title: A ZZ/ZW-type sex determination in Xenopus laevis.
abstract: Genetic sex-determining systems in vertebrates include two basic types of heterogamety, which are represented by the XX/XY and ZZ/ZW types. Both types occur among amphibian species. Little is known, however, about the molecular mechanisms underlying amphibian sex determination. Recently, a W-linked gene, DM-W, was isolated as a paralog of DMRT1 in the African clawed frog Xenopus laevis, which has a female heterogametic ZZ/ZW-type sex-determining system. The DNA-binding domain of DM-W shows high sequence identity with that of DMRT1, but DM-W does not contain a domain with homology to DMRT1's transactivation domain. Importantly, phenotypic analysis of transgenic individuals bearing a DM-W-expression or -knockdown vector strongly suggested that DM-W acts as a female sex-determining gene in this species. In this minireview, we briefly describe the sex-determining systems in amphibians, discuss recent findings from the discovery of the DM-W gene in terms of its molecular evolution and its function in sex determination and ovary formation, and introduce a new model for the ZZ/ZW-type sex determination elicited by DM-W and DMRT1 in X. laevis. Finally, we discuss sex-determining systems and germ-cell development during vertebrate evolution, especially in view of a conserved role of DMRT1 in gonadal masculinization.
authors.affiliation: Department of Biosciences, Kitasato University, Minamiku, Sagamihara, Japan.
authors.forename: Shin
authors.initials: S
authors.lastname: Yoshimoto
authors.forename: Michihiko
authors.initials: M
authors.lastname: Ito
mesh_terms: D000818:Animals; D005260:Female; D005854:Germ Cells; D006066:Gonads / Q000196:embryology / Q000254:growth & development; D008297:Male; D012730:Sex Chromosomes / Q000235:genetics*; D019849:Sex Determination Processes; D012733:Sex Differentiation; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D029867:Xenopus Proteins / Q000235:genetics / Q000378:metabolism; D014982:Xenopus laevis / Q000502:physiology*
chemical_list: C110547:DMRT1 protein; D014157:Transcription Factors; D029867:Xenopus Proteins