-
Zhe Li,
Hui Huang,
Patricia Boland,
Melissa G Dominguez,
Patricia Burfeind,
Ka-Man Lai,
Hsin-Chieh Lin,
Nicholas W Gale,
Christopher Daly,
Wojtek Auerbach, David Valenzuela,
George D Yancopoulos,
Gavin Thurston
[show abstract]
[hide abstract]
ABSTRACT: Inhibiting angiogenesis has become an effective approach for treating cancer and other diseases. However, our understanding of signaling pathways in tumor angiogenesis has been limited by the embryonic lethality of many gene knockouts. To overcome this limitation, we used the plasticity of embryonic stem (ES) cells to develop a unique approach to study tumor angiogenesis. Murine ES cells can be readily manipulated genetically; in addition, ES cells implanted subcutaneously in mice develop into tumors that contain a variety of cell types (teratomas). We show that ES cells differentiate into bona fide endothelial cells within the teratoma, and that these ES-derived endothelial cells form part of the functional tumor vasculature. Using this powerful and flexible system, the Angiopoietin/Tie2 system is shown to have a key role in the regulation of tumor vessel size. Endothelial differentiation in the ES teratoma model allows gene-targeting methods to be used in the study of tumor angiogenesis.
Proceedings of the National Academy of Sciences 12/2009; 106(52):22399-404. · 9.68 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: 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.
Journal of Experimental Medicine 10/2008; 205(9):2099-110. · 13.85 Impact Factor
-
David B Lombard,
Frederick W Alt,
Hwei-Ling Cheng,
Jakob Bunkenborg,
Ryan S Streeper,
Raul Mostoslavsky,
Jennifer Kim,
George Yancopoulos, David Valenzuela,
Andrew Murphy,
Yinhua Yang,
Yaohui Chen,
Matthew D Hirschey,
Roderick T Bronson,
Marcia Haigis,
Leonard P Guarente,
Robert V Farese,
Sherman Weissman,
Eric Verdin,
Bjoern Schwer
[show abstract]
[hide abstract]
ABSTRACT: 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.
Molecular and cellular biology 01/2008; 27(24):8807-14. · 6.06 Impact Factor
-
Iwona Pilecka,
Claudia Patrignani,
Rosanna Pescini,
Marie-Laure Curchod,
Dominique Perrin,
Yingzi Xue,
Jason Yasenchak,
Ann Clark,
Maria Chiara Magnone,
Paola Zaratin, David Valenzuela,
Christian Rommel,
Rob Hooft van Huijsduijnen
[show abstract]
[hide abstract]
ABSTRACT: Several protein-tyrosine phosphatases (PTPs) have been implicated in the control of growth hormone receptor (GHR) signaling, but none have been shown to affect growth in vivo. We have applied a battery of molecular and cellular approaches to test a family-wide panel of PTPs for interference with GHR signaling. Among the subset of PTPs that showed activity in multiple readouts, we selected PTP-H1/PTPN3 for further in vivo studies and found that mice lacking the PTP-H1 catalytic domain show significantly enhanced growth over their wild type littermates. In addition, PTP-H1 mutant animals had enhanced plasma and liver mRNA expression of insulin-like growth factor 1, as well as increased bone density and mineral content. These observations point to a controlling role for PTP-H1 in modulating GHR signaling and systemic growth through insulin-like growth factor 1 secretion.
Journal of Biological Chemistry 12/2007; 282(48):35405-15. · 4.77 Impact Factor
-
Vesna Todorovic,
David Frendewey,
David E Gutstein,
Yan Chen,
Laina Freyer,
Erin Finnegan,
Fangyu Liu,
Andrew Murphy, David Valenzuela,
George Yancopoulos,
Daniel B Rifkin
[show abstract]
[hide abstract]
ABSTRACT: Latent TGF-beta binding protein 1 (LTBP1) is a member of the LTBP/fibrillin family of extracellular proteins. Due to the usage of different promoters, LTBP1 exists in two major forms, long (L) and short (S), each expressed in a temporally and spatially unique fashion. Both LTBP1 molecules covalently interact with latent TGF-beta and regulate its function, presumably via interaction with the extracellular matrix (ECM). To explore the in vivo role of Ltbp1 in mouse development, at the time when only the L isoform is expressed, we mutated the Ltbp1L locus by gene targeting. Ltbp1L-null animals die shortly after birth from defects in heart development, consisting of the improper septation of the cardiac outflow tract (OFT) and remodeling of the associated vessels. These cardiac anomalies present as persistent truncus arteriosus (PTA) and interrupted aortic arch (IAA), which are associated with the faulty function of cardiac neural crest cells (CNCCs). The lack of Ltbp1L in the ECM of the septating OFT and associated vessels results in altered gene expression and function of CNCCs and decreased Tgf-beta activity in the OFT. This phenotype reveals a crucial role for Ltbp1L and matrix as extracellular regulators of Tgf-beta activity in heart organogenesis.
Development 11/2007; 134(20):3723-32. · 6.60 Impact Factor
-
Katherine E Wortley,
Karen Garcia,
Haruka Okamoto,
Karen Thabet,
Keith D Anderson,
Victor Shen,
Jim P Herman, David Valenzuela,
George D Yancopoulos,
Matthias H Tschöp,
Andrew Murphy,
Mark W Sleeman
[show abstract]
[hide abstract]
ABSTRACT: Peptide YY (PYY) and pancreatic polypeptide (PPY) are members of the neuropeptide Y peptide family. The neuropeptide Y receptor signaling pathway has been implicated in a number of physiologic processes, including the regulation of energy balance and bone mass. To investigate the contribution of endogenous PYY and PPY to these processes, we generated both Pyy- and Ppy-deficient mice.
Pyy(-/-) and Ppy(-/-) mice and their respective wild-type littermates were studied from 8 weeks to 9 months of age. Food intake, metabolic parameters, and locomotor activity were monitored using indirect calorimetry. Body composition and bone parameters were analyzed using dual energy x-ray absorptiometry, histomorphometry, and vertebral compression testing.
Studies in these mice showed an osteopenic phenotype specific to the Pyy-deficient line, which included a reduction in trabecular bone mass and a functional deficit in bone strength. Furthermore, female Pyy(-/-) mice showed a greater sensitivity to ovariectomy-induced bone loss compared with wild-type littermates. No food intake or metabolic phenotype was apparent in male or female Pyy(-/-) mice on standard chow. However, female Pyy(-/-) mice on a high-fat diet showed a greater propensity to gain body weight and adiposity. No metabolic or osteopenic phenotype was observed in Ppy-deficient mice.
These results indicate that endogenous PYY plays a critical role in regulating bone mass. In comparison, its role in regulating body weight is minor and is confined to situations of high-fat feeding.
Gastroenterology 11/2007; 133(5):1534-43. · 11.68 Impact Factor
-
To-Ha Thai,
Dinis Pedro Calado,
Stefano Casola,
K Mark Ansel,
Changchun Xiao,
Yingzi Xue,
Andrew Murphy,
David Frendewey, David Valenzuela,
Jeffery L Kutok,
Marc Schmidt-Supprian,
Nikolaus Rajewsky,
George Yancopoulos,
Anjana Rao,
Klaus Rajewsky
[show abstract]
[hide abstract]
ABSTRACT: MicroRNAs are small RNA species involved in biological control at multiple levels. Using genetic deletion and transgenic approaches, we show that the evolutionarily conserved microRNA-155 (miR-155) has an important role in the mammalian immune system, specifically in regulating T helper cell differentiation and the germinal center reaction to produce an optimal T cell-dependent antibody response. miR-155 exerts this control, at least in part, by regulating cytokine production. These results also suggest that individual microRNAs can exert critical control over mammalian differentiation processes in vivo.
Science 05/2007; 316(5824):604-8. · 31.20 Impact Factor
-
Raul Mostoslavsky,
Katrin F Chua,
David B Lombard,
Wendy W Pang,
Miriam R Fischer,
Lionel Gellon,
Pingfang Liu,
Gustavo Mostoslavsky,
Sonia Franco,
Michael M Murphy, [......], David Valenzuela,
Margaret Karow,
Michael O Hottiger,
Stephen Hursting,
J Carl Barrett,
Leonard Guarente,
Richard Mulligan,
Bruce Demple,
George D Yancopoulos,
Frederick W Alt
[show abstract]
[hide abstract]
ABSTRACT: The Sir2 histone deacetylase functions as a chromatin silencer to regulate recombination, genomic stability, and aging in budding yeast. Seven mammalian Sir2 homologs have been identified (SIRT1-SIRT7), and it has been speculated that some may have similar functions to Sir2. Here, we demonstrate that SIRT6 is a nuclear, chromatin-associated protein that promotes resistance to DNA damage and suppresses genomic instability in mouse cells, in association with a role in base excision repair (BER). SIRT6-deficient mice are small and at 2-3 weeks of age develop abnormalities that include profound lymphopenia, loss of subcutaneous fat, lordokyphosis, and severe metabolic defects, eventually dying at about 4 weeks. We conclude that one function of SIRT6 is to promote normal DNA repair, and that SIRT6 loss leads to abnormalities in mice that overlap with aging-associated degenerative processes.
Cell 02/2006; 124(2):315-29. · 32.40 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Endogenous modulators of the central melanocortin system, such as the agouti-related protein (AgRP), should hold a pivotal position in the regulation of energy intake and expenditure. Despite this, AgRP-deficient mice were recently reported to exhibit normal food intake, body weight gain, and energy expenditure. Here we demonstrate that 2- to 3-month-old Agrp null mice do in fact exhibit subtle changes in response to feeding challenges (fasting and MCR agonists) but, of more significance and magnitude, exhibit reduced body weight and adiposity after 6 months of age. This age-dependent lean phenotype is correlated with increased metabolic rate, body temperature, and locomotor activity and increased circulating thyroid hormone (T4 and T3) and BAT UCP-1 expression. These results provide further proof of the importance of the AgRP neuronal system in the regulation of energy homeostasis.
Cell Metabolism 01/2006; 2(6):421-7. · 13.67 Impact Factor
