Molecular characterization and expression pattern of a germ cell marker gene dnd in gibel carp (Carassius gibelio)

As a germ cell marker gene, Dead end (dnd) has been identified and characterized in many vertebrates. Recently, we created a complete germ cell-depleted gonad model by the dnd-specific morpholino-mediated knockdown approach, and revealed sex-biased gene expression alteration through utilizing unisexual gynogenetic superiority in polyploid gibel carp. However, dnd and its expression pattern are still unclear in the gibel carp. In this study, we further analyzed molecular characterization of gibel carp dnd and its dynamic expression pattern during gametogenesis and embryogenesis. Similar to other homologs in vertebrates, gibel carp dnd contains a conserved RRM motif and five other motifs, and is highly evolutionary conserved in genomic organization and neighborhood gene synteny. RT-PCR and Western blot analyses showed its gonad-specific expression intensively in testis and ovary. Section in situ hybridization (SISH) and immunofluorescence localization revealed its dynamic expression pattern specific to oogenic cells and spermatogenetic cells during oogenesis and spermatogenesis. Moreover, its temporal and spatial distribution specific to PGCs were also demonstrated by RT-PCR and whole mount in situ hybridization (WISH) during embryogenesis. Therefore, gibel carp Dnd is a conserved germ cell marker during gametogenesis, and its maternal transcript is also a useful marker for tracing PGC specification and migration.