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Zheng Y, Zhang Y, Wu L, Riaz H, Li Z, Shi D, Rehman SU, Liu Q, Cui K. Generation of Heritable Prominent Double Muscle Buttock Rabbits via Novel Site Editing of Myostatin Gene Using CRISPR/Cas9 System. Front Vet Sci 2022; 9:842074. [PMID: 35669173 PMCID: PMC9165342 DOI: 10.3389/fvets.2022.842074] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2021] [Accepted: 03/18/2022] [Indexed: 12/25/2022] Open
Abstract
Rabbits have been domesticated for meat, wool, and fur production, and have also been cherished as a companion, artistic inspiration, and an experimental model to study many human diseases. In the present study, the muscle mass negative regulator gene myostatin (MSTN) was knocked out in rabbits at two novel sites in exon3, and the function of these mutations was determined in subsequent generations. The prominent double muscle phenotype with hyperplasia or hypertrophy of muscle fiber was observed in the MSTN-KO rabbits, and a similar phenotype was confirmed in the F1 generation. Moreover, the average weight of 80-day-old MSTN-KO rabbits (2,452 ± 63 g) was higher than that of wild-type rabbits (2,393.2 ± 106.88 g), and also the bodyweight of MSTN-KO rabbits (3,708 ± 43.06g) was significantly higher (P < 0.001) at the age of 180 days than wild-type (WT) rabbits (3,224 ± 48.64g). In MSTN-KO rabbits, fourteen rabbit pups from the F1 generation and thirteen from the F2 generation stably inherited the induced MSTN gene mutations. Totally, 194 pups were produced in the F1 generation of which 49 were MSTN-KO rabbits, while 47 pups were produced in the F2 generation of which 20 were edited rabbits, and the ratio of edited to wild-type rabbits in the F2 generation was approximately 1:1. Thus, we successfully generated a heritable double muscle buttocks rabbits via myostatin mutation with CRISPR/Cas9 system, which could be valuable in rabbit's meat production and also a useful animal model to study the development of muscles among livestock species and improve their important economic traits as well as the human muscle development-related diseases.
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Affiliation(s)
- Yalin Zheng
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, Guangxi University, Nanning, China
| | - Yu Zhang
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, Guangxi University, Nanning, China
| | - Liyan Wu
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, Guangxi University, Nanning, China
| | - Hasan Riaz
- Department of Biosciences, COMSATS University Islamabad, Islamabad, Pakistan
| | - Zhipeng Li
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, Guangxi University, Nanning, China
| | - Deshun Shi
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, Guangxi University, Nanning, China
| | - Saif Ur Rehman
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, Guangxi University, Nanning, China
| | - Qingyou Liu
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, Guangxi University, Nanning, China.,Guangdong Provincial Key Laboratory of Animal Molecular Design and Precise Breeding, School of Life Science and Engineering, Foshan University, Foshan, China
| | - Kuiqing Cui
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, Guangxi University, Nanning, China
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Gomer RH. The Use of Diffusion Calculations and Monte Carlo Simulations to Understand the Behavior of Cells in Dictyostelium Communities. Comput Struct Biotechnol J 2019; 17:684-688. [PMID: 31303972 PMCID: PMC6603294 DOI: 10.1016/j.csbj.2019.06.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2019] [Revised: 05/25/2019] [Accepted: 06/01/2019] [Indexed: 11/01/2022] Open
Abstract
Microbial communities are the simplest possible model of multicellular tissues, allowing studies of cell-cell interactions to be done with as few extraneous factors as possible. For instance, the eukaryotic microbe Dictyostelium discoideum proliferates as single cells, and when starved, the cells aggregate together and form structures of ~20,000 cells. The cells use a variety of signals to direct their movement, inform each other of their local cell density and whether they are starving, and organize themselves into groups of ~20,000 cells. Mathematical models and computational approaches have been a key check on, and guide of, the experimental work. In this minireview, I will discuss diffusion calculations and Monte Carlo simulations that were used for Dictyostelium studies that offer general paradigms for several aspects of cell-cell communication. For instance, computational work showed that diffusible secreted cell-density sensing (quorum) factors can diffuse away so quickly from a single cell that the local concentration will not build up to incorrectly cause the cell to sense that it is in the presence of a high density of other cells secreting that signal. In another example, computation correctly predicted a mechanism that allows a group of cells to break up into subgroups. These are thus some examples of the power and necessity of computational work in biology.
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Affiliation(s)
- Richard H Gomer
- Department of Biology, Texas A&M University, College Station, TX 77843-3474, USA
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3
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Cianflone E, Aquila I, Scalise M, Marotta P, Torella M, Nadal-Ginard B, Torella D. Molecular basis of functional myogenic specification of Bona Fide multipotent adult cardiac stem cells. Cell Cycle 2018; 17:927-946. [PMID: 29862928 PMCID: PMC6103696 DOI: 10.1080/15384101.2018.1464852] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2018] [Revised: 06/01/2018] [Accepted: 04/08/2018] [Indexed: 01/14/2023] Open
Abstract
Ischemic Heart Disease (IHD) remains the developed world's number one killer. The improved survival from Acute Myocardial Infarction (AMI) and the progressive aging of western population brought to an increased incidence of chronic Heart Failure (HF), which assumed epidemic proportions nowadays. Except for heart transplantation, all treatments for HF should be considered palliative because none of the current therapies can reverse myocardial degeneration responsible for HF syndrome. To stop the HF epidemic will ultimately require protocols to reduce the progressive cardiomyocyte (CM) loss and to foster their regeneration. It is now generally accepted that mammalian CMs renew throughout life. However, this endogenous regenerative reservoir is insufficient to repair the extensive damage produced by AMI/IHD while the source and degree of CM turnover remains strongly disputed. Independent groups have convincingly shown that the adult myocardium harbors bona-fide tissue specific cardiac stem cells (CSCs). Unfortunately, recent reports have challenged the identity and the endogenous myogenic capacity of the c-kit expressing CSCs. This has hampered progress and unless this conflict is settled, clinical tests of repair/regenerative protocols are unlikely to provide convincing answers about their clinical potential. Here we review recent data that have eventually clarified the specific phenotypic identity of true multipotent CSCs. These cells when coaxed by embryonic cardiac morphogens undergo a precisely orchestrated myogenic commitment process robustly generating bona-fide functional cardiomyocytes. These data should set the path for the revival of further investigation untangling the regenerative biology of adult CSCs to harness their potential for HF prevention and treatment.
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Affiliation(s)
- Eleonora Cianflone
- Molecular and Cellular Cardiology, Department of Medical and Surgical Sciences, Magna Graecia University, Catanzaro, Italy
| | - Iolanda Aquila
- Molecular and Cellular Cardiology, Department of Medical and Surgical Sciences, Magna Graecia University, Catanzaro, Italy
| | - Mariangela Scalise
- Molecular and Cellular Cardiology, Department of Medical and Surgical Sciences, Magna Graecia University, Catanzaro, Italy
| | - Pina Marotta
- Molecular and Cellular Cardiology, Department of Medical and Surgical Sciences, Magna Graecia University, Catanzaro, Italy
| | - Michele Torella
- Department of Cardiothoracic Sciences, University of Campania Campus “Salvatore Venuta” Viale Europa- Loc. Germaneto “L. Vanvitelli”, Naples, Italy
| | - Bernardo Nadal-Ginard
- Molecular and Cellular Cardiology, Department of Medical and Surgical Sciences, Magna Graecia University, Catanzaro, Italy
| | - Daniele Torella
- Molecular and Cellular Cardiology, Department of Medical and Surgical Sciences, Magna Graecia University, Catanzaro, Italy
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Inomata T, Mashaghi A, Hong J, Nakao T, Dana R. Scaling and maintenance of corneal thickness during aging. PLoS One 2017; 12:e0185694. [PMID: 28985226 PMCID: PMC5630165 DOI: 10.1371/journal.pone.0185694] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2016] [Accepted: 09/18/2017] [Indexed: 01/27/2023] Open
Abstract
Corneal thickness is tightly regulated by its boundary endothelial and epithelial layers. The regulated set-point of corneal thickness likely shows inter-individual variations, changes by age, and response to stress. Using anterior segment-optical coherence tomography, we measure murine central corneal thickness and report on body size scaling of murine central corneal thickness during aging. For aged-matched mice, we find that corneal thickness depends on sex and strain. To shed mechanistic insights into these anatomical changes, we measure epithelial layer integrity and endothelial cell density during the life span of the mice using corneal fluorescein staining and in vivo confocal microscopy, respectively and compare their trends with that of the corneal thickness. Cornea thickness increases initially (1 month: 114.7 ± 3.0 μm, 6 months: 126.3 ± 1.6 μm), reaches a maximum (9 months: 129.3 ± 4.4 μm) and then reduces (12 months: 127 ± 2.9 μm, 13 months: 119.5 ± 7.6 μm, 14 months: 110.6 ± 10.6 μm), while the body size (weight) increases with age. We find that endothelial cell density reduces from 2 months old to 8 months old as the mice age and epithelial layer accumulates damages within this time frame. Finally, we compare murine corneal thickness with those of several other mammals including humans and show that corneal thickness has an allometric scaling with body size. Our results have relevance for organ size regulation, translational pharmacology, and veterinary medicine.
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Affiliation(s)
- Takenori Inomata
- Schepens Eye Research Institute, Massachusetts Eye and Ear Infirmary, Department of Ophthalmology, Harvard Medical School, Boston, MA, United States of America
- Juntendo University Faculty of Medicine, Department of Ophthalmology, Tokyo, Japan
| | - Alireza Mashaghi
- Schepens Eye Research Institute, Massachusetts Eye and Ear Infirmary, Department of Ophthalmology, Harvard Medical School, Boston, MA, United States of America
- Leiden Academic Centre for Drug Research, Faculty of Mathematics and Natural Sciences, Leiden University, Leiden, The Netherlands
| | - Jiaxu Hong
- Schepens Eye Research Institute, Massachusetts Eye and Ear Infirmary, Department of Ophthalmology, Harvard Medical School, Boston, MA, United States of America
| | - Takeshi Nakao
- Schepens Eye Research Institute, Massachusetts Eye and Ear Infirmary, Department of Ophthalmology, Harvard Medical School, Boston, MA, United States of America
| | - Reza Dana
- Schepens Eye Research Institute, Massachusetts Eye and Ear Infirmary, Department of Ophthalmology, Harvard Medical School, Boston, MA, United States of America
- * E-mail:
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Pten Regulates Retinal Amacrine Cell Number by Modulating Akt, Tgfβ, and Erk Signaling. J Neurosci 2017; 36:9454-71. [PMID: 27605619 DOI: 10.1523/jneurosci.0936-16.2016] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2016] [Accepted: 07/18/2016] [Indexed: 12/11/2022] Open
Abstract
UNLABELLED All tissues are genetically programmed to acquire an optimal size that is defined by total cell number and individual cellular dimensions. The retina contains stereotyped proportions of one glial and six neuronal cell types that are generated in overlapping waves. How multipotent retinal progenitors know when to switch from making one cell type to the next so that appropriate numbers of each cell type are generated is poorly understood. Pten is a phosphatase that controls progenitor cell proliferation and differentiation in several lineages. Here, using a conditional loss-of-function strategy, we found that Pten regulates retinal cell division and is required to produce the full complement of rod photoreceptors and amacrine cells in mouse. We focused on amacrine cell number control, identifying three downstream Pten effector pathways. First, phosphoinositide 3-kinase/Akt signaling is hyperactivated in Pten conditional knock-out (cKO) retinas, and misexpression of constitutively active Akt (Akt-CA) in retinal explants phenocopies the reduction in amacrine cell production observed in Pten cKOs. Second, Akt-CA activates Tgfβ signaling in retinal explants, which is a negative feedback pathway for amacrine cell production. Accordingly, Tgfβ signaling is elevated in Pten cKO retinas, and epistatic analyses placed Pten downstream of TgfβRII in amacrine cell number control. Finally, Pten regulates Raf/Mek/Erk signaling levels to promote the differentiation of all amacrine cell subtypes, which are each reduced in number in Pten cKOs. Pten is thus a positive regulator of amacrine cell production, acting via multiple downstream pathways, highlighting its diverse actions as a mediator of cell number control. SIGNIFICANCE STATEMENT Despite the importance of size for optimal organ function, how individual cell types are generated in correct proportions is poorly understood. There are several ways to control cell number, including readouts of organ function (e.g., secreted hormones reach functional levels when enough cells are made) or counting of cell divisions or cell number. The latter applies to the retina, where cell number is regulated by negative feedback signals, which arrest differentiation of particular cell types at threshold levels. Herein, we show that Pten is a critical regulator of amacrine cell number in the retina, acting via multiple downstream pathways. Our studies provide molecular insights into how PTEN loss in humans may lead to uncontrolled cell division in several pathological conditions.
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Suess PM, Gomer RH. Extracellular Polyphosphate Inhibits Proliferation in an Autocrine Negative Feedback Loop in Dictyostelium discoideum. J Biol Chem 2016; 291:20260-9. [PMID: 27519410 DOI: 10.1074/jbc.m116.737825] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2016] [Indexed: 11/06/2022] Open
Abstract
Polyphosphate is a polymer of phosphate residues linked by high energy phosphoanhydride bonds. Despite being highly conserved throughout nature, its function is poorly understood. Here we show that Dictyostelium cells accumulate extracellular polyphosphate, and this acts to inhibit proliferation at high cell densities. In shaking culture, extracellular polyphosphate concentrations increase as cell density increases, and if the concentration of polyphosphate observed at the stationary phase is added to cells at mid-log, proliferation is halted. Adding an exopolyphosphatase to cell cultures or stationary phase conditioned medium decreases polyphosphate levels and abrogates the anti-proliferative effect. The cells show saturable binding of polyphosphate, suggesting the presence of a cell surface polyphosphate receptor. Extracellular polyphosphate accumulation is potentiated by decreased nutrient levels, potentially as a means to anticipate starvation. Loss of the Dictyostelium polyphosphate kinase DdPpk1 causes intracellular polyphosphate levels to become undetectable and negatively affects fitness, cytokinesis, and germination. However, cells lacking DdPpk1 accumulate ∼50% normal levels of extracellular polyphosphate, suggesting an additional means of synthesis. We found that cells lacking inositol hexakisphosphate kinase, which is responsible for the synthesis of the inositol pyrophosphates IP7 and IP8, reach abnormally high cell densities and show decreased extracellular polyphosphate levels. Two different enzymes thus appear to mediate the synthesis of Dictyostelium extracellular polyphosphate, which is used as a signal in an autocrine negative feedback loop to regulate cell proliferation.
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Affiliation(s)
- Patrick M Suess
- From the Department of Biology, Texas A&M University, College Station, Texas 77843-3474
| | - Richard H Gomer
- From the Department of Biology, Texas A&M University, College Station, Texas 77843-3474
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7
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Hill EM, Petersen CP. Wnt/Notum spatial feedback inhibition controls neoblast differentiation to regulate reversible growth of the planarian brain. Development 2015; 142:4217-29. [PMID: 26525673 DOI: 10.1242/dev.123612] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2015] [Accepted: 10/27/2015] [Indexed: 12/20/2022]
Abstract
Mechanisms determining final organ size are poorly understood. Animals undergoing regeneration or ongoing adult growth are likely to require sustained and robust mechanisms to achieve and maintain appropriate sizes. Planarians, well known for their ability to undergo whole-body regeneration using pluripotent adult stem cells of the neoblast population, can reversibly scale body size over an order of magnitude by controlling cell number. Using quantitative analysis, we showed that after injury planarians perfectly restored brain:body proportion by increasing brain cell number through epimorphosis or decreasing brain cell number through tissue remodeling (morphallaxis), as appropriate. We identified a pathway controlling a brain size set-point that involves feedback inhibition between wnt11-6/wntA/wnt4a and notum, encoding conserved antagonistic signaling factors expressed at opposite brain poles. wnt11-6/wntA/wnt4a undergoes feedback inhibition through canonical Wnt signaling but is likely to regulate brain size in a non-canonical pathway independently of beta-catenin-1 and APC. Wnt/Notum signaling tunes numbers of differentiated brain cells in regenerative growth and tissue remodeling by influencing the abundance of brain progenitors descended from pluripotent stem cells, as opposed to regulating cell death. These results suggest that the attainment of final organ size might be accomplished by achieving a balance of positional signaling inputs that regulate the rates of tissue production.
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Affiliation(s)
- Eric M Hill
- Department of Molecular Biosciences, Northwestern University, Evanston, IL 60208, USA
| | - Christian P Petersen
- Department of Molecular Biosciences, Northwestern University, Evanston, IL 60208, USA Robert Lurie Comprehensive Cancer Center, Northwestern University, Evanston, IL 60208, USA
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8
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Abstract
PURPOSE OF REVIEW Recent basic studies have yielded important new insights into the molecular mechanisms that regulate growth locally. Simultaneously, clinical studies have identified new molecular defects that cause growth failure and overgrowth, and genome-wide association studies have elucidated the genetic basis for normal human height variation. RECENT FINDINGS The Hippo pathway has emerged as one of the major mechanisms controlling organ size. In addition, an extensive genetic program has been described that allows rapid body growth in the fetus and infant but then causes growth to slow with age in multiple tissues. In human genome-wide association studies, hundreds of loci associated with adult stature have been identified; many appear to involve genes that function locally in the growth plate. Clinical genetic studies have identified a new genetic abnormality, microduplication of Xq26.3, that is responsible for growth hormone excess, and a gene, DNMT3A, in which mutations cause an overgrowth syndrome through epigenetic mechanisms. SUMMARY These recent advances in our understanding of somatic growth not only provide insight into childhood growth disorders but also have broader medical applications because disruption of these regulatory systems contributes to oncogenesis.
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Affiliation(s)
- Julian C Lui
- Program in Developmental Endocrinology and Genetics, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health (NIH), Bethesda, Maryland 20892, USA
| | - Presley Garrison
- Program in Developmental Endocrinology and Genetics, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health (NIH), Bethesda, Maryland 20892, USA
| | - Jeffrey Baron
- Program in Developmental Endocrinology and Genetics, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health (NIH), Bethesda, Maryland 20892, USA
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Leri A, Rota M, Hosoda T, Goichberg P, Anversa P. Cardiac stem cell niches. Stem Cell Res 2014; 13:631-46. [PMID: 25267073 DOI: 10.1016/j.scr.2014.09.001] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/23/2014] [Revised: 08/07/2014] [Accepted: 09/01/2014] [Indexed: 02/07/2023] Open
Abstract
The critical role that stem cell niches have in cardiac homeostasis and myocardial repair following injury is the focus of this review. Cardiac niches represent specialized microdomains where the quiescent and activated state of resident stem cells is regulated. Alterations in niche function with aging and cardiac diseases result in abnormal sites of cardiomyogenesis and inadequate myocyte formation. The relevance of Notch1 signaling, gap-junction formation, HIF-1α and metabolic state in the regulation of stem cell growth and differentiation within the cardiac niches are discussed.
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Affiliation(s)
- Annarosa Leri
- Departments of Anesthesia and Medicine, Division of Cardiovascular Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA 02115, USA.
| | - Marcello Rota
- Departments of Anesthesia and Medicine, Division of Cardiovascular Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA 02115, USA
| | - Toru Hosoda
- Departments of Anesthesia and Medicine, Division of Cardiovascular Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA 02115, USA
| | - Polina Goichberg
- Departments of Anesthesia and Medicine, Division of Cardiovascular Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA 02115, USA
| | - Piero Anversa
- Departments of Anesthesia and Medicine, Division of Cardiovascular Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA 02115, USA.
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Phillips JE, Gomer RH. The p21-activated kinase (PAK) family member PakD is required for chemorepulsion and proliferation inhibition by autocrine signals in Dictyostelium discoideum. PLoS One 2014; 9:e96633. [PMID: 24797076 PMCID: PMC4010531 DOI: 10.1371/journal.pone.0096633] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2014] [Accepted: 04/09/2014] [Indexed: 11/19/2022] Open
Abstract
In Dictyostelium discoideum, the secreted proteins AprA and CfaD function as reporters of cell density and regulate cell number by inhibiting proliferation at high cell densities. AprA also functions to disperse groups of cells at high density by acting as a chemorepellent. However, the signal transduction pathways associated with AprA and CfaD are not clear, and little is known about how AprA affects the cytoskeleton to regulate cell movement. We found that the p21-activated kinase (PAK) family member PakD is required for both the proliferation-inhibiting activity of AprA and CfaD and the chemorepellent activity of AprA. Similar to cells lacking AprA or CfaD, cells lacking PakD proliferate to a higher cell density than wild-type cells. Recombinant AprA and CfaD inhibit the proliferation of wild-type cells but not cells lacking PakD. Like AprA and CfaD, PakD affects proliferation but does not significantly affect growth (the accumulation of mass) on a per-nucleus basis. In contrast to wild-type cells, cells lacking PakD are not repelled from a source of AprA, and colonies of cells lacking PakD expand at a slower rate than wild-type cells, indicating that PakD is required for AprA-mediated chemorepulsion. A PakD-GFP fusion protein localizes to an intracellular punctum that is not the nucleus or centrosome, and PakD-GFP is also occasionally observed at the rear cortex of moving cells. Vegetative cells lacking PakD show excessive actin-based filopodia-like structures, suggesting that PakD affects actin dynamics, consistent with previously characterized roles of PAK proteins in actin regulation. Together, our results implicate PakD in AprA/CfaD signaling and show that a PAK protein is required for proper chemorepulsive cell movement in Dictyostelium.
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Affiliation(s)
- Jonathan E. Phillips
- Department of Biology, Texas A&M University, College Station, Texas, United States of America
| | - Richard H. Gomer
- Department of Biology, Texas A&M University, College Station, Texas, United States of America
- * E-mail:
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Shimono K, Fujishima K, Nomura T, Ohashi M, Usui T, Kengaku M, Toyoda A, Uemura T. An evolutionarily conserved protein CHORD regulates scaling of dendritic arbors with body size. Sci Rep 2014; 4:4415. [PMID: 24643112 PMCID: PMC3958717 DOI: 10.1038/srep04415] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2014] [Accepted: 03/04/2014] [Indexed: 12/17/2022] Open
Abstract
Most organs scale proportionally with body size through regulation of individual cell size and/or cell number. Here we addressed how postmitotic and morphologically complex cells such as neurons scale with the body size by using the dendritic arbor of one Drosophila sensory neuron as an assay system. In small adults eclosed under a limited-nutrition condition, the wild-type neuron preserved the branching complexity of the arbor, but scaled down the entire arbor, making a “miniature”. In contrast, mutant neurons for the Insulin/IGF signaling (IIS) or TORC1 pathway exhibited “undergrowth”, which was characterized by decreases in both the branching complexity and the arbor size, despite a normal diet. These contrasting phenotypes hinted that a novel regulatory mechanism contributes to the dendritic scaling in wild-type neurons. Indeed, we isolated a mutation in the gene CHORD/morgana that uncoupled the neuron size and the body size: CHORD mutant neurons generated miniature dendritic arbors regardless of the body size. CHORD encodes an evolutionarily conserved co-chaperone of HSP90. Our results support the notion that dendritic growth and branching are controlled by partly separate mechanisms. The IIS/TORC1 pathways control both growth and branching to avert underdevelopment, whereas CHORD together with TORC2 realizes proportional scaling of the entire arbor.
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Affiliation(s)
- Kohei Shimono
- Graduate School of Biostudies, Kyoto University, Kyoto 606-8501, Japan
| | - Kazuto Fujishima
- Institute for Integrated Cell-Material Sciences (WPI-iCeMS), Kyoto University Kyoto 606-8501, Japan
| | - Takafumi Nomura
- Graduate School of Biostudies, Kyoto University, Kyoto 606-8501, Japan
| | - Masayoshi Ohashi
- Graduate School of Biostudies, Kyoto University, Kyoto 606-8501, Japan
| | - Tadao Usui
- Graduate School of Biostudies, Kyoto University, Kyoto 606-8501, Japan
| | - Mineko Kengaku
- 1] Graduate School of Biostudies, Kyoto University, Kyoto 606-8501, Japan [2] Institute for Integrated Cell-Material Sciences (WPI-iCeMS), Kyoto University Kyoto 606-8501, Japan
| | - Atsushi Toyoda
- Center for Information Biology, National Institute of Genetics, Mishima, Shizuoka, Japan
| | - Tadashi Uemura
- Graduate School of Biostudies, Kyoto University, Kyoto 606-8501, Japan
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Bianconi E, Piovesan A, Facchin F, Beraudi A, Casadei R, Frabetti F, Vitale L, Pelleri MC, Tassani S, Piva F, Perez-Amodio S, Strippoli P, Canaider S. An estimation of the number of cells in the human body. Ann Hum Biol 2013; 40:463-71. [PMID: 23829164 DOI: 10.3109/03014460.2013.807878] [Citation(s) in RCA: 505] [Impact Index Per Article: 45.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
BACKGROUND All living organisms are made of individual and identifiable cells, whose number, together with their size and type, ultimately defines the structure and functions of an organism. While the total cell number of lower organisms is often known, it has not yet been defined in higher organisms. In particular, the reported total cell number of a human being ranges between 10(12) and 10(16) and it is widely mentioned without a proper reference. AIM To study and discuss the theoretical issue of the total number of cells that compose the standard human adult organism. SUBJECTS AND METHODS A systematic calculation of the total cell number of the whole human body and of the single organs was carried out using bibliographical and/or mathematical approaches. RESULTS A current estimation of human total cell number calculated for a variety of organs and cell types is presented. These partial data correspond to a total number of 3.72 × 10(13). CONCLUSIONS Knowing the total cell number of the human body as well as of individual organs is important from a cultural, biological, medical and comparative modelling point of view. The presented cell count could be a starting point for a common effort to complete the total calculation.
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Affiliation(s)
- Eva Bianconi
- Department of Experimental, Diagnostic and Specialty Medicine, University of Bologna , Bologna , Italy
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A Dictyostelium secreted factor requires a PTEN-like phosphatase to slow proliferation and induce chemorepulsion. PLoS One 2013; 8:e59365. [PMID: 23555023 PMCID: PMC3595242 DOI: 10.1371/journal.pone.0059365] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2012] [Accepted: 02/13/2013] [Indexed: 02/02/2023] Open
Abstract
In Dictyostelium discoideum, AprA and CfaD are secreted proteins that inhibit cell proliferation. We found that the proliferation of cells lacking CnrN, a phosphatase and tensin homolog (PTEN)-like phosphatase, is not inhibited by exogenous AprA and is increased by exogenous CfaD. The expression of CnrN in cnrN cells partially rescues these altered sensitivities, suggesting that CnrN is necessary for the ability of AprA and CfaD to inhibit proliferation. Cells lacking CnrN accumulate normal levels of AprA and CfaD. Like cells lacking AprA and CfaD, cnrN cells proliferate faster and reach a higher maximum cell density than wild type cells, tend to be multinucleate, accumulate normal levels of mass and protein per nucleus, and form less viable spores. When cnrN cells expressing myc-tagged CnrN are stimulated with a mixture of rAprA and rCfaD, levels of membrane-associated myc-CnrN increase. AprA also causes chemorepulsion of Dictyostelium cells, and CnrN is required for this process. Combined, these results suggest that CnrN functions in a signal transduction pathway downstream of AprA and CfaD mediating some, but not all, of the effects of AprA and CfaD.
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Jang W, Schwartz OG, Gomer RH. A cell number counting factor alters cell metabolism. Commun Integr Biol 2013; 2:293-7. [PMID: 19721869 DOI: 10.4161/cib.2.4.8470] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2009] [Accepted: 03/16/2009] [Indexed: 11/19/2022] Open
Abstract
It is still not clear how organisms regulate the size of appendages or organs during development. During development, Dictyostelium discoideum cells form groups of approximately 2 x 10(4) cells. The cells secrete a protein complex called counting factor (CF) that allows them to sense the local cell density. If there are too many cells in a group, as indicated by high extracellular concentrations of CF, the cells break up the group by decreasing cell-cell adhesion and increasing random cell motility. As a part of the signal transduction pathway, CF decreases the activity of glucose-6-phosphatase to decrease internal glucose levels. CF also decreases the levels of fructose-1,6-bisphosphate and increases the levels of glucose-6-phosphate and fructose-6-phosphate. In this report, we focus on how a secreted signal used to regulate the size of a group of cells regulates many basic aspects of cell metabolism, including the levels of pyruvate, lactate, and ATP, and oxygen consumption.
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Affiliation(s)
- Wonhee Jang
- Department of Life Science; Dongguk University; Seoul, South Korea
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15
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Tang Y, Gomer RH. CnrN regulates Dictyostelium group size using a counting factor-independent mechanism. Commun Integr Biol 2012; 1:185-7. [PMID: 19704889 DOI: 10.4161/cib.1.2.7255] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2008] [Accepted: 10/22/2008] [Indexed: 11/19/2022] Open
Abstract
One of the simplest examples of a complex behavior is the aggregation of solitary Dictyostelium discoideum amoebae to form a 20,000-cell fruiting body. A field of starving amoebae first breaks up into territories. In each territory, the cells form a spider-like pattern of streams of cells. As part of a negative feedback loop, counting factor (CF), a secreted protein complex whose concentration increases with the size of the stream, prevents over-sized fruiting bodies from being formed by increasing cell motility and decreasing cell-cell adhesion, which causes the breakup of excessively large streams. Cells lacking the phosphatase CnrN (cnrN(-) cells) form small aggregation territories and few streams.1 In this report, we present computer simulations that suggest that in the absence of stream formation, CF should be unable to affect group size. As predicted, cnrN(-) group size is insensitive to the addition or depletion of CF. Together, the data indicate that CnrN regulates group size by regulating both the break-up of a field of cells into aggregation territories and stream formation during development, and that CnrN-mediated and CF-mediated group size regulation use different mechanisms.
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Affiliation(s)
- Yitai Tang
- Department of Biochemistry and Cell Biology; Rice University; Houston, Texas USA
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16
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Jaiswal P, Soldati T, Thewes S, Baskar R. Regulation of aggregate size and pattern by adenosine and caffeine in cellular slime molds. BMC DEVELOPMENTAL BIOLOGY 2012; 12:5. [PMID: 22269093 PMCID: PMC3341216 DOI: 10.1186/1471-213x-12-5] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/22/2011] [Accepted: 01/23/2012] [Indexed: 02/06/2023]
Abstract
BACKGROUND Multicellularity in cellular slime molds is achieved by aggregation of several hundreds to thousands of cells. In the model slime mold Dictyostelium discoideum, adenosine is known to increase the aggregate size and its antagonist caffeine reduces the aggregate size. However, it is not clear if the actions of adenosine and caffeine are evolutionarily conserved among other slime molds known to use structurally unrelated chemoattractants. We have examined how the known factors affecting aggregate size are modulated by adenosine and caffeine. RESULT Adenosine and caffeine induced the formation of large and small aggregates respectively, in evolutionarily distinct slime molds known to use diverse chemoattractants for their aggregation. Due to its genetic tractability, we chose D. discoideum to further investigate the factors affecting aggregate size. The changes in aggregate size are caused by the effect of the compounds on several parameters such as cell number and size, cell-cell adhesion, cAMP signal relay and cell counting mechanisms. While some of the effects of these two compounds are opposite to each other, interestingly, both compounds increase the intracellular glucose level and strengthen cell-cell adhesion. These compounds also inhibit the synthesis of cAMP phosphodiesterase (PdsA), weakening the relay of extracellular cAMP signal. Adenosine as well as caffeine rescue mutants impaired in stream formation (pde4- and pdiA-) and colony size (smlA- and ctnA-) and restore their parental aggregate size. CONCLUSION Adenosine increased the cell division timings thereby making large number of cells available for aggregation and also it marginally increased the cell size contributing to large aggregate size. Reduced cell division rates and decreased cell size in the presence of caffeine makes the aggregates smaller than controls. Both the compounds altered the speed of the chemotactic amoebae causing a variation in aggregate size. Our data strongly suggests that cytosolic glucose and extracellular cAMP levels are the other major determinants regulating aggregate size and pattern. Importantly, the aggregation process is conserved among different lineages of cellular slime molds despite using unrelated signalling molecules for aggregation.
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Affiliation(s)
- Pundrik Jaiswal
- Department of Biotechnology, Indian Institute of Technology-Madras, Chennai-600036, India
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Phillips JE, Huang E, Shaulsky G, Gomer RH. The putative bZIP transcription factor BzpN slows proliferation and functions in the regulation of cell density by autocrine signals in Dictyostelium. PLoS One 2011; 6:e21765. [PMID: 21760904 PMCID: PMC3131300 DOI: 10.1371/journal.pone.0021765] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2011] [Accepted: 06/06/2011] [Indexed: 11/27/2022] Open
Abstract
The secreted proteins AprA and CfaD function as autocrine signals that inhibit cell proliferation in Dictyostelium discoideum, thereby regulating cell numbers by a negative feedback mechanism. We report here that the putative basic leucine zipper transcription factor BzpN plays a role in the inhibition of proliferation by AprA and CfaD. Cells lacking BzpN proliferate more rapidly than wild-type cells but do not reach a higher stationary density. Recombinant AprA inhibits wild-type cell proliferation but does not inhibit the proliferation of cells lacking BzpN. Recombinant CfaD also inhibits wild-type cell proliferation, but promotes the proliferation of cells lacking BzpN. Overexpression of BzpN results in a reduced cell density at stationary phase, and this phenotype requires AprA, CfaD, and the kinase QkgA. Conditioned media from high-density cells stops the proliferation of wild-type but not bzpN− cells and induces a nuclear localization of a BzpN-GFP fusion protein, though this localization does not require AprA or CfaD. Together, the data suggest that BzpN is necessary for some but not all of the effects of AprA and CfaD, and that BzpN may function downstream of AprA and CfaD in a signal transduction pathway that inhibits proliferation.
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Affiliation(s)
- Jonathan E. Phillips
- Department of Biochemistry and Cell Biology, Rice University, Houston, Texas, United States of America
| | - Eryong Huang
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, United States of America
| | - Gad Shaulsky
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, United States of America
| | - Richard H. Gomer
- Department of Biology, Texas A&M University, College Station, Texas, United States of America
- * E-mail:
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Abstract
The social amoeba Dictyostelium discoideum is one of the leading model systems used to study how cells count themselves to determine the number and/or density of cells. In this review, we describe work on three different cell-density sensing systems used by Dictyostelium. The first involves a negative feedback loop in which two secreted signals inhibit cell proliferation during the growth phase. As the cell density increases, the concentrations of the secreted factors concomitantly increase, allowing the cells to sense their density. The two signals act as message authenticators for each other, and the existence of two different signals that require each other for activity may explain why previous efforts to identify autocrine proliferation-inhibiting signals in higher eukaryotes have generally failed. The second system involves a signal made by growing cells that is secreted only when they starve. This then allows cells to sense the density of just the starving cells, and is an example of a mechanism that allows cells in a tissue to sense the density of one specific cell type. The third cell density counting system involves cells in aggregation streams secreting a signal that limits the size of fruiting bodies. Computer simulations predicted, and experiments then showed, that the factor increases random cell motility and decreases cell-cell adhesion to cause streams to break up if there are too many cells in the stream. Together, studies on Dictyostelium cell density counting systems will help elucidate how higher eukaryotes regulate the size and composition of tissues.
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Affiliation(s)
- Richard H Gomer
- Department of Biology, ILSB MS 3474, Texas A&M University, College Station, Texas 77843-3474, USA.
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The ROCO kinase QkgA is necessary for proliferation inhibition by autocrine signals in Dictyostelium discoideum. EUKARYOTIC CELL 2010; 9:1557-65. [PMID: 20709790 DOI: 10.1128/ec.00121-10] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
AprA and CfaD are secreted proteins that function as autocrine signals to inhibit cell proliferation in Dictyostelium discoideum. Cells lacking AprA or CfaD proliferate rapidly, and adding AprA or CfaD to cells slows proliferation. Cells lacking the ROCO kinase QkgA proliferate rapidly, with a doubling time 83% of that of the wild type, and overexpression of a QkgA-green fluorescent protein (GFP) fusion protein slows cell proliferation. We found that qkgA(-) cells accumulate normal levels of extracellular AprA and CfaD. Exogenous AprA or CfaD does not slow the proliferation of cells lacking qkgA, and expression of QkgA-GFP in qkgA(-) cells rescues this insensitivity. Like cells lacking AprA or CfaD, cells lacking QkgA tend to be multinucleate, accumulate nuclei rapidly, and show a mass and protein accumulation per nucleus like those of the wild type, suggesting that QkgA negatively regulates proliferation but not growth. Despite their rapid proliferation, cells lacking AprA, CfaD, or QkgA expand as a colony on bacteria less rapidly than the wild type. Unlike AprA and CfaD, QkgA does not affect spore viability following multicellular development. Together, these results indicate that QkgA is necessary for proliferation inhibition by AprA and CfaD, that QkgA mediates some but not all of the effects of AprA and CfaD, and that QkgA may function downstream of these proteins in a signal transduction pathway regulating proliferation.
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Lui JC, Forcinito P, Chang M, Chen W, Barnes KM, Baron J. Coordinated postnatal down-regulation of multiple growth-promoting genes: evidence for a genetic program limiting organ growth. FASEB J 2010; 24:3083-92. [PMID: 20371622 DOI: 10.1096/fj.09-152835] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Children grow, but adults do not. The cessation of growth in multiple organs is the end result of a progressive decline in cell proliferation beginning in early life. The mechanisms responsible for this growth deceleration are largely unknown. Using expression microarray and real-time PCR, we identified a common program of gene expression in lung, kidney, and liver during growth deceleration in juvenile rats. Gene ontology analyses and siRNA-mediated knockdown in vitro indicated that many of the down-regulated genes are growth promoting. Down-regulated genes in the program showed declining histone H3K4 trimethylation with age, implicating underlying epigenetic mechanisms. To investigate the physiological processes driving the genetic program, a tryptophan-deficient diet was used to temporarily inhibit juvenile growth in newborn rats for 4 wk. Afterward, microarray analysis showed that the genetic program had been delayed, implying that it is driven by body growth itself rather than age. Taken together, the findings suggest that growth in early life induces progressive down-regulation of a large set of proliferation-stimulating genes, causing organ growth to slow and eventually cease.
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Affiliation(s)
- Julian C Lui
- Developmental Endocrinology Branch, Program in Developmental Endocrinology and Genetics, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, CRC, Room 1-3330, 10 Center Dr., MSC-1103, Bethesda, MD 20892-1103, USA.
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Bakthavatsalam D, Choe JM, Hanson NE, Gomer RH. A Dictyostelium chalone uses G proteins to regulate proliferation. BMC Biol 2009; 7:44. [PMID: 19635129 PMCID: PMC2726123 DOI: 10.1186/1741-7007-7-44] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2009] [Accepted: 07/27/2009] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Several studies have shown that organ size, and the proliferation of tumor metastases, may be regulated by negative feedback loops in which autocrine secreted factors called chalones inhibit proliferation. However, very little is known about chalones, and how cells sense them. We previously identified two secreted proteins, AprA and CfaD, which act as chalones in Dictyostelium. Cells lacking AprA or CfaD proliferate faster than wild-type cells, and adding recombinant AprA or CfaD to cells slows their proliferation. RESULTS We show here that cells lacking the G protein components Galpha8, Galpha9, and Gbeta proliferate faster than wild-type cells despite secreting normal or high levels of AprA and CfaD. Compared with wild-type cells, the proliferation of galpha8-, galpha9- and gbeta- cells are only weakly inhibited by recombinant AprA (rAprA). Like AprA and CfaD, Galpha8 and Gbeta inhibit cell proliferation but not cell growth (the rate of increase in mass and protein per nucleus), whereas Galpha9 inhibits both proliferation and growth. galpha8- cells show normal cell-surface binding of rAprA, whereas galpha9- and gbeta- cells have fewer cell-surface rAprA binding sites, suggesting that Galpha9 and Gbeta regulate the synthesis or processing of the AprA receptor. Like other ligands that activate G proteins, rAprA induces the binding of [3H]GTP to membranes, and GTPgammaS inhibits the binding of rAprA to membranes. Both AprA-induced [3H]GTP binding and the GTPgammaS inhibition of rAprA binding require Galpha8 and Gbeta but not Galpha9. Like aprA- cells, galpha8- cells have reduced spore viability. CONCLUSION This study shows that Galpha8 and Gbeta are part of the signal transduction pathway used by AprA to inhibit proliferation but not growth in Dictyostelium, whereas Galpha9 is part of a differealnt pathway that regulates both proliferation and growth, and that a chalone signal transduction pathway uses G proteins.
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Finkielstain GP, Forcinito P, Lui JCK, Barnes KM, Marino R, Makaroun S, Nguyen V, Lazarus JE, Nilsson O, Baron J. An extensive genetic program occurring during postnatal growth in multiple tissues. Endocrinology 2009; 150:1791-800. [PMID: 19036884 PMCID: PMC2659288 DOI: 10.1210/en.2008-0868] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Mammalian somatic growth is rapid in early postnatal life but then slows and eventually ceases in multiple tissues. We hypothesized that there exists a postnatal gene expression program that is common to multiple tissues and is responsible for this coordinate growth deceleration. Consistent with this hypothesis, microarray analysis identified more than 1600 genes that were regulated with age (1 vs. 4 wk) coordinately in kidney, lung, and heart of male mice, including many genes that regulate proliferation. As examples, we focused on three growth-promoting genes, Igf2, Mest, and Peg3, that were markedly down-regulated with age. In situ hybridization revealed that expression occurred in organ-specific parenchymal cells and suggested that the decreasing expression with age was due primarily to decreased expression per cell rather than a decreased number of expressing cells. The declining expression of these genes was slowed during hypothyroidism and growth inhibition (induced by propylthiouracil at 0-5 wk of age) in male rats, suggesting that the normal decline in expression is driven by growth rather than by age per se. We conclude that there exists an extensive genetic program occurring during postnatal life. Many of the involved genes are regulated coordinately in multiple organs, including many genes that regulate cell proliferation. At least some of these are themselves apparently regulated by growth, suggesting that, in the embryo, a gene expression pattern is established that allows for rapid somatic growth of multiple tissues, but then, during postnatal life, this growth leads to negative-feedback changes in gene expression that in turn slow and eventually halt somatic growth, thus imposing a fundamental limit on adult body size.
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Affiliation(s)
- Gabriela P Finkielstain
- Developmental Endocrinology Branch, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892-1103, USA
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23
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Ostrowski EA, Katoh M, Shaulsky G, Queller DC, Strassmann JE. Kin discrimination increases with genetic distance in a social amoeba. PLoS Biol 2009; 6:e287. [PMID: 19067487 PMCID: PMC2586364 DOI: 10.1371/journal.pbio.0060287] [Citation(s) in RCA: 106] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2008] [Accepted: 10/10/2008] [Indexed: 12/04/2022] Open
Abstract
In the social amoeba Dictyostelium discoideum, thousands of cells aggregate upon starvation to form a multicellular fruiting body, and approximately 20% of them die to form a stalk that benefits the others. The aggregative nature of multicellular development makes the cells vulnerable to exploitation by cheaters, and the potential for cheating is indeed high. Cells might avoid being victimized if they can discriminate among individuals and avoid those that are genetically different. We tested how widely social amoebae cooperate by mixing isolates from different localities that cover most of their natural range. We show here that different isolates partially exclude one another during aggregation, and there is a positive relationship between the extent of this exclusion and the genetic distance between strains. Our findings demonstrate that D. discoideum cells co-aggregate more with genetically similar than dissimilar individuals, suggesting the existence of a mechanism that discerns the degree of genetic similarity between individuals in this social microorganism. In social amoebae such as Dictyostelium discoideum, cells aggregate to form a multicellular slug that migrates and then forms a fruiting body, which contains live spores (which go on to make new amoebae) and dead stalk cells. Unlike animals where all the cells descend from one fertilized egg, social amoeba fruiting bodies can contain cells with different genotypes. This potential for chimerism creates a conceptual problem in that “cheater” cells could arise that preferentially become reproductive spores and force the victims to become stalk cells and die. One way that amoebae could avoid being cheated is if they recognize and preferentially aggregate with genetically similar cells while avoiding genetically distant cells—a process called kin discrimination. We tested whether cells of D. discoideum could discriminate in this way. We mixed cells from genetically distinct strains and found that they segregate during multicellular development. The degree of segregation increases in a graded fashion with the genetic distance between strains. Our results demonstrate the existence of kin discrimination in D. discoideum, an ability that is likely to reduce the potential for cheating and ensure that the death of the stalk cells provides a fitness advantage to related individuals. Genetically based discrimination in social amoebae may help these cells to avoid cheaters that take advantage of their altruistic behavior.
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Affiliation(s)
- Elizabeth A Ostrowski
- Department of Ecology and Evolutionary Biology, Rice University, Houston, Texas, USA.
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Choe JM, Bakthavatsalam D, Phillips JE, Gomer RH. Dictyostelium cells bind a secreted autocrine factor that represses cell proliferation. BMC BIOCHEMISTRY 2009; 10:4. [PMID: 19187549 PMCID: PMC2644720 DOI: 10.1186/1471-2091-10-4] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/10/2008] [Accepted: 02/02/2009] [Indexed: 11/10/2022]
Abstract
BACKGROUND Dictyostelium cells secrete the proteins AprA and CfaD. Cells lacking either AprA or CfaD proliferate faster than wild type, while AprA or CfaD overexpressor cells proliferate slowly, indicating that AprA and CfaD are autocrine factors that repress proliferation. CfaD interacts with AprA and requires the presence of AprA to slow proliferation. To determine if CfaD is necessary for the ability of AprA to slow proliferation, whether AprA binds to cells, and if so whether the binding requires the presence of CfaD, we examined the binding and effect on proliferation of recombinant AprA. RESULTS We find that the extracellular accumulation of AprA increases with cell density and reaches a concentration of 0.3 microg/ml near a stationary cell density. When added to wild-type or aprA- cells, recombinant AprA (rAprA) significantly slows proliferation at 0.1 microg/ml and higher concentrations. From 4 to 64 microg/ml, the effect of rAprA is at a plateau, slowing but not stopping proliferation. The proliferation-inhibiting activity of rAprA is roughly the same as that of native AprA in conditioned growth medium. Proliferating aprA- cells show saturable binding of rAprA to 92,000 +/- 11,000 cell-surface receptors with a KD of 0.03 +/- 0.02 microg/ml. There appears to be one class of binding site, and no apparent cooperativity. Native AprA inhibits the binding of rAprA to aprA- cells with a Ki of 0.03 mug/ml, suggesting that the binding kinetics of rAprA are similar to those of native AprA. The proliferation of cells lacking CrlA, a cAMP receptor-like protein, or cells lacking CfaD are not affected by rAprA. Surprisingly, both cell types still bind rAprA. CONCLUSION Together, the data suggest that AprA functions as an autocrine proliferation-inhibiting factor by binding to cell surface receptors. Although AprA requires CfaD for activity, it does not require CfaD to bind to cells, suggesting the possibility that cells have an AprA receptor and a CfaD receptor, and activation of both receptors is required to slow proliferation. We previously found that crlA- cells are sensitive to CfaD. Combined with the results presented here, this suggests that CrlA is not the AprA or CfaD receptor, and may be the receptor for an unknown third factor that is required for AprA and CfaD activity.
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Affiliation(s)
- Jonathan M Choe
- Department of Biochemistry and Cell Biology, MS-140, Rice University, Houston, TX 77005-1892, USA
| | | | - Jonathan E Phillips
- Department of Biochemistry and Cell Biology, MS-140, Rice University, Houston, TX 77005-1892, USA
| | - Richard H Gomer
- Department of Biochemistry and Cell Biology, MS-140, Rice University, Houston, TX 77005-1892, USA
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A protein with similarity to PTEN regulates aggregation territory size by decreasing cyclic AMP pulse size during Dictyostelium discoideum development. EUKARYOTIC CELL 2008; 7:1758-70. [PMID: 18676953 DOI: 10.1128/ec.00210-08] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
An interesting but largely unanswered biological question is how eukaryotic organisms regulate the size of multicellular tissues. During development, a lawn of Dictyostelium cells breaks up into territories, and within the territories the cells aggregate in dendritic streams to form groups of approximately 20,000 cells. Using random insertional mutagenesis to search for genes involved in group size regulation, we found that an insertion in the cnrN gene affects group size. Cells lacking CnrN (cnrN(-)) form abnormally small groups, which can be rescued by the expression of exogenous CnrN. Relayed pulses of extracellular cyclic AMP (cAMP) direct cells to aggregate by chemotaxis to form aggregation territories and streams. cnrN(-) cells overaccumulate cAMP during development and form small territories. Decreasing the cAMP pulse size by treating cnrN(-) cells with cAMP phosphodiesterase or starving cnrN(-) cells at a low density rescues the small-territory phenotype. The predicted CnrN sequence has similarity to phosphatase and tensin homolog (PTEN), which in Dictyostelium inhibits cAMP-stimulated phosphatidylinositol 3-kinase signaling pathways. CnrN inhibits cAMP-stimulated phosphatidylinositol 3,4,5-trisphosphate accumulation, Akt activation, actin polymerization, and cAMP production. Our results suggest that CnrN is a protein with some similarities to PTEN and that it regulates cAMP signal transduction to regulate territory size.
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Bakthavatsalam D, Brock DA, Nikravan NN, Houston KD, Hatton RD, Gomer RH. The secreted Dictyostelium protein CfaD is a chalone. J Cell Sci 2008; 121:2473-80. [PMID: 18611962 DOI: 10.1242/jcs.026682] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
Dictyostelium discoideum cells secrete CfaD, a protein that is similar to cathepsin proteases. Cells that lack cfaD proliferate faster and reach a higher stationary-phase density than wild-type cells, whereas cells that overexpress CfaD proliferate slowly and reach the stationary phase when at a low density. On a per-nucleus basis, CfaD affects proliferation but not growth. The drawback of not having CfaD is a reduced spore viability. Recombinant CfaD has no detectable protease activity but, when added to cells, inhibits the proliferation of wild-type and cfaD(-) cells. The secreted protein AprA also inhibits proliferation. AprA is necessary for the effect of CfaD on proliferation. Molecular-sieve chromatography indicates that in conditioned growth medium, the 60 kDa CfaD is part of a approximately 150 kDa complex, and both chromatography and pull-down assays suggest that CfaD interacts with AprA. These results suggest that two interacting proteins may function together as a chalone signal in a negative feedback loop that slows Dictyostelium cell proliferation.
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Ma L, Cantrup R, Varrault A, Colak D, Klenin N, Götz M, McFarlane S, Journot L, Schuurmans C. Zac1 functions through TGFbetaII to negatively regulate cell number in the developing retina. Neural Dev 2007; 2:11. [PMID: 17559664 PMCID: PMC1913510 DOI: 10.1186/1749-8104-2-11] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2007] [Accepted: 06/08/2007] [Indexed: 12/25/2022] Open
Abstract
Background Organs are programmed to acquire a particular size during development, but the regulatory mechanisms that dictate when dividing progenitor cells should permanently exit the cell cycle and stop producing additional daughter cells are poorly understood. In differentiated tissues, tumor suppressor genes maintain a constant cell number and intact tissue architecture by controlling proliferation, apoptosis and cell dispersal. Here we report a similar role for two tumor suppressor genes, the Zac1 zinc finger transcription factor and that encoding the cytokine TGFβII, in the developing retina. Results Using loss and gain-of-function approaches, we show that Zac1 is an essential negative regulator of retinal size. Zac1 mutants develop hypercellular retinae due to increased progenitor cell proliferation and reduced apoptosis at late developmental stages. Consequently, supernumerary rod photoreceptors and amacrine cells are generated, the latter of which form an ectopic cellular layer, while other retinal cells are present in their normal number and location. Strikingly, Zac1 functions as a direct negative regulator of a rod fate, while acting cell non-autonomously to modulate amacrine cell number. We implicate TGFβII, another tumor suppressor and cytokine, as a Zac1-dependent amacrine cell negative feedback signal. TGFβII and phospho-Smad2/3, its downstream effector, are expressed at reduced levels in Zac1 mutant retinae, and exogenous TGFβII relieves the mutant amacrine cell phenotype. Moreover, treatment of wild-type retinae with a soluble TGFβ inhibitor and TGFβ receptor II (TGFβRII) conditional mutants generate excess amacrine cells, phenocopying the Zac1 mutant phenotype. Conclusion We show here that Zac1 has an essential role in cell number control during retinal development, akin to its role in tumor surveillance in mature tissues. Furthermore, we demonstrate that Zac1 employs a novel cell non-autonomous strategy to regulate amacrine cell number, acting in cooperation with a second tumor suppressor gene, TGFβII, through a negative feedback pathway. This raises the intriguing possibility that tumorigenicity may also be associated with the loss of feedback inhibition in mature tissues.
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Affiliation(s)
- Lin Ma
- IMCH, HBI, University of Calgary, T2N 4N1, Canada
| | | | - Annie Varrault
- Institut de Génomique Fonctionnelle, Montpellier, France
| | - Dilek Colak
- Institute of Stem Cell Research, GSF, München, Germany
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Bakthavatsalam D, Brazill D, Gomer RH, Eichinger L, Rivero F, Noegel AA. A G protein-coupled receptor with a lipid kinase domain is involved in cell-density sensing. Curr Biol 2007; 17:892-7. [PMID: 17481898 DOI: 10.1016/j.cub.2007.04.029] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2007] [Revised: 04/05/2007] [Accepted: 04/05/2007] [Indexed: 11/30/2022]
Abstract
One mechanism multicellular structures use for controlling cell number [1, 2] involves the secretion and sensing of a factor, such as leptin [3] or myostatin [4], in mammals. Dictyostelium cells secrete autocrine factors for sensing cell density prior to aggregation and multicellular development [5, 6] such as CMF (conditioned-medium factor), which enables starving cells to respond to cAMP pulses [7-9]. Its actions are mediated by two receptors. CMFR1 activates a G protein-independent signaling pathway regulating gene expression [10]. An unknown Galpha1-dependent receptor activates phospholipase C (PLC), which regulates the lifetime of Galpha2-GTP [11-13]. Here, we describe RpkA, an unusual seven-transmembrane receptor that is fused to a C-terminal PIP5 kinase domain and that localizes in membranes of a late endosomal compartment. Loss of RpkA resulted in formation of persistent loose aggregates and altered expression of cAMP-regulated genes. The developmental defect can be rescued by full-length RpkA and the transmembrane domain only. The PIP5 kinase domain is dispensable for the developmental role of RpkA. rpkA- cells secrete and bind CMF but are unable to induce downstream responses. Inactivation of Galpha1, a negative regulator of CMF signaling, rescued the developmental defect of the rpkA- cells, suggesting that RpkA actions are mediated by Galpha1.
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Affiliation(s)
- Deenadayalan Bakthavatsalam
- Center for Biochemistry, Institute for Biochemistry I, Medical Faculty and Center for Molecular Medicine Cologne, University of Cologne, D-50931 Cologne, Germany
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Brock DA, van Egmond WN, Shamoo Y, Hatton RD, Gomer RH. A 60-kilodalton protein component of the counting factor complex regulates group size in Dictyostelium discoideum. EUKARYOTIC CELL 2006; 5:1532-8. [PMID: 16963635 PMCID: PMC1563584 DOI: 10.1128/ec.00169-06] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Much remains to be understood about how a group of cells or a tissue senses and regulates its size. Dictyostelium discoideum cells sense and regulate the size of groups and fruiting bodies using a secreted 450-kDa complex of proteins called counting factor (CF). Low levels of CF result in large groups, and high levels of CF result in small groups. We previously found three components of CF (D. A. Brock and R. H. Gomer, Genes Dev. 13:1960-1969, 1999; D. A. Brock, R. D. Hatton, D.-V. Giurgiutiu, B. Scott, R. Ammann, and R. H. Gomer, Development 129:3657-3668, 2002; and D. A. Brock, R. D. Hatton, D.-V. Giurgiutiu, B. Scott, W. Jang, R. Ammann, and R. H. Gomer, Eukaryot. Cell 2:788-797, 2003). We describe here a fourth component, CF60. CF60 has similarity to acid phosphatases, although it has very little, if any, acid phosphatase activity. CF60 is secreted by starving cells and is lost from the 450-kDa CF when a different CF component, CF50, is absent. Although we were unable to obtain cells lacking CF60, decreasing CF60 levels by antisense resulted in large groups, and overexpressing CF60 resulted in small groups. When added to wild-type cells, conditioned starvation medium from CF60 overexpressor cells as well as recombinant CF60 caused the formation of small groups. The ability of recombinant CF60 to decrease group size did not require the presence of the CF component CF45-1 or countin but did require the presence of CF50. Recombinant CF60 does not have acid phosphatase activity, indicating that the CF60 bioactivity is not due to a phosphatase activity. Together, the data suggest that CF60 is a component of CF, and thus this secreted signal has four different protein components.
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Affiliation(s)
- Debra A Brock
- Howard Hughes Medical Institute, Rice University, 6100 S. Main Street, Houston, Texas 77005-1892, USA
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30
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Kolbinger A, Gao T, Brock D, Ammann R, Kisters A, Kellermann J, Hatton D, Gomer RH, Wetterauer B. A cysteine-rich extracellular protein containing a PA14 domain mediates quorum sensing in Dictyostelium discoideum. EUKARYOTIC CELL 2005; 4:991-8. [PMID: 15947191 PMCID: PMC1151990 DOI: 10.1128/ec.4.6.991-998.2005] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Much remains to be understood about quorum-sensing factors that allow cells to sense their local density. Dictyostelium discoideum is a simple eukaryote that grows as single-celled amoebae and switches to multicellular development when food becomes limited. As the growing cells reach a high density, they begin expressing discoidin genes. The cells secrete an unknown factor, and at high cell densities the concomitant high levels of the factor induce discoidin expression. We report here the enrichment of discoidin-inducing complex (DIC), an approximately 400-kDa protein complex that induces discoidin expression during growth and development. Two proteins in the DIC preparation, DicA1 and DicB, were identified by sequencing proteolytic digests. DicA1 and DicB were expressed in Escherichia coli and tested for their ability to induce discoidin during growth and development. Recombinant DicB was unable to induce discoidin expression, while recombinant DicA1 was able to induce discoidin expression. This suggests that DicA1 is an active component of DIC and indicates that posttranslational modification is dispensable for activity. DicA1 mRNA is expressed in vegetative and developing cells. The mature secreted form of DicA1 has a molecular mass of 80 kDa and has a 24-amino-acid cysteine-rich repeat that is similar to repeats in Dictyostelium proteins, such as the extracellular matrix protein ecmB/PstA, the prespore cell-inducing factor PSI, and the cyclic AMP phosphodiesterase inhibitor PDI. Together, the data suggest that DicA1 is a component of a secreted quorum-sensing signal regulating discoidin gene expression during Dictyostelium growth and development.
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Affiliation(s)
- Alexandra Kolbinger
- Howard Hughes Medical Institute and Department of Biochemistry and Cell Biology, MS-140, Rice University, 6100 S. Main Street, Houston, TX 77005-1892, USA
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Abstract
Many cells appear to secrete factors called chalones that limit their proliferation, but in most cases the factors have not been identified. We found that growing Dictyostelium cells secrete a 60 kDa protein called AprA for autocrine proliferation repressor. AprA has similarity to putative bacterial proteins of unknown function. Compared with wild-type cells, aprA-null cells proliferate faster, while AprA overexpressing cells proliferate slower. Growing wild-type cells secrete a factor that inhibits the proliferation of wild-type and aprA- cells; this activity is not secreted by aprA- cells. AprA purified by immunoprecipitation also slows the proliferation of wild-type and aprA- cells. Compared with wild type, there is a higher percentage of multinucleate cells in the aprA- population, and when starved, aprA- cells form abnormal structures that contain fewer spores. AprA may thus decrease the number of multinucleate cells and increase spore production. Together, the data suggest that AprA functions as part of a Dictyostelium chalone.
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Jang W, Gomer RH. Exposure of cells to a cell number-counting factor decreases the activity of glucose-6-phosphatase to decrease intracellular glucose levels in Dictyostelium discoideum. EUKARYOTIC CELL 2005; 4:72-81. [PMID: 15643062 PMCID: PMC544156 DOI: 10.1128/ec.4.1.72-81.2005] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The development of Dictyostelium discoideum is a model for tissue size regulation, as these cells form groups of approximately 2 x 10(4) cells. The group size is regulated in part by a negative feedback pathway mediated by a secreted multipolypeptide complex called counting factor (CF). CF signal transduction involves decreasing intracellular CF glucose levels. A component of CF, countin, has the bioactivity of the entire CF complex, and an 8-min exposure of cells to recombinant countin decreases intracellular glucose levels. To understand how CF regulates intracellular glucose, we examined the effect of CF on enzymes involved in glucose metabolism. Exposure of cells to CF has little effect on amylase or glycogen phosphorylase, enzymes involved in glucose production from glycogen. Glucokinase activity (the first specific step of glycolysis) is inhibited by high levels of CF but is not affected by an 8-min exposure to countin. The second enzyme specific for glycolysis, phosphofructokinase, is not regulated by CF. There are two corresponding enzymes in the gluconeogenesis pathway, fructose-1,6-bisphosphatase and glucose-6-phosphatase. The first is not regulated by CF or countin, whereas glucose-6-phosphatase is regulated by both CF and an 8-min exposure to countin. The countin-induced changes in the Km and Vmax of glucose-6-phosphatase cause a decrease in glucose production that can account for the countin-induced decrease in intracellular glucose levels. It thus appears that part of the CF signal transduction pathway involves inhibiting the activity of glucose-6-phosphatase, decreasing intracellular glucose levels and affecting the levels of other metabolites, to regulate group size.
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Affiliation(s)
- Wonhee Jang
- Howard Hughes Medical Institute, Department of Biochemistry and Cell Biology, Rice University, Houston, TX 77005-1892, USA
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33
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Cohen JE, Jonsson T, Müller CB, Godfray HCJ, Savage VM. Body sizes of hosts and parasitoids in individual feeding relationships. Proc Natl Acad Sci U S A 2005; 102:684-9. [PMID: 15647346 PMCID: PMC545575 DOI: 10.1073/pnas.0408780102] [Citation(s) in RCA: 77] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
In a natural community of 49 species (12 species of aphids and 37 species of their parasitoids), body lengths of 2,151 parasitoid individuals were, to an excellent approximation, related to the body lengths of their individual aphid hosts by a power law with an exponent close to 3/4. Two alternative models predict this exponent. One is based on surface area to volume relationships. The other is based on recent developments in metabolic ecology. Both models require a changing ratio (in both host and parasitoid) of length to diameter with increasing body length. These changing ratios are manifested differently in the two models and result in testably different predictions for the scaling of body form with increasing size. The estimated exponent of 3/4 for the relationship between individual host body size and individual parasitoid body size degrades to an exponent of nearly 1/2, and the scatter in the relationship between aphid and parasitoid body length is substantially increased, if the average length of a parasitoid species is examined as a function of the average length of its aphid host species instead of using measurements of individuals.
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Affiliation(s)
- Joel E Cohen
- Laboratory of Populations, The Rockefeller University and Columbia University, Box 20, 1230 York Avenue, New York, NY 10021, USA.
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34
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Nilsson O, Baron J. Fundamental limits on longitudinal bone growth: growth plate senescence and epiphyseal fusion. Trends Endocrinol Metab 2004; 15:370-4. [PMID: 15380808 DOI: 10.1016/j.tem.2004.08.004] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Longitudinal bone growth occurs rapidly in early life but then slows and, eventually, ceases. The decline in growth rate is caused primarily by a decrease in the rate of chondrocyte proliferation and is accompanied by structural changes in growth plate cartilage. This programmed senescence does not appear to be caused by hormonal or other systemic mechanisms but is intrinsic to the growth plate itself. In particular, recent evidence indicates that senescence might occur because stem-like cells in the resting zone have a finite proliferative capacity, which is exhausted gradually. In some mammals, including humans, proliferative exhaustion is followed by epiphyseal fusion, an abrupt event in which the growth plate cartilage is replaced completely by bone.
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Affiliation(s)
- Ola Nilsson
- Developmental Endocrinology Branch, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA
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35
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Abstract
Very little is known about how the size of an organism, or a specific tissue in an organism, is regulated. Coordinating and regulating the size of tissues is necessary for proper development, wound healing, and regeneration. Defects in a tissue-size regulation mechanism could lead to birth defects or cancer. In addition, there is a strong psychological aspect to some areas of tissue size regulation, as many cosmetic surgery procedures involve enlarging or reducing the size of some body parts. This review addresses the little bit that we know about size regulation. A key concept is that the size of a tissue is the size of the component cells multiplied by the number of those cells. This breaks the size regulation problem down to two parts. The size of cells can be regulated by nutrient sensing and secreted factors, and may have an upper limit due to an upper limit of a genome's ability to produce mRNA's and thus proteins. To regulate the number of cells in a tissue, there are several simple theoretical models involving secreted factors. In one case, the cells can secrete a characteristic factor and the concentration of the factor will increase with the number of cells secreting it, allowing the tissue to sense its own size. In another scenario, a specific cell secretes a limited amount of a factor necessary for the survival of a target population, and this then limits the size of the target population. There are currently several examples of secreted factors that regulate tissue size, including myostatin, which regulates the amount of muscles, leptin, which regulates adipose tissue, and growth hormone and insulin-like growth factors which regulate total mass. In addition, there are factors such as the <<counting factor>> found in Dictyostelium that regulate the breakup of a tissue into sub-groups. A better understanding of how these factors regulate size will hopefully allow us to develop new therapeutic procedures to treat birth defects or diseases that affect tissue size.
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Affiliation(s)
- Céline Roisin-Bouffay
- Centre d'immunologie de Marseille-Luminy, CNRS-Inserm-Université de la Méditerranée, Campus de Luminy, Case 906, 13288 Marseille Cedex 09, France.
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36
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Stockinger B, Barthlott T, Kassiotis G. The concept of space and competition in immune regulation. Immunology 2004; 111:241-7. [PMID: 15009422 PMCID: PMC1782425 DOI: 10.1111/j.1365-2567.2004.01831.x] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2003] [Accepted: 01/13/2004] [Indexed: 12/31/2022] Open
Affiliation(s)
- Brigitta Stockinger
- Division of Molecular Immunology, The National Institute for Medical Research, The Ridgeway, Mill Hill, London NW7 1 AA, UK.
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37
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Pilling D, Buckley CD, Salmon M, Gomer RH. Inhibition of fibrocyte differentiation by serum amyloid P. THE JOURNAL OF IMMUNOLOGY 2004; 171:5537-46. [PMID: 14607961 PMCID: PMC4482350 DOI: 10.4049/jimmunol.171.10.5537] [Citation(s) in RCA: 237] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Wound healing and the dysregulated events leading to fibrosis both involve the proliferation and differentiation of fibroblasts and the deposition of extracellular matrix. Whether these fibroblasts are locally derived or from a circulating precursor population is unclear. Fibrocytes are a distinct population of fibroblast-like cells derived from peripheral blood monocytes that enter sites of tissue injury to promote angiogenesis and wound healing. We have found that CD14(+) peripheral blood monocytes cultured in the absence of serum or plasma differentiate into fibrocytes within 72 h. We purified the factor in serum and plasma that prevents the rapid appearance of fibrocytes, and identified it as serum amyloid P (SAP). Purified SAP inhibits fibrocyte differentiation at levels similar to those found in plasma, while depleting SAP reduces the ability of plasma to inhibit fibrocyte differentiation. Compared with sera from healthy individuals and patients with rheumatoid arthritis, sera from patients with scleroderma and mixed connective tissue disease, two systemic fibrotic diseases, were less able to inhibit fibrocyte differentiation in vitro and had correspondingly lower serum levels of SAP. These results suggest that low levels of SAP may thus augment pathological processes leading to fibrosis. These data also suggest mechanisms to inhibit fibrosis in chronic inflammatory conditions, or conversely to promote wound healing.
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Affiliation(s)
- Darrell Pilling
- Howard Hughes Medical Institute, Department of Biochemistry and Cell Biology, Rice University, Houston, TX 77005
| | - Christopher D. Buckley
- Department of Rheumatology, Rheumatology Research Group, University of Birmingham/Medical Research Council Centre for Immune Regulation, Medical School, University of Birmingham, Birmingham, West Midlands, United Kingdom
| | - Mike Salmon
- Department of Rheumatology, Rheumatology Research Group, University of Birmingham/Medical Research Council Centre for Immune Regulation, Medical School, University of Birmingham, Birmingham, West Midlands, United Kingdom
| | - Richard H. Gomer
- Howard Hughes Medical Institute, Department of Biochemistry and Cell Biology, Rice University, Houston, TX 77005
- Address correspondence and reprint requests to: Dr. Richard H. Gomer, Department of Biochemistry and Cell Biology, MS-140, Rice University, Houston, TX 77005-1892.
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Takano A, Akaza Y, Hasegawa Y, Issaeva M, Masamune Y, Kodaira KI, Shinohara H, Yasukawa H. Expression of Genes Coding for Cell-Cell Adhesion Proteins in Dictyostelium discoideum Mutants that Form Small Fruiting Bodies. Microbes Environ 2004. [DOI: 10.1264/jsme2.19.76] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Affiliation(s)
- Akinori Takano
- Division of Bioengineering, Faculty of Engineering, Toyama University
| | - Yuya Akaza
- Division of Bioengineering, Faculty of Engineering, Toyama University
| | - Yasuna Hasegawa
- Division of Bioengineering, Faculty of Engineering, Toyama University
| | - Marina Issaeva
- Department of Microbiology, Faculty of Pharmaceutical Sciences, Kanazawa University
| | - Yukito Masamune
- Department of Microbiology, Faculty of Pharmaceutical Sciences, Kanazawa University
| | - Ken-ichi Kodaira
- Division of Bioengineering, Faculty of Engineering, Toyama University
| | - Hiroaki Shinohara
- Division of Bioengineering, Faculty of Engineering, Toyama University
| | - Hiro Yasukawa
- Division of Bioengineering, Faculty of Engineering, Toyama University
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Gomer R, Gao T, Tang Y, Knecht D, Titus MA. Cell motility mediates tissue size regulation in Dictyostelium. J Muscle Res Cell Motil 2003; 23:809-15. [PMID: 12952079 DOI: 10.1023/a:1024487930787] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Little is known about how organisms regulate the size of multicellular structures. This review condenses some of the observations about how Dictyostelium regulates the size of fruiting bodies. Very large fruiting bodies tend to fall over, and one of the ways Dictyostelium cells prevent this is by breaking up the aggregation streams when there is an excessive number of cells in the stream. Developing cells simultaneously secrete and sense counting factor (CF), a 450 kDa complex of proteins. Diffusion calculations showed that as the number of cells in a stream or group increases, the local concentration of CF will increase, allowing the cells to sense the number of cells in the stream or group. Computer simulations predicted that a high level of CF could trigger stream breakup by decreasing cell-cell adhesion and/or increasing cell motility, effectively causing the stream to dissipate and begin to fall apart. The prediction that adhesion and motility affect group size is supported by observations that decreasing adhesion by adding antibodies that bind to adhesion protein causes the formation of smaller groups, while increasing adhesion by overexpressing adhesion proteins, or decreasing motility with drugs that disrupt actin function both cause the formation of larger groups. CF both decreases adhesion and increases motility. CF increases motility in part by increasing actin polymerization and myosin phosphorylation, and decreasing myosin polymerization. New observations using a fusion of a green fluorescent protein to a protein fragment that binds polymerized actin show that in live cells CF does not affect the distribution of polymerized actin. CF increases the levels of ABP-120, an actin-bundling protein, and new observations indicate that very low levels of CF cause an increase in levels of myoB, an unconventional myosin. Our current understanding of group size regulation in Dictyostelium is thus that motility plays a key role, and that to regulate group size cells regulate the expression of at least two proteins, as well as regulating the polymerization of both actin and myosin.
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Affiliation(s)
- Richard Gomer
- Howard Hughes Medical Institute, Department of Biochemistry and Cell Biology, MS-140, Rice University, 6100 S. Main Street, Houston, TX 77005-1892, USA.
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40
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Brock DA, Ehrenman K, Ammann R, Tang Y, Gomer RH. Two components of a secreted cell number-counting factor bind to cells and have opposing effects on cAMP signal transduction in Dictyostelium. J Biol Chem 2003; 278:52262-72. [PMID: 14557265 DOI: 10.1074/jbc.m309101200] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
A secreted 450-kDa complex of proteins called counting factor (CF) is part of a negative feedback loop that regulates the size of the groups formed by developing Dictyostelium cells. Two components of CF are countin and CF50. Both recombinant countin and recombinant CF50 decrease group size in Dictyostelium. countin- cells have a decreased cAMP-stimulated cAMP pulse, whereas recombinant countin potentiates the cAMP pulse. We find that CF50 cells have an increased cAMP pulse, whereas recombinant CF50 decreases the cAMP pulse, suggesting that countin and CF50 have opposite effects on cAMP signal transduction. In addition, countin and CF50 have opposite effects on cAMP-stimulated Erk2 activation. However, like recombinant countin, recombinant CF50 increases cell motility. We previously found that cells bind recombinant countin with a Hill coefficient of approximately 2, a KH of 60 pm, and approximately 53 sites/cell. We find here that cells also bind 125I-recombinant CF50, with a Hill coefficient of approximately 2, a KH of approximately 15 ng/ml (490 pm), and approximately 56 sites/cell. Countin and CF50 require each other's presence to affect group size, but the presence of countin is not necessary for CF50 to bind to cells, and CF50 is not necessary for countin to bind to cells. Our working hypothesis is that a signal transduction pathway activated by countin binding to cells modulates a signal transduction pathway activated by CF50 binding to cells and vice versa and that these two pathways can be distinguished by their effects on cAMP signal transduction.
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Affiliation(s)
- Debra A Brock
- Howard Hughes Medical Institute, Rice University, Houston, Texas 77005-1892, USA
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41
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Ehrenman K, Yang G, Hong WP, Gao T, Jang W, Brock DA, Hatton RD, Shoemaker JD, Gomer RH. Disruption of aldehyde reductase increases group size in dictyostelium. J Biol Chem 2003; 279:837-47. [PMID: 14551196 DOI: 10.1074/jbc.m310539200] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Developing Dictyostelium cells form structures containing approximately 20,000 cells. The size regulation mechanism involves a secreted counting factor (CF) repressing cytosolic glucose levels. Glucose or a glucose metabolite affects cell-cell adhesion and motility; these in turn affect whether a group stays together, loses cells, or even breaks up. NADPH-coupled aldehyde reductase reduces a wide variety of aldehydes to the corresponding alcohols, including converting glucose to sorbitol. The levels of this enzyme previously appeared to be regulated by CF. We find that disrupting alrA, the gene encoding aldehyde reductase, results in the loss of alrA mRNA and AlrA protein and a decrease in the ability of cell lysates to reduce both glyceraldehyde and glucose in an NADPH-coupled reaction. Counterintuitively, alrA- cells grow normally and have decreased glucose levels compared with parental cells. The alrA- cells form long unbroken streams and huge groups. Expression of AlrA in alrA- cells causes cells to form normal fruiting bodies, indicating that AlrA affects group size. alrA- cells have normal adhesion but a reduced motility, and computer simulations suggest that this could indeed result in the formation of large groups. alrA- cells secrete low levels of countin and CF50, two components of CF, and this could partially account for why alrA- cells form large groups. alrA- cells are responsive to CF and are partially responsive to recombinant countin and CF50, suggesting that disrupting alrA inhibits but does not completely block the CF signal transduction pathway. Gas chromatography/mass spectroscopy indicates that the concentrations of several metabolites are altered in alrA- cells, suggesting that the Dictyostelium aldehyde reductase affects several metabolic pathways in addition to converting glucose to sorbitol. Together, our data suggest that disrupting alrA affects CF secretion, causes many effects on cellular metabolism, and has a major effect on group size.
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Affiliation(s)
- Karen Ehrenman
- Howard Hughes Medical Institute and Department of Biochemistry and Cell Biology, Rice University, Houston, Texas 77005-1892, USA
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Kim DH, Sarbassov DD, Ali SM, Latek RR, Guntur KVP, Erdjument-Bromage H, Tempst P, Sabatini DM. GbetaL, a positive regulator of the rapamycin-sensitive pathway required for the nutrient-sensitive interaction between raptor and mTOR. Mol Cell 2003; 11:895-904. [PMID: 12718876 DOI: 10.1016/s1097-2765(03)00114-x] [Citation(s) in RCA: 714] [Impact Index Per Article: 34.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
mTOR and raptor are components of a signaling pathway that regulates mammalian cell growth in response to nutrients and growth factors. Here, we identify a member of this pathway, a protein named GbetaL that binds to the kinase domain of mTOR and stabilizes the interaction of raptor with mTOR. Like mTOR and raptor, GbetaL participates in nutrient- and growth factor-mediated signaling to S6K1, a downstream effector of mTOR, and in the control of cell size. The binding of GbetaL to mTOR strongly stimulates the kinase activity of mTOR toward S6K1 and 4E-BP1, an effect reversed by the stable interaction of raptor with mTOR. Interestingly, nutrients and rapamycin regulate the association between mTOR and raptor only in complexes that also contain GbetaL. Thus, we propose that the opposing effects on mTOR activity of the GbetaL- and raptor-mediated interactions regulate the mTOR pathway.
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Affiliation(s)
- Do-Hyung Kim
- Whitehead Institute for Biomedical Research and Department of Biology, Massachusetts Institute of Technology, Nine Cambridge Center, 02142, USA
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43
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Abstract
We studied the role of the adenylyl cyclase ACA in Dictyostelium discoideum chemotaxis and streaming. In this process, cells orient themselves in a head to tail fashion as they are migrating to form aggregates. We show that cells lacking ACA are capable of moving up a chemoattractant gradient, but are unable to stream. Imaging of ACA-YFP reveals plasma membrane labeling highly enriched at the uropod of polarized cells. This localization requires the actin cytoskeleton but is independent of the regulator CRAC and the effector PKA. A constitutively active mutant of ACA shows dramatically reduced uropod enrichment and has severe streaming defects. We propose that the asymmetric distribution of ACA provides a compartment from which cAMP is secreted to locally act as a chemoattractant, thereby providing a unique mechanism to amplify chemical gradients. This could represent a general mechanism that cells use to amplify chemotactic responses.
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Affiliation(s)
- Paul W Kriebel
- Laboratory of Cellular and Molecular Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, 37 Convent Drive, Building 37/Room 1E24, Bethesda, MD 20892, USA
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Jang W, Chiem B, Gomer RH. A secreted cell number counting factor represses intracellular glucose levels to regulate group size in dictyostelium. J Biol Chem 2002; 277:39202-8. [PMID: 12161440 DOI: 10.1074/jbc.m205635200] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Developing Dictyostelium cells form evenly sized groups of approximately 2 x 10(4) cells. A secreted 450-kDa protein complex called counting factor (CF) regulates group size by repressing cell-cell adhesion and myosin polymerization and by increasing cAMP-stimulated cAMP production, actin polymerization, and cell motility. We find that CF regulates group size in part by repressing internal glucose levels. Transformants lacking bioactive CF and wild-type cells with extracellular CF depleted by antibodies have high glucose levels, whereas transformants oversecreting CF have low glucose levels. A component of CF, countin, affects group size in a manner similar to CF, and a 1-min exposure of cells to countin decreases glucose levels. Adding 1 mm exogenous glucose negates the effect of high levels of extracellular CF on group size and mimics the effect of depleting CF on glucose levels, cell-cell adhesion, cAMP pulse size, actin polymerization, myosin assembly, and motility. These results suggest that glucose is a downstream component in part of the CF signaling pathway and may be relevant to the observed role of the insulin pathway in tissue size regulation in higher eukaryotes.
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Affiliation(s)
- Wonhee Jang
- Howard Hughes Medical Institute and the Department of Biochemistry and Cell Biology, Rice University, Houston, Texas 77005-1892, USA
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Gao T, Ehrenman K, Tang L, Leippe M, Brock DA, Gomer RH. Cells respond to and bind countin, a component of a multisubunit cell number counting factor. J Biol Chem 2002; 277:32596-605. [PMID: 12070154 DOI: 10.1074/jbc.m203075200] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
In Dictyostelium discoideum counting factor (CF), a secreted approximately 450-kDa complex of polypeptides, inhibits group and fruiting body size. When the gene encoding countin (a component of CF) was disrupted, cells formed large groups. We find that recombinant countin causes developing cells to form small groups, with an EC(50) of approximately 3 ng/ml, and affects cAMP signal transduction in the same manner as semipurified CF. Recombinant countin increases cell motility, decreases cell-cell adhesion, and regulates gene expression in a manner similar to the effect of CF. However, countin does not decrease adhesion or group size to the extent that semipurified CF does. A 1-min exposure of developing cells to countin causes an increase in F-actin polymerization and myosin phosphorylation and a decrease in myosin polymerization, suggesting that countin activates a rapid signal transduction pathway. (125)I-Labeled countin has countin bioactivity, and binding experiments suggest that vegetative and developing cells have approximately 53 cell-surface sites that bind countin with a K(D) of approximately 1.5 ng/ml or 60 pm. We hypothesize that countin regulates cell development through the same pathway as CF and that other proteins within the complex may modify the activity of countin and/or have independent size-regulating activities.
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Affiliation(s)
- Tong Gao
- Howard Hughes Medical Institute, Rice University, Houston, Texas 77005-1892, USA
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46
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Deery WJ, Gao T, Ammann R, Gomer RH. A single cell density-sensing factor stimulates distinct signal transduction pathways through two different receptors. J Biol Chem 2002; 277:31972-9. [PMID: 12070170 DOI: 10.1074/jbc.m204539200] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
In Dictyostelium discoideum, cell density is monitored by levels of a secreted protein, conditioned medium factor (CMF). CMFR1 is a putative CMF receptor necessary for CMF-induced G protein-independent accumulation of the SP70 prespore protein but not for CMF-induced G protein-dependent inositol 1,4,5-trisphosphate production. Using recombinant fragments of CMF, we find that stimulation of the inositol 1,4,5-trisphosphate pathway requires amino acids 170-180, whereas SP70 accumulation does not, corroborating a two-receptor model. Cells lacking CMFR1 do not aggregate, due to the lack of expression of several important early developmentally regulated genes, including gp80. Although many aspects of early developmental cAMP-stimulated signal transduction are mediated by CMF, CMFR1 is not essential for cAMP-stimulated cAMP and cGMP production or Ca(2+) uptake, suggesting the involvement of a second CMF receptor. Exogenous application of antibodies against either the region between a first and second or a second and third possible transmembrane domain of CMFR1 induces SP70 accumulation. Antibody- and CMF-induced gene expression can be inhibited by recombinant CMFR1 corresponding to the region between the first and third potential transmembrane domains, indicating that this region is extracellular and probably contains the CMF binding site. These observations support a model where a one- or two-transmembrane CMFR1 regulates gene expression and a G protein-coupled CMF receptor mediates cAR1 signal transduction.
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Affiliation(s)
- William J Deery
- Howard Hughes Medical Institute, Department of Biochemistry and Cell Biology, Rice University, Houston, Texas 77005-1892, USA
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Brock DA, Hatton RD, Giurgiutiu DV, Scott B, Ammann R, Gomer RH. The different components of a multisubunit cell number-counting factor have both unique and overlapping functions. Development 2002; 129:3657-68. [PMID: 12117815 DOI: 10.1242/dev.129.15.3657] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Dictyostelium aggregation streams break up into groups of 103 to 2×104 cells. The cells sense the number of cells in a stream or group by the level of a secreted counting factor (CF). CF is a complex of at least 5 polypeptides. When the gene encoding countin (one of the CF polypeptides) was disrupted, the cells could not sense each other’s presence, resulting in non-breaking streams that coalesced into abnormally large groups. To understand the function of the components of CF, we have isolated cDNA sequences encoding a second component of CF, CF50. CF50 is 30% identical to lysozyme (but has very little lysozyme activity) and contains distinctive serine-glycine motifs. Transformants with a disrupted cf50 gene, like countin– cells, form abnormally large groups. Addition of recombinant CF50 protein to developing cf50– cells rescues their phenotype by decreasing group size. Abnormalities seen in aggregating countin– cells (such as high cell-cell adhesion and low motility) are also observed in the cf50– cells. Western blot analysis of conditioned medium sieve column fractions showed that the CF50 protein is present in the same fraction as the 450 kDa CF complex. In the absence of CF50, secreted countin is degraded, suggesting that one function of CF50 may be to protect countin from degradation. However, unlike countin– cells, cf50– cells differentiate into an abnormally high percentage of cells expressing SP70 (a marker expressed in a subset of prespore cells), and this difference can be rescued by exposing cells to recombinant CF50. These observations indicate that unlike other known multisubunit factors, CF contains subunits with both overlapping and unique properties.
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Affiliation(s)
- Debra A Brock
- Howard Hughes Medical Institute, Rice University, 6100 South Main Street, Houston, TX 77005-1892, USA
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Tang L, Gao T, McCollum C, Jang W, Vicker MG, Ammann RR, Gomer RH. A cell number-counting factor regulates the cytoskeleton and cell motility in Dictyostelium. Proc Natl Acad Sci U S A 2002; 99:1371-6. [PMID: 11818526 PMCID: PMC122197 DOI: 10.1073/pnas.022516099] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Little is known about how a morphogenetic rearrangement of a tissue is affected by individual cells. Starving Dictyostelium discoideum cells aggregate to form dendritic streams, which then break up into groups of approximately 2 x 10(4) cells. Cell number is sensed at this developmental stage by using counting factor (CF), a secreted complex of polypeptides. A high extracellular concentration of CF indicates that there is a large number of cells, which then causes the aggregation stream to break up. Computer simulations indicated that stream breakup could be caused by CF decreasing cell-cell adhesion and/or increasing cell motility, and we observed that CF does indeed decrease cell-cell adhesion. We find here that CF increases cell motility. In Dictyostelium, motility is mediated by actin and myosin. CF increases the amounts of polymerized actin and the ABP-120 actin-crosslinking protein. Partially inhibiting motility by using drugs that interfere with actin polymerization reduces stream dissipation, resulting in fewer stream breaks and thus larger groups. CF also potentiates the phosphorylation and redistribution of myosin while repressing its basal level of assembly. The computer simulations indicated that a narrower distribution of group sizes results when a secreted factor modulates both adhesion and motility. CF thus seems to induce the morphogenesis of streams into evenly sized groups by increasing actin polymerization, ABP-120 levels, and myosin phosphorylation and decreasing adhesion and myosin polymerization.
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Affiliation(s)
- Lei Tang
- Department of Biochemistry and Cell Biology, MS-140, Rice University, Houston, TX 77005-1892, USA
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49
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Tang L, Ammann R, Gao T, Gomer RH. A cell number-counting factor regulates group size in Dictyostelium by differentially modulating cAMP-induced cAMP and cGMP pulse sizes. J Biol Chem 2001; 276:27663-9. [PMID: 11371560 DOI: 10.1074/jbc.m102205200] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
A secreted counting factor (CF), regulates the size of Dictyostelium discoideum fruiting bodies in part by regulating cell-cell adhesion. Aggregation and the expression of adhesion molecules are mediated by relayed pulses of cAMP. Cells also respond to cAMP with a short cGMP pulse. We find that CF slowly down-regulates the cAMP-induced cGMP pulse by inhibiting guanylyl cyclase activity. A 1-min exposure of cells to purified CF increases the cAMP-induced cAMP pulse. CF does not affect the cAMP receptor or its interaction with its associated G proteins or the translocation of the cytosolic regulator of adenylyl cyclase to the membrane in response to cAMP. Pulsing streaming wild-type cells with a high concentration of cAMP results in the formation of small groups, whereas reducing cAMP pulse size with exogenous cAMP phosphodiesterase during stream formation causes cells to form large groups. Altering the extracellular cAMP pulse size does not phenocopy the effects of CF on the cAMP-induced cGMP pulse size or cell-cell adhesion, indicating that CF does not regulate cGMP pulses and adhesion via CF's effects on cAMP pulses. The results suggest that regulating cell-cell adhesion, the cGMP pulse size, or the cAMP pulse size can control group size and that CF regulates all three of these independently.
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Affiliation(s)
- L Tang
- Howard Hughes Medical Institute and the Department of Biochemistry and Cell Biology, Rice University, Houston, Texas 77005-1892, USA
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