Muscle and nerve-specific regulation of a novel NK-2 class homeodomain factor in Caenorhabditis elegans.
We have identified a new Caenorhabditis elegans NK-2 class homeobox gene, designated ceh-24. Distinct cis-acting elements generate a complex neuronal and mesodermal expression pattern. A promoter-proximal enhancer mediates expression in a single pharyngeal muscle, the donut-shaped m8 cell at the posterior end of the pharynx. A second mesodermal enhancer is active in a set of eight nonstriated vulval muscles used in egg laying. Activation in the egg laying muscles requires an 'NdE-box' consensus motif (CATATG) which is related to, but distinct from, the standard E-box motif bound by the MyoD family of transcriptional activators. Ectodermal expression of ceh-24 is limited to a subset of sublateral motor neurons in the head of the animal; this activity requires a cis-acting activator element that is distinct from the control elements for pharyngeal and vulval muscle expression. Activation of ceh-24 in each of the three cell types coincides with the onset of differentiation. Using a set of transposon-induced null mutations, we show that ceh-24 is not essential for the formation of any of these cells. Although ceh-24 mutants have no evident defects under laboratory conditions, the pattern of ceh-24 activity is apparently important for Rhabditid nematodes: the related species C. briggsae contains a close homologue of C. elegans ceh-24 including a highly conserved and functionally equivalent set of cis-acting control signals.
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Carnegie Institution of Washington, Department of Embryology, Baltimore, MD 21210, USA.
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D000595:Amino Acid Sequence; D000818:Animals; D030801:Animals, Genetically Modified; D001483:Base Sequence; D017173:Caenorhabditis elegans / Q000235:genetics*; D029742:Caenorhabditis elegans Proteins; D004742:Enhancer Elements, Genetic / Q000235:genetics; D005260:Female; D018507:Gene Expression Regulation, Developmental / Q000235:genetics*; D017238:Genes, Helminth / Q000235:genetics; D005801:Genes, Homeobox / Q000235:genetics*; D006257:Head; D018398:Homeodomain Proteins / Q000235:genetics* / Q000502:physiology; D008969:Molecular Sequence Data; D009046:Motor Neurons / Q000737:chemistry; D009132:Muscles / Q000737:chemistry; D010609:Pharyngeal Muscles / Q000737:chemistry; D010641:Phenotype; D011401:Promoter Regions, Genetic / Q000235:genetics; D012333:RNA, Messenger / Q000032:analysis; D017384:Sequence Deletion; D017386:Sequence Homology, Amino Acid; D014844:Vulva / Q000737:chemistry
D029742:Caenorhabditis elegans Proteins; C111093:Ceh-24 protein, C elegans; D018398:Homeodomain Proteins; D012333:RNA, Messenger