Meeting Abstract
P3.109 Saturday, Jan. 5 RETINOIC ACID AND NITRIC OXIDE DIFFERENTIALLY INDUCE NEURONAL SPECIFICATION IN THE CNIDARIAN RENILLA KOELLIKERI ESTEPHAN, D*; ANCTIL, M; Universit� de Montr�al, Canada djoyce_este@hotmail.com
Retinoic acid (RA) and nitric oxide (NO) are reported to induce neurite outgrowth in both vertebrates and invertebrates. Retinoic acid receptors appear to be present in cnidarians and NO plays various physiological roles in several cnidarians, but there is as yet no evidence that these agents have a role in neural development in this basal metazoan phylum. We used primary cultures of cells from the sea pansy Renilla koellikeri to investigate potential effects of these agents on cnidarian cell differentiation. We found that both 9-cis and all-trans RA induced cell proliferation in dose- and time-dependent manners in dishes coated with polylysine from the start of culture. Cells in cultures first exposed to RA in dishes devoid of polylysine were observed to differentiate into epithelial cells, while some dedifferentiated cells expressed the ubiquitous neuropeptide Antho-RFamide, a neuronal marker in the sea pansy. NO induced extensive neurite outgrowth in polylysine-coated culture dishes. No other cell type underwent differentiation in the presence of NO, and the density of dedifferentiated cells was reduced. The neurites of the differentiating neurons appeared to intertwine and form a loose nerve net. These observations suggest that (1) RA, but not NO, has mitogenic activity, (2) both RA and NO are differentially involved in nerve cell specification in the sea pansy, and (3) the type of action, mitogenesis or cell differentiation (epithelial or neural), varies according to the state of cell adhesion to substrate during first exposure to RA. As both molecular and paleontological evidence place pennatulaceans such as the sea pansy closest to the eumetazoan ancestor, our results suggest that the morphogenetic role of RA and NO is rooted in the common ancestor of all metazoans. (Funded by Discovery Grant 6447-06 from NSERC of Canada)
