1
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Brinkley DM, Smith KC, Fink EC, Kwen W, Yoo NH, West Z, Sullivan NL, Farthing AS, Hale VA, Goutte C. Notch signaling without the APH-2/nicastrin subunit of gamma secretase in Caenorhabditis elegans germline stem cells. Genetics 2024; 227:iyae076. [PMID: 38717968 DOI: 10.1093/genetics/iyae076] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2024] [Accepted: 05/01/2024] [Indexed: 07/09/2024] Open
Abstract
The final step in Notch signaling activation is the transmembrane cleavage of Notch receptor by γ secretase. Thus far, genetic and biochemical evidence indicates that four subunits are essential for γ secretase activity in vivo: presenilin (the catalytic core), APH-1, PEN-2, and APH-2/nicastrin. Although some γ secretase activity has been detected in APH-2/nicastrin-deficient mammalian cell lines, the lack of biological relevance for this activity has left the quaternary γ secretase model unchallenged. Here, we provide the first example of in vivo Notch signal transduction without APH-2/nicastrin. The surprising dispensability of APH-2/nicastrin is observed in Caenorhabditis elegans germline stem cells (GSCs) and contrasts with its essential role in previously described C. elegans Notch signaling events. Depletion of GLP-1/Notch, presenilin, APH-1, or PEN-2 causes a striking loss of GSCs. In contrast, aph-2/nicastrin mutants maintain GSCs and exhibit robust and localized expression of the downstream Notch target sygl-1. Interestingly, APH-2/nicastrin is normally expressed in GSCs and becomes essential under conditions of compromised Notch function. Further insight is provided by reconstituting the C. elegans γ secretase complex in yeast, where we find that APH-2/nicastrin increases but is not essential for γ secretase activity. Together, our results are most consistent with a revised model of γ secretase in which the APH-2/nicastrin subunit has a modulatory, rather than obligatory role. We propose that a trimeric presenilin-APH-1-PEN-2 γ secretase complex can provide a low level of γ secretase activity, and that cellular context determines whether or not APH-2/nicastrin is essential for effective Notch signal transduction.
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Affiliation(s)
- David M Brinkley
- Program in Biochemistry and Biophysics, Amherst College, Amherst, MA 01002, USA
| | - Karen C Smith
- Department of Biology, Amherst College, Amherst, MA 01002, USA
| | - Emma C Fink
- Department of Biology, Amherst College, Amherst, MA 01002, USA
| | - Woohyun Kwen
- Department of Biology, Amherst College, Amherst, MA 01002, USA
| | - Nina H Yoo
- Department of Biology, Amherst College, Amherst, MA 01002, USA
| | - Zachary West
- Department of Biology, Amherst College, Amherst, MA 01002, USA
| | - Nora L Sullivan
- Department of Biology, Amherst College, Amherst, MA 01002, USA
| | - Alex S Farthing
- Program in Biochemistry and Biophysics, Amherst College, Amherst, MA 01002, USA
| | - Valerie A Hale
- Department of Biology, Amherst College, Amherst, MA 01002, USA
| | - Caroline Goutte
- Program in Biochemistry and Biophysics, Amherst College, Amherst, MA 01002, USA
- Department of Biology, Amherst College, Amherst, MA 01002, USA
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2
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Amran A, Pigatto L, Farley J, Godini R, Pocock R, Gopal S. The matrisome landscape controlling in vivo germ cell fates. Nat Commun 2024; 15:4200. [PMID: 38760342 PMCID: PMC11101451 DOI: 10.1038/s41467-024-48283-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2023] [Accepted: 04/26/2024] [Indexed: 05/19/2024] Open
Abstract
The developmental fate of cells is regulated by intrinsic factors and the extracellular environment. The extracellular matrix (matrisome) delivers chemical and mechanical cues that can modify cellular development. However, comprehensive understanding of how matrisome factors control cells in vivo is lacking. Here we show that specific matrisome factors act individually and collectively to control germ cell development. Surveying development of undifferentiated germline stem cells through to mature oocytes in the Caenorhabditis elegans germ line enabled holistic functional analysis of 443 conserved matrisome-coding genes. Using high-content imaging, 3D reconstruction, and cell behavior analysis, we identify 321 matrisome genes that impact germ cell development, the majority of which (>80%) are undescribed. Our analysis identifies key matrisome networks acting autonomously and non-autonomously to coordinate germ cell behavior. Further, our results demonstrate that germ cell development requires continual remodeling of the matrisome landscape. Together, this study provides a comprehensive platform for deciphering how extracellular signaling controls cellular development and anticipate this will establish new opportunities for manipulating cell fates.
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Affiliation(s)
- Aqilah Amran
- Department of Experimental Medical Science, Lund University, Lund, Sweden
- Lund Stem Cell Center, Lund University, Lund, Sweden
- Lund Cancer Center, Lund University, Lund, Sweden
- Development and Stem Cells Program, Monash Biomedicine Discovery Institute. Department of Anatomy and Developmental Biology, Monash University, Melbourne, VIC, Australia
| | - Lara Pigatto
- Department of Experimental Medical Science, Lund University, Lund, Sweden
- Lund Stem Cell Center, Lund University, Lund, Sweden
- Lund Cancer Center, Lund University, Lund, Sweden
- Development and Stem Cells Program, Monash Biomedicine Discovery Institute. Department of Anatomy and Developmental Biology, Monash University, Melbourne, VIC, Australia
| | - Johanna Farley
- Department of Experimental Medical Science, Lund University, Lund, Sweden
- Lund Stem Cell Center, Lund University, Lund, Sweden
- Lund Cancer Center, Lund University, Lund, Sweden
| | - Rasoul Godini
- Development and Stem Cells Program, Monash Biomedicine Discovery Institute. Department of Anatomy and Developmental Biology, Monash University, Melbourne, VIC, Australia
| | - Roger Pocock
- Development and Stem Cells Program, Monash Biomedicine Discovery Institute. Department of Anatomy and Developmental Biology, Monash University, Melbourne, VIC, Australia.
| | - Sandeep Gopal
- Department of Experimental Medical Science, Lund University, Lund, Sweden.
- Lund Stem Cell Center, Lund University, Lund, Sweden.
- Lund Cancer Center, Lund University, Lund, Sweden.
- Development and Stem Cells Program, Monash Biomedicine Discovery Institute. Department of Anatomy and Developmental Biology, Monash University, Melbourne, VIC, Australia.
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3
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Aprison EZ, Dzitoyeva S, Ruvinsky I. The roles of TGFβ and serotonin signaling in regulating proliferation of oocyte precursors and germline aging. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.05.08.593208. [PMID: 38766220 PMCID: PMC11100717 DOI: 10.1101/2024.05.08.593208] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2024]
Abstract
The decline of oocyte quality in aging but otherwise relatively healthy individuals compels a search for underlying mechanisms. Building upon a finding that exposure to male pheromone ascr#10 improves oocyte quality in C. elegans, we uncovered a regulatory cascade that promotes proliferation of oocyte precursors in adults and regulates oocyte quality. We found that the male pheromone promotes proliferation of oocyte precursors by upregulating LAG-2, a ligand of the Notch-like pathway in the germline stem cell niche. LAG-2 is upregulated by a TGFβ-like ligand DAF-7 revealing similarity of regulatory mechanisms that promote germline proliferation in adults and larvae. A serotonin circuit that also regulates food search and consumption upregulates DAF-7 specifically in adults. The serotonin/DAF-7 signaling promotes germline expansion to compensate for oocyte expenditure which is increased by the male pheromone. Finally, we show that the earliest events in reproductive aging may be due to declining expression of LAG-2 and DAF-7. Our findings highlight neuronal signals that promote germline proliferation in response to the environment and argue that deteriorating oocyte quality may be due to reduced neuronal expression of key germline regulators.
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Affiliation(s)
- Erin Z. Aprison
- Department of Molecular Biosciences, Northwestern University, Evanston, IL 60208, USA
| | - Svetlana Dzitoyeva
- Department of Molecular Biosciences, Northwestern University, Evanston, IL 60208, USA
| | - Ilya Ruvinsky
- Department of Molecular Biosciences, Northwestern University, Evanston, IL 60208, USA
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4
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Urman MA, John NS, Jung T, Lee C. Aging disrupts spatiotemporal regulation of germline stem cells and niche integrity. Biol Open 2024; 13:bio060261. [PMID: 38156664 PMCID: PMC10810562 DOI: 10.1242/bio.060261] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2023] [Accepted: 12/13/2023] [Indexed: 01/03/2024] Open
Abstract
A major factor driving stem cell decline is stem cell niche aging, but its molecular mechanism remains elusive. We use the Caenorhabditis elegans distal tip cell (DTC), the mesenchymal niche that employs Notch signaling to regulate germline stem cells (GSCs), as an in vivo niche aging model and delineate the molecular details of the DTC/niche aging process. Here, we demonstrate that a drastic decrease in C. elegans germline fecundity, which begins even in early adulthood, is mainly due to an age-induced disruption in spatial regulation of Notch-dependent transcription in the germline combined with a moderate reduction in Notch transcription at both tissue and cellular levels. Consequently, the Notch-responsive GSC pool shifts from the distal end of the gonad to a more proximal region, disrupting the distal-to-proximal germline polarity. We find that this GSC pool shift is due to a dislocation of the DTC/niche nucleus, which is associated with age-induced changes in the structure and morphology of the DTC/niche. Our findings reveal a critical link between physiological changes in the aging niche, their consequences in stem cell regulation, and germline tissue functions.
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Affiliation(s)
- Michelle A. Urman
- Department of Biological Sciences, University at Albany, State University of New York, Albany, NY, 12222, USA
- The RNA Institute, University at Albany, State University of New York, Albany, NY, 12222, USA
| | - Nimmy S. John
- Department of Biological Sciences, University at Albany, State University of New York, Albany, NY, 12222, USA
- The RNA Institute, University at Albany, State University of New York, Albany, NY, 12222, USA
| | - Tyler Jung
- Department of Biological Sciences, University at Albany, State University of New York, Albany, NY, 12222, USA
| | - ChangHwan Lee
- Department of Biological Sciences, University at Albany, State University of New York, Albany, NY, 12222, USA
- The RNA Institute, University at Albany, State University of New York, Albany, NY, 12222, USA
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5
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Davis GM, Hipwell H, Boag PR. Oogenesis in Caenorhabditis elegans. Sex Dev 2023; 17:73-83. [PMID: 37232019 PMCID: PMC10659005 DOI: 10.1159/000531019] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2022] [Accepted: 05/01/2023] [Indexed: 05/27/2023] Open
Abstract
BACKGROUND The nematode, Caenorhabditis elegans has proven itself as a valuable model for investigating metazoan biology. C. elegans have a transparent body, an invariant cell lineage, and a high level of genetic conservation which makes it a desirable model organism. Although used to elucidate many aspects of somatic biology, a distinct advantage of C. elegans is its well annotated germline which allows all aspects of oogenesis to be observed in real time within a single animal. C. elegans hermaphrodites have two U-shaped gonad arms which produce their own sperm that is later stored to fertilise their own oocytes. These two germlines take up much of the internal space of each animal and germ cells are therefore the most abundant cell present within each animal. This feature and the genetic phenotypes observed for mutant worm gonads have allowed many novel findings that established our early understanding of germ cell dynamics. The mutant phenotypes also allowed key features of meiosis and germ cell maturation to be unveiled. SUMMARY This review will focus on the key aspects that make C. elegans an outstanding model for exploring each feature of oogenesis. This will include the fundamental steps associated with germline function and germ cell maturation and will be of use for those interested in exploring reproductive metazoan biology. KEY MESSAGES Since germ cell biology is highly conserved in animals, much can be gained from study of a simple metazoan like C. elegans. Past findings have enhanced understanding on topics that would be more laborious or challenging in more complex animal models.
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Affiliation(s)
- Gregory M. Davis
- Institute of Innovation, Science and Sustainability, Federation University, Churchill, VIC, Australia
| | - Hayleigh Hipwell
- Department of Biochemistry and Molecular Biology, Development and Stem Cells Program, Monash Biomedicine Discovery Institute, Clayton, VIC, Australia
| | - Peter R. Boag
- Department of Biochemistry and Molecular Biology, Development and Stem Cells Program, Monash Biomedicine Discovery Institute, Clayton, VIC, Australia
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6
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Crittenden SL, Seidel HS, Kimble J. Analysis of the C. elegans Germline Stem Cell Pool. Methods Mol Biol 2023; 2677:1-36. [PMID: 37464233 DOI: 10.1007/978-1-0716-3259-8_1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/20/2023]
Abstract
The Caenorhabditis elegans germline is an excellent model for studying the genetic and molecular regulation of stem cell self-renewal and progression of cells from a stem cell state to a differentiated state. The germline tissue is organized in an assembly line with the germline stem cell (GSC) pool at one end and differentiated gametes at the other. A simple mesenchymal niche caps the GSC pool and maintains GSCs in an undifferentiated state by signaling through the conserved Notch pathway. Notch signaling activates transcription of the key GSC regulators lst-1 and sygl-1 proteins in a gradient through the GSC pool. LST-1 and SYGL-1 proteins work with PUF RNA regulators in a self-renewal hub to maintain the GSC pool. In this chapter, we present methods for characterizing the C. elegans GSC pool and early stages of germ cell differentiation. The methods include examination of germlines in living and fixed worms, cell cycle analysis, and analysis of markers. We also discuss assays to separate mutant phenotypes that affect the stem cell vs. differentiation decision from those that affect germ cell processes more generally.
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Affiliation(s)
- Sarah L Crittenden
- Department of Biochemistry, University of Wisconsin-Madison, Madison, WI, USA.
| | - Hannah S Seidel
- Department of Biology, Eastern Michigan University, Ypsilanti, MI, USA
| | - Judith Kimble
- Department of Biochemistry, University of Wisconsin-Madison, Madison, WI, USA
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7
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Valet M, Narbonne P. Formation of benign tumors by stem cell deregulation. PLoS Genet 2022; 18:e1010434. [PMID: 36301803 PMCID: PMC9612571 DOI: 10.1371/journal.pgen.1010434] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
Within living organisms, stem cells respond to various cues, including to niche signals and growth factors. Niche signals originate from the stem cell's microenvironment and promote the undifferentiated state by preventing differentiation, allowing for stem cell self-renewal. On the other hand, growth factors promote stem cell growth and proliferation, while their sources comprise of a systemic input reflecting the animal's nutritional and metabolic status, and a localized, homeostatic feedback signal from the tissue that the stem cells serve. That homeostatic signal prevents unnecessary stem cell proliferation when the corresponding differentiated tissues already have optimal cell contents. Here, we recapitulate progresses made in our understanding of in vivo stem cell regulation, largely using simple models, and draw the conclusion that 2 types of stem cell deregulations can provoke the formation of benign tumors. Namely, constitutive niche signaling promotes the formation of undifferentiated "stem cell" tumors, while defective homeostatic signaling leads to the formation of differentiated tumors. Finally, we provide evidence that these general principles may be conserved in mammals and as such, may underlie benign tumor formation in humans, while benign tumors can evolve into cancer.
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Affiliation(s)
- Matthieu Valet
- Département de biologie médicale, Université du Québec à Trois-Rivières, Trois-Rivières, Québec, Canada
| | - Patrick Narbonne
- Département de biologie médicale, Université du Québec à Trois-Rivières, Trois-Rivières, Québec, Canada
- * E-mail:
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8
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Tolkin T, Mohammad A, Starich TA, Nguyen KCQ, Hall DH, Schedl T, Hubbard EJA, Greenstein D. Innexin function dictates the spatial relationship between distal somatic cells in the Caenorhabditis elegans gonad without impacting the germline stem cell pool. eLife 2022; 11:e74955. [PMID: 36098634 PMCID: PMC9473689 DOI: 10.7554/elife.74955] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2021] [Accepted: 08/08/2022] [Indexed: 12/01/2022] Open
Abstract
Gap-junctional signaling mediates myriad cellular interactions in metazoans. Yet, how gap junctions control the positioning of cells in organs is not well understood. Innexins compose gap junctions in invertebrates and affect organ architecture. Here, we investigate the roles of gap-junctions in controlling distal somatic gonad architecture and its relationship to underlying germline stem cells in Caenorhabditis elegans. We show that a reduction of soma-germline gap-junctional activity causes displacement of distal sheath cells (Sh1) towards the distal end of the gonad. We confirm, by live imaging, transmission electron microscopy, and antibody staining, that bare regions-lacking somatic gonadal cell coverage of germ cells-are present between the distal tip cell (DTC) and Sh1, and we show that an innexin fusion protein used in a prior study encodes an antimorphic gap junction subunit that mispositions Sh1. We determine that, contrary to the model put forth in the prior study based on this fusion protein, Sh1 mispositioning does not markedly alter the position of the borders of the stem cell pool nor of the progenitor cell pool. Together, these results demonstrate that gap junctions can control the position of Sh1, but that Sh1 position is neither relevant for GLP-1/Notch signaling nor for the exit of germ cells from the stem cell pool.
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Affiliation(s)
- Theadora Tolkin
- Kimmel Center for Biology and Medicine at the Skirball Institute, NYU Grossman School of MedicineNew YorkUnited States
- Department of Cell Biology, NYU Grossman School of MedicineNew YorkUnited States
| | - Ariz Mohammad
- Department of Genetics, Washington University School of MedicineSt. LouisUnited States
| | - Todd A Starich
- Department of Genetics, Cell Biology and Development, University of MinnesotaMinneapolisUnited States
| | - Ken CQ Nguyen
- Department of Neuroscience, Albert Einstein College of MedicineThe BronxUnited States
| | - David H Hall
- Department of Neuroscience, Albert Einstein College of MedicineThe BronxUnited States
| | - Tim Schedl
- Department of Genetics, Washington University School of MedicineSt. LouisUnited States
| | - E Jane Albert Hubbard
- Kimmel Center for Biology and Medicine at the Skirball Institute, NYU Grossman School of MedicineNew YorkUnited States
- Department of Cell Biology, NYU Grossman School of MedicineNew YorkUnited States
- Department of Pathology, NYU Grossman School of MedicineNew YorkUnited States
| | - David Greenstein
- Department of Genetics, Cell Biology and Development, University of MinnesotaMinneapolisUnited States
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9
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Marchal I, Tursun B. Induced Neurons From Germ Cells in Caenorhabditis elegans. Front Neurosci 2021; 15:771687. [PMID: 34924939 PMCID: PMC8678065 DOI: 10.3389/fnins.2021.771687] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2021] [Accepted: 11/08/2021] [Indexed: 11/28/2022] Open
Abstract
Cell fate conversion by the forced overexpression of transcription factors (TFs) is a process known as reprogramming. It leads to de-differentiation or trans-differentiation of mature cells, which could then be used for regenerative medicine applications to replenish patients suffering from, e.g., neurodegenerative diseases, with healthy neurons. However, TF-induced reprogramming is often restricted due to cell fate safeguarding mechanisms, which require a better understanding to increase reprogramming efficiency and achieve higher fidelity. The germline of the nematode Caenorhabditis elegans has been a powerful model to investigate the impediments of generating neurons from germ cells by reprogramming. A number of conserved factors have been identified that act as a barrier for TF-induced direct reprogramming of germ cells to neurons. In this review, we will first summarize our current knowledge regarding cell fate safeguarding mechanisms in the germline. Then, we will focus on the molecular mechanisms underlying neuronal induction from germ cells upon TF-mediated reprogramming. We will shortly discuss the specific characteristics that might make germ cells especially fit to change cellular fate and become neurons. For future perspectives, we will look at the potential of C. elegans research in advancing our knowledge of the mechanisms that regulate cellular identity, and what implications this has for therapeutic approaches such as regenerative medicine.
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Affiliation(s)
- Iris Marchal
- Berlin Institute for Medical Systems Biology, Berlin, Germany
- Max Delbrück Center for Molecular Medicine in the Helmholtz Association, Berlin, Germany
| | - Baris Tursun
- Berlin Institute for Medical Systems Biology, Berlin, Germany
- Max Delbrück Center for Molecular Medicine in the Helmholtz Association, Berlin, Germany
- Department of Biology, Institute of Zoology, University of Hamburg, Hamburg, Germany
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10
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Dagar S, Pushpa K, Pathak D, Samaddar S, Saxena A, Banerjee S, Mylavarapu SVS. Nucleolin regulates 14-3-3ζ mRNA and promotes cofilin phosphorylation to induce tunneling nanotube formation. FASEB J 2021; 35:e21199. [PMID: 33222276 DOI: 10.1096/fj.202001152r] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2020] [Revised: 10/19/2020] [Accepted: 11/02/2020] [Indexed: 12/17/2023]
Abstract
Tunneling nanotubes (TNTs) mediate intercellular communication between animal cells in health and disease, but the mechanisms of their biogenesis and function are poorly understood. Here we report that the RNA-binding protein (RBP) nucleolin, which interacts with the known TNT-inducing protein MSec, is essential for TNT formation in mammalian cells. Nucleolin, through its RNA-binding domains (RBDs), binds to and maintains the cytosolic levels of 14-3-3ζ mRNA, and is, therefore, required for TNT formation. A specific region of the 3'-untranslated region (UTR) of the 14-3-3ζ mRNA is likely to be involved in its regulation by nucleolin. Functional complementation experiments suggest that nucleolin and 14-3-3ζ form a linear signaling axis that promotes the phosphorylation and inactivation of the F-actin depolymerization factor cofilin to induce TNT formation. MSec also similarly inactivates cofilin, but potentiates TNT formation independent of the nucleolin-14-3-3ζ axis, despite biochemically interacting with both proteins. We show that 14-3-3ζ and nucleolin are required for the formation of TNTs between primary mouse neurons and astrocytes and in multiple other mammalian cell types. We also report that the Caenorhabditis elegans orthologs of 14-3-3ζ and MSec regulate the size and architecture of the TNT-like cellular protrusions of the distal tip cell (DTC), the germline stem cell niche in the gonad. Our study demonstrates a novel and potentially conserved mRNA-guided mechanism of TNT formation through the maintenance of cellular 14-3-3ζ mRNA levels by the RBP nucleolin.
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Affiliation(s)
- Sunayana Dagar
- Laboratory of Cellular Dynamics, Regional Centre for Biotechnology, NCR Biotech Science Cluster, Faridabad, India
- Affiliated to the Kalinga Institute of Industrial Technology, Bhubaneswar, India
| | - Kumari Pushpa
- Laboratory of Cellular Dynamics, Regional Centre for Biotechnology, NCR Biotech Science Cluster, Faridabad, India
| | - Diksha Pathak
- Laboratory of Cellular Dynamics, Regional Centre for Biotechnology, NCR Biotech Science Cluster, Faridabad, India
| | | | - Anjana Saxena
- Biology Department, Brooklyn College AND Biology and Biochemistry Programs, Graduate Center, CUNY, New York, NY, USA
| | | | - Sivaram V S Mylavarapu
- Laboratory of Cellular Dynamics, Regional Centre for Biotechnology, NCR Biotech Science Cluster, Faridabad, India
- Affiliated to the Kalinga Institute of Industrial Technology, Bhubaneswar, India
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11
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Rikitake M, Matsuda A, Murata D, Dejima K, Nomura KH, Abbott KL, Mitani S, Nomura K. Analysis of GPI-anchored proteins involved in germline stem cell proliferation in the Caenorhabditis elegans germline stem cell niche. J Biochem 2020; 168:589-602. [PMID: 32844210 DOI: 10.1093/jb/mvaa075] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2020] [Accepted: 06/24/2020] [Indexed: 11/14/2022] Open
Abstract
Stem cells divide and undergo self-renewal depending on the signals received from the stem cell niche. This phenomenon is indispensable to maintain tissues and organs in individuals. However, not all the molecular factors and mechanisms of self-renewal are known. In our previous study, we reported that glycosylphosphatidylinositol (GPI)-anchored proteins (GPI-APs) synthesized in the distal tip cells (DTCs; the stem cell niche) are essential for germline stem cell proliferation in Caenorhabditis elegans. Here, we characterized the GPI-APs required for proliferation. We selected and verified the candidate GPI-APs synthesized in DTCs by RNA interference screening and found that F57F4.3 (GFI-1), F57F4.4 and F54E2.1 are necessary for germline proliferation. These proteins are likely involved in the same pathway for proliferation and activated by the transcription factor PQM-1. We further provided evidence suggesting that these GPI-APs act through fatty acid remodelling of the GPI anchor, which is essential for association with lipid rafts. These findings demonstrated that GPI-APs, particularly F57F4.3/4 and F54E2.1, synthesized in the germline stem cell niche are located in lipid rafts and involved in promoting germline stem cell proliferation in C. elegans. The findings may thus shed light on the mechanisms by which GPI-APs regulate stem cell self-renewal.
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Affiliation(s)
- Marika Rikitake
- Department of Systems Life Sciences, Kyushu University Graduate School, Fukuoka 819-0395, Japan
| | - Ayako Matsuda
- Department of Systems Life Sciences, Kyushu University Graduate School, Fukuoka 819-0395, Japan
| | - Daisuke Murata
- Department of Systems Life Sciences, Kyushu University Graduate School, Fukuoka 819-0395, Japan.,CREST (JST), Saitama 332-0012, Japan.,Department of Cell Biology, Johns Hopkins University School of Medicine, 725 N. Wolfe Street, 113 Hunterian, Baltimore, MD 21205, USA
| | - Katsufumi Dejima
- CREST (JST), Saitama 332-0012, Japan.,Department of Physiology, Tokyo Women's Medical University School of Medicine, Tokyo 162-8666, Japan
| | - Kazuko H Nomura
- CREST (JST), Saitama 332-0012, Japan.,Department of Biology, Kyushu University, Fukuoka 819-0395, Japan
| | - Karen L Abbott
- Department of Biochemistry and Molecular Biology, The University of Oklahoma Health Sciences Center, 9 Stephenson Cancer Center, Oklahoma City, OK 73104, USA.,SL Young Biomedical Research Center, 975 NE 10th St., BRC 409 North lab/411A Office, Little Rock, AR 72205, USA
| | - Shohei Mitani
- CREST (JST), Saitama 332-0012, Japan.,Department of Physiology, Tokyo Women's Medical University School of Medicine, Tokyo 162-8666, Japan
| | - Kazuya Nomura
- CREST (JST), Saitama 332-0012, Japan.,Department of Biology, Kyushu University, Fukuoka 819-0395, Japan.,Department of Medical Biochemistry, Kurume University School of Medicine, 67 Asahi-machi, Kurume, Fukuoka 830-0011, Japan
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12
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Gorgoń S, Świątek P. The apical cell - An enigmatic somatic cell in leech ovaries - Structure and putative functions. Dev Biol 2020; 469:111-124. [PMID: 33141038 DOI: 10.1016/j.ydbio.2020.10.004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2020] [Revised: 09/27/2020] [Accepted: 10/10/2020] [Indexed: 11/16/2022]
Abstract
Although somatic cells play an integral role in animal gametogenesis, their organization and function are usually poorly characterized, especially in non-model systems. One such example is a peculiar cell found in leech ovaries - the apical cell (AC). A single AC can be found at the apical tip of each ovary cord, the functional unit of leech ovaries, where it is surrounded by other somatic and germline cells. The AC is easily distinguished due to its enormous size and its numerous long cytoplasmic projections that penetrate the space between neighboring cells. It is also characterized by a prominent accumulation of mitochondria, Golgi complexes and electron-dense vesicles. ACs are also enriched in cytoskeleton, mainly in form of intermediate filaments. Additionally, the AC is connected to neighboring cells via junctions that structurally resemble hemidesmosomes. In spite of numerous descriptive data about the AC, its functions remain poorly understood. Its suggested functions include a role in forming skeleton for the germline cells, and a role in defining a niche for germline stem cells. The latter is more speculative, since germline stem cells have not been identified in leech ovaries. Somatic cells with similar morphological properties to those of the AC have been found in gonads of nematodes - the distal tip cell - and in insects - Verson's cell, hub cells and cap cells. In the present article we summarize information about the AC structure and its putative functions. AC is compared with other well-described somatic cells with potentially similar roles in gametogenesis.
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Affiliation(s)
- Szymon Gorgoń
- University of Silesia in Katowice, Faculty of Natural Sciences, Institute of Biology, Biotechnology and Environmental Protection, Bankowa 9, 40-032, Katowice, Poland; Umeå University, Department of Surgical and Perioperative Sciences, Surgery, 901 87, Umeå, Sweden.
| | - Piotr Świątek
- University of Silesia in Katowice, Faculty of Natural Sciences, Institute of Biology, Biotechnology and Environmental Protection, Bankowa 9, 40-032, Katowice, Poland
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13
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Molecular basis of reproductive senescence: insights from model organisms. J Assist Reprod Genet 2020; 38:17-32. [PMID: 33006069 DOI: 10.1007/s10815-020-01959-4] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2020] [Accepted: 09/25/2020] [Indexed: 12/14/2022] Open
Abstract
PURPOSE Reproductive decline due to parental age has become a major barrier to fertility as couples have delayed having offspring into their thirties and forties. Advanced parental age is also associated with increased incidence of neurological and cardiovascular disease in offspring. Thus, elucidating the etiology of reproductive decline is of clinical importance. METHODS Deciphering the underlying processes that drive reproductive decline is particularly challenging in women in whom a discrete oocyte pool is established during embryogenesis and may remain dormant for tens of years. Instead, our understanding of the processes that drive reproductive senescence has emerged from studies in model organisms, both vertebrate and invertebrate, that are the focus of this literature review. CONCLUSIONS Studies of reproductive aging in model organisms not only have revealed the detrimental cellular changes that occur with age but also are helping identify major regulator proteins controlling them. Here, we discuss what we have learned from model organisms with respect to the molecular mechanisms that maintain both genome integrity and oocyte quality.
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14
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Cinquin A, Cinquin O. More than just a pool. eLife 2020; 9:61397. [PMID: 32915135 PMCID: PMC7486116 DOI: 10.7554/elife.61397] [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: 09/02/2020] [Accepted: 09/02/2020] [Indexed: 11/13/2022] Open
Abstract
An intricate stem cell niche boundary formed by finger-like extensions generates asymmetry in stem cell divisions.
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Affiliation(s)
- Amanda Cinquin
- Department of Developmental and Cell Biology, Center for Complex Biological Systems, University of California, Irvine, Irvine, United States
| | - Olivier Cinquin
- Department of Developmental and Cell Biology, Center for Complex Biological Systems, University of California, Irvine, Irvine, United States
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15
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Gordon K. Recent Advances in the Genetic, Anatomical, and Environmental Regulation of the C. elegans Germ Line Progenitor Zone. J Dev Biol 2020; 8:E14. [PMID: 32707774 PMCID: PMC7559772 DOI: 10.3390/jdb8030014] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2020] [Revised: 07/13/2020] [Accepted: 07/15/2020] [Indexed: 12/16/2022] Open
Abstract
The C. elegans germ line and its gonadal support cells are well studied from a developmental genetics standpoint and have revealed many foundational principles of stem cell niche biology. Among these are the observations that a niche-like cell supports a self-renewing stem cell population with multipotential, differentiating daughter cells. While genetic features that distinguish stem-like cells from their differentiating progeny have been defined, the mechanisms that structure these populations in the germ line have yet to be explained. The spatial restriction of Notch activation has emerged as an important genetic principle acting in the distal germ line. Synthesizing recent findings, I present a model in which the germ stem cell population of the C. elegans adult hermaphrodite can be recognized as two distinct anatomical and genetic populations. This review describes the recent progress that has been made in characterizing the undifferentiated germ cells and gonad anatomy, and presents open questions in the field and new directions for research to pursue.
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Affiliation(s)
- Kacy Gordon
- Department of Biology, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
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16
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Gordon KL, Zussman JW, Li X, Miller C, Sherwood DR. Stem cell niche exit in C. elegans via orientation and segregation of daughter cells by a cryptic cell outside the niche. eLife 2020; 9:e56383. [PMID: 32692313 PMCID: PMC7467730 DOI: 10.7554/elife.56383] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2020] [Accepted: 07/17/2020] [Indexed: 12/17/2022] Open
Abstract
Stem cells reside in and rely upon their niche to maintain stemness but must balance self-renewal with the production of daughters that leave the niche to differentiate. We discovered a mechanism of stem cell niche exit in the canonical C. elegans distal tip cell (DTC) germ stem cell niche mediated by previously unobserved, thin, membranous protrusions of the adjacent somatic gonad cell pair (Sh1). A disproportionate number of germ cell divisions were observed at the DTC-Sh1 interface. Stem-like and differentiating cell fates segregated across this boundary. Spindles polarized, pairs of daughter cells oriented between the DTC and Sh1, and Sh1 grew over the Sh1-facing daughter. Impeding Sh1 growth by RNAi to cofilin and Arp2/3 perturbed the DTC-Sh1 interface, reduced germ cell proliferation, and shifted a differentiation marker. Because Sh1 membrane protrusions eluded detection for decades, it is possible that similar structures actively regulate niche exit in other systems.
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Affiliation(s)
- Kacy L Gordon
- Department of Biology, The University of North Carolina at Chapel HillChapel HillUnited States
| | - Jay W Zussman
- Department of Biology, Duke UniversityDurhamUnited States
| | - Xin Li
- Department of Biology, The University of North Carolina at Chapel HillChapel HillUnited States
| | - Camille Miller
- Department of Biology, The University of North Carolina at Chapel HillChapel HillUnited States
| | - David R Sherwood
- Department of Biology, Duke UniversityDurhamUnited States
- Regeneration Next, Duke UniversityDurhamUnited States
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17
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Wang X, Voronina E. Diverse Roles of PUF Proteins in Germline Stem and Progenitor Cell Development in C. elegans. Front Cell Dev Biol 2020; 8:29. [PMID: 32117964 PMCID: PMC7015873 DOI: 10.3389/fcell.2020.00029] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2019] [Accepted: 01/14/2020] [Indexed: 01/05/2023] Open
Abstract
Stem cell development depends on post-transcriptional regulation mediated by RNA-binding proteins (RBPs) (Zhang et al., 1997; Forbes and Lehmann, 1998; Okano et al., 2005; Ratti et al., 2006; Kwon et al., 2013). Pumilio and FBF (PUF) family RBPs are highly conserved post-transcriptional regulators that are critical for stem cell maintenance (Wickens et al., 2002; Quenault et al., 2011). The RNA-binding domains of PUF proteins recognize a family of related sequence motifs in the target mRNAs, yet individual PUF proteins have clearly distinct biological functions (Lu et al., 2009; Wang et al., 2018). The C. elegans germline is a simple and powerful model system for analyzing regulation of stem cell development. Studies in C. elegans uncovered specific physiological roles for PUFs expressed in the germline stem cells ranging from control of proliferation and differentiation to regulation of the sperm/oocyte decision. Importantly, recent studies started to illuminate the mechanisms behind PUF functional divergence. This review summarizes the many roles of PUF-8, FBF-1, and FBF-2 in germline stem and progenitor cells (SPCs) and discusses the factors accounting for their distinct biological functions. PUF proteins are conserved in evolution, and insights into PUF-mediated regulation provided by the C. elegans model system are likely relevant for other organisms.
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Affiliation(s)
- Xiaobo Wang
- Division of Biological Sciences, University of Montana, Missoula, MT, United States
| | - Ekaterina Voronina
- Division of Biological Sciences, University of Montana, Missoula, MT, United States
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18
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Niche Cell Wrapping Ensures Primordial Germ Cell Quiescence and Protection from Intercellular Cannibalism. Curr Biol 2020; 30:708-714.e4. [PMID: 32008902 DOI: 10.1016/j.cub.2019.12.021] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2018] [Revised: 11/12/2019] [Accepted: 12/06/2019] [Indexed: 12/25/2022]
Abstract
Niche cells often wrap membrane extensions around stem cell surfaces. Niche wrapping has been proposed to retain stem cells in defined positions and affect signaling [e.g., 1, 2]. To test these hypotheses and uncover additional functions of wrapping, we investigated niche wrapping of primordial germ cells (PGCs) in the C. elegans embryonic gonad primordium. The gonad primordium contains two PGCs that are wrapped individually by two somatic gonad precursor cells (SGPs). SGPs are known to promote PGC survival during embryogenesis and exit from quiescence after hatching, although how they do so is unknown [3]. Here, we identify two distinct functions of SGP wrapping that are critical for PGC quiescence and survival. First, niche cell wrapping templates a laminin-based basement membrane around the gonad primordium. Laminin and the basement membrane receptor dystroglycan function to maintain niche cell wrapping, which is critical for normal gonad development. We find that laminin also preserves PGC quiescence during embryogenesis. Exit from quiescence following laminin depletion requires glp-1/Notch and is accompanied by inappropriate activation of the GLP-1 target sygl-1 in PGCs. Independent of basement membrane, SGP wrapping performs a second, crucial function to ensure PGC survival. Endodermal cells normally engulf and degrade large lobes extended by the PGCs [4]. When SGPs are absent, we show that endodermal cells can inappropriately engulf and cannibalize the PGC cell body. Our findings demonstrate how niche cell wrapping protects germ cells by manipulating their signaling environment and by shielding germ cells from unwanted cellular interactions that can compromise their survival.
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19
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Hubbard EJA, Schedl T. Biology of the Caenorhabditis elegans Germline Stem Cell System. Genetics 2019; 213:1145-1188. [PMID: 31796552 PMCID: PMC6893382 DOI: 10.1534/genetics.119.300238] [Citation(s) in RCA: 73] [Impact Index Per Article: 14.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2019] [Accepted: 09/09/2019] [Indexed: 12/14/2022] Open
Abstract
Stem cell systems regulate tissue development and maintenance. The germline stem cell system is essential for animal reproduction, controlling both the timing and number of progeny through its influence on gamete production. In this review, we first draw general comparisons to stem cell systems in other organisms, and then present our current understanding of the germline stem cell system in Caenorhabditis elegans In contrast to stereotypic somatic development and cell number stasis of adult somatic cells in C. elegans, the germline stem cell system has a variable division pattern, and the system differs between larval development, early adult peak reproduction and age-related decline. We discuss the cell and developmental biology of the stem cell system and the Notch regulated genetic network that controls the key decision between the stem cell fate and meiotic development, as it occurs under optimal laboratory conditions in adult and larval stages. We then discuss alterations of the stem cell system in response to environmental perturbations and aging. A recurring distinction is between processes that control stem cell fate and those that control cell cycle regulation. C. elegans is a powerful model for understanding germline stem cells and stem cell biology.
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Affiliation(s)
- E Jane Albert Hubbard
- Skirball Institute of Biomolecular Medicine, Departments of Cell Biology and Pathology, New York University School of Medicine, New York 10016
| | - Tim Schedl
- and Department of Genetics, Washington University School of Medicine, St. Louis, Missouri 63110
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20
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Crittenden SL, Lee C, Mohanty I, Battula S, Knobel K, Kimble J. Sexual dimorphism of niche architecture and regulation of the Caenorhabditis elegans germline stem cell pool. Mol Biol Cell 2019; 30:1757-1769. [PMID: 31067147 PMCID: PMC6727753 DOI: 10.1091/mbc.e19-03-0164] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2019] [Revised: 04/24/2019] [Accepted: 05/02/2019] [Indexed: 01/08/2023] Open
Abstract
Stem cell maintenance by niche signaling is a common theme across phylogeny. In the Caenorhabditis elegans gonad, the broad outlines of germline stem cell (GSC) regulation are the same for both sexes: GLP-1/Notch signaling from the mesenchymal distal tip cell niche maintains GSCs in the distal gonad of both sexes and does so via two key stem cell regulators, SYGL-1 and LST-1. Yet most recent analyses of niche signaling and GSC regulation have focused on XX hermaphrodites, an essentially female sex making sperm in larvae and oocytes in adults. Here we focus on GSC regulation in XO males. Sexual dimorphism of niche architecture, reported previously, suggested that the molecular responses to niche signaling or numbers of GSCs might also be sexually distinct. Remarkably, this is not the case. This work extends our understanding of the sexually dimorphic niche architecture, but also demonstrates that the dimorphic niches drive a similar molecular response and maintain a similar number of GSCs in their stem cell pools.
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Affiliation(s)
- Sarah L. Crittenden
- Howard Hughes Medical Institute, University of Wisconsin–Madison, Madison, WI 53706
- Department of Biochemistry, University of Wisconsin–Madison, Madison, WI 53706
| | - ChangHwan Lee
- Howard Hughes Medical Institute, University of Wisconsin–Madison, Madison, WI 53706
- Department of Biochemistry, University of Wisconsin–Madison, Madison, WI 53706
| | - Ipsita Mohanty
- Department of Biochemistry, University of Wisconsin–Madison, Madison, WI 53706
| | - Sindhu Battula
- Department of Biochemistry, University of Wisconsin–Madison, Madison, WI 53706
| | - Karla Knobel
- Department of Biochemistry, University of Wisconsin–Madison, Madison, WI 53706
| | - Judith Kimble
- Howard Hughes Medical Institute, University of Wisconsin–Madison, Madison, WI 53706
- Department of Biochemistry, University of Wisconsin–Madison, Madison, WI 53706
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21
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Charmpilas N, Tavernarakis N. Mitochondrial maturation drives germline stem cell differentiation in Caenorhabditis elegans. Cell Death Differ 2019; 27:601-617. [PMID: 31217501 PMCID: PMC7206027 DOI: 10.1038/s41418-019-0375-9] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2018] [Revised: 05/27/2019] [Accepted: 06/03/2019] [Indexed: 01/07/2023] Open
Abstract
The C. elegans germline recapitulates mammalian stem cell niches and provides an effective platform for investigating key aspects of stem cell biology. However, the molecular and physiological requirements for germline stem cell homeostasis remain largely elusive. Here, we report that mitochondrial biogenesis and function are crucial for germline stem cell identity. We show that general transcription activity in germline mitochondria is highly compartmentalized, and determines mitochondrial maturation. RPOM-1, the mitochondrial RNA polymerase, is differentially expressed as germ nuclei progress from the distal to the proximal gonad arm to form oocytes. Mitochondria undergo changes from globular to tubular morphology and become polarized, as they approach the proximal gonad arm. Notably, this mitochondrial maturation trajectory is evolutionarily conserved. We find that a similar transition and temporal mitochondrial RNA polymerase expression profile characterizes differentiation of mammalian stem cells. In C. elegans, ATP, and ROS production increases sharply during maturation. Impaired mitochondrial bioenergetics causes gonad syncytium tumor formation by disrupting the balance between mitosis and differentiation to oocytes, which results in a marked reduction of fecundity. Consequently, compensatory apoptosis is induced in the germline. Sperm-derived signals promote mitochondrial maturation and proper germ cell differentiation via the MEK/ERK kinase pathway. Germ cell fate decisions are determined by a crosstalk between Insulin/IGF-1 and TGF-β signaling, mitochondria and protein synthesis. Our findings demonstrate that mitochondrial transcription activity determines a shift in mitochondrial bioenergetics, which in turn regulates germline stem cell survival and differentiation. Perturbation of mitochondrial transcription hinders proper germ cell differentiation and causes germline tumor development.
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Affiliation(s)
- Nikolaos Charmpilas
- Institute of Molecular Biology and Biotechnology, Foundation for Research and Technology-Hellas, Heraklion, Greece.,Department of Biology, University of Crete, Heraklion, Greece
| | - Nektarios Tavernarakis
- Institute of Molecular Biology and Biotechnology, Foundation for Research and Technology-Hellas, Heraklion, Greece. .,Department of Basic Sciences, School of Medicine, University of Crete, 70013, Heraklion, Crete, Greece.
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22
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Developmental Control of the Cell Cycle: Insights from Caenorhabditis elegans. Genetics 2019; 211:797-829. [PMID: 30846544 PMCID: PMC6404260 DOI: 10.1534/genetics.118.301643] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2018] [Accepted: 10/10/2018] [Indexed: 12/11/2022] Open
Abstract
During animal development, a single fertilized egg forms a complete organism with tens to trillions of cells that encompass a large variety of cell types. Cell cycle regulation is therefore at the center of development and needs to be carried out in close coordination with cell differentiation, migration, and death, as well as tissue formation, morphogenesis, and homeostasis. The timing and frequency of cell divisions are controlled by complex combinations of external and cell-intrinsic signals that vary throughout development. Insight into how such controls determine in vivo cell division patterns has come from studies in various genetic model systems. The nematode Caenorhabditis elegans has only about 1000 somatic cells and approximately twice as many germ cells in the adult hermaphrodite. Despite the relatively small number of cells, C. elegans has diverse tissues, including intestine, nerves, striated and smooth muscle, and skin. C. elegans is unique as a model organism for studies of the cell cycle because the somatic cell lineage is invariant. Somatic cells divide at set times during development to produce daughter cells that adopt reproducible developmental fates. Studies in C. elegans have allowed the identification of conserved cell cycle regulators and provided insights into how cell cycle regulation varies between tissues. In this review, we focus on the regulation of the cell cycle in the context of C. elegans development, with reference to other systems, with the goal of better understanding how cell cycle regulation is linked to animal development in general.
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23
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Gordon KL, Payne SG, Linden-High LM, Pani AM, Goldstein B, Hubbard EJA, Sherwood DR. Ectopic Germ Cells Can Induce Niche-like Enwrapment by Neighboring Body Wall Muscle. Curr Biol 2019; 29:823-833.e5. [PMID: 30799241 DOI: 10.1016/j.cub.2019.01.056] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2018] [Revised: 01/18/2019] [Accepted: 01/23/2019] [Indexed: 12/20/2022]
Abstract
Niche cell enwrapment of stem cells and their differentiating progeny is common and provides a specialized signaling and protective environment. Elucidating the mechanisms underlying enwrapment behavior has important basic and clinical significance in not only understanding how niches are formed and maintained but also how they can be engineered and how they are misregulated in human pathologies, such as cancer. Previous work in C. elegans found that, when germ cells, which are enwrapped by somatic gonadal niche cells, are freed into the body cavity, they embed into other tissues. We investigated this phenomenon using live-cell imaging and discovered that ectopic germ cells preferentially induce body-wall muscle to extend cellular processes that enwrap the germ cells, the extent of which was strikingly similar to the distal tip cell (DTC)-germ stem cell niche. Enwrapment was specific for escaped germ cells, and genetic analysis revealed it did not depend on pathways that control cell death and engulfment or muscle arm extension. Instead, using a large-scale RNAi screen and GFP knockin strains, we discovered that the enwrapping behavior of muscle relied upon the same suite of cell-cell adhesion molecules that functioned in the endogenous niche: the C. elegans E-cadherin HMR-1, its intracellular associates α-catenin (HMP-1) and β-catenin (HMP-2), and the L1CAM protein SAX-7. This ectopic niche-like behavior resembles the seed-and-soil model of cancer metastasis and offers a new model to understand factors regulating ectopic niche formation.
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Affiliation(s)
- Kacy L Gordon
- Department of Biology, Duke University, Durham, NC 27708, USA
| | - Sara G Payne
- Department of Biology, Duke University, Durham, NC 27708, USA
| | | | - Ariel M Pani
- Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Bob Goldstein
- Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - E Jane Albert Hubbard
- Skirball Institute of Biomolecular Medicine, Departments of Cell Biology and Pathology, New York University School of Medicine, New York, NY 10016, USA
| | - David R Sherwood
- Department of Biology, Duke University, Durham, NC 27708, USA; Regeneration Next, Duke University, Durham, NC 27708, USA.
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24
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25
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Seidel HS, Smith TA, Evans JK, Stamper JQ, Mast TG, Kimble J. C. elegans germ cells divide and differentiate in a folded tissue. Dev Biol 2018; 442:173-187. [DOI: 10.1016/j.ydbio.2018.07.013] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2018] [Revised: 07/08/2018] [Accepted: 07/16/2018] [Indexed: 12/18/2022]
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26
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Haag ES, Fitch DHA, Delattre M. From "the Worm" to "the Worms" and Back Again: The Evolutionary Developmental Biology of Nematodes. Genetics 2018; 210:397-433. [PMID: 30287515 PMCID: PMC6216592 DOI: 10.1534/genetics.118.300243] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2017] [Accepted: 08/03/2018] [Indexed: 12/13/2022] Open
Abstract
Since the earliest days of research on nematodes, scientists have noted the developmental and morphological variation that exists within and between species. As various cellular and developmental processes were revealed through intense focus on Caenorhabditis elegans, these comparative studies have expanded. Within the genus Caenorhabditis, they include characterization of intraspecific polymorphisms and comparisons of distinct species, all generally amenable to the same laboratory culture methods and supported by robust genomic and experimental tools. The C. elegans paradigm has also motivated studies with more distantly related nematodes and animals. Combined with improved phylogenies, this work has led to important insights about the evolution of nematode development. First, while many aspects of C. elegans development are representative of Caenorhabditis, and of terrestrial nematodes more generally, others vary in ways both obvious and cryptic. Second, the system has revealed several clear examples of developmental flexibility in achieving a particular trait. This includes developmental system drift, in which the developmental control of homologous traits has diverged in different lineages, and cases of convergent evolution. Overall, the wealth of information and experimental techniques developed in C. elegans is being leveraged to make nematodes a powerful system for evolutionary cellular and developmental biology.
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Affiliation(s)
- Eric S Haag
- Department of Biology, University of Maryland, College Park, Maryland 20742
| | | | - Marie Delattre
- Laboratoire de Biologie Moléculaire de la Cellule, CNRS, INSERM, Ecole Normale Supérieure de Lyon, 69007, France
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27
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Caviglia S, Ober EA. Non-conventional protrusions: the diversity of cell interactions at short and long distance. Curr Opin Cell Biol 2018; 54:106-113. [DOI: 10.1016/j.ceb.2018.05.013] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2018] [Revised: 05/18/2018] [Accepted: 05/23/2018] [Indexed: 01/04/2023]
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28
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Berardi S, McFall A, Toledo-Hernandez A, Coote C, Graham H, Stine L, Rhodehouse K, Auernhamer A, Van Wynsberghe PM. The Period protein homolog LIN-42 regulates germline development in C. elegans. Mech Dev 2018; 153:42-53. [PMID: 30144508 DOI: 10.1016/j.mod.2018.08.008] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2018] [Revised: 08/20/2018] [Accepted: 08/20/2018] [Indexed: 10/28/2022]
Abstract
Germline stem cells are maintained in the distal region of the C. elegans gonad. These cells undergo mitotic divisions, and GLP-1/Notch signaling dictates whether they remain in this state. The somatic distal tip cell (DTC) caps the end of the distal gonad and is essential for maintenance of the germline mitotic zone. As germ cells move away from the DTC they exit mitosis and enter early meiotic prophase. Here we identify the Period protein homolog LIN-42 as a new regulator of germline development in C. elegans. LIN-42 is expressed in almost all somatic cells including the DTC, and LIN-42 functions as a transcription factor in the heterochronic pathway and to regulate molting. We found that the mitotic proliferative zone size in the distal gonad was significantly reduced by ~25% in lin-42 mutants compared to WT N2 worms. A lin-42 mutation also reduced the mitotic proliferative zone size caused by glp-1 partial loss-of-function and gain-of-function alleles. LIN-42 mediates this effect, at least in part, by regulating expression of the GLP-1/Notch ligand LAG-2. We further show that lin-42 expression itself is regulated by ATX-2, which promotes germline proliferation and is the homolog of the RNA binding protein ataxin-2 that is implicated in human neurodegenerative diseases. Altogether our results establish a new role for the conserved, important Period protein homolog LIN-42 in regulating early germline development. These results also suggest that in addition to regulating behavioral rhythms, the circadian clock plays an important role in communicating environmental signals to essential reproductive pathways.
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Affiliation(s)
- Skyler Berardi
- Department of Biology, Colgate University, Hamilton, NY 13346, USA
| | - Alanna McFall
- Department of Biology, Colgate University, Hamilton, NY 13346, USA
| | | | - Carolyn Coote
- Department of Biology, Colgate University, Hamilton, NY 13346, USA
| | - Hillary Graham
- Department of Biology, Colgate University, Hamilton, NY 13346, USA
| | - Laurel Stine
- Department of Biology, Colgate University, Hamilton, NY 13346, USA
| | - Kyle Rhodehouse
- Department of Biology, Colgate University, Hamilton, NY 13346, USA
| | - Anna Auernhamer
- Department of Biology, Colgate University, Hamilton, NY 13346, USA
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29
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Foray V, Pérez-Jiménez MM, Fattouh N, Landmann F. Wolbachia Control Stem Cell Behavior and Stimulate Germline Proliferation in Filarial Nematodes. Dev Cell 2018; 45:198-211.e3. [PMID: 29689195 DOI: 10.1016/j.devcel.2018.03.017] [Citation(s) in RCA: 36] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2017] [Revised: 02/20/2018] [Accepted: 03/23/2018] [Indexed: 01/04/2023]
Abstract
Although symbiotic interactions are ubiquitous in the living world, examples of developmental symbioses are still scarce. We show here the crucial role of Wolbachia in the oogenesis of filarial nematodes, a class of parasites of biomedical and veterinary relevance. We applied newly developed techniques to demonstrate the earliest requirements of Wolbachia in the parasite germline preceding the production of faulty embryos in Wolbachia-depleted nematodes. We show that Wolbachia stimulate germline proliferation in a cell-autonomous manner, and not through nucleotide supplementation as previously hypothesized. We also found Wolbachia to maintain the quiescence of a pool of germline stem cells to ensure a constant delivery of about 1,400 eggs per day for many years. The loss of quiescence upon Wolbachia depletion as well as the disorganization of the distal germline suggest that Wolbachia are required to execute the proper germline stem cell developmental program in order to produce viable eggs and embryos.
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Affiliation(s)
- Vincent Foray
- CRBM, University of Montpellier, CNRS, Montpellier, France
| | | | - Nour Fattouh
- CRBM, University of Montpellier, CNRS, Montpellier, France
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30
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Gopal S, Pocock R. Computational Analysis of the Caenorhabditis elegans Germline to Study the Distribution of Nuclei, Proteins, and the Cytoskeleton. J Vis Exp 2018. [PMID: 29733323 DOI: 10.3791/57702] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
The Caenorhabditis elegans (C. elegans) germline is used to study several biologically important processes including stem cell development, apoptosis, and chromosome dynamics. While the germline is an excellent model, the analysis is often two dimensional due to the time and labor required for three-dimensional analysis. Major readouts in such studies are the number/position of nuclei and protein distribution within the germline. Here, we present a method to perform automated analysis of the germline using confocal microscopy and computational approaches to determine the number and position of nuclei in each region of the germline. Our method also analyzes germline protein distribution that enables the three-dimensional examination of protein expression in different genetic backgrounds. Further, our study shows variations in cytoskeletal architecture in distinct regions of the germline that may accommodate specific spatial developmental requirements. Finally, our method enables automated counting of the sperm in the spermatheca of each germline. Taken together, our method enables rapid and reproducible phenotypic analysis of the C. elegans germline.
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Affiliation(s)
- Sandeep Gopal
- Development and Stem Cells Program, Monash Biomedicine Discovery Institute, Department of Anatomy and Developmental Biology, Monash University;
| | - Roger Pocock
- Development and Stem Cells Program, Monash Biomedicine Discovery Institute, Department of Anatomy and Developmental Biology, Monash University;
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31
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Automated three-dimensional reconstruction of the Caenorhabditis elegans germline. Dev Biol 2017; 432:222-228. [DOI: 10.1016/j.ydbio.2017.10.004] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2017] [Revised: 10/09/2017] [Accepted: 10/09/2017] [Indexed: 11/24/2022]
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32
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Dafachronic acid inhibits C. elegans germ cell proliferation in a DAF-12-dependent manner. Dev Biol 2017; 432:215-221. [PMID: 29066181 DOI: 10.1016/j.ydbio.2017.10.014] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2017] [Revised: 10/16/2017] [Accepted: 10/19/2017] [Indexed: 11/23/2022]
Abstract
Dafachronic acid (DA) is a bile acid-like steroid hormone that regulates dauer formation, heterochrony, and lifespan in C. elegans. Here, we describe that DA is an inhibitor of C. elegans germ stem cell proliferation in adult hermaphrodites. Using a C. elegans germ cell primary culture system, we show that DA inhibits the proliferation of germ cells in vitro. Exogenous DA reduces the frequency of large tumors in adult tumorous germline mutants and decreases the proliferation of wild-type germ stem cells in adult hermaphrodites. In contrast, DA has no appreciable effect on the proliferation of larval-stage germ cells in wild type. The inhibition of adult germ cell proliferation by DA requires its canonical receptor DAF-12. Blocking DA production by inactivating the cytochrome P450 DAF-9 increases germ cell proliferation in wild-type adult hermaphrodites and the frequency of large tumors in germline tumorous mutants, suggesting that DA inhibits the rate of germ cell proliferation under normal growth conditions.
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33
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The Canonical Notch Signaling Pathway: Structural and Biochemical Insights into Shape, Sugar, and Force. Dev Cell 2017; 41:228-241. [PMID: 28486129 DOI: 10.1016/j.devcel.2017.04.001] [Citation(s) in RCA: 252] [Impact Index Per Article: 36.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2017] [Revised: 03/04/2017] [Accepted: 04/03/2017] [Indexed: 02/07/2023]
Abstract
The Notch signaling pathway relies on a proteolytic cascade to release its transcriptionally active intracellular domain, on force to unfold a protective domain and permit proteolysis, on extracellular domain glycosylation to tune the forces exerted by endocytosed ligands, and on a motley crew of nuclear proteins, chromatin modifiers, ubiquitin ligases, and a few kinases to regulate activity and half-life. Herein we provide a review of recent molecular insights into how Notch signals are triggered and how cell shape affects these events, and we use the new insights to illuminate a few perplexing observations.
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Cottee PA, Cole T, Schultz J, Hoang HD, Vibbert J, Han SM, Miller MA. The C. elegans VAPB homolog VPR-1 is a permissive signal for gonad development. Development 2017. [PMID: 28634273 PMCID: PMC5482997 DOI: 10.1242/dev.152207] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
VAMP/synaptobrevin-associated proteins (VAPs) contain an N-terminal major sperm protein domain (MSPd) that is associated with amyotrophic lateral sclerosis. VAPs have an intracellular housekeeping function, as well as an extracellular signaling function mediated by the secreted MSPd. Here we show that the C. elegans VAP homolog VPR-1 is essential for gonad development. vpr-1 null mutants are maternal effect sterile due to arrested gonadogenesis following embryo hatching. Somatic gonadal precursor cells and germ cells fail to proliferate fully and complete their respective differentiation programs. Maternal or zygotic vpr-1 expression is sufficient to induce gonadogenesis and fertility. Genetic mosaic and cell type-specific expression studies indicate that vpr-1 activity is important in the nervous system, germ line and intestine. VPR-1 acts in parallel to Notch signaling, a key regulator of germline stem cell proliferation and differentiation. Neuronal vpr-1 expression is sufficient for gonadogenesis induction during a limited time period shortly after hatching. These results support the model that the secreted VPR-1 MSPd acts at least in part on gonadal sheath cell precursors in L1 to early L2 stage hermaphrodites to permit gonadogenesis. Highlighted Article:vpr-1 null mutants are sterile upon hatching, a defect rescued by the expression of MSPd from almost any tissue except for the somatic gonad itself. See also the companion paper by Schultz et al.
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Affiliation(s)
- Pauline A Cottee
- Department of Cell, Developmental and Integrative Biology, University of Alabama at Birmingham, Birmingham, AL 35294, USA
| | - Tim Cole
- Department of Cell, Developmental and Integrative Biology, University of Alabama at Birmingham, Birmingham, AL 35294, USA
| | - Jessica Schultz
- Department of Cell, Developmental and Integrative Biology, University of Alabama at Birmingham, Birmingham, AL 35294, USA
| | - Hieu D Hoang
- Department of Cell, Developmental and Integrative Biology, University of Alabama at Birmingham, Birmingham, AL 35294, USA
| | - Jack Vibbert
- Department of Cell, Developmental and Integrative Biology, University of Alabama at Birmingham, Birmingham, AL 35294, USA
| | - Sung Min Han
- Department of Cell, Developmental and Integrative Biology, University of Alabama at Birmingham, Birmingham, AL 35294, USA
| | - Michael A Miller
- Department of Cell, Developmental and Integrative Biology, University of Alabama at Birmingham, Birmingham, AL 35294, USA
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Abstract
Many stem cell niches contain support cells that increase contact with stem cells by enwrapping them in cellular processes. One example is the germ stem cell niche in C. elegans, which is composed of a single niche cell termed the distal tip cell (DTC) that extends cellular processes, constructing an elaborate plexus that enwraps germ stem cells. To identify genes required for plexus formation and to explore the function of this specialized enwrapping behavior, a series of targeted and tissue-specific RNAi screens were performed. Here we identify genes that promote stem cell enwrapment by the DTC plexus, including a set that specifically functions within the DTC, such as the chromatin modifier lin-40/MTA1, and others that act within the germline, such as the 14-3-3 signaling protein par-5. Analysis of genes that function within the germline to mediate plexus development reveal that they are required for expansion of the germ progenitor zone, supporting the emerging idea that germ stem cells signal to the niche to stimulate enwrapping behavior. Examination of wild-type animals with asymmetric plexus formation and animals with reduced DTC plexus elaboration via loss of two candidates including lin-40 indicate that cellular enwrapment promotes GLP-1/Notch signaling and germ stem cell fate. Together, our work identifies novel regulators of cellular enwrapment and suggests that reciprocal signaling between the DTC niche and the germ stem cells promotes enwrapment behavior and stem cell fate.
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36
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Hall DH. Gap junctions in C. elegans: Their roles in behavior and development. Dev Neurobiol 2017; 77:587-596. [PMID: 27294317 PMCID: PMC5412865 DOI: 10.1002/dneu.22408] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2016] [Revised: 06/08/2016] [Accepted: 06/08/2016] [Indexed: 01/07/2023]
Abstract
The nematode Caenorhabditis elegans utilizes gap junctions in different fashions in virtually all of its cells. This model animal has a surprisingly large number of innexin genes within its genome, and many nematode cell types can express multiple innexins at once, leading to the formation of diverse junction types and enough redundancy to limit the effect of single gene knockdowns on animal development or behavioral phenotypes. Here, we review the general properties of these junctions, their expression patterns, and their known roles in tissue development and in the animal's connectome. © 2016 Wiley Periodicals, Inc. Develop Neurobiol 77: 587-596, 2017.
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Affiliation(s)
- David H Hall
- Department of Neuroscience, Center for C. elegans Anatomy, Albert Einstein College of Medicine, Bronx, New York, 10461
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The Bright Fluorescent Protein mNeonGreen Facilitates Protein Expression Analysis In Vivo. G3-GENES GENOMES GENETICS 2017; 7:607-615. [PMID: 28108553 PMCID: PMC5295605 DOI: 10.1534/g3.116.038133] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
The Green Fluorescent Protein (GFP) has been tremendously useful in investigating cell architecture, protein localization, and protein function. Recent developments in transgenesis and genome editing methods now enable working with fewer transgene copies and, consequently, with physiological expression levels. However, lower signal intensity might become a limiting factor. The recently developed mNeonGreen protein is a brighter alternative to GFP in vitro. The goal of the present study was to determine how mNeonGreen performs in vivo in Caenorhabditis elegans—a model used extensively for fluorescence imaging in intact animals. We started with a side-by-side comparison between cytoplasmic forms of mNeonGreen and GFP expressed in the intestine, and in different neurons, of adult animals. While both proteins had similar photostability, mNeonGreen was systematically 3–5 times brighter than GFP. mNeonGreen was also used successfully to trace endogenous proteins, and label specific subcellular compartments such as the nucleus or the plasma membrane. To further demonstrate the utility of mNeonGreen, we tested transcriptional reporters for nine genes with unknown expression patterns. While mNeonGreen and GFP reporters gave overall similar expression patterns, low expression tissues were detected only with mNeonGreen. As a whole, our work establishes mNeonGreen as a brighter alternative to GFP for in vivo imaging in a multicellular organism. Furthermore, the present research illustrates the utility of mNeonGreen to tag proteins, mark subcellular regions, and describe new expression patterns, particularly in tissues with low expression.
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38
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Singh R, Hansen D. Regulation of the Balance Between Proliferation and Differentiation in Germ Line Stem Cells. Results Probl Cell Differ 2017; 59:31-66. [PMID: 28247045 DOI: 10.1007/978-3-319-44820-6_2] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
In many animals, reproductive fitness is dependent upon the production of large numbers of gametes over an extended period of time. This level of gamete production is possible due to the continued presence of germ line stem cells. These cells can produce two types of daughter cells, self-renewing daughter cells that will maintain the stem cell population and differentiating daughter cells that will become gametes. A balance must be maintained between the proliferating self-renewing cells and those that differentiate for long-term gamete production to be maintained. Too little proliferation can result in depletion of the stem cell population, while too little differentiation can lead to a lack of gamete formation and possible tumor formation. In this chapter, we discuss our current understanding of how the balance between proliferation and differentiation is achieved in three well-studied germ line model systems: the Drosophila female, the mouse male, and the C. elegans hermaphrodite. While these three systems have significant differences in how this balance is regulated, including differences in stem cell population size, signaling pathways utilized, and the use of symmetric and/or asymmetric cell divisions, there are also similarities found between them. These similarities include the reliance on a predominant signaling pathway to promote proliferation, negative feedback loops to rapidly shutoff proliferation-promoting cues, close association of the germ line stem cells with a somatic niche, cytoplasmic connections between cells, projections emanating from the niche cell, and multiple mechanisms to limit the spatial influence of the niche. A comparison between different systems may help to identify elements that are essential for a proper balance between proliferation and differentiation to be achieved and elements that may be achieved through various mechanisms.
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Affiliation(s)
- Ramya Singh
- Department of Biological Sciences, University of Calgary, Calgary, AB, Canada, T2N 1N4
| | - Dave Hansen
- Department of Biological Sciences, University of Calgary, Calgary, AB, Canada, T2N 1N4.
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39
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Lam AK, Phillips BT. Wnt Signaling Polarizes C. elegans Asymmetric Cell Divisions During Development. Results Probl Cell Differ 2017; 61:83-114. [PMID: 28409301 PMCID: PMC6057142 DOI: 10.1007/978-3-319-53150-2_4] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Asymmetric cell division is a common mode of cell differentiation during the invariant lineage of the nematode, C. elegans. Beginning at the four-cell stage, and continuing throughout embryogenesis and larval development, mother cells are polarized by Wnt ligands, causing an asymmetric inheritance of key members of a Wnt/β-catenin signal transduction pathway termed the Wnt/β-catenin asymmetry pathway. The resulting daughter cells are distinct at birth with one daughter cell activating Wnt target gene expression via β-catenin activation of TCF, while the other daughter displays transcriptional repression of these target genes. Here, we seek to review the body of evidence underlying a unified model for Wnt-driven asymmetric cell division in C. elegans, identify global themes that occur during asymmetric cell division, as well as highlight tissue-specific variations. We also discuss outstanding questions that remain unanswered regarding this intriguing mode of asymmetric cell division.
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Affiliation(s)
- Arielle Koonyee Lam
- Interdisciplinary Graduate Program in Molecular and Cellular Biology, University of Iowa, Iowa City, IA, USA
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40
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Abstract
The Caenorhabditis elegans germline is an excellent model for studying the regulation of a pool of stem cells and progression of cells from a stem cell state to a differentiated state. At the tissue level, the germline is organized in an assembly line with the germline stem cell (GSC) pool at one end and differentiated cells at the other. A simple mesenchymal niche caps the GSC region of the germline and maintains GSCs in an undifferentiated state by signaling through the conserved Notch pathway. Downstream of Notch signaling, key regulators include novel LST-1 and SYGL-1 proteins and a network of RNA regulatory proteins. In this chapter we present methods for characterizing the C. elegans GSC pool and early germ cell differentiation. The methods include examination of the germline in living and fixed worms, cell cycle analysis, and analysis of markers. We also discuss assays to separate mutants that affect the stem cell vs. differentiation decision from those that affect germ cell processes more generally.
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Affiliation(s)
- Sarah L Crittenden
- HHMI/Department of Biochemistry, Howard Hughes Medical Institute and University of Wisconsin-Madison, 433 Babcock Drive, Madison, WI, 53706-1544, USA.
| | - Hannah S Seidel
- HHMI/Department of Biochemistry, Howard Hughes Medical Institute and University of Wisconsin-Madison, 433 Babcock Drive, Madison, WI, 53706-1544, USA
| | - Judith Kimble
- HHMI/Department of Biochemistry, Howard Hughes Medical Institute and University of Wisconsin-Madison, 433 Babcock Drive, Madison, WI, 53706-1544, USA
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41
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Lee C, Sorensen EB, Lynch TR, Kimble J. C. elegans GLP-1/Notch activates transcription in a probability gradient across the germline stem cell pool. eLife 2016; 5:e18370. [PMID: 27705743 PMCID: PMC5094854 DOI: 10.7554/elife.18370] [Citation(s) in RCA: 57] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2016] [Accepted: 10/04/2016] [Indexed: 12/26/2022] Open
Abstract
C. elegans Notch signaling maintains a pool of germline stem cells within their single-celled mesenchymal niche. Here we investigate the Notch transcriptional response in germline stem cells using single-molecule fluorescence in situ hybridization coupled with automated, high-throughput quantitation. This approach allows us to distinguish Notch-dependent nascent transcripts in the nucleus from mature mRNAs in the cytoplasm. We find that Notch-dependent active transcription sites occur in a probabilistic fashion and, unexpectedly, do so in a steep gradient across the stem cell pool. Yet these graded nuclear sites create a nearly uniform field of mRNAs that extends beyond the region of transcriptional activation. Therefore, active transcription sites provide a precise view of where the Notch-dependent transcriptional complex is productively engaged. Our findings offer a new window into the Notch transcriptional response and demonstrate the importance of assaying nascent transcripts at active transcription sites as a readout for canonical signaling.
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Affiliation(s)
- ChangHwan Lee
- Howard Hughes Medical Institute, University of Wisconsin-Madison, Madison, United States
- Department of Biochemistry, University of Wisconsin-Madison, Madison, United States
| | - Erika B Sorensen
- Howard Hughes Medical Institute, University of Wisconsin-Madison, Madison, United States
- Department of Biochemistry, University of Wisconsin-Madison, Madison, United States
| | - Tina R Lynch
- Department of Biochemistry, University of Wisconsin-Madison, Madison, United States
| | - Judith Kimble
- Howard Hughes Medical Institute, University of Wisconsin-Madison, Madison, United States
- Department of Biochemistry, University of Wisconsin-Madison, Madison, United States
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42
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Saberi A, Jamal A, Beets I, Schoofs L, Newmark PA. GPCRs Direct Germline Development and Somatic Gonad Function in Planarians. PLoS Biol 2016; 14:e1002457. [PMID: 27163480 PMCID: PMC4862687 DOI: 10.1371/journal.pbio.1002457] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2015] [Accepted: 04/11/2016] [Indexed: 11/21/2022] Open
Abstract
Planarians display remarkable plasticity in maintenance of their germline, with the ability to develop or dismantle reproductive tissues in response to systemic and environmental cues. Here, we investigated the role of G protein-coupled receptors (GPCRs) in this dynamic germline regulation. By genome-enabled receptor mining, we identified 566 putative planarian GPCRs and classified them into conserved and phylum-specific subfamilies. We performed a functional screen to identify NPYR-1 as the cognate receptor for NPY-8, a neuropeptide required for sexual maturation and germ cell differentiation. Similar to NPY-8, knockdown of this receptor results in loss of differentiated germ cells and sexual maturity. NPYR-1 is expressed in neuroendocrine cells of the central nervous system and can be activated specifically by NPY-8 in cell-based assays. Additionally, we screened the complement of GPCRs with expression enriched in sexually reproducing planarians, and identified an orphan chemoreceptor family member, ophis, that controls differentiation of germline stem cells (GSCs). ophis is expressed in somatic cells of male and female gonads, as well as in accessory reproductive tissues. We have previously shown that somatic gonadal cells are required for male GSC specification and maintenance in planarians. However, ophis is not essential for GSC specification or maintenance and, therefore, defines a secondary role for planarian gonadal niche cells in promoting GSC differentiation. Our studies uncover the complement of planarian GPCRs and reveal previously unappreciated roles for these receptors in systemic and local (i.e., niche) regulation of germ cell development. Genome-wide analysis of the planarian Schmidtea mediterranea reveals a complement of over 550 G protein-coupled receptors, including two with critical roles in germline development. G protein-coupled receptors (GPCRs) are the largest and most versatile family of cell-surface receptors. They play critical roles in various cellular and physiological systems and have emerged as a leading group of therapeutic targets. Due to their structural and functional conservation across animals, much has been learned about GPCRs from studies in laboratory models. Here, we performed genome-wide receptor mining to identify and categorize the complement of GPCR-encoding genes in the planarian Schmidtea mediterranea, an emerging model organism for regeneration and germ cell biology. We then conducted two studies implicating planarian GPCRs in the regulation of reproductive function. First, we found the receptor component of a central neuropeptide Y signaling pathway and demonstrated its involvement in the systemic control of reproductive development. Next, we showed that a novel chemoreceptor family member is expressed in somatic cells of the planarian gonads and directs germ cell maturation via the niche. We predict that future studies on the hundreds of other planarian GPCRs identified in this work will not only help us understand the conserved role of these receptors in various physiological pathways but also pave the way for identification of novel therapeutic targets in parasitic relatives of the planarian.
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Affiliation(s)
- Amir Saberi
- Howard Hughes Medical Institute and Department of Cell and Developmental Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States of America
| | - Ayana Jamal
- Howard Hughes Medical Institute and Department of Cell and Developmental Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States of America
| | - Isabel Beets
- Department of Biology, Functional Genomics and Proteomics Unit, KU Leuven, Leuven, Belgium
| | - Liliane Schoofs
- Department of Biology, Functional Genomics and Proteomics Unit, KU Leuven, Leuven, Belgium
| | - Phillip A. Newmark
- Howard Hughes Medical Institute and Department of Cell and Developmental Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States of America
- * E-mail:
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43
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Hall BA, Piterman N, Hajnal A, Fisher J. Emergent stem cell homeostasis in the C. elegans germline is revealed by hybrid modeling. Biophys J 2016. [PMID: 26200879 PMCID: PMC4621618 DOI: 10.1016/j.bpj.2015.06.007] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
The establishment of homeostasis among cell growth, differentiation, and apoptosis is of key importance for organogenesis. Stem cells respond to temporally and spatially regulated signals by switching from mitotic proliferation to asymmetric cell division and differentiation. Executable computer models of signaling pathways can accurately reproduce a wide range of biological phenomena by reducing detailed chemical kinetics to a discrete, finite form. Moreover, coordinated cell movements and physical cell-cell interactions are required for the formation of three-dimensional structures that are the building blocks of organs. To capture all these aspects, we have developed a hybrid executable/physical model describing stem cell proliferation, differentiation, and homeostasis in the Caenorhabditis elegans germline. Using this hybrid model, we are able to track cell lineages and dynamic cell movements during germ cell differentiation. We further show how apoptosis regulates germ cell homeostasis in the gonad, and propose a role for intercellular pressure in developmental control. Finally, we use the model to demonstrate how an executable model can be developed from the hybrid system, identifying a mechanism that ensures invariance in fate patterns in the presence of instability.
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Affiliation(s)
- Benjamin A Hall
- Medical Research Council Cancer Unit, Hutchison/Medical Research Council Research Centre, University of Cambridge, Cambridge, United Kingdom; Microsoft Research Cambridge, Cambridge, UK.
| | - Nir Piterman
- Department of Computer Science, University of Leicester, Leicester, UK
| | - Alex Hajnal
- Institute of Molecular Life Sciences, University of Zurich, Zurich, Switzerland
| | - Jasmin Fisher
- Microsoft Research Cambridge, Cambridge, UK; Department of Biochemistry, University of Cambridge, Cambridge, UK.
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44
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Cinquin A, Zheng L, Taylor PH, Paz A, Zhang L, Chiang M, Snow JJ, Nie Q, Cinquin O. Semi-permeable Diffusion Barriers Enhance Patterning Robustness in the C. elegans Germline. Dev Cell 2016; 35:405-17. [PMID: 26609956 DOI: 10.1016/j.devcel.2015.10.027] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2014] [Revised: 07/15/2015] [Accepted: 10/28/2015] [Indexed: 01/29/2023]
Abstract
Positional information derived from local morphogen concentration plays an important role in patterning. A key question is how morphogen diffusion and gene expression regulation shape positional information into an appropriate profile with suitably low noise. We address this question using a model system--the C. elegans germline--whose regulatory network has been well characterized genetically but whose spatiotemporal dynamics are poorly understood. We show that diffusion within the germline syncytium is a critical control of stem cell differentiation and that semi-permeable diffusion barriers present at key locations make it possible--in combination with a feedback loop in the germline regulatory network--for mitotic zone size to be robust against spatial noise in Notch signaling. Spatial averaging within compartments defined by diffusion barriers is an advantageous patterning strategy, which attenuates noise while still allowing for sharp transitions between compartments. This strategy could apply to other organs.
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Affiliation(s)
- Amanda Cinquin
- Department of Developmental and Cell Biology, University of California at Irvine, Irvine, CA 92697, USA; Center for Complex Biological Systems, University of California at Irvine, Irvine, CA 92697, USA
| | - Likun Zheng
- Department of Mathematics, University of California at Irvine, Irvine, CA 92697, USA; Center for Complex Biological Systems, University of California at Irvine, Irvine, CA 92697, USA
| | - Pete H Taylor
- Department of Developmental and Cell Biology, University of California at Irvine, Irvine, CA 92697, USA; Center for Complex Biological Systems, University of California at Irvine, Irvine, CA 92697, USA
| | - Adrian Paz
- Department of Developmental and Cell Biology, University of California at Irvine, Irvine, CA 92697, USA; Center for Complex Biological Systems, University of California at Irvine, Irvine, CA 92697, USA
| | - Lei Zhang
- Department of Mathematics, University of California at Irvine, Irvine, CA 92697, USA; Center for Complex Biological Systems, University of California at Irvine, Irvine, CA 92697, USA
| | - Michael Chiang
- Department of Developmental and Cell Biology, University of California at Irvine, Irvine, CA 92697, USA; Center for Complex Biological Systems, University of California at Irvine, Irvine, CA 92697, USA
| | - Joshua J Snow
- Department of Biochemistry, University of Wisconsin at Madison, Madison, WI 53706, USA
| | - Qing Nie
- Department of Mathematics, University of California at Irvine, Irvine, CA 92697, USA; Center for Complex Biological Systems, University of California at Irvine, Irvine, CA 92697, USA
| | - Olivier Cinquin
- Department of Developmental and Cell Biology, University of California at Irvine, Irvine, CA 92697, USA; Center for Complex Biological Systems, University of California at Irvine, Irvine, CA 92697, USA.
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45
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Germline Stem Cell Differentiation Entails Regional Control of Cell Fate Regulator GLD-1 in Caenorhabditis elegans. Genetics 2016; 202:1085-103. [PMID: 26757772 DOI: 10.1534/genetics.115.185678] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2015] [Accepted: 01/07/2016] [Indexed: 12/18/2022] Open
Abstract
Germline stem cell differentiation in Caenorhabditis elegans is controlled by glp-1 Notch signaling. Cell fate regulator GLD-1 is sufficient to induce meiotic entry and expressed at a high level during meiotic prophase, inhibiting mitotic gene activity. glp-1 signaling and other regulators control GLD-1 levels post-transcriptionally (low in stem cells, high in meiotic prophase), but many aspects of GLD-1 regulation are uncharacterized, including the link between glp-1-mediated transcriptional control and post-transcriptional GLD-1 regulation. We established a sensitive assay to quantify GLD-1 levels across an ∼35-cell diameter field, where distal germline stem cells differentiate proximally into meiotic prophase cells in the adult C. elegans hermaphrodite, and applied the approach to mutants in known or proposed GLD-1 regulators. In wild-type GLD-1 levels elevated ∼20-fold in a sigmoidal pattern. We found that two direct transcriptional targets of glp-1 signaling, lst-1 and sygl-1, were individually required for repression of GLD-1. We determined that lst-1 and sygl-1 act in the same genetic pathway as known GLD-1 translational repressor fbf-1, while lst-1 also acts in parallel to fbf-1, linking glp-1-mediated transcriptional control and post-transcriptional GLD-1 repression. Additionally, we estimated the position in wild-type gonads where germ cells irreversibly commit to meiotic development based on GLD-1 levels in worms where glp-1 activity was manipulated to cause an irreversible fate switch. Analysis of known repressors and activators, as well as modeling the sigmoidal accumulation pattern, indicated that regulation of GLD-1 levels is largely regional, which we integrated with the current view of germline stem cell differentiation.
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Roy D, Michaelson D, Hochman T, Santella A, Bao Z, Goldberg JD, Hubbard EJA. Cell cycle features of C. elegans germline stem/progenitor cells vary temporally and spatially. Dev Biol 2016; 409:261-271. [PMID: 26577869 PMCID: PMC4827254 DOI: 10.1016/j.ydbio.2015.10.031] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2015] [Revised: 10/26/2015] [Accepted: 10/27/2015] [Indexed: 11/24/2022]
Abstract
Many organisms accumulate a pool of germline stem cells during development that is maintained in later life. The dynamics of establishment, expansion and homeostatic maintenance of this pool are subject to both developmental and physiological influences including the availability of a suitable niche microenvironment, nutritional status, and age. Here, we investigated the dynamics of germline proliferation during stages of expansion and homeostasis, using the C. elegans germ line as a model. The vast majority of germ cells in the proliferative zone are in interphase stages of mitosis (G1, S, G2) rather than in the active mitotic (M) phase. We examined mitotic index and DNA content, comparing different life stages, mutants, and physiological conditions. We found that germ cells in larval stages cycle faster than in adult stages, but that this difference could not be attributed to sexual fate of the germ cells. We also found that larval germ cells exhibit a lower average DNA content compared to adult germ cells. We extended our analysis to consider the effects of distance from the niche and further found that the spatial pattern of DNA content differs between larval and adult stages in the wild type and among mutants in pathways that interfere with cell cycle progression, cell fate, or both. Finally, we characterized expansion of the proliferative pool of germ cells during adulthood, using a regeneration paradigm (ARD recovery) in which animals are starved and re-fed. We compared adult stage regeneration and larval stage expansion, and found that the adult germ line is capable of rapid accumulation but does not sustain a larval-level mitotic index nor does it recapitulate the larval pattern of DNA content. The regenerated germ line does not reach the number of proliferative zone nuclei seen in the continuously fed adult. Taken together, our results suggest that cell cycle dynamics are under multiple influences including distance from the niche, age and/or maturation of the germ line, nutrition and, possibly, latitude for physical expansion.
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Affiliation(s)
- Debasmita Roy
- Skirball Institute of Biomolecular Medicine, Helen L. and Martin S. Kimmel Center for Stem Cell Biology, Departments of Cell Biology and Pathology, New York University School of Medicine, 540 First Avenue, New York, NY 10016, USA
| | - David Michaelson
- Skirball Institute of Biomolecular Medicine, Helen L. and Martin S. Kimmel Center for Stem Cell Biology, Departments of Cell Biology and Pathology, New York University School of Medicine, 540 First Avenue, New York, NY 10016, USA
| | - Tsivia Hochman
- Departments of Population Health and Environmental Medicine, Division of Biostatistics, New York University School of Medicine, 540 First Avenue, New York, NY, 10016, USA
| | - Anthony Santella
- Developmental Biology Program, Sloan-Kettering Institute, 1275 York Avenue, New York, NY, 10065, USA
| | - Zhirong Bao
- Developmental Biology Program, Sloan-Kettering Institute, 1275 York Avenue, New York, NY, 10065, USA
| | - Judith D Goldberg
- Departments of Population Health and Environmental Medicine, Division of Biostatistics, New York University School of Medicine, 540 First Avenue, New York, NY, 10016, USA
| | - E Jane Albert Hubbard
- Skirball Institute of Biomolecular Medicine, Helen L. and Martin S. Kimmel Center for Stem Cell Biology, Departments of Cell Biology and Pathology, New York University School of Medicine, 540 First Avenue, New York, NY 10016, USA.
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Seidel HS, Kimble J. Cell-cycle quiescence maintains Caenorhabditis elegans germline stem cells independent of GLP-1/Notch. eLife 2015; 4. [PMID: 26551561 PMCID: PMC4718729 DOI: 10.7554/elife.10832] [Citation(s) in RCA: 57] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2015] [Accepted: 11/07/2015] [Indexed: 12/13/2022] Open
Abstract
Many types of adult stem cells exist in a state of cell-cycle quiescence, yet it has remained unclear whether quiescence plays a role in maintaining the stem cell fate. Here we establish the adult germline of Caenorhabditis elegans as a model for facultative stem cell quiescence. We find that mitotically dividing germ cells--including germline stem cells--become quiescent in the absence of food. This quiescence is characterized by a slowing of S phase, a block to M-phase entry, and the ability to re-enter M phase rapidly in response to re-feeding. Further, we demonstrate that cell-cycle quiescence alters the genetic requirements for stem cell maintenance: The signaling pathway required for stem cell maintenance under fed conditions--GLP-1/Notch signaling--becomes dispensable under conditions of quiescence. Thus, cell-cycle quiescence can itself maintain stem cells, independent of the signaling pathway otherwise essential for such maintenance.
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Affiliation(s)
- Hannah S Seidel
- Department of Biochemistry, University of Wisconsin-Madison, Madison, United States.,The Ellison Medical Foundation Fellow of the Life Sciences Research Foundation, The Lawrence Ellison Foundation, Mount Airy, United States
| | - Judith Kimble
- Department of Biochemistry, University of Wisconsin-Madison, Madison, United States.,Howard Hughes Medical Institute, University of Wisconsin-Madison, Madison, United States
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Nousch M, Eckmann CR. Translational activation maintains germline tissue homeostasis during adulthood. WORM 2015; 4:e1042644. [PMID: 26430565 PMCID: PMC4588557 DOI: 10.1080/21624054.2015.1042644] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/06/2015] [Revised: 03/30/2015] [Accepted: 04/10/2015] [Indexed: 02/03/2023]
Abstract
Adult tissue maintenance is achieved through a tightly controlled equilibrium of 2 opposing cell fates: stem cell proliferation and differentiation. In recent years, the germ line emerged as a powerful in vivo model tissue to investigate the underlying gene expression mechanisms regulating this balance. Studies in numerous organisms highlighted the prevalence of post-transcriptional mRNA regulation, which relies on RNA-targeting factors that influence mRNA fates (e.g. decay or translational efficiency). Conserved translational repressors were identified that build negative feedback loops to ensure one or the other cell fate. However, to facilitate a fast and efficient transition between 2 opposing cell fates, translational repression per se appears not to be sufficient, suggesting the involvement of additional modes of gene expression regulation. Cytoplasmic poly(A) polymerases (cytoPAPs) represent a unique class of post-transcriptional mRNA regulators that modify mRNA 3' ends and positively influence cytoplasmic mRNA fates. We recently discovered that the 2 main cytoPAPs, GLD-2 and GLD-4, use distinct mechanisms to promote gene expression and that cytoPAP-mediated mRNA activation is important for regulating the size of the proliferative germ cell pool in the adult Caenorhabditis elegans gonad. Here, we comment on the different mechanisms of the 2 cytoPAPs as translational activators in germ cell development and focus on their biological roles in maintaining the balance between germline stem cell proliferation and differentiation in the Caenorhabditis elegans gonad.
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Affiliation(s)
- Marco Nousch
- Division of Genetics; Institute of Biology; Martin Luther University, Halle-Wittenberg ; Halle, Saales, Germany
| | - Christian R Eckmann
- Division of Genetics; Institute of Biology; Martin Luther University, Halle-Wittenberg ; Halle, Saales, Germany ; Max Planck Institute of Molecular Cell Biology and Genetics ; Dresden, Germany
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Fox PM, Schedl T. Analysis of Germline Stem Cell Differentiation Following Loss of GLP-1 Notch Activity in Caenorhabditis elegans. Genetics 2015; 201:167-84. [PMID: 26158953 PMCID: PMC4566261 DOI: 10.1534/genetics.115.178061] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2015] [Accepted: 07/01/2015] [Indexed: 11/18/2022] Open
Abstract
Stem cells generate the differentiated progeny cells of adult tissues. Stem cells in the Caenorhabditis elegans hermaphrodite germline are maintained within a proliferative zone of ∼230 cells, ∼20 cell diameters in length, through GLP-1 Notch signaling. The distal tip cell caps the germline and supplies GLP-1-activating ligand, and the distal-most germ cells that occupy this niche are likely self-renewing stem cells with active GLP-1 signaling. As germ cells are displaced from the niche, GLP-1 activity likely decreases, yet mitotically cycling germ cells are found throughout the proliferative zone prior to overt meiotic differentiation. Following loss of GLP-1 activity, it remains unclear whether stem cells undergo transit-amplifying (TA) divisions or more directly enter meiosis. To distinguish between these possibilities we employed a temperature-sensitive (ts) glp-1 mutant to manipulate GLP-1 activity. We characterized proliferative zone dynamics in glp-1(ts) mutants at permissive temperature and then analyzed the kinetics of meiotic entry of proliferative zone cells after loss of GLP-1. We found that entry of proliferative zone cells into meiosis following loss of GLP-1 activity is largely synchronous and independent of their distal-proximal position. Furthermore, the majority of cells complete only a single mitotic division before entering meiosis, independent of their distal-proximal position. We conclude that germ cells do not undergo TA divisions following loss of GLP-1 activity. We present a model for the dynamics of the proliferative zone that utilizes cell cycle rate and proliferative zone size and output and incorporates the more direct meiotic differentiation of germ cells following loss of GLP-1 activity.
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Affiliation(s)
- Paul M Fox
- Department of Genetics, Washington University School of Medicine, St. Louis, Missouri 63110
| | - Tim Schedl
- Department of Genetics, Washington University School of Medicine, St. Louis, Missouri 63110
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