The stem cells of planarians, known as neoblasts, can give rise to all cell types in planarians. Neoblasts can be identified by electron microscopy as cells with electron-dense chromatoid bodies, which are large RNP (ribonucleoprotein) complexes, in their cytoplasm. However, the components and function of chromatoid bodies are still relatively unknown. Here we identified a DEAD box RNA helicase gene of the RCK/p54/Me31B family from a planarian EST database and showed the localization of its product in chromatoid bodies by immunoelectron microscopy. We named this gene Djcbc-1 (Dugesia japonica chromatoid body component 1). Djcbc-1 was also strongly expressed in the brain and in the germline stem cells of sexualized planarians. We observed chromatoid body-like electron-dense bodies in brain neurons, where DjCBC-1 was also expressed. These observations suggest that common molecular components of RNP complexes may be involved in the regulation of somatic and germline stem cells, and neurons in planarians. Departmental Dynamics 236:3436–3450, 2007. © 2007 Wiley-Liss, Inc.