CHARACTERIZATION OF PLATYHELMINTH POU DOMAIN GENES - UBIQUITOUS AND SPECIFIC ANTERIOR NERVE-CELL EXPRESSION OF DIFFERENT EPITOPES OF GTPOU-1

POU domain proteins are a large family of transcription factors that h ave been identified in a variety of metazoans, from freshwater sponges , planarians and nematodes to arthropods, echinoderms and vertebrates. Many of these proteins are implicated in the development and establis hment of the nervous system. In this paper we describe the identificat ion of the planarian genes GtPOU-1, GtPOU-3 and GtPOU-4. which belong to the subclasses III and IV of POU-domain genes. Their similarity wit h other members of the POU family is restricted to the POU and homeo d omains, plus some peptide sequences scattered in the linker and flanki ng regions. As with other subclass LII POU genes, GtPOU-1 is devoid of introns. Axial transcript distribution by RT-PCR and immunohistochemi cal assays, performed with a polyclonal antibody raised against the Gt POU-1 fusion protein, indicate that both the GtPOU-1 transcript and pr otein are continuously expressed along the antero-posterior axis. A mo noclonal antibody raised against the same fusion protein indicates tha t a GtPOU-1-specific epitope, probably obtained by post-translational modification, is present in neural cells from both the central and per ipheral nerve systems of the adult planarian's anterior third. Moreove r, the GtPOU-1-specific epitope shows a dynamic expression pattern dur ing regeneration, always marking the most anterior region of the plana rian nervous system. Both the rapid and general GtPOU-1-specific epito pe modification, during posterior regeneration, indicate that regenera tion is a global process involving all planarian regions, including th ose that are far from the wound, by a combination of morphallactic and epimorphic mechanisms. (C) 1998 Elsevier Science Ireland Ltd. All rig hts reserved.