Modulation of COUP-TF Expression in a Cnidarian by Ectopic Wnt Signalling and Allorecognition

COUP transcription factors are required for the regulation of gene expression underlying development, differentiation, and homeostasis. They have an evolutionarily conserved function, being a known marker for neurogenesis from cnidarians to vertebrates. A homologue of this gene was shown previously to be a neuronal and nematocyte differentiation marker in Hydra. However, COUP-TFs had not previously been studied in a colonial cnidarian.We cloned a COUP-TF homologue from the colonial marine cnidarian Hydractinia echinata. Expression of the gene was analysed during normal development, allorecognition events and ectopic Wnt activation, using in situ hybridisation and quantitative PCR. During normal Hydractinia development, the gene was first expressed in post-gastrula stages. It was undetectable in larvae, and its mRNA was present again in putative differentiating neurons and nematocytes in post-metamorphic stages. Global activation of canonical Wnt signalling in adult animals resulted in the upregulation of COUP-TF. We also monitored a strong COUP-TF upregulation in stolons undergoing allogeneic interactions. COUP-TF mRNA was most concentrated in the tissues that contacted allogeneic, non-self tissues, and decreased in a gradient away from the contact area. Interestingly, the gene was transiently upregulated during initial contact of self stolons, but dissipated rapidly following self recognition, while in non-self contacts high expression levels were maintained.We conclude that COUP-TF is likely involved in neuronal/nematocyte differentiation in a variety of contexts. This has now been shown to include allorecognition, where COUP-TF is thought to have been co-opted to mediate allorejection by recruiting stinging cells that are the effectors of cytotoxic rejection of allogeneic tissue. Our findings that Wnt activation upregulates COUP-TF expression suggests that Wnts' role in neuronal differentiation could be mediated through COUP-TF

PHOSPHORUS-CONTAINING N-METHYLENEAMINE TYPE COMPOUNDS - SYNTHESIS, STRUCTURE, AND REACTIVITY

GALLIOT C, CAMINADE AM, DAHAN F, MAJORAL JP, Schoeller W. PHOSPHORUS-CONTAINING N-METHYLENEAMINE TYPE COMPOUNDS - SYNTHESIS, STRUCTURE, AND REACTIVITY. INORGANIC CHEMISTRY. 1994;33(26):6351-6356.Addition of paraformaldehyde to phosphonodihydrazides PhP(X)(NCH3NH2)(2), 1a (X = S) or 1b (X = O), led to 1,2,4,5,3-perhydrotetrazaphosphorines 4a or 4b and then to stable phosphonodihydrazones PhP(X)(N(CH3)N=CH2)(2), 6a (X = S) or 6b (X = O). Similarly, addition of paraformaldehyde to the hexahydrazino cyclotriphosphazene N3P3(NCH3NH2)(6) afforded a tris(1,2,4,5,3-perhydrotetrazaphosphorine 12, which in turn is transformed to the stable hexakis(N-methyleneamine)cyclotriphosphazine 13 by addition of paraformaldehyde. The crystal and molecular structure of 13 was examined by single crystal X-ray diffraction. Treatment of 6a or 6b with the phosphanylium ion (iPr(2)N)(2)P+CF3SO3-, 15, gave a mixture of bicyclic phosphonium salts 17 and 18 or 19 and 20 respectively. A pyridinium salt 21 was prepared by reacting 6a with trifluoro acetic anhydride in the presence of pyridine. Interaction of the borenium salt (C5H9)(2)B+CF3SO3-, 22, with 6a led to the salt 23 [6a.2B(C5H9)(2).CF3SO3]

Increased Cell Proliferation and Mucocyte Density in the Sea Anemone Aiptasia pallida Recovering from Bleaching

Recovery of coral after bleaching episodes is a critical period for the health of the reef ecosystem. While events such as symbiont (genus Symbiodinium) shifting/shuffling or tissue apoptosis have been demonstrated to occur following bleaching, little is known concerning tissue recovery or cell proliferation. Here, we studied the sea anemone Aiptasia pallida exposed to a transient elevation of water temperature combined with high illumination (33°C and 1900 μmolphotons.m.s for 30h). Following such treatment bleached anemones showed a significant reduction of their Symbiodinium density. Cell proliferation in the ectodermis and gastrodermis was determined by assessing the densities of cells labeled with a thymidine analogue (EdU). Cell proliferation significantly increased during the first day following stress in both tissue types. This increased cell proliferation returned to pre-stress values after one week. Although cell proliferation was higher in the ectodermis in absence of stress, it was relatively more pronounced in the gastrodermis of stressed anemones. In addition, the ratio of ectodermal mucocytes significantly increased three weeks after induced stress. These results suggest that thermal/photic stress coupled with the loss of the symbionts is able to enhance cell proliferation in both gastrodermis and ectodermis of cnidarians. While new cells formed in the gastrodermis are likely to host new Symbiodinium, the fate of new cells in the ectodermis was only partially revealed. Some new ectodermal cells may, in part, contribute to the increased number of mucocytes which could eventually help strengthen the heterotrophic state until restoration of the symbiosis