Evolution of sex chromosomes and sex determination of the medaka

青鳉（Oryzias latipes）是研究性染色体和性别决定的实验动物。为了定位克隆性别决定基因，我们构建了一个Y同源株系，以突出两个自交系X和Y染色体之间的遗传差异。同源株系在Hd-rR（Southern population）的遗传背景上具有来自HNI（北方群体）Y染色体的性别决定区。利用该菌株，我们构建了性染色体遗传图谱和BAC文库。DMY是一个Y染色体特异性的DM结构域基因，通过对一个同系XY女性的缺失分析鉴定出来。来自野生种群的该基因的功能缺失突变导致雌性发育。携带DMY的117-腺苷酸酶基因组DNA片段足以诱导睾丸分化， 关于我们 以及随后的男性发育。这些结果表明，DMY基因是青鳉性别决定基因。这使得DMY成为第一个在非哺乳类脊椎动物中发现的性别决定基因。迄今为止，已鉴定出14种Oryzias。Oryzias curvinotus和O. luzonensis是O.拉丁人虽然这两个物种都有雄性异配子（XX-XY）性别决定系统，但DMY只在O。弯鼻龙我们鉴定了几个与O.吕宋。利用这些EST构建的遗传图谱显示，O. luzonensis与O.拉丁人这一结果表明O. luzonensis具有另一个来自DMY的性别决定基因。此外，在一种Oryzias中发现了雌性异配子体（ZZ-ZW系统）。性染色体和性别决定系统的多样性表明，不同基因可能是Oryzias鱼类性别决定的主导基因，青鳉可作为脊椎动物性染色体进化和性别决定研究的模式系统。少

The medaka (Oryzias latipes), has been used as an experimental animal to study sex chromosomes and sex determination. It has many advantages for this kind of research : a large genetic diversity within the species, inbred strains, wild populations, closely related wild species, and so on. To clone positionally the sex-determining gene, we generated a Y congenic strain to highlight the genetic differences between the X and Y chromosomes from two inbred strains. The congenic strain has a sex-determining region derived from the HNI (Northern population) Y chromosome on the genetic background of Hd-rR (Southern population). Using this strain, we constructed a genetic map of the sex chromosome and a BAC library. DMY, a Y specific DM-domain gene, was identified from a deletion analysis of a congenic XY female. Loss of function mutations of this gene derived from wild populations caused female development. A 117-kilobase genomic DNA fragment carrying DMY was sufficient to induce testis differ … More entiation and subsequent male development. These results demonstrated that DMY is the sex-determining gene of medaka. This makes DMY the first sex-determining gene found in non-mammalian vertebrates. Fourteen species of the genus Oryzias have been identified to date. Oryzias curvinotus and O. luzonensis are a sister species pair of O. latipes. Although both species have male-heterogametic (XX-XY) system of sex determination, DMY was detected only in O. curvinotus. We identified several EST markers that linked to the sex of O. luzonensis. A genetic map of these ESTs showed that the sex chromosome of O. luzonensis was homologous to an autosome (linkage group 12) of O. latipes. This result suggests that O. luzonensis has another sex-determining gene from DMY. Furthermore, female heterogamety (ZZ-ZW system) has been found in a species of Oryzias. Diversity of sex chromosomes and sex-determining system suggest that different genes might be the master sex-determining gene in Oryzias fishes, and that medakas can be a model system for the research on evolution of sex chromosomes and sex determination in vertebrates. Less