Cloning and characterization of Vasa gene expression pattern in adults of the Lusitanian toadfish Halobatrachus didactylus

The Vasa gene is essential for germ cell development in eukaryotes. It encodes a RNA helicase, a member of the DEAD box protein family. Using the RACE method, we cloned the Vasa cDNA of the Lusitanian toadfish Halobatrachus didactylus, and analyzed quantitative and qualitative Vasa expression and its protein immunolocalization. We reported a main product of about 2.4 kb which encodes a protein of 615 amino acids, but other minority Vasa products were also identified by RACE-PCR. This gene is predominantly expressed in the ovaries and testes, although some relatively low extragonadal expression levels have also been identified. In situ hybridization and immunolocalization analysis during gametogenesis in the testes showed that toadfish Vasa mRNA was detected in spermatogonia, spermatocytes and spermatids. However, in the ovaries, Vasa mRNA was detected in early vitellogenic oocytes and in more advanced vitel-logenic stages, showing a very weak signal in oogonia, whereas the Vasa protein was evidenced in the cytoplasm of oogonia and previtellogenic oocytes, becoming weaker as the vitellogenic and maturation processes progress. These results suggest that toadfish Vasa homologues can play an important role in gametogenesis and germ cell development, but it could also be functionally implicated in other processes that are not as well known. © The authors 2014.This work was financed by Proyecto de Excelencia (RNM-03074; Consejería de Inno- vación, Ciencia y Empresa, Junta de Andalucía, Spain). M.Ú-M. was supported by a CSIC JAE-Predoc fellowship.Peer Reviewe