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Du L, Tracy S, Rifkin SA. Mutagenesis of GATA motifs controlling the endoderm regulator elt-2 reveals distinct dominant and secondary cis-regulatory elements. Dev Biol 2016; 412:160-170. [PMID: 26896592 PMCID: PMC4814310 DOI: 10.1016/j.ydbio.2016.02.013] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2015] [Revised: 02/03/2016] [Accepted: 02/10/2016] [Indexed: 10/22/2022]
Abstract
Cis-regulatory elements (CREs) are crucial links in developmental gene regulatory networks, but in many cases, it can be difficult to discern whether similar CREs are functionally equivalent. We found that despite similar conservation and binding capability to upstream activators, different GATA cis-regulatory motifs within the promoter of the C. elegans endoderm regulator elt-2 play distinctive roles in activating and modulating gene expression throughout development. We fused wild-type and mutant versions of the elt-2 promoter to a gfp reporter and inserted these constructs as single copies into the C. elegans genome. We then counted early embryonic gfp transcripts using single-molecule RNA FISH (smFISH) and quantified gut GFP fluorescence. We determined that a single primary dominant GATA motif located 527bp upstream of the elt-2 start codon was necessary for both embryonic activation and later maintenance of transcription, while nearby secondary GATA motifs played largely subtle roles in modulating postembryonic levels of elt-2. Mutation of the primary activating site increased low-level spatiotemporally ectopic stochastic transcription, indicating that this site acts repressively in non-endoderm cells. Our results reveal that CREs with similar GATA factor binding affinities in close proximity can play very divergent context-dependent roles in regulating the expression of a developmentally critical gene in vivo.
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Affiliation(s)
- Lawrence Du
- Section of Ecology, Behavior, and Evolution, Division of Biological Sciences, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0116, United States
| | - Sharon Tracy
- Section of Ecology, Behavior, and Evolution, Division of Biological Sciences, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0116, United States
| | - Scott A Rifkin
- Section of Ecology, Behavior, and Evolution, Division of Biological Sciences, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0116, United States.
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Iron Overload Coordinately Promotes Ferritin Expression and Fat Accumulation in Caenorhabditis elegans. Genetics 2016; 203:241-53. [PMID: 27017620 DOI: 10.1534/genetics.116.186742] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2016] [Accepted: 03/20/2016] [Indexed: 01/22/2023] Open
Abstract
The trace element iron is crucial for living organisms, since it plays essential roles in numerous cellular functions. Systemic iron overload and the elevated level of ferritin, a ubiquitous intracellular protein that stores and releases iron to maintain the iron homeostasis in cells, has long been epidemiologically associated with obesity and obesity-related diseases. However, the underlying mechanisms of this association remain unclear. Here, using Caenorhabditis elegans, we show that iron overload induces the expression of sgk-1, encoding the serum and glucocorticoid-inducible kinase, to promote the level of ferritin and fat accumulation. Mutation of cyp-23A1, encoding a homolog of human cytochrome P450 CYP7B1 that is related to neonatal hemochromatosis, further enhances the elevated expression of ftn-1, sgk-1, and fat accumulation. sgk-1 positively regulates the expression of acs-20 and vit-2, genes encoding homologs of the mammalian FATP1/4 fatty acid transport proteins and yolk lipoproteins, respectively, to facilitate lipid uptake and translocation for storage under iron overload. This study reveals a completely novel pathway in which sgk-1 plays a central role to synergistically regulate iron and lipid homeostasis, offering not only experimental evidence supporting a previously unverified link between iron and obesity, but also novel insights into the pathogenesis of iron and obesity-related human metabolic diseases.
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Mendenhall AR, Tedesco PM, Sands B, Johnson TE, Brent R. Single Cell Quantification of Reporter Gene Expression in Live Adult Caenorhabditis elegans Reveals Reproducible Cell-Specific Expression Patterns and Underlying Biological Variation. PLoS One 2015; 10:e0124289. [PMID: 25946008 PMCID: PMC4422670 DOI: 10.1371/journal.pone.0124289] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2014] [Accepted: 03/07/2015] [Indexed: 11/22/2022] Open
Abstract
In multicellular organisms such as Caenorhabditis elegans, differences in complex phenotypes such as lifespan correlate with the level of expression of particular engineered reporter genes. In single celled organisms, quantitative understanding of responses to extracellular signals and of cell-to-cell variation in responses has depended on precise measurement of reporter gene expression. Here, we developed microscope-based methods to quantify reporter gene expression in cells of Caenorhabditis elegans with low measurement error. We then quantified expression in strains that carried different configurations of Phsp-16.2-fluorescent-protein reporters, in whole animals, and in all 20 cells of the intestine tissue, which is responsible for most of the fluorescent signal. Some animals bore more recently developed single copy Phsp-16.2 reporters integrated at defined chromosomal sites, others, “classical” multicopy reporter gene arrays integrated at random sites. At the level of whole animals, variation in gene expression was similar: strains with single copy reporters showed the same amount of animal-to-animal variation as strains with multicopy reporters. At the level of cells, in animals with single copy reporters, the pattern of expression in cells within the tissue was highly stereotyped. In animals with multicopy reporters, the cell-specific expression pattern was also stereotyped, but distinct, and somewhat more variable. Our methods are rapid and gentle enough to allow quantification of expression in the same cells of an animal at different times during adult life. They should allow investigators to use changes in reporter expression in single cells in tissues as quantitative phenotypes, and link those to molecular differences. Moreover, by diminishing measurement error, they should make possible dissection of the causes of the remaining, real, variation in expression. Understanding such variation should help reveal its contribution to differences in complex phenotypic outcomes in multicellular organisms.
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Affiliation(s)
- Alexander R. Mendenhall
- Division of Basic Sciences, Fred Hutchinson Cancer Research Center, Seattle, Washington, United States of America
- * E-mail: (RB); (ARM)
| | - Patricia M. Tedesco
- Institute for Behavioral Genetics, University of Colorado, Boulder, Colorado, United States of America
| | - Bryan Sands
- Division of Basic Sciences, Fred Hutchinson Cancer Research Center, Seattle, Washington, United States of America
| | - Thomas E. Johnson
- Institute for Behavioral Genetics, University of Colorado, Boulder, Colorado, United States of America
- Department of Integrative Physiology, University of Colorado, Boulder, Colorado, United States of America
- Biofrontiers Institute, University of Colorado, Boulder, Colorado, United States of America
| | - Roger Brent
- Division of Basic Sciences, Fred Hutchinson Cancer Research Center, Seattle, Washington, United States of America
- * E-mail: (RB); (ARM)
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Reinke V, Krause M, Okkema P. Transcriptional regulation of gene expression in C. elegans. ACTA ACUST UNITED AC 2013:1-34. [PMID: 23801596 DOI: 10.1895/wormbook.1.45.2] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Protein coding gene sequences are converted to mRNA by the highly regulated process of transcription. The precise temporal and spatial control of transcription for many genes is an essential part of development in metazoans. Thus, understanding the molecular mechanisms underlying transcriptional control is essential to understanding cell fate determination during embryogenesis, post-embryonic development, many environmental interactions, and disease-related processes. Studies of transcriptional regulation in C. elegans exploit its genomic simplicity and physical characteristics to define regulatory events with single-cell and minute-time-scale resolution. When combined with the genetics of the system, C. elegans offers a unique and powerful vantage point from which to study how chromatin-associated proteins and their modifications interact with transcription factors and their binding sites to yield precise control of gene expression through transcriptional regulation.
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Affiliation(s)
- Valerie Reinke
- Department of Genetics, Yale University, New Haven, CT 06520, USA.
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DePina AS, Iser WB, Park SS, Maudsley S, Wilson MA, Wolkow CA. Regulation of Caenorhabditis elegans vitellogenesis by DAF-2/IIS through separable transcriptional and posttranscriptional mechanisms. BMC PHYSIOLOGY 2011; 11:11. [PMID: 21749693 PMCID: PMC3160409 DOI: 10.1186/1472-6793-11-11] [Citation(s) in RCA: 67] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/22/2011] [Accepted: 07/12/2011] [Indexed: 11/11/2022]
Abstract
Background Evolutionary theories of aging propose that longevity evolves as a competition between reproduction and somatic maintenance for a finite pool of resources. Reproduction is thought to shorten lifespan by depleting resources from processes promoting somatic maintenance. Maternal yolk production, vitellogenesis, represents a significant maternal cost for reproduction and is suppressed under genetic and environmental conditions that extend lifespan. However, little is known about the pathways regulating vitellogenesis in response to prolongevity cues. Results In order to identify mechanisms that suppress vitellogenesis under prolongevity conditions, we studied factors regulating vitellogenesis in C. elegans nematodes. In C. elegans, vitellogenesis is depressed in the absence of insulin-like signaling (IIS). We found that the C. elegans daf-2/IIS pathway regulates vitellogenesis through two mechanisms. vit-2 transcript levels in daf-2 mutants were indirectly regulated through a germline-dependent signal, and could be rescued by introduction of daf-2(+) sperm. However, yolk protein (YP) levels in daf-2 mutants were also regulated by germline-independent posttranscriptional mechanisms. Conclusions C. elegans vitellogenesis is regulated transcriptionally and posttranscriptionally in response to environmental and reproductive cues. The daf-2 pathway suppressed vitellogenesis through transcriptional mechanisms reflecting reproductive phenotypes, as well as distinct posttranscriptional mechanisms. This study reveals that pleiotropic effects of IIS pathway mutations can converge on a common downstream target, vitellogenesis, as a mechanism to modulate longevity.
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Affiliation(s)
- Ana S DePina
- Laboratory of Neurosciences, NIA Intramural Research Program, NIH, Baltimore, MD 21224, USA
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ELT-2 is the predominant transcription factor controlling differentiation and function of the C. elegans intestine, from embryo to adult. Dev Biol 2008; 327:551-65. [PMID: 19111532 DOI: 10.1016/j.ydbio.2008.11.034] [Citation(s) in RCA: 118] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2008] [Accepted: 11/17/2008] [Indexed: 12/14/2022]
Abstract
Starting with SAGE-libraries prepared from C. elegans FAC-sorted embryonic intestine cells (8E-16E cell stage), from total embryos and from purified oocytes, and taking advantage of the NextDB in situ hybridization data base, we define sets of genes highly expressed from the zygotic genome, and expressed either exclusively or preferentially in the embryonic intestine or in the intestine of newly hatched larvae; we had previously defined a similarly expressed set of genes from the adult intestine. We show that an extended TGATAA-like sequence is essentially the only candidate for a cis-acting regulatory motif common to intestine genes expressed at all stages. This sequence is a strong ELT-2 binding site and matches the sequence of GATA-like sites found to be important for the expression of every intestinal gene so far analyzed experimentally. We show that the majority of these three sets of highly expressed intestinal-specific/intestinal-enriched genes respond strongly to ectopic expression of ELT-2 within the embryo. By flow-sorting elt-2(null) larvae from elt-2(+) larvae and then preparing Solexa/Illumina-SAGE libraries, we show that the majority of these genes also respond strongly to loss-of-function of ELT-2. To test the consequences of loss of other transcription factors identified in the embryonic intestine, we develop a strain of worms that is RNAi-sensitive only in the intestine; however, we are unable (with one possible exception) to identify any other transcription factor whose intestinal loss-of-function causes a phenotype of comparable severity to the phenotype caused by loss of ELT-2. Overall, our results support a model in which ELT-2 is the predominant transcription factor in the post-specification C. elegans intestine and participates directly in the transcriptional regulation of the majority (>80%) of intestinal genes. We present evidence that ELT-2 plays a central role in most aspects of C. elegans intestinal physiology: establishing the structure of the enterocyte, regulating enzymes and transporters involved in digestion and nutrition, responding to environmental toxins and pathogenic infections, and regulating the downstream intestinal components of the daf-2/daf-16 pathway influencing aging and longevity.
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Pauli F, Liu Y, Kim YA, Chen PJ, Kim SK. Chromosomal clustering and GATA transcriptional regulation of intestine-expressed genes in C. elegans. Development 2005; 133:287-95. [PMID: 16354718 PMCID: PMC4719054 DOI: 10.1242/dev.02185] [Citation(s) in RCA: 109] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
We used mRNA tagging to identify genes expressed in the intestine of C. elegans. Animals expressing an epitope-tagged protein that binds the poly-A tail of mRNAs (FLAG::PAB-1) from an intestine-specific promoter (ges-1) were used to immunoprecipitate FLAG::PAB-1/mRNA complexes from the intestine. A total of 1938 intestine-expressed genes (P<0.001) were identified using DNA microarrays. First, we compared the intestine-expressed genes with those expressed in the muscle and germline, and identified 510 genes enriched in all three tissues and 624 intestine-, 230 muscle- and 1135 germ line-enriched genes. Second, we showed that the 1938 intestine-expressed genes were physically clustered on the chromosomes, suggesting that the order of genes in the genome is influenced by the effect of chromatin domains on gene expression. Furthermore, the commonly expressed genes showed more chromosomal clustering than the tissue-enriched genes, suggesting that chromatin domains may influence housekeeping genes more than tissue-specific genes. Third, in order to gain further insight into the regulation of intestinal gene expression, we searched for regulatory motifs. This analysis found that the promoters of the intestine genes were enriched for the GATA transcription factor consensus binding sequence. We experimentally verified these results by showing that the GATA motif is required in cis and that GATA transcription factors are required in trans for expression of these intestinal genes.
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Affiliation(s)
- Florencia Pauli
- Department of Genetics, Stanford University, Stanford, CA 94305, USA
| | - Yueyi Liu
- Stanford Medical Informatics, Stanford University, Stanford, CA 94305, USA
| | - Yoona A. Kim
- Department of Developmental Biology, Stanford University, Stanford, CA 94305, USA
| | | | - Stuart K. Kim
- Department of Genetics, Stanford University, Stanford, CA 94305, USA
- Department of Developmental Biology, Stanford University, Stanford, CA 94305, USA
- Author for correspondence ()
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Timmons L, Tabara H, Mello CC, Fire AZ. Inducible systemic RNA silencing in Caenorhabditis elegans. Mol Biol Cell 2003; 14:2972-83. [PMID: 12857879 PMCID: PMC165691 DOI: 10.1091/mbc.e03-01-0858] [Citation(s) in RCA: 109] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Introduction of double-stranded RNA (dsRNA) can elicit a gene-specific RNA interference response in a variety of organisms and cell types. In many cases, this response has a systemic character in that silencing of gene expression is observed in cells distal from the site of dsRNA delivery. The molecular mechanisms underlying the mobile nature of RNA silencing are unknown. For example, although cellular entry of dsRNA is possible, cellular exit of dsRNA from normal animal cells has not been directly observed. We provide evidence that transgenic strains of Caenorhabditis elegans transcribing dsRNA from a tissue-specific promoter do not exhibit comprehensive systemic RNA interference phenotypes. In these same animals, modifications of environmental conditions can result in more robust systemic RNA silencing. Additionally, we find that genetic mutations can influence the systemic character of RNA silencing in C. elegans and can separate mechanisms underlying systemic RNA silencing into tissue-specific components. These data suggest that trafficking of RNA silencing signals in C. elegans is regulated by specific physiological and genetic factors.
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Affiliation(s)
- Lisa Timmons
- Department of Molecular Biosciences, The University of Kansas, Lawrence, Kansas 66045, USA.
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Park BJ, Lee DG, Yu JR, Jung SK, Choi K, Lee J, Lee J, Kim YS, Lee JI, Kwon JY, Lee J, Singson A, Song WK, Eom SH, Park CS, Kim DH, Bandyopadhyay J, Ahnn J. Calreticulin, a calcium-binding molecular chaperone, is required for stress response and fertility in Caenorhabditis elegans. Mol Biol Cell 2001; 12:2835-45. [PMID: 11553721 PMCID: PMC59717 DOI: 10.1091/mbc.12.9.2835] [Citation(s) in RCA: 108] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2001] [Revised: 06/19/2001] [Accepted: 07/08/2001] [Indexed: 11/11/2022] Open
Abstract
Calreticulin (CRT), a Ca(2+)-binding protein known to have many cellular functions, including regulation of Ca(2+) homoeostasis and chaperone activity, is essential for heart and brain development during embryogenesis in mice. Here, we report the functional characterization of Caenorhabditis elegans calreticulin (crt-1). A crt-1 null mutant does not result in embryonic lethality but shows temperature-dependent reproduction defects. In C. elegans CRT-1 is expressed in the intestine, pharynx, body-wall muscles, head neurons, coelomocytes, and in sperm. crt-1 males exhibit reduced mating efficiency and defects late in sperm development in addition to defects in oocyte development and/or somatic gonad function in hermaphrodites. Furthermore, crt-1 and itr-1 (inositol triphosphate receptor) together are required for normal behavioral rhythms. crt-1 transcript level is elevated under stress conditions, suggesting that CRT-1 may be important for stress-induced chaperoning function in C. elegans.
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Affiliation(s)
- B J Park
- Department of Life Science, Kwangju Institute of Science and Technology, Kwangju, 500-712, Korea
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Gilleard JS, Barry JD, Johnstone IL. cis regulatory requirements for hypodermal cell-specific expression of the Caenorhabditis elegans cuticle collagen gene dpy-7. Mol Cell Biol 1997; 17:2301-11. [PMID: 9121480 PMCID: PMC232079 DOI: 10.1128/mcb.17.4.2301] [Citation(s) in RCA: 166] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
The Caenorhabditis elegans cuticle collagens are encoded by a multigene family of between 50 and 100 members and are the major component of the nematode cuticular exoskeleton. They are synthesized in the hypodermis prior to secretion and incorporation into the cuticle and exhibit complex patterns of spatial and temporal expression. We have investigated the cis regulatory requirements for tissue- and stage-specific expression of the cuticle collagen gene dpy-7 and have identified a compact regulatory element which is sufficient to specify hypodermal cell reporter gene expression. This element appears to be a true tissue-specific promoter element, since it encompasses the dpy-7 transcription initiation sites and functions in an orientation-dependent manner. We have also shown, by interspecies transformation experiments, that the dpy-7 cis regulatory elements are functionally conserved between C. elegans and C. briggsae, and comparative sequence analysis supports the importance of the regulatory sequence that we have identified by reporter gene analysis. All of our data suggest that the spatial expression of the dpy-7 cuticle collagen gene is established essentially by a small tissue-specific promoter element and does not require upstream activator or repressor elements. In addition, we have found the DPY-7 polypeptide is very highly conserved between the two species and that the C. briggsae polypeptide can function appropriately within the C. elegans cuticle. This finding suggests a remarkably high level of conservation of individual cuticle components, and their interactions, between these two nematode species.
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Affiliation(s)
- J S Gilleard
- Wellcome Unit of Molecular Parasitology, Anderson College, University of Glasgow, United Kingdom.
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