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Krause M, Liu J. Somatic muscle specification during embryonic and post-embryonic development in the nematode C. elegans. WILEY INTERDISCIPLINARY REVIEWS-DEVELOPMENTAL BIOLOGY 2011; 1:203-14. [PMID: 23801436 DOI: 10.1002/wdev.15] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Myogenesis has proved to be a powerful paradigm for understanding cell fate specification and differentiation in many model organisms. Studies of somatic bodywall muscle (BWM) development in Caenorhabditis elegans allow us to define, with single cell resolution, the distinct hierarchies of transcriptional regulators needed for myogenesis throughout development. Although all 95 BWM cells appear uniform after differentiation, there are several different regulatory cascades employed embryonically and post-embryonically. These, in turn, are integrated into multiple extrinsic cell signaling events. The convergence of these different pathways on the key nodal point, that is the activation of the core muscle module, commits individual cells to myogenesis. Comparisons of myogenesis between C. elegans and other model systems provide insights into the evolution of contractile cell types, demonstrating the conservation of regulatory schemes for muscles throughout the animal kingdom.
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Affiliation(s)
- Michael Krause
- Laboratory of Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, Bethesda, MD, USA.
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Mainpal R, Priti A, Subramaniam K. PUF-8 suppresses the somatic transcription factor PAL-1 expression in C. elegans germline stem cells. Dev Biol 2011; 360:195-207. [PMID: 21968099 PMCID: PMC3736097 DOI: 10.1016/j.ydbio.2011.09.021] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2011] [Revised: 08/30/2011] [Accepted: 09/18/2011] [Indexed: 10/17/2022]
Abstract
RNA-binding proteins of the PUF family are well conserved post-transcriptional regulators that control a variety of developmental processes. The C. elegans protein PUF-8 is essential for several aspects of germ cell development including the maintenance of germline stem cells (GSCs). To explore the molecular mechanisms underlying its function, we have identified 160 germline-expressed mRNAs as potential targets of PUF-8. We generated GFP::H2B-3' UTR fusions for 17 mRNAs to assay their post-transcriptional regulation in germ cells. Twelve transgenes were not expressed in the mitotic germ cells, and depletion of PUF-8 led to misexpression of six of them in these cells. In contrast, the expression of 3' UTR fusion of hip-1, which encodes the HSP-70 interacting protein, was dependent on PUF-8. These results indicate that PUF-8 may regulate the expression of its targets both negatively as well as positively. We investigated the PUF-8-mediated post-transcriptional control of one mRNA, namely pal-1, which encodes a homeodomain transcription factor responsible for muscle development. Our results show that PUF-8 binds in vitro to specific sequences within pal-1 3' UTR that are critical for post-transcriptional suppression in GSCs. Removal of PUF-8 resulted in PAL-1 misexpression, and PAL-1-dependent misexpression of the myogenic promoter HLH-1 in germ cells. We propose that PUF-8 protects GSCs from the influence of somatic differentiation factors such as PAL-1, which are produced in the maternal germline but meant for embryogenesis.
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Affiliation(s)
- Rana Mainpal
- Department of Biological Sciences & Bioengineering, Indian Institute of Technology, Kanpur 208016, India
| | - Agarwal Priti
- Department of Biological Sciences & Bioengineering, Indian Institute of Technology, Kanpur 208016, India
| | - Kuppuswamy Subramaniam
- Department of Biological Sciences & Bioengineering, Indian Institute of Technology, Kanpur 208016, India
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53
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Zuryn S, Daniele T, Jarriault S. Direct cellular reprogramming in Caenorhabditis elegans: facts, models, and promises for regenerative medicine. WILEY INTERDISCIPLINARY REVIEWS-DEVELOPMENTAL BIOLOGY 2011; 1:138-52. [PMID: 23801672 DOI: 10.1002/wdev.7] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
In vitro systems of cellular reprogramming [induced pluripotent stem (iPS) cells and direct reprogramming or transdifferentiation] are rapidly improving our repertoire of molecular techniques that can force cells in culture to change into a desired identity. However, the new frontier for regenerative medicine is in vivo cellular reprogramming, which in light of concerns about the safety of in vitro cell manipulations, is an increasingly attractive approach for regenerative medicine. Powerful in vivo approaches are currently being undertaken in the genetic model Caenorhabditis elegans. Several very distinct cell types have been induced to change or have been discovered to transform naturally, into altogether different cell types. These examples have improved our understanding of the fundamental molecular and cellular mechanisms that permit cell identity changes in live animals. In addition, the combination of a stereotyped lineage with single cell analyses allows dissection of the early and intermediate mechanisms of reprogramming, as well as their kinetics. As a result, several important concepts on in vivo cellular reprogramming have been recently developed.
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Affiliation(s)
- Steven Zuryn
- Institut de Génétique et de Biologie Moléculaire et Cellulaire, CNRS UMR7104, INSERM U964, Université de Strasbourg, Illkirch Cu Strasbourg, France
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Hajduskova M, Ahier A, Daniele T, Jarriault S. Cell plasticity in Caenorhabditis elegans: from induced to natural cell reprogramming. Genesis 2011; 50:1-17. [PMID: 21932439 DOI: 10.1002/dvg.20806] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2011] [Revised: 08/29/2011] [Accepted: 08/30/2011] [Indexed: 01/17/2023]
Abstract
Achieving controlled reprogramming of differentiated cells into a desired cell type would open new opportunities in stem-cell biology and regenerative medicine. Experimentation on cell reprogramming requires a model in which cell conversion can be induced and tracked individually. The tiny nematode, Caenorhabditis elegans, owing to its known cellular lineage, allows the study of direct cell type conversion with a single-cell resolution. Indeed, recent advances have shown that despite its invariant cell lineage, cellular identities can be reprogrammed, leading to cell conversion in vivo. In addition, natural transdifferentiation events occur in the worm, providing a powerful model for the study of cellular plasticity in a physiological cellular microenvironment. Here, we review pioneer studies on induced and naturally occurring reprogramming events in C. elegans and the new notions that have emerged.
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Affiliation(s)
- Martina Hajduskova
- Development and Stem Cells Programme, Institut de Génétique et de Biologie Moléculaire et Cellulaire, CNRS UMR 7104, INSERM U964, Université de Strasbourg, 67404 Illkirch CU Strasbourg, France
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55
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Myogenic conversion and transcriptional profiling of embryonic blastomeres in Caenorhabditis elegans. Methods 2011; 56:50-4. [PMID: 22019720 DOI: 10.1016/j.ymeth.2011.10.001] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2011] [Revised: 10/03/2011] [Accepted: 10/04/2011] [Indexed: 11/22/2022] Open
Abstract
Myogenesis has proven to be a powerful paradigm for understanding cell fate specification and differentiation in many model organisms. This includes the nematode Caenorhabditis elegans for which the genetic, cellular, and molecular tools have allowed an in-depth understanding of muscle development. One tool not yet available in C. elegans is a robust, pure and prolific cell culture system to study myogenesis. As an alternative, this chapter describes a method by which the cell fates of early, uncommitted blastomeres in the embryo are converted to a myogenic lineage. This technique permits the nearly synchronous induction of myogenesis in vivo with the potential to generate a nearly homogeneous population of cells. Coupled with the RNA isolation and cDNA amplification methods that are also described, one can now profile gene expression throughout myogenesis using any platform of choice (e.g. expression arrays, next generation sequencing). Although limited by the artificial nature of this developing mass of muscle inside the eggshell, blastomere conversion and transcriptional profiling is a very powerful tool to investigate changes in gene expression associated with myogenesis in C. elegans that is applicable to many different cell types. When coupled with next generation sequencing, the method has the potential to yield a very high-resolution map of changes in gene expression throughout myogenesis.
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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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Savory JGA, Mansfield M, St Louis C, Lohnes D. Cdx4 is a Cdx2 target gene. Mech Dev 2010; 128:41-8. [PMID: 20933081 DOI: 10.1016/j.mod.2010.09.004] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2010] [Revised: 08/31/2010] [Accepted: 09/29/2010] [Indexed: 11/29/2022]
Abstract
The products of the Cdx genes, Cdx1, Cdx2 and Cdx4, play multiple roles in early vertebrate development, and have been proposed to serve to relay signaling information from Wnt, RA and FGF pathways to orchestrate events related to anterior-posterior vertebral patterning and axial elongation. In addition, Cdx1 and Cdx2 have been reported to both autoregulate and to be subject to cross regulation by other family members. We have now found that Cdx4 expression is significantly down regulated in Cdx2(-/-) mutants suggesting previously unrecognized cross-regulatory interactions. Moreover, we have previously shown that Cdx4 is a direct target of the canonical Wnt signaling pathway, and that Cdx1 physically interacts with LEF/TCF members in an autoregulatory loop. We therefore investigated the means by which Cdx2 impacted on Cdx4 expression and assessed potential interaction between Cdx2 and canonical Wnt signaling on the Cdx4 promoter. We found that the Cdx4 promoter was regulated by Cdx2 in transient transfection assays. Electrophoretic mobility shift assays showed that Cdx2 bound to predicted Cdx response elements in the Cdx4 promoter which, when mutated, significantly reduced activity. Consistent with these data, chromatin immunoprecipitation assays from embryos demonstrated occupancy of the Cdx4 promoter by Cdx2 in vivo. However, we failed to observe an interaction between Cdx2 and components of the canonical Wnt signaling pathway. These findings suggest that, while both canonical Wnt and Cdx2 can regulate the activity of the Cdx4 promoter, they appear to operate through distinct mechanisms.
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Affiliation(s)
- Joanne G A Savory
- Department of Cellular and Molecular Medicine, University of Ottawa, 451 Smyth Road, Ottawa, Ontario, Canada K1H 8M5
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58
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A negative regulatory loop between microRNA and Hox gene controls posterior identities in Caenorhabditis elegans. PLoS Genet 2010; 6:e1001089. [PMID: 20824072 PMCID: PMC2932687 DOI: 10.1371/journal.pgen.1001089] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2009] [Accepted: 07/23/2010] [Indexed: 12/05/2022] Open
Abstract
MicroRNAs (miRNAs) have been found to regulate gene expression across eukaryotic species, but the function of most miRNA genes remains unknown. Here we describe how the analysis of the expression patterns of a well-conserved miRNA gene, mir-57, at cellular resolution for every minute during early development of Caenorhabditis elegans provided key insights in understanding its function. Remarkably, mir-57 expression shows strong positional bias but little tissue specificity, a pattern reminiscent of Hox gene function. Despite the minor defects produced by a loss of function mutation, overexpression of mir-57 causes dramatic posterior defects, which also mimic the phenotypes of mutant alleles of a posterior Hox gene, nob-1, an Abd homolog. More importantly, nob-1 expression is found in the same two posterior AB sublineages as those expressing mir-57 but with an earlier onset. Intriguingly, nob-1 functions as an activator for mir-57 expression; it is also a direct target of mir-57. In agreement with this, loss of mir-57 function partially rescues the nob-1 allele defects, indicating a negative feedback regulatory loop between the miRNA and Hox gene to provide positional cues. Given the conservation of the miRNA and Hox gene, the regulatory mechanism might be broadly used across species. The strategy used here to explore mir-57 function provides a path to dissect the regulatory relationship between genes. miRNAs are small RNAs found in many multi-cellular species that inhibit gene expression. Many of them play important roles in cancer and cell fate determination, but the function of most miRNAs is uncertain. Using live cell imaging and automated expression analysis, we found a miRNA gene, mir-57, is expressed in a position rather than tissue dependent way. Hox genes also regulate cell fate patterning along anterior-posterior (a-p) axis across different tissues. By investigating interactions between genes of these classes expressed in mir-57 expressing cells, we demonstrated by both genetic analysis and gene expression assays that a negative feedback loop between a posterior Hox gene, nob-1, and mir-57 regulates posterior cell fate determination in C. elegans. On the one hand, the Hox gene is required for normal activation of mir-57 expression, and on the other, the Hox gene functions as a direct target of and is repressed by the miRNA. Given the conservation of the two genes, a negative feedback loop between Hox and miRNA genes might be broadly used across species to regulate cell fate along the a-p axis. Detailed expression analysis may provide a general way to dissect the regulatory role of miRNAs.
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Abstract
Cell specification requires that particular subsets of cells adopt unique expression patterns that ultimately define the fates of their descendants. In C. elegans, cell fate specification involves the combinatorial action of multiple signals that produce activation of a small number of "blastomere specification" factors. These initiate expression of gene regulatory networks that drive development forward, leading to activation of "tissue specification" factors. In this review, the C. elegans embryo is considered as a model system for studies of cell specification. The techniques used to study cell fate in this species, and the themes that have emerged, are described.
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Affiliation(s)
- Morris F Maduro
- Department of Biology, University of California, Riverside, Riverside, California 92521, USA.
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60
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Landmann F, Foster JM, Slatko B, Sullivan W. Asymmetric Wolbachia segregation during early Brugia malayi embryogenesis determines its distribution in adult host tissues. PLoS Negl Trop Dis 2010; 4:e758. [PMID: 20689574 PMCID: PMC2910707 DOI: 10.1371/journal.pntd.0000758] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2010] [Accepted: 06/07/2010] [Indexed: 11/25/2022] Open
Abstract
Wolbachia are required for filarial nematode survival and
fertility and contribute to the immune responses associated with human filarial
diseases. Here we developed whole-mount immunofluorescence techniques to
characterize Wolbachia somatic and germline transmission
patterns and tissue distribution in Brugia malayi, a nematode
responsible for lymphatic filariasis. In the initial embryonic divisions,
Wolbachia segregate asymmetrically such that they occupy
only a small subset of cells in the developing embryo, facilitating their
concentration in the adult hypodermal chords and female germline.
Wolbachia are not found in male reproductive tissues and
the absence of Wolbachia from embryonic germline precursors in
half of the embryos indicates Wolbachia loss from the male
germline may occur in early embryogenesis. Wolbachia rely on
fusion of hypodermal cells to populate adult chords. Finally, we detect
Wolbachia in the secretory canal lumen suggesting living
worms may release bacteria and/or their products into their host. Filarial diseases affect over 150 million people in tropical countries. They are
caused by parasitic nematodes like Brugia malayi that rely on
their endosymbiont Wolbachia for their survival and fertility.
These bacteria are a recognized drug target in the search for treatments killing
adult worms. To understand the transmission of Wolbachia from
the embryonic to adult stages, we developed new techniques to track these
bacteria at the cellular and tissue levels. These techniques include
immunofluorescence in whole mount adult tissues and embryos. We found that
Wolbachia segregate asymetrically in specific cells, in a
lineage-specific manner during early Brugia embryogenesis, and
rely on cell fusion to subsequently populate the adult hypodermal chords. From
the chords, the Wolbachia can be secreted in the
secretory-excretory canal, suggesting that in addition to dead worms releasing
the bacteria in the human body, living worms may also secrete
Wolbachia, whose role in stimulating the immune system in
filarial pathologies is now well established.
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Affiliation(s)
- Frédéric Landmann
- Department of Molecular, Cell and Developmental Biology, University of California Santa Cruz, Santa Cruz, California, United States of America.
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61
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Hwang SY, Rose LS. Control of asymmetric cell division in early C. elegans embryogenesis: teaming-up translational repression and protein degradation. BMB Rep 2010; 43:69-78. [PMID: 20193124 DOI: 10.5483/bmbrep.2010.43.2.069] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Asymmetric cell division is a fundamental mechanism for the generation of body axes and cell diversity during early embryogenesis in many organisms. During intrinsically asymmetric divisions, an axis of polarity is established within the cell and the division plane is oriented to ensure the differential segregation of developmental determinants to the daughter cells. Studies in the nematode Caenorhabditis elegans have contributed greatly to our understanding of the regulatory mechanisms underlying cell polarity and asymmetric division. However, much remains to be elucidated about the molecular machinery controlling the spatiotemporal distribution of key components. In this review we discuss recent findings that reveal intricate interactions between translational control and targeted proteolysis. These two mechanisms of regulation serve to carefully modulate protein levels and reinforce asymmetries, or to eliminate proteins from certain cells.
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Affiliation(s)
- Sue-Yun Hwang
- Department of Molecular and Cellular Biology, University of California, Davis, CA 95616, USA
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62
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Abstract
Although now dogma, the idea that nonvertebrate organisms such as yeast, worms, and flies could inform, and in some cases even revolutionize, our understanding of oncogenesis in humans was not immediately obvious. Aided by the conservative nature of evolution and the persistence of a cohort of devoted researchers, the role of model organisms as a key tool in solving the cancer problem has, however, become widely accepted. In this review, we focus on the nematode Caenorhabditis elegans and its diverse and sometimes surprising contributions to our understanding of the tumorigenic process. Specifically, we discuss findings in the worm that address a well-defined set of processes known to be deregulated in cancer cells including cell cycle progression, growth factor signaling, terminal differentiation, apoptosis, the maintenance of genome stability, and developmental mechanisms relevant to invasion and metastasis.
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Affiliation(s)
- Natalia V. Kirienko
- University of Wyoming, College of Agriculture, Department of Molecular Biology, Dept 3944, 1000 E. University Avenue, Laramie, WY 82071
| | - Kumaran Mani
- University of Wyoming, College of Agriculture, Department of Molecular Biology, Dept 3944, 1000 E. University Avenue, Laramie, WY 82071
| | - David S. Fay
- University of Wyoming, College of Agriculture, Department of Molecular Biology, Dept 3944, 1000 E. University Avenue, Laramie, WY 82071
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63
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Yang Y, Qin W, Tian G, Jian W. Expression and functional characterization of a Rho-family small GTPase CDC42 from Trichinella spiralis. Parasitol Res 2010; 107:153-62. [PMID: 20369253 DOI: 10.1007/s00436-010-1851-9] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2010] [Accepted: 03/12/2010] [Indexed: 12/31/2022]
Abstract
A full-length cDNA encoding a Rho-family small GTPase gene cdc42 of Trichinella spiralis was expressed in E. coli. The recombinant protein of TsCDC42 was purified and used to raise the polyclonal antibodies. The expression of TsCDC42 in different stages of parasite was investigated. The western blot showed that TsCDC42 was expressed in all stages of T. spiralis, including newborn larvae, muscle larvae and adult worms. The immuno-localization revealed that TsCDC42 was ubiquitously distributed in the newborn larvae, muscle larvae and adult worm. Cross-species RNAi was done by knockdown Tscdc42 RNAi in C. elegans. The results revealed that endogenous expression level of CDC42 was decreased by knockdown Tscdc42 RNAi in C. elegans, and this knockdown reduced the progeny of C. elegans. It suggested that Tscdc42 might play the same roles in the early development of T. spiralis.
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Affiliation(s)
- Yurong Yang
- Key Laboratory of the Ministry of Education for Cell Biology and Tumor Cell Engineering, School of Life Science, Xiamen University, Xiamen, Fujian 361005, People's Republic of China.
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64
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Racher H, Hansen D. Translational control in the C. elegans hermaphrodite germ line. Genome 2010; 53:83-102. [DOI: 10.1139/g09-090] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The formation of a fully developed gamete from an undifferentiated germ cell requires progression through numerous developmental stages and cell fate decisions. The precise timing and level of gene expression guides cells through these stages. Translational regulation is highly utilized in the germ line of many species, including Caenorhabditis elegans , to regulate gene expression and ensure the proper formation of gametes. In this review, we discuss some of the developmental stages and cell fate decisions involved in the formation of functional gametes in the C. elegans germ line in which translational control has been implicated. These stages include the mitosis versus meiosis decision, the sperm/oocyte decision, and gamete maturation. We also discuss some of the techniques used to identify mRNA targets; the identification of these targets is necessary to clearly understand the role each RNA-binding protein plays in these decisions. Relatively few mRNA targets have been identified, thus providing a major focus for future research. Finally, we propose some reasons why translational control may be utilized so heavily in the germ line. Given that many species have this substantial reliance on translational regulation for the control of gene expression in the germ line, an understanding of translational regulation in the C. elegans germ line is likely to increase our understanding of gamete formation in general.
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Affiliation(s)
- Hilary Racher
- University of Calgary, 2500 University Drive, Department of Biological Sciences, Calgary, AB T2N 1N4, Canada
| | - Dave Hansen
- University of Calgary, 2500 University Drive, Department of Biological Sciences, Calgary, AB T2N 1N4, Canada
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65
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Analysis of cell fate from single-cell gene expression profiles in C. elegans. Cell 2009; 139:623-33. [PMID: 19879847 DOI: 10.1016/j.cell.2009.08.044] [Citation(s) in RCA: 114] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2008] [Revised: 05/21/2009] [Accepted: 08/18/2009] [Indexed: 11/23/2022]
Abstract
The C. elegans cell lineage provides a unique opportunity to look at how cell lineage affects patterns of gene expression. We developed an automatic cell lineage analyzer that converts high-resolution images of worms into a data table showing fluorescence expression with single-cell resolution. We generated expression profiles of 93 genes in 363 specific cells from L1 stage larvae and found that cells with identical fates can be formed by different gene regulatory pathways. Molecular signatures identified repeating cell fate modules within the cell lineage and enabled the generation of a molecular differentiation map that reveals points in the cell lineage when developmental fates of daughter cells begin to diverge. These results demonstrate insights that become possible using computational approaches to analyze quantitative expression from many genes in parallel using a digital gene expression atlas.
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RNA recognition by the embryonic cell fate determinant and germline totipotency factor MEX-3. Proc Natl Acad Sci U S A 2009; 106:20252-7. [PMID: 19915141 DOI: 10.1073/pnas.0907916106] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Totipotent stem cells have the potential to differentiate into every cell type. Renewal of totipotent stem cells in the germline and cellular differentiation during early embryogenesis rely upon posttranscriptional regulatory mechanisms. The Caenorhabditis elegans RNA binding protein, MEX-3, plays a key role in both processes. MEX-3 is a maternally-supplied factor that controls the RNA metabolism of transcripts encoding critical cell fate determinants. However, the nucleotide sequence specificity and requirements of MEX-3 mRNA recognition remain unclear. Only a few candidate regulatory targets have been identified, and the full extent of the network of MEX-3 targets is not known. Here, we define the consensus sequence required for MEX-3 RNA recognition and demonstrate that this element is required for MEX-3 dependent regulation of gene expression in live worms. Based on this work, we identify several candidate MEX-3 targets that help explain its dual role in regulating germline stem cell totipotency and embryonic cell fate specification.
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67
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Schoppmeier M, Fischer S, Schmitt-Engel C, Löhr U, Klingler M. An Ancient Anterior Patterning System Promotes Caudal Repression and Head Formation in Ecdysozoa. Curr Biol 2009; 19:1811-5. [DOI: 10.1016/j.cub.2009.09.026] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2009] [Revised: 08/31/2009] [Accepted: 09/01/2009] [Indexed: 11/26/2022]
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Translational control during early development. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2009; 90:211-54. [PMID: 20374743 DOI: 10.1016/s1877-1173(09)90006-0] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Translational control of specific messenger RNAs, which themselves are often asymmetrically localized within the cytoplasm of a cell, underlies many events in germline development, and in embryonic axis specification. This comprehensive, but by no means exhaustive, review attempts to present a picture of the present state of knowledge about mechanisms underlying mRNA localization and translational control of specific mRNAs that are mediated by trans-acting protein factors. While RNA localization and translational control are widespread in evolution and have been studied in many experimental systems, this article will focus mainly on three particularly well-characterized systems: Drosophila, Caenorhabditis elegans, and Xenopus. In keeping with the overall theme of this volume, instances in which translational control factors have been linked to human disease states will also be discussed.
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69
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Owraghi M, Broitman-Maduro G, Luu T, Roberson H, Maduro MF. Roles of the Wnt effector POP-1/TCF in the C. elegans endomesoderm specification gene network. Dev Biol 2009; 340:209-21. [PMID: 19818340 DOI: 10.1016/j.ydbio.2009.09.042] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2009] [Revised: 09/23/2009] [Accepted: 09/25/2009] [Indexed: 10/20/2022]
Abstract
In C. elegans the 4-cell stage blastomere EMS is an endomesodermal precursor. Its anterior daughter, MS, makes primarily mesodermal cells, while its posterior daughter E generates the entire intestine. The gene regulatory network underlying specification of MS and E has been the subject of study for more than 15 years. A key component of the specification of the two cells is the involvement of the Wnt/beta-catenin asymmetry pathway, which through its nuclear effector POP-1, specifies MS and E as different from each other. Loss of pop-1 function results in the mis-specification of MS as an E-like cell, because POP-1 directly represses the end-1 and end-3 genes in MS, which would otherwise promote an endoderm fate. A long-standing question has been whether POP-1 plays a role in specifying MS fate beyond repression of endoderm fate. This question has been difficult to ask because the only chromosomal lesions that remove both end-1 and end-3 are large deletions removing hundreds of genes. Here, we report the construction of bona fide end-1 end-3 double mutants. In embryos lacking activity of end-1, end-3 and pop-1 together, we find that MS fate is partially restored, while E expresses early markers of MS fate and adopts characteristics of both MS and C. Our results suggest that POP-1 is not critical for MS specification beyond repression of endoderm specification, and reveal that Wnt-modified POP-1 and END-1/3 further reinforce E specification by repressing MS fate in E. By comparison, a previous work suggested that in the related nematode C. briggsae, Cb-POP-1 is not required to repress endoderm specification in MS, in direct contrast with Ce-POP-1, but is critical for repression of MS fate in E. The findings reported here shed new light on the flexibility of combinatorial control mechanisms in endomesoderm specification in Caenorhabditis.
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Affiliation(s)
- Melissa Owraghi
- Department of Biology, University of California, 2121A Genomics Building, Riverside, Riverside, CA 92521, USA
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Broitman-Maduro G, Owraghi M, Hung WWK, Kuntz S, Sternberg PW, Maduro MF. The NK-2 class homeodomain factor CEH-51 and the T-box factor TBX-35 have overlapping function in C. elegans mesoderm development. Development 2009; 136:2735-46. [PMID: 19605496 DOI: 10.1242/dev.038307] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The C. elegans MS blastomere, born at the 7-cell stage of embryogenesis, generates primarily mesodermal cell types, including pharynx cells, body muscles and coelomocytes. A presumptive null mutation in the T-box factor gene tbx-35, a target of the MED-1 and MED-2 divergent GATA factors, was previously found to result in a profound decrease in the production of MS-derived tissues, although the tbx-35(-) embryonic arrest phenotype was variable. We report here that the NK-2 class homeobox gene ceh-51 is a direct target of TBX-35 and at least one other factor, and that CEH-51 and TBX-35 share functions. Embryos homozygous for a ceh-51 null mutation arrest as larvae with pharynx and muscle defects, although these tissues appear to be specified correctly. Loss of tbx-35 and ceh-51 together results in a synergistic phenotype resembling loss of med-1 and med-2. Overexpression of ceh-51 causes embryonic arrest and generation of ectopic body muscle and coelomocytes. Our data show that TBX-35 and CEH-51 have overlapping function in MS lineage development. As T-box regulators and NK-2 homeodomain factors are both important for heart development in Drosophila and vertebrates, our results suggest that these regulators function in a similar manner in C. elegans to specify a major precursor of mesoderm.
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71
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Henderson MA, Cronland E, Dunkelbarger S, Contreras V, Strome S, Keiper BD. A germline-specific isoform of eIF4E (IFE-1) is required for efficient translation of stored mRNAs and maturation of both oocytes and sperm. J Cell Sci 2009; 122:1529-39. [PMID: 19383718 DOI: 10.1242/jcs.046771] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Fertility and embryonic viability are measures of efficient germ cell growth and development. During oogenesis and spermatogenesis, new proteins are required for both mitotic expansion and differentiation. Qualitative and quantitative changes in protein synthesis occur by translational control of mRNAs, mediated in part by eIF4E, which binds the mRNAs 5' cap. IFE-1 is one of five eIF4E isoforms identified in C. elegans. IFE-1 is expressed primarily in the germ line and associates with P granules, large mRNPs that store mRNAs. We isolated a strain that lacks IFE-1 [ife-1(bn127)] and demonstrated that the translation of several maternal mRNAs (pos-1, pal-1, mex-1 and oma-1) was inefficient relative to that in wild-type worms. At 25 degrees C, ife-1(bn127) spermatocytes failed in cytokinesis, prematurely expressed the pro-apoptotic protein CED-4/Apaf-1, and accumulated as multinucleate cells unable to mature to spermatids. A modest defect in oocyte development was also observed. Oocytes progressed normally through mitosis and meiosis, but subsequent production of competent oocytes became limiting, even in the presence of wild-type sperm. Combined gametogenesis defects decreased worm fertility by 80% at 20 degrees C; ife-1 worms were completely sterile at 25 degrees C. Thus, IFE-1 plays independent roles in late oogenesis and spermatogenesis through selective translation of germline-specific mRNAs.
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Affiliation(s)
- Melissa A Henderson
- Department of Biochemistry, Brody School of Medicine at East Carolina University, Greenville, NC 27834, USA
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72
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Lei H, Liu J, Fukushige T, Fire A, Krause M. Caudal-like PAL-1 directly activates the bodywall muscle module regulator hlh-1 in C. elegans to initiate the embryonic muscle gene regulatory network. Development 2009; 136:1241-9. [PMID: 19261701 DOI: 10.1242/dev.030668] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
Previous work in C. elegans has shown that posterior embryonic bodywall muscle lineages are regulated through a genetically defined transcriptional cascade that includes PAL-1/Caudal-mediated activation of muscle-specific transcription factors, including HLH-1/MRF and UNC-120/SRF, which together orchestrate specification and differentiation. Using chromatin immunoprecipitation (ChIP) in embryos, we now demonstrate direct binding of PAL-1 in vivo to an hlh-1 enhancer element. Through mutational analysis of the evolutionarily conserved sequences within this enhancer, we identify two cis-acting elements and their associated transacting factors (PAL-1 and HLH-1) that are crucial for the temporal-spatial expression of hlh-1 and proper myogenesis. Our data demonstrate that hlh-1 is indeed a direct target of PAL-1 in the posterior embryonic C. elegans muscle lineages, defining a novel in vivo binding site for this crucial developmental regulator. We find that the same enhancer element is also a target of HLH-1 positive auto regulation, underlying (at least in part) the sustained high levels of CeMyoD in bodywall muscle throughout development. Together, these results provide a molecular framework for the gene regulatory network activating the muscle module during embryogenesis.
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Affiliation(s)
- Haiyan Lei
- National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892, USA
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73
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Expression and characterization of aspartic protease gene in eggs and larvae stage of Ancylostoma caninum. Parasitol Res 2009; 104:1327-33. [DOI: 10.1007/s00436-009-1332-1] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2008] [Accepted: 01/05/2009] [Indexed: 10/21/2022]
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74
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Abstract
The elimination of unwanted cells by programmed cell death is a common feature of animal development. Genetic studies in the nematode Caenorhabditis elegans, the fruit fly Drosophila melanogaster, and the mouse have not only revealed the molecular machineries that cause the programmed demise of specific cells, but have also allowed us to get a glimpse of the types of pathways that regulate these machineries during development. Rather than serving as a broad overview of programmed cell death during development, this review focuses on recent advances in our understanding of the regulation of specific programmed cell death events during nematode, fly, and mouse development. Recent studies have revealed that many of the regulatory pathways involved play additional important roles in development, which confirms that the programmed cell death fate is an integral aspect of animal development.
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Affiliation(s)
- Barbara Conradt
- Department of Genetics, Norris Cotton Cancer Center, Dartmouth Medical School, Hanover, New Hampshire 03755, USA.
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75
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Farley BM, Pagano JM, Ryder SP. RNA target specificity of the embryonic cell fate determinant POS-1. RNA (NEW YORK, N.Y.) 2008; 14:2685-97. [PMID: 18952820 PMCID: PMC2590972 DOI: 10.1261/rna.1256708] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/07/2008] [Accepted: 09/10/2008] [Indexed: 05/20/2023]
Abstract
Specification of Caenorhabditis elegans body axes and cell fates occurs prior to the activation of zygotic transcription. Several CCCH-type tandem zinc finger (TZF) proteins coordinate local activation of quiescent maternal mRNAs after fertilization, leading to asymmetric expression of factors required for patterning. The primary determinant of posterior fate is the TZF protein POS-1. Mutants of pos-1 are maternal effect lethal with a terminal phenotype that includes excess pharyngeal tissue and no endoderm or germline. Here, we delineate the consensus POS-1 recognition element (PRE) required for specific recognition of its target mRNAs. The PRE is necessary but not sufficient to pattern the expression of a reporter. The PRE is distinct from sequences recognized by related proteins from both mammals and nematodes, demonstrating that variants of this protein family can recognize divergent RNA sequences. The PRE is found within the 3' untranslated region of 227 maternal transcripts required for early development, including genes involved in endoderm and germline specification. The results enable prediction of novel targets that explain the pleiotropy of the pos-1 phenotype.
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Affiliation(s)
- Brian M Farley
- Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, Massachusetts 01605, USA
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76
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Lin KTH, Broitman-Maduro G, Hung WWK, Cervantes S, Maduro MF. Knockdown of SKN-1 and the Wnt effector TCF/POP-1 reveals differences in endomesoderm specification in C. briggsae as compared with C. elegans. Dev Biol 2008; 325:296-306. [PMID: 18977344 DOI: 10.1016/j.ydbio.2008.10.001] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2008] [Revised: 09/29/2008] [Accepted: 10/01/2008] [Indexed: 02/04/2023]
Abstract
In the nematode, C. elegans, the bZIP/homeodomain transcription factor SKN-1 and the Wnt effector TCF/POP-1 are central to the maternal specification of the endomesoderm prior to gastrulation. The 8-cell stage blastomere MS is primarily a mesodermal precursor, giving rise to cells of the pharynx and body muscle among others, while its sister E clonally generates the entire endoderm (gut). In C. elegans, loss of SKN-1 results in the absence of MS-derived tissues all of the time, and loss of gut most of the time, while loss of POP-1 results in a mis-specification of MS as an E-like cell, resulting in ectopic gut. We show that in C. briggsae, RNAi of skn-1 results in a stronger E defect but no apparent MS defect, while RNAi of pop-1 results in loss of gut and an apparent E to MS transformation, the opposite of the pop-1 knockdown phenotype seen in C. elegans. The difference in pop-1(-) phenotypes correlates with changes in how the endogenous endoderm-specifying end genes are regulated by POP-1 in the two species. Our results suggest that integration of Wnt-dependent and Wnt-independent cell fate specification pathways within the Caenorhabditis genus can occur in different ways.
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Affiliation(s)
- Katy Tan-Hui Lin
- Department of Biology, University of California, Riverside, Riverside, CA 92521, USA
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77
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Courchet J, Buchet-Poyau K, Potemski A, Brès A, Jariel-Encontre I, Billaud M. Interaction with 14-3-3 adaptors regulates the sorting of hMex-3B RNA-binding protein to distinct classes of RNA granules. J Biol Chem 2008; 283:32131-42. [PMID: 18779327 DOI: 10.1074/jbc.m802927200] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
Stress granules (SG) and processing bodies (PBs) are cytoplasmic ribonucleoprotein particles whose assembly is induced by different stimuli. SG are the site of storage of untranslated transcripts formed in response to environmental stress, whereas PBs are involved in mRNA turnover. We recently characterized a novel family of four human proteins related to the Caenorhabditis elegans Mex-3, a RNA binding protein involved in the establishment of the anterior-posterior embryonic asymmetry and in the maintenance of germline pluripotency. We now report that the adaptor proteins 14-3-3 bind to hMex-3B but not to the three other hMex-3 family members. Serine 462, when phosphorylated, is the major 14-3-3 docking site on hMex-3B, and manipulation of this interaction reveals that 14-3-3 both stabilizes hMex-3B and modulates its ability to bind RNA. Furthermore, the complex formed between hMex-3B and Argonaute proteins is excluded from PBs when the interaction with 14-3-3 is disrupted, whereas the recruitment to SG is not affected. Thus, 14-3-3 exerts combined effects on hMex-3B and acts as a major regulator of the sorting between distinct classes of RNA granules.
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Affiliation(s)
- Julien Courchet
- CNRS UMR5201, Laboratoire de Génétique Moléculaire, Signalisation et Cancer, Lyon F-69008, France
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78
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Structure and evolution of the C. elegans embryonic endomesoderm network. BIOCHIMICA ET BIOPHYSICA ACTA-GENE REGULATORY MECHANISMS 2008; 1789:250-60. [PMID: 18778800 DOI: 10.1016/j.bbagrm.2008.07.013] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/06/2008] [Accepted: 07/29/2008] [Indexed: 12/19/2022]
Abstract
The specification of the Caenorhabditis elegans endomesoderm has been the subject of study for more than 15 years. Specification of the 4-cell stage endomesoderm precursor, EMS, occurs as a result of the activation of a transcription factor cascade that starts with SKN-1, coupled with input from the Wnt/beta-catenin asymmetry pathway through the nuclear effector POP-1. As development proceeds, transiently-expressed cell fate factors are succeeded by stable, tissue/organ-specific regulators. The pathway is complex and uses motifs found in all transcriptional networks. Here, the regulators that function in the C. elegans endomesoderm network are described. An examination of the motifs in the network suggests how they may have evolved from simpler gene interactions. Flexibility in the network is evident from the multitude of parallel functions that have been identified and from apparent changes in parts of the corresponding network in Caenorhabditis briggsae. Overall, the complexities of C. elegans endomesoderm specification build a picture of a network that is robust, complex, and still evolving.
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79
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Jadhav S, Rana M, Subramaniam K. Multiple maternal proteins coordinate to restrict the translation of C. elegans nanos-2 to primordial germ cells. Development 2008; 135:1803-12. [PMID: 18417623 DOI: 10.1242/dev.013656] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Although germ cell formation has been relatively well understood in worms and insects, how germ cell-specific developmental programs are initiated is not clear. In Caenorhabditis elegans, translational activation of maternal nos-2 mRNA is the earliest known molecular event specific to the germline founder cell P(4). Cis-elements in nos-2 3'UTR have been shown to mediate translational control; however, the trans-acting proteins are not known. Here, we provide evidence that four maternal RNA-binding proteins, OMA-1, OMA-2, MEX-3 and SPN-4, bind nos-2 3'UTR to suppress its translation, and POS-1, another maternal RNA-binding protein, relieves this suppression in P(4). The POS-1: SPN-4 ratio in P(4) increases significantly over its precursor, P(3); and POS-1 competes with SPN-4 for binding to nos-2 RNA in vitro. We propose temporal changes in the relative concentrations of POS-1 and SPN-4, through their effect on the translational status of maternal mRNAs such as nos-2, initiate germ cell-specific developmental programs in C. elegans.
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Affiliation(s)
- Shreyas Jadhav
- Department of Biological Sciences and Bioengineering, Indian Institute of Technology, Kanpur 208016, India
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80
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Pairing of competitive and topologically distinct regulatory modules enhances patterned gene expression. Mol Syst Biol 2008; 4:163. [PMID: 18277379 PMCID: PMC2267734 DOI: 10.1038/msb.2008.6] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2007] [Accepted: 01/08/2008] [Indexed: 11/08/2022] Open
Abstract
Biological networks are inherently modular, yet little is known about how modules are assembled to enable coordinated and complex functions. We used RNAi and time series, whole-genome microarray analyses to systematically perturb and characterize components of a Caenorhabditis elegans lineage-specific transcriptional regulatory network. These data are supported by selected reporter gene analyses and comprehensive yeast one-hybrid and promoter sequence analyses. Based on these results, we define and characterize two modules composed of muscle- and epidermal-specifying transcription factors that function together within a single cell lineage to robustly specify multiple cell types. The expression of these two modules, although positively regulated by a common factor, is reliably segregated among daughter cells. Our analyses indicate that these modules repress each other, and we propose that this cross-inhibition coupled with their relative time of induction function to enhance the initial asymmetry in their expression patterns, thus leading to the observed invariant gene expression patterns and cell lineage. The coupling of asynchronous and topologically distinct modules may be a general principle of module assembly that functions to potentiate genetic switches.
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81
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Winston WM, Sutherlin M, Wright AJ, Feinberg EH, Hunter CP. Caenorhabditis elegans SID-2 is required for environmental RNA interference. Proc Natl Acad Sci U S A 2007; 104:10565-70. [PMID: 17563372 PMCID: PMC1965553 DOI: 10.1073/pnas.0611282104] [Citation(s) in RCA: 200] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
In plants and in the nematode Caenorhabditis elegans, an RNAi signal can trigger gene silencing in cells distant from the site where silencing is initiated. In plants, this signal is known to be a form of dsRNA, and the signal is most likely a form of dsRNA in C. elegans as well. Furthermore, in C. elegans, dsRNA present in the environment or expressed in ingested bacteria is sufficient to trigger RNAi (environmental RNAi). Ingestion and soaking delivery of dsRNA has also been described for other invertebrates. Here we report the identification and characterization of SID-2, an intestinal luminal transmembrane protein required for environmental RNAi in C. elegans. SID-2, when expressed in the environmental RNAi defective species Caenorhabditis briggsae, confers environmental RNAi.
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Affiliation(s)
- William M. Winston
- Department of Molecular and Cellular Biology, Harvard University, 16 Divinity Avenue, Cambridge, MA 02138
| | - Marie Sutherlin
- Department of Molecular and Cellular Biology, Harvard University, 16 Divinity Avenue, Cambridge, MA 02138
| | - Amanda J. Wright
- Department of Molecular and Cellular Biology, Harvard University, 16 Divinity Avenue, Cambridge, MA 02138
| | - Evan H. Feinberg
- Department of Molecular and Cellular Biology, Harvard University, 16 Divinity Avenue, Cambridge, MA 02138
| | - Craig P. Hunter
- Department of Molecular and Cellular Biology, Harvard University, 16 Divinity Avenue, Cambridge, MA 02138
- To whom correspondence should be addressed. E-mail:
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82
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Buchet-Poyau K, Courchet J, Hir HL, Séraphin B, Scoazec JY, Duret L, Domon-Dell C, Freund JN, Billaud M. Identification and characterization of human Mex-3 proteins, a novel family of evolutionarily conserved RNA-binding proteins differentially localized to processing bodies. Nucleic Acids Res 2007; 35:1289-300. [PMID: 17267406 PMCID: PMC1851655 DOI: 10.1093/nar/gkm016] [Citation(s) in RCA: 112] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
In Caenorhabditis elegans, the Mex-3 protein is a translational regulator that specifies the posterior blastomere identity in the early embryo and contributes to the maintenance of the germline totipotency. We have now identified a family of four homologous human Mex-3 genes, called hMex-3A to -3D that encode proteins containing two heterogeneous nuclear ribonucleoprotein K homology (KH) domains and one carboxy-terminal RING finger module. The hMex-3 are phosphoproteins that bind RNA through their KH domains and shuttle between the nucleus and the cytoplasm via the CRM1-dependent export pathway. Our analysis further revealed that hMex-3A and hMex-3B, but not hMex-3C, colocalize with both the hDcp1a decapping factor and Argonaute (Ago) proteins in processing bodies (P bodies), recently characterized as centers of mRNA turnover. Taken together, these findings indicate that hMex-3 proteins constitute a novel family of evolutionarily conserved RNA-binding proteins, differentially recruited to P bodies and potentially involved in post-transcriptional regulatory mechanisms.
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Affiliation(s)
- Karine Buchet-Poyau
- Université de Lyon, Lyon, F-69003, France; université Lyon 1, Domaine Rockefeller, Lyon, F-69003, France; CNRS UMR 5201, Laboratoire de Génétique Moléculaire, Signalisation et Cancer, Lyon, F-69003, France, CNRS UPR 2167, 6 avenue de la Terrasse, 91198 Gif sur Yvette, France, Service Central d’Anatomie et Cytologie Pathologiques, Hôpital Edouard Herriot, 69437 Lyon, France, CNRS UMR 5558, 16 rue Dubois, 69622 Villeurbanne Cedex, France and INSERM U682, 3 avenue Molière, 67200 Strasbourg, France
| | - Julien Courchet
- Université de Lyon, Lyon, F-69003, France; université Lyon 1, Domaine Rockefeller, Lyon, F-69003, France; CNRS UMR 5201, Laboratoire de Génétique Moléculaire, Signalisation et Cancer, Lyon, F-69003, France, CNRS UPR 2167, 6 avenue de la Terrasse, 91198 Gif sur Yvette, France, Service Central d’Anatomie et Cytologie Pathologiques, Hôpital Edouard Herriot, 69437 Lyon, France, CNRS UMR 5558, 16 rue Dubois, 69622 Villeurbanne Cedex, France and INSERM U682, 3 avenue Molière, 67200 Strasbourg, France
| | - Hervé Le Hir
- Université de Lyon, Lyon, F-69003, France; université Lyon 1, Domaine Rockefeller, Lyon, F-69003, France; CNRS UMR 5201, Laboratoire de Génétique Moléculaire, Signalisation et Cancer, Lyon, F-69003, France, CNRS UPR 2167, 6 avenue de la Terrasse, 91198 Gif sur Yvette, France, Service Central d’Anatomie et Cytologie Pathologiques, Hôpital Edouard Herriot, 69437 Lyon, France, CNRS UMR 5558, 16 rue Dubois, 69622 Villeurbanne Cedex, France and INSERM U682, 3 avenue Molière, 67200 Strasbourg, France
| | - Bertrand Séraphin
- Université de Lyon, Lyon, F-69003, France; université Lyon 1, Domaine Rockefeller, Lyon, F-69003, France; CNRS UMR 5201, Laboratoire de Génétique Moléculaire, Signalisation et Cancer, Lyon, F-69003, France, CNRS UPR 2167, 6 avenue de la Terrasse, 91198 Gif sur Yvette, France, Service Central d’Anatomie et Cytologie Pathologiques, Hôpital Edouard Herriot, 69437 Lyon, France, CNRS UMR 5558, 16 rue Dubois, 69622 Villeurbanne Cedex, France and INSERM U682, 3 avenue Molière, 67200 Strasbourg, France
| | - Jean-Yves Scoazec
- Université de Lyon, Lyon, F-69003, France; université Lyon 1, Domaine Rockefeller, Lyon, F-69003, France; CNRS UMR 5201, Laboratoire de Génétique Moléculaire, Signalisation et Cancer, Lyon, F-69003, France, CNRS UPR 2167, 6 avenue de la Terrasse, 91198 Gif sur Yvette, France, Service Central d’Anatomie et Cytologie Pathologiques, Hôpital Edouard Herriot, 69437 Lyon, France, CNRS UMR 5558, 16 rue Dubois, 69622 Villeurbanne Cedex, France and INSERM U682, 3 avenue Molière, 67200 Strasbourg, France
| | - Laurent Duret
- Université de Lyon, Lyon, F-69003, France; université Lyon 1, Domaine Rockefeller, Lyon, F-69003, France; CNRS UMR 5201, Laboratoire de Génétique Moléculaire, Signalisation et Cancer, Lyon, F-69003, France, CNRS UPR 2167, 6 avenue de la Terrasse, 91198 Gif sur Yvette, France, Service Central d’Anatomie et Cytologie Pathologiques, Hôpital Edouard Herriot, 69437 Lyon, France, CNRS UMR 5558, 16 rue Dubois, 69622 Villeurbanne Cedex, France and INSERM U682, 3 avenue Molière, 67200 Strasbourg, France
| | - Claire Domon-Dell
- Université de Lyon, Lyon, F-69003, France; université Lyon 1, Domaine Rockefeller, Lyon, F-69003, France; CNRS UMR 5201, Laboratoire de Génétique Moléculaire, Signalisation et Cancer, Lyon, F-69003, France, CNRS UPR 2167, 6 avenue de la Terrasse, 91198 Gif sur Yvette, France, Service Central d’Anatomie et Cytologie Pathologiques, Hôpital Edouard Herriot, 69437 Lyon, France, CNRS UMR 5558, 16 rue Dubois, 69622 Villeurbanne Cedex, France and INSERM U682, 3 avenue Molière, 67200 Strasbourg, France
| | - Jean-Noël Freund
- Université de Lyon, Lyon, F-69003, France; université Lyon 1, Domaine Rockefeller, Lyon, F-69003, France; CNRS UMR 5201, Laboratoire de Génétique Moléculaire, Signalisation et Cancer, Lyon, F-69003, France, CNRS UPR 2167, 6 avenue de la Terrasse, 91198 Gif sur Yvette, France, Service Central d’Anatomie et Cytologie Pathologiques, Hôpital Edouard Herriot, 69437 Lyon, France, CNRS UMR 5558, 16 rue Dubois, 69622 Villeurbanne Cedex, France and INSERM U682, 3 avenue Molière, 67200 Strasbourg, France
| | - Marc Billaud
- Université de Lyon, Lyon, F-69003, France; université Lyon 1, Domaine Rockefeller, Lyon, F-69003, France; CNRS UMR 5201, Laboratoire de Génétique Moléculaire, Signalisation et Cancer, Lyon, F-69003, France, CNRS UPR 2167, 6 avenue de la Terrasse, 91198 Gif sur Yvette, France, Service Central d’Anatomie et Cytologie Pathologiques, Hôpital Edouard Herriot, 69437 Lyon, France, CNRS UMR 5558, 16 rue Dubois, 69622 Villeurbanne Cedex, France and INSERM U682, 3 avenue Molière, 67200 Strasbourg, France
- *To whom correspondence should be addressed. Tel: (+33) 478 77 72 14; Fax: (+33) 478 77 72 20; E-mail:
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83
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Baugh LR, Hunter CP. MyoD, modularity, and myogenesis: conservation of regulators and redundancy in C. elegans. Genes Dev 2007; 20:3342-6. [PMID: 17182863 DOI: 10.1101/gad.1507606] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Affiliation(s)
- L Ryan Baugh
- Howard Hughes Medical Institute and Division of Biology, California Institute of Technology, Pasadena, California 91125, USA.
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84
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Lublin AL, Evans TC. The RNA-binding proteins PUF-5, PUF-6, and PUF-7 reveal multiple systems for maternal mRNA regulation during C. elegans oogenesis. Dev Biol 2006; 303:635-49. [PMID: 17234175 DOI: 10.1016/j.ydbio.2006.12.004] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2006] [Revised: 11/25/2006] [Accepted: 12/02/2006] [Indexed: 02/04/2023]
Abstract
In metazoans, many mRNAs needed for embryogenesis are produced during oogenesis and must be tightly regulated during the complex events of oocyte development. In C. elegans, translation of the Notch receptor GLP-1 is repressed during oogenesis and is then activated specifically in anterior cells of the early embryo. The KH domain protein GLD-1 represses glp-1 translation during early stages of meiosis, but the factors that repress glp-1 during late oogenesis are not known. Here, we provide evidence that the PUF domain protein PUF-5 and two nearly identical PUF proteins PUF-6 and PUF-7 function during a specific period of oocyte differentiation to repress glp-1 and other maternal mRNAs. Depletion of PUF-5 and PUF-6/7 together caused defects in oocyte formation and early embryonic cell divisions. Loss of PUF-5 and PUF-6/7 also caused inappropriate expression of GLP-1 protein in oocytes, but GLP-1 remained repressed in meiotic germ cells. PUF-5 and PUF-6/7 function was required directly or indirectly for translational repression through elements of the glp-1 3' untranslated region. Oogenesis and embryonic defects could not be rescued by loss of GLP-1 activity, suggesting that PUF-5 and PUF-6/7 regulate other mRNAs in addition to glp-1. PUF-5 and PUF-6/7 depletion, however, did not perturb repression of the maternal factors GLD-1 and POS-1, suggesting that subsets of maternal gene products may be regulated by distinct pathways. Interestingly, PUF-5 protein was detected exclusively during mid to late oogenesis but became undetectable prior to completion of oocyte differentiation. These results reveal a previously unknown maternal mRNA control system that is specific to late stages of oogenesis and suggest new functions for PUF family proteins in post-mitotic differentiation. Multiple sets of RNA-binding complexes function in different domains of the C. elegans germ line to maintain silencing of Notch/glp-1 and other mRNAs.
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Affiliation(s)
- Alex L Lublin
- Department of Cell and Developmental Biology, University of Colorado School of Medicine, Mail Stop 8108, P.O. Box 6511, Aurora, CO 80045, USA
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85
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Fukushige T, Brodigan TM, Schriefer LA, Waterston RH, Krause M. Defining the transcriptional redundancy of early bodywall muscle development in C. elegans: evidence for a unified theory of animal muscle development. Genes Dev 2006; 20:3395-406. [PMID: 17142668 PMCID: PMC1698447 DOI: 10.1101/gad.1481706] [Citation(s) in RCA: 87] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Myogenic regulatory factors (MRFs) are required for mammalian skeletal myogenesis. In contrast, bodywall muscle is readily detectable in Caenorhabditis elegans embryos lacking activity of the lone MRF ortholog HLH-1, indicating that additional myogenic factors must function in the nematode. We find that two additional C. elegans proteins, UNC-120/SRF and HND-1/HAND, can convert naïve blastomeres to muscle when overproduced ectopically in the embryo. In addition, we have used genetic null mutants to demonstrate that both of these factors act in concert with HLH-1 to regulate myogenesis. Loss of all three factors results in embryos that lack detectable bodywall muscle differentiation, identifying this trio as a set that is both necessary and sufficient for bodywall myogenesis in C. elegans. In mammals, SRF and HAND play prominent roles in regulating smooth and cardiac muscle development. That C. elegans bodywall muscle development is dependent on transcription factors that are associated with all three types of mammalian muscle supports a theory that all animal muscle types are derived from a common ancestral contractile cell type.
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Affiliation(s)
- Tetsunari Fukushige
- Laboratory of Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892, USA
| | - Thomas M. Brodigan
- Laboratory of Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892, USA
| | | | - Robert H. Waterston
- Department of Genome Sciences, University of Washington, Seattle, Washington 98195, USA
| | - Michael Krause
- Laboratory of Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892, USA
- Corresponding author.E-MAIL ; FAX (301) 496-0201
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86
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Abstract
The endomesoderm gene regulatory network (GRN) of C. elegans is a rich resource for studying the properties of cell-fate-specification pathways. This GRN contains both cell-autonomous and cell non-autonomous mechanisms, includes network motifs found in other GRNs, and ties maternal factors to terminal differentiation genes through a regulatory cascade. In most cases, upstream regulators and their direct downstream targets are known. With the availability of resources to study close and distant relatives of C. elegans, the molecular evolution of this network can now be examined. Within Caenorhabditis, components of the endomesoderm GRN are well conserved. A cursory examination of the preliminary genome sequences of two parasitic nematodes, Haemonchus contortus and Brugia malayi, suggests that evolution in this GRN is occurring most rapidly for the zygotic genes that specify blastomere identity.
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Affiliation(s)
- Morris F Maduro
- Department of Biology, University of California, Riverside, Riverside, CA 92521, USA.
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87
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Olesnicky EC, Brent AE, Tonnes L, Walker M, Pultz MA, Leaf D, Desplan C. AcaudalmRNA gradient controls posterior development in the waspNasonia. Development 2006; 133:3973-82. [PMID: 16971471 DOI: 10.1242/dev.02576] [Citation(s) in RCA: 107] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
One of the earliest steps of embryonic development is the establishment of polarity along the anteroposterior axis. Extensive studies of Drosophila embryonic development have elucidated mechanisms for establishing polarity, while studies with other model systems have found that many of these molecular components are conserved through evolution. One exception is Bicoid, the master organizer of anterior development in Drosophila and higher dipterans, which is not conserved. Thus, the study of anteroposterior patterning in insects that lack Bicoid can provide insight into the evolution of the diversity of body plan patterning networks. To this end, we have established the long germ parasitic wasp Nasonia vitripennis as a model for comparative studies with Drosophila.Here we report that, in Nasonia, a gradient of localized caudal mRNA directs posterior patterning, whereas, in Drosophila, the gradient of maternal Caudal protein is established through translational repression by Bicoid of homogeneous caudalmRNA. Loss of caudal function in Nasonia results in severe segmentation defects. We show that Nasonia caudal is an activator of gap gene expression that acts far towards the anterior of the embryo, placing it atop a cascade of early patterning. By contrast, activation of gap genes in flies relies on redundant functions of Bicoid and Caudal, leading to a lack of dramatic action on gap gene expression: caudal instead plays a limited role as an activator of pair-rule gene expression. These studies,together with studies in short germ insects, suggest that caudal is an ancestral master organizer of patterning, and that its role has been reduced in higher dipterans such as Drosophila.
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88
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Maduro MF, Broitman-Maduro G, Mengarelli I, Rothman JH. Maternal deployment of the embryonic SKN-1-->MED-1,2 cell specification pathway in C. elegans. Dev Biol 2006; 301:590-601. [PMID: 16979152 DOI: 10.1016/j.ydbio.2006.08.029] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2006] [Revised: 08/12/2006] [Accepted: 08/15/2006] [Indexed: 10/24/2022]
Abstract
We have previously shown that the MED-1,2 divergent GATA factors act apparently zygotically to specify the fates of the MS (mesoderm) and E (endoderm) sister cells, born at the 7-cell stage of C. elegans embryogenesis. In the E cell, MED-1,2 activate transcription of the endoderm-promoting end-1 and end-3 genes. We demonstrate by in situ hybridization that med transcripts accumulate both in the EMS cell and in the maternal germline in a SKN-1-dependent manner. Removal of zygotic med function alone results in a weakly impenetrant loss of endoderm. However, med-1,2(-) embryos made by mothers in which germline med transcripts have been abrogated by transgene cosuppression fail to make endoderm 50% of the time, similar to the phenotype seen by RNAi. We also find that reduction of Med or End activity results in aberrant numbers of intestinal cells in embryos that make endoderm. We further show that regulation of the paralogous end-1 and end-3 genes consists of both shared and distinct inputs, and that END-3 activates end-1 expression. Our data thus reveal three new properties of C. elegans endoderm specification: both maternal and zygotic activities of the med genes act to specify endoderm, defects in endoderm specification also result in defects in gut cell number, and activation of the paralogous end-1 and end-3 genes differs qualitatively in the relative contributions of their upstream regulators.
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Affiliation(s)
- Morris F Maduro
- Department of Biology, 3380 Spieth Hall, University of California, Riverside, Riverside, CA 92521, USA.
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89
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Broitman-Maduro G, Lin KTH, Hung WWK, Maduro MF. Specification of the C. elegans MS blastomere by the T-box factor TBX-35. Development 2006; 133:3097-106. [PMID: 16831832 DOI: 10.1242/dev.02475] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
In C. elegans, many mesodermal cell types are made by descendants of the progenitor MS, born at the seven-cell stage of embryonic development. Descendants of MS contribute to body wall muscle and to the posterior half of the pharynx. We have previously shown that MS is specified by the activity of the divergent MED-1,2 GATA factors. We report that the MED-1,2 target gene tbx-35, which encodes a T-box transcription factor, specifies the MS fate. Embryos homozygous for a putative tbx-35-null mutation fail to generate MS-derived pharynx and body muscle, and instead generate ectopic PAL-1-dependent muscle and hypodermis, tissues normally made by the C blastomere. Conversely, overexpression of tbx-35 results in the generation of ectopic pharynx and muscle tissue. The MS and E sister cells are made different by transduction of a Wnt/MAPK/Src pathway signal through the nuclear effector TCF/POP-1. We show that in E, tbx-35 is repressed in a Wnt-dependent manner that does not require activity of TCF/POP-1, suggesting that an additional nuclear Wnt effector functions in E to repress MS development. Genes of the T-box family are known to function in protostomes and deuterostomes in the specification of mesodermal fates. Our results show that this role has been evolutionarily conserved in the early C. elegans embryo, and that a progenitor of multiple tissue types can be specified by a surprisingly simple gene cascade.
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Affiliation(s)
- Gina Broitman-Maduro
- Department of Biology, University of California, Riverside, Riverside, CA 92521, USA
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90
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Ciosk R, DePalma M, Priess JR. Translational regulators maintain totipotency in the Caenorhabditis elegans germline. Science 2006; 311:851-3. [PMID: 16469927 DOI: 10.1126/science.1122491] [Citation(s) in RCA: 137] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
The molecular mechanisms that maintain totipotency of the germline are not well understood. Here, we show that two conserved translational regulators, MEX-3 and GLD-1, are essential for maintaining totipotency in the Caenorhabditis elegans germline. In mex-3 gld-1 mutants, germ cells transdifferentiate into various somatic cell types such as muscles or neurons. Our findings implicate RNA regulation in the maintenance of totipotency, suggest that multiple mechanisms maintain totipotency at different stages of germline development, and establish a genetically tractable model for studying the development of teratomas.
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Affiliation(s)
- Rafal Ciosk
- Division of Basic Sciences, Fred Hutchinson Cancer Research Center, Seattle, WA 98109, USA.
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91
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Abstract
The synthesis of gene expression data and cis-regulatory analysis permits the elucidation of genomic regulatory networks. These networks provide a direct visualization of the functional interconnections among the regulatory genes and signaling components leading to cell-specific patterns of gene activity. Complex developmental processes are thereby illuminated in ways not revealed by the conventional analysis of individual genes. In this review, we describe emerging networks in several different model systems, and compare them with the gene regulatory network that controls dorsoventral patterning of the Drosophila embryo.
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Affiliation(s)
- Angelike Stathopoulos
- Division of Biology, California Institute of Technology, Pasadena, California 91125, USA.
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92
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Maduro MF, Kasmir JJ, Zhu J, Rothman JH. The Wnt effector POP-1 and the PAL-1/Caudal homeoprotein collaborate with SKN-1 to activate C. elegans endoderm development. Dev Biol 2005; 285:510-23. [PMID: 16084508 DOI: 10.1016/j.ydbio.2005.06.022] [Citation(s) in RCA: 78] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2005] [Revised: 06/12/2005] [Accepted: 06/13/2005] [Indexed: 11/22/2022]
Abstract
POP-1, a Tcf/Lef-1-like target of the convergent Wnt and MAP kinase (MAPK) signaling pathways, functions throughout Caenorhabditis elegans development to generate unequal daughters during asymmetric cell divisions. A particularly prominent such asymmetric division occurs when the EMS blastomere divides to produce MS, a mesoderm precursor, and E, the sole endoderm progenitor. POP-1 allows mesoderm development in the MS lineage by repressing the endoderm-promoting end-1 and end-3 genes. This repression is relieved in the E lineage by Wnt/MAPK signaling, which results in phosphorylation and export of POP-1 from the E nucleus. Here, we report that, in addition to repressing E development in MS, POP-1 also functions positively in endoderm development, in conjunction with the well-characterized endoderm-promoting SKN-1-->MED regulatory cascade. While removal of POP-1 alone results in derepression of endoderm development in the MS lineage, mutations in several genes that result in impenetrant loss of endoderm are strongly enhanced by loss of pop-1 function. A Lef-1-like binding site is essential for activation of an end-1 promoter fusion, suggesting that POP-1 may act directly on end-1. Thus, POP-1 may generate developmental asymmetry during many cell divisions in C. elegans by reiteratively switching from repressive and activating states. Furthermore, we report that the Caudal-like homeodomain protein PAL-1, whose role in early embryogenesis was thought to be exclusive specification of mesectodermal development in the lineage of the C blastomere, can act with POP-1 to activate endoderm specification in the absence of the SKN-1-->MED transcriptional input, accounting for the impenetrance of mutants lacking SKN-1 or MED-1,2 activity. We conclude that the combined action of several separate transcriptional regulatory inputs, including SKN-1, the MEDs, PAL-1, and the Wnt/MAPK-activated form of POP-1, are responsible for activating end gene transcription and endoderm development.
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Affiliation(s)
- Morris F Maduro
- Department of MCD Biology and Neuroscience Research Institute, University of California at Santa Barbara, Santa Barbara, CA 93106, USA
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93
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Reece-Hoyes JS, Keenan ID, Pownall ME, Isaacs HV. A consensus Oct1 binding site is required for the activity of the Xenopus Cdx4 promoter. Dev Biol 2005; 282:509-23. [PMID: 15950614 DOI: 10.1016/j.ydbio.2005.03.035] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2004] [Revised: 03/09/2005] [Accepted: 03/14/2005] [Indexed: 10/25/2022]
Abstract
Cdx homeodomain transcription factors have multiple roles in early vertebrate development. Furthermore, mis-regulation of Cdx expression has been demonstrated in metaplasias and cancers of the gut epithelium. Given the importance of Cdx genes in development and disease, the mechanisms underlying their expression are of considerable interest. We report an analysis of the upstream regulatory regions from the amphibian Xenopus laevis Cdx4 gene. We show that a GFP reporter containing 2.8 kb upstream of the transcription start site is expressed in the posterior of transgenic embryos. Deletion analysis of the upstream sequence reveals that a 247-bp proximal promoter fragment will drive posterior expression in transgenic embryos. We show that 63 bp of upstream sequence, that includes a consensus site for POU-domain octamer-binding proteins, retains significant promoter activity. Co-expression of the octamer-binding protein Oct1 induces expression from a Cdx4 reporter and mutation of the octamer site abolishes activity of the same reporter. We show that the octamer site is highly conserved in the promoters of the human, mouse, chicken, and zebrafish Cdx4 genes and within the promoters of amphibian Cdx1 and Cdx2. These data suggest a conserved function for octamer-binding proteins in the regulation of Cdx family members.
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94
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Shinmyo Y, Mito T, Matsushita T, Sarashina I, Miyawaki K, Ohuchi H, Noji S. caudal is required for gnathal and thoracic patterning and for posterior elongation in the intermediate-germband cricket Gryllus bimaculatus. Mech Dev 2005; 122:231-9. [PMID: 15652710 DOI: 10.1016/j.mod.2004.10.001] [Citation(s) in RCA: 87] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2004] [Revised: 09/27/2004] [Accepted: 10/04/2004] [Indexed: 10/26/2022]
Abstract
Although the molecular mechanisms directing anteroposterior patterning of the Drosophila embryo (long-germband mode) are well understood, how these mechanisms were evolved from an ancestral mode of insect embryogenesis remains largely unknown. In order to gain insight into mechanisms of evolution in insect embryogenesis, we have examined the expression and function of the orthologue of Drosophila caudal (cad) in the intermediate-germband cricket Gryllus bimaculatus. We observed that a posterior (high) to anterior (low) gradient in the levels of Gryllus bimaculatus cad (Gb' cad) transcript was formed in the early-stage embryo, and then Gb' cad was expressed in the posterior growth zone until the posterior segmentation was completed. Reduction of Gb' cad expression level by RNA interference resulted in deletion of the gnathum, thorax, and abdomen in embryos, remaining only anterior head. We found that the gnathal and thoracic segments are formed by Gb' cad probably through the transcriptional regulation of gap genes including Gb' hunchback and Gb' Kruppel. Furthermore, Gb' cad was found to be involved in the posterior elongation, acting as a downstream gene in the Wingless/Armadillo signalling pathways. These findings indicate that Gb' cad does not function as it does in Drosophila, suggesting that regulatory and functional changes of cad occurred during insect evolution. Since Wnt/Cdx pathways are involved in the posterior patterning of vertebrates, such mechanisms may be conserved in animals that undergo sequential segmentation from the posterior growth zone.
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Affiliation(s)
- Yohei Shinmyo
- Department of Biological Science and Technology, Faculty of Engineering, The University of Tokushima, 2-1 Minami-Josanjima-cho, Tokushima City 770-8506, Japan
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95
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Broitman-Maduro G, Maduro MF, Rothman JH. The noncanonical binding site of the MED-1 GATA factor defines differentially regulated target genes in the C. elegans mesendoderm. Dev Cell 2005; 8:427-33. [PMID: 15737937 DOI: 10.1016/j.devcel.2005.01.014] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2004] [Revised: 01/12/2005] [Accepted: 01/13/2005] [Indexed: 11/20/2022]
Abstract
Mesoderm and endoderm in C. elegans arise from sister cells called MS and E, respectively. The identities of both of these mesendodermal progenitors are controlled by MED-1 and -2, members of the GATA factor family. In the E lineage, these factors activate a sequential cascade of GATA factors, beginning with their immediate targets, the endoderm-specifying end genes. We report that MED-1 binds invariant noncanonical sites in the end genes, revealing that the MEDs are atypical members of the GATA factor family that do not recognize GATA sequences. By searching the genome for clusters of these MED sites, we have identified 19 candidate MED targets. Based on their expression patterns, these define three distinct classes of MED-regulated genes: MS-specific, E-specific, and E plus MS-specific. Some MED targets encode transcription factors related to those that regulate mesendoderm development in other phyla, supporting the existence of an ancient metazoan mesendoderm gene regulatory network.
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Affiliation(s)
- Gina Broitman-Maduro
- Department of Biology and Neuroscience Research Institute, University of California, Santa Barbara, Santa Barbara, California 93106, USA
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96
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Baugh LR, Wen JC, Hill AA, Slonim DK, Brown EL, Hunter CP. Synthetic lethal analysis of Caenorhabditis elegans posterior embryonic patterning genes identifies conserved genetic interactions. Genome Biol 2005; 6:R45. [PMID: 15892873 PMCID: PMC1175957 DOI: 10.1186/gb-2005-6-5-r45] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2004] [Revised: 12/24/2004] [Accepted: 03/09/2005] [Indexed: 11/10/2022] Open
Abstract
Phenotypic robustness is evidenced when single-gene mutations do not result in an obvious phenotype. It has been suggested that such phenotypic stability results from 'buffering' activities of homologous genes as well as non-homologous genes acting in parallel pathways. One approach to characterizing mechanisms of phenotypic robustness is to identify genetic interactions, specifically, double mutants where buffering is compromised. To identify interactions among genes implicated in posterior patterning of the Caenorhabditis elegans embryo, we measured synthetic lethality following RNA interference of 22 genes in 15 mutant strains. A pair of homologous T-box transcription factors (tbx-8 and tbx-9) is found to interact in both C. elegans and C. briggsae, indicating that their compensatory function is conserved. Furthermore, a muscle module is defined by transitive interactions between the MyoD homolog hlh-1, another basic helix-loop-helix transcription factor, hnd-1, and the MADS-box transcription factor unc-120. Genetic interactions within a homologous set of genes involved in vertebrate myogenesis indicate broad conservation of the muscle module and suggest that other genetic modules identified in C. elegans will be conserved.
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Affiliation(s)
- L Ryan Baugh
- Department of Molecular and Cellular Biology, Harvard University, Cambridge, MA 02138, USA
- Current address: Biology Division, California Institute of Technology, Pasadena, CA 91125
| | - Joanne C Wen
- Department of Molecular and Cellular Biology, Harvard University, Cambridge, MA 02138, USA
| | - Andrew A Hill
- Department of Genomics, Wyeth Research, Cambridge, MA 02140, USA
| | - Donna K Slonim
- Department of Genomics, Wyeth Research, Cambridge, MA 02140, USA
- Current address: Department of Computer Science, Tufts University, Medford, MA 02155
| | - Eugene L Brown
- Department of Genomics, Wyeth Research, Cambridge, MA 02140, USA
| | - Craig P Hunter
- Department of Molecular and Cellular Biology, Harvard University, Cambridge, MA 02138, USA
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97
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Fukushige T, Krause M. The myogenic potency of HLH-1 reveals wide-spread developmental plasticity in early C. elegans embryos. Development 2005; 132:1795-805. [PMID: 15772130 DOI: 10.1242/dev.01774] [Citation(s) in RCA: 94] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
In vertebrates, striated muscle development depends on both the expression of members of the myogenic regulatory factor family (MRFs) and on extrinsic cellular cues, including Wnt signaling. The 81 embryonically born body wall muscle cells in C. elegans are comparable to the striated muscle of vertebrates. These muscle cells all express the gene hlh-1, encoding HLH-1 (CeMyoD) which is the only MRF-related factor in the nematode. However, genetic studies have shown that body wall muscle development occurs in the absence of HLH-1 activity, making the role of this factor in nematode myogenesis unclear. By ectopically expressing hlh-1 in early blastomeres of the C. elegans embryo, we show that CeMyoD is a bona fide MRF that can convert almost all cells to a muscle-like fate, regardless of their lineage of origin. The window during which ectopic HLH-1 can function is surprisingly broad, spanning the first 3 hours of development when cell lineages are normally established and non-muscle cell fate markers begin to be expressed. We have begun to explore the maternal factors controlling zygotic hlh-1 expression. We find that the Caudal-related homeobox factor PAL-1 can activate hlh-1 in blastomeres that either lack POP-1/TCF or that have down-regulated POP-1/TCF in response to Wnt/MAP kinase signaling. The potent myogenic activity of HLH-1 highlights the remarkable developmental plasticity of early C. elegans blastomeres and reveals the evolutionary conservation of MyoD function.
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Affiliation(s)
- Tetsunari Fukushige
- Laboratory of Molecular Biology, National Institute of Diabetes, Digestive, and Kidney Diseases, NIH, Bethesda, MD 20892, USA
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98
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Baugh LR, Hill AA, Claggett JM, Hill-Harfe K, Wen JC, Slonim DK, Brown EL, Hunter CP. The homeodomain protein PAL-1 specifies a lineage-specific regulatory network in the C. elegans embryo. Development 2005; 132:1843-54. [PMID: 15772128 DOI: 10.1242/dev.01782] [Citation(s) in RCA: 90] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
Maternal and zygotic activities of the homeodomain protein PAL-1 specify the identity and maintain the development of the multipotent C blastomere lineage in the C. elegans embryo. To identify PAL-1 regulatory target genes, we used microarrays to compare transcript abundance in wild-type embryos with mutant embryos lacking a C blastomere and to mutant embryos with extra C blastomeres. pal-1-dependent C-lineage expression was verified for select candidate target genes by reporter gene analysis, though many of the target genes are expressed in additional lineages as well. The set of validated target genes includes 12 transcription factors, an uncharacterized wingless ligand and five uncharacterized genes. Phenotypic analysis demonstrates that the identified PAL-1 target genes affect specification, differentiation and morphogenesis of C-lineage cells. In particular, we show that cell fate-specific genes (or tissue identity genes) and a posterior HOX gene are activated in lineage-specific fashion. Transcription of targets is initiated in four temporal phases, which together with their spatial expression patterns leads to a model of the regulatory network specified by PAL-1.
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Affiliation(s)
- L Ryan Baugh
- Department of Molecular and Cellular Biology, Harvard University, Cambridge, MA 02138, USA
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99
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Konwerski J, Senchuk M, Petty E, Lahaie D, Schisa JA. Cloning and expression analysis ofpos-1 in the nematodesCaenorhabditis briggsae andCaenorhabditis remanei. Dev Dyn 2005; 233:1006-12. [PMID: 15880508 DOI: 10.1002/dvdy.20421] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
The Caenorhabditis elegans pos-1 gene encodes a zinc-finger protein that is required for germline specification during embryogenesis. The maternally provided mRNA is translationally regulated both spatially and temporally during early development. We have cloned orthologs of pos-1 from C. briggsae and C. remanei, two Caenorhabditis species that have diverged from C. elegans by approximately 20-40 million years. Two regions in the 3' untranslated region are highly conserved among all three species. We find that the pos-1 RNA is expressed in the hermaphrodite and female gonads of C. briggsae and C. remanei but POS-1 protein is not detected at high levels in C. briggsae until the 2-cell stage of embryogenesis. The protein expression is restricted to the germline precursors of the embryo. We conclude that pos-1 appears to be translationally regulated in C. briggsae as it is in C. elegans and speculate the conserved 3' UTR sequences may be involved.
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Affiliation(s)
- Jamie Konwerski
- Department of Biology, Central Michigan University, Mount Pleasant, Michigan 48859, USA
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100
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Copf T, Schröder R, Averof M. Ancestral role of caudal genes in axis elongation and segmentation. Proc Natl Acad Sci U S A 2004; 101:17711-5. [PMID: 15598743 PMCID: PMC539741 DOI: 10.1073/pnas.0407327102] [Citation(s) in RCA: 155] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2004] [Indexed: 12/21/2022] Open
Abstract
caudal (cad/Cdx) genes are essential for the formation of posterior structures in Drosophila, Caenorhabditis elegans, and vertebrates. In contrast to Drosophila, the majority of arthropods generate their segments sequentially from a posteriorly located growth zone, a process known as short-germ development. caudal homologues are expressed in the growth zone of diverse short-germ arthropods, but until now their functional role in these animals had not been studied. Here, we use RNA interference to examine the function of caudal genes in two short-germ arthropods, the crustacean Artemia franciscana and the beetle Tribolium castaneum. We show that, in both species, caudal is required for the formation of most body segments. In animals with reduced levels of caudal expression, axis elongation stops, resulting in severe truncations that remove most trunk segments. We also show that caudal function is required for the early phases of segmentation and Hox gene expression. The observed phenotypes suggest that in arthropods caudal had an ancestral role in axis elongation and segmentation, and was required for the formation of most body segments. Similarities to the function of vertebrate Cdx genes in the presomitic mesoderm, from which somites are generated, indicate that this role may also predate the origin of the Bilateria.
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Affiliation(s)
- Tijana Copf
- Institute of Molecular Biology and Biotechnology, 711 10 Iraklio Crete, Greece
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