We have isolated a cDNA of the DEAD protein family from a Xenopus ovary cDNA library. Northern hybridization revealed that the mRNA corresponding to the cDNA [XVLG1 (Xenopus vasa-like gene)] was specifically expressed in adult testis and ovary. The deduced amino acid sequence of XVLG1 was relatively homologous to that of Drosophila vasa. XVLG1 protein was found to be expressed exclusively in adult testis and ovary by immunoblotting with a monoclonal antibody against XVLG1 protein. Immunocytological study showed that XVLG1 protein was expressed in oogonia, oocytes, spermatogonia, spermatocytes, and also in primordial germ cells in stage 46 tadpoles. The monoclonal antibody used in this study specifically stains germ line cells and is useful both as a germ cell lineage marker and in biochemical studies of germ cells.