scholarly journals The Caenorhabditis elegans NK-2 class homeoprotein CEH-22 is involved in combinatorial activation of gene expression in pharyngeal muscle

Development ◽  
1994 ◽  
Vol 120 (8) ◽  
pp. 2175-2186 ◽  
Author(s):  
P.G. Okkema ◽  
A. Fire
Keyword(s):  
Gene Expression ◽  
Caenorhabditis Elegans ◽  
Specific Activity ◽  
Myogenic Differentiation ◽  
Smooth Muscles ◽  
Chain Gene ◽  
Cdna Expression Library ◽  
Homeodomain Protein ◽  
Pharyngeal Muscle ◽  
Pharyngeal Muscles

The pharyngeal muscles of Caenorhabditis elegans are single sarcomere muscles used for feeding. Like vertebrate cardiac and smooth muscles, C. elegans pharyngeal muscle does not express any of the known members of the MyoD family of myogenic factors. To identify mechanisms regulating gene expression in this tissue, we have characterized a pharyngeal muscle-specific enhancer from myo-2, a myosin heavy chain gene expressed exclusively in pharyngeal muscle. Assaying enhancer function in transgenic animals, we identified three subelements, designated A, B and C, that contribute to myo-2 enhancer activity. These subelements are individually inactive; however, any combination of two or more subelements forms a functional enhancer. The B and C subelements have distinct cell type specificities. A duplication of B activates transcription in a subset of pharyngeal muscles (m3, m4, m5 and m7). A duplication of C activates transcription in all pharyngeal cells, muscle and non-muscle. Thus, the activity of the myo-2 enhancer is regulated by a combination of pharyngeal muscle-type-specific and organ-specific signals. Screening a cDNA expression library, we identified a gene encoding an NK-2 class homeodomain protein, CEH-22, that specifically binds a site necessary for activity of the B subelement. CEH-22 protein is first expressed prior to myogenic differentiation and is present in the same subset of pharyngeal muscles in which B is active. Expression continues throughout embryonic and larval development. This expression pattern suggests CEH-22 plays a key role in pharyngeal muscle-specific activity of the myo-2 enhancer.

The Caenorhabditis elegans NK-2 homeobox gene ceh-22 activates pharyngeal muscle gene expression in combination with pha-1 and is required for normal pharyngeal development

Development ◽  
1997 ◽  
Vol 124 (20) ◽  
pp. 3965-3973 ◽  
Author(s):  
P.G. Okkema ◽  
E. Ha ◽  
C. Haun ◽  
W. Chen ◽  
A. Fire
Keyword(s):  
Gene Expression ◽  
Caenorhabditis Elegans ◽  
Muscle Development ◽  
Synergistic Effects ◽  
Chain Gene ◽  
Loss Of Function ◽  
Pharyngeal Muscle ◽  
Muscle Gene Expression ◽  
Pharyngeal Muscles ◽  
Muscle Gene

Pharyngeal muscle development in the nematode Caenorhabditis elegans appears to share similarities with cardiac muscle development in other species. We have previously described CEH-22, an NK-2 class homeodomain transcription factor similar to Drosophila tinman and vertebrate Nkx2-5, which is expressed exclusively in the pharyngeal muscles. In vitro, CEH-22 binds the enhancer from myo-2, a pharyngeal muscle-specific myosin heavy chain gene. In this paper, we examine the role CEH-22 plays in pharyngeal muscle development and gene activation by (a) ectopically expressing ceh-22 in transgenic C. elegans and (b) examining the phenotype of a ceh-22 loss-of-function mutant. These experiments indicate that CEH-22 is an activator of myo-2 expression and that it is required for normal pharyngeal muscle development. However, ceh-22 is necessary for neither formation of the pharyngeal muscles, nor for myo-2 expression. Our data suggest parallel and potentially compensating pathways contribute to pharyngeal muscle differentiation. We also examine the relationship between ceh-22 and the pharyngeal organ-specific differentiation gene pha-1. Mutations in ceh-22 and pha-1 have strongly synergistic effects on pharyngeal muscle gene expression; in addition, a pha-1 mutation enhances the lethal phenotype caused by a mutation in ceh-22. Wild-type pha-1 is not required for the onset of ceh-22 expression but it appears necessary for maintained expression of ceh-22.

The DAF-3 Smad binds DNA and represses gene expression in the Caenorhabditis elegans pharynx

Development ◽  
1999 ◽  
Vol 126 (1) ◽  
pp. 97-107 ◽  
Author(s):  
J.D. Thatcher ◽  
C. Haun ◽  
P.G. Okkema
Keyword(s):  
Gene Expression ◽  
Caenorhabditis Elegans ◽  
Recognition Sequence ◽  
Mobility Shift ◽  
Enhancer Activity ◽  
Gene Target ◽  
Gfp Reporter ◽  
Pharyngeal Muscles ◽  
Gel Mobility Shift ◽  
Dauer Larvae

Gene expression in the pharyngeal muscles of Caenorhabditis elegans is controlled in part by organ-specific signals, which in the myo-2 gene target a short DNA sequence termed the C subelement. To identify genes contributing to these signals, we performed a yeast one-hybrid screen for cDNAs encoding factors that bind the C subelement. One clone recovered was from daf-3, which encodes a Smad most closely related to vertebrate Smad4. We demonstrated that DAF-3 binds C subelement DNA directly and specifically using gel mobility shift and DNase1 protection assays. Mutation of any base in the sequence GTCTG interfered with binding in the gel mobility shift assay, demonstrating that this pentanucleotide is a core recognition sequence for DAF-3 binding. daf-3 is known to promote formation of dauer larvae and this activity is negatively regulated by TGFbeta-like signaling. To determine how daf-3 affects C subelement enhancer activity in vivo, we examined expression a gfp reporter controlled by a concatenated C subelement oligonucleotide in daf-3 mutants and other mutants affecting the TGFbeta-like signaling pathway controlling dauer formation. Our results demonstrate that wild-type daf-3 can repress C subelement enhancer activity during larval development and, like its dauer-promoting activity, daf-3's repressor activity is negatively regulated by TGFbeta-like signaling. We have examined expression of this gfp reporter in dauer larvae and have observed no daf-3-dependent repression of C activity. These results suggest daf-3 directly regulates pharyngeal gene expression during non-dauer development.

scholarly journals Combinatorial chromatin dynamics foster accurate cardiopharyngeal fate choices

2019 ◽  
Author(s):  
Claudia Racioppi ◽  
Keira A Wiechecki ◽  
Lionel Christiaen
Keyword(s):  
Gene Expression ◽  
Specific Activity ◽  
Expression Profiles ◽  
Regulatory Elements ◽  
Chromatin Accessibility ◽  
Control Gene ◽  
Specific Expression ◽  
Pharyngeal Muscle ◽  
Control Gene Expression ◽  
Multipotent Progenitors

ABSTRACTIn embryos, lineage-specific profiles of chromatin accessibility control gene expression by modulating transcription, and thus impact multipotent progenitor states and subsequent fate choices. Subsets of cardiac and pharyngeal/head muscles share a common origin in the cardiopharyngeal mesoderm, but the chromatin landscapes that govern multipotent progenitors’ competence and early fate choices remain largely elusive. Here, we leveraged the simplicity of the chordate model Ciona to profile chromatin accessibility through stereotyped transitions from naive Mesp+ mesoderm to distinct fate-restricted heart and pharyngeal muscle precursors. An FGF-Foxf pathway acts in multipotent progenitors to establish cardiopharyngeal-specific patterns of accessibility, which govern later heart vs. pharyngeal muscle-specific expression profiles, demonstrating extensive spatiotemporal decoupling between early cardiopharyngeal enhancer accessibility and late cell-type-specific activity. Combinations of cis-regulatory elements with distinct chromatin accessibility profiles are required to activate of Ebf and Tbx1/10, two key determinants of cardiopharyngeal fate choices. We propose that this higher order combinatorial logic increases the repertoire of regulatory inputs that control gene expression, through either accessibility and/or activity, thus fostering spatially and temporally accurate fate choices.

scholarly journals Combinatorial chromatin dynamics foster accurate cardiopharyngeal fate choices

eLife ◽  
2019 ◽  
Vol 8 ◽  
Author(s):  
Claudia Racioppi ◽  
Keira A Wiechecki ◽  
Lionel Christiaen
Keyword(s):  
Gene Expression ◽  
Specific Activity ◽  
Expression Profiles ◽  
Regulatory Elements ◽  
Chromatin Accessibility ◽  
Specific Gene ◽  
Specific Expression ◽  
Pharyngeal Muscle ◽  
Chromatin Dynamics ◽  
Multipotent Progenitors

During embryogenesis, chromatin accessibility profiles control lineage-specific gene expression by modulating transcription, thus impacting multipotent progenitor states and subsequent fate choices. Subsets of cardiac and pharyngeal/head muscles share a common origin in the cardiopharyngeal mesoderm, but the chromatin landscapes that govern multipotent progenitors competence and early fate choices remain largely elusive. Here, we leveraged the simplicity of the chordate model Ciona to profile chromatin accessibility through stereotyped transitions from naive Mesp+ mesoderm to distinct fate-restricted heart and pharyngeal muscle precursors. An FGF-Foxf pathway acts in multipotent progenitors to establish cardiopharyngeal-specific patterns of accessibility, which govern later heart vs. pharyngeal muscle-specific expression profiles, demonstrating extensive spatiotemporal decoupling between early cardiopharyngeal enhancer accessibility and late cell-type-specific activity. We found that multiple cis-regulatory elements, with distinct chromatin accessibility profiles and motif compositions, are required to activate Ebf and Tbx1/10, two key determinants of cardiopharyngeal fate choices. We propose that these ‘combined enhancers’ foster spatially and temporally accurate fate choices, by increasing the repertoire of regulatory inputs that control gene expression, through either accessibility and/or activity.

The genetics of feeding in Caenorhabditis elegans.

Genetics ◽  
1993 ◽  
Vol 133 (4) ◽  
pp. 897-917 ◽  
Author(s):  
L Avery
Keyword(s):  
Nervous System ◽  
Caenorhabditis Elegans ◽  
Direct Evidence ◽  
Muscle Membrane ◽  
Excitable Cells ◽  
Pharyngeal Muscle ◽  
Genetic Mosaic ◽  
Pharyngeal Muscles ◽  
Pharmacological Studies ◽  
Pha Genes

Abstract The pharynx of Caenorhabditis elegans is a nearly self-contained neuromuscular organ responsible for feeding. To identify genes involved in the development or function of the excitable cells of the pharynx, I screened for worms with visible defects in pharyngeal feeding behavior. Fifty-two mutations identified 35 genes, at least 22 previously unknown. The genes broke down into three broad classes: 2 pha genes, mutations in which caused defects in the shape of the pharynx, 7 phm genes, mutations in which caused defects in the contractile structures of the pharyngeal muscle, and 26 eat genes, mutants in which had abnormal pharyngeal muscle motions, but had normally shaped and normally birefringent pharynxes capable of vigorous contraction. Although the Eat phenotypes were diverse, most resembled those caused by defects in the pharyngeal nervous system. For some of the eat genes there is direct evidence from previous genetic mosaic and pharmacological studies that they do in fact affect nervous system. In eat-5 mutants the motions of the different parts of the pharynx were poorly synchronized. eat-6 and eat-12 mutants failed to relax their pharyngeal muscles properly. These pharyngeal motion defects are most easily explained as resulting from abnormal electrical excitability of the pharyngeal muscle membrane.

scholarly journals The Caenorhabditis elegans paxillin orthologue, PXL-1, is required for pharyngeal muscle contraction and for viability

2011 ◽  
Vol 22 (14) ◽  
pp. 2551-2563 ◽  
Author(s):  
Adam Warner ◽  
Hiroshi Qadota ◽  
Guy M. Benian ◽  
A. Wayne Vogl ◽  
Donald G. Moerman
Keyword(s):  
Caenorhabditis Elegans ◽  
Body Wall ◽  
Fluorescent Protein ◽  
Repeat Unit ◽  
Body Wall Muscle ◽  
Loss Of Function ◽  
Pharyngeal Muscle ◽  
Adhesion Sites ◽  
Pharyngeal Muscles ◽  
Green Fluorescent

We have identified the gene C28H8.6 (pxl-1) as the Caenorhabditis elegans orthologue of vertebrate paxillin. PXL-1 contains the four C-terminal LIM domains conserved in paxillin across all species and three of the five LD motifs found in the N-terminal half of most paxillins. In body wall muscle, PXL-1 antibodies and a full-length green fluorescent protein translational fusion localize to adhesion sites in the sarcomere, the functional repeat unit in muscle responsible for contraction. PXL-1 also localizes to ring-shaped structures near the sarcolemma in pharyngeal muscle corresponding to podosome-like sites of actin attachment. Our analysis of a loss-of-function allele of pxl-1, ok1483, shows that loss of paxillin leads to early larval arrested animals with paralyzed pharyngeal muscles and eventual lethality, presumably due to an inability to feed. We rescued the mutant phenotype by expressing paxillin solely in the pharynx and found that these animals survived and are essentially wild type in movement and body wall muscle structure. This indicates a differential requirement for paxillin in these two types of muscle. In pharyngeal muscle it is essential for contraction, whereas in body wall muscle it is dispensable for filament assembly, sarcomere stability, and ultimately movement.

scholarly journals Sequence requirements for myosin gene expression and regulation in Caenorhabditis elegans.

Genetics ◽  
1993 ◽  
Vol 135 (2) ◽  
pp. 385-404 ◽  
Author(s):  
P G Okkema ◽  
S W Harrison ◽  
V Plunger ◽  
A Aryana ◽  
A Fire
Keyword(s):  
Gene Expression ◽  
Caenorhabditis Elegans ◽  
Regulatory Element ◽  
Myosin Heavy Chain Isoforms ◽  
Gene Promoters ◽  
Coding Region ◽  
Muscle Type ◽  
Tissue Specific ◽  
Pharyngeal Muscles ◽  
Sequence Requirements

Abstract Four Caenorhabditis elegans genes encode muscle-type specific myosin heavy chain isoforms: myo-1 and myo-2 are expressed in the pharyngeal muscles; unc-54 and myo-3 are expressed in body wall muscles. We have used transformation-rescue and lacZ fusion assays to determine sequence requirements for regulated myosin gene expression during development. Multiple tissue-specific activation elements are present for all four genes. For each of the four genes, sequences upstream of the coding region are tissue-specific promoters, as shown by their ability to drive expression of a reporter gene (lacZ) in the appropriate muscle type. Each gene contains at least one additional tissue-specific regulatory element, as defined by the ability to enhance expression of a heterologous promoter in the appropriate muscle type. In rescue experiments with unc-54, two further requirements apparently independent of tissue specificity were found: sequences within the 3' non-coding region are essential for activity while an intron near the 5' end augments expression levels. The general intron stimulation is apparently independent of intron sequence, indicating a mechanistic effect of splicing. To further characterize the myosin gene promoters and to examine the types of enhancer sequences in the genome, we have initiated a screen of C. elegans genomic DNA for fragments capable of enhancing the myo-2 promoter. The properties of enhancers recovered from this screen suggest that the promoter is limited to muscle cells in its ability to respond to enhancers.

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