1
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Abushalbaq O, Baek J, Yaron A, Tran TS. Balancing act of small GTPases downstream of plexin-A4 signaling motifs promotes dendrite elaboration in mammalian cortical neurons. Sci Signal 2024; 17:eadh7673. [PMID: 38227686 DOI: 10.1126/scisignal.adh7673] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2023] [Accepted: 12/21/2023] [Indexed: 01/18/2024]
Abstract
The precise development of neuronal morphologies is crucial to the establishment of synaptic circuits and, ultimately, proper brain function. Signaling by the axon guidance cue semaphorin 3A (Sema3A) and its receptor complex of neuropilin-1 and plexin-A4 has multifunctional outcomes in neuronal morphogenesis. Downstream activation of the RhoGEF FARP2 through interaction with the lysine-arginine-lysine motif of plexin-A4 and consequent activation of the small GTPase Rac1 promotes dendrite arborization, but this pathway is dispensable for axon repulsion. Here, we investigated the interplay of small GTPase signaling mechanisms underlying Sema3A-mediated dendritic elaboration in mouse layer V cortical neurons in vitro and in vivo. Sema3A promoted the binding of the small GTPase Rnd1 to the amino acid motif lysine-valine-serine (LVS) in the cytoplasmic domain of plexin-A4. Rnd1 inhibited the activity of the small GTPase RhoA and the kinase ROCK, thus supporting the activity of the GTPase Rac1, which permitted the growth and branching of dendrites. Overexpression of a dominant-negative RhoA, a constitutively active Rac1, or the pharmacological inhibition of ROCK activity rescued defects in dendritic elaboration in neurons expressing a plexin-A4 mutant lacking the LVS motif. Our findings provide insights into the previously unappreciated balancing act between Rho and Rac signaling downstream of specific motifs in plexin-A4 to mediate Sema3A-dependent dendritic elaboration in mammalian cortical neuron development.
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Affiliation(s)
- Oday Abushalbaq
- Department of Biological Sciences, Rutgers University, Newark, NJ 07102, USA
| | - Jiyeon Baek
- Department of Biological Sciences, Rutgers University, Newark, NJ 07102, USA
| | - Avraham Yaron
- Department of Biomolecular Sciences and Department of Molecular Neuroscience, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Tracy S Tran
- Department of Biological Sciences, Rutgers University, Newark, NJ 07102, USA
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2
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Bonsor DA, Simanshu DK. Structural insights into the role of SHOC2-MRAS-PP1C complex in RAF activation. FEBS J 2023; 290:4852-4863. [PMID: 37074066 PMCID: PMC10584989 DOI: 10.1111/febs.16800] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2023] [Revised: 04/07/2023] [Accepted: 04/18/2023] [Indexed: 04/20/2023]
Abstract
RAF activation is a key step for signalling through the mitogen-activated protein kinase (MAPK) pathway. The SHOC2 protein, along with MRAS and PP1C, forms a high affinity, heterotrimeric holoenzyme that activates RAF kinases by dephosphorylating a specific phosphoserine. Recently, our research, along with that of three other teams, has uncovered valuable structural and functional insights into the SHOC2-MRAS-PP1C (SMP) holoenzyme complex. In this structural snapshot, we review SMP complex assembly, the dependency on the bound-nucleotide state of MRAS, the substitution of MRAS by the canonical RAS proteins and the roles of SHOC2 and MRAS on PP1C activity and specificity. Furthermore, we discuss the effect of several RASopathy mutations identified within the SMP complex and explore potential therapeutic approaches for targeting the SMP complex in RAS/RAF-driven cancers and RASopathies.
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Affiliation(s)
- Daniel A. Bonsor
- NCI RAS Initiative, Cancer Research Technology Program, Frederick National Laboratory for Cancer Research, Frederick, MD, USA
| | - Dhirendra K. Simanshu
- NCI RAS Initiative, Cancer Research Technology Program, Frederick National Laboratory for Cancer Research, Frederick, MD, USA
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3
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Bonsor DA, Alexander P, Snead K, Hartig N, Drew M, Messing S, Finci LI, Nissley DV, McCormick F, Esposito D, Rodriguez-Viciana P, Stephen AG, Simanshu DK. Structure of the SHOC2-MRAS-PP1C complex provides insights into RAF activation and Noonan syndrome. Nat Struct Mol Biol 2022; 29:966-977. [PMID: 36175670 PMCID: PMC10365013 DOI: 10.1038/s41594-022-00841-4] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2022] [Accepted: 08/12/2022] [Indexed: 11/08/2022]
Abstract
SHOC2 acts as a strong synthetic lethal interactor with MEK inhibitors in multiple KRAS cancer cell lines. SHOC2 forms a heterotrimeric complex with MRAS and PP1C that is essential for regulating RAF and MAPK-pathway activation by dephosphorylating a specific phosphoserine on RAF kinases. Here we present the high-resolution crystal structure of the SHOC2-MRAS-PP1C (SMP) complex and apo-SHOC2. Our structures reveal that SHOC2, MRAS, and PP1C form a stable ternary complex in which all three proteins synergistically interact with each other. Our results show that dephosphorylation of RAF substrates by PP1C is enhanced upon interacting with SHOC2 and MRAS. The SMP complex forms only when MRAS is in an active state and is dependent on SHOC2 functioning as a scaffolding protein in the complex by bringing PP1C and MRAS together. Our results provide structural insights into the role of the SMP complex in RAF activation and how mutations found in Noonan syndrome enhance complex formation, and reveal new avenues for therapeutic interventions.
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Affiliation(s)
- Daniel A Bonsor
- NCI RAS Initiative, Cancer Research Technology Program, Frederick National Laboratory for Cancer Research, Frederick, MD, USA
| | - Patrick Alexander
- NCI RAS Initiative, Cancer Research Technology Program, Frederick National Laboratory for Cancer Research, Frederick, MD, USA
| | - Kelly Snead
- NCI RAS Initiative, Cancer Research Technology Program, Frederick National Laboratory for Cancer Research, Frederick, MD, USA
| | - Nicole Hartig
- UCL Cancer Institute, University College London, London, UK
| | - Matthew Drew
- NCI RAS Initiative, Cancer Research Technology Program, Frederick National Laboratory for Cancer Research, Frederick, MD, USA
| | - Simon Messing
- NCI RAS Initiative, Cancer Research Technology Program, Frederick National Laboratory for Cancer Research, Frederick, MD, USA
| | - Lorenzo I Finci
- NCI RAS Initiative, Cancer Research Technology Program, Frederick National Laboratory for Cancer Research, Frederick, MD, USA
| | - Dwight V Nissley
- NCI RAS Initiative, Cancer Research Technology Program, Frederick National Laboratory for Cancer Research, Frederick, MD, USA
| | - Frank McCormick
- NCI RAS Initiative, Cancer Research Technology Program, Frederick National Laboratory for Cancer Research, Frederick, MD, USA
- University of California, San Francisco Helen Diller Family Comprehensive Cancer Center, University of California, San Francisco, CA, USA
| | - Dominic Esposito
- NCI RAS Initiative, Cancer Research Technology Program, Frederick National Laboratory for Cancer Research, Frederick, MD, USA
| | | | - Andrew G Stephen
- NCI RAS Initiative, Cancer Research Technology Program, Frederick National Laboratory for Cancer Research, Frederick, MD, USA
| | - Dhirendra K Simanshu
- NCI RAS Initiative, Cancer Research Technology Program, Frederick National Laboratory for Cancer Research, Frederick, MD, USA.
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4
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Liau NPD, Johnson MC, Izadi S, Gerosa L, Hammel M, Bruning JM, Wendorff TJ, Phung W, Hymowitz SG, Sudhamsu J. Structural basis for SHOC2 modulation of RAS signalling. Nature 2022; 609:400-407. [PMID: 35768504 PMCID: PMC9452301 DOI: 10.1038/s41586-022-04838-3] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2021] [Accepted: 05/05/2022] [Indexed: 12/12/2022]
Abstract
The RAS-RAF pathway is one of the most commonly dysregulated in human cancers1-3. Despite decades of study, understanding of the molecular mechanisms underlying dimerization and activation4 of the kinase RAF remains limited. Recent structures of inactive RAF monomer5 and active RAF dimer5-8 bound to 14-3-39,10 have revealed the mechanisms by which 14-3-3 stabilizes both RAF conformations via specific phosphoserine residues. Prior to RAF dimerization, the protein phosphatase 1 catalytic subunit (PP1C) must dephosphorylate the N-terminal phosphoserine (NTpS) of RAF11 to relieve inhibition by 14-3-3, although PP1C in isolation lacks intrinsic substrate selectivity. SHOC2 is as an essential scaffolding protein that engages both PP1C and RAS to dephosphorylate RAF NTpS11-13, but the structure of SHOC2 and the architecture of the presumptive SHOC2-PP1C-RAS complex remain unknown. Here we present a cryo-electron microscopy structure of the SHOC2-PP1C-MRAS complex to an overall resolution of 3 Å, revealing a tripartite molecular architecture in which a crescent-shaped SHOC2 acts as a cradle and brings together PP1C and MRAS. Our work demonstrates the GTP dependence of multiple RAS isoforms for complex formation, delineates the RAS-isoform preference for complex assembly, and uncovers how the SHOC2 scaffold and RAS collectively drive specificity of PP1C for RAF NTpS. Our data indicate that disease-relevant mutations affect complex assembly, reveal the simultaneous requirement of two RAS molecules for RAF activation, and establish rational avenues for discovery of new classes of inhibitors to target this pathway.
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Affiliation(s)
- Nicholas P D Liau
- Department of Structural Biology, Genentech, South San Francisco, CA, USA
| | - Matthew C Johnson
- Department of Structural Biology, Genentech, South San Francisco, CA, USA
| | - Saeed Izadi
- Pharmaceutical Development, Genentech, South San Francisco, CA, USA
| | - Luca Gerosa
- Department of Bioinformatics and Computational Biology, Genentech, South San Francisco, CA, USA
| | - Michal Hammel
- Physical Bioscience Division, Lawrence Berkeley National Labs, Berkeley, CA, USA
| | - John M Bruning
- Department of Biochemical and Cellular Pharmacology, Genentech, South San Francisco, CA, USA
| | - Timothy J Wendorff
- Department of Structural Biology, Genentech, South San Francisco, CA, USA
| | - Wilson Phung
- Department of Microchemistry, Proteomics and Lipidomics, Genentech, South San Francisco, CA, USA
| | - Sarah G Hymowitz
- Department of Structural Biology, Genentech, South San Francisco, CA, USA.
- The Column Group, San Francisco, CA, USA.
| | - Jawahar Sudhamsu
- Department of Structural Biology, Genentech, South San Francisco, CA, USA.
- Department of Discovery Oncology, Genentech, South San Francisco, CA, USA.
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5
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Hauseman ZJ, Fodor M, Dhembi A, Viscomi J, Egli D, Bleu M, Katz S, Park E, Jang DM, Porter KA, Meili F, Guo H, Kerr G, Mollé S, Velez-Vega C, Beyer KS, Galli GG, Maira SM, Stams T, Clark K, Eck MJ, Tordella L, Thoma CR, King DA. Structure of the MRAS-SHOC2-PP1C phosphatase complex. Nature 2022; 609:416-423. [PMID: 35830882 PMCID: PMC9452295 DOI: 10.1038/s41586-022-05086-1] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2022] [Accepted: 07/07/2022] [Indexed: 11/09/2022]
Abstract
RAS-MAPK signalling is fundamental for cell proliferation and is altered in most human cancers1-3. However, our mechanistic understanding of how RAS signals through RAF is still incomplete. Although studies revealed snapshots for autoinhibited and active RAF-MEK1-14-3-3 complexes4, the intermediate steps that lead to RAF activation remain unclear. The MRAS-SHOC2-PP1C holophosphatase dephosphorylates RAF at serine 259, resulting in the partial displacement of 14-3-3 and RAF-RAS association3,5,6. MRAS, SHOC2 and PP1C are mutated in rasopathies-developmental syndromes caused by aberrant MAPK pathway activation6-14-and SHOC2 itself has emerged as potential target in receptor tyrosine kinase (RTK)-RAS-driven tumours15-18. Despite its importance, structural understanding of the SHOC2 holophosphatase is lacking. Here we determine, using X-ray crystallography, the structure of the MRAS-SHOC2-PP1C complex. SHOC2 bridges PP1C and MRAS through its concave surface and enables reciprocal interactions between all three subunits. Biophysical characterization indicates a cooperative assembly driven by the MRAS GTP-bound active state, an observation that is extendible to other RAS isoforms. Our findings support the concept of a RAS-driven and multi-molecular model for RAF activation in which individual RAS-GTP molecules recruit RAF-14-3-3 and SHOC2-PP1C to produce downstream pathway activation. Importantly, we find that rasopathy and cancer mutations reside at protein-protein interfaces within the holophosphatase, resulting in enhanced affinities and function. Collectively, our findings shed light on a fundamental mechanism of RAS biology and on mechanisms of clinically observed enhanced RAS-MAPK signalling, therefore providing the structural basis for therapeutic interventions.
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Affiliation(s)
| | - Michelle Fodor
- Novartis Institutes for BioMedical Research, Cambridge, MA, USA
| | - Anxhela Dhembi
- Novartis Institutes for BioMedical Research, Cambridge, MA, USA
| | - Jessica Viscomi
- Novartis Institutes for BioMedical Research, Cambridge, MA, USA
| | - David Egli
- Novartis Institutes for BioMedical Research, Basel, Switzerland
| | - Melusine Bleu
- Novartis Institutes for BioMedical Research, Basel, Switzerland
| | - Stephanie Katz
- Novartis Institutes for BioMedical Research, Basel, Switzerland
| | - Eunyoung Park
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA, USA
- Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, MA, USA
| | - Dong Man Jang
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA, USA
- Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, MA, USA
| | | | - Fabian Meili
- Novartis Institutes for BioMedical Research, Cambridge, MA, USA
| | - Hongqiu Guo
- Novartis Institutes for BioMedical Research, Cambridge, MA, USA
| | - Grainne Kerr
- Novartis Institutes for BioMedical Research, Basel, Switzerland
| | - Sandra Mollé
- Novartis Institutes for BioMedical Research, Basel, Switzerland
| | | | - Kim S Beyer
- Novartis Institutes for BioMedical Research, Basel, Switzerland
| | - Giorgio G Galli
- Novartis Institutes for BioMedical Research, Basel, Switzerland
| | | | - Travis Stams
- Novartis Institutes for BioMedical Research, Cambridge, MA, USA
| | - Kirk Clark
- Novartis Institutes for BioMedical Research, Cambridge, MA, USA
| | - Michael J Eck
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA, USA
- Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, MA, USA
| | - Luca Tordella
- Novartis Institutes for BioMedical Research, Basel, Switzerland.
| | - Claudio R Thoma
- Novartis Institutes for BioMedical Research, Cambridge, MA, USA.
| | - Daniel A King
- Novartis Institutes for BioMedical Research, Cambridge, MA, USA.
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6
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Abstract
The RASopathies are a group of disorders caused by a germline mutation in one of the genes encoding a component of the RAS/MAPK pathway. These disorders, including neurofibromatosis type 1, Noonan syndrome, cardiofaciocutaneous syndrome, Costello syndrome and Legius syndrome, among others, have overlapping clinical features due to RAS/MAPK dysfunction. Although several of the RASopathies are very rare, collectively, these disorders are relatively common. In this Review, we discuss the pathogenesis of the RASopathy-associated genetic variants and the knowledge gained about RAS/MAPK signaling that resulted from studying RASopathies. We also describe the cell and animal models of the RASopathies and explore emerging RASopathy genes. Preclinical and clinical experiences with targeted agents as therapeutics for RASopathies are also discussed. Finally, we review how the recently developed drugs targeting RAS/MAPK-driven malignancies, such as inhibitors of RAS activation, direct RAS inhibitors and RAS/MAPK pathway inhibitors, might be leveraged for patients with RASopathies.
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Affiliation(s)
- Katie E Hebron
- Pediatric Oncology Branch, Center for Cancer Research, National Cancer Institute, Bethesda, MD 20892, USA
| | - Edjay Ralph Hernandez
- Pediatric Oncology Branch, Center for Cancer Research, National Cancer Institute, Bethesda, MD 20892, USA
| | - Marielle E Yohe
- Pediatric Oncology Branch, Center for Cancer Research, National Cancer Institute, Bethesda, MD 20892, USA
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7
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Endo T. M-Ras is Muscle-Ras, Moderate-Ras, Mineral-Ras, Migration-Ras, and Many More-Ras. Exp Cell Res 2020; 397:112342. [PMID: 33130177 DOI: 10.1016/j.yexcr.2020.112342] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2020] [Accepted: 10/23/2020] [Indexed: 11/19/2022]
Abstract
The Ras family of small GTPases comprises about 36 members in humans. M-Ras is related to classical Ras with regard to its regulators and effectors, but solely constitutes a subfamily among the Ras family members. Although classical Ras strongly binds Raf and highly activates the ERK pathway, M-Ras less strongly binds Raf and moderately but sustainedly activates the ERK pathway to induce neuronal differentiation. M-Ras also possesses specific effectors, including RapGEFs and the PP1 complex Shoc2-PP1c, which dephosphorylates Raf to activate the ERK pathway. M-Ras is highly expressed in the brain and plays essential roles in dendrite formation during neurogenesis, in contrast to the axon formation by R-Ras. M-Ras is also highly expressed in the bone and induces osteoblastic differentiation and transdifferentiation accompanied by calcification. Moreover, M-Ras elicits epithelial-mesenchymal transition-mediated collective and single cell migration through the PP1 complex-mediated ERK pathway activation. Activating missense mutations in the MRAS gene have been detected in Noonan syndrome, one of the RASopathies, and MRAS gene amplification occurs in several cancers. Furthermore, several SNPs in the MRAS gene are associated with coronary artery disease, obesity, and dyslipidemia. Therefore, M-Ras carries out a variety of cellular, physiological, and pathological functions. Further investigations may reveal more functions of M-Ras.
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Affiliation(s)
- Takeshi Endo
- Department of Biology, Graduate School of Science, Chiba University, 1-33 Yayoicho, Inageku, Chiba, Chiba 263-8522, Japan.
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8
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Young LC, Rodriguez-Viciana P. MRAS: A Close but Understudied Member of the RAS Family. Cold Spring Harb Perspect Med 2018; 8:cshperspect.a033621. [PMID: 29311130 DOI: 10.1101/cshperspect.a033621] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
MRAS is the closest relative to the classical RAS oncoproteins and shares most regulatory and effector interactions. However, it also has unique functions, including its ability to function as a phosphatase regulatory subunit when in complex with SHOC2 and protein phosphatase 1 (PP1). This phosphatase complex regulates a crucial step in the activation cycle of RAF kinases and provides a key coordinate input required for efficient ERK pathway activation and transformation by RAS. MRAS mutations rarely occur in cancer but deregulated expression may play a role in tumorigenesis in some settings. Activating mutations in MRAS (as well as SHOC2 and PP1) do occur in the RASopathy Noonan syndrome, underscoring a key role for MRAS within the RAS-ERK pathway. MRAS also has unique roles in cell migration and differentiation and has properties consistent with a key role in the regulation of cell polarity. Further investigations should shed light on what remains a relatively understudied RAS family member.
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Affiliation(s)
- Lucy C Young
- UCSF Helen Diller Family Comprehensive Cancer Center, San Francisco, California 94158
| | - Pablo Rodriguez-Viciana
- UCL Cancer Institute, Paul O'Gorman Building, University College London, London WC1E 6BT, United Kingdom
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9
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Ehrhardt A, Wang B, Leung MJ, Schrader JW. Absence of M-Ras modulates social behavior in mice. BMC Neurosci 2015; 16:68. [PMID: 26490652 PMCID: PMC4618870 DOI: 10.1186/s12868-015-0209-8] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2015] [Accepted: 10/08/2015] [Indexed: 12/23/2022] Open
Abstract
Background The molecular mechanisms that determine social behavior are poorly understood. Pheromones play a critical role in social recognition in most animals, including mice, but how these are converted into behavioral responses is largely unknown. Here, we report that the absence of the small GTPase M-Ras affects social behavior in mice. Results In their interactions with other males, Mras−/− males exhibited high levels of territorial aggression and social investigations, and increased fear-related behavior. They also showed increased mating behavior with females. Curiously, increased aggression and mating behaviors were only observed when Mras−/− males were paired with Mras−/− partners, but were significantly reduced when paired with wild-type (WT) mice. Since mice use pheromonal cues to identify other individuals, we explored the possibility that pheromone detection may be altered in Mras−/− mice. Unlike WT mice, Mras−/− did not show a preference for exploring unfamiliar urinary pheromones or unfamiliar isogenic mice. Although this could indicate that vomeronasal function and/or olfactory learning may be compromised in Mras−/− mice, these observations were not fully consistent with the differential behavioral responses to WT and Mras−/− interaction partners by Mras−/− males. In addition, induction of c-fos upon pheromone exposure or in response to mating was similar in WT and Mras−/− mice, as was the ex vivo expansion of neural progenitors with EGF. This indicated that acute pheromone detection and processing was likely intact. However, urinary metabolite profiles differed between Mras−/− and WT males. Conclusions The changes in behaviors displayed by Mras−/− mice are likely due to a complex combination of factors that may include an inherent predisposition to increased aggression and sexual behavior, and the production of distinct pheromones that could override the preference for unfamiliar social odors. Olfactory and/or social learning processes may thus be compromised in Mras−/− mice. Electronic supplementary material The online version of this article (doi:10.1186/s12868-015-0209-8) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Annette Ehrhardt
- The Biomedical Research Centre, University of British Columbia, 2222 Health Sciences Mall, Vancouver, V6T 1Z3, Canada.
| | - Bin Wang
- The Biomedical Research Centre, University of British Columbia, 2222 Health Sciences Mall, Vancouver, V6T 1Z3, Canada.
| | - Marie J Leung
- The Biomedical Research Centre, University of British Columbia, 2222 Health Sciences Mall, Vancouver, V6T 1Z3, Canada.
| | - John W Schrader
- The Biomedical Research Centre, University of British Columbia, 2222 Health Sciences Mall, Vancouver, V6T 1Z3, Canada.
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10
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Abstract
Mammalian plexins constitute a family of transmembrane receptors for semaphorins and represent critical regulators of various processes during development of the nervous, cardiovascular, skeletal, and renal system. In vitro studies have shown that plexins exert their effects via an intracellular R-Ras/M-Ras GTPase-activating protein (GAP) domain or by activation of RhoA through interaction with Rho guanine nucleotide exchange factor proteins. However, which of these signaling pathways are relevant for plexin functions in vivo is largely unknown. Using an allelic series of transgenic mice, we show that the GAP domain of plexins constitutes their key signaling module during development. Mice in which endogenous Plexin-B2 or Plexin-D1 is replaced by transgenic versions harboring mutations in the GAP domain recapitulate the phenotypes of the respective null mutants in the developing nervous, vascular, and skeletal system. We further provide genetic evidence that, unexpectedly, the GAP domain-mediated developmental functions of plexins are not brought about via R-Ras and M-Ras inactivation. In contrast to the GAP domain mutants, Plexin-B2 transgenic mice defective in Rho guanine nucleotide exchange factor binding are viable and fertile but exhibit abnormal development of the liver vasculature. Our genetic analyses uncover the in vivo context-dependence and functional specificity of individual plexin-mediated signaling pathways during development.
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11
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Mathieu ME, Faucheux C, Saucourt C, Soulet F, Gauthereau X, Fédou S, Trouillas M, Thézé N, Thiébaud P, Boeuf H. MRAS GTPase is a novel stemness marker that impacts mouse embryonic stem cell plasticity and Xenopus embryonic cell fate. Development 2013; 140:3311-22. [DOI: 10.1242/dev.091082] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Pluripotent mouse embryonic stem cells (mESCs), maintained in the presence of the leukemia inhibitory factor (LIF) cytokine, provide a powerful model with which to study pluripotency and differentiation programs. Extensive microarray studies on cultured cells have led to the identification of three LIF signatures. Here we focus on muscle ras oncogene homolog (MRAS), which is a small GTPase of the Ras family encoded within the Pluri gene cluster. To characterise the effects of Mras on cell pluripotency and differentiation, we used gain- and loss-of-function strategies in mESCs and in the Xenopus laevis embryo, in which Mras gene structure and protein sequence are conserved. We show that persistent knockdown of Mras in mESCs reduces expression of specific master genes and that MRAS plays a crucial role in the downregulation of OCT4 and NANOG protein levels upon differentiation. In Xenopus, we demonstrate the potential of Mras to modulate cell fate at early steps of development and during neurogenesis. Overexpression of Mras allows gastrula cells to retain responsiveness to fibroblast growth factor (FGF) and activin. Collectively, these results highlight novel conserved and pleiotropic effects of MRAS in stem cells and early steps of development.
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Affiliation(s)
- Marie-Emmanuelle Mathieu
- University of Bordeaux, CIRID, UMR 5164, F-33000 Bordeaux, France
- CNRS, CIRID, UMR 5164, F-33000 Bordeaux, France
| | - Corinne Faucheux
- University of Bordeaux, CIRID, UMR 5164, F-33000 Bordeaux, France
- CNRS, CIRID, UMR 5164, F-33000 Bordeaux, France
| | - Claire Saucourt
- University of Bordeaux, CIRID, UMR 5164, F-33000 Bordeaux, France
- CNRS, CIRID, UMR 5164, F-33000 Bordeaux, France
| | - Fabienne Soulet
- University of Bordeaux, CIRID, UMR 5164, F-33000 Bordeaux, France
- CNRS, CIRID, UMR 5164, F-33000 Bordeaux, France
| | - Xavier Gauthereau
- University of Bordeaux, CIRID, UMR 5164, F-33000 Bordeaux, France
- CNRS, CIRID, UMR 5164, F-33000 Bordeaux, France
| | - Sandrine Fédou
- University of Bordeaux, CIRID, UMR 5164, F-33000 Bordeaux, France
- CNRS, CIRID, UMR 5164, F-33000 Bordeaux, France
| | - Marina Trouillas
- University of Bordeaux, CIRID, UMR 5164, F-33000 Bordeaux, France
| | - Nadine Thézé
- University of Bordeaux, CIRID, UMR 5164, F-33000 Bordeaux, France
- CNRS, CIRID, UMR 5164, F-33000 Bordeaux, France
| | - Pierre Thiébaud
- University of Bordeaux, CIRID, UMR 5164, F-33000 Bordeaux, France
- CNRS, CIRID, UMR 5164, F-33000 Bordeaux, France
| | - Hélène Boeuf
- University of Bordeaux, CIRID, UMR 5164, F-33000 Bordeaux, France
- CNRS, CIRID, UMR 5164, F-33000 Bordeaux, France
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12
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Kennedy CR, Tilkens SB, Guan H, Garner JA, Or PM, Chan AM. Differential sensitivities of glioblastoma cell lines towards metabolic and signaling pathway inhibitions. Cancer Lett 2013; 336:299-306. [DOI: 10.1016/j.canlet.2013.03.020] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2012] [Revised: 02/22/2013] [Accepted: 03/15/2013] [Indexed: 01/21/2023]
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13
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Larive RM, Abad A, Cardaba CM, Hernández T, Cañamero M, de Álava E, Santos E, Alarcón B, Bustelo XR. The Ras-like protein R-Ras2/TC21 is important for proper mammary gland development. Mol Biol Cell 2012; 23:2373-87. [PMID: 22535521 PMCID: PMC3374755 DOI: 10.1091/mbc.e12-01-0060] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
R-Ras2/TC21 is a GTPase with high sequence and signaling similarity with Ras subfamily members. Although it has been extensively studied using overexpression studies in cell lines, its physiological role remains poorly characterized. Here we used RRas2-knockout mice expressing β-galactosidase under the regulation of the endogenous RRas2 promoter to investigate the function of this GTPase in vivo. Despite its expression in tissues critical for organismal viability, RRas2(-/-) mice show no major alterations in viability, growth rates, cardiovascular parameters, or fertility. By contrast, they display a marked and specific defect in the development of the mammary gland during puberty. In the absence of R-Ras2/TC21, this gland forms reduced numbers of terminal end buds (TEBs) and ductal branches, leading to a temporal delay in the extension and arborization of the gland tree in mammary fat pads. This phenotype is linked to cell-autonomous proliferative defects of epithelial cells present in TEBs. These cells also show reduced Erk activation but wild type-like levels of phosphorylated Akt. Using compound RRas2-, HRas-, and NRas-knockout mice, we demonstrate that these GTPases act in a nonsynergistic and nonadditive manner during this morphogenic process.
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Affiliation(s)
- Romain M Larive
- Centro de Investigación del Cáncer, Consejo Superior de Investigaciones Científicas-University of Salamanca, E37007 Salamanca, Spain
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Abstract
R-Ras is a member of the RAS superfamily of small GTP-binding proteins. The physiologic function of R-Ras has not been fully elucidated. We found that R-Ras is expressed by lymphoid and nonlymphoid tissues and drastically up-regulated when bone marrow progenitors are induced to differentiate into dendritic cells (DCs). To address the role of R-Ras in DC functions, we generated a R-Ras-deficient mouse strain. We found that tumors induced in Rras(-/-) mice formed with shorter latency and attained greater tumor volumes. This finding has prompted the investigation of a role for R-Ras in the immune system. Indeed, Rras(-/-) mice were impaired in their ability to prime allogeneic and antigen-specific T-cell responses. Rras(-/-) DCs expressed lower levels of surface MHC class II and CD86 in response to lipopolysaccharide compared with wild-type DCs. This was correlated with a reduced phosphorylation of p38 and Akt. Consistently, R-Ras-GTP level was increased within 10 minutes of lipopolysaccharide stimulation. Furthermore, Rras(-/-) DCs have attenuated capacity to spread on fibronectin and form stable immunologic synapses with T cells. Altogether, these findings provide the first demonstration of a role for R-Ras in cell-mediated immunity and further expand on the complexity of small G-protein signaling in DCs.
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15
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Sivapalaratnam S, Motazacker MM, Maiwald S, Hovingh GK, Kastelein JJP, Levi M, Trip MD, Dallinga-Thie GM. Genome-wide association studies in atherosclerosis. Curr Atheroscler Rep 2011; 13:225-32. [PMID: 21369780 PMCID: PMC3085784 DOI: 10.1007/s11883-011-0173-4] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Cardiovascular disease remains the major cause of worldwide morbidity and mortality. Its pathophysiology is complex and multifactorial. Because the phenotype of cardiovascular disease often shows a marked heritable pattern, it is likely that genetic factors play an important role. In recent years, large genome-wide association studies have been conducted to decipher the molecular mechanisms underlying this heritable and prevalent phenotype. The emphasis of this review is on the recently identified 17 susceptibility loci for coronary artery disease. Implications of their discovery for biology and clinical medicine are discussed. A description of the landscape of human genetics in the near future in the context of next-generation sequence technologies is provided at the conclusion of this review.
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Affiliation(s)
- S Sivapalaratnam
- Department of Vascular Medicine, Academic Medical Center Amsterdam, Amsterdam, The Netherlands
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16
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Yamamoto Y, Tanahashi T, Kawai T, Chikahisa S, Katsuura S, Nishida K, Teshima-Kondo S, Sei H, Rokutan K. Changes in behavior and gene expression induced by caloric restriction in C57BL/6 mice. Physiol Genomics 2009; 39:227-35. [DOI: 10.1152/physiolgenomics.00082.2009] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
Caloric restriction (CR) is an effective method for prevention of age-associated diseases as well as overweight and obesity; however, there is controversy regarding the effects of dieting regimens on behavior. In this study, we investigated two different dieting regimens: repeated fasting and refeeding (RFR) and daily feeding of half the amount of food consumed by RFR mice (CR). CR and RFR mice had an approximate 20% reduction in food intake compared with control mice. Open field, light-dark transition, elevated plus maze, and forced swimming tests indicated that CR, but not RFR, reduced anxiety- and depressive-like behaviors, with a reduction peak on day 8. Using a mouse whole genome microarray, we analyzed gene expression in the prefrontal cortex, amygdala, and hypothalamus. In addition to the CR-responsive genes commonly modified by RFR and CR, each regimen differentially changed the expression of distinct genes in each region. The most profound change was observed in the amygdalas of CR mice: 884 genes were specifically upregulated. Ingenuity pathway analysis revealed that these 884 genes significantly modified nine canonical pathways in the amygdala. α-Adrenergic and dopamine receptor signalings were the two top-scoring pathways. Quantitative RT-PCR confirmed the upregulation of six genes in these pathways. Western blotting confirmed that CR specifically increased dopamine- and cAMP-regulated phosphoprotein (Darpp-32), a key regulator of dopamine receptor signaling, in the amygdala. Our results suggest that CR may change behavior through altered gene expression.
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Affiliation(s)
| | | | | | - Sachiko Chikahisa
- Integrative Physiology, Institute of Health Biosciences, The University of Tokushima Graduate School, Tokushima, Japan
| | | | | | | | - Hiroyoshi Sei
- Integrative Physiology, Institute of Health Biosciences, The University of Tokushima Graduate School, Tokushima, Japan
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17
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Watanabe-Takano H, Takano K, Keduka E, Endo T. M-Ras is activated by bone morphogenetic protein-2 and participates in osteoblastic determination, differentiation, and transdifferentiation. Exp Cell Res 2009; 316:477-90. [PMID: 19800879 DOI: 10.1016/j.yexcr.2009.09.028] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2009] [Revised: 09/26/2009] [Accepted: 09/28/2009] [Indexed: 11/19/2022]
Abstract
The small GTPase M-Ras is highly expressed in the central nervous system and plays essential roles in neuronal differentiation. However, its other cellular and physiological functions remain to be elucidated. Here, we clarify the novel functions of M-Ras in osteogenesis. M-Ras was prominently expressed in developing mouse bones particularly in osteoblasts and hypertrophic chondrocytes. Its expression was elevated in C3H/10T1/2 (10T1/2) mesenchymal cells and in MC3T3-E1 preosteoblasts during differentiation into osteoblasts. Treatment of C2C12 skeletal muscle myoblasts with bone morphogenetic protein-2 (BMP-2) to bring about transdifferentiation into osteoblasts also induced M-Ras mRNA and protein expression. Moreover, the BMP-2 treatment activated the M-Ras protein. Stable expression of the constitutively active M-Ras(G22V) in 10T1/2 cells facilitated osteoblast differentiation. M-Ras(G22V) also induced transdifferentiation of C2C12 cells into osteoblasts. In contrast, knockdown of endogenous M-Ras by RNAi interfered with osteoblast differentiation in 10T1/2 and MC3T3-E1 cells. Osteoblast differentiation in M-Ras(G22V)-expressing C2C12 cells was inhibited by treatment with inhibitors of p38 MAP kinase (MAPK) and c-Jun N-terminal kinase (JNK) but not by inhibitors of MAPK and ERK kinase (MEK) or phosphatidylinositol 3-kinase. These results imply that M-Ras, induced and activated by BMP-2 signaling, participates in the osteoblastic determination, differentiation, and transdifferentiation under p38 MAPK and JNK regulation.
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Affiliation(s)
- Haruko Watanabe-Takano
- Department of Biology, Graduate School of Science, Chiba University, Inageku, Chiba 263-8522, Japan
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18
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Plexin-B1 is a GTPase activating protein for M-Ras, remodelling dendrite morphology. EMBO Rep 2009; 10:614-21. [PMID: 19444311 DOI: 10.1038/embor.2009.63] [Citation(s) in RCA: 71] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2008] [Revised: 03/04/2009] [Accepted: 03/09/2009] [Indexed: 11/08/2022] Open
Abstract
Plexins are receptors for axonal guidance molecules known as semaphorins. We recently reported that the semaphorin 4D (Sema4D) receptor, Plexin-B1, induces axonal growth cone collapse by functioning as an R-Ras GTPase activating protein (GAP). Here, we report that Plexin-B1 shows GAP activity for M-Ras, another member of the Ras family of GTPases. In cortical neurons, the expression of M-Ras was upregulated during dendritic development. Knockdown of endogenous M-Ras-but not R-Ras-reduced dendritic outgrowth and branching, whereas overexpression of constitutively active M-Ras, M-Ras(Q71L), enhanced dendritic outgrowth and branching. Sema4D suppressed M-Ras activity and reduced dendritic outgrowth and branching, but this reduction was blocked by M-Ras(Q71L). M-Ras(Q71L) stimulated extracellular signal-regulated kinase (ERK) activation, inducing dendrite growth, whereas Sema4D suppressed ERK activity and down-regulation of ERK was required for a Sema4D-induced reduction of dendrite growth. Thus, we conclude that Plexin-B1 is a dual functional GAP for R-Ras and M-Ras, remodelling axon and dendrite morphology, respectively.
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Vazquez J, Hall SC, Witkowska HE, Greco MA. Rapid alterations in cortical protein profiles underlie spontaneous sleep and wake bouts. J Cell Biochem 2008; 105:1472-84. [DOI: 10.1002/jcb.21970] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
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20
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Yoshikawa Y, Satoh T, Tamura T, Wei P, Bilasy SE, Edamatsu H, Aiba A, Katagiri K, Kinashi T, Nakao K, Kataoka T. The M-Ras-RA-GEF-2-Rap1 pathway mediates tumor necrosis factor-alpha dependent regulation of integrin activation in splenocytes. Mol Biol Cell 2007; 18:2949-59. [PMID: 17538012 PMCID: PMC1949361 DOI: 10.1091/mbc.e07-03-0250] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
The Rap1 small GTPase has been implicated in regulation of integrin-mediated leukocyte adhesion downstream of various chemokines and cytokines in many aspects of inflammatory and immune responses. However, the mechanism for Rap1 regulation in the adhesion signaling remains unclear. RA-GEF-2 is a member of the multiple-member family of guanine nucleotide exchange factors (GEFs) for Rap1 and characterized by the possession of a Ras/Rap1-associating domain, interacting with M-Ras-GTP as an effector, in addition to the GEF catalytic domain. Here, we show that RA-GEF-2 is specifically responsible for the activation of Rap1 that mediates tumor necrosis factor-alpha (TNF-alpha)-triggered integrin activation. In BAF3 hematopoietic cells, activated M-Ras potently induced lymphocyte function-associated antigen 1 (LFA-1)-mediated cell aggregation. This activation was totally abrogated by knockdown of RA-GEF-2 or Rap1. TNF-alpha treatment activated LFA-1 in a manner dependent on M-Ras, RA-GEF-2, and Rap1 and induced activation of M-Ras and Rap1 in the plasma membrane, which was accompanied by recruitment of RA-GEF-2. Finally, we demonstrated that M-Ras and RA-GEF-2 were indeed involved in TNF-alpha-stimulated and Rap1-mediated LFA-1 activation in splenocytes by using mice deficient in RA-GEF-2. These findings proved a crucial role of the cross-talk between two Ras-family GTPases M-Ras and Rap1, mediated by RA-GEF-2, in adhesion signaling.
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Affiliation(s)
- Yoko Yoshikawa
- *Division of Molecular Biology, Department of Biochemistry and Molecular Biology, and
| | - Takaya Satoh
- *Division of Molecular Biology, Department of Biochemistry and Molecular Biology, and
| | - Takashi Tamura
- *Division of Molecular Biology, Department of Biochemistry and Molecular Biology, and
| | - Ping Wei
- *Division of Molecular Biology, Department of Biochemistry and Molecular Biology, and
| | - Shymaa E. Bilasy
- *Division of Molecular Biology, Department of Biochemistry and Molecular Biology, and
| | - Hironori Edamatsu
- *Division of Molecular Biology, Department of Biochemistry and Molecular Biology, and
| | - Atsu Aiba
- Division of Molecular Genetics, Department of Physiology and Cell Biology, Kobe University Graduate School of Medicine, Kobe 650-0017, Japan
| | - Koko Katagiri
- Department of Molecular Genetics, Institute of Biomedical Science, Kansai Medical University, Osaka 570-8506, Japan; and
| | - Tatsuo Kinashi
- Department of Molecular Genetics, Institute of Biomedical Science, Kansai Medical University, Osaka 570-8506, Japan; and
| | - Kazuki Nakao
- Laboratory of Animal Resources and Genetic Engineering, Riken Center for Developmental Biology, Kobe 650-0047, Japan
| | - Tohru Kataoka
- *Division of Molecular Biology, Department of Biochemistry and Molecular Biology, and
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