title: Molecular evolution of vertebrate sex-determining genes.
abstract: Y-linked Dmy (also called dmrt1bY) in the teleost fish medaka, W-linked Dm-W in the African clawed frog (Xenopus laevis), and Z-linked Dmrt1 in the chicken are all sex chromosome-linked Dmrt1 homologues required for sex determination. Dmy and Dm-W both are Dmrt1 palalogues evolved through Dmrt1 duplication, while chicken Dmrt1 is a Z-linked orthologue. The eutherian sex-determining gene, Sry, evolved from an allelic gene, Sox3. Here we analyzed the exon-intron structures of the Dmrt1 homologues of several vertebrate species through information from databases and by determining the transcription initiation sites in medaka, chicken, Xenopus, and mouse. Interestingly, medaka Dmrt1 and Dmy and Xenopus Dm-W and Dmrt1 have a noncoding-type first exon, while mouse and chicken Dmrt1 do not. We next compared the 5'-flanking sequences of the Dmrt1 noncoding and coding exons 1 of several vertebrate species and found conservation of the presumptive binding sites for some transcription factors. Importantly, based on the phylogenetic trees for Dmrt1 and Sox3 homologues, it was implied that the sex-determining gene Dmy, Dm-W, and Sry have a higher substitution rate than thier prototype genes. Finally, we discuss the evolutionary relationships between vertebrate sex chromosomes and the sex-determining genes Dmy/Dm-W and Sry, which evolved by neofunctionalization of Dmrt1 and Sox3, respectively, for sex determining function. We propose a coevolution model of sex determining gene and sex chromosome, in which undifferentiated sex chromosomes easily allow replacement of a sex-determining gene with another new one, while specialized sex chromosomes are restricted a particular sex-determining gene.
authors.affiliation: Department of Biosciences, School of Science, Kitasato University, 1-15-1 Kitasato, Minamiku, Sagamihara, Japan.
authors.forename: Shuuji
authors.initials: S
authors.lastname: Mawaribuchi
authors.forename: Shin
authors.initials: S
authors.lastname: Yoshimoto
authors.forename: Shuntaro
authors.initials: S
authors.lastname: Ohashi
authors.forename: Nobuhiko
authors.initials: N
authors.lastname: Takamatsu
authors.forename: Michihiko
authors.initials: M
authors.lastname: Ito
mesh_terms: D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D043171:Chromosomal Instability; D017124:Conserved Sequence; D030541:Databases, Genetic; D019143:Evolution, Molecular; D005091:Exons; D005260:Female; D024742:HMG-Box Domains; D007438:Introns; D008297:Male; D008957:Models, Genetic; D010802:Phylogeny; D011401:Promoter Regions, Genetic; D055747:SOX Transcription Factors / Q000235:genetics / Q000378:metabolism; D012730:Sex Chromosomes / Q000235:genetics* / Q000378:metabolism; D019849:Sex Determination Processes; D014157:Transcription Factors / Q000235:genetics* / Q000378:metabolism; D024363:Transcription Initiation Site; D014714:Vertebrates / Q000235:genetics*
chemical_list: C110547:DMRT1 protein; D055747:SOX Transcription Factors; D014157:Transcription Factors