+ CD4+ T cells. GM-CSF induced CD11b+Gr-1+Ly-6Chi inflammatory monocyte accumulation in the aortic root, but administration of anti–GM-CSF mAb toSmad3–/– mice resulted in significantly less inflammation and dilation in the aortic root. We also identified a missense mutation (c.985A>G) in a family of thoracic aortic aneurysms. Intense inflammatory infiltration and GM-CSF expression was observed in aortas specimens of these patients, suggesting that GM-CSF is potentially involved in the development of AOS.Authors
Ping Ye, Wenhao Chen, Jie Wu, Xiaofan Huang, Jun Li, Sihua Wang, Zheng Liu, Guohua Wang, Xiao Yang, Peng Zhang, Qiulun Lv, Jiahong Xia
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Errata
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Abstract
Authors
Mahua Chakraborty, Caixia Lou, Chongmin Huan, Ming-Shang Kuo, Tae-Sik Park, Guoqing Cao, Xian-Cheng Jiang
×Abstract
Authors
Min Luo, Xiaoqun Guan, Elizabeth D. Luczak, Di Lang, William Kutschke, Zhan Gao, Jinying Yang, Patric Glynn, Samuel Sossalla, Paari D. Swaminathan, Robert M. Weiss, Baoli Yang, Adam G. Rokita, Lars S. Maier, Igor R. Efimov, Thomas J. Hund, Mark E. Anderson
Copyright © 2025 American Society for Clinical Investigation
ISSN: 0021-9738 (print), 1558-8238 (online)