Evolution of sex chromosomes and sex determination of the medaka

青蒿虫(Oryzias Latipe)被用作研究性染色体和性别决定的实验动物。这类研究具有许多优势：物种内遗传多样性大、近交系、野生种群、密切相关的野生物种等。为了定位克隆性别决定基因，我们产生了一个Y同源菌株，以突出两个近交系X和Y染色体之间的遗传差异。在HD-RR(南方群体)的遗传背景上，该同基因株具有一个源于HNI(北方群体)Y染色体的性别决定区域。利用该菌株构建了性染色体遗传图谱和BAC文库。通过对一例同源XY女性的缺失分析，发现了一种Y特有的DM结构域基因DMY。来自野生种群的这种基因功能突变的丧失导致了雌性发育。携带DMY的117kb的基因组片段足以诱导出不同的…更多的辨别和随后的男性发展。这些结果表明，DMY是青竹的性别决定基因。这使DMY成为在非哺乳动物脊椎动物中发现的第一个性别决定基因。到目前为止，已鉴定出14种稻属植物。曲叶野生稻和吕宋野生稻是宽叶野生稻的姐妹种对。虽然这两个物种都有雄性-异性配子(XX-XY)系统，但DMY只在曲纹东方田鼠中检测到。我们鉴定了几个与吕宋岛野生稻性别相关的EST标记。这些EST的遗传图谱显示，吕宋岛野生稻的性染色体与宽叶野生稻的常染色体(连锁群12)同源。这一结果表明，吕宋稻瘟病菌具有来自DMY的另一个性别决定基因。此外，还在一种水稻中发现了雌性异性配偶制(ZZ-ZW系统)。性染色体和性别决定系统的多样性表明，不同的基因可能是稻属鱼类性别决定的主要基因，Medakas可以作为脊椎动物性染色体进化和性别决定研究的模式系统。较少

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