P68, a DEAD-Box RNA helicase, is expressed in chordate embryo neural and mesodermal tissues

The p68 DEAD-box RNA helicases have been identified in diverse organisms, i ncluding yeast, invertebrates, and mammals. DEAD-box RNA helicases are thou ght to unwind duplexed RNAs, and the p68 family may participate in initiati ng nucleolar assembly. Recent evidence also suggests that they are developm entally regulated in chordate embryos, bobcat, a newly described member of this gene family, has been found in eggs and developing embryos of the asci dian urochordate, Molgula oculata. Antisense RNA experiments have implicate d this gene in establishing basic chordate features, including the notochor d and neural tube in ascidians (Swalla et al. 1999). We have isolated p68 h omologs from chick and Xenopus in order to investigate their possible role in vertebrate development. We show that embryonic expression of p68 in chic k, frog, and ascidian embryos is high in the developing brain and spinal co rd as well as in the sensory vesicles. In frog embryos, p68 expression also marks the streams of migrating cranial neural crest cells throughout neura l tube development and in tailbud stages, but neural crest expression is fa int in chick embryos. Ascidian embryos also show mesodermal p68 expression during gastrulation and neurulation, and we document some p68 mesodermal ex pression in both chick and frog. Thus, as shown in these studies, p68 is ex pressed in early neural development and in various mesodermal tissues in a variety of chordate embryos, including chick, frog, and ascidian. Further f unctional experiments will be necessary to understand the role(s) p68 may p lay in vertebrate development. J. Exp. Zool. (Mol. Dev. Evol.) 288:193-204, 2000. (C) 2000 Wiley-Liss, Inc.