Regulation of ectodermal and excretory function by the C. elegans POU homeobox gene ceh-6.
Caenorhabditis elegans has three POU homeobox genes, unc-86, ceh-6 and ceh-18. ceh-6 is the ortholog of vertebrate Brn1, Brn2, SCIP/Oct6 and Brn4 and fly Cf1a/drifter/ventral veinless. Comparison of C. elegans and C. briggsae CEH-6 shows that it is highly conserved. C. elegans has only three POU homeobox genes, while Drosophila has five that fall into four families. Immunofluorescent detection of the CEH-6 protein reveals that it is expressed in particular head and ventral cord neurons, as well as in rectal epithelial cells, and in the excretory cell, which is required for osmoregulation. A deletion of the ceh-6 locus causes 80% embryonic lethality. During morphogenesis, embryos extrude cells in the rectal region of the tail or rupture, indicative of a defect in the rectal epithelial cells that express ceh-6. Those embryos that hatch are sick and develop vacuoles, a phenotype similar to that caused by laser ablation of the excretory cell. A GFP reporter construct expressed in the excretory cell reveals inappropriate canal structures in the ceh-6 null mutant. Members of the POU-III family are expressed in tissues involved in osmoregulation and secretion in a number of species. We propose that one evolutionary conserved function of the POU-III transcription factor class could be the regulation of genes that mediate secretion/osmoregulation.
Bürglin
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Department of Molecular Biology, Massachusetts General Hospital, Fruit Street, Boston, MA 02114, USA. Thomas.Burglin@biosci.ki.se
Ruvkun
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D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D000818:Animals; D030801:Animals, Genetically Modified; D017173:Caenorhabditis elegans / Q000033:anatomy & histology / Q000196:embryology / Q000235:genetics* / Q000502:physiology; D029742:Caenorhabditis elegans Proteins; D002874:Chromosome Mapping; D003001:Cloning, Molecular; D004847:Epithelial Cells / Q000378:metabolism; D017238:Genes, Helminth; D005801:Genes, Homeobox; D017930:Genes, Reporter; D018398:Homeodomain Proteins / Q000737:chemistry / Q000378:metabolism*; D008969:Molecular Sequence Data; D009474:Neurons / Q000378:metabolism*; D010641:Phenotype; D010802:Phylogeny; D016415:Sequence Alignment; D014882:Water-Electrolyte Balance
D029742:Caenorhabditis elegans Proteins; C423385:Ceh-6 protein, C elegans; D018398:Homeodomain Proteins