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Balasubramaniam B, Topalidou I, Kelley M, Meadows SM, Funk O, Ailion M, Fay DS. Effectors of anterior morphogenesis in C. elegans embryos. Biol Open 2023; 12:bio059982. [PMID: 37345480 PMCID: PMC10339035 DOI: 10.1242/bio.059982] [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: 04/23/2023] [Accepted: 06/19/2023] [Indexed: 06/23/2023] Open
Abstract
During embryogenesis the nascent Caenorhabditis elegans epidermis secretes an apical extracellular matrix (aECM) that serves as an external stabilizer, preventing deformation of the epidermis by mechanical forces exerted during morphogenesis. At present, the factors that contribute to aECM function are mostly unknown, including the aECM components themselves, their posttranslational regulators, and the pathways required for their secretion. Here we showed that two proteins previously linked to aECM function, SYM-3/FAM102A and SYM-4/WDR44, colocalize to intracellular and membrane-associated puncta and likely function in a complex. Proteomics experiments also suggested potential roles for SYM-3/FAM102A and SYM-4/WDR44 family proteins in intracellular trafficking. Nonetheless, we found no evidence to support a critical function for SYM-3 or SYM-4 in the apical deposition of two aECM components, NOAH-1 and FBN-1. Moreover, loss of a key splicing regulator of fbn-1, MEC-8/RBPMS2, had surprisingly little effect on the abundance or deposition of FBN-1. Using a focused screening approach, we identified 32 additional proteins that likely contribute to the structure and function of the embryonic aECM. We also characterized morphogenesis defects in embryos lacking mir-51 microRNA family members, which display a similar phenotype to mec-8; sym double mutants. Collectively, these findings add to our knowledge of factors controlling embryonic morphogenesis.
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Affiliation(s)
- Boopathi Balasubramaniam
- Department of Molecular Biology, College of Agriculture, Life Sciences and Natural Resources, University of Wyoming, Laramie 82071-3944, WY, USA
| | - Irini Topalidou
- Department of Biochemistry, University of Washington, Seattle 98195-7350, WA, USA
| | - Melissa Kelley
- Department of Molecular Biology, College of Agriculture, Life Sciences and Natural Resources, University of Wyoming, Laramie 82071-3944, WY, USA
| | - Sarina M. Meadows
- Department of Molecular Biology, College of Agriculture, Life Sciences and Natural Resources, University of Wyoming, Laramie 82071-3944, WY, USA
| | - Owen Funk
- Department of Molecular Biology, College of Agriculture, Life Sciences and Natural Resources, University of Wyoming, Laramie 82071-3944, WY, USA
| | - Michael Ailion
- Department of Biochemistry, University of Washington, Seattle 98195-7350, WA, USA
| | - David S. Fay
- Department of Molecular Biology, College of Agriculture, Life Sciences and Natural Resources, University of Wyoming, Laramie 82071-3944, WY, USA
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Boopathi B, Topalidou I, Kelley M, Meadows SM, Funk O, Ailion M, Fay DS. Pathways that affect anterior morphogenesis in C. elegans embryos. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.04.23.537986. [PMID: 37163004 PMCID: PMC10168279 DOI: 10.1101/2023.04.23.537986] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
During embryogenesis the nascent Caenorhabditis elegans epidermis secretes an apical extracellular matrix (aECM) that serves as an external stabilizer, preventing deformation of the epidermis by mechanical forces exerted during morphogenesis. We showed that two conserved proteins linked to this process, SYM-3/FAM102A and SYM-4/WDR44, colocalize to intracellular and membrane-associated puncta and likely function together in a complex. Proteomics data also suggested potential roles for FAM102A and WDR44 family proteins in intracellular trafficking, consistent with their localization patterns. Nonetheless, we found no evidence to support a clear function for SYM-3 or SYM-4 in the apical deposition of two aECM components, FBN-1 and NOAH. Surprisingly, loss of MEC-8/RBPMS2, a conserved splicing factor and regulator of fbn-1 , had little effect on the abundance or deposition of FBN-1 to the aECM. Using a focused screening approach, we identified 32 additional proteins that likely contribute to the structure and function of the embryonic aECM. Lastly, we examined morphogenesis defects in embryos lacking mir-51 microRNA family members, which display a related embryonic phenotype to mec-8; sym double mutants. Collectively, our findings add to our knowledge of pathways controlling embryonic morphogenesis. SUMMARY STATEMENT We identify new proteins in apical ECM biology in C. elegans and provide evidence that SYM-3/FAM102A and SYM-4/WDR44 function together in trafficking but do not regulate apical ECM protein deposition.
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Affiliation(s)
- Balasubramaniam Boopathi
- Department of Molecular Biology, College of Agriculture, Life Sciences and Natural Resources, University of Wyoming, Laramie, Wyoming, United States of America
| | - Irini Topalidou
- Department of Biochemistry, University of Washington, Seattle, United States of America
| | - Melissa Kelley
- Department of Molecular Biology, College of Agriculture, Life Sciences and Natural Resources, University of Wyoming, Laramie, Wyoming, United States of America
| | - Sarina M Meadows
- Department of Molecular Biology, College of Agriculture, Life Sciences and Natural Resources, University of Wyoming, Laramie, Wyoming, United States of America
| | - Owen Funk
- Department of Molecular Biology, College of Agriculture, Life Sciences and Natural Resources, University of Wyoming, Laramie, Wyoming, United States of America
| | - Michael Ailion
- Department of Biochemistry, University of Washington, Seattle, United States of America
| | - David S Fay
- Department of Molecular Biology, College of Agriculture, Life Sciences and Natural Resources, University of Wyoming, Laramie, Wyoming, United States of America
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3
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Naturale VF, Pickett MA, Feldman JL. Context matters: Lessons in epithelial polarity from the Caenorhabditis elegans intestine and other tissues. Curr Top Dev Biol 2023; 154:37-71. [PMID: 37100523 DOI: 10.1016/bs.ctdb.2023.02.007] [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: 04/28/2023]
Abstract
Epithelia are tissues with diverse morphologies and functions across metazoans, ranging from vast cell sheets encasing internal organs to internal tubes facilitating nutrient uptake, all of which require establishment of apical-basolateral polarity axes. While all epithelia tend to polarize the same components, how these components are deployed to drive polarization is largely context-dependent and likely shaped by tissue-specific differences in development and ultimate functions of polarizing primordia. The nematode Caenorhabditis elegans (C. elegans) offers exceptional imaging and genetic tools and possesses unique epithelia with well-described origins and roles, making it an excellent model to investigate polarity mechanisms. In this review, we highlight the interplay between epithelial polarization, development, and function by describing symmetry breaking and polarity establishment in a particularly well-characterized epithelium, the C. elegans intestine. We compare intestinal polarization to polarity programs in two other C. elegans epithelia, the pharynx and epidermis, correlating divergent mechanisms with tissue-specific differences in geometry, embryonic environment, and function. Together, we emphasize the importance of investigating polarization mechanisms against the backdrop of tissue-specific contexts, while also underscoring the benefits of cross-tissue comparisons of polarity.
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Affiliation(s)
- Victor F Naturale
- Department of Biology, Stanford University, Stanford, CA, United States
| | - Melissa A Pickett
- Department of Biology, Stanford University, Stanford, CA, United States; Department of Biological Sciences, San José State University, San José, CA, United States
| | - Jessica L Feldman
- Department of Biology, Stanford University, Stanford, CA, United States.
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Vidal B, Gulez B, Cao WX, Leyva-Diaz E, Reilly MB, Tekieli T, Hobert O. The enteric nervous system of the C. elegans pharynx is specified by the Sine oculis-like homeobox gene ceh-34. eLife 2022; 11:76003. [PMID: 35324425 PMCID: PMC8989417 DOI: 10.7554/elife.76003] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2021] [Accepted: 03/23/2022] [Indexed: 11/29/2022] Open
Abstract
Overarching themes in the terminal differentiation of the enteric nervous system, an autonomously acting unit of animal nervous systems, have so far eluded discovery. We describe here the overall regulatory logic of enteric nervous system differentiation of the nematode Caenorhabditis elegans that resides within the foregut (pharynx) of the worm. A C. elegans homolog of the Drosophila Sine oculis homeobox gene, ceh-34, is expressed in all 14 classes of interconnected pharyngeal neurons from their birth throughout their life time, but in no other neuron type of the entire animal. Constitutive and temporally controlled ceh-34 removal shows that ceh-34 is required to initiate and maintain the neuron type-specific terminal differentiation program of all pharyngeal neuron classes, including their circuit assembly. Through additional genetic loss of function analysis, we show that within each pharyngeal neuron class, ceh-34 cooperates with different homeodomain transcription factors to individuate distinct pharyngeal neuron classes. Our analysis underscores the critical role of homeobox genes in neuronal identity specification and links them to the control of neuronal circuit assembly of the enteric nervous system. Together with the pharyngeal nervous system simplicity as well as its specification by a Sine oculis homolog, our findings invite speculations about the early evolution of nervous systems.
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Affiliation(s)
- Berta Vidal
- Department of Biological Sciences, Columbia University, Howard Hughes Medical Institute, New York, United States
| | - Burcu Gulez
- Department of Biological Sciences, Columbia University, Howard Hughes Medical Institute, New York, United States
| | - Wen Xi Cao
- Department of Biological Sciences, Columbia University, Howard Hughes Medical Institute, New York, United States
| | - Eduardo Leyva-Diaz
- Department of Biological Sciences, Columbia University, Howard Hughes Medical Institute, New York, United States
| | - Molly B Reilly
- Department of Biological Sciences, Columbia University, Howard Hughes Medical Institute, New York, United States
| | - Tessa Tekieli
- Department of Biological Sciences, Columbia University, Howard Hughes Medical Institute, New York, United States
| | - Oliver Hobert
- Department of Biological Sciences, Columbia University, Howard Hughes Medical Institute, New York, United States
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Abstract
Biological development is often described as a dynamic, emergent process. This is evident across a variety of phenomena, from the temporal organization of cell types in the embryo to compounding trends that affect large-scale differentiation. To better understand this, we propose combining quantitative investigations of biological development with theory-building techniques. This provides an alternative to the gene-centric view of development: namely, the view that developmental genes and their expression determine the complexity of the developmental phenotype. Using the model system Caenorhabditis elegans, we examine time-dependent properties of the embryonic phenotype and utilize the unique life-history properties to demonstrate how these emergent properties can be linked together by data analysis and theory-building. We also focus on embryogenetic differentiation processes, and how terminally-differentiated cells contribute to structure and function of the adult phenotype. Examining embryogenetic dynamics from 200 to 400 min post-fertilization provides basic quantitative information on developmental tempo and process. To summarize, theory construction techniques are summarized and proposed as a way to rigorously interpret our data. Our proposed approach to a formal data representation that can provide critical links across life-history, anatomy and function.
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Casasa S, Biddle JF, Koutsovoulos GD, Ragsdale EJ. Polyphenism of a Novel Trait Integrated Rapidly Evolving Genes into Ancestrally Plastic Networks. Mol Biol Evol 2021; 38:331-343. [PMID: 32931588 PMCID: PMC7826178 DOI: 10.1093/molbev/msaa235] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Developmental polyphenism, the ability to switch between phenotypes in response to environmental variation, involves the alternating activation of environmentally sensitive genes. Consequently, to understand how a polyphenic response evolves requires a comparative analysis of the components that make up environmentally sensitive networks. Here, we inferred coexpression networks for a morphological polyphenism, the feeding-structure dimorphism of the nematode Pristionchus pacificus. In this species, individuals produce alternative forms of a novel trait—moveable teeth, which in one morph enable predatory feeding—in response to environmental cues. To identify the origins of polyphenism network components, we independently inferred coexpression modules for more conserved transcriptional responses, including in an ancestrally nonpolyphenic nematode species. Further, through genome-wide analyses of these components across the nematode family (Diplogastridae) in which the polyphenism arose, we reconstructed how network components have changed. To achieve this, we assembled and resolved the phylogenetic context for five genomes of species representing the breadth of Diplogastridae and a hypothesized outgroup. We found that gene networks instructing alternative forms arose from ancestral plastic responses to environment, specifically starvation-induced metabolism and the formation of a conserved diapause (dauer) stage. Moreover, loci from rapidly evolving gene families were integrated into these networks with higher connectivity than throughout the rest of the P. pacificus transcriptome. In summary, we show that the modular regulatory outputs of a polyphenic response evolved through the integration of conserved plastic responses into networks with genes of high evolutionary turnover.
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Affiliation(s)
- Sofia Casasa
- Department of Biology, Indiana University, Bloomington, Bloomington, IN
| | - Joseph F Biddle
- Department of Biology, Indiana University, Bloomington, Bloomington, IN
| | | | - Erik J Ragsdale
- Department of Biology, Indiana University, Bloomington, Bloomington, IN
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Grimbert S, Mastronardi K, Richard V, Christensen R, Law C, Zardoui K, Fay D, Piekny A. Multi-tissue patterning drives anterior morphogenesis of the C. elegans embryo. Dev Biol 2021; 471:49-64. [PMID: 33309948 PMCID: PMC8597047 DOI: 10.1016/j.ydbio.2020.12.003] [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: 04/29/2020] [Revised: 12/01/2020] [Accepted: 12/02/2020] [Indexed: 11/23/2022]
Abstract
Complex structures derived from multiple tissue types are challenging to study in vivo, and our knowledge of how cells from different tissues are coordinated is limited. Model organisms have proven invaluable for improving our understanding of how chemical and mechanical cues between cells from two different tissues can govern specific morphogenetic events. Here we used Caenorhabditis elegans as a model system to show how cells from three different tissues are coordinated to give rise to the anterior lumen. While some aspects of pharyngeal morphogenesis have been well-described, it is less clear how cells from the pharynx, epidermis and neuroblasts coordinate to define the location of the anterior lumen and supporting structures. Using various microscopy and software approaches, we define the movements and patterns of these cells during anterior morphogenesis. Projections from the anterior-most pharyngeal cells (arcade cells) provide the first visible markers for the location of the future lumen, and facilitate patterning of the surrounding neuroblasts. These neuroblast patterns control the rate of migration of the anterior epidermal cells, whereas the epidermal cells ultimately reinforce and control the position of the future lumen, as they must join with the pharyngeal cells for their epithelialization. Our studies are the first to characterize anterior morphogenesis in C. elegans in detail and should lay the framework for identifying how these different patterns are controlled at the molecular level.
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Affiliation(s)
- Stéphanie Grimbert
- Department of Biology, Concordia University, 7141 Sherbrooke Street West, Montreal, Quebec, H4B 1R6, Canada
| | - Karina Mastronardi
- Department of Biology, Concordia University, 7141 Sherbrooke Street West, Montreal, Quebec, H4B 1R6, Canada
| | - Victoria Richard
- Department of Biology, Concordia University, 7141 Sherbrooke Street West, Montreal, Quebec, H4B 1R6, Canada
| | - Ryan Christensen
- Laboratory of High Resolution Optical Imaging, NIH/NIBIB, 13 South Drive, Bethesda, MD, 20892, USA
| | - Christopher Law
- Department of Biology, Concordia University, 7141 Sherbrooke Street West, Montreal, Quebec, H4B 1R6, Canada
| | - Khashayar Zardoui
- Department of Biology, Concordia University, 7141 Sherbrooke Street West, Montreal, Quebec, H4B 1R6, Canada
| | - David Fay
- Department of Molecular Biology, University of Wyoming, 1000 E. University Ave., Laramie, WY, 82071, USA
| | - Alisa Piekny
- Department of Biology, Concordia University, 7141 Sherbrooke Street West, Montreal, Quebec, H4B 1R6, Canada.
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8
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Abstract
As multi-cellular organisms evolved from small clusters of cells to complex metazoans, biological tubes became essential for life. Tubes are typically thought of as mainly playing a role in transport, with the hollow space (lumen) acting as a conduit to distribute nutrients and waste, or for gas exchange. However, biological tubes also provide a platform for physiological, mechanical, and structural functions. Indeed, tubulogenesis is often a critical aspect of morphogenesis and organogenesis. C. elegans is made up of tubes that provide structural support and protection (the epidermis), perform the mechanical and enzymatic processes of digestion (the buccal cavity, pharynx, intestine, and rectum), transport fluids for osmoregulation (the excretory system), and execute the functions necessary for reproduction (the germline, spermatheca, uterus and vulva). Here we review our current understanding of the genetic regulation, molecular processes, and physical forces involved in tubulogenesis and morphogenesis of the epidermal, digestive and excretory systems in C. elegans.
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Affiliation(s)
- Daniel D Shaye
- Department of Physiology and Biophysics, University of Illinois at Chicago-College of Medicine, Chicago, IL, United States.
| | - Martha C Soto
- Department of Pathology and Laboratory Medicine, Rutgers-Robert Wood Johnson Medical School, Piscataway, NJ, United States.
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9
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Alicea B. Raising the Connectome: The Emergence of Neuronal Activity and Behavior in Caenorhabditis elegans. Front Cell Neurosci 2020; 14:524791. [PMID: 33100971 PMCID: PMC7522492 DOI: 10.3389/fncel.2020.524791] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2020] [Accepted: 08/24/2020] [Indexed: 11/15/2022] Open
Abstract
The differentiation of neurons and formation of connections between cells is the basis of both the adult phenotype and behaviors tied to cognition, perception, reproduction, and survival. Such behaviors are associated with local (circuits) and global (connectome) brain networks. A solid understanding of how these networks emerge is critical. This opinion piece features a guided tour of early developmental events in the emerging connectome, which is crucial to a new view on the connectogenetic process. Connectogenesis includes associating cell identities with broader functional and developmental relationships. During this process, the transition from developmental cells to terminally differentiated cells is defined by an accumulation of traits that ultimately results in neuronal-driven behavior. The well-characterized developmental and cell biology of Caenorhabditis elegans will be used to build a synthesis of developmental events that result in a functioning connectome. Specifically, our view of connectogenesis enables a first-mover model of synaptic connectivity to be demonstrated using data representing larval synaptogenesis. In a first-mover model of Stackelberg competition, potential pre- and postsynaptic relationships are shown to yield various strategies for establishing various types of synaptic connections. By comparing these results to what is known regarding principles for establishing complex network connectivity, these strategies are generalizable to other species and developmental systems. In conclusion, we will discuss the broader implications of this approach, as what is presented here informs an understanding of behavioral emergence and the ability to simulate related biological phenomena.
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Affiliation(s)
- Bradly Alicea
- Orthogonal Research and Education Laboratory, Champaign, IL, United States
- OpenWorm Foundation, Boston, MA, United States
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10
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Bai X, Melesse M, Sorensen Turpin CG, Sloan DE, Chen CY, Wang WC, Lee PY, Simmons JR, Nebenfuehr B, Mitchell D, Klebanow LR, Mattson N, Betzig E, Chen BC, Cheerambathur D, Bembenek JN. Aurora B functions at the apical surface after specialized cytokinesis during morphogenesis in C. elegans. Development 2020; 147:dev.181099. [PMID: 31806662 PMCID: PMC6983721 DOI: 10.1242/dev.181099] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2019] [Accepted: 11/26/2019] [Indexed: 12/18/2022]
Abstract
Although cytokinesis has been intensely studied, the way it is executed during development is not well understood, despite a long-standing appreciation that various aspects of cytokinesis vary across cell and tissue types. To address this, we investigated cytokinesis during the invariant Caenorhabditis elegans embryonic divisions and found several parameters that are altered at different stages in a reproducible manner. During early divisions, furrow ingression asymmetry and midbody inheritance is consistent, suggesting specific regulation of these events. During morphogenesis, we found several unexpected alterations to cytokinesis, including apical midbody migration in polarizing epithelial cells of the gut, pharynx and sensory neurons. Aurora B kinase, which is essential for several aspects of cytokinesis, remains apically localized in each of these tissues after internalization of midbody ring components. Aurora B inactivation disrupts cytokinesis and causes defects in apical structures, even if inactivated post-mitotically. Therefore, we demonstrate that cytokinesis is implemented in a specialized way during epithelial polarization and that Aurora B has a role in the formation of the apical surface.
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Affiliation(s)
- Xiaofei Bai
- Department of Biochemistry, Cellular and Molecular Biology, University of Tennessee, Knoxville, TN 37996, USA
| | - Michael Melesse
- Department of Biochemistry, Cellular and Molecular Biology, University of Tennessee, Knoxville, TN 37996, USA
| | | | - Dillon E. Sloan
- Department of Biochemistry, Cellular and Molecular Biology, University of Tennessee, Knoxville, TN 37996, USA,Department of Molecular, Cellular and Developmental Biology, University of Michigan, Ann Arbor, MI 48109, USA
| | - Chin-Yi Chen
- Research Center for Applied Sciences, Academia Sinica, Taipei, Taiwan
| | - Wen-Cheng Wang
- Research Center for Applied Sciences, Academia Sinica, Taipei, Taiwan
| | - Po-Yi Lee
- Research Center for Applied Sciences, Academia Sinica, Taipei, Taiwan
| | - James R. Simmons
- Department of Biochemistry, Cellular and Molecular Biology, University of Tennessee, Knoxville, TN 37996, USA
| | - Benjamin Nebenfuehr
- Department of Biochemistry, Cellular and Molecular Biology, University of Tennessee, Knoxville, TN 37996, USA
| | - Diana Mitchell
- Department of Molecular, Cellular and Developmental Biology, University of Michigan, Ann Arbor, MI 48109, USA
| | - Lindsey R. Klebanow
- Department of Biochemistry, Cellular and Molecular Biology, University of Tennessee, Knoxville, TN 37996, USA
| | - Nicholas Mattson
- Department of Biochemistry, Cellular and Molecular Biology, University of Tennessee, Knoxville, TN 37996, USA
| | - Eric Betzig
- Janelia Research Campus, HHMI, Ashburn, VA 20147, USA
| | - Bi-Chang Chen
- Research Center for Applied Sciences, Academia Sinica, Taipei, Taiwan,Janelia Research Campus, HHMI, Ashburn, VA 20147, USA
| | - Dhanya Cheerambathur
- Wellcome Centre for Cell Biology, University of Edinburgh, Edinburgh, EH9 3BF, UK
| | - Joshua N. Bembenek
- Department of Biochemistry, Cellular and Molecular Biology, University of Tennessee, Knoxville, TN 37996, USA,Department of Molecular, Cellular and Developmental Biology, University of Michigan, Ann Arbor, MI 48109, USA,Author for correspondence ()
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11
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Reduction of mRNA export unmasks different tissue sensitivities to low mRNA levels during Caenorhabditis elegans development. PLoS Genet 2019; 15:e1008338. [PMID: 31525188 PMCID: PMC6762213 DOI: 10.1371/journal.pgen.1008338] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2019] [Revised: 09/26/2019] [Accepted: 07/31/2019] [Indexed: 12/25/2022] Open
Abstract
Animal development requires the execution of specific transcriptional programs in different sets of cells to build tissues and functional organs. Transcripts are exported from the nucleus to the cytoplasm where they are translated into proteins that, ultimately, carry out the cellular functions. Here we show that in Caenorhabditis elegans, reduction of mRNA export strongly affects epithelial morphogenesis and germline proliferation while other tissues remain relatively unaffected. Epithelialization and gamete formation demand a large number of transcripts in the cytoplasm for the duration of these processes. In addition, our findings highlight the existence of a regulatory feedback mechanism that activates gene expression in response to low levels of cytoplasmic mRNA. We expand the genetic characterization of nuclear export factor NXF-1 to other members of the mRNA export pathway to model mRNA export and recycling of NXF-1 back to the nucleus. Our model explains how mutations in genes involved in general processes, such as mRNA export, may result in tissue-specific developmental phenotypes. The Central Dogma of Biology schematically highlights the transmission of genetic information stored in DNA, through RNA, to the formation of proteins. This general flow implicates RNA export from the nucleus to the cytoplasm and proper protein localization within the eukaryotic cell. Ultimately, proteins are the cell’s structural and catalytic functional units. As a result, cells differentiate into one cell type or another (such as epithelial, muscle, neuron…) and exhibit specific shape and functionality. Here we describe, in a C. elegans model, how mutations in genes involved in a general and ubiquitous mechanism, such as mRNA export, may result in tissue-specific developmental phenotypes that show up in processes that are highly demanding of cytoplasmic transcripts like epithelialization and gamete formation. A deep understanding of the mechanisms underlying the "connectors" shown in the Central Dogma of Biology is key both to unravel the general genetic control of an organism’s development and, at the same time, contribute to a better understanding of tissue-specific diseases.
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12
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Alicea B. The emergent connectome in Caenorhabditis elegans embryogenesis. Biosystems 2018; 173:247-255. [DOI: 10.1016/j.biosystems.2018.09.016] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2018] [Revised: 09/20/2018] [Accepted: 09/25/2018] [Indexed: 11/26/2022]
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13
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Sequential formation and resolution of multiple rosettes drive embryo remodelling after implantation. Nat Cell Biol 2018; 20:1278-1289. [PMID: 30323188 DOI: 10.1038/s41556-018-0211-3] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2018] [Accepted: 09/06/2018] [Indexed: 11/08/2022]
Abstract
The morphogenetic remodelling of embryo architecture after implantation culminates in pro-amniotic cavity formation. Despite its key importance, how this transformation occurs remains unknown. Here, we apply high-resolution imaging of embryos developing in vivo and in vitro, spatial RNA sequencing and 3D trophoblast stem cell models to determine the sequence and mechanisms of these remodelling events. We show that cavitation of the embryonic tissue is followed by folding of extra-embryonic tissue to mediate the formation of a second extra-embryonic cavity. Concomitantly, at the boundary between embryonic and extra-embryonic tissues, a hybrid 3D rosette forms. Resolution of this rosette enables the embryonic cavity to invade the extra-embryonic tissue. Subsequently, β1-integrin signalling mediates the formation of multiple extra-embryonic 3D rosettes. Podocalyxin exocytosis leads to their polarized resolution, permitting the extension of embryonic and extra-embryonic cavities and their fusion into a unified pro-amniotic cavity. These morphogenetic transformations of embryogenesis reveal a previously unappreciated mechanism for lumen expansion and fusion.
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14
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Blazie SM, Geissel HC, Wilky H, Joshi R, Newbern J, Mangone M. Alternative Polyadenylation Directs Tissue-Specific miRNA Targeting in Caenorhabditis elegans Somatic Tissues. Genetics 2017; 206:757-774. [PMID: 28348061 PMCID: PMC5499184 DOI: 10.1534/genetics.116.196774] [Citation(s) in RCA: 52] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2016] [Accepted: 03/02/2017] [Indexed: 01/03/2023] Open
Abstract
mRNA expression dynamics promote and maintain the identity of somatic tissues in living organisms; however, their impact in post-transcriptional gene regulation in these processes is not fully understood. Here, we applied the PAT-Seq approach to systematically isolate, sequence, and map tissue-specific mRNA from five highly studied Caenorhabditis elegans somatic tissues: GABAergic and NMDA neurons, arcade and intestinal valve cells, seam cells, and hypodermal tissues, and studied their mRNA expression dynamics. The integration of these datasets with previously profiled transcriptomes of intestine, pharynx, and body muscle tissues, precisely assigns tissue-specific expression dynamics for 60% of all annotated C. elegans protein-coding genes, providing an important resource for the scientific community. The mapping of 15,956 unique high-quality tissue-specific polyA sites in all eight somatic tissues reveals extensive tissue-specific 3'untranslated region (3'UTR) isoform switching through alternative polyadenylation (APA) . Almost all ubiquitously transcribed genes use APA and harbor miRNA targets in their 3'UTRs, which are commonly lost in a tissue-specific manner, suggesting widespread usage of post-transcriptional gene regulation modulated through APA to fine tune tissue-specific protein expression. Within this pool, the human disease gene C. elegans orthologs rack-1 and tct-1 use APA to switch to shorter 3'UTR isoforms in order to evade miRNA regulation in the body muscle tissue, resulting in increased protein expression needed for proper body muscle function. Our results highlight a major positive regulatory role for APA, allowing genes to counteract miRNA regulation on a tissue-specific basis.
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Affiliation(s)
- Stephen M Blazie
- Molecular and Cellular Biology Graduate Program, Arizona State University, Tempe, Arizona 85281
- Virginia G. Piper Center for Personalized Diagnostics, The Biodesign Institute at Arizona State University, Tempe, Arizona 85281
| | - Heather C Geissel
- Molecular and Cellular Biology Graduate Program, Arizona State University, Tempe, Arizona 85281
- Virginia G. Piper Center for Personalized Diagnostics, The Biodesign Institute at Arizona State University, Tempe, Arizona 85281
| | - Henry Wilky
- Barrett Honors College, Arizona State University, Tempe, Arizona 85281
| | - Rajan Joshi
- College of Letters and Sciences, Interdisciplinary Studies, Biological Sciences and Informatics, Arizona State University, Tempe, Arizona 85281
| | - Jason Newbern
- Molecular and Cellular Biology Graduate Program, Arizona State University, Tempe, Arizona 85281
- Barrett Honors College, Arizona State University, Tempe, Arizona 85281
| | - Marco Mangone
- Molecular and Cellular Biology Graduate Program, Arizona State University, Tempe, Arizona 85281
- Virginia G. Piper Center for Personalized Diagnostics, The Biodesign Institute at Arizona State University, Tempe, Arizona 85281
- Barrett Honors College, Arizona State University, Tempe, Arizona 85281
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15
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Von Stetina SE, Liang J, Marnellos G, Mango SE. Temporal regulation of epithelium formation mediated by FoxA, MKLP1, MgcRacGAP, and PAR-6. Mol Biol Cell 2017; 28:2042-2065. [PMID: 28539408 PMCID: PMC5509419 DOI: 10.1091/mbc.e16-09-0644] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2016] [Revised: 05/18/2017] [Accepted: 05/18/2017] [Indexed: 12/15/2022] Open
Abstract
During embryo morphogenesis, minor epithelia are generated after, and then form bridges between, major epithelia (e.g., epidermis and gut). In Caenorhabditis elegans, this delay is regulated by four proteins that control production and localization of polarity proteins: the pioneer factor PHA-4/FoxA, kinesin ZEN-4/MKLP1, its partner CYK-4/MgcRacGAP, and PAR-6. To establish the animal body plan, embryos link the external epidermis to the internal digestive tract. In Caenorhabditis elegans, this linkage is achieved by the arcade cells, which form an epithelial bridge between the foregut and epidermis, but little is known about how development of these three epithelia is coordinated temporally. The arcade cell epithelium is generated after the epidermis and digestive tract epithelia have matured, ensuring that both organs can withstand the mechanical stress of embryo elongation; mistiming of epithelium formation leads to defects in morphogenesis. Using a combination of genetic, bioinformatic, and imaging approaches, we find that temporal regulation of the arcade cell epithelium is mediated by the pioneer transcription factor and master regulator PHA-4/FoxA, followed by the cytoskeletal regulator and kinesin ZEN-4/MKLP1 and the polarity protein PAR-6. We show that PHA-4 directly activates mRNA expression of a broad cohort of epithelial genes, including junctional factor dlg-1. Accumulation of DLG-1 protein is delayed by ZEN-4, acting in concert with its binding partner CYK-4/MgcRacGAP. Our structure–function analysis suggests that nuclear and kinesin functions are dispensable, whereas binding to CYK-4 is essential, for ZEN-4 function in polarity. Finally, PAR-6 is necessary to localize polarity proteins such as DLG-1 within adherens junctions and at the apical surface, thereby generating arcade cell polarity. Our results reveal that the timing of a landmark event during embryonic morphogenesis is mediated by the concerted action of four proteins that delay the formation of an epithelial bridge until the appropriate time. In addition, we find that mammalian FoxA associates with many epithelial genes, suggesting that direct regulation of epithelial identity may be a conserved feature of FoxA factors and a contributor to FoxA function in development and cancer.
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Affiliation(s)
- Stephen E Von Stetina
- Department of Molecular and Cellular Biology, Harvard University, Cambridge; MA 02138
| | - Jennifer Liang
- Department of Molecular and Cellular Biology, Harvard University, Cambridge; MA 02138
| | - Georgios Marnellos
- Informatics and Scientific Applications, Science Division, Faculty of Arts and Sciences, Harvard University, Cambridge; MA 02138
| | - Susan E Mango
- Department of Molecular and Cellular Biology, Harvard University, Cambridge; MA 02138
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16
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Jay Burr AH, Baldwin JG. The nematode stoma: Homology of cell architecture with improved understanding by confocal microscopy of labeled cell boundaries. J Morphol 2016; 277:1168-86. [DOI: 10.1002/jmor.20567] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2016] [Revised: 05/24/2016] [Accepted: 05/26/2016] [Indexed: 11/08/2022]
Affiliation(s)
- A. H. Jay Burr
- Department of Biological Sciences; Simon Fraser University; Burnaby British Columbia V5A 1S6 Canada
- Department of Nematology; University of California; Riverside California 92521
| | - James G. Baldwin
- Department of Nematology; University of California; Riverside California 92521
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17
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Martín-Durán JM, Hejnol A. The study of Priapulus caudatus reveals conserved molecular patterning underlying different gut morphogenesis in the Ecdysozoa. BMC Biol 2015; 13:29. [PMID: 25895830 PMCID: PMC4434581 DOI: 10.1186/s12915-015-0139-z] [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: 04/13/2015] [Indexed: 12/14/2022] Open
Abstract
Background The digestive systems of animals can become highly specialized in response to their exploration and occupation of new ecological niches. Although studies on different animals have revealed commonalities in gut formation, the model systems Caenorhabditis elegans and Drosophila melanogaster, which belong to the invertebrate group Ecdysozoa, exhibit remarkable deviations in how their intestines develop. Their morphological and developmental idiosyncrasies have hindered reconstructions of ancestral gut characters for the Ecdysozoa, and limit comparisons with vertebrate models. In this respect, the phylogenetic position, and slow evolving morphological and molecular characters of marine priapulid worms advance them as a key group to decipher evolutionary events that occurred in the lineages leading to C. elegans and D. melanogaster. Results In the priapulid Priapulus caudatus, the gut consists of an ectodermal foregut and anus, and a mid region of at least partial endodermal origin. The inner gut develops into a 16-cell primordium devoid of visceral musculature, arranged in three mid tetrads and two posterior duplets. The mouth invaginates ventrally and shifts to a terminal anterior position as the ventral anterior ectoderm differentially proliferates. Contraction of the musculature occurs as the head region retracts into the trunk and resolves the definitive larval body plan. Despite obvious developmental differences with C. elegans and D. melanogaster, the expression in P. caudatus of the gut-related candidate genes NK2.1, foxQ2, FGF8/17/18, GATA456, HNF4, wnt1, and evx demonstrate three distinct evolutionarily conserved molecular profiles that correlate with morphologically identified sub-regions of the gut. Conclusions The comparative analysis of priapulid development suggests that a midgut formed by a single endodermal population of vegetal cells, a ventral mouth, and the blastoporal origin of the anus are ancestral features in the Ecdysozoa. Our molecular data on P. caudatus reveal a conserved ecdysozoan gut-patterning program and demonstrates that extreme morphological divergence has not been accompanied by major molecular innovations in transcriptional regulators during digestive system evolution in the Ecdysozoa. Our data help us understand the origins of the ecdysozoan body plan, including those of C. elegans and D. melanogaster, and this is critical for comparisons between these two prominent model systems and their vertebrate counterparts. Electronic supplementary material The online version of this article (doi:10.1186/s12915-015-0139-z) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- José M Martín-Durán
- Sars International Centre for Marine Molecular Biology, University of Bergen, Thormøhlensgate 55, 5008, Bergen, Norway.
| | - Andreas Hejnol
- Sars International Centre for Marine Molecular Biology, University of Bergen, Thormøhlensgate 55, 5008, Bergen, Norway.
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18
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Kelley M, Yochem J, Krieg M, Calixto A, Heiman MG, Kuzmanov A, Meli V, Chalfie M, Goodman MB, Shaham S, Frand A, Fay DS. FBN-1, a fibrillin-related protein, is required for resistance of the epidermis to mechanical deformation during C. elegans embryogenesis. eLife 2015; 4. [PMID: 25798732 PMCID: PMC4395870 DOI: 10.7554/elife.06565] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2015] [Accepted: 03/20/2015] [Indexed: 12/19/2022] Open
Abstract
During development, biomechanical forces contour the body and provide shape to internal organs. Using genetic and molecular approaches in combination with a FRET-based tension sensor, we characterized a pulling force exerted by the elongating pharynx (foregut) on the anterior epidermis during C. elegans embryogenesis. Resistance of the epidermis to this force and to actomyosin-based circumferential constricting forces is mediated by FBN-1, a ZP domain protein related to vertebrate fibrillins. fbn-1 was required specifically within the epidermis and FBN-1 was expressed in epidermal cells and secreted to the apical surface as a putative component of the embryonic sheath. Tiling array studies indicated that fbn-1 mRNA processing requires the conserved alternative splicing factor MEC-8/RBPMS. The conserved SYM-3/FAM102A and SYM-4/WDR44 proteins, which are linked to protein trafficking, function as additional components of this network. Our studies demonstrate the importance of the apical extracellular matrix in preventing mechanical deformation of the epidermis during development. DOI:http://dx.doi.org/10.7554/eLife.06565.001 For an animal embryo to develop, its cells must organize themselves into tissues and organs. For example, skin and the lining of internal organs—such as the lungs and gut—are made from cells called epithelial cells, which are tightly linked to form flat sheets. In a microscopic worm called Caenorhabditis elegans, the outermost layer of epithelial cells (called the epidermis) forms over the surface of the embryo early on in embryonic development. Shortly afterwards, the embryonic epidermis experiences powerful contractions along the surface of the embryo. The force generated by these contractions converts the embryo from an oval shape to a roughly cylindrical form. These contractions also squeeze the internal tissues and organs, which correspondingly elongate along with the epidermis. It has been known for decades that such ‘mechanical’ forces are important for the normal development of embryos. However, it remains poorly understood how these forces generate tissues and organs of the proper shape—partly because it is difficult to measure forces in living embryos. It is also not clear how the mechanical properties of specific tissues are controlled. Now, Kelley, Yochem, Krieg et al. have analyzed the development of C. elegans' embryos and discovered a novel mechanical interplay between the feeding organ (called the pharynx) and the worm's epidermis. The experiments involved studying several mutant worms that perturb epidermal contractions and disrupt the attachment of the pharynx to the epidermis. These studies suggested that the pharynx exerts a strong inward pulling force on the epidermis during development. Using recently developed methods, Kelley, Yochem, Krieg et al. then measured mechanical forces within intact worm embryos and demonstrated that greater forces were experienced in cells that were being pulled by the pharynx. Kelley, Yochem, Krieg et al. further analyzed how the epidermis normally resists this pulling force from the pharynx and implicated a protein called FBN-1. This worm protein is structurally related to a human protein that is affected in people with a disorder called Marfan Syndrome. Worm embryos without the FBN-1 protein become severely deformed because they are unable to withstand mechanical forces at the epidermis. FBN-1 is normally synthesized and then transported to the outside of the worm embryo by epidermal cells, where it is thought to assemble into a meshwork of long fibers. This provides a strong scaffold that attaches to the epidermis to prevent the epidermis from undergoing excessive deformation while it experiences mechanical forces. The work of Kelley, Yochem, Krieg et al. provides an opportunity to understand how FBN-1 and other fiber-forming proteins are produced and transported to the cell surface. Moreover, these findings may have implications for human diseases and birth defects that result from an inability of tissues to respond appropriately to mechanical forces. DOI:http://dx.doi.org/10.7554/eLife.06565.002
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Affiliation(s)
- Melissa Kelley
- Department of Molecular Biology, University of Wyoming, Laramie, United States
| | - John Yochem
- Department of Molecular Biology, University of Wyoming, Laramie, United States
| | - Michael Krieg
- Department of Molecular and Cellular Physiology, Stanford University, Stanford, United States
| | - Andrea Calixto
- Department of Biological Sciences, Columbia University, New York, United States
| | - Maxwell G Heiman
- Department of Genetics, Harvard Medical School, Boston Children's Hospital, Boston, United States
| | - Aleksandra Kuzmanov
- Department of Molecular Biology, University of Wyoming, Laramie, United States
| | - Vijaykumar Meli
- Department of Biological Chemistry, David Geffen School of Medicine, University of California, Los Angeles, United States
| | - Martin Chalfie
- Department of Biological Sciences, Columbia University, New York, United States
| | - Miriam B Goodman
- Department of Molecular and Cellular Physiology, Stanford University, Stanford, United States
| | - Shai Shaham
- Laboratory of Developmental Genetics, The Rockefeller University, New York, United States
| | - Alison Frand
- Department of Biological Chemistry, David Geffen School of Medicine, University of California, Los Angeles, United States
| | - David S Fay
- Department of Molecular Biology, University of Wyoming, Laramie, United States
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19
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Von Stetina SE, Mango SE. PAR-6, but not E-cadherin and β-integrin, is necessary for epithelial polarization in C. elegans. Dev Biol 2015; 403:5-14. [PMID: 25773364 DOI: 10.1016/j.ydbio.2015.03.002] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2014] [Revised: 01/29/2015] [Accepted: 03/04/2015] [Indexed: 10/23/2022]
Abstract
Cell polarity is a fundamental characteristic of epithelial cells. Classical cell biological studies have suggested that establishment and orientation of polarized epithelia depend on outside-in cues that derive from interactions with either neighboring cells or the substratum (Akhtar and Streuli, 2013; Chen and Zhang, 2013; Chung and Andrew, 2008; McNeill et al., 1990; Nejsum and Nelson, 2007; Nelson et al., 2013; Ojakian and Schwimmer, 1994; Wang et al., 1990; Yu et al., 2005). This paradigm has been challenged by examples of epithelia generated in the absence of molecules that mediate cell-cell or cell-matrix interactions, notably E-cadherin and integrins (Baas et al., 2004; Choi et al., 2013; Costa et al., 1998; Harris and Peifer, 2004; Raich et al., 1999; Roote and Zusman, 1995; Vestweber et al., 1985; Williams and Waterston, 1994; Wu et al., 2009). Here we explore an alternative hypothesis, that cadherins and integrins function redundantly to substitute for one another during epithelium formation (Martinez-Rico et al., 2010; Ojakian et al., 2001; Rudkouskaya et al., 2014; Weber et al., 2011). We use C. elegans, which possesses a single E-cadherin (Costa et al., 1998; Hardin et al., 2013; Tepass, 1999) and a single β-integrin (Gettner et al., 1995; Lee et al., 2001), and analyze the arcade cells, which generate an epithelium late in embryogenesis (Portereiko and Mango, 2001; Portereiko et al., 2004), after most maternal factors are depleted. Loss of E-cadherin(HMR-1) in combination with β-integrin(PAT-3) had no impact on the onset or formation of the arcade cell epithelium, nor the epidermis or digestive tract. Moreover, ß-integrin(PAT-3) was not enriched at the basal surface of the arcades, and the candidate PAT-3 binding partner β-laminin(LAM-1) was not detected until after arcade cell polarity was established and exhibited no obvious polarity defect when mutated. Instead, the polarity protein par-6 (Chen and Zhang, 2013; Watts et al., 1996) was required to polarize the arcade cells, and par-6 mutants exhibited mislocalized or absent apical and junctional proteins. We conclude that the arcade cell epithelium polarizes by a PAR-6-mediated pathway that is independent of E-cadherin, β-integrin and β-laminin.
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Affiliation(s)
- Stephen E Von Stetina
- Department of Molecular and Cellular Biology, Harvard University, Boston, MA 02138, USA.
| | - Susan E Mango
- Department of Molecular and Cellular Biology, Harvard University, Boston, MA 02138, USA.
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20
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Abstract
PHA-1 encodes a cytoplasmic protein that is required for embryonic morphogenesis and attachment of the foregut (pharynx) to the mouth (buccal capsule). Previous reports have in some cases suggested that PHA-1 is essential for the differentiation of most or all pharyngeal cell types. By performing mosaic analysis with a recently acquired pha-1 null mutation (tm3671), we found that PHA-1 is not required within most or all pharyngeal cells for their proper specification, differentiation, or function. Rather, our evidence suggests that PHA-1 acts in the arcade or anterior epithelial cells of the pharynx to promote attachment of the pharynx to the future buccal capsule. In addition, PHA-1 appears to be required in the epidermis for embryonic morphogenesis, in the excretory system for osmoregulation, and in the somatic gonad for normal ovulation and fertility. PHA-1 activity is also required within at least a subset of intestinal cells for viability. To better understand the role of PHA-1 in the epidermis, we analyzed several apical junction markers in pha-1(tm3671) homozygous embryos. PHA-1 regulates the expression of several components of two apical junction complexes including AJM-1–DLG-1/discs large complex and the classical cadherin–catenin complex, which may account for the role of PHA-1 in embryonic morphogenesis.
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21
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Pilon M. Developmental genetics of the Caenorhabditis elegans pharynx. WILEY INTERDISCIPLINARY REVIEWS. DEVELOPMENTAL BIOLOGY 2014; 3:263-80. [PMID: 25262818 PMCID: PMC4314705 DOI: 10.1002/wdev.139] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/03/2014] [Revised: 04/03/2014] [Accepted: 04/15/2014] [Indexed: 11/07/2022]
Abstract
The Caenorhabditis elegans pharynx is a rhythmically pumping organ composed initially of 80 cells that, through fusions, amount to 62 cells in the adult worm. During the first 100 min of development, most future pharyngeal cells are born and gather into a double-plate primordium surrounded by a basal lamina. All pharyngeal cells express the transcription factor PHA-4, of which the concentration increases throughout development, triggering a sequential activation of genes with promoters responding differentially to PHA-4 protein levels. The oblong-shaped pharyngeal primordium becomes polarized, many cells taking on wedge shapes with their narrow ends toward the center, hence forming an epithelial cyst. The primordium then elongates, and reorientations of the cells at the anterior and posterior ends form the mouth and pharyngeal-intestinal openings, respectively. The 20 pharyngeal neurons establish complex but reproducible trajectories using 'fishing line' and growth cone-driven mechanisms, and the gland cells also similarly develop their processes. The genetics behind many fate decisions and morphogenetic processes are being elucidated, and reveal the pharynx to be a fruitful model for developmental biologists.
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Affiliation(s)
- Marc Pilon
- Department of Chemistry and Molecular Biology, University of GothenburgGothenburg, Sweden
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22
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Polley SRG, Kuzmanov A, Kuang J, Karpel J, Lažetić V, Karina EI, Veo BL, Fay DS. Implicating SCF complexes in organogenesis in Caenorhabditis elegans. Genetics 2014; 196:211-23. [PMID: 24214340 PMCID: PMC3872186 DOI: 10.1534/genetics.113.158485] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2013] [Accepted: 10/29/2013] [Indexed: 11/18/2022] Open
Abstract
Development of the Caenorhabditis elegans foregut (pharynx) is regulated by a network of proteins that includes the Retinoblastoma protein (pRb) ortholog LIN-35; the ubiquitin pathway components UBC-18 and ARI-1; and PHA-1, a cytoplasmic protein. Loss of pha-1 activity impairs pharyngeal development and body morphogenesis, leading to embryonic arrest. We have used a genetic suppressor approach to dissect this complex pathway. The lethality of pha-1 mutants is suppressed by loss-of-function mutations in sup-35/ztf-21 and sup-37/ztf-12, which encode Zn-finger proteins, and by mutations in sup-36. Here we show that sup-36 encodes a divergent Skp1 family member that binds to several F-box proteins and the microtubule-associated protein PLT-1/τ. Like SUP-35, SUP-36 levels were negatively regulated by UBC-18-ARI-1. We also found that SUP-35 and SUP-37 physically associated and that SUP-35 could bind microtubules. Thus, SUP-35, SUP-36, and SUP-37 may function within a pathway or complex that includes cytoskeletal components. Additionally, SUP-36 may regulate the subcellular localization of SUP-35 during embryogenesis. We carried out a genome-wide RNAi screen to identify additional regulators of this network and identified 39 genes, most of which are associated with transcriptional regulation. Twenty-three of these genes acted via the LIN-35 pathway. In addition, several S-phase kinase-associated protein (Skp)1-Cullin-F-Box (SCF) components were identified, further implicating SCF complexes as part of the greater network controlling pharyngeal development.
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Affiliation(s)
| | | | | | | | - Vladimir Lažetić
- Department of Molecular Biology, College of Agriculture and Natural Resources, University of Wyoming, Laramie, Wyoming 82071
| | - Evguenia I. Karina
- Department of Molecular Biology, College of Agriculture and Natural Resources, University of Wyoming, Laramie, Wyoming 82071
| | - Bethany L. Veo
- Department of Molecular Biology, College of Agriculture and Natural Resources, University of Wyoming, Laramie, Wyoming 82071
| | - David S. Fay
- Department of Molecular Biology, College of Agriculture and Natural Resources, University of Wyoming, Laramie, Wyoming 82071
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23
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Refai O, Rohs P, Mains PE, Gaudet J. Extension of the Caenorhabditis elegans Pharyngeal M1 neuron axon is regulated by multiple mechanisms. G3 (BETHESDA, MD.) 2013; 3:2015-29. [PMID: 24048649 PMCID: PMC3815062 DOI: 10.1534/g3.113.008466] [Citation(s) in RCA: 6] [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: 07/17/2013] [Accepted: 09/10/2013] [Indexed: 02/07/2023]
Abstract
The guidance of axons to their correct targets is a critical step in development. The C. elegans pharynx presents an attractive system to study neuronal pathfinding in the context of a developing organ. The worm pharynx contains relatively few cells and cell types, but each cell has a known lineage and stereotyped developmental patterns. We found that extension of the M1 pharyngeal axon, which spans the entire length of the pharynx, occurs in two distinct phases. The first proximal phase does not require genes that function in axon extension (unc-34, unc-51, unc-115, and unc-119), whereas the second distal phase does use these genes and is guided in part by the adjacent g1P gland cell projection. unc-34, unc-51, and unc-115 had incompletely penetrant defects and appeared to act in conjunction with the g1P cell for distal outgrowth. Only unc-119 showed fully penetrant defects for the distal phase. Mutations affecting classical neuronal guidance cues (Netrin, Semaphorin, Slit/Robo, Ephrin) or adhesion molecules (cadherin, IgCAM) had, at best, weak effects on the M1 axon. None of the mutations we tested affected the proximal phase of M1 elongation. In a forward genetic screen, we isolated nine mutations in five genes, three of which are novel, showing defects in M1, including axon overextension, truncation, or ectopic branching. One of these mutations appeared to affect the generation or differentiation of the M1 neuron. We conclude that M1 axon extension is a robust process that is not completely dependent on any single guidance mechanism.
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Affiliation(s)
- Osama Refai
- Department of Biochemistry and Molecular Biology, Alberta Children’s Hospital Research Institute, University of Calgary, Calgary, Alberta T2N 4N1, Canada
| | - Patricia Rohs
- Department of Biochemistry and Molecular Biology, Alberta Children’s Hospital Research Institute, University of Calgary, Calgary, Alberta T2N 4N1, Canada
| | - Paul E. Mains
- Department of Biochemistry and Molecular Biology, Alberta Children’s Hospital Research Institute, University of Calgary, Calgary, Alberta T2N 4N1, Canada
| | - Jeb Gaudet
- Department of Biochemistry and Molecular Biology, Alberta Children’s Hospital Research Institute, University of Calgary, Calgary, Alberta T2N 4N1, Canada
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24
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Rasmussen JP, Feldman JL, Reddy SS, Priess JR. Cell interactions and patterned intercalations shape and link epithelial tubes in C. elegans. PLoS Genet 2013; 9:e1003772. [PMID: 24039608 PMCID: PMC3764189 DOI: 10.1371/journal.pgen.1003772] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2013] [Accepted: 07/19/2013] [Indexed: 01/15/2023] Open
Abstract
Many animal organs are composed largely or entirely of polarized epithelial tubes, and the formation of complex organ systems, such as the digestive or vascular systems, requires that separate tubes link with a common polarity. The Caenorhabditis elegans digestive tract consists primarily of three interconnected tubes—the pharynx, valve, and intestine—and provides a simple model for understanding the cellular and molecular mechanisms used to form and connect epithelial tubes. Here, we use live imaging and 3D reconstructions of developing cells to examine tube formation. The three tubes develop from a pharynx/valve primordium and a separate intestine primordium. Cells in the pharynx/valve primordium polarize and become wedge-shaped, transforming the primordium into a cylindrical cyst centered on the future lumenal axis. For continuity of the digestive tract, valve cells must have the same, radial axis of apicobasal polarity as adjacent intestinal cells. We show that intestinal cells contribute to valve cell polarity by restricting the distribution of a polarizing cue, laminin. After developing apicobasal polarity, many pharyngeal and valve cells appear to explore their neighborhoods through lateral, actin-rich lamellipodia. For a subset of cells, these lamellipodia precede more extensive intercalations that create the valve. Formation of the valve tube begins when two valve cells become embedded at the left-right boundary of the intestinal primordium. Other valve cells organize symmetrically around these two cells, and wrap partially or completely around the orthogonal, lumenal axis, thus extruding a small valve tube from the larger cyst. We show that the transcription factors DIE-1 and EGL-43/EVI1 regulate cell intercalations and cell fates during valve formation, and that the Notch pathway is required to establish the proper boundary between the pharyngeal and valve tubes. Tubes composed of epithelial cells are universal building blocks of animal organs, and complex organs typically contain multiple interconnected tubes, such as in the digestive tract or vascular system. The nematode Caenorhabditis elegans provides a simple genetic system to study how tubes form and link. Understanding these events provides insight into basic biology, and can inform engineering strategies for building or repairing cellular tubes. A small tube called the valve connects the two major tubular organs of the nematode digestive tract, the pharynx and intestine. The pharynx and valve form from the same primordium, while the intestine forms from a separate primordium. Cells in each primordium polarize around a central axis, and valve formation involves connecting these axes. Using live imaging, we show that valve cells initially resemble other pharyngeal cells, but undergo additional and extensive intercalations around the lumenal axis, effectively squeezing a small tube from the larger primordium. Valve cells develop the same polarity axis as intestinal cells, and we show that this depends on interactions with the intestinal cells. We show that valve formation involves dynamic changes in the localization of adhesive proteins, and identify transcription factors that play a role in valve cell specification and intercalation.
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Affiliation(s)
- Jeffrey P. Rasmussen
- Fred Hutchinson Cancer Research Center, Seattle, Washington, United States of America
- Howard Hughes Medical Institute, Chevy Chase, Maryland, United States of America
- Molecular and Cellular Biology Program, University of Washington, Seattle, Washington, United States of America
| | - Jessica L. Feldman
- Fred Hutchinson Cancer Research Center, Seattle, Washington, United States of America
- Howard Hughes Medical Institute, Chevy Chase, Maryland, United States of America
| | - Sowmya Somashekar Reddy
- Fred Hutchinson Cancer Research Center, Seattle, Washington, United States of America
- Howard Hughes Medical Institute, Chevy Chase, Maryland, United States of America
| | - James R. Priess
- Fred Hutchinson Cancer Research Center, Seattle, Washington, United States of America
- Howard Hughes Medical Institute, Chevy Chase, Maryland, United States of America
- Department of Biology, University of Washington, Seattle, Washington, United States of America
- * E-mail:
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25
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Praitis V, Simske J, Kniss S, Mandt R, Imlay L, Feddersen C, Miller MB, Mushi J, Liszewski W, Weinstein R, Chakravorty A, Ha DG, Schacht Farrell A, Sullivan-Wilson A, Stock T. The secretory pathway calcium ATPase PMR-1/SPCA1 has essential roles in cell migration during Caenorhabditis elegans embryonic development. PLoS Genet 2013; 9:e1003506. [PMID: 23696750 PMCID: PMC3656159 DOI: 10.1371/journal.pgen.1003506] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2012] [Accepted: 03/26/2013] [Indexed: 01/22/2023] Open
Abstract
Maintaining levels of calcium in the cytosol is important for many cellular events, including cell migration, where localized regions of high calcium are required to regulate cytoskeletal dynamics, contractility, and adhesion. Studies show inositol-trisphosphate receptors (IP3R) and ryanodine receptors (RyR), which release calcium into the cytosol, are important regulators of cell migration. Similarly, proteins that return calcium to secretory stores are likely to be important for cell migration. The secretory protein calcium ATPase (SPCA) is a Golgi-localized protein that transports calcium from the cytosol into secretory stores. SPCA has established roles in protein processing, metal homeostasis, and inositol-trisphosphate signaling. Defects in the human SPCA1/ATP2C1 gene cause Hailey-Hailey disease (MIM# 169600), a genodermatosis characterized by cutaneous blisters and fissures as well as keratinocyte cell adhesion defects. We have determined that PMR-1, the Caenorhabditis elegans ortholog of SPCA1, plays an essential role in embryogenesis. Pmr-1 strains isolated from genetic screens show terminal phenotypes, such as ventral and anterior enclosure failures, body morphogenesis defects, and an unattached pharynx, which are caused by earlier defects during gastrulation. In Pmr-1 embryos, migration rates are significantly reduced for cells moving along the embryo surface, such as ventral neuroblasts, C-derived, and anterior-most blastomeres. Gene interaction experiments show changing the activity of itr-1/IP3R and unc-68/RyR modulates levels of embryonic lethality in Pmr-1 strains, indicating pmr-1 acts with these calcium channels to regulate cell migration. This analysis reveals novel genes involved in C. elegans cell migration, as well as a new role in cell migration for the highly conserved SPCA gene family. During growth or regeneration after damage, skin cells migrate from basal to superficial layers, forming tight attachments that protect an individual from environmental assaults. Proteins that remove calcium from the cell cytosol into secretory stores, where it is available for future release, play a key role in skin cell integrity. Defects in these secretory pathway calcium ATPase (SPCA) channels in humans cause Hailey-Hailey disease, a chronic disorder marked by skin lesions in areas of high-stress. Our study of the SPCA gene pmr-1 in Caenorhabditis elegans indicates the gene is essential for viability. Embryos with defective PMR-1 die with cell attachment defects superficially similar to those of Hailey-Hailey disease patients. To better understand this phenotype, we tracked the position of individual cells during development of pmr-1 mutant embryos. This analysis revealed that the cell attachment defects are caused by primary failures in cell migration. We also identified other calcium channel proteins involved in this process, indicating proper regulation of calcium is crucial for cell migration in C. elegans. If SPCA proteins act similarly in humans, this research will lead to better understanding of the molecules important for skin cell regeneration, as well as help to explain the defects observed in Hailey-Hailey disease patients.
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Affiliation(s)
- Vida Praitis
- Biology Department, Grinnell College, Grinnell, IA, USA.
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Abstract
Interconnection of epithelial tubules is a crucial process during organogenesis. Organisms have evolved sets of molecular and cellular strategies to generate an interconnected tubular network during animal development. Spatiotemporal control of common cellular strategies includes dissolution of the basement membrane, apoptosis, rearrangements of cell adhesion junctions, and mesenchymal-like invasive cellular behaviors prior to tubular interconnection. Different model systems exhibit varying degrees of active invasive-like behaviors that precede tubular interconnection, which may reflect changes in cell polarity or differential adhesive cell states. Studies in this newly-emerging field of tubular interconnections will provide a greater understanding of pediatric diseases and cancer metastasis, as well as generate fundamentally new insights into lumen formation pathology, or lumopathies.
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Affiliation(s)
- Robert M Kao
- Departments of Molecular and Cellular Biology and Stem Cell and Regenerative Biology, Harvard University, Cambridge, MA, USA.
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Kao RM, Vasilyev A, Miyawaki A, Drummond IA, McMahon AP. Invasion of distal nephron precursors associates with tubular interconnection during nephrogenesis. J Am Soc Nephrol 2012; 23:1682-90. [PMID: 22904347 DOI: 10.1681/asn.2012030283] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
Formation of a functional renal network requires the interconnection of two epithelial tubes: the nephron, which arises from kidney mesenchyme, and the collecting system, which originates from the branching ureteric epithelium. How this connection occurs, however, is incompletely understood. Here, we used high-resolution image analysis in conjunction with genetic labeling of epithelia to visualize and characterize this process. Although the focal absence of basal lamina from renal vesicle stages ensures that both epithelial networks are closely apposed, we found that a patent luminal interconnection is not established until S-shaped body stages. Precursor cells of the distal nephron in the interconnection zone exhibit a characteristic morphology consisting of ill-defined epithelial junctional complexes but without expression of mesenchymal markers such as vimentin and Snai2. Live-cell imaging revealed that before luminal interconnection, distal cells break into the lumen of the collecting duct epithelium, suggesting that an invasive behavior is a key step in the interconnection process. Furthermore, loss of distal cell identity, which we induced by activating the Notch pathway, prevented luminal interconnection. Taken together, these data support a model in which establishing the distal identity of nephron precursor cells closest to the nascent collecting duct epithelium leads to an active cell invasion, which in turn contributes to a patent tubular interconnection between the nephron and collecting duct epithelia.
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Affiliation(s)
- Robert M Kao
- Department of Stem Cell Biology and Regenerative Medicine, Broad-CIRM Center, Keck School of Medicine, University of Southern California, 1425 San Pablo Street, Los Angeles, CA 90089, USA
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A regulatory module controlling pharyngeal development and function in Caenorhabditis elegans. Genetics 2012; 191:827-43. [PMID: 22542967 DOI: 10.1534/genetics.112.140814] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
In Caenorhabditis elegans, the differentiation and morphogenesis of the foregut are controlled by several transcriptional regulators and cell signaling events, and by PHA-1, an essential cytoplasmic protein of unknown function. Previously we have shown that LIN-35 and UBC-18-ARI-1 contribute to the regulation of pha-1 and pharyngeal development through the Zn-finger protein SUP-35/ZTF-21. Here we characterize SUP-37/ZTF-12 as an additional component of the PHA-1 network regulating pharyngeal development. SUP-37 is encoded by four distinct splice isoforms, which contain up to seven C2H2 Zn-finger domains, and is localized to the nucleus, suggesting a role in transcription. Similar to sup-35, sup-37 loss-of-function mutations can suppress both LOF mutations in pha-1 as well as synthetic-lethal double mutants, including lin-35; ubc-18, which are defective in pharyngeal development. Genetic, molecular, and expression data further indicate that SUP-37 and SUP-35 may act at a common step to control pharyngeal morphogenesis, in part through the transcriptional regulation of pha-1. Moreover, we find that SUP-35 and SUP-37 effect pharyngeal development through a mechanism that can genetically bypass the requirement for pha-1 activity. Unlike SUP-35, SUP-37 expression is not regulated by either the LIN-35 or UBC-18-ARI-1 pathways. In addition, SUP-37 carries out two essential functions that are distinct from its role in regulating pharyngeal development with SUP-35. SUP-37 is required within a subset of pharyngeal muscle cells to facilitate coordinated rhythmic pumping and in the somatic gonad to promote ovulation. These latter observations suggest that SUP-37 may be required for the orchestrated contraction of muscle cells within several tissues.
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29
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Rasmussen JP, Reddy SS, Priess JR. Laminin is required to orient epithelial polarity in the C. elegans pharynx. Development 2012; 139:2050-60. [PMID: 22535412 DOI: 10.1242/dev.078360] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The development of many animal organs involves a mesenchymal to epithelial transition, in which cells develop and coordinate polarity through largely unknown mechanisms. The C. elegans pharynx, which is an epithelial tube in which cells polarize around a central lumen, provides a simple system with which to understand the coordination of epithelial polarity. We show that cell fate regulators cause pharyngeal precursor cells to group into a bilaterally symmetric, rectangular array of cells called the double plate. The double plate cells polarize with apical localization of the PAR-3 protein complex, then undergo apical constriction to form a cylindrical cyst. We show that laminin, but not other basement membrane components, orients the polarity of the double plate cells. Our results provide in vivo evidence that laminin has an early role in cell polarity that can be distinguished from its later role in basement membrane integrity.
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30
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Cell architecture: surrounding muscle cells shape gland cell morphology in the Caenorhabditis elegans pharynx. Genetics 2011; 189:885-97. [PMID: 21868609 PMCID: PMC3213386 DOI: 10.1534/genetics.111.132449] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The acquisition and maintenance of shape is critical for the normal function of most cells. Here we investigate the morphology of the pharyngeal glands of Caenorhabditis elegans. These unicellular glands have long cellular processes that extend discrete lengths through the pharyngeal musculature and terminate at ducts connected to the pharyngeal lumen. From a genetic screen we identified several mutants that affect pharyngeal gland morphology. The most severe such mutant is an allele of sma-1, which encodes a β-spectrin required for embryonic elongation, including elongation of the pharynx. In sma-1 mutants, gland projections form normally but become increasingly abnormal over time, acquiring additional branches, outgrowths, and swelling, suggestive of hypertrophy. Rather than acting in pharyngeal glands, sma-1 functions in the surrounding musculature, suggesting that pharyngeal muscles play a critical role in maintenance of gland morphology by restricting their growth, and analysis of other mutants known to affect pharyngeal muscles supports this hypothesis. We suggest that gland morphology is maintained by a balance of forces from the muscles and the glands.
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31
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Abstract
The ability to manipulate the genome of organisms at will is perhaps the single most useful ability for the study of biological systems. Techniques for the generation of transgenics in the nematode Caenorhabditis elegans became available in the late 1980s. Since then, improvements to the original approach have been made to address specific limitations with transgene expression, expand on the repertoire of the types of biological information that transgenes can provide, and begin to develop methods to target transgenes to defined chromosomal locations. Many recent, detailed protocols have been published, and hence in this chapter, we will review various approaches to making C. elegans transgenics, discuss their applications, and consider their relative advantages and disadvantages. Comments will also be made on anticipated future developments and on the application of these methods to other nematodes.
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Affiliation(s)
- Vida Praitis
- Biology Department, Grinnell College, Grinnell, Iowa, USA
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32
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RAGSDALE ERIKJ, NGO PHUONGT, CRUM JOHN, ELLISMAN MARKH, BALDWIN JAMESG. Reconstruction of the pharyngeal corpus of Aphelenchus avenae (Nematoda: Tylenchomorpha), with implications for phylogenetic congruence. Zool J Linn Soc 2010. [DOI: 10.1111/j.1096-3642.2009.00632.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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33
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O'Rourke SM, Christensen SN, Bowerman B. Caenorhabditis elegans EFA-6 limits microtubule growth at the cell cortex. Nat Cell Biol 2010; 12:1235-41. [PMID: 21076413 DOI: 10.1038/ncb2128] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2010] [Accepted: 10/18/2010] [Indexed: 01/01/2023]
Abstract
Microtubules are polymers of tubulin heterodimers that exhibit dynamic instability: periods of growth followed by periods of shrinkage. However, the molecular regulation of dynamic instability remains elusive. Here, we show that EFA-6, a cortically-localized protein, limits the growth of microtubules near the cell cortex of early embryonic cells from Caenorhabditis elegans, possibly by inducing microtubule catastrophes. Compared with wild type, embryos lacking EFA-6 had abnormally long and dense microtubules at the cell cortex, and growing microtubule plus ends resided at the cortex for up to five-fold longer. Loss of EFA-6 also caused excess centrosome separation and displacement towards the cell cortex early in mitosis, and subsequently a loss of anaphase spindle-pole oscillations and increased rates of spindle elongation. The centrosome separation phenotype was dependent on the motor protein dynein, suggesting a possible link between the modulation of microtubule dynamics at the cortex and dynein-dependent force production. EFA-6 orthologues activate ARF6-type GTPases to regulate vesicle trafficking. However, we show that only the C. elegans EFA-6 amino-terminus is both necessary and sufficient to limit microtubule growth along the cortex, and that this function is independent of ARF-6.
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Affiliation(s)
- Sean M O'Rourke
- Institute of Molecular Biology, 1229 University of Oregon, Eugene, Oregon 97403, USA
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34
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Genetics of extracellular matrix remodeling during organ growth using the Caenorhabditis elegans pharynx model. Genetics 2010; 186:969-82. [PMID: 20805556 DOI: 10.1534/genetics.110.120519] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The organs of animal embryos are typically covered with an extracellular matrix (ECM) that must be carefully remodeled as these organs enlarge during post-embryonic growth; otherwise, their shape and functions may be compromised. We previously described the twisting of the Caenorhabditis elegans pharynx (here called the Twp phenotype) as a quantitative mutant phenotype that worsens as that organ enlarges during growth. Mutations previously known to cause pharyngeal twist affect membrane proteins with large extracellular domains (DIG-1 and SAX-7), as well as a C. elegans septin (UNC-61). Here we show that two novel alleles of the C. elegans papilin gene, mig-6(et4) and mig-6(sa580), can also cause the Twp phenotype. We also show that overexpression of the ADAMTS protease gene mig-17 can suppress the pharyngeal twist in mig-6 mutants and identify several alleles of other ECM-related genes that can cause or influence the Twp phenotype, including alleles of fibulin (fbl-1), perlecan (unc-52), collagens (cle-1, dpy-7), laminins (lam-1, lam-3), one ADAM protease (sup-17), and one ADAMTS protease (adt-1). The Twp phenotype in C. elegans is easily monitored using light microscopy, is quantitative via measurements of the torsion angle, and reveals that ECM components, metalloproteinases, and ECM attachment molecules are important for this organ to retain its correct shape during post-embryonic growth. The Twp phenotype is therefore a promising experimental system to study ECM remodeling and diseases.
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35
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Aviles-Espinosa R, Santos SICO, Brodschelm A, Kaenders WG, Alonso-Ortega C, Artigas D, Loza-Alvarez P. Third-harmonic generation for the study of Caenorhabditis elegans embryogenesis. JOURNAL OF BIOMEDICAL OPTICS 2010; 15:046020. [PMID: 20799822 DOI: 10.1117/1.3477535] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/19/2023]
Abstract
Live microscopy techniques (i.e., differential interference contrast, confocal microscopy, etc.) have enabled the understanding of the mechanisms involved in cells and tissue formation. In long-term studies, special care must be taken in order to avoid sample damage, restricting the applicability of the different microscopy techniques. We demonstrate the potential of using third-harmonic generation (THG) microscopy for morphogenesis/embryogenesis studies in living Caenorhabditis elegans (C. elegans). Moreover, we show that the THG signal is obtained in all the embryo development stages, showing different tissue/structure information. For this research, we employ a 1550-nm femtosecond fiber laser and demonstrate that the expected water absorption at this wavelength does not severely compromise sample viability. Additionally, this has the important advantage that the THG signal is emitted at visible wavelengths (516 nm). Therefore, standard collection optics and detectors operating near maximum efficiency enable an optimal signal reconstruction. All this, to the best of our knowledge, demonstrates for the first time the noninvasiveness and strong potential of this particular wavelength to be used for high-resolution four-dimensional imaging of embryogenesis using unstained C. elegans in vivo samples.
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Affiliation(s)
- Rodrigo Aviles-Espinosa
- Institut de Ciencies Fotoniques, The Institute of Photonic Sciences, Mediterranean Technology Park, Barcelona, Spain
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36
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Kormish JD, Gaudet J, McGhee JD. Development of the C. elegans digestive tract. Curr Opin Genet Dev 2010; 20:346-54. [PMID: 20570129 DOI: 10.1016/j.gde.2010.04.012] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2010] [Revised: 04/20/2010] [Accepted: 04/24/2010] [Indexed: 12/11/2022]
Abstract
The C. elegans digestive tract (pharynx, intestine, and rectum) contains only approximately 100 cells but develops under the control of the same types of transcription factors (e.g. FoxA and GATA factors) that control digestive tract development in far more complex animals. The GATA-factor dominated core regulatory hierarchy directing development of the homogenous clonal intestine from oocyte to mature organ is now known with some degree of certainty, setting the stage for more biochemical experiments to understand developmental mechanisms. The FoxA-factor dominated development of the pharynx (and rectum) is less well understood but is beginning to reveal how transcription factor combinations produce unique cell types within organs.
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Affiliation(s)
- Jay D Kormish
- Department of Molecular Biology and Biochemistry, Department of Medical Genetics, Alberta Children's Hospital Research Institute for Child and Maternal Health, University of Calgary, Calgary, Alberta, Canada
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37
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The conserved miR-51 microRNA family is redundantly required for embryonic development and pharynx attachment in Caenorhabditis elegans. Genetics 2010; 185:897-905. [PMID: 20421599 DOI: 10.1534/genetics.110.117515] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
microRNAs (miRNAs) are approximately 22-nucleotide small RNAs that act as endogenous regulators of gene expression by base-pairing with target mRNAs. Here we analyze the function of the six members of the Caenorhabditis elegans miR-51 family of miRNAs (miR-51, miR-52, miR-53, miR-54, miR-55, miR-56). miR-51 family miRNAs are broadly expressed from mid-embryogenesis onward. The miR-51 family is redundantly required for embryonic development. mir-51 family mutants display a highly penetrant pharynx unattached (Pun) phenotype, where the pharyngeal muscle, the food pump of C. elegans, is not attached to the mouth. Unusually, the Pun phenotype in mir-51 family mutants is not due to a failure to attach, but instead a failure to maintain attachment during late embryogenesis. Expression of the miR-51 family in the mouth is sufficient to maintain attachment. The Fat cadherin ortholog CDH-3 is expressed in the mouth and is a direct target of the miR-51 family miRNAs. Genetic analysis reveals that miR-51 family miRNAs might act in part through CDH-3 to regulate pharynx attachment. This study is the first to assign a function to the miR-51/miR-100 miRNA family in any organism.
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38
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Carberry K, Wiesenfahrt T, Windoffer R, Bossinger O, Leube RE. Intermediate filaments in Caenorhabditis elegans. ACTA ACUST UNITED AC 2009; 66:852-64. [PMID: 19437512 DOI: 10.1002/cm.20372] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Intermediate filaments (IFs) make up one of the three major fibrous cytoskeletal systems in metazoans. Numerous IF polypeptides are synthesized in cell type-specific combinations suggesting specialized functions. The review concentrates on IFs in the model organism Caenorhabditis elegans which carries great promise to elucidate the still unresolved mechanisms of IF assembly into complex networks and to determine IF function in a living organism. In contrast to Drosophila melanogaster, which lacks cytoplasmic IFs altogether, the nematode genome contains 11 genes coding for cytoplasmic IFs and only a single gene for a nuclear lamin. Its cytoplasmic IFs are expressed in developmentally and spatially defined patterns. As an example we present the case of the intestinal IFs which are abundant in the mechanically resilient endotube, a prominent feature of the C. elegans intestinal terminal web region. This IF-rich structure brings together all three cytoskeletal filaments that are integrated into a coherent entity by the C. elegans apical junction (CeAJ) thereby completely surrounding and stabilizing the intestinal lumen with its characteristic brush border. Concepts on the developmental establishment of the endotube in relation to polarization and its function for maintenance of epithelial integrity are discussed. Furthermore, possible connections of the cytoplasmic cytoskeleton to the nuclear lamin IFs and the importance of these links for nuclear positioning are summarized.
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Affiliation(s)
- Katrin Carberry
- Institute of Molecular and Cellular Anatomy, RWTH Aachen University, 52074 Aachen, Germany
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39
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Kang J, Shin D, Yu JR, Lee J. Lats kinase is involved in the intestinal apical membrane integrity in the nematode Caenorhabditis elegans. Development 2009; 136:2705-15. [PMID: 19605499 DOI: 10.1242/dev.035485] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The roles of Lats kinases in the regulation of cell proliferation and apoptosis have been well established. Here we report new roles for Lats kinase in the integrity of the apical membrane structure. WTS-1, the C. elegans Lats homolog, localized primarily to the subapical region in the intestine. A loss-of-function mutation in wts-1 resulted in an early larval arrest and defects in the structure of the intestinal lumen. An electron microscopy study of terminally arrested wts-1 mutant animals revealed numerous microvilli-containing lumen-like structures within the intestinal cells. The wts-1 phenotype was not caused by cell proliferation or apoptosis defects. Instead, we found that the wts-1 mutant animals exhibited gradual mislocalization of apical actin and apical junction proteins, suggesting that wts-1 normally suppresses the formation of extra apical membrane structures. Heat-shock-driven pulse-chase expression experiments showed that WTS-1 regulates the localization of newly synthesized apical actins. RNAi of the exocyst complex genes suppressed the mislocalization phenotype of wts-1 mutation. Collectively, the data presented here suggest that Lats kinase plays important roles in the integrity of the apical membrane structure of intestinal cells.
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Affiliation(s)
- Junsu Kang
- Research Center for Functional Cellulomics, Institute of Molecular Biology and Genetics, School of Biological Sciences, Seoul National University, Seoul, Korea
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40
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Abstract
The digestive tracts of many animals are epithelial tubes with specialized compartments to break down food, remove wastes, combat infection, and signal nutrient availability. C. elegans possesses a linear, epithelial gut tube with foregut, midgut, and hindgut sections. The simple anatomy belies the developmental complexity that is involved in forming the gut from a pool of heterogeneous precursor cells. Here, I focus on the processes that specify cell fates and control morphogenesis within the embryonic foregut (pharynx) and the developmental roles of the pharynx after birth. Maternally donated factors in the pregastrula embryo converge on pha-4, a FoxA transcription factor that specifies organ identity for pharyngeal precursors. Positive feedback loops between PHA-4 and other transcription factors ensure commitment to pharyngeal fate. Binding-site affinity of PHA-4 for its target promoters contributes to the progression of the pharyngeal precursors towards differentiation. During morphogenesis, the pharyngeal precursors form an epithelial tube in a process that is independent of cadherins, catenins, and integrins but requires the kinesin zen-4/MKLP1. After birth, the pharynx and/or pha-4 are involved in repelling pathogens and controlling aging.
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Affiliation(s)
- Susan E Mango
- Department of Molecular and Cellular Biology, Harvard University, Cambridge, Massachusetts, USA.
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41
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Smit RB, Schnabel R, Gaudet J. The HLH-6 transcription factor regulates C. elegans pharyngeal gland development and function. PLoS Genet 2008; 4:e1000222. [PMID: 18927627 PMCID: PMC2563036 DOI: 10.1371/journal.pgen.1000222] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2008] [Accepted: 09/11/2008] [Indexed: 12/22/2022] Open
Abstract
The Caenorhabditis elegans pharynx (or foregut) functions as a pump that draws in food (bacteria) from the environment. While the “organ identity factor” PHA-4 is critical for formation of the C. elegans pharynx as a whole, little is known about the specification of distinct cell types within the pharynx. Here, we use a combination of bioinformatics, molecular biology, and genetics to identify a helix-loop-helix transcription factor (HLH-6) as a critical regulator of pharyngeal gland development. HLH-6 is required for expression of a number of gland-specific genes, acting through a discrete cis-regulatory element named PGM1 (Pharyngeal Gland Motif 1). hlh-6 mutants exhibit a frequent loss of a subset of glands, while the remaining glands have impaired activity, indicating a role for hlh-6 in both gland development and function. Interestingly, hlh-6 mutants are also feeding defective, ascribing a biological function for the glands. Pharyngeal pumping in hlh-6 mutants is normal, but hlh-6 mutants lack expression of a class of mucin-related proteins that are normally secreted by pharyngeal glands and line the pharyngeal cuticle. An interesting possibility is that one function of pharyngeal glands is to secrete a pharyngeal lining that ensures efficient transport of food along the pharyngeal lumen. To make an organ, cells must be instructed to be part of a common structure yet must also be assigned specific roles or identities within that structure. For example, the stomach contains a variety of different kinds of cells, including muscles, nerves, and glands. This same complexity is seen even in relatively simple organs, like the pharynx (foregut) of the nematode C. elegans. The pharynx is a neuromuscular organ that pumps in food (bacteria) from the environment. This organ is relatively simple (containing only 80 cells) yet contains five distinct kinds of cells. How these different cells are specified is unclear but likely involves combinations of developmental regulators known as transcription factors. Here, we examine one cell type, the pharyngeal glands, and identify a key regulator of their development, the transcription factor HLH-6. Interestingly, HLH-6 is closely related to a mammalian transcription factor, Sgn1, which is involved in development of mammalian salivary glands, suggesting that C. elegans pharyngeal glands are evolutionarily related to mammalian salivary glands. A further connection is that the pharyngeal glands of C. elegans appear to be required for efficient feeding, possibly by secreting mucin-like proteins that ensure the smooth passage of food along the digestive tract.
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Affiliation(s)
- Ryan B. Smit
- Genes and Development Research Group, Department of Biochemistry and Molecular Biology, University of Calgary, Calgary, Alberta, Canada
| | - Ralf Schnabel
- Institut für Genetik, Technische Universität Braunschweig, Braunschweig, Germany
| | - Jeb Gaudet
- Genes and Development Research Group, Department of Biochemistry and Molecular Biology, University of Calgary, Calgary, Alberta, Canada
- Department of Medical Genetics, University of Calgary, Calgary, Alberta, Canada
- * E-mail:
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42
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Rasmussen JP, English K, Tenlen J, Priess JR. Notch signaling and morphogenesis of single-cell tubes in the C. elegans digestive tract. Dev Cell 2008; 14:559-69. [PMID: 18410731 PMCID: PMC2435507 DOI: 10.1016/j.devcel.2008.01.019] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2007] [Revised: 10/22/2007] [Accepted: 01/31/2008] [Indexed: 11/19/2022]
Abstract
During organogenesis of the C. elegans digestive system, epithelial cells within a cyst-like primordium develop diverse shapes through largely unknown mechanisms. We here analyze two adjacent, dorsal epithelial cells, called pm8 and vpi1, that remodel their shapes and apical junctions to become donut-shaped, or toroidal, single-cell tubes. pm8 and vpi1 delaminate from the dorsal cyst epithelium and migrate ventrally, across the midline of the cyst, on a transient tract of laminin. pm8 appears to encircle the midline by wrapping around finger-like projections from neighboring cells. Finally, pm8 and vpi1 self-fuse to become toroids by expressing AFF-1 and EFF-1, two fusogens that are each sufficient to promote crossfusion between other cell types. Notch signaling in pm8 induces AFF-1 expression, while simultaneously repressing EFF-1 expression; vpi1 expresses EFF-1 independent of Notch. Thus, the adjacent pm8 and vpi1 cells express different fusogens, allowing them to self-fuse into separate, single-cell tubes while avoiding crossfusion.
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Affiliation(s)
- Jeffrey P. Rasmussen
- Fred Hutchinson Cancer Research Center, Seattle, WA 98109, USA
- Howard Hughes Medical Institute
- Molecular and Cellular Biology Program, University of Washington, Seattle, WA 98195, USA
| | - Kathryn English
- Fred Hutchinson Cancer Research Center, Seattle, WA 98109, USA
- Howard Hughes Medical Institute
| | - Jennifer Tenlen
- Fred Hutchinson Cancer Research Center, Seattle, WA 98109, USA
- Howard Hughes Medical Institute
- Molecular and Cellular Biology Program, University of Washington, Seattle, WA 98195, USA
| | - James R. Priess
- Fred Hutchinson Cancer Research Center, Seattle, WA 98109, USA
- Howard Hughes Medical Institute
- Department of Biology, University of Washington, Seattle, WA 98195, USA
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The Fat-like cadherin CDH-4 controls axon fasciculation, cell migration and hypodermis and pharynx development in Caenorhabditis elegans. Dev Biol 2008; 316:249-59. [PMID: 18328472 DOI: 10.1016/j.ydbio.2008.01.024] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2007] [Revised: 01/08/2008] [Accepted: 01/12/2008] [Indexed: 02/07/2023]
Abstract
Cadherins are one of the major families of adhesion molecules with diverse functions during embryonic development. Fat-like cadherins form an evolutionarily conserved subgroup characterized by an unusually large number of cadherin repeats in the extracellular domain. Here we describe the role of the Fat-like cadherin CDH-4 in Caenorhabditis elegans development. Cdh-4 mutants are characterized by hypodermal defects leading to incompletely penetrant embryonic or larval lethality with variable morphogenetic defects. Independently of the morphogenetic defects cdh-4 mutant animals also exhibit fasciculation defects in the ventral and dorsal cord, the major longitudinal axon tracts, as well as migration defects of the Q neuroblasts. In addition CDH-4 is essential for establishing and maintaining the attachment between the buccal cavity and the pharynx. Cdh-4 is expressed widely in most affected cells and tissues during embryogenesis suggesting that CDH-4 functions to ensure that proper cell contacts are made and maintained during development.
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Diogon M, Wissler F, Quintin S, Nagamatsu Y, Sookhareea S, Landmann F, Hutter H, Vitale N, Labouesse M. The RhoGAP RGA-2 and LET-502/ROCK achieve a balance of actomyosin-dependent forces inC. elegansepidermis to control morphogenesis. Development 2007; 134:2469-79. [PMID: 17537791 DOI: 10.1242/dev.005074] [Citation(s) in RCA: 73] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Embryonic morphogenesis involves the coordinate behaviour of multiple cells and requires the accurate balance of forces acting within different cells through the application of appropriate brakes and throttles. In C. elegans, embryonic elongation is driven by Rho-binding kinase (ROCK) and actomyosin contraction in the epidermis. We identify an evolutionary conserved, actin microfilament-associated RhoGAP (RGA-2) that behaves as a negative regulator of LET-502/ROCK. The small GTPase RHO-1 is the preferred target of RGA-2 in vitro, and acts between RGA-2 and LET-502 in vivo. Two observations show that RGA-2 acts in dorsal and ventral epidermal cells to moderate actomyosin tension during the first half of elongation. First,time-lapse microscopy shows that loss of RGA-2 induces localised circumferentially oriented pulling on junctional complexes in dorsal and ventral epidermal cells. Second, specific expression of RGA-2 in dorsal/ventral, but not lateral, cells rescues the embryonic lethality of rga-2 mutants. We propose that actomyosin-generated tension must be moderated in two out of the three sets of epidermal cells surrounding the C. elegans embryo to achieve morphogenesis.
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Affiliation(s)
- Marie Diogon
- IGBMC, CNRS/INSERM/ULP, 1 rue Laurent Fries, BP.10142, 67400 Illkirch, France
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The twisted pharynx phenotype in C. elegans. BMC DEVELOPMENTAL BIOLOGY 2007; 7:61. [PMID: 17540043 PMCID: PMC1904197 DOI: 10.1186/1471-213x-7-61] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/15/2007] [Accepted: 06/01/2007] [Indexed: 11/10/2022]
Abstract
Background The pharynx of C. elegans is an epithelial tube whose development has been compared to that of the embryonic heart and the kidney and hence serves as an interesting model for organ development. Several C. elegans mutants have been reported to exhibit a twisted pharynx phenotype but no careful studies have been made to directly address this phenomenon. In this study, the twisting mutants dig-1, mig-4, mnm-4 and unc-61 are examined in detail and the nature of the twist is investigated. Results We find that the twisting phenotype worsens throughout larval development, that in most mutants the pharynx retains its twist when dissected away from the worm body, and that double mutants between mnm-4 and mutants with thickened pharyngeal domains (pha-2 and sma-1) have less twisting in these regions. We also describe the ultrastructure of pharyngeal tendinous organs that connect the pharyngeal basal lamina to that of the body wall, and show that these are pulled into a spiral orientation by twisted pharynges. Within twisted pharynges, actin filaments also show twisting and are longer than in controls. In a mini screen of adhesionmolecule mutants, we also identified one more twisting pharynx mutant, sax-7. Conclusion Defects in pharyngeal cytoskeleton length or its anchor points to the extracellular matrix are proposed as the actual source of the twisting force. The twisted pharynx is a useful and easy-to-score phenotype for genes required in extracellular adhesion or organ attachment, and perhaps forgenes required for cytoskeleton regulation.
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Estes KA, Kalamegham R, Hanna-Rose W. Membrane localization of the NlpC/P60 family protein EGL-26 correlates with regulation of vulval cell morphogenesis in Caenorhabditis elegans. Dev Biol 2007; 308:196-205. [PMID: 17560977 DOI: 10.1016/j.ydbio.2007.05.020] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2006] [Revised: 04/26/2007] [Accepted: 05/18/2007] [Indexed: 11/25/2022]
Abstract
Vulval morphogenesis in Caenorhabditis elegans generates a stack of toroidal cells enclosing a tubular lumen. Mutation of egl-26 is associated with malformation of vulF, the most dorsal toroid in the stack, resulting in a blocked lumen and an egg-laying defect. Here we present evidence that vulF retains the expected gene expression pattern, functions in signaling to the uterus and retains proper polarity when egl-26 is mutated, all suggesting that mutation of egl-26 specifically results in aberrant morphogenesis as opposed to abnormal fate specification. Recent computational analysis indicates that EGL-26, which was previously characterized as novel, belongs to the LRAT (lecithin retinol acyltransferase) subfamily of the NlpC/P60 superfamily of catalytic proteins. Via site-directed mutagenesis, we demonstrate a requirement of the putative catalytic residues for EGL-26 function in vivo. We also show that mutation of conserved serine 275 perturbs the apical membrane localization and the function of the EGL-26 protein. Additional mutagenesis of this residue suggests that EGL-26 attains its membrane localization via a mechanism distinct from that of LRAT.
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Affiliation(s)
- Kathleen A Estes
- Department of Biochemistry and Molecular Biology, 104D Life Science Building, The Pennsylvania State University, University Park, PA 16802, USA
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Bumbarger DJ, Crum J, Ellisman MH, Baldwin JG. Three-dimensional reconstruction of the nose epidermal cells in the microbial feeding nematode, Acrobeles complexus (Nematoda: Rhabditida). J Morphol 2007; 267:1257-72. [PMID: 16710857 DOI: 10.1002/jmor.10456] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
The epidermis of the anterior end (nose) plays an important role in the evolution, development, and functional feeding morphology in nematodes, but information on this complex organ system is limited. Here, we produce a 3D model of 13 of the cells making up this organ system reconstructed from serial transmission electron micrographs of the microbial feeding nematode, Acrobeles complexus. Nose epidermal cells were found to be broadly similar to those of the distantly related model organism Caenorhabditis elegans in the number and arrangement of nuclei in these largely syncytial cells; this similarity demonstrates striking evolutionary conservation that allows for robust statements of homology between the taxa. Examining details of cell shape, however, revealed surprisingly complex subcellular specialization, which differed markedly from C. elegans in the number and arrangement of cell processes. Anterior toroid processes of the anterior arcade, posterior arcade, and HypB syncytia form a nested complex at the base of the labial probolae. Anterior toroid processes of HypC and the inner labial socket cells are associated with the base of the cephalic probolae and radial ridge processes. Extracellular filaments (tendon organs) and radiating cytoskeletal filaments of the posterior arcade syncytium form a connection between the body wall muscle cells and the pharynx. An epidermal cell with no known homolog in other nematodes is identified. Findings provide a basis to propose hypotheses related to the development and evolutionary origin of specialized feeding appendages (probolae) in the Cephalobinae (including Acrobeles), and hypotheses of homology are revised for epidermal cells in the nose of the closely related and primarily plant parasitic group, Tylenchida.
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Affiliation(s)
- Daniel J Bumbarger
- Department of Nematology, University of California, Riverside, California 92521, USA.
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Kiefer JC, Smith PA, Mango SE. PHA-4/FoxA cooperates with TAM-1/TRIM to regulate cell fate restriction in the C. elegans foregut. Dev Biol 2006; 303:611-24. [PMID: 17250823 PMCID: PMC1855296 DOI: 10.1016/j.ydbio.2006.11.042] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2006] [Revised: 11/16/2006] [Accepted: 11/28/2006] [Indexed: 10/23/2022]
Abstract
A key question in development is how pluripotent progenitors are progressively restricted to acquire specific cell fates. Here we investigate how embryonic blastomeres in C. elegans develop into foregut (pharynx) cells in response to the selector gene PHA-4/FoxA. When pha-4 is removed from pharyngeal precursors, they exhibit two alternative responses. Before late-gastrulation (8E stage), these cells lose their pharyngeal identity and acquire an alternative fate such as ectoderm (Specification stage). After the Specification stage, mutant cells develop into aberrant pharyngeal cells (Morphogenesis/Differentiation stage). Two lines of evidence suggest that the Specification stage depends on transcriptional repression of ectodermal genes by pha-4. First, pha-4 exhibits strong synthetic phenotypes with the B class synMuv gene tam-1 (Tandam Array expression Modifier 1) and with a mediator of transcriptional repression, the NuRD complex (NUcleosome Remodeling and histone Deacetylase). Second, pha-4 associates with the promoter of the ectodermal regulator lin-26 and is required to repress lin-26 expression. We propose that restriction of early blastomeres to the pharyngeal fate depends on both repression of ectodermal genes and activation of pharyngeal genes by PHA-4.
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Affiliation(s)
| | | | - Susan E. Mango
- *To whom correspondence should be sent: , phone 801-581-7633, FAX 801-585- 1980
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Jenkins N, Saam JR, Mango SE. CYK-4/GAP provides a localized cue to initiate anteroposterior polarity upon fertilization. Science 2006; 313:1298-301. [PMID: 16873611 DOI: 10.1126/science.1130291] [Citation(s) in RCA: 105] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
The Caenorhabditis elegans anteroposterior axis is established in response to fertilization by sperm. Here we present evidence that RhoA, the guanine nucleotide-exchange factor ECT-2, and the Rho guanosine triphosphatase-activating protein CYK-4 modulate myosin light-chain activity to create a gradient of actomyosin, which establishes the anterior domain. CYK-4 is enriched within sperm, and paternally donated CYK-4 is required for polarity. These data suggest that CYK-4 provides a molecular link between fertilization and polarity establishment in the one-cell embryo. Orthologs of CYK-4 are expressed in sperm of other species, which suggests that this cue may be evolutionarily conserved.
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Affiliation(s)
- Noah Jenkins
- Department of Oncological Sciences, Huntsman Cancer Institute, University of Utah, Salt Lake City, UT 84112, USA
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50
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Franks DM, Izumikawa T, Kitagawa H, Sugahara K, Okkema PG. C. elegans pharyngeal morphogenesis requires both de novo synthesis of pyrimidines and synthesis of heparan sulfate proteoglycans. Dev Biol 2006; 296:409-20. [PMID: 16828468 DOI: 10.1016/j.ydbio.2006.06.008] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2006] [Revised: 05/18/2006] [Accepted: 06/02/2006] [Indexed: 11/21/2022]
Abstract
The C. elegans pharynx undergoes elongation and morphogenesis to its characteristic bi-lobed shape between the 2- and 3-fold stages of embryogenesis. During this period, the pharyngeal muscles and marginal cells forming the isthmus between the anterior and posterior pharyngeal bulbs elongate and narrow. We have identified the spontaneous mutant pyr-1(cu8) exhibiting defective pharyngeal isthmus elongation, cytoskeletal organization defects, and maternal effect lethality. pyr-1 encodes CAD, a trifunctional enzyme required for de novo pyrimidine synthesis, and pyr-1(cu8) mutants are rescued by supplying exogenous pyrimidines. Similar pharyngeal defects and maternal effect lethality were found in sqv-1, sqv-8, rib-1 and rib-2 mutants, which affect enzymes involved in heparan sulfate proteoglycan (HSPG) synthesis. rib-1 mutant lethality was enhanced in a pyr-1 mutant background, indicating that HSPG synthesis is very sensitive to decreased pyrimidine pools, and HS disaccharides are moderately decreased in both rib-1 and pyr-1 mutants. We hypothesize that HSPGs are necessary for pharyngeal isthmus elongation, and pyr-1 functions upstream of proteoglycan synthesizing enzymes by providing precursors of UDP-sugars essential for HSPG synthesis.
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Affiliation(s)
- Dawn M Franks
- Department of Biological Sciences and the Laboratory for Molecular Biology, University of Illinois at Chicago, 900 S. Ashland Avenue, Chicago, IL 60607, USA
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