1
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Zhang Z, Yang H, Fang L, Zhao G, Xiang J, Zheng JC, Qin Z. DOS-3 mediates cell-non-autonomous DAF-16/FOXO activity in antagonizing age-related loss of C. elegans germline stem/progenitor cells. Nat Commun 2024; 15:4904. [PMID: 38851828 PMCID: PMC11162419 DOI: 10.1038/s41467-024-49318-6] [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: 09/09/2023] [Accepted: 05/29/2024] [Indexed: 06/10/2024] Open
Abstract
Age-related depletion of stem cells causes tissue degeneration and failure to tissue regeneration, driving aging at the organismal level. Previously we reported a cell-non-autonomous DAF-16/FOXO activity in antagonizing the age-related loss of germline stem/progenitor cells (GSPCs) in C. elegans, indicating that regulation of stem cell aging occurs at the organ system level. Here we discover the molecular effector that links the cell-non-autonomous DAF-16/FOXO activity to GSPC maintenance over time by performing a tissue-specific DAF-16/FOXO transcriptome analysis. Our data show that dos-3, which encodes a non-canonical Notch ligand, is a direct transcriptional target of DAF-16/FOXO and mediates the effect of the cell-non-autonomous DAF-16/FOXO activity on GSPC maintenance through activating Notch signaling in the germ line. Importantly, expression of a human homologous protein can functionally substitute for DOS-3 in this scenario. As Notch signaling controls the specification of many tissue stem cells, similar mechanisms may exist in other aging stem cell systems.
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Affiliation(s)
- Zhifei Zhang
- Key Laboratory of Spine and Spinal Cord Injury Repair and Regeneration of Ministry of Education, Orthopedic Department of Tongji Hospital, School of Medicine, Tongji University, Shanghai, 200065, China
| | - Haiyan Yang
- Key Laboratory of Spine and Spinal Cord Injury Repair and Regeneration of Ministry of Education, Orthopedic Department of Tongji Hospital, School of Medicine, Tongji University, Shanghai, 200065, China
| | - Lei Fang
- Key Laboratory of Spine and Spinal Cord Injury Repair and Regeneration of Ministry of Education, Orthopedic Department of Tongji Hospital, School of Medicine, Tongji University, Shanghai, 200065, China
| | - Guangrong Zhao
- Key Laboratory of Spine and Spinal Cord Injury Repair and Regeneration of Ministry of Education, Orthopedic Department of Tongji Hospital, School of Medicine, Tongji University, Shanghai, 200065, China
| | - Jun Xiang
- Department of Urology, Tongji Hospital, Tongji University School of Medicine, Shanghai, 200065, China.
| | - Jialin C Zheng
- Center for Translational Neurodegeneration and Regenerative Therapy, Tongji Hospital Affiliated to Tongji University, Shanghai, 200065, China.
- State Key Laboratory of Cardiology and Medical Innovation Center, Shanghai East Hospital, School of Medicine, Tongji University, Shanghai, 200120, China.
- Shanghai Key Laboratory of Anesthesiology and Brain Functional Modulation, Shanghai Fourth People's Hospital, School of Medicine, Tongji University, Shanghai, 200080, China.
- Translational Research Institute of Brain and Brain-Like Intelligence, Shanghai Fourth People's Hospital affiliated to Tongji University School of Medicine, Shanghai, 200080, China.
- Innovation Center of Medical Basic Research for Brain Aging and Associated Diseases, Ministry of Education, Tongji University, Shanghai, 200331, China.
- Collaborative Innovation Center for Brain Science, Tongji University, Shanghai, 200331, China.
- Shanghai Frontiers Science Center of Nanocatalytic Medicine, Tongji University School of Medicine, Shanghai, 200331, China.
| | - Zhao Qin
- Key Laboratory of Spine and Spinal Cord Injury Repair and Regeneration of Ministry of Education, Orthopedic Department of Tongji Hospital, School of Medicine, Tongji University, Shanghai, 200065, China.
- Innovation Center of Medical Basic Research for Brain Aging and Associated Diseases, Ministry of Education, Tongji University, Shanghai, 200331, China.
- Collaborative Innovation Center for Brain Science, Tongji University, Shanghai, 200331, China.
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2
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Ferdous AS, Lynch TR, Costa Dos Santos SJ, Kapadia DH, Crittenden SL, Kimble J. LST-1 is a bifunctional regulator that feeds back on Notch-dependent transcription to regulate C. elegans germline stem cells. Proc Natl Acad Sci U S A 2023; 120:e2309964120. [PMID: 37729202 PMCID: PMC10523584 DOI: 10.1073/pnas.2309964120] [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: 06/13/2023] [Accepted: 08/15/2023] [Indexed: 09/22/2023] Open
Abstract
Notch signaling regulates stem cells across animal phylogeny. C. elegans Notch signaling activates transcription of two genes, lst-1 and sygl-1, that encode potent regulators of germline stem cells. The LST-1 protein regulates stem cells in two distinct ways: It promotes self-renewal posttranscriptionally and also restricts self-renewal by a poorly understood mechanism. Its self-renewal promoting activity resides in its N-terminal region, while its self-renewal restricting activity resides in its C-terminal region and requires the Zn finger. Here, we report that LST-1 limits self-renewal by down-regulating Notch-dependent transcription. We detect LST-1 in the nucleus, in addition to its previously known cytoplasmic localization. LST-1 lowers nascent transcript levels at both lst-1 and sygl-1 loci but not at let-858, a Notch-independent locus. LST-1 also lowers levels of two key components of the Notch activation complex, the LAG-1 DNA binding protein and Notch intracellular domain (NICD). Genetically, an LST-1 Zn finger mutant increases Notch signaling strength in both gain- and loss-of-function GLP-1/Notch receptor mutants. Biochemically, LST-1 co-immunoprecipitates with LAG-1 from nematode extracts, suggesting a direct effect. LST-1 is thus a bifunctional regulator that coordinates posttranscriptional and transcriptional mechanisms in a single protein. This LST-1 bifunctionality relies on its bipartite protein architecture and is bolstered by generation of two LST-1 isoforms, one specialized for Notch downregulation. A conserved theme from worms to human is the coupling of PUF-mediated RNA repression together with Notch feedback in the same protein.
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Affiliation(s)
- Ahlan S. Ferdous
- Department of Biochemistry, University of Wisconsin-Madison, Madison, WI53706
- Integrated Program in Biochemistry, University of Wisconsin-Madison, Madison, WI53706
| | - Tina R. Lynch
- Department of Biochemistry, University of Wisconsin-Madison, Madison, WI53706
- Integrated Program in Biochemistry, University of Wisconsin-Madison, Madison, WI53706
| | | | - Deep H. Kapadia
- Department of Biochemistry, University of Wisconsin-Madison, Madison, WI53706
| | - Sarah L. Crittenden
- Department of Biochemistry, University of Wisconsin-Madison, Madison, WI53706
| | - Judith Kimble
- Department of Biochemistry, University of Wisconsin-Madison, Madison, WI53706
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3
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Ferdous AS, Costa Dos Santos SJ, Kanzler CR, Shin H, Carrick BH, Crittenden SL, Wickens M, Kimble J. The in vivo functional significance of PUF hub partnerships in C. elegans germline stem cells. Development 2023; 150:dev201705. [PMID: 37070766 PMCID: PMC10259659 DOI: 10.1242/dev.201705] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2023] [Accepted: 03/29/2023] [Indexed: 04/19/2023]
Abstract
PUF RNA-binding proteins are conserved stem cell regulators. Four PUF proteins govern self-renewal of Caenorhabditis elegans germline stem cells together with two intrinsically disordered proteins, LST-1 and SYGL-1. Based on yeast two-hybrid results, we previously proposed a composite self-renewal hub in the stem cell regulatory network, with eight PUF partnerships and extensive redundancy. Here, we investigate LST-1-PUF and SYGL-1-PUF partnerships and their molecular activities in their natural context - nematode stem cells. We confirm LST-1-PUF partnerships and their specificity to self-renewal PUFs by co-immunoprecipitation and show that an LST-1(AmBm) mutant defective for PUF-interacting motifs does not complex with PUFs in nematodes. LST-1(AmBm) is used to explore the in vivo functional significance of the LST-1-PUF partnership. Tethered LST-1 requires this partnership to repress expression of a reporter RNA, and LST-1 requires the partnership to co-immunoprecipitate with NTL-1/Not1 of the CCR4-NOT complex. We suggest that the partnership provides multiple molecular interactions that work together to form an effector complex on PUF target RNAs in vivo. Comparison of LST-1-PUF and Nanos-Pumilio reveals fundamental molecular differences, making LST-1-PUF a distinct paradigm for PUF partnerships.
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Affiliation(s)
- Ahlan S. Ferdous
- Department of Biochemistry, University of Wisconsin-Madison, Madison, WI 53706, USA
| | | | - Charlotte R. Kanzler
- Department of Biochemistry, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Heaji Shin
- Department of Biochemistry, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Brian H. Carrick
- Department of Biochemistry, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Sarah L. Crittenden
- Department of Biochemistry, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Marvin Wickens
- Department of Biochemistry, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Judith Kimble
- Department of Biochemistry, University of Wisconsin-Madison, Madison, WI 53706, USA
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4
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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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5
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Qiu C, Wine RN, Campbell ZT, Hall T. Bipartite interaction sites differentially modulate RNA-binding affinity of a protein complex essential for germline stem cell self-renewal. Nucleic Acids Res 2022; 50:536-548. [PMID: 34908132 PMCID: PMC8754657 DOI: 10.1093/nar/gkab1220] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2021] [Revised: 11/23/2021] [Accepted: 12/08/2021] [Indexed: 01/09/2023] Open
Abstract
In C. elegans, PUF proteins promote germline stem cell self-renewal. Their functions hinge on partnerships with two proteins that are redundantly required for stem cell maintenance. Here we focus on understanding how the essential partner protein, LST-1, modulates mRNA regulation by the PUF protein, FBF-2. LST-1 contains two nonidentical sites of interaction with FBF-2, LST-1 A and B. Our crystal structures of complexes of FBF-2, LST-1 A, and RNA visualize how FBF-2 associates with LST-1 A versus LST-1 B. One commonality is that FBF-2 contacts the conserved lysine and leucine side chains in the KxxL motifs in LST-1 A and B. A key difference is that FBF-2 forms unique contacts with regions N- and C-terminal to the KxxL motif. Consequently, LST-1 A does not modulate the RNA-binding affinity of FBF-2, whereas LST-1 B decreases RNA-binding affinity of FBF-2. The N-terminal region of LST-1 B, which binds near the 5' end of RNA elements, is essential to modulate FBF-2 RNA-binding affinity, while the C-terminal residues of LST-1 B contribute strong binding affinity to FBF-2. We conclude that LST-1 has the potential to impact which mRNAs are regulated depending on the precise nature of engagement through its functionally distinct FBF binding sites.
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Affiliation(s)
- Chen Qiu
- Epigenetics and Stem Cell Biology Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, NC 27709, USA
| | - Robert N Wine
- Epigenetics and Stem Cell Biology Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, NC 27709, USA
| | - Zachary T Campbell
- Department of Biological Sciences, University of Texas at Dallas, Richardson, TX 75025, USA
| | - Traci M Tanaka Hall
- Epigenetics and Stem Cell Biology Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, NC 27709, USA
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6
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Gopal S, Amran A, Elton A, Ng L, Pocock R. A somatic proteoglycan controls Notch-directed germ cell fate. Nat Commun 2021; 12:6708. [PMID: 34795288 PMCID: PMC8602670 DOI: 10.1038/s41467-021-27039-4] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2020] [Accepted: 11/02/2021] [Indexed: 11/24/2022] Open
Abstract
Communication between the soma and germline optimizes germ cell fate programs. Notch receptors are key determinants of germ cell fate but how somatic signals direct Notch-dependent germ cell behavior is undefined. Here we demonstrate that SDN-1 (syndecan-1), a somatic transmembrane proteoglycan, controls expression of the GLP-1 (germline proliferation-1) Notch receptor in the Caenorhabditis elegans germline. We find that SDN-1 control of a somatic TRP calcium channel governs calcium-dependent binding of an AP-2 transcription factor (APTF-2) to the glp-1 promoter. Hence, SDN-1 signaling promotes GLP-1 expression and mitotic germ cell fate. Together, these data reveal SDN-1 as a putative communication nexus between the germline and its somatic environment to control germ cell fate decisions.
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Affiliation(s)
- Sandeep Gopal
- Department of Anatomy and Developmental Biology, Monash Biomedicine Discovery Institute, Monash University, Melbourne, Victoria, 3800, Australia.
| | - Aqilah Amran
- grid.1002.30000 0004 1936 7857Department of Anatomy and Developmental Biology, Monash Biomedicine Discovery Institute, Monash University, Melbourne, Victoria 3800 Australia
| | - Andre Elton
- grid.1002.30000 0004 1936 7857Department of Anatomy and Developmental Biology, Monash Biomedicine Discovery Institute, Monash University, Melbourne, Victoria 3800 Australia
| | - Leelee Ng
- grid.1002.30000 0004 1936 7857Department of Anatomy and Developmental Biology, Monash Biomedicine Discovery Institute, Monash University, Melbourne, Victoria 3800 Australia
| | - Roger Pocock
- Department of Anatomy and Developmental Biology, Monash Biomedicine Discovery Institute, Monash University, Melbourne, Victoria, 3800, Australia.
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7
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Tolkin T, Hubbard EJA. Germline Stem and Progenitor Cell Aging in C. elegans. Front Cell Dev Biol 2021; 9:699671. [PMID: 34307379 PMCID: PMC8297657 DOI: 10.3389/fcell.2021.699671] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2021] [Accepted: 06/07/2021] [Indexed: 11/13/2022] Open
Abstract
Like many animals and humans, reproduction in the nematode C. elegans declines with age. This decline is the cumulative result of age-related changes in several steps of germline function, many of which are highly accessible for experimental investigation in this short-lived model organism. Here we review recent work showing that a very early and major contributing step to reproductive decline is the depletion of the germline stem and progenitor cell pool. Since many cellular and molecular aspects of stem cell biology and aging are conserved across animals, understanding mechanisms of age-related decline of germline stem and progenitor cells in C. elegans has broad implications for aging stem cells, germline stem cells, and reproductive aging.
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Affiliation(s)
- Theadora Tolkin
- Department of Cell Biology, Skirball Institute of Biomolecular Medicine, NYU Grossman School of Medicine, New York, NY, United States
| | - E Jane Albert Hubbard
- Department of Cell Biology, Skirball Institute of Biomolecular Medicine, NYU Grossman School of Medicine, New York, NY, United States
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8
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Dalfó D, Ding Y, Liang Q, Fong A, Cipriani PG, Piano F, Zheng JC, Qin Z, Hubbard EJA. A Genome-Wide RNAi Screen for Enhancers of a Germline Tumor Phenotype Caused by Elevated GLP-1/Notch Signaling in Caenorhabditis elegans. G3 (BETHESDA, MD.) 2020; 10:4323-4334. [PMID: 33077477 PMCID: PMC7718737 DOI: 10.1534/g3.120.401632] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/03/2020] [Accepted: 10/08/2020] [Indexed: 11/18/2022]
Abstract
Stem cells are tightly controlled in vivo Both the balance between self-renewal and differentiation and the rate of proliferation are often regulated by multiple factors. The Caenorhabditis elegans hermaphrodite germ line provides a simple and accessible system for studying stem cells in vivo In this system, GLP-1/Notch activity prevents the differentiation of distal germ cells in response to ligand production from the nearby distal tip cell, thereby supporting a stem cell pool. However, a delay in germline development relative to somatic gonad development can cause a pool of undifferentiated germ cells to persist in response to alternate Notch ligands expressed in the proximal somatic gonad. This pool of undifferentiated germ cells forms a proximal tumor that, in adulthood, blocks the oviduct. This type of "latent niche"-driven proximal tumor is highly penetrant in worms bearing the temperature-sensitive weak gain-of-function mutation glp-1(ar202) at the restrictive temperature. At the permissive temperature, few worms develop tumors. Nevertheless, several interventions elevate the penetrance of proximal tumor formation at the permissive temperature, including reduced insulin signaling or the ablation of distal-most sheath cells. To systematically identify genetic perturbations that enhance proximal tumor formation, we sought genes that, upon RNAi depletion, elevate the percentage of worms bearing proximal germline tumors in glp-1(ar202) at the permissive temperature. We identified 43 genes representing a variety of functional classes, the most enriched of which is "translation". Some of these genes also influence the distal germ line, and some are conserved genes for which genetic interactions with Notch were not previously known in this system.
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Affiliation(s)
- Diana Dalfó
- Skirball Institute of Biomolecular Medicine, Departments of Cell Biology and Pathology, NYU Grossman School of Medicine
| | | | | | - Alex Fong
- Skirball Institute of Biomolecular Medicine, Departments of Cell Biology and Pathology, NYU Grossman School of Medicine
| | - Patricia Giselle Cipriani
- Center for Genomics and Systems Biology, Department of Biology, New York University and Center for Genomics and Systems Biology, New York University Abu Dhabi
| | - Fabio Piano
- Center for Genomics and Systems Biology, Department of Biology, New York University and Center for Genomics and Systems Biology, New York University Abu Dhabi
| | | | - Zhao Qin
- School of Medicine, Tongji University
- Key Laboratory of Spine and Spinal Cord Injury Repair and Regeneration of Ministry of Education, Orthopedic Department of Tongji Hospital, School of Medicine, Tongji University
| | - E Jane Albert Hubbard
- Skirball Institute of Biomolecular Medicine, Departments of Cell Biology and Pathology, NYU Grossman School of Medicine
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9
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Wodarz D, Komarova NL. Mutant Evolution in Spatially Structured and Fragmented Expanding Populations. Genetics 2020; 216:191-203. [PMID: 32661138 PMCID: PMC7463292 DOI: 10.1534/genetics.120.303422] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2020] [Accepted: 06/23/2020] [Indexed: 11/18/2022] Open
Abstract
Mutant evolution in spatially structured systems is important for a range of biological systems, but aspects of it still require further elucidation. Adding to previous work, we provide a simple derivation of growth laws that characterize the number of mutants of different relative fitness in expanding populations in spatial models of different dimensionalities. These laws are universal and independent of "microscopic" modeling details. We further study the accumulation of mutants and find that, with advantageous and neutral mutants, more of them are present in spatially structured, compared to well-mixed colonies of the same size. The behavior of disadvantageous mutants is subtle: if they are disadvantageous through a reduction in division rates, the result is the same, and it is the opposite if the disadvantage is due to a death rate increase. Finally, we show that in all cases, the same results are observed in fragmented, nonspatial patch models. This suggests that the patterns observed are the consequence of population fragmentation, and not spatial restrictions per se We provide an intuitive explanation for the complex dependence of disadvantageous mutant evolution on spatial restriction, which relies on desynchronized dynamics in different locations/patches, and plays out differently depending on whether the disadvantage is due to a lower division rate or a higher death rate. Implications for specific biological systems, such as the evolution of drug-resistant cell mutants in cancer or bacterial biofilms, are discussed.
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Affiliation(s)
- Dominik Wodarz
- Department of Population Health and Disease Prevention, Program in Public Health, Susan and Henry Samueli College of Health Sciences, University of California Irvine, California 92697
- Department of Mathematics, University of California Irvine, California 92697
| | - Natalia L Komarova
- Department of Mathematics, University of California Irvine, California 92697
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10
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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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11
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Haupt KA, Law KT, Enright AL, Kanzler CR, Shin H, Wickens M, Kimble J. A PUF Hub Drives Self-Renewal in Caenorhabditis elegans Germline Stem Cells. Genetics 2020; 214:147-161. [PMID: 31740451 PMCID: PMC6944405 DOI: 10.1534/genetics.119.302772] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2019] [Accepted: 11/05/2019] [Indexed: 01/12/2023] Open
Abstract
Stem cell regulation relies on extrinsic signaling from a niche plus intrinsic factors that respond and drive self-renewal within stem cells. A priori, loss of niche signaling and loss of the intrinsic self-renewal factors might be expected to have equivalent stem cell defects. Yet this simple prediction has not been borne out for most stem cells, including Caenorhabditis elegans germline stem cells (GSCs). The central regulators of C. elegans GSCs include extrinsically acting GLP-1/Notch signaling from the niche; intrinsically acting RNA-binding proteins in the PUF family, termed FBF-1 and FBF-2 (collectively FBF); and intrinsically acting PUF partner proteins that are direct Notch targets. Abrogation of either GLP-1/Notch signaling or its targets yields an earlier and more severe GSC defect than loss of FBF-1 and FBF-2, suggesting that additional intrinsic regulators must exist. Here, we report that those missing regulators are two additional PUF proteins, PUF-3 and PUF-11 Remarkably, an fbf-1fbf-2 ; puf-3puf-11 quadruple null mutant has a GSC defect virtually identical to that of a glp-1/Notch null mutant. PUF-3 and PUF-11 both affect GSC maintenance, both are expressed in GSCs, and epistasis experiments place them at the same position as FBF within the network. Therefore, action of PUF-3 and PUF-11 explains the milder GSC defect in fbf-1fbf-2 mutants. We conclude that a "PUF hub," comprising four PUF proteins and two PUF partners, constitutes the intrinsic self-renewal node of the C. elegans GSC RNA regulatory network. Discovery of this hub underscores the significance of PUF RNA-binding proteins as key regulators of stem cell maintenance.
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Affiliation(s)
- Kimberly A Haupt
- Department of Biochemistry, University of Wisconsin-Madison, Wisconsin 53706
| | - Kimberley T Law
- Department of Biochemistry, University of Wisconsin-Madison, Wisconsin 53706
| | - Amy L Enright
- Department of Biochemistry, University of Wisconsin-Madison, Wisconsin 53706
| | - Charlotte R Kanzler
- Department of Biochemistry, University of Wisconsin-Madison, Wisconsin 53706
| | - Heaji Shin
- Department of Biochemistry, University of Wisconsin-Madison, Wisconsin 53706
| | - Marvin Wickens
- Department of Biochemistry, University of Wisconsin-Madison, Wisconsin 53706
| | - Judith Kimble
- Department of Biochemistry, University of Wisconsin-Madison, Wisconsin 53706
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12
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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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13
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Haupt KA, Enright AL, Ferdous AS, Kershner AM, Shin H, Wickens M, Kimble J. The molecular basis of LST-1 self-renewal activity and its control of stem cell pool size. Development 2019; 146:dev.181644. [PMID: 31515205 DOI: 10.1242/dev.181644] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2019] [Accepted: 09/05/2019] [Indexed: 01/01/2023]
Abstract
PUF RNA-binding proteins have diverse roles in animal development, with a broadly conserved role in stem cells. Two paradigmatic PUF proteins, FBF-1 and FBF-2, promote both self-renewal and differentiation in the C. elegans germline. The LST-1 protein is a pivotal regulator of self-renewal and is oncogenic when mis-expressed. Here, we demonstrate that LST-1 self-renewal activity resides within a predicted disordered region that harbors two KXXL motifs. We find that the KXXL motifs mediate the binding of LST-1 to FBF, and that point mutations of these motifs abrogate LST-1 self-renewal activity. The LST-1-FBF partnership is therefore crucial to stem cell maintenance and is a key element in the FBF regulatory network. A distinct region within LST-1 determines its spatial expression and size of the GSC pool. Most importantly, the molecular understanding of how an IDR-rich protein works in an essential partnership with a conserved stem cell regulator and RNA-binding protein suggests broad new avenues for combinatorial control.
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Affiliation(s)
- Kimberly A Haupt
- Department of Biochemistry, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Amy L Enright
- Department of Biochemistry, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Ahlan S Ferdous
- Department of Biochemistry, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Aaron M Kershner
- Howard Hughes Medical Institute, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Heaji Shin
- Department of Biochemistry, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Marvin Wickens
- Department of Biochemistry, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Judith Kimble
- Department of Biochemistry, University of Wisconsin-Madison, Madison, WI 53706, USA .,Howard Hughes Medical Institute, University of Wisconsin-Madison, Madison, WI 53706, USA
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14
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Qiu C, Bhat VD, Rajeev S, Zhang C, Lasley AE, Wine RN, Campbell ZT, Hall TMT. A crystal structure of a collaborative RNA regulatory complex reveals mechanisms to refine target specificity. eLife 2019; 8:48968. [PMID: 31397673 PMCID: PMC6697444 DOI: 10.7554/elife.48968] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2019] [Accepted: 08/09/2019] [Indexed: 01/09/2023] Open
Abstract
In the Caenorhabditis elegans germline, fem-3 Binding Factor (FBF) partners with LST-1 to maintain stem cells. A crystal structure of an FBF-2/LST-1/RNA complex revealed that FBF-2 recognizes a short RNA motif different from the characteristic 9-nt FBF binding element, and compact motif recognition coincided with curvature changes in the FBF-2 scaffold. Previously, we engineered FBF-2 to favor recognition of shorter RNA motifs without curvature change (Bhat et al., 2019). In vitro selection of RNAs bound by FBF-2 suggested sequence specificity in the central region of the compact element. This bias, reflected in the crystal structure, was validated in RNA-binding assays. FBF-2 has the intrinsic ability to bind to this shorter motif. LST-1 weakens FBF-2 binding affinity for short and long motifs, which may increase target selectivity. Our findings highlight the role of FBF scaffold flexibility in RNA recognition and suggest a new mechanism by which protein partners refine target site selection.
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Affiliation(s)
- Chen Qiu
- Epigenetics and Stem Cell Biology LaboratoryNational Institute of Environmental Health Sciences, National Institutes of HealthResearch Triangle ParkUnited States
| | - Vandita D Bhat
- Department of Biological SciencesUniversity of Texas at DallasRichardsonUnited States
| | - Sanjana Rajeev
- Department of Biological SciencesUniversity of Texas at DallasRichardsonUnited States
| | - Chi Zhang
- Department of Biological SciencesUniversity of Texas at DallasRichardsonUnited States
| | - Alexa E Lasley
- Department of Biological SciencesUniversity of Texas at DallasRichardsonUnited States
| | - Robert N Wine
- Epigenetics and Stem Cell Biology LaboratoryNational Institute of Environmental Health Sciences, National Institutes of HealthResearch Triangle ParkUnited States
| | - Zachary T Campbell
- Department of Biological SciencesUniversity of Texas at DallasRichardsonUnited States
| | - Traci M Tanaka Hall
- Epigenetics and Stem Cell Biology LaboratoryNational Institute of Environmental Health Sciences, National Institutes of HealthResearch Triangle ParkUnited States
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15
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Roy D, Kahler DJ, Yun C, Hubbard EJA. Functional Interactions Between rsks-1/S6K, glp-1/Notch, and Regulators of Caenorhabditis elegans Fertility and Germline Stem Cell Maintenance. G3 (BETHESDA, MD.) 2018; 8:3293-3309. [PMID: 30126834 PMCID: PMC6169383 DOI: 10.1534/g3.118.200511] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/18/2018] [Accepted: 08/06/2018] [Indexed: 12/17/2022]
Abstract
The proper accumulation and maintenance of stem cells is critical for organ development and homeostasis. The Notch signaling pathway maintains stem cells in diverse organisms and organ systems. In Caenorhabditis elegans, GLP-1/Notch activity prevents germline stem cell (GSC) differentiation. Other signaling mechanisms also influence the maintenance of GSCs, including the highly-conserved TOR substrate ribosomal protein S6 kinase (S6K). Although C. elegans bearing either a null mutation in rsks-1/S6K or a reduction-of-function (rf) mutation in glp-1/Notch produce half the normal number of adult germline progenitors, virtually all these single mutant animals are fertile. However, glp-1(rf) rsks-1(null) double mutant animals are all sterile, and in about half of their gonads, all GSCs differentiate, a distinctive phenotype associated with a significant reduction or loss of GLP-1 signaling. How rsks-1/S6K promotes GSC fate is unknown. Here, we determine that rsks-1/S6K acts germline-autonomously to maintain GSCs, and that it does not act through Cyclin-E or MAP kinase in this role. We found that interfering with translation also enhances glp-1(rf), but that regulation through rsks-1 cannot fully account for this effect. In a genome-scale RNAi screen for genes that act similarly to rsks-1/S6K, we identified 56 RNAi enhancers of glp-1(rf) sterility, many of which were previously not known to interact functionally with Notch. Further investigation revealed at least six candidates that, by genetic criteria, act linearly with rsks-1/S6K. These include genes encoding translation-related proteins, cacn-1/Cactin, an RNA exosome component, and a Hedgehog-related ligand. We found that additional Hedgehog-related ligands may share functional relationships with glp-1/Notch and rsks-1/S6K in maintaining germline progenitors.
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Affiliation(s)
- Debasmita Roy
- Skirball Institute of Biomolecular Medicine, Departments of Cell Biology and Pathology, New York University School of Medicine, New York, NY 10016
| | - David J Kahler
- NYU High Throughput Biology Laboratory, NYU Langone Health, New York, NY 10016
| | - Chi Yun
- NYU High Throughput Biology Laboratory, NYU Langone Health, New York, NY 10016
| | - 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
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16
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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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Mohammad A, Vanden Broek K, Wang C, Daryabeigi A, Jantsch V, Hansen D, Schedl T. Initiation of Meiotic Development Is Controlled by Three Post-transcriptional Pathways in Caenorhabditis elegans. Genetics 2018; 209:1197-1224. [PMID: 29941619 PMCID: PMC6063227 DOI: 10.1534/genetics.118.300985] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2018] [Accepted: 06/20/2018] [Indexed: 11/18/2022] Open
Abstract
A major event in germline development is the transition from stem/progenitor cells to entry into meiosis and gametogenesis. This transition requires downregulation of mitotic cell cycle activity and upregulation of processes associated with meiosis. We identify the Caenorhabditis elegans SCFPROM-1 E3 ubiquitin-ligase complex as functioning to downregulate mitotic cell cycle protein levels including cyclin E, WAPL-1, and KNL-2 at meiotic entry and, independently, promoting homologous chromosome pairing as a positive regulator of the CHK-2 kinase. SCFPROM-1 is thus a novel regulator of meiotic entry, coordinating downregulation of mitotic cell cycle proteins and promoting homolog pairing. We further show that SCFPROM-1 functions redundantly, in parallel to the previously described GLD-1 and GLD-2 meiotic entry pathways, downstream of and inhibited by GLP-1 Notch signaling, which specifies the stem cell fate. Accordingly, C. elegans employs three post-transcriptional pathways, SCFPROM-1-mediated protein degradation, GLD-1-mediated translational repression, and GLD-2-mediated translational activation, to control and coordinate the initiation of meiotic development.
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Affiliation(s)
- Ariz Mohammad
- Department of Genetics, School of Medicine, Washington University in St. Louis, Missouri 63110
| | - Kara Vanden Broek
- Department of Biological Sciences, University of Calgary, T2N 1N4, Canada
| | - Christopher Wang
- Department of Biological Sciences, University of Calgary, T2N 1N4, Canada
| | - Anahita Daryabeigi
- Department of Chromosome Biology, Max F. Perutz Laboratories, University of Vienna, Vienna Biocenter, 1030, Austria
| | - Verena Jantsch
- Department of Chromosome Biology, Max F. Perutz Laboratories, University of Vienna, Vienna Biocenter, 1030, Austria
| | - Dave Hansen
- Department of Biological Sciences, University of Calgary, T2N 1N4, Canada
| | - Tim Schedl
- Department of Genetics, School of Medicine, Washington University in St. Louis, Missouri 63110
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18
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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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19
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Spickard EA, Joshi PM, Rothman JH. The multipotency-to-commitment transition in Caenorhabditis elegans-implications for reprogramming from cells to organs. FEBS Lett 2018; 592:838-851. [PMID: 29334121 DOI: 10.1002/1873-3468.12977] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2017] [Revised: 12/22/2017] [Accepted: 01/11/2018] [Indexed: 12/13/2022]
Abstract
In animal embryos, cells transition from a multipotential state, with the capacity to adopt multiple fates, into an irreversible, committed state of differentiation. This multipotency-to-commitment transition (MCT) is evident from experiments in which cell fate is reprogrammed by transcription factors for cell type-specific differentiation, as has been observed extensively in Caenorhabditis elegans. Although factors that direct differentiation into each of the three germ layer types cannot generally reprogram cells after the MCT in this animal, transcription factors for endoderm development are able to do so in multiple differentiated cell types. In one case, these factors can redirect the development of an entire organ in the process of "transorganogenesis". Natural transdifferentiation also occurs in a small number of differentiated cells during normal C. elegans development. We review these reprogramming and transdifferentiation events, highlighting the cellular and developmental contexts in which they occur, and discuss common themes underlying direct cell lineage reprogramming. Although certain aspects may be unique to the model system, growing evidence suggests that some mechanisms are evolutionarily conserved and may shed light on cellular plasticity and disease in humans.
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Affiliation(s)
- Erik A Spickard
- Department of MCD Biology and Neuroscience Research Institute, University of California Santa Barbara, CA, USA
| | - Pradeep M Joshi
- Department of MCD Biology and Neuroscience Research Institute, University of California Santa Barbara, CA, USA
| | - Joel H Rothman
- Department of MCD Biology and Neuroscience Research Institute, University of California Santa Barbara, CA, USA
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20
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Gao J, Colaiácovo MP. Zipping and Unzipping: Protein Modifications Regulating Synaptonemal Complex Dynamics. Trends Genet 2017; 34:232-245. [PMID: 29290403 DOI: 10.1016/j.tig.2017.12.001] [Citation(s) in RCA: 77] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2017] [Revised: 11/28/2017] [Accepted: 12/01/2017] [Indexed: 12/23/2022]
Abstract
The proteinaceous zipper-like structure known as the synaptonemal complex (SC), which forms between pairs of homologous chromosomes during meiosis from yeast to humans, plays important roles in promoting interhomolog crossover formation, regulating cessation of DNA double-strand break (DSB) formation following crossover designation, and ensuring accurate meiotic chromosome segregation. Recent studies are starting to reveal critical roles for different protein modifications in regulating SC dynamics. Protein SUMOylation, N-terminal acetylation, and phosphorylation have been shown to be essential for the regulated assembly and disassembly of the SC. Moreover, phosphorylation of specific SC components has been found to link changes in SC dynamics with meiotic recombination. This review highlights the latest findings on how protein modifications regulate SC dynamics and functions.
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Affiliation(s)
- Jinmin Gao
- Institute of Biomedical Sciences, College of Life Sciences, Key Laboratory of Animal Resistance Biology of Shandong Province, Shandong Normal University, Jinan, Shandong, 250014, China; Department of Genetics, Harvard Medical School, Boston, MA 02115, USA
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21
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Shin H, Haupt KA, Kershner AM, Kroll-Conner P, Wickens M, Kimble J. SYGL-1 and LST-1 link niche signaling to PUF RNA repression for stem cell maintenance in Caenorhabditis elegans. PLoS Genet 2017; 13:e1007121. [PMID: 29232700 PMCID: PMC5741267 DOI: 10.1371/journal.pgen.1007121] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2017] [Revised: 12/22/2017] [Accepted: 11/20/2017] [Indexed: 01/14/2023] Open
Abstract
Central questions in regenerative biology include how stem cells are maintained and how they transition from self-renewal to differentiation. Germline stem cells (GSCs) in Caeno-rhabditis elegans provide a tractable in vivo model to address these questions. In this system, Notch signaling and PUF RNA binding proteins, FBF-1 and FBF-2 (collectively FBF), maintain a pool of GSCs in a naïve state. An open question has been how Notch signaling modulates FBF activity to promote stem cell self-renewal. Here we report that two Notch targets, SYGL-1 and LST-1, link niche signaling to FBF. We find that SYGL-1 and LST-1 proteins are cytoplasmic and normally restricted to the GSC pool region. Increasing the distribution of SYGL-1 expands the pool correspondingly, and vast overexpression of either SYGL-1 or LST-1 generates a germline tumor. Thus, SYGL-1 and LST-1 are each sufficient to drive "stemness" and their spatial restriction prevents tumor formation. Importantly, SYGL-1 and LST-1 can only drive tumor formation when FBF is present. Moreover, both proteins interact physically with FBF, and both are required to repress a signature FBF mRNA target. Together, our results support a model in which SYGL-1 and LST-1 form a repressive complex with FBF that is crucial for stem cell maintenance. We further propose that progression from a naïve stem cell state to a state primed for differentiation relies on loss of SYGL-1 and LST-1, which in turn relieves FBF target RNAs from repression. Broadly, our results provide new insights into the link between niche signaling and a downstream RNA regulatory network and how this circuitry governs the balance between self-renewal and differentiation.
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Affiliation(s)
- Heaji Shin
- Department of Biochemistry, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
| | - Kimberly A. Haupt
- Department of Biochemistry, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
| | - Aaron M. Kershner
- Howard Hughes Medical Institute, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
| | - Peggy Kroll-Conner
- Howard Hughes Medical Institute, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
| | - Marvin Wickens
- Department of Biochemistry, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
| | - Judith Kimble
- Department of Biochemistry, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
- Howard Hughes Medical Institute, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
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22
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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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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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24
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Lee MH, Mamillapalli SS, Keiper BD, Cha DS. A systematic mRNA control mechanism for germline stem cell homeostasis and cell fate specification. BMB Rep 2016; 49:93-8. [PMID: 26303971 PMCID: PMC4915122 DOI: 10.5483/bmbrep.2016.49.2.135] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2015] [Indexed: 11/20/2022] Open
Abstract
Germline stem cells (GSCs) are the best understood adult stem cell types in the nematode Caenorhabditis elegans, and have provided an important model system for studying stem cells and their cell fate in vivo, in mammals. In this review, we propose a mechanism that controls GSCs and their cell fate through selective activation, repression and mobilization of the specific mRNAs. This mechanism is acutely controlled by known signal transduction pathways (e.g., Notch signaling and Ras-ERK MAPK signaling pathways) and P granule (analogous to mammalian germ granule)-associated mRNA regulators (FBF-1, FBF-2, GLD-1, GLD-2, GLD-3, RNP-8 and IFE-1). Importantly, all regulators are highly conserved in many multi-cellular animals. Therefore, GSCs from a simple animal may provide broad insight into vertebrate stem cells (e.g., hematopoietic stem cells) and their cell fate specification. [BMB Reports 2016; 49(2): 93-98]
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Affiliation(s)
- Myon-Hee Lee
- Department of Medicine, Hematology/Oncology Division, Brody School of Medicine, East Carolina University, Greenville, NC 27834, USA; Lineberger Comprehensive Cancer Center, University of North Carolina-Chapel Hill, Chapel Hill, NC 27599, USA
| | - Srivalli Swathi Mamillapalli
- Department of Medicine, Hematology/Oncology Division, Brody School of Medicine, East Carolina University, Greenville, NC 27834, USA
| | - Brett D Keiper
- Department of Biochemistry and Molecular Biology, Brody School of Medicine, East Carolina University, Greenville, NC 27834, USA
| | - Dong Seok Cha
- Department of Oriental Pharmacy, College of Pharmacy, Woosuk University, Jeonju 55338, Korea
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25
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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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26
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Gonadal transcriptomic analysis and differentially expressed genes in the testis and ovary of the Pacific white shrimp (Litopenaeus vannamei). BMC Genomics 2015; 16:1006. [PMID: 26607692 PMCID: PMC4659196 DOI: 10.1186/s12864-015-2219-4] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2015] [Accepted: 11/16/2015] [Indexed: 01/15/2023] Open
Abstract
Background The Pacific white shrimp (Litopenaeus vannamei) is the world’s most prevalent cultured crustacean species. However, the supply of high-quality broodstocks is limited and baseline information related to its reproductive activity and molecular issues related to gonad development are scarce. In this study, we performed transcriptome sequencing on the gonads of adult male and female L. vannamei to identify sex-related genes. Results A total of 25.16 gigabases (Gb) of sequences were generated from four L. vannamei gonadal tissue libraries. After quality control, 24.11 Gb of clean reads were selected from the gonadal libraries. De-novo assembly of all the clean reads generated a total of 65,218 unigenes with a mean size of 1021 bp and a N50 of 2000 bp. A search of all-unigene against Nr, SwissProt, KEGG, COG and NT databases resulted in 26,482, 23,062, 20,659, 11,935 and 14,626 annotations, respectively, providing a total of 30,304 annotated unigenes. Among annotated unigenes, 12,320 unigenes were assigned to gene ontology categories and 20,659 unigenes were mapped to 258 KEGG pathways. By comparing the ovary and testis libraries, 19,279 testicular up-regulated and 3,529 ovarian up-regulated unigenes were identified. Enrichment analysis of differentially expressed unigenes resulted in 1060 significantly enriched GO terms and 34 significantly enriched KEGG pathways. Nine ovary-specific, 6 testis-specific, 45 testicular up-regulated and 39 ovarian up-regulated unigenes were then confirmed by semi-quantitative PCR and quantitative real-time PCR. In addition, using all-unigenes as a reference, a total of 13,233 simple sequence repeats (SSRs) were identified in 10,411 unigene sequences. Conclusions The present study depicts the first large-scale RNA sequencing of shrimp gonads. We have identified many important sex-related functional genes, GO terms and pathways, all of which will facilitate future research into the reproductive biology of shrimp. We expect that the SSRs detected in this study can then be used as genetic markers for germplasm evaluation of breeding and imported populations. Electronic supplementary material The online version of this article (doi:10.1186/s12864-015-2219-4) contains supplementary material, which is available to authorized users.
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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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Atwell K, Qin Z, Gavaghan D, Kugler H, Hubbard EJA, Osborne JM. Mechano-logical model of C. elegans germ line suggests feedback on the cell cycle. Development 2015; 142:3902-11. [PMID: 26428008 PMCID: PMC4712881 DOI: 10.1242/dev.126359] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2015] [Accepted: 09/17/2015] [Indexed: 12/20/2022]
Abstract
The Caenorhabditis elegans germ line is an outstanding model system in which to study the control of cell division and differentiation. Although many of the molecules that regulate germ cell proliferation and fate decisions have been identified, how these signals interact with cellular dynamics and physical forces within the gonad remains poorly understood. We therefore developed a dynamic, 3D in silico model of the C. elegans germ line, incorporating both the mechanical interactions between cells and the decision-making processes within cells. Our model successfully reproduces key features of the germ line during development and adulthood, including a reasonable ovulation rate, correct sperm count, and appropriate organization of the germ line into stably maintained zones. The model highlights a previously overlooked way in which germ cell pressure may influence gonadogenesis, and also predicts that adult germ cells might be subject to mechanical feedback on the cell cycle akin to contact inhibition. We provide experimental data consistent with the latter hypothesis. Finally, we present cell trajectories and ancestry recorded over the course of a simulation. The novel approaches and software described here link mechanics and cellular decision-making, and are applicable to modeling other developmental and stem cell systems.
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Affiliation(s)
- Kathryn Atwell
- Computational Biology Group, Department of Computer Science, University of Oxford, Oxford OX1 3QD, UK Biological Computation Group, Computational Science Laboratory, Microsoft Research Cambridge, Cambridge CB1 2FB, UK
| | - Zhao Qin
- Skirball Institute of Biomolecular Medicine, Department of Cell Biology and Kimmel Center for Stem Cell Biology, New York University School of Medicine, New York, NY 10016, USA
| | - David Gavaghan
- Computational Biology Group, Department of Computer Science, University of Oxford, Oxford OX1 3QD, UK
| | - Hillel Kugler
- Biological Computation Group, Computational Science Laboratory, Microsoft Research Cambridge, Cambridge CB1 2FB, UK Faculty of Engineering, Bar-Ilan University, Ramat Gan 5290002, Israel
| | - E Jane Albert Hubbard
- Skirball Institute of Biomolecular Medicine, Department of Cell Biology and Kimmel Center for Stem Cell Biology, New York University School of Medicine, New York, NY 10016, USA
| | - James M Osborne
- Computational Biology Group, Department of Computer Science, University of Oxford, Oxford OX1 3QD, UK Biological Computation Group, Computational Science Laboratory, Microsoft Research Cambridge, Cambridge CB1 2FB, UK School of Mathematics and Statistics, University of Melbourne, Melbourne 3010, Australia
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Splicing Machinery Facilitates Post-Transcriptional Regulation by FBFs and Other RNA-Binding Proteins in Caenorhabditis elegans Germline. G3-GENES GENOMES GENETICS 2015; 5:2051-9. [PMID: 26268245 PMCID: PMC4592988 DOI: 10.1534/g3.115.019315] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Genetic interaction screens are an important approach for understanding complex regulatory networks governing development. We used a genetic interaction screen to identify cofactors of FBF-1 and FBF-2, RNA-binding proteins that regulate germline stem cell proliferation in Caenorhabditis elegans. We found that components of splicing machinery contribute to FBF activity as splicing factor knockdowns enhance sterility of fbf-1 and fbf-2 single mutants. This sterility phenocopied multiple aspects of loss of fbf function, suggesting that splicing factors contribute to stem cell maintenance. However, previous reports indicate that splicing factors instead promote the opposite cell fate, namely, differentiation. We explain this discrepancy by proposing that splicing factors facilitate overall RNA regulation in the germline. Indeed, we find that loss of splicing factors produces synthetic phenotypes with a mutation in another RNA regulator, FOG-1, but not with a mutation in a gene unrelated to posttranscriptional regulation (dhc-1). We conclude that inefficient pre-mRNA splicing may interfere with multiple posttranscriptional regulatory events, which has to be considered when interpreting results of genetic interaction screens.
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Qin Z, Hubbard EJA. Non-autonomous DAF-16/FOXO activity antagonizes age-related loss of C. elegans germline stem/progenitor cells. Nat Commun 2015; 6:7107. [PMID: 25960195 PMCID: PMC4432587 DOI: 10.1038/ncomms8107] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2014] [Accepted: 04/07/2015] [Indexed: 12/20/2022] Open
Abstract
Stem cells maintain tissues and organs over the lifespan of individuals. How aging influences this process is unclear. Here we investigate the effects of aging on C. elegans germline stem/progenitor cells and show that the progenitor pool is depleted over time in a manner dependent on inhibition of DAF-16/FOXO by insulin/IGF-1 signalling (IIS). Our data indicate that DAF-16/FOXO activity in certain somatic gonad cells is required for germline progenitor maintenance, and that this role is separable from the effect of DAF-16/FOXO on organismal aging. In addition, blocking germ cell flux, similar to reducing IIS, maintains germline progenitors. This effect is partially dependent on gonadal DAF-16/FOXO activity. Our results imply that (1) longevity pathways can regulate aging stem cells through anatomically separable mechanisms, (2) stem cell maintenance is not necessarily prioritized and (3) stem cell regulation can occur at the level of an entire organ system such as the reproductive system. The number of germline stem/progenitor cells in C. elegans declines with age. Here the authors show this cell loss is mediated by the transcription factor DAF-16/FOXO acting in specific somatic gonad cells, demonstrating that stem cell aging can be anatomically uncoupled from organismal aging.
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Affiliation(s)
- Zhao Qin
- Departments of Cell Biology and Pathology, The Helen L. and Martin S. Kimmel Center for Stem Cell Biology, Skirball Institute for Biomolecular Medicine, New York University School of Medicine, 540 First Avenue, New York, New York, USA
| | - E Jane Albert Hubbard
- Departments of Cell Biology and Pathology, The Helen L. and Martin S. Kimmel Center for Stem Cell Biology, Skirball Institute for Biomolecular Medicine, New York University School of Medicine, 540 First Avenue, New York, New York, USA
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31
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32
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Gupta P, Leahul L, Wang X, Wang C, Bakos B, Jasper K, Hansen D. Proteasome regulation of the chromodomain protein MRG-1 controls the balance between proliferative fate and differentiation in the C. elegans germ line. Development 2015; 142:291-302. [PMID: 25564623 DOI: 10.1242/dev.115147] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
The level of stem cell proliferation must be tightly controlled for proper development and tissue homeostasis. Multiple levels of gene regulation are often employed to regulate stem cell proliferation to ensure that the amount of proliferation is aligned with the needs of the tissue. Here we focus on proteasome-mediated protein degradation as a means of regulating the activities of proteins involved in controlling the stem cell proliferative fate in the C. elegans germ line. We identify five potential E3 ubiquitin ligases, including the RFP-1 RING finger protein, as being involved in regulating proliferative fate. RFP-1 binds to MRG-1, a homologue of the mammalian chromodomain-containing protein MRG15 (MORF4L1), which has been implicated in promoting the proliferation of neural precursor cells. We find that C. elegans with reduced proteasome activity, or that lack RFP-1 expression, have increased levels of MRG-1 and a shift towards increased proliferation in sensitized genetic backgrounds. Likewise, reduction of MRG-1 partially suppresses stem cell overproliferation. MRG-1 levels are controlled independently of the spatially regulated GLP-1/Notch signalling pathway, which is the primary signal controlling the extent of stem cell proliferation in the C. elegans germ line. We propose a model in which MRG-1 levels are controlled, at least in part, by the proteasome, and that the levels of MRG-1 set a threshold upon which other spatially regulated factors act in order to control the balance between the proliferative fate and differentiation in the C. elegans germ line.
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Affiliation(s)
- Pratyush Gupta
- Department of Biological Sciences, University of Calgary, 2500 University Drive, Calgary, Alberta, Canada T2N 1N4
| | - Lindsay Leahul
- Department of Biological Sciences, University of Calgary, 2500 University Drive, Calgary, Alberta, Canada T2N 1N4
| | - Xin Wang
- Department of Biological Sciences, University of Calgary, 2500 University Drive, Calgary, Alberta, Canada T2N 1N4
| | - Chris Wang
- Department of Biological Sciences, University of Calgary, 2500 University Drive, Calgary, Alberta, Canada T2N 1N4
| | - Brendan Bakos
- Department of Biological Sciences, University of Calgary, 2500 University Drive, Calgary, Alberta, Canada T2N 1N4
| | - Katie Jasper
- Department of Biological Sciences, University of Calgary, 2500 University Drive, Calgary, Alberta, Canada T2N 1N4
| | - Dave Hansen
- Department of Biological Sciences, University of Calgary, 2500 University Drive, Calgary, Alberta, Canada T2N 1N4
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Kershner AM, Shin H, Hansen TJ, Kimble J. Discovery of two GLP-1/Notch target genes that account for the role of GLP-1/Notch signaling in stem cell maintenance. Proc Natl Acad Sci U S A 2014; 111:3739-44. [PMID: 24567412 PMCID: PMC3956202 DOI: 10.1073/pnas.1401861111] [Citation(s) in RCA: 77] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
A stem cell's immediate microenvironment creates an essential "niche" to maintain stem cell self-renewal. Many niches and their intercellular signaling pathways are known, but for the most part, the key downstream targets of niche signaling remain elusive. Here, we report the discovery of two GLP-1/Notch target genes, lst-1 (lateral signaling target) and sygl-1 (synthetic Glp), that function redundantly to maintain germ-line stem cells (GSCs) in the nematode Caenorhabditis elegans. Whereas lst-1 and sygl-1 single mutants appear normal, lst-1 sygl-1 double mutants are phenotypically indistinguishable from glp-1/Notch mutants. Multiple lines of evidence demonstrate that GLP-1/Notch signaling activates lst-1 and sygl-1 expression in GSCs within the niche. Therefore, these two genes fully account for the role of GLP-1/Notch signaling in GSC maintenance. Importantly, lst-1 and sygl-1 are not required for GLP-1/Notch signaling per se. We conclude that lst-1 and sygl-1 forge a critical link between Notch signaling and GSC maintenance.
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Affiliation(s)
| | - Heaji Shin
- Department of Biochemistry, University of Wisconsin, Madison, WI 53706
| | - Tyler J. Hansen
- Department of Biochemistry, University of Wisconsin, Madison, WI 53706
| | - Judith Kimble
- Howard Hughes Medical Institute and
- Department of Biochemistry, University of Wisconsin, Madison, WI 53706
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34
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Hanna CB, Hennebold JD. Ovarian germline stem cells: an unlimited source of oocytes? Fertil Steril 2014; 101:20-30. [PMID: 24382341 DOI: 10.1016/j.fertnstert.2013.11.009] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2013] [Revised: 11/06/2013] [Accepted: 11/07/2013] [Indexed: 12/28/2022]
Abstract
While there has been progress in directing the development of embryonic stem cells and induced pluripotent stem cells toward a germ cell state, their ability to serve as a source of functional oocytes in a clinically relevant model or situation has yet to be established. Recent studies suggest that the adult mammalian ovary is not endowed with a finite number of oocytes, but instead possesses stem cells that contribute to their renewal. The ability to isolate and promote the growth and development of such ovarian germline stem cells (GSCs) would provide a novel means to treat infertility in women. Although such ovarian GSCs are well characterized in nonmammalian model organisms, the findings that support the existence of adult ovarian GSCs in mammals have been met with considerable evidence that disputes their existence. This review details the lessons provided by model organisms that successfully utilize ovarian GSCs to allow for a continual and high level of female germ cell production throughout their life, with a specific focus on the cellular mechanisms involved in GSC self-renewal and oocyte development. Such an overview of the role that oogonial stem cells play in maintaining fertility in nonmammalian species serves as a backdrop for the data generated to date that supports or disputes the existence of GSCs in mammals as well as the future of this area of research in terms of its potential for any application in reproductive medicine.
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Affiliation(s)
- Carol B Hanna
- Division of Reproductive and Developmental Sciences, Oregon National Primate Research Center, Oregon Health and Science University, Portland, Oregon.
| | - Jon D Hennebold
- Division of Reproductive and Developmental Sciences, Oregon National Primate Research Center, Oregon Health and Science University, Portland, Oregon; Department of Obstetrics and Gynecology, Oregon Health and Science University, Portland, Oregon
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35
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A DTC niche plexus surrounds the germline stem cell pool in Caenorhabditis elegans. PLoS One 2014; 9:e88372. [PMID: 24586318 PMCID: PMC3929564 DOI: 10.1371/journal.pone.0088372] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2013] [Accepted: 01/11/2014] [Indexed: 01/13/2023] Open
Abstract
The mesenchymal distal tip cell (DTC) provides the niche for Caenorhabditis elegans germline stem cells (GSCs). The DTC has a complex cellular architecture: its cell body caps the distal gonadal end and contacts germ cells extensively, but it also includes multiple cellular processes that extend along the germline tube and intercalate between germ cells. Here we use the lag-2 DTC promoter to drive expression of myristoylated GFP, which highlights DTC membranes and permits a more detailed view of DTC architecture. We find that short processes intercalating between germ cells contact more germ cells than seen previously. We define this region of extensive niche contact with germ cells as the DTC plexus. The extent of the DTC plexus corresponds well with the previously determined extent of the GSC pool. Moreover, expression of a differentiation marker increases as germ cells move out of the plexus. Maintenance of this DTC plexus depends on the presence of undifferentiated germ cells, suggesting that germ cell state can influence niche architecture. The roles of this DTC architecture remain an open question. One idea is that the DTC plexus delivers Notch signaling to the cluster of germ cells comprising the GSC pool; another idea is that the plexus anchors GSCs at the distal end.
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36
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Merlet J, Pintard L. Role of the CRL2(LRR-1) E3 ubiquitin-ligase in the development of the germline in C. elegans. WORM 2013; 2:e25716. [PMID: 24778939 PMCID: PMC3875651 DOI: 10.4161/worm.25716] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/05/2013] [Accepted: 07/10/2013] [Indexed: 01/16/2023]
Abstract
The ubiquitin-proteolytic system (UPS) regulates a variety of cellular and biological processes by controlling the stability of regulatory proteins, in space and time. Not surprisingly, defects in this system have been associated with various syndromes and pathologies, including cancer, illustrating the importance of understanding the regulation and the multiple functions of this system. C. elegans is a powerful model system to identify components of the UPS and to study their function during development in multicellular organisms. In C. elegans, the evolutionarily conserved CRL2LRR-1 E3-ligase is critical for the development of the germline. Inactivation of the CUL-2 scaffold or the LRR-1 substrate-recognition subunit leads to a cell cycle arrest in germline stem cells resulting in sterility. Through a genetic screen, we have identified a cul-2 temperature-sensitive allele and we have used this allele to show that CUL-2 plays multiple roles in the development of the germline. CUL-2 (1) promotes germ cell proliferation, (2) influences the balance between mitotic proliferation and meiotic differentiation, and (3) inhibits the first step of meiotic prophase. Here, we discuss how CUL-2 regulates and coordinates these different processes. We suggest that ubiquitin-mediated protein degradation constitutes an important additional layer of regulation that contributes to the spatial organization of the germline.
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Affiliation(s)
- Jorge Merlet
- Institut Jacques Monod; Monod; CNRS; UMR 7592; Univ. Paris Diderot; Sorbonne Paris Cité; F-75205 Paris, France
| | - Lionel Pintard
- Institut Jacques Monod; Monod; CNRS; UMR 7592; Univ. Paris Diderot; Sorbonne Paris Cité; F-75205 Paris, France
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