title: Overlapping roles of two Hox genes and the exd ortholog ceh-20 in diversification of the C. elegans postembryonic mesoderm.
abstract: Members of the Hox family of homeoproteins and their cofactors play a central role in pattern formation of all germ layers. During postembryonic development of C. elegans, non-gonadal mesoderm arises from a single mesoblast cell M. Starting in the first larval stage, M divides to produce 14 striated muscles, 16 non-striated muscles, and two non-muscle cells (coelomocytes). We investigated the role of the C. elegans Hox cluster and of the exd ortholog ceh-20 in patterning of the postembryonic mesoderm. By examining the M lineage and its differentiation products in different Hox mutant combinations, we found an essential but overlapping role for two of the Hox cluster genes, lin-39 and mab-5, in diversification of the postembryonic mesoderm. This role of the two Hox gene products required the CEH-20 cofactor. One target of these two Hox genes is the C. elegans twist ortholog hlh-8. Using both in vitro and in vivo assays, we demonstrated that twist is a direct target of Hox activation. We present evidence from mutant phenotypes that twist is not the only target for Hox genes in the M lineage: in particular we show that lin-39 mab-5 double mutants exhibit a more severe M lineage defect than the hlh-8 null mutant.
authors.affiliation: Carnegie Institution of Washington, Department of Embryology, Baltimore, MD 21210, USA.
authors.forename: J
authors.initials: J
authors.lastname: Liu
authors.forename: A
authors.initials: A
authors.lastname: Fire
mesh_terms: D000818:Animals; D001665:Binding Sites; D017173:Caenorhabditis elegans / Q000196:embryology / Q000502:physiology*; D029742:Caenorhabditis elegans Proteins; D029721:Drosophila Proteins; D015801:Helminth Proteins / Q000235:genetics*; D018398:Homeodomain Proteins / Q000235:genetics*; D008648:Mesoderm / Q000502:physiology*; D009687:Nuclear Proteins / Q000235:genetics; D011401:Promoter Regions, Genetic; D014157:Transcription Factors / Q000235:genetics*; D051879:Twist-Related Protein 1
chemical_list: D029742:Caenorhabditis elegans Proteins; D029721:Drosophila Proteins; C497752:HLH-8 protein, C elegans; D015801:Helminth Proteins; D018398:Homeodomain Proteins; C081538:Mab-5 protein, C elegans; D009687:Nuclear Proteins; D014157:Transcription Factors; D051879:Twist-Related Protein 1; C418523:ceh-20 protein, C elegans; C083405:exd protein, Drosophila; C108673:lin-39 protein, C elegans