Submitted on June 7, 2006
Accepted on November 14, 2006
Differential response of type 2 deiodinase gene expression to photoperiod between photoperiodic Fischer 344 and nonphotoperiodic Wistar rats
Shinobu Yasuo1, Miwa Watanabe1, Masayuki Iigo2, Takahiro J. Nakamura1, Tsuyoshi Watanabe1, Tsuyoshi Takagi1, Hiroko Ono1, Shizufumi Ebihara1, and Takashi Yoshimura3*
1 Division of Biomodeling, Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya, Japan
2 Department of Applied Biological Chemistry, Faculty of Agriculture, Utsunomiya University, Japan
3 Division of Biomodeling, Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya, Japan; Institute for Advanced Research, Nagoya University, Nagoya, Japan
* To whom correspondence should be addressed. E-mail: takashiy{at}agr.nagoya-u.ac.jp.
The molecular basis of seasonal or nonseasonal breeding remains unknown. Although laboratory rats are generally regarded as photoperiod-insensitive species, the testicular weight of the Fischer 344 (F344) strain responds to the photoperiod. Recently, it was clarified that photoperiodic regulation of type 2 iodothyronine deiodinase (Dio2) in the mediobasal hypothalamus (MBH) is critical in the photoperiodic gonadal regulation. Strain-dependent differences in the photoperiod sensitivity may now provide the opportunity to address the regulatory mechanism of seasonality by studying Dio2 expression. Therefore, in the present study, we examined the effect of photoperiod on Dio2 expression in photoperiod-sensitive F344 and photoperiod-insensitive Wistar rats. A statistically significant difference was observed between short and long days in terms of the testicular weight and Dio2 expression in the F344 strain, while no difference was observed in the Wistar strain. These results suggest that differential responses of Dio2 gene to photoperiod may determine the strain-dependent differences in photoperiod sensitivity in laboratory rats.
