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Tolkin T, Mohammad A, Starich TA, Nguyen KCQ, Hall DH, Schedl T, Hubbard EJA, Greenstein D. Innexin function dictates the spatial relationship between distal somatic cells in the Caenorhabditis elegans gonad without impacting the germline stem cell pool. eLife 2022; 11:e74955. [PMID: 36098634 PMCID: PMC9473689 DOI: 10.7554/elife.74955] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2021] [Accepted: 08/08/2022] [Indexed: 12/01/2022] Open
Abstract
Gap-junctional signaling mediates myriad cellular interactions in metazoans. Yet, how gap junctions control the positioning of cells in organs is not well understood. Innexins compose gap junctions in invertebrates and affect organ architecture. Here, we investigate the roles of gap-junctions in controlling distal somatic gonad architecture and its relationship to underlying germline stem cells in Caenorhabditis elegans. We show that a reduction of soma-germline gap-junctional activity causes displacement of distal sheath cells (Sh1) towards the distal end of the gonad. We confirm, by live imaging, transmission electron microscopy, and antibody staining, that bare regions-lacking somatic gonadal cell coverage of germ cells-are present between the distal tip cell (DTC) and Sh1, and we show that an innexin fusion protein used in a prior study encodes an antimorphic gap junction subunit that mispositions Sh1. We determine that, contrary to the model put forth in the prior study based on this fusion protein, Sh1 mispositioning does not markedly alter the position of the borders of the stem cell pool nor of the progenitor cell pool. Together, these results demonstrate that gap junctions can control the position of Sh1, but that Sh1 position is neither relevant for GLP-1/Notch signaling nor for the exit of germ cells from the stem cell pool.
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Affiliation(s)
- Theadora Tolkin
- Kimmel Center for Biology and Medicine at the Skirball Institute, NYU Grossman School of MedicineNew YorkUnited States
- Department of Cell Biology, NYU Grossman School of MedicineNew YorkUnited States
| | - Ariz Mohammad
- Department of Genetics, Washington University School of MedicineSt. LouisUnited States
| | - Todd A Starich
- Department of Genetics, Cell Biology and Development, University of MinnesotaMinneapolisUnited States
| | - Ken CQ Nguyen
- Department of Neuroscience, Albert Einstein College of MedicineThe BronxUnited States
| | - David H Hall
- Department of Neuroscience, Albert Einstein College of MedicineThe BronxUnited States
| | - Tim Schedl
- Department of Genetics, Washington University School of MedicineSt. LouisUnited States
| | - E Jane Albert Hubbard
- Kimmel Center for Biology and Medicine at the Skirball Institute, NYU Grossman School of MedicineNew YorkUnited States
- Department of Cell Biology, NYU Grossman School of MedicineNew YorkUnited States
- Department of Pathology, NYU Grossman School of MedicineNew YorkUnited States
| | - David Greenstein
- Department of Genetics, Cell Biology and Development, University of MinnesotaMinneapolisUnited States
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2
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Flibotte S, Kim BR, Van de Laar E, Brown L, Moghal N. The SWI/SNF chromatin remodeling complex exerts both negative and positive control over LET-23/EGFR-dependent vulval induction in Caenorhabditis elegans. Dev Biol 2016; 415:46-63. [PMID: 27207389 DOI: 10.1016/j.ydbio.2016.05.009] [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: 10/14/2015] [Revised: 05/05/2016] [Accepted: 05/09/2016] [Indexed: 11/19/2022]
Abstract
Signaling by the epidermal growth factor receptor (EGFR) generates diverse developmental patterns. This requires precise control over the location and intensity of signaling. Elucidation of these regulatory mechanisms is important for understanding development and disease pathogenesis. In Caenorhabditis elegans, LIN-3/EGF induces vulval formation in the mid-body, which requires LET-23/EGFR activation only in P6.p, the vulval progenitor nearest the LIN-3 source. To identify mechanisms regulating this signaling pattern, we screened for mutations that cooperate with a let-23 gain-of-function allele to cause ectopic vulval induction. Here, we describe a dominant gain-of-function mutation in swsn-4, a component of SWI/SNF chromatin remodeling complexes. Loss-of-function mutations in multiple SWI/SNF components reveal that weak reduction in SWI/SNF activity causes ectopic vulval induction, while stronger reduction prevents adoption of vulval fates, a phenomenon also observed with increasing loss of LET-23 activity. High levels of LET-23 expression in P6.p are thought to locally sequester LIN-3, thereby preventing ectopic vulval induction, with slight reductions in its expression interfering with LIN-3 sequestration, but not vulval fate signaling. We find that SWI/SNF positively regulates LET-23 expression in P6.p descendants, providing an explanation for the similarities between let-23 and SWI/SNF mutant phenotypes. However, SWI/SNF regulation of LET-23 expression is cell-specific, with SWI/SNF repressing its expression in the ALA neuron. The swsn-4 gain-of-function mutation affects the PTH domain, and provides the first evidence that its auto-inhibitory function in yeast Sth1p is conserved in metazoan chromatin remodelers. Finally, our work supports broad use of SWI/SNF in regulating EGFR signaling during development, and suggests that dominant SWI/SNF mutations in certain human congenital anomaly syndromes may be gain-of-functions.
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Affiliation(s)
- Stephane Flibotte
- Department of Zoology, University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z4.
| | - Bo Ram Kim
- Princess Margaret Cancer Centre/University Health Network, Department of Medical Biophysics, University of Toronto, Toronto, Ontario, Canada M5G 1L7.
| | - Emily Van de Laar
- Princess Margaret Cancer Centre/University Health Network, Department of Medical Biophysics, University of Toronto, Toronto, Ontario, Canada M5G 1L7.
| | - Louise Brown
- Samuel Lunenfeld Research Institute of Mount Sinai Hospital, Toronto, Ontario, Canada M5G 1X5.
| | - Nadeem Moghal
- Princess Margaret Cancer Centre/University Health Network, Department of Medical Biophysics, University of Toronto, Toronto, Ontario, Canada M5G 1L7.
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3
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Modzelewska K, Elgort MG, Huang J, Jongeward G, Lauritzen A, Yoon CH, Sternberg PW, Moghal N. An activating mutation in sos-1 identifies its Dbl domain as a critical inhibitor of the epidermal growth factor receptor pathway during Caenorhabditis elegans vulval development. Mol Cell Biol 2007; 27:3695-707. [PMID: 17339331 PMCID: PMC1899997 DOI: 10.1128/mcb.01630-06] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Proper regulation of receptor tyrosine kinase (RTK)-Ras-mitogen-activated protein kinase (MAPK) signaling pathways is critical for normal development and the prevention of cancer. SOS is a dual-function guanine nucleotide exchange factor (GEF) that catalyzes exchange on Ras and Rac. Although the physiologic role of SOS and its CDC25 domain in RTK-mediated Ras activation is well established, the in vivo function of its Dbl Rac GEF domain is less clear. We have identified a novel gain-of-function missense mutation in the Dbl domain of Caenorhabditis elegans SOS-1 that promotes epidermal growth factor receptor (EGFR) signaling in vivo. Our data indicate that a major developmental function of the Dbl domain is to inhibit EGF-dependent MAPK activation. The amount of inhibition conferred by the Dbl domain is equal to that of established trans-acting inhibitors of the EGFR pathway, including c-Cbl and RasGAP, and more than that of MAPK phosphatase. In conjunction with molecular modeling, our data suggest that the C. elegans mutation, as well as an equivalent mutation in human SOS1, activates the MAPK pathway by disrupting an autoinhibitory function of the Dbl domain on Ras activation. Our work suggests that functionally similar point mutations in humans could directly contribute to disease.
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Affiliation(s)
- Katarzyna Modzelewska
- Department of Oncological Sciences, Huntsman Cancer Institute, University of Utah, 2000 Circle of Hope, Room 3242, Salt Lake City, UT 84112-5550, USA
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4
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Frank CA, Hawkins NC, Guenther C, Horvitz HR, Garriga G. C. elegans HAM-1 positions the cleavage plane and regulates apoptosis in asymmetric neuroblast divisions. Dev Biol 2005; 284:301-10. [PMID: 15979607 DOI: 10.1016/j.ydbio.2005.05.026] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2005] [Revised: 04/28/2005] [Accepted: 05/18/2005] [Indexed: 12/28/2022]
Abstract
Asymmetric cell division occurs when a mother cell divides to generate two distinct daughter cells, a process that promotes the generation of cellular diversity in metazoans. During Caenorhabditis elegans development, the asymmetric divisions of neural progenitors generate neurons, neural support cells and apoptotic cells. C. elegans HAM-1 is an asymmetrically distributed cortical protein that regulates several of these asymmetric neuroblast divisions. Here, we show that HAM-1 is a novel protein and define residues important for HAM-1 function and distribution to the cell cortex. Our phenotypic analysis of ham-1 mutant embryos suggests that HAM-1 controls only neuroblast divisions that produce apoptotic cells. Moreover, ham-1 mutant embryos contain many unusually large cell-death corpses. An investigation of this corpse phenotype revealed that it results from a reversal of neuroblast polarity. A misplacement of the neuroblast cleavage plane generates daughter cells of abnormal size, with the apoptotic daughters larger than normal. Thus, HAM-1 regulates the position of the cleavage plane, apoptosis and mitotic potential in C. elegans asymmetric cell divisions.
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Affiliation(s)
- C Andrew Frank
- Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720-3204, USA
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5
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Grisoni K, Gieseler K, Mariol MC, Martin E, Carre-Pierrat M, Moulder G, Barstead R, Ségalat L. The stn-1 syntrophin gene of C.elegans is functionally related to dystrophin and dystrobrevin. J Mol Biol 2003; 332:1037-46. [PMID: 14499607 DOI: 10.1016/j.jmb.2003.08.021] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Syntrophins are a family of PDZ domain-containing adaptor proteins required for receptor localization. Syntrophins are also associated with the dystrophin complex in muscles. We report here the molecular and functional characterization of the Caenorhabditis elegans gene stn-1 (F30A10.8), which encodes a syntrophin with homology to vertebrate alpha and beta-syntrophins. stn-1 is expressed in neurons and in muscles of C.elegans. stn-1 mutants resemble dystrophin (dys-1) and dystrobrevin (dyb-1) mutants: they are hyperactive, bend their heads when they move forward, tend to hypercontract, and are hypersensitive to the acetylcholinesterase inhibitor aldicarb. These phenotypes are suppressed when stn-1 is expressed under the control of a muscular promoter, indicating that they are caused by the absence of stn-1 in muscles. These results suggest that the role of syntrophin is linked to dystrophin function in C.elegans.
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Affiliation(s)
- Karine Grisoni
- CGMC, CNRS-UMR 5534, Université Lyon-1, 43 Bid du 11 Novembre, 69622, Villeurbanne, cedex, France.
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6
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Bastiani CA, Gharib S, Simon MI, Sternberg PW. Caenorhabditis elegans Gαq Regulates Egg-Laying Behavior via a PLCβ-Independent and Serotonin-Dependent Signaling Pathway and Likely Functions Both in the Nervous System and in Muscle. Genetics 2003; 165:1805-22. [PMID: 14704167 PMCID: PMC1462877 DOI: 10.1093/genetics/165.4.1805] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Abstract
egl-30 encodes the single C. elegans ortholog of vertebrate Gαq family members. We analyzed the expression pattern of EGL-30 and found that it is broadly expressed, with highest expression in the nervous system and in pharyngeal muscle. We isolated dominant, gain-of-function alleles of egl-30 as intragenic revertants of an egl-30 reduction-of-function mutation. Using these gain-of-function mutants and existing reduction-of-function mutants, we examined the site and mode of action of EGL-30. On the basis of pharmacological analysis, it has been determined that egl-30 functions both in the nervous system and in the vulval muscles for egg-laying behavior. Genetic epistasis over mutations that eliminate detectable levels of serotonin reveals that egl-30 requires serotonin to regulate egg laying. Furthermore, pharmacological response assays strongly suggest that EGL-30 may directly couple to a serotonin receptor to mediate egg laying. We also examined genetic interactions with mutations in the gene that encodes the single C. elegans homolog of PLCβ and mutations in genes that encode signaling molecules downstream of PLCβ. We conclude that PLCβ functions in parallel with egl-30 with respect to egg laying or is not the major effector of EGL-30. In contrast, PLCβ-mediated signaling is likely downstream of EGL-30 with respect to pharyngeal-pumping behavior. Our data indicate that there are multiple signaling pathways downstream of EGL-30 and that different pathways could predominate with respect to the regulation of different behaviors.
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Affiliation(s)
- Carol A Bastiani
- Howard Hughes Medical Institute, California Institute of Technology, Pasadena, California 91125, USA
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7
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Jin SW, Kimble J, Ellis RE. Regulation of cell fate in Caenorhabditis elegans by a novel cytoplasmic polyadenylation element binding protein. Dev Biol 2001; 229:537-53. [PMID: 11150246 DOI: 10.1006/dbio.2000.9993] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
The fog-1 gene of Caenorhabditis elegans specifies that germ cells differentiate as sperm rather than as oocytes. We cloned fog-1 through a combination of transformation rescue experiments, RNA-mediated inactivation, and mutant analyses. Our results show that fog-1 produces two transcripts, both of which are found in germ cells but not in the soma. Furthermore, two deletion mutants alter these transcripts and are likely to eliminate fog-1 activity. The larger transcript is expressed under the control of sex-determination genes, is necessary for fog-1 activity, and is sufficient to rescue a fog-1 mutant. This transcript encodes a novel member of the CPEB family of RNA-binding proteins. Because CPEB proteins in Xenopus and Drosophila regulate gene expression at the level of translation, we propose that FOG-1 controls germ cell fates by regulating the translation of specific messenger RNAs.
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Affiliation(s)
- S W Jin
- Department of Biology, University of Michigan, Ann Arbor, Michigan, 48109
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8
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Nance J, Davis EB, Ward S. spe-29 encodes a small predicted membrane protein required for the initiation of sperm activation in Caenorhabditis elegans. Genetics 2000; 156:1623-33. [PMID: 11102362 PMCID: PMC1461390 DOI: 10.1093/genetics/156.4.1623] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Caenorhabditis elegans spermatids complete a dramatic morphogenesis to crawling spermatozoa in the absence of an actin- or tubulin-based cytoskeleton and without synthesizing new gene products. Mutations in three genes (spe-8, spe-12, and spe-27) prevent the initiation of this morphogenesis, termed activation. Males with mutations in any of these genes are fertile. By contrast, mutant hermaphrodites are self-sterile when unmated due to a failure in spermatid activation. Intriguingly, mutant hermaphrodites form functional spermatozoa and become self-fertile upon mating, suggesting that spermatids can be activated by male seminal fluid. Here we describe a mutation in a fourth gene, spe-29, which mimics the phenotype of spe-8, spe-12, and spe-27 mutants. spe-29 sperm are defective in the initiation of hermaphrodite sperm activation, yet they maintain the ability to complete the morphogenetic rearrangements that follow. Mutant alleles of spe-12, spe-27, and spe-29 exhibit genetic interactions that suggest that the wild-type products of these genes function in a common signaling pathway to initiate sperm activation. We have identified the spe-29 gene, which is expressed specifically in the sperm-producing germ line and is predicted to encode a small, novel transmembrane protein.
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Affiliation(s)
- J Nance
- Department of Molecular and Cellular Biology, University of Arizona, Tucson, Arizona 85721, USA
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9
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Petalcorin MI, Oka T, Koga M, Ogura K, Wada Y, Ohshima Y, Futai M. Disruption of clh-1, a chloride channel gene, results in a wider body of Caenorhabditis elegans. J Mol Biol 1999; 294:347-55. [PMID: 10610763 DOI: 10.1006/jmbi.1999.3241] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We cloned the clh-1 gene coding for a putative ClC chloride channel in Caenorhabditis elegans. The gene product exhibited a high degree of homology with human ClC-1 and ClC-2. The clh-1 gene was predominantly expressed in the hypodermis, including seam cells. Null mutations of clh-1 caused a significantly wider body and an abnormal alae structure. High osmolarity in the culture medium restored the normal body width of the clh-1 mutants. These results suggest that the clh-1 gene contributes to maintenance of the body width through regulation of osmolarity.
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Affiliation(s)
- M I Petalcorin
- Division of Biological Sciences Institute of Scientific and Industrial Research, Osaka University, CREST of the Japan Science and Technology Corporation, Osaka, 567-0047, Japan
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10
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Nance J, Minniti AN, Sadler C, Ward S. spe-12 encodes a sperm cell surface protein that promotes spermiogenesis in Caenorhabditis elegans. Genetics 1999; 152:209-20. [PMID: 10224255 PMCID: PMC1460590 DOI: 10.1093/genetics/152.1.209] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
During spermiogenesis, Caenorhabditis elegans spermatids activate and mature into crawling spermatozoa without synthesizing new proteins. Mutations in the spe-12 gene block spermatid activation, rendering normally self-fertile hermaphrodites sterile. Mutant males, however, are fertile. Surprisingly, when mutant hermaphrodites mate with a male, their self-spermatids activate and form functional spermatozoa, presumably due to contact with male seminal fluid. Here we show that, in addition to its essential role in normal activation of hermaphrodite-derived spermatids, SPE-12 also plays a supplementary but nonessential role in mating-induced activation. We have identified the spe-12 gene, which encodes a novel protein containing a single transmembrane domain. spe-12 mRNA is expressed in the sperm-producing germ line and the protein localizes to the spermatid cell surface. We propose that SPE-12 functions downstream of both hermaphrodite- and male-derived activation signals in a spermatid signaling pathway that initiates spermiogenesis.
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Affiliation(s)
- J Nance
- Department of Molecular and Cellular Biology, University of Arizona, Tucson, Arizona 85721, USA
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11
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Forrester WC, Perens E, Zallen JA, Garriga G. Identification of Caenorhabditis elegans genes required for neuronal differentiation and migration. Genetics 1998; 148:151-65. [PMID: 9475729 PMCID: PMC1459802 DOI: 10.1093/genetics/148.1.151] [Citation(s) in RCA: 79] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
To understand the mechanisms that guide migrating cells, we have been studying the embryonic migrations of the C. elegans canal-associated neurons (CANs). Here, we describe two screens used to identify genes involved in CAN migration. First, we screened for mutants that died as clear larvae (Clr) or had withered tails (Wit), phenotypes displayed by animals lacking normal CAN function. Second, we screened directly for mutants with missing or misplaced CANs. We isolated and characterized 30 mutants that defined 14 genes necessary for CAN migration. We found that one of the genes, ceh-10, specifies CAN fate. ceh-10 had been defined molecularly as encoding a homeodomain protein expressed in the CANs. Mutations that reduce ceh-10 function result in Wit animals with CANs that are partially defective in their migrations. Mutations that eliminate ceh-10 function result in Clr animals with CANs that fail to migrate or express CEH-23, a CAN differentiation marker. Null mutants also fail to express CEH-10, suggesting that CEH-10 regulates its own expression. Finally, we found that ceh-10 is necessary for the differentiation of AIY and RMED, two additional cells that express CEH-10.
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Affiliation(s)
- W C Forrester
- Department of Molecular and Cell Biology, University of California, Berkeley 94720-3204, USA.
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12
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Abstract
The migrations of cells and growth cones contribute to form and pattern during metazoan development. To study the mechanisms that regulate cell motility, we have screened for C. elegans mutants defective in the posteriorly directed migrations of the canal-associated neurons (CANs). Here we describe 14 genes necessary for CAN cell migration. Our characterization of the mutants has led to three conclusions. First, the mutations define three gene classes: genes necessary for cell fate specification, genes necessary for multiple cell migrations and a single gene necessary for final positioning of migrating cells. Second, cell interactions between the CAN and HSN, a neuron that migrates anteriorly to a position adjacent to the CAN, control the final destination of the HSN cell body. Third, C. elegans larval development requires the CANs. In the absence of CAN function, larvae arrest development, with excess fluid accumulating in their pseudocoeloms. This phenotype may reflect a role of the CANs in osmoregulation.
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Affiliation(s)
- W C Forrester
- Department of Molecular and Cell Biology, University of California, Berkeley 94720, USA.
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13
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Guenther C, Garriga G. Asymmetric distribution of the C. elegans HAM-1 protein in neuroblasts enables daughter cells to adopt distinct fates. Development 1996; 122:3509-18. [PMID: 8951066 DOI: 10.1242/dev.122.11.3509] [Citation(s) in RCA: 47] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
One mechanism of generating cellular diversity is to distribute developmental potential asymmetrically to daughter cells at mitosis. Two observations described in this report suggest that the C. elegans HAM-1 protein functions in dividing neuroblasts to produce daughter cells that adopt distinct fates. First, HAM-1 is asymmetrically distributed to the periphery of certain mitotic cells, ensuring that it will be inherited by only one daughter cell. Second, ham-1 mutations disrupt the asymmetric divisions of five neuroblasts. In one of these divisions, loss of ham-1 function causes the daughter cell that does not inherit HAM-1 to adopt the fate of the daughter cell that normally inherits HAM-1. We propose that asymmetric distribution of HAM-1 enables daughter cells to adopt distinct fates.
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Affiliation(s)
- C Guenther
- Department of Molecular and Cell Biology, University of California, Berkeley 94720-3204, USA
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14
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Sundaram M, Han M. The C. elegans ksr-1 gene encodes a novel Raf-related kinase involved in Ras-mediated signal transduction. Cell 1995; 83:889-901. [PMID: 8521513 DOI: 10.1016/0092-8674(95)90205-8] [Citation(s) in RCA: 235] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Vulval induction in C. elegans is controlled by a highly conserved signaling pathway similar to the RTK-Ras-MAPK cascade in mammals. By screening for suppressors of the Multivulva phenotype caused by an activated let-60 ras allele, we isolated mutations in a gene, ksr-1, that acts as a positive modifier of vulval induction and is required for at least two other let-60 ras-mediated processes. Although ksr-1 mutations do not perturb vulval induction in an otherwise wild-type background, they have very strong effects on vulval induction in genetic backgrounds where Ras pathway activity is constitutively activated or compromised, suggesting that ksr-1 activity is required for maximal stimulation of vulval fates by the Ras pathway. Genetic epistasis analysis suggests that ksr-1 acts downstream of or in parallel to let-60 ras. We cloned ksr-1 and have shown that it encodes a novel putative protein kinase related to the Raf family of Ser/Thr kinases.
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Affiliation(s)
- M Sundaram
- Department of Molecular, University of Colorado, Boulder 80309-0347, USA
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15
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Fukushige T, Siddiqui SS. Effect of the dpy-20 and rol-6 cotransformation markers on alpha-tubulin gene expression in C. elegans transformants. Transgenic Res 1995; 4:332-40. [PMID: 8589736 DOI: 10.1007/bf01972530] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
An alpha-1 tubulin::lacZ fusion gene was introduced into the germline of Caenorhabditis elegans, using either rol-6 or dpy-20 genomic DNA as a cotransformation marker. Distinct patterns in cellular specificity of the alpha-1 tubulin::lacZ fusion gene expression were observed, depending on the cotransformation marker used. For the rol-6 marker, the tubulin fusion gene was expressed in several neurons in the head and tail ganglia and a set of 38-39 ventral cord motor neurons along the body length of the animal during larval and adult development. In contrast, for the dpy-20 marker system, not only were fewer neurons stained in the head and tail region, but also the staining of ventral cord motor neurons was extremely reduced both in number and intensity. The dpy-20 marked-mediated suppression of the alpha-1 tubulin gene expression was observed both in the cis and trans configurations. Similar down-regulation in the ventral cord motor neurons was observed when the alpha-2 tubulin::lacZ fusion gene construct was tested in these experiments using the dpy-20 marker. In controls, where the tubulin fusion gene was directly injected to obtain transformants without any marker DNA, the cellular staining pattern was close to the fusion gene expression observed with the rol-6 marker DNA. These results underline the importance of the choice of transformation marker system in generation of the transgenic animals, and reveal a down-regulation of the alpha-tubulin fusion gene expression in the ventral cord motor neurons in transgenic animals when the dpy-20 gene was used as a cotransformation marker.
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Affiliation(s)
- T Fukushige
- Department of Ecological Engineering, Toyohashi University of Technology, Japan
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16
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Clark DV, Suleman DS, Beckenbach KA, Gilchrist EJ, Baillie DL. Molecular cloning and characterization of the dpy-20 gene of Caenorhabditis elegans. MOLECULAR & GENERAL GENETICS : MGG 1995; 247:367-78. [PMID: 7770042 DOI: 10.1007/bf00293205] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
We describe the molecular analysis of the dpy-20 gene in Caenorhabditis elegans. Isolation of genomic sequences was facilitated by the availability of a mutation that resulted from insertion of a Tc1 transposable element into the dpy-20 gene. The Tc1 insertion site in the m474::Tc1 allele was identified and was found to lie within the coding region of dpy-20. Three revertants (two wild-type and one partial revertant) resulted from the excision of this Tc1 element. Genomic dpy-20 clones' were isolated from a library of wild-type DNA and were found to lie just to the left of the unc-22 locus on the physical map, compatible with the position of dpy-20 on the genetic map. Cosmid DNA containing the dpy-20 gene was successfully used to rescue the mutant phenotype of animals homozygous for another dpy-20 allele, e1282ts. Sequence analysis of the putative dpy-20 homologue in Caenorhabditis briggsae was performed to confirm identification of the coding regions of the C. elegans gene and to identify conserved regulatory regions. Sequence analysis of dpy-20 revealed that it was not similar to other genes encoding known cuticle components such as collagen or cuticulin. The dpy-20 gene product, therefore, identifies a previously unknown type of protein that may be directly or indirectly involved in cuticle function. Northern blot analysis showed that dpy-20 is expressed predominantly in the second larval stage and that the mRNA is not at all abundant. Data from temperature shift studies using the temperature-sensitive allele e1282ts showed that the sensitive period also occurs at approximately the second larval stage. Therefore, expression of dpy-20 mRNA and function of the DPY-20 protein are closely linked temporally.
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Affiliation(s)
- D V Clark
- Department of Biological Sciences, Simon Fraser University, Burnaby, B.C., Canada
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