Analysis Of Gene Expression Associated With Reproductive Regulation In Male Rattus Norvegicus From Harbin And Zhanjiang

Norway rat(Rattus norvegicus) is a widely distributed pest rodent in the world. The Norway rats in Harbin and Zhangjiang City in China are two different subspecies. Previous studies by our laboratory suggest that the reproductive organs of Rattus norvegicus were inhibited during autumn and winter in Harbin, while not in Zhanjiang, furthermore, and the testis index of rats in Harbin were significantly positively correlated with the day length, while in Zhangjiang the correlation is not significant. Thus, we presumed the diffierent reproductive characteristics of the two subspecies are associated with the regulation of photoperiod responses. In this study, we collected samples from Harbin and Zhanjiang in the spring and autumn of 2013 and 2014. We analyzed the genes expression including the photoperiodism genes(Dio2, Dio3), seasonal-reproduction-related genes on HPG axis(GnRH, Kiss-1, RFRP-3), and testicular meiosis and cell cycle marker gens(Stra8, GnRHR) by real-time quantitative PCR. The main results are as follows:(1) We Cloned partial cDNAs of Dio2(650bp), Dio3(1047bp), GnRH(336bp), RFRP-3(349bp) and Kiss-1(282bp). The similarity between these sequences and the Norway rat reference sequence in GenBank is 100%.(2) The development of reproductive organ was significantly inhibited in autumn in Harbin, while not in Zhanjiang. The relative expression of GnRHR gene in testicular in autumn is significantly higher than in spring in Harbin, while not in Zhanjiang. We found a significant negative correlation between testicular GnRHR gene expression and testis index in autumn in Harbin, and it consistent with different devolpment patterns of two subspecies in autumn.(3) In both Zhanjiang and Harbin, we found a higher relative expression of Dio2 and GnRH and a lower expression of Dio3 in spring than in autumn. The expression of RFRP-3 and Kiss-1 genes are not significantly differentiated between in spring and in summer in both locations, however, the expression trend of the two genes from spring to autumn are different. The relative expression of Stra8 was significantly higher in autumn than in spring in 2013, and vice versa in 2014.All findings suggest the differences of reproduction between Harbin and Zhanjiang may be decided by genes in other regulatory pathways than the photoperiodism genes, although the expression of photoperiodism genes are sensitive to the photoperiod.