A marsupial, Trichosurus vulpecula, DDX4/VASAGene (TvDDX4) of the DEAD box protein family: molecular conservation and germline expression.

The DDX4/VASA gene plays an important role in germ cell development in animals. We cloned and characterized a marsupial DDX4/VASA homolog (TvDDX4, 2,769 bps) from the possum and examined its expression in adult tissues at mRNA and protein levels. The isolated cDNA had a deduced 704 amino acid residues with significant homology to DDX4 from other animals, including mouse (86%) and human (87%). The DDX4 transcript was detected in the ovary and testis, and was undetectable in somatic tissues. The recombinant possum DDX4 protein (TvDDX4) was successfully produced in a bacterial expression system and used in polyclonal antibody generation. The recombinant TvDDX4 was detected by antibody against human DDX4 and mouse antibody against TvDDX4, but native possum TvDDX4 was only recognized by the possum antibody in the ovary and testis. Our results suggest a structural and functional conservation of DDX4 in marsupials and in mammals in the therian branches.