Abstract: [Objective] To investigate the effects of 17α-methyltestosterone （MT） on relative expression of DNA methyltransferase （DNMT） genes in testis of Gobiocypris rarus. [Method] Male Gobiocypris rarus were treated with varied doses of MT （25, 50, and 100 ng / L）. On the 7^th, 14^th and 21^st day post MT exposure, ten fishes were randomly selected from each MT treatment group, respectively, and they were dissected to collect testis tissues. The total RNA in the obtained testis tissues was extracted by one-step Trizol method, and the relative expression of DNA methyltransferase genes （dnmts） was detected by real-time quantitative PCR （qRT-PCR）. [Result] On 7^th day post MT exposure, compared with control group, the relative expression of dnmt3 gene in testis tissues in 25 ng/L （P<0.05）, 50 ng/L （P<0.01）, and 100 ng/L （P<0.05） MT treatment groups was significantly or extremely significantly reduced; in the testis tissues of 25 ng/L and 50 ng/L MT treatment groups, the relative expression of dnmt5 gene fell significantly （P<0.05）; 50 ng/L MT treatment group had significantly （P<0.05） decreased relative expression of dnmt7 gene in the testis tissues. On 14^th day post MT exposure, compared with control group, the relative expression of dnmt3, dnmt5, dnmt6, and dnmt7 genes increased significantly （P<0.05） in 100 ng/L MT treatment group, and that of dnmt1 gene increased extremely significantly （P<0.01） in 50 ng/L MT treatment group. On 21^st day post MT exposure, compared with control group, 50 ng/L and 100 ng/L MT treatment groups had significantly （P<0.05） increased relative expression of dnmt1 gene, and 100 ng/L MT treatment group had extremely significantly （P<0.01） higher relative expression of dnmt8 gene. [Conclusion] MT can interfere with the mRNA expression of dmmts genes in testis of Gobiocypris rarus. Further studies are expected to focus on the effects of MT on enzymatic activity of DNA methyltransferases, as well as on whether MT affects spermatogenesis of Gobiocypris rarus by altering DNA methylation levels.

Key words: 17α-methyltestosterone, Gobiocypris rarus, testis, DNA methyltransferase gene