title: Cloning and characterization of a rice field eel vasa-like gene cDNA and its expression in gonads during natural sex transformation.
abstract: The vasa (vas)-related gene encodes an RNA helicase protein member of the DEAD-box family and plays key roles in germ-cell formation in higher metazoans. Using degenerate PCR and RACE, we cloned the vasa gene of the rice field eel (Monopterus albus), which is homologous to the Drosophila vasa gene. We named it ma-vas (Monopterus albus vas). Ma-vas encodes a protein of 618 amino acids, which contains all of the known characteristics of vasa homologs. RT-PCR analysis revealed that ma-vas was exclusively expressed in the gonads of the female, intersex, and male. During gonadal natural sex reversal, ma-vas is expressed in oocytes at all stages of oogenesis, in degenerating oocytes of ovotestis, and in spermatogonia and spermatocytes at early stages. The vasa positive signal was also observed in the peripheral layer of late ovary. It was not found, however, in that layer of the testis. Alkaline phosphatase (AKP) staining on the ovary and testis also indicated that some cells had differentiational potential in the peripheral layer of the ovary, suggesting that spermatogonia might arise from cells with AKP and vasa-positive staining in the peripheral layer of the female gonad.
authors.affiliation: Laboratory of Molecular Genetics and Developmental Biology, College of Life Science, Wuhan University, Wuhan, Hubei 430072, P. R. China.
authors.forename: Ding
authors.initials: D
authors.lastname: Ye
authors.forename: Daoyuan
authors.initials: D
authors.lastname: Lv
authors.forename: Ping
authors.initials: P
authors.lastname: Song
authors.forename: Maoyu
authors.initials: M
authors.lastname: Peng
authors.forename: Yungui
authors.initials: Y
authors.lastname: Chen
authors.forename: Ming
authors.initials: M
authors.lastname: Guo
authors.forename: Qiwen
authors.initials: Q
authors.lastname: Yang
authors.forename: Yinchang
authors.initials: Y
authors.lastname: Hu
mesh_terms: D000469:Alkaline Phosphatase / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D003001:Cloning, Molecular; D053487:DEAD-box RNA Helicases / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D018076:DNA, Complementary / Q000235:genetics* / Q000302:isolation & purification; D005260:Female; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation; D006066:Gonads / Q000378:metabolism*; D057850:Hermaphroditic Organisms; D008297:Male; D008969:Molecular Sequence Data; D010053:Ovary / Q000166:cytology; D010802:Phylogeny; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D016415:Sequence Alignment; D019849:Sex Determination Processes; D023701:Smegmamorpha / Q000235:genetics*; D013093:Spermatogonia / Q000378:metabolism
chemical_list: D018076:DNA, Complementary; D012333:RNA, Messenger; D000469:Alkaline Phosphatase; D053487:DEAD-box RNA Helicases