The orphan COUP-TF nuclear receptors are markers for neurogenesis from cnidarians to vertebrates.
In bilaterians, COUP-TF nuclear receptors participate in neurogenesis and/or CNS patterning. In hydra, the nervous system is formed of sensory mechanoreceptor cells (nematocytes) and neuronal cells, both lineages deriving from a common stem cell. The hydra COUP-TF gene, hyCOUP-TF, which encodes highly conserved DNA-binding and ligand-binding domains, belongs to the monophyletic COUP-TFs orphan receptor family (NR2F). In adult polyps, hyCOUP-TF is expressed in nematoblasts and a subset of neuronal cells. Comparative BrDU labeling analyses performed on cells expressing either hyCOUP-TF or the paired-like gene prdl-b showed that prdl-b expression corresponded to early stages of proliferation, while hyCOUP-TF was detected slightly later. HyCOUP-TF and prdl-b expressing cells disappeared in sf-1 mutants becoming "nerve-free". Moreover hyCOUP-TF and prdl-b expression was excluded from regions undergoing developmental processes. These data suggest that hyCOUP-TF and prdl-b belong to a genetic network that appeared together with neurogenesis during early metazoan evolution. The hyCOUP-TF protein specifically bound onto the evolutionarily conserved DR1 and DR5 response elements, and repressed transactivation induced by RAR:RXR nuclear receptors in a dose-dependent manner when expressed in mammalian cells. Hence, a cnidarian transcription factor can be active in vertebrate cells, implying that functional interactions between COUP-TF and other nuclear receptors were evolutionarily conserved.
Department of Zoology and Animal Biology, University of Geneva, Sciences III, CH-1211 Geneva 4, Switzerland.
Dominique
D
Gauchat
Hector
H
Escriva
Marijana
M
Miljkovic-Licina
Simona
S
Chera
Marie-Claire
MC
Langlois
Agnès
A
Begue
Vincent
V
Laudet
Brigitte
B
Galliot
D000595:Amino Acid Sequence; D000818:Animals; D005075:Biological Evolution; D015415:Biomarkers / Q000378:metabolism; D051836:COUP Transcription Factors; D003063:Cnidaria / Q000378:metabolism*; D017124:Conserved Sequence; D004268:DNA-Binding Proteins / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D018398:Homeodomain Proteins / Q000378:metabolism; D006829:Hydra / Q000378:metabolism; D008969:Molecular Sequence Data; D009474:Neurons / Q000378:metabolism; D010802:Phylogeny; D020033:Protein Isoforms / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D011987:Receptors, Steroid / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D016415:Sequence Alignment; D013234:Stem Cells / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*
D015415:Biomarkers; D051836:COUP Transcription Factors; D004268:DNA-Binding Proteins; D018398:Homeodomain Proteins; C112762:Prdl-b protein, Hydra attenuata; D020033:Protein Isoforms; D011987:Receptors, Steroid; D014157:Transcription Factors