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Robinson J, Teuliere J, Yoo S, Garriga G. NMY-2, TOE-2 and PIG-1 regulate Caenorhabditis elegans asymmetric cell divisions. PLoS One 2024; 19:e0304064. [PMID: 38787850 PMCID: PMC11125515 DOI: 10.1371/journal.pone.0304064] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2023] [Accepted: 05/06/2024] [Indexed: 05/26/2024] Open
Abstract
Asymmetric cell division is an important mechanism that generates cellular diversity during development. Not only do asymmetric cell divisions produce daughter cells of different fates, but many can also produce daughters of different sizes, which we refer to as Daughter Cell Size Asymmetry (DCSA). In Caenorhabditis elegans, apoptotic cells are frequently produced by asymmetric divisions that exhibit DCSA, where the smaller daughter dies. We focus here on the divisions of the Q.a and Q.p neuroblasts, which produce larger surviving cells and smaller apoptotic cells and divide with opposite polarity using both distinct and overlapping mechanisms. Several proteins regulate DCSA in these divisions. Previous studies showed that the PIG-1/MELK and TOE-2 proteins regulate DCSA in both the Q.a and Q.p divisions, and the non-muscle myosin NMY-2 regulates DCSA in the Q.a division but not the Q.p division. In this study, we examined endogenously tagged NMY-2, TOE-2, and PIG-1 reporters and characterized their distribution at the cortex during the Q.a and Q.p divisions. In both divisions, TOE-2 localized toward the side of the dividing cell that produced the smaller daughter, whereas PIG-1 localized toward the side that produced the larger daughter. As previously reported, NMY-2 localized to the side of Q.a that produced the smaller daughter and did not localize asymmetrically in Q.p. We used temperature-sensitive nmy-2 mutants to determine the role of nmy-2 in these divisions and were surprised to find that these mutants only displayed DCSA defects in the Q.p division. We generated double mutant combinations between the nmy-2 mutations and mutations in toe-2 and pig-1. Because previous studies indicate that DCSA defects result in the transformation of cells fated to die into their sister cells, the finding that the nmy-2 mutations did not significantly alter the Q.a and Q.p DCSA defects of toe-2 and pig-1 mutants but did alter the number of daughter cells produced by Q.a and Q.p suggests that nmy-2 plays a role in specifying the fates of the Q.a and Q.p that is independent of its role in DCSA.
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Affiliation(s)
- Joseph Robinson
- Department of Molecular and Cell Biology, University of California Berkeley, Berkeley, CA, United States of America
| | - Jerome Teuliere
- Department of Molecular and Cell Biology, University of California Berkeley, Berkeley, CA, United States of America
| | - Shinja Yoo
- Department of Molecular and Cell Biology, University of California Berkeley, Berkeley, CA, United States of America
| | - Gian Garriga
- Department of Molecular and Cell Biology, University of California Berkeley, Berkeley, CA, United States of America
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2
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Lamb H, Liro MJ, Myles KM, Fernholz M, Anderson HA, Rose LS. The Rac1 homolog CED-10 is a component of the MES-1/SRC-1 pathway for asymmetric division of the C. elegans EMS blastomere. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.04.04.588162. [PMID: 38645195 PMCID: PMC11030239 DOI: 10.1101/2024.04.04.588162] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/23/2024]
Abstract
Asymmetric cell division is essential for the creation of cell types with different identities and functions. The EMS blastomere of the four-cell Caenorhabditis elegans embryo undergoes an asymmetric division in response to partially redundant signaling pathways. One pathway involves a Wnt signal emanating from the neighboring P2 cell, while the other pathway is defined by the receptor-like MES-1 protein localized at the EMS/P2 cell contact, and the cytoplasmic kinase SRC-1. In response to these pathways, the EMS nuclear-centrosome complex rotates so that the spindle forms on the anterior-posterior axis; after division, the daughter cell contacting P2 becomes the endodermal precursor cell. Here we identify the Rac1 homolog, CED-10, as a new component of the MES-1/SRC-1 pathway. Loss of CED-10 affects both spindle positioning and endoderm specification. Although MES-1 is still present at the EMS/P2 contact in ced-10 embryos, SRC-1 dependent phosphorylation is reduced. These and other results suggest that CED-10 acts downstream of MES-1 and upstream or at the level of SRC-1 activity. In addition, we find that the branched actin regulator ARX-2 is enriched at the EMS/P2 cell contact site, in a CED-10 dependent manner. Loss of ARX-2 results in spindle positioning defects, suggesting that CED-10 acts through branched actin to promote the asymmetric division of the EMS cell.
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3
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Stolpner NJ, Manzi NI, Su T, Dickinson DJ. Apical PAR protein caps orient the mitotic spindle in C. elegans early embryos. Curr Biol 2023; 33:4312-4329.e6. [PMID: 37729910 PMCID: PMC10615879 DOI: 10.1016/j.cub.2023.08.069] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2023] [Revised: 07/24/2023] [Accepted: 08/23/2023] [Indexed: 09/22/2023]
Abstract
During embryonic development, oriented cell divisions are important for patterned tissue growth and cell fate specification. Cell division orientation is controlled in part by asymmetrically localized polarity proteins, which establish functional domains of the cell membrane and interact with microtubule regulators to position the mitotic spindle. For example, in the 8-cell mouse embryo, apical polarity proteins form caps on the outside, contact-free surface of the embryo that position the mitotic spindle to execute asymmetric cell division. A similar radial or "inside-outside" polarity is established at an early stage in many other animal embryos, but in most cases, it remains unclear how inside-outside polarity is established and how it influences downstream cell behaviors. Here, we explore inside-outside polarity in C. elegans somatic blastomeres using spatiotemporally controlled protein degradation and live embryo imaging. We show that PAR polarity proteins, which form apical caps at the center of the contact-free membrane, localize dynamically during the cell cycle and contribute to spindle orientation and proper cell positioning. Surprisingly, isolated single blastomeres lacking cell contacts are able to break symmetry and form PAR-3/atypical protein kinase C (aPKC) caps. Polarity caps form independently of actomyosin flows and microtubules and can regulate spindle orientation in cooperation with the key polarity kinase aPKC. Together, our results reveal a role for apical polarity caps in regulating spindle orientation in symmetrically dividing cells and provide novel insights into how these structures are formed.
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Affiliation(s)
- Naomi J Stolpner
- Department of Molecular Biosciences, The University of Texas at Austin, 2415 Speedway, PAT 206, Austin, TX 78712, USA
| | - Nadia I Manzi
- Department of Molecular Biosciences, The University of Texas at Austin, 2415 Speedway, PAT 206, Austin, TX 78712, USA
| | - Thomas Su
- Department of Molecular Biosciences, The University of Texas at Austin, 2415 Speedway, PAT 206, Austin, TX 78712, USA
| | - Daniel J Dickinson
- Department of Molecular Biosciences, The University of Texas at Austin, 2415 Speedway, PAT 206, Austin, TX 78712, USA.
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4
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Stolpner NJ, Manzi NI, Su T, Dickinson DJ. Apical PAR-3 caps orient the mitotic spindle in C. elegans early embryos. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.03.27.534341. [PMID: 37034756 PMCID: PMC10081169 DOI: 10.1101/2023.03.27.534341] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 05/14/2023]
Abstract
During embryonic development, oriented cell divisions are important for patterned tissue growth and cell fate specification. Cell division orientation is controlled in part by asymmetrically localized polarity proteins, which establish functional domains of the cell membrane and interact with microtubule regulators to position the mitotic spindle. For example, in the 8-cell mouse embryo, apical polarity proteins form caps on the outside, contact-free surface of the embryo that position the mitotic spindle to execute asymmetric cell division. A similar radial or "inside-outside" polarity is established at an early stage in many other animal embryos, but in most cases it remains unclear how inside-outside polarity is established and how it influences downstream cell behaviors. Here, we explore inside-outside polarity in C. elegans somatic blastomeres using spatiotemporally controlled protein degradation and live embryo imaging. We show that PAR polarity proteins, which form apical caps at the center of the contact free membrane, localize dynamically during the cell cycle and contribute to spindle orientation and proper cell positioning. Surprisingly, apical PAR-3 can form polarity caps independently of actomyosin flows and the small GTPase CDC-42, and can regulate spindle orientation in cooperation with the key polarity kinase aPKC. Together, our results reveal a role for apical polarity caps in regulating spindle orientation in symmetrically dividing cells and provide novel insights into how these structures are formed.
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Affiliation(s)
- Naomi J. Stolpner
- Department of Molecular Biosciences, The University of Texas at Austin, 2415 Speedway, PAT 206, Austin, TX 78712
| | - Nadia I. Manzi
- Department of Molecular Biosciences, The University of Texas at Austin, 2415 Speedway, PAT 206, Austin, TX 78712
| | - Thomas Su
- Department of Molecular Biosciences, The University of Texas at Austin, 2415 Speedway, PAT 206, Austin, TX 78712
| | - Daniel J. Dickinson
- Department of Molecular Biosciences, The University of Texas at Austin, 2415 Speedway, PAT 206, Austin, TX 78712
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5
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Jankele R, Jelier R, Gönczy P. Physically asymmetric division of the C. elegans zygote ensures invariably successful embryogenesis. eLife 2021; 10:e61714. [PMID: 33620314 PMCID: PMC7972452 DOI: 10.7554/elife.61714] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2020] [Accepted: 02/22/2021] [Indexed: 12/17/2022] Open
Abstract
Asymmetric divisions that yield daughter cells of different sizes are frequent during early embryogenesis, but the importance of such a physical difference for successful development remains poorly understood. Here, we investigated this question using the first division of Caenorhabditis elegans embryos, which yields a large AB cell and a small P1 cell. We equalized AB and P1 sizes using acute genetic inactivation or optogenetic manipulation of the spindle positioning protein LIN-5. We uncovered that only some embryos tolerated equalization, and that there was a size asymmetry threshold for viability. Cell lineage analysis of equalized embryos revealed an array of defects, including faster cell cycle progression in P1 descendants, as well as defects in cell positioning, division orientation, and cell fate. Moreover, equalized embryos were more susceptible to external compression. Overall, we conclude that unequal first cleavage is essential for invariably successful embryonic development of C. elegans.
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Affiliation(s)
- Radek Jankele
- Swiss Institute for Experimental Cancer Research (ISREC), School of Life Sciences, Swiss Federal Institute of Technology Lausanne (EPFL)LausanneSwitzerland
| | - Rob Jelier
- Centre of Microbial and Plant Genetics, Katholieke Universiteit LeuvenLeuvenBelgium
| | - Pierre Gönczy
- Swiss Institute for Experimental Cancer Research (ISREC), School of Life Sciences, Swiss Federal Institute of Technology Lausanne (EPFL)LausanneSwitzerland
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6
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Wu X, Zhou J, Li D. Orientation of the Mitotic Spindle in Blood Vessel Development. Front Cell Dev Biol 2020; 8:583325. [PMID: 33072763 PMCID: PMC7533553 DOI: 10.3389/fcell.2020.583325] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2020] [Accepted: 09/01/2020] [Indexed: 12/21/2022] Open
Abstract
Angiogenesis requires coordinated endothelial cell specification, proliferation, and collective migration. The orientation of endothelial cell division is tightly regulated during the earliest stages of blood vessel formation in response to morphogenetic cues and the controlled orientation of the mitotic spindle. Consequently, oriented cell division is a vital mechanism in vessel morphogenesis, and defective spindle orientation can perturb the spatial arrangement of daughter cells and consequently contribute to several diseases related to vascular development. Many factors affect endothelial cell proliferation and orientation and therefore blood vessel formation, with the relationship between improper spindle orientation in endothelial cells and various diseases extensively studied. Here we review the molecular mechanisms driving the orientation of endothelial cell division, particularly with respect to the mitotic spindle, and how these processes affect vascular development, disease pathogenesis, and their potential as novel targets.
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Affiliation(s)
- Xuemei Wu
- State Key Laboratory of Medicinal Chemical Biology, College of Life Sciences, Nankai University, Tianjin, China
| | - Jun Zhou
- State Key Laboratory of Medicinal Chemical Biology, College of Life Sciences, Nankai University, Tianjin, China.,Shandong Provincial Key Laboratory of Animal Resistance Biology, Collaborative Innovation Center of Cell Biology in Universities of Shandong, College of Life Sciences, Institute of Biomedical Sciences, Shandong Normal University, Jinan, China
| | - Dengwen Li
- State Key Laboratory of Medicinal Chemical Biology, College of Life Sciences, Nankai University, Tianjin, China
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7
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Pimpale LG, Middelkoop TC, Mietke A, Grill SW. Cell lineage-dependent chiral actomyosin flows drive cellular rearrangements in early Caenorhabditis elegans development. eLife 2020; 9:54930. [PMID: 32644039 PMCID: PMC7394549 DOI: 10.7554/elife.54930] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2020] [Accepted: 07/05/2020] [Indexed: 12/15/2022] Open
Abstract
Proper positioning of cells is essential for many aspects of development. Daughter cell positions can be specified via orienting the cell division axis during cytokinesis. Rotatory actomyosin flows during division have been implied in specifying and reorienting the cell division axis, but how general such reorientation events are, and how they are controlled, remains unclear. We followed the first nine divisions of Caenorhabditis elegans embryo development and demonstrate that chiral counter-rotating flows arise systematically in early AB lineage, but not in early P/EMS lineage cell divisions. Combining our experiments with thin film active chiral fluid theory we identify a mechanism by which chiral counter-rotating actomyosin flows arise in the AB lineage only, and show that they drive lineage-specific spindle skew and cell reorientation events. In conclusion, our work sheds light on the physical processes that underlie chiral morphogenesis in early development.
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Affiliation(s)
- Lokesh G Pimpale
- Max Planck Institute of Molecular Cell Biology and Genetics, Dresden, Germany.,Biotechnology Center, TU Dresden, Dresden, Germany.,Cluster of Excellence Physics of Life, TU Dresden, Dresden, Germany
| | - Teije C Middelkoop
- Max Planck Institute of Molecular Cell Biology and Genetics, Dresden, Germany.,Biotechnology Center, TU Dresden, Dresden, Germany.,Cluster of Excellence Physics of Life, TU Dresden, Dresden, Germany
| | - Alexander Mietke
- Max Planck Institute of Molecular Cell Biology and Genetics, Dresden, Germany.,Max Planck Institute for the Physics of Complex Systems, Dresden, Germany.,Chair of Scientific Computing for Systems Biology, Faculty of Computer Science, TU Dresden, Dresden, Germany.,Center for Systems Biology Dresden, Dresden, Germany.,Department of Mathematics, Massachusetts Institute of Technology, Cambridge, United States
| | - Stephan W Grill
- Max Planck Institute of Molecular Cell Biology and Genetics, Dresden, Germany.,Biotechnology Center, TU Dresden, Dresden, Germany.,Cluster of Excellence Physics of Life, TU Dresden, Dresden, Germany
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8
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Kotak S. Mechanisms of Spindle Positioning: Lessons from Worms and Mammalian Cells. Biomolecules 2019; 9:E80. [PMID: 30823600 PMCID: PMC6406873 DOI: 10.3390/biom9020080] [Citation(s) in RCA: 33] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2019] [Revised: 02/13/2019] [Accepted: 02/18/2019] [Indexed: 02/06/2023] Open
Abstract
Proper positioning of the mitotic spindle is fundamental for specifying the site for cleavage furrow, and thus regulates the appropriate sizes and accurate distribution of the cell fate determinants in the resulting daughter cells during development and in the stem cells. The past couple of years have witnessed tremendous work accomplished in the area of spindle positioning, and this has led to the emergence of a working model unravelling in-depth mechanistic insight of the underlying process orchestrating spindle positioning. It is evident now that the correct positioning of the mitotic spindle is not only guided by the chemical cues (protein⁻protein interactions) but also influenced by the physical nature of the cellular environment. In metazoans, the key players that regulate proper spindle positioning are the actin-rich cell cortex and associated proteins, the ternary complex (Gα/GPR-1/2/LIN-5 in Caenorhabditis elegans, Gαi/Pins/Mud in Drosophila and Gαi1-3/LGN/NuMA in humans), minus-end-directed motor protein dynein and the cortical machinery containing myosin. In this review, I will mainly discuss how the abovementioned components precisely and spatiotemporally regulate spindle positioning by sensing the physicochemical environment for execution of flawless mitosis.
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Affiliation(s)
- Sachin Kotak
- Department of Microbiology and Cell Biology (MCB), Indian Institute of Science (IISc), Bangalore 560012, India.
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9
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Abstract
For over a century, the centrosome has been an organelle more easily tracked than understood, and the study of its peregrinations within the cell remains a chief underpinning of its functional investigation. Increasing attention and new approaches have been brought to bear on mechanisms that control centrosome localization in the context of cleavage plane determination, ciliogenesis, directional migration, and immunological synapse formation, among other cellular and developmental processes. The Golgi complex, often linked with the centrosome, presents a contrasting case of a pleiomorphic organelle for which functional studies advanced somewhat more rapidly than positional tracking. However, Golgi orientation and distribution has emerged as an area of considerable interest with respect to polarized cellular function. This chapter will review our current understanding of the mechanism and significance of the positioning of these organelles.
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10
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Liro MJ, Morton DG, Rose LS. The kinases PIG-1 and PAR-1 act in redundant pathways to regulate asymmetric division in the EMS blastomere of C. elegans. Dev Biol 2018; 444:9-19. [PMID: 30213539 PMCID: PMC6238631 DOI: 10.1016/j.ydbio.2018.08.016] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2017] [Revised: 08/19/2018] [Accepted: 08/31/2018] [Indexed: 10/28/2022]
Abstract
The PAR-1 kinase of C. elegans is localized to the posterior of the one-cell embryo and its mutations affect asymmetric spindle placement and partitioning of cytoplasmic components in the first cell cycle. However, par-1 mutations do not cause failure to restrict the anterior PAR polarity complex to the same extent as mutations in the posteriorly localized PAR-2 protein. Further, it has been difficult to examine the role of PAR-1 in subsequent divisions due to the early defects in par-1 mutant embryos. Here we show that the PIG-1 kinase acts redundantly with PAR-1 to restrict the anterior PAR-3 protein for normal polarity in the one-cell embryo. By using a temperature sensitive allele of par-1, which exhibits enhanced lethality when combined with a pig-1 mutation, we have further explored roles for these genes in subsequent divisions. We find that both PIG-1 and PAR-1 regulate spindle orientation in the EMS blastomere of the four-cell stage embryo to ensure that it undergoes an asymmetric division. In this cell, PIG-1 and PAR-1 act in parallel pathways for spindle positioning, PIG-1 in the MES-1/SRC-1 pathway and PAR-1 in the Wnt pathway.
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Affiliation(s)
- Małgorzata J. Liro
- Department of Molecular and Cellular Biology and Graduate
Program in Biochemistry, Molecular, Cellular and Developmental Biology, University
of California, Davis, CA, 95616
| | - Diane G. Morton
- Department of Molecular Biology and Genetics, Cornell
University, Ithaca NY 14853
| | - Lesilee S. Rose
- Department of Molecular and Cellular Biology and Graduate
Program in Biochemistry, Molecular, Cellular and Developmental Biology, University
of California, Davis, CA, 95616
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11
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G Proteins and GPCRs in C. elegans Development: A Story of Mutual Infidelity. J Dev Biol 2018; 6:jdb6040028. [PMID: 30477278 PMCID: PMC6316442 DOI: 10.3390/jdb6040028] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2018] [Revised: 11/15/2018] [Accepted: 11/22/2018] [Indexed: 12/14/2022] Open
Abstract
Many vital processes during C. elegans development, especially the establishment and maintenance of cell polarity in embryogenesis, are controlled by complex signaling pathways. G protein-coupled receptors (GPCRs), such as the four Frizzled family Wnt receptors, are linchpins in regulating and orchestrating several of these mechanisms. However, despite being GPCRs, which usually couple to G proteins, these receptors do not seem to activate classical heterotrimeric G protein-mediated signaling cascades. The view on signaling during embryogenesis is further complicated by the fact that heterotrimeric G proteins do play essential roles in cell polarity during embryogenesis, but their activity is modulated in a predominantly GPCR-independent manner via G protein regulators such as GEFs GAPs and GDIs. Further, the triggered downstream effectors are not typical. Only very few GPCR-dependent and G protein-mediated signaling pathways have been unambiguously defined in this context. This unusual and highly intriguing concept of separating GPCR function and G-protein activity, which is not restricted to embryogenesis in C. elegans but can also be found in other organisms, allows for essential and multi-faceted ways of regulating cellular communication and response. Although its relevance cannot be debated, its impact is still poorly discussed, and C. elegans is an ideal model to understand the underlying principles.
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12
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Combinatorial Contact Cues Specify Cell Division Orientation by Directing Cortical Myosin Flows. Dev Cell 2018; 46:257-270.e5. [PMID: 30032990 PMCID: PMC7695482 DOI: 10.1016/j.devcel.2018.06.020] [Citation(s) in RCA: 33] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2017] [Revised: 04/13/2018] [Accepted: 06/22/2018] [Indexed: 12/31/2022]
Abstract
Cell division axes during development are specified in different orientations to establish multicellular assemblies, but the mechanisms that generate division axis diversity remain unclear. We show here that patterns of cell contact provide cues that diversify cell division orientation by modulating cortical non-muscle myosin flow. We reconstituted in vivo contact patterns using beads or isolated cells to show two findings. First, we identified three contact-dependent cues that pattern cell division orientation and myosin flow: physical contact, contact asymmetry, and a Wnt signal. Second, we experimentally demonstrated that myosin flow generates forces that trigger plasma membrane movements and propose that their anisotropy drives cell division orientation. Our data suggest that contact-dependent control of myosin specifies the division axes of Caenorhabditis elegans AB, ABa, EMS cells, and the mouse AB cell. The contact pattern-dependent generation of myosin flows, in concert with known microtubule/dynein pathways, may greatly expand division axis diversity during development.
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13
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Heppert JK, Pani AM, Roberts AM, Dickinson DJ, Goldstein B. A CRISPR Tagging-Based Screen Reveals Localized Players in Wnt-Directed Asymmetric Cell Division. Genetics 2018; 208:1147-1164. [PMID: 29348144 PMCID: PMC5844328 DOI: 10.1534/genetics.117.300487] [Citation(s) in RCA: 40] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2017] [Accepted: 01/08/2018] [Indexed: 11/18/2022] Open
Abstract
Oriented cell divisions are critical to establish and maintain cell fates and tissue organization. Diverse extracellular and intracellular cues have been shown to provide spatial information for mitotic spindle positioning; however, the molecular mechanisms by which extracellular signals communicate with cells to direct mitotic spindle positioning are largely unknown. In animal cells, oriented cell divisions are often achieved by the localization of force-generating motor protein complexes to discrete cortical domains. Disrupting either these force-generating complexes or proteins that globally affect microtubule stability results in defects in mitotic positioning, irrespective of whether these proteins function as spatial cues for spindle orientation. This poses a challenge to traditional genetic dissection of this process. Therefore, as an alternative strategy to identify key proteins that act downstream of intercellular signaling, we screened the localization of many candidate proteins by inserting fluorescent tags directly into endogenous gene loci, without overexpressing the proteins. We tagged 23 candidate proteins in Caenorhabditis elegans and examined each protein's localization in a well-characterized, oriented cell division in the four-cell-stage embryo. We used cell manipulations and genetic experiments to determine which cells harbor key localized proteins and which signals direct these localizations in vivo We found that Dishevelled and adenomatous polyposis coli homologs are polarized during this oriented cell division in response to a Wnt signal, but two proteins typically associated with mitotic spindle positioning, homologs of NuMA and Dynein, were not detectably polarized. These results suggest an unexpected mechanism for mitotic spindle positioning in this system, they pinpoint key proteins of interest, and they highlight the utility of a screening approach based on analyzing the localization of endogenously tagged proteins.
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Affiliation(s)
- Jennifer K Heppert
- Department of Biology, University of North Carolina at Chapel Hill, North Carolina 27599
| | - Ariel M Pani
- Department of Biology, University of North Carolina at Chapel Hill, North Carolina 27599
- Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, North Carolina 27599
| | - Allyson M Roberts
- Curriculum in Genetics and Molecular Biology, University of North Carolina at Chapel Hill, North Carolina 27599
| | - Daniel J Dickinson
- Department of Biology, University of North Carolina at Chapel Hill, North Carolina 27599
- Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, North Carolina 27599
| | - Bob Goldstein
- Department of Biology, University of North Carolina at Chapel Hill, North Carolina 27599
- Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, North Carolina 27599
- Curriculum in Genetics and Molecular Biology, University of North Carolina at Chapel Hill, North Carolina 27599
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14
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Price KL, Rose LS. LET-99 functions in the astral furrowing pathway, where it is required for myosin enrichment in the contractile ring. Mol Biol Cell 2017; 28:2360-2373. [PMID: 28701343 PMCID: PMC5576900 DOI: 10.1091/mbc.e16-12-0874] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2016] [Revised: 06/16/2017] [Accepted: 06/27/2017] [Indexed: 11/11/2022] Open
Abstract
LET-99 is required for furrowing during cytokinesis in both symmetrically and asymmetrically dividing cells. This function is distinct from the role of LET-99 in spindle positioning with Gα signaling. LET-99 is localized to the furrow, where it acts to promote myosin enrichment. The anaphase spindle determines the position of the cytokinesis furrow, such that the contractile ring assembles in an equatorial zone between the two spindle poles. Contractile ring formation is mediated by RhoA activation at the equator by the centralspindlin complex and midzone microtubules. Astral microtubules also inhibit RhoA accumulation at the poles. In the Caenorhabditis elegans one-cell embryo, the astral microtubule–dependent pathway requires anillin, NOP-1, and LET-99. LET-99 is well characterized for generating the asymmetric cortical localization of the Gα-dependent force-generating complex that positions the spindle during asymmetric division. However, whether the role of LET-99 in cytokinesis is specific to asymmetric division and whether it acts through Gα to promote furrowing are unclear. Here we show that LET-99 contributes to furrowing in both asymmetrically and symmetrically dividing cells, independent of its function in spindle positioning and Gα regulation. LET-99 acts in a pathway parallel to anillin and is required for myosin enrichment into the contractile ring. These and other results suggest a positive feedback model in which LET-99 localizes to the presumptive cleavage furrow in response to the spindle and myosin. Once positioned there, LET-99 enhances myosin accumulation to promote furrowing in both symmetrically and asymmetrically dividing cells.
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Affiliation(s)
- Kari L Price
- Department of Molecular and Cellular Biology and Biochemistry, Molecular, Cellular and Developmental Biology Graduate Program, University of California, Davis, Davis, CA 95616
| | - Lesilee S Rose
- Department of Molecular and Cellular Biology and Biochemistry, Molecular, Cellular and Developmental Biology Graduate Program, University of California, Davis, Davis, CA 95616
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