1
|
Brenner JL, Jyo EM, Mohammad A, Fox P, Jones V, Mardis E, Schedl T, Maine EM. TRIM-NHL protein, NHL-2, modulates cell fate choices in the C. elegans germ line. Dev Biol 2022; 491:43-55. [PMID: 36063869 PMCID: PMC9922029 DOI: 10.1016/j.ydbio.2022.08.010] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2022] [Revised: 07/19/2022] [Accepted: 08/27/2022] [Indexed: 12/01/2022]
Abstract
Many tissues contain multipotent stem cells that are critical for maintaining tissue function. In Caenorhabditis elegans, germline stem cells allow gamete production to continue in adulthood. In the gonad, GLP-1/Notch signaling from the distal tip cell niche to neighboring germ cells activates a complex regulatory network to maintain a stem cell population. GLP-1/Notch signaling positively regulates production of LST-1 and SYGL-1 proteins that, in turn, interact with a set of PUF/FBF proteins to positively regulate the stem cell fate. We previously described sog (suppressor of glp-1 loss of function) and teg (tumorous enhancer of glp-1 gain of function) genes that limit the stem cell fate and/or promote the meiotic fate. Here, we show that sog-10 is allelic to nhl-2. NHL-2 is a member of the conserved TRIM-NHL protein family whose members can bind RNA and ubiquitinate protein substrates. We show that NHL-2 acts, at least in part, by inhibiting the expression of PUF-3 and PUF-11 translational repressor proteins that promote the stem cell fate. Two other negative regulators of stem cell fate, CGH-1 (conserved germline helicase) and ALG-5 (Argonaute protein), may work with NHL-2 to modulate the stem cell population. In addition, NHL-2 activity promotes the male germ cell fate in XX animals.
Collapse
Affiliation(s)
- John L Brenner
- Department of Genetics, Washington University School of Medicine, St. Louis, MO, 63110, USA
| | - Erin M Jyo
- Department of Biology, Syracuse University, Syracuse, NY, 13210, USA
| | - Ariz Mohammad
- Department of Genetics, Washington University School of Medicine, St. Louis, MO, 63110, USA
| | - Paul Fox
- Department of Genetics, Washington University School of Medicine, St. Louis, MO, 63110, USA
| | - Vovanti Jones
- Department of Genetics, Washington University School of Medicine, St. Louis, MO, 63110, USA
| | - Elaine Mardis
- McDonnell Genome Institute, Washington University School of Medicine, St. Louis, MO, 63110, USA
| | - Tim Schedl
- Department of Genetics, Washington University School of Medicine, St. Louis, MO, 63110, USA.
| | - Eleanor M Maine
- Department of Biology, Syracuse University, Syracuse, NY, 13210, USA.
| |
Collapse
|
2
|
Davis GM, Tu S, Anderson JW, Colson RN, Gunzburg MJ, Francisco MA, Ray D, Shrubsole SP, Sobotka JA, Seroussi U, Lao RX, Maity T, Wu MZ, McJunkin K, Morris QD, Hughes TR, Wilce JA, Claycomb JM, Weng Z, Boag PR. The TRIM-NHL protein NHL-2 is a co-factor in the nuclear and somatic RNAi pathways in C. e legans. eLife 2018; 7:35478. [PMID: 30575518 PMCID: PMC6351104 DOI: 10.7554/elife.35478] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2018] [Accepted: 12/20/2018] [Indexed: 12/26/2022] Open
Abstract
Proper regulation of germline gene expression is essential for fertility and maintaining species integrity. In the C. elegans germline, a diverse repertoire of regulatory pathways promote the expression of endogenous germline genes and limit the expression of deleterious transcripts to maintain genome homeostasis. Here we show that the conserved TRIM-NHL protein, NHL-2, plays an essential role in the C. elegans germline, modulating germline chromatin and meiotic chromosome organization. We uncover a role for NHL-2 as a co-factor in both positively (CSR-1) and negatively (HRDE-1) acting germline 22G-small RNA pathways and the somatic nuclear RNAi pathway. Furthermore, we demonstrate that NHL-2 is a bona fide RNA binding protein and, along with RNA-seq data point to a small RNA independent role for NHL-2 in regulating transcripts at the level of RNA stability. Collectively, our data implicate NHL-2 as an essential hub of gene regulatory activity in both the germline and soma.
Collapse
Affiliation(s)
- Gregory M Davis
- Development and Stem Cells Program, Monash Biomedicine Discovery Institute, Monash University, Melbourne, Australia.,Department of Biochemistry and Molecular Biology, Monash University, Melbourne, Australia.,School of Health and Life Sciences, Federation University, Victoria, Australia
| | - Shikui Tu
- Program in Bioinformatics and Integrative Biology, University of Massachusetts Medical School, Worcester, United States
| | - Joshua Wt Anderson
- Development and Stem Cells Program, Monash Biomedicine Discovery Institute, Monash University, Melbourne, Australia.,Department of Biochemistry and Molecular Biology, Monash University, Melbourne, Australia
| | - Rhys N Colson
- Development and Stem Cells Program, Monash Biomedicine Discovery Institute, Monash University, Melbourne, Australia.,Department of Biochemistry and Molecular Biology, Monash University, Melbourne, Australia
| | - Menachem J Gunzburg
- Development and Stem Cells Program, Monash Biomedicine Discovery Institute, Monash University, Melbourne, Australia.,Department of Biochemistry and Molecular Biology, Monash University, Melbourne, Australia
| | | | - Debashish Ray
- Department of Molecular Genetics, University of Toronto, Toronto, Canada
| | - Sean P Shrubsole
- Development and Stem Cells Program, Monash Biomedicine Discovery Institute, Monash University, Melbourne, Australia.,Department of Biochemistry and Molecular Biology, Monash University, Melbourne, Australia
| | - Julia A Sobotka
- Department of Molecular Genetics, University of Toronto, Toronto, Canada
| | - Uri Seroussi
- Department of Molecular Genetics, University of Toronto, Toronto, Canada
| | - Robert X Lao
- Department of Molecular Genetics, University of Toronto, Toronto, Canada
| | - Tuhin Maity
- Department of Molecular Genetics, University of Toronto, Toronto, Canada
| | - Monica Z Wu
- Department of Molecular Genetics, University of Toronto, Toronto, Canada
| | - Katherine McJunkin
- Laboratory of Cellular and Developmental Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, United States
| | - Quaid D Morris
- Department of Molecular Genetics, University of Toronto, Toronto, Canada
| | - Timothy R Hughes
- Department of Molecular Genetics, University of Toronto, Toronto, Canada
| | - Jacqueline A Wilce
- Development and Stem Cells Program, Monash Biomedicine Discovery Institute, Monash University, Melbourne, Australia.,Department of Biochemistry and Molecular Biology, Monash University, Melbourne, Australia
| | - Julie M Claycomb
- Department of Molecular Genetics, University of Toronto, Toronto, Canada
| | - Zhiping Weng
- Program in Bioinformatics and Integrative Biology, University of Massachusetts Medical School, Worcester, United States
| | - Peter R Boag
- Development and Stem Cells Program, Monash Biomedicine Discovery Institute, Monash University, Melbourne, Australia.,Department of Biochemistry and Molecular Biology, Monash University, Melbourne, Australia
| |
Collapse
|
3
|
Wu E, Vashisht AA, Chapat C, Flamand MN, Cohen E, Sarov M, Tabach Y, Sonenberg N, Wohlschlegel J, Duchaine TF. A continuum of mRNP complexes in embryonic microRNA-mediated silencing. Nucleic Acids Res 2018; 45:2081-2098. [PMID: 28204614 PMCID: PMC5389717 DOI: 10.1093/nar/gkw872] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2016] [Revised: 09/21/2016] [Accepted: 09/28/2016] [Indexed: 12/12/2022] Open
Abstract
MicroRNAs (miRNAs) impinge on the translation and stability of their target mRNAs, and play key roles in development, homeostasis and disease. The gene regulation mechanisms they instigate are largely mediated through the CCR4–NOT deadenylase complex, but the molecular events that occur on target mRNAs are poorly resolved. We observed a broad convergence of interactions of germ granule and P body mRNP components on AIN-1/GW182 and NTL-1/CNOT1 in Caenorhabditis elegans embryos. We show that the miRISC progressively matures on the target mRNA from a scanning form into an effector mRNP particle by sequentially recruiting the CCR4–NOT complex, decapping and decay, or germ granule proteins. Finally, we implicate intrinsically disordered proteins, key components in mRNP architectures, in the embryonic function of lsy-6 miRNA. Our findings define dynamic steps of effector mRNP assembly in miRNA-mediated silencing, and identify a functional continuum between germ granules and P bodies in the C. elegans embryo.
Collapse
Affiliation(s)
| | - Ajay A Vashisht
- Department of Biological Chemistry, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA
| | - Clément Chapat
- Department of Biochemistry and Goodman Cancer Research Centre, McGill University, Montreal, Quebec, H3G 1Y6 Canada
| | - Mathieu N Flamand
- Department of Biochemistry and Goodman Cancer Research Centre, McGill University, Montreal, Quebec, H3G 1Y6 Canada
| | - Emiliano Cohen
- Department of Developmental Biology and Cancer Research, The Institute For Medical Research-Israel-Canada, The Hebrew University Hadassah Medical School, Jerusalem 91120, Israel
| | - Mihail Sarov
- Max Planck Institute of Molecular Cell Biology and Genetics, Dresden 01307, Germany
| | - Yuval Tabach
- Department of Developmental Biology and Cancer Research, The Institute For Medical Research-Israel-Canada, The Hebrew University Hadassah Medical School, Jerusalem 91120, Israel
| | - Nahum Sonenberg
- Department of Biochemistry and Goodman Cancer Research Centre, McGill University, Montreal, Quebec, H3G 1Y6 Canada
| | - James Wohlschlegel
- Department of Biological Chemistry, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA
| | | |
Collapse
|
4
|
Exploring Potential Germline-Associated Roles of the TRIM-NHL Protein NHL-2 Through RNAi Screening. G3-GENES GENOMES GENETICS 2017; 7:3251-3256. [PMID: 28818867 PMCID: PMC5633376 DOI: 10.1534/g3.117.300166] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
TRIM-NHL proteins are highly conserved regulators of developmental pathways in vertebrates and invertebrates. The TRIM-NHL family member NHL-2 in Caenorhabditis elegans functions as a miRNA cofactor to regulate developmental timing. Similar regulatory roles have been reported in other model systems, with the mammalian ortholog in mice, TRIM32, contributing to muscle and neuronal cell proliferation via miRNA activity. Given the interest associated with TRIM-NHL family proteins, we aimed to further investigate the role of NHL-2 in C. elegans development by using a synthetic RNAi screening approach. Using the ORFeome library, we knocked down 11,942 genes in wild-type animals and nhl-2 null mutants. In total, we identified 42 genes that produced strong reproductive synthetic phenotypes when knocked down in nhl-2 null mutants, with little or no change when knocked down in wild-type animals. These included genes associated with transcriptional processes, chromosomal integrity, and key cofactors of the germline small 22G RNA pathway.
Collapse
|
5
|
McJunkin K, Ambros V. A microRNA family exerts maternal control on sex determination in C. elegans. Genes Dev 2017; 31:422-437. [PMID: 28279983 PMCID: PMC5358761 DOI: 10.1101/gad.290155.116] [Citation(s) in RCA: 45] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2016] [Accepted: 02/06/2017] [Indexed: 12/29/2022]
Abstract
Gene expression in early animal embryogenesis is in large part controlled post-transcriptionally. Maternally contributed microRNAs may therefore play important roles in early development. We elucidated a major biological role of the nematode mir-35 family of maternally contributed essential microRNAs. We show that this microRNA family regulates the sex determination pathway at multiple levels, acting both upstream of and downstream from her-1 to prevent aberrantly activated male developmental programs in hermaphrodite embryos. Both of the predicted target genes that act downstream from the mir-35 family in this process, suppressor-26 (sup-26) and NHL (NCL-1, HT2A, and LIN-41 repeat) domain-containing-2 (nhl-2), encode RNA-binding proteins, thus delineating a previously unknown post-transcriptional regulatory subnetwork within the well-studied sex determination pathway of Caenorhabditis elegans Repression of nhl-2 by the mir-35 family is required for not only proper sex determination but also viability, showing that a single microRNA target site can be essential. Since sex determination in C. elegans requires zygotic gene expression to read the sex chromosome karyotype, early embryos must remain gender-naïve; our findings show that the mir-35 family microRNAs act in the early embryo to function as a developmental timer that preserves naïveté and prevents premature deleterious developmental decisions.
Collapse
Affiliation(s)
- Katherine McJunkin
- Program in Molecular Medicine, RNA Therapeutics Institute, University of Massachusetts Medical School, Worcester, Massachusetts 01605, USA
| | - Victor Ambros
- Program in Molecular Medicine, RNA Therapeutics Institute, University of Massachusetts Medical School, Worcester, Massachusetts 01605, USA
| |
Collapse
|
6
|
Rabilotta A, Desrosiers M, Labbé JC. CDK-1 and two B-type cyclins promote PAR-6 stabilization during polarization of the early C. elegans embryo. PLoS One 2015; 10:e0117656. [PMID: 25658117 PMCID: PMC4319824 DOI: 10.1371/journal.pone.0117656] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2014] [Accepted: 12/30/2014] [Indexed: 01/08/2023] Open
Abstract
In the C. elegans embryo, formation of an antero-posterior axis of polarity relies on signaling by the conserved PAR proteins, which localize asymmetrically in two mutually exclusive groups at the embryonic cortex. Depletion of any PAR protein causes a loss of polarity and embryonic lethality. A genome-wide RNAi screen previously identified two B-type cyclins, cyb-2.1 and cyb-2.2, as suppressors of par-2(it5ts) lethality. We found that the loss of cyb-2.1 or cyb-2.2 suppressed the lethality and polarity defects of par-2(it5ts) mutants and that these cyclins act in cell polarity with their cyclin-dependent kinase partner, CDK-1. Interestingly, cyb-2.1; cyb-2.2 double mutants did not show defects in cell cycle progression or timing of polarity establishment, suggesting that they regulate polarity independently of their typical role in cell cycle progression. Loss of both cyclin genes or of cdk-1 resulted in a decrease in PAR-6 levels in the embryo. Furthermore, the activity of the cullin CUL-2 was required to achieve suppression of par-2 lethality when both cyclins were absent. Our results support a model in which CYB-2.1/2/CDK-1 antagonize CUL-2 activity to promote stabilization of PAR-6 levels during polarization of the early C. elegans embryo. They also suggest that CYB-2.1 and CYB-2.2 contribute to the coupling of cell cycle progression and asymmetric segregation of cell fate determinants.
Collapse
Affiliation(s)
- Alexia Rabilotta
- Institute of Research in Immunology and Cancer (IRIC), Université de Montréal, Montréal, Quebec, Canada
| | - Marianne Desrosiers
- Institute of Research in Immunology and Cancer (IRIC), Université de Montréal, Montréal, Quebec, Canada
| | - Jean-Claude Labbé
- Institute of Research in Immunology and Cancer (IRIC), Université de Montréal, Montréal, Quebec, Canada
- Department of Pathology and Cell Biology, Université de Montréal, Montréal, Quebec, Canada
- * E-mail:
| |
Collapse
|
7
|
Benkemoun L, Descoteaux C, Chartier NT, Pintard L, Labbé JC. PAR-4/LKB1 regulates DNA replication during asynchronous division of the early C. elegans embryo. ACTA ACUST UNITED AC 2014; 205:447-55. [PMID: 24841566 PMCID: PMC4033775 DOI: 10.1083/jcb.201312029] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
DNA replication is asymmetrically regulated in the two-cell stage C. elegans embryo by the PAR-4 and PAR-1 polarity proteins, which function independently of known regulators of cell cycle timing to dampen DNA replication dynamics specifically in the posterior blastomere. Regulation of cell cycle duration is critical during development, yet the underlying molecular mechanisms are still poorly understood. The two-cell stage Caenorhabditis elegans embryo divides asynchronously and thus provides a powerful context in which to study regulation of cell cycle timing during development. Using genetic analysis and high-resolution imaging, we found that deoxyribonucleic acid (DNA) replication is asymmetrically regulated in the two-cell stage embryo and that the PAR-4 and PAR-1 polarity proteins dampen DNA replication dynamics specifically in the posterior blastomere, independently of regulators previously implicated in the control of cell cycle timing. Our results demonstrate that accurate control of DNA replication is crucial during C. elegans early embryonic development and further provide a novel mechanism by which PAR proteins control cell cycle progression during asynchronous cell division.
Collapse
Affiliation(s)
- Laura Benkemoun
- Cell Division and Differentiation Laboratory, Institute of Research in Immunology and Cancer, and Department of Pathology and Cell Biology, Université de Montréal, Montréal, Québec H3T 1J4, Canada
| | - Catherine Descoteaux
- Cell Division and Differentiation Laboratory, Institute of Research in Immunology and Cancer, and Department of Pathology and Cell Biology, Université de Montréal, Montréal, Québec H3T 1J4, Canada
| | - Nicolas T Chartier
- Cell Division and Differentiation Laboratory, Institute of Research in Immunology and Cancer, and Department of Pathology and Cell Biology, Université de Montréal, Montréal, Québec H3T 1J4, Canada
| | - Lionel Pintard
- Institut Jacques Monod, Centre National de la Recherche Scientifique and Université Paris Diderot, F-75013 Paris, France
| | - Jean-Claude Labbé
- Cell Division and Differentiation Laboratory, Institute of Research in Immunology and Cancer, and Department of Pathology and Cell Biology, Université de Montréal, Montréal, Québec H3T 1J4, CanadaCell Division and Differentiation Laboratory, Institute of Research in Immunology and Cancer, and Department of Pathology and Cell Biology, Université de Montréal, Montréal, Québec H3T 1J4, Canada
| |
Collapse
|
8
|
Beatty A, Morton DG, Kemphues K. PAR-2, LGL-1 and the CDC-42 GAP CHIN-1 act in distinct pathways to maintain polarity in the C. elegans embryo. Development 2013; 140:2005-14. [PMID: 23536568 DOI: 10.1242/dev.088310] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
In the one-cell C. elegans embryo, polarity is maintained by mutual antagonism between the anterior cortical proteins PAR-3, PKC-3, PAR-6 and CDC-42, and the posterior cortical proteins PAR-2 and LGL-1 on the posterior cortex. The mechanisms by which these proteins interact to maintain polarity are incompletely understood. In this study, we investigate the interplay among PAR-2, LGL-1, myosin, the anterior PAR proteins and CDC-42. We find that PAR-2 and LGL-1 affect cortical myosin accumulation by different mechanisms. LGL-1 does not directly antagonize the accumulation of cortical myosin and instead plays a role in regulating PAR-6 levels. By contrast, PAR-2 likely has separate roles in regulating cortical myosin accumulation and preventing the expansion of the anterior cortical domain. We also provide evidence that asymmetry of active CDC-42 can be maintained independently of LGL-1 and PAR-2 by a redundant pathway that includes the CDC-42 GAP CHIN-1. Finally, we show that, in addition to its primary role in regulating the size of the anterior cortical domain via its binding to PAR-6, CDC-42 has a secondary role in regulating cortical myosin that is not dependent on PAR-6.
Collapse
Affiliation(s)
- Alexander Beatty
- Department of Molecular Biology and Genetics, Cornell University, 433 Biotechnology Building, Ithaca, NY 14853, USA
| | | | | |
Collapse
|
9
|
Hirth F. Stem Cells and Asymmetric Cell Division. Regen Med 2013. [DOI: 10.1007/978-94-007-5690-8_4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
|
10
|
Deubiquitylation machinery is required for embryonic polarity in Caenorhabditis elegans. PLoS Genet 2012; 8:e1003092. [PMID: 23209443 PMCID: PMC3510043 DOI: 10.1371/journal.pgen.1003092] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2012] [Accepted: 10/01/2012] [Indexed: 11/19/2022] Open
Abstract
The Caenorhabditis elegans one-cell embryo polarizes in response to a cue from the paternally donated centrosome and asymmetrically segregates cell fate determinants that direct the developmental program of the worm. We have found that genes encoding putative deubiquitylating enzymes (DUBs) are required for polarization of one-cell embryos. Maternal loss of the proteins MATH-33 and USP-47 leads to variable inability to correctly establish and maintain asymmetry as defined by posterior and anterior polarity proteins PAR-2 and PAR-3. The first observable defect is variable positioning of the centrosome with respect to the cell cortex and the male pronucleus. The severity of the polarity defects correlates with distance of the centrosome from the cortex. Furthermore, polarity defects can be bypassed by mutations that bring the centrosome in close proximity to the cortex. In addition we find that polarity and centrosome positioning defects can be suppressed by compromising protein turnover. We propose that the DUB activity of MATH-33 and USP-47 stabilizes one or more proteins required for association of the centrosome with the cortex. Because these DUBs are homologous to two members of a group of DUBs that act in fission yeast polarity, we tested additional members of that family and found that another C. elegans DUB gene, usp-46, also contributes to polarity. Our finding that deubiquitylating enzymes required for polarity in Schizosaccharomyces pombe are also required in C. elegans raises the possibility that these DUBs act through an evolutionarily conserved mechanism to control cell polarity. In eukaryotes, modification of proteins by the covalent ligation of a protein called ubiquitin is an important regulatory mechanism. In this study we found that deubiquitylation enzymes, which are known to cleave ubiquitin off of target proteins, are required for asymmetry in one-cell embryos of the nematode C. elegans. In one-cell embryos the establishment of asymmetry depends on a signal from the centrosome, a microtubule-organizing center. This signal breaks homogeneity in the contractile cytoskeleton located at the cortex of the embryo. We have identified three deubiquitylation enzymes that are necessary for the centrosome to properly localize adjacent to the cortex to perform its symmetry-breaking role. Furthermore, a homologous group of enzymes in fission yeast also regulates cell polarity. Our results suggest that a novel mechanism of centrosome localization regulated by ubiquitylation exists in C. elegans; this mechanism is masked by genetic redundancy and may be an evolutionarily conserved mechanism for cell asymmetry.
Collapse
|
11
|
Karp X, Ambros V. Dauer larva quiescence alters the circuitry of microRNA pathways regulating cell fate progression in C. elegans. Development 2012; 139:2177-86. [PMID: 22619389 DOI: 10.1242/dev.075986] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
In C. elegans larvae, the execution of stage-specific developmental events is controlled by heterochronic genes, which include those encoding a set of transcription factors and the microRNAs that regulate the timing of their expression. Under adverse environmental conditions, developing larvae enter a stress-resistant, quiescent stage called 'dauer'. Dauer larvae are characterized by the arrest of all progenitor cell lineages at a stage equivalent to the end of the second larval stage (L2). If dauer larvae encounter conditions favorable for resumption of reproductive growth, they recover and complete development normally, indicating that post-dauer larvae possess mechanisms to accommodate an indefinite period of interrupted development. For cells to progress to L3 cell fate, the transcription factor Hunchback-like-1 (HBL-1) must be downregulated. Here, we describe a quiescence-induced shift in the repertoire of microRNAs that regulate HBL-1. During continuous development, HBL-1 downregulation (and consequent cell fate progression) relies chiefly on three let-7 family microRNAs, whereas after quiescence, HBL-1 is downregulated primarily by the lin-4 microRNA in combination with an altered set of let-7 family microRNAs. We propose that this shift in microRNA regulation of HBL-1 expression involves an enhancement of the activity of lin-4 and let-7 microRNAs by miRISC modulatory proteins, including NHL-2 and LIN-46. These results illustrate how the employment of alternative genetic regulatory pathways can provide for the robust progression of progenitor cell fates in the face of temporary developmental quiescence.
Collapse
Affiliation(s)
- Xantha Karp
- Program in Molecular Medicine, University of Massachusetts Medical School, Worcester, MA 01605, USA
| | | |
Collapse
|
12
|
RAB-5 controls the cortical organization and dynamics of PAR proteins to maintain C. elegans early embryonic polarity. PLoS One 2012; 7:e35286. [PMID: 22545101 PMCID: PMC3335856 DOI: 10.1371/journal.pone.0035286] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2012] [Accepted: 03/14/2012] [Indexed: 11/19/2022] Open
Abstract
In all organisms, cell polarity is fundamental for most aspects of cell physiology. In many species and cell types, it is controlled by the evolutionarily conserved PAR-3, PAR-6 and aPKC proteins, which are asymmetrically localized at the cell cortex where they define specific domains. While PAR proteins define the antero-posterior axis of the early C. elegans embryo, the mechanism controlling their asymmetric localization is not fully understood. Here we studied the role of endocytic regulators in embryonic polarization and asymmetric division. We found that depleting the early endosome regulator RAB-5 results in polarity-related phenotypes in the early embryo. Using Total Internal Reflection Fluorescence (TIRF) microscopy, we observed that PAR-6 is localized at the cell cortex in highly dynamic puncta and depleting RAB-5 decreased PAR-6 cortical dynamics during the polarity maintenance phase. Depletion of RAB-5 also increased PAR-6 association with clathrin heavy chain (CHC-1) and this increase depended on the presence of the GTPase dynamin, an upstream regulator of endocytosis. Interestingly, further analysis indicated that loss of RAB-5 leads to a disorganization of the actin cytoskeleton and that this occurs independently of dynamin activity. Our results indicate that RAB-5 promotes C. elegans embryonic polarity in both dynamin-dependent and -independent manners, by controlling PAR-6 localization and cortical dynamics through the regulation of its association with the cell cortex and the organization of the actin cytoskeleton.
Collapse
|
13
|
Hirth F. Stem Cells and Asymmetric Cell Division. Regen Med 2011. [DOI: 10.1007/978-90-481-9075-1_4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
|
14
|
Hyenne V, Chartier NT, Labbé JC. Understanding the role of asymmetric cell division in cancer using C. elegans. Dev Dyn 2010; 239:1378-87. [PMID: 20140912 DOI: 10.1002/dvdy.22237] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Asymmetric cell division is an important process to generate cell diversity and maintain tissue homeostasis. Recent evidence suggests that this process may also be crucial to prevent tumor formation. In the past 30 years, the embryo of the nematode Caenorhabditis elegans has proven to be a very powerful model to study the molecular and cellular basis of asymmetric cell division. Understanding this process in Caenorhabditis elegans may thus lead to a better understanding of stem cell function and tumorigenesis in humans.
Collapse
Affiliation(s)
- Vincent Hyenne
- Laboratory of Cell Division and Differentiation, Department of Pathology and Cell Biology, Institute of Research in Immunology and Cancer (IRIC), Université de Montréal, Montréal, Quebec, Canada.
| | | | | |
Collapse
|
15
|
Hwang SY, Rose LS. Control of asymmetric cell division in early C. elegans embryogenesis: teaming-up translational repression and protein degradation. BMB Rep 2010; 43:69-78. [PMID: 20193124 DOI: 10.5483/bmbrep.2010.43.2.069] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Asymmetric cell division is a fundamental mechanism for the generation of body axes and cell diversity during early embryogenesis in many organisms. During intrinsically asymmetric divisions, an axis of polarity is established within the cell and the division plane is oriented to ensure the differential segregation of developmental determinants to the daughter cells. Studies in the nematode Caenorhabditis elegans have contributed greatly to our understanding of the regulatory mechanisms underlying cell polarity and asymmetric division. However, much remains to be elucidated about the molecular machinery controlling the spatiotemporal distribution of key components. In this review we discuss recent findings that reveal intricate interactions between translational control and targeted proteolysis. These two mechanisms of regulation serve to carefully modulate protein levels and reinforce asymmetries, or to eliminate proteins from certain cells.
Collapse
Affiliation(s)
- Sue-Yun Hwang
- Department of Molecular and Cellular Biology, University of California, Davis, CA 95616, USA
| | | |
Collapse
|
16
|
Chartier NT, Hyenne V, Labbé JC. [Mechanisms of asymmetric cell division: from model organisms to tumorigenesis]. Med Sci (Paris) 2010; 26:251-7. [PMID: 20346274 DOI: 10.1051/medsci/2010263251] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
Asymmetric cell division is the process by which a single cell gives rise to two different daughter cells. This process is important to generate cell diversity during the development of multicellular organisms, as well as for stem cell self-renewal in adults. Current knowledge on so-called cancer stem cells suggests that a loss of asymmetry during their division could lead to overproliferation and favour tumorigenesis, highlighting the importance of deciphering the mechanisms governing asymmetric cell division. Two mechanisms can lead to an asymmetric cell division: asymmetry can either be governed by proximity to a given cellular environment (or niche), in which case the mechanism is referred to as extrinsic, or the mother cell polarizes itself without external intervention, in which case the mechanism is referred to as intrinsic. In the last 20 years, our understanding of intrinsic mechanisms leading to asymmetric cell division has progressed, largely after studies carried out in model organisms such as the nematode Caenorhabditis elegans and the fruit fly Drosophila melanogaster. These models allowed the identification of molecular complexes used by nearly all the cells that divide asymmetrically, including human cells. Here we review the main intrinsic mechanisms of asymmetric cell division as described in model organisms and discuss their relevance towards mammalian tumorigenesis.
Collapse
Affiliation(s)
- Nicolas T Chartier
- Unité de recherche en division et différenciation cellulaire, Institut de recherche en immunologie et en cancérologie, Université de Montréal, CP 6128, Succursale Centre-ville, Montréal (Québec), Canada H3C 3J7.
| | | | | |
Collapse
|
17
|
Narbonne P, Hyenne V, Li S, Labbé JC, Roy R. Differential requirements for STRAD in LKB1-dependent functions in C. elegans. Development 2010; 137:661-70. [DOI: 10.1242/dev.042044] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The protein kinase LKB1 is a crucial regulator of cell growth/proliferation and cell polarity and is the causative gene in the cancer-predisposing disease Peutz-Jeghers syndrome (PJS). The activity of LKB1 is greatly enhanced following its association with the Ste20-like adapter protein STRAD. Unlike LKB1 however, mutations in STRAD have not been identified in PJS patients and thus, the key tumour suppressive role(s) of LKB1 might be STRAD independent. Here, we report that Caenorhabditis elegans strd-1/STRAD mutants recapitulate many phenotypes typical of par-4/LKB1 loss of function, showing defects during early embryonic and dauer development. Interestingly, although the growth/proliferation defects in severe par-4 and strd-1 mutant dauers are comparable, strd-1 mutant embryos do not share the polarity defects of par-4 embryos. We demonstrate that most of par-4-dependent regulation of germline stem cell (GSC) quiescence occurs through AMPK, whereby PAR-4 requires STRD-1 to phosphorylate and activate AMPK. Consistent with this, even though AMPK plays a major role in the regulation of cell proliferation, like strd-1 it does not affect embryonic polarity. Instead, we found that the PAR-4-mediated phosphorylation of polarity regulators such as PAR-1 and MEX-5 in the early embryo occurs in the absence of STRD-1. Thus, PAR-4 requires STRD-1 to phosphorylate AMPK to regulate cell growth/proliferation under reduced insulin signalling conditions, whereas PAR-4 can promote phosphorylation of key proteins, including PAR-1 and MEX-5, to specify early embryonic polarity independently of STRD-1. Our results therefore identify a key strd-1/STRAD-independent function of par-4/LKB1 in polarity establishment that is likely to be important for tumour suppression in humans.
Collapse
Affiliation(s)
- Patrick Narbonne
- Department of Biology, McGill University, Montréal, H3A 1B1 Québec, Canada
| | - Vincent Hyenne
- Institut de recherche en immunologie et cancérologie (IRIC), Université de Montréal, Montréal, H3C 3J7 Québec, Canada
| | - Shaolin Li
- Department of Biology, McGill University, Montréal, H3A 1B1 Québec, Canada
| | - Jean-Claude Labbé
- Institut de recherche en immunologie et cancérologie (IRIC), Université de Montréal, Montréal, H3C 3J7 Québec, Canada
- Department of Pathology and Cell Biology, Université de Montréal. Montréal, H3C 3J7 Québec, Canada
| | - Richard Roy
- Department of Biology, McGill University, Montréal, H3A 1B1 Québec, Canada
| |
Collapse
|
18
|
|