Yokoyama Satoshi, Oshima Yuki, Tokita Junpei, Suda Mari, Shinozuka Takuma, Nakamura Masahisa
Department of Biology, Faculty of Education and Integrated Arts and Sciences, Waseda University, Tokyo, Japan.
J Exp Zool A Ecol Genet Physiol. 2009 Dec 1;311(10):796-812. doi: 10.1002/jez.568.
The androgen receptor(AR) gene is located on the Z and W sex chromosomes in the frog Rana rugosa, designated Z- and W-AR, respectively. Among various tissues of an adult frog, AR expression levels were highest in the testis and brain. In the testis, AR was expressed in germ cells. AR expression occured in developing embryos from stage 21 and was very high in the gonad of a male tadpole before the onset of sex determination. When Z- and W-AR were expressed in Xenopus A6 cells, they activated androgen-dependent transcription of a luciferase reporter gene. By contrast, estrogen receptor (ER) alpha and beta showed no sexually dimorphic expression during sex determination, but their expressions became much higher in the gonad of a female tadpole after sex determination. In addition, AR transcripts in the ZZ-tadpoles were twice as abundant as in the ZW genotype. In contrast, W-AR expression was extremely low although when W-AR was expressed in A6 cells, it activated transcription in the luciferase assay. In this regard it is worth noting that the promoter regions of Z- and W-AR are not identical. The results suggest that Z-AR plays an important role in the testis formation in a R. rugosa tadpole, whereas ERbeta is involved in ovary differentiation. Very low expression of W-AR may be due to its promoter region having mutations in key transcription factor binding sites, although these remain to be identified. Thus, it is proposed that AR could be a candidate for a male-determining gene in R. rugosa.
雄激素受体（AR）基因位于皱皮蛙的Z和W性染色体上，分别命名为Z-AR和W-AR。在成年蛙的各种组织中，AR表达水平在睾丸和大脑中最高。在睾丸中，AR在生殖细胞中表达。AR表达在第21阶段的发育胚胎中出现，并且在性别决定开始前雄性蝌蚪的性腺中非常高。当Z-AR和W-AR在非洲爪蟾A6细胞中表达时，它们激活了荧光素酶报告基因的雄激素依赖性转录。相比之下，雌激素受体（ER）α和β在性别决定期间没有性二态性表达，但在性别决定后雌性蝌蚪的性腺中它们的表达变得高得多。此外，ZZ蝌蚪中的AR转录本比ZW基因型中的丰富两倍。相比之下，W-AR表达极低，尽管当W-AR在A6细胞中表达时，它在荧光素酶测定中激活转录。在这方面，值得注意的是Z-AR和W-AR的启动子区域不相同。结果表明，Z-AR在皱皮蛙蝌蚪的睾丸形成中起重要作用，而ERβ参与卵巢分化。W-AR的极低表达可能是由于其启动子区域在关键转录因子结合位点发生了突变，尽管这些位点仍有待确定。因此，有人提出AR可能是皱皮蛙雄性决定基因的候选者。
