Myosho Taijun, Takehana Yusuke, Hamaguchi Satoshi, Sakaizumi Mitsuru
Institute of Science and Technology, Niigata University, Niigata 950-2181, Japan
Laboratory of Bioresources, National Institute for Basic Biology, Okazaki 444-8585, Japan.
G3 (Bethesda). 2015 Oct 23;5(12):2685-91. doi: 10.1534/g3.115.021543.
Sex chromosomes and the sex-determining (SD) gene are variable in vertebrates. In particular, medaka fishes in the genus Oryzias show an extremely large diversity in sex chromosomes and the SD gene, providing a good model to study the evolutionary process by which they turnover. Here, we investigated the sex determination system and sex chromosomes in six celebensis group species. Our sex-linkage analysis demonstrated that all species had an XX-XY sex determination system, and that the Oryzias marmoratus and O. profundicola sex chromosomes were homologous to O. latipes linkage group (LG) 10, while those of the other four species, O. celebensis, O. matanensis, O. wolasi, and O. woworae, were homologous to O. latipes LG 24. The phylogenetic relationship suggested a turnover of the sex chromosomes from O. latipes LG 24 to LG 10 within this group. Six sex-linkage maps showed that the former two and the latter four species shared a common SD locus, respectively, suggesting that the LG 24 acquired the SD function in a common ancestor of the celebensis group, and that the LG 10 SD function appeared in a common ancestor of O. marmoratus and O. profundicola after the divergence of O. matanensis. Additionally, fine mapping and association analysis in the former two species revealed that Sox3 on the Y chromosome is a prime candidate for the SD gene, and that the Y-specific 430-bp insertion might be involved in its SD function.
性染色体和性别决定（SD）基因在脊椎动物中是可变的。特别是，青鳉属的青鳉鱼在性染色体和SD基因方面表现出极大的多样性，为研究它们更替的进化过程提供了一个很好的模型。在这里，我们研究了六种西里伯斯青鳉种群物种的性别决定系统和性染色体。我们的性连锁分析表明，所有物种都具有XX-XY性别决定系统，并且斑纹青鳉和深水青鳉的性染色体与青鳉的连锁群（LG）10同源，而其他四个物种，即西里伯斯青鳉、马坦青鳉、沃拉斯青鳉和沃沃拉青鳉的性染色体与青鳉的LG 24同源。系统发育关系表明，在这个种群中，性染色体从青鳉的LG 24转变为LG 10。六个性连锁图谱表明，前两个物种和后四个物种分别共享一个共同的SD位点，这表明LG 24在西里伯斯青鳉种群的共同祖先中获得了SD功能，并且LG 10的SD功能在马坦青鳉分化后出现在斑纹青鳉和深水青鳉的共同祖先中。此外，对前两个物种的精细定位和关联分析表明，Y染色体上的Sox3是SD基因的主要候选基因，并且Y特异性430bp插入可能参与其SD功能。
