Molecular Evolution of Sex-determining Genes during Vertebrate Evolution

在XX/XY性别决定系统中，大多数哺乳动物的Y-连锁SRY基因和硬骨鱼青鳉的DMY/DMRT 1 Y基因被描述为启动精巢形成，导致雄性性发育的性别决定基因。相反，ZZ/ZW性别决定系统的分子机制仍然不清楚，因为没有性别决定基因被分离出来。南非爪蟾（Xenopus laevis）使用ZZ/ZW系统。DM结构域基因DMRT 1与多种脊椎动物睾丸的形成有关。然后，我们首先表明，X laevis DMRT 1在胚胎发生过程中表达，然后仅限于原始性腺。接下来，我们分离了一个W-连锁的DMRT 1，DM-W，在X laevis。虽然DM-W和DMRT 1的DNA结合结构域具有较高的序列同源性（89%），但它们的C-末端区域没有显著的序列相似性。DM-W和DMRT 1 mRNA表达模式的比较分析表明，DM-W主要表达在原始ZW性腺在早期性别决定。这些发现和转基因动物的表型分析表明，W连锁基因DM-W最有可能是X的性别（雌性）决定基因。光滑。

In the XX/XY sex-determining system, the Y-linked SRY genes of most mammals and the DMY/DMRT1Y gene of the teleost fish medaka have been characterized as sex-determining genes that initiate testis formation, leading to male sexual development. In contrast, the molecular mechanism for the ZZ/ZW sex-determining system remains unclear, because no sex-determining genes have been isolated. The South African clawed frog Xenopus laevis uses the ZZ/ZW system. A DM-domain gene DMRT1 is implicated in testis formation of various vertebrate species. Then, we first showed that X laevis DMRT1 is expressed during embryogenesis, and is then restricted to the primordial gonads. Next, we isolated a W-linked paralogue of DMRT1, DM-W, in X laevis. Although the DNA-binding domains of DM-W and DMRT1 shared high sequence identity (89%), their C-terminal regions had no significant sequence similarity. A comparative analysis of the DM-W and DMRT1 mRNA expression patterns showed that DM-W was expressed predominantly in the primordial ZW gonads during early sex determination. These findings and phenotypic analyses of transgenic animals carrying DM-W expression vectors indicated that the W-linked gene, DM-W, is most likely to be a sex (female)-determining gene in X. laevis.