title: Vasa identifies germ cells and critical stages of oogenesis in the Asian seabass.
abstract: Germ cells produce sperm and eggs for reproduction and fertility. The Asian seabass (Lates calcarifer), a protandrous marine fish, undergoes male-female sex reversal and thus offers an excellent model to study the role of germ cells in sex differentiation and sex reversal. Here we report the cloning and expression of vasa as a first germ cell marker in this organism. A 2241-bp cDNA was cloned by PCR using degenerate primers of conserved sequences and gene-specific primers. This cDNA contains a polyadenylation signal and a full open reading frame for 645 amino acid residues, which was designated as Lcvasa for the seabass vasa, as its predicted protein is homologous to Vasa proteins. The Lcvasa RNA is maternally supplied and specific to gonads in adulthood. By chromogenic and fluorescent in situ hybridization we revealed germ cell-specific Lcvasa expression in both the testis and ovary. Importantly, Lcvasa shows dynamic patterns of temporospatial expression and subcellular distribution during gametogenesis. At different stages of oogenesis, for example, Lcvasa undergoes nuclear-cytoplasmic redistribution and becomes concentrated preferentially in the Balbiani body of stage-II~III oocytes. Thus, the vasa RNA identifies both female and male germ cells in the Asian seabass, and its expression and distribution delineate critical stages of gametogenesis.
authors.affiliation: Department of Biological Sciences, National University of Singapore, 14 Science Drive 4, Singapore 117543.
authors.forename: Hongyan
authors.initials: H
authors.lastname: Xu
authors.affiliation: Department of Biological Sciences, National University of Singapore, 14 Science Drive 4, Singapore 117543.
authors.forename: Menghuat
authors.initials: M
authors.lastname: Lim
authors.affiliation: Department of Biological Sciences, National University of Singapore, 14 Science Drive 4, Singapore 117543.
authors.forename: Manali
authors.initials: M
authors.lastname: Dwarakanath
authors.affiliation: Department of Biological Sciences, National University of Singapore, 14 Science Drive 4, Singapore 117543.
authors.forename: Yunhan
authors.initials: Y
authors.lastname: Hong
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D029941:Fish Proteins / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D005399:Fishes / Q000235:genetics / Q000502:physiology*; D005854:Germ Cells / Q000502:physiology*; D008297:Male; D008969:Molecular Sequence Data; D009865:Oocytes / Q000378:metabolism; D009866:Oogenesis; D010802:Phylogeny; D016415:Sequence Alignment; D019849:Sex Determination Processes; D013737:Testis / Q000378:metabolism
chemical_list: D029941:Fish Proteins
keywords: Asian seabass; gametogenesis; gene expression; germ cell; oogenesis; sex reversal; vasa.