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Letters to Nature

Nature 426, 178-181 (13 November 2003) | doi:10.1038/nature02117; Received 14 July 2003; Accepted 25 September 2003

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Light-induced hormone conversion of T4 to T3 regulates photoperiodic response of gonads in birds

Takashi Yoshimura1, Shinobu Yasuo1, Miwa Watanabe1, Masayuki Iigo3, Takashi Yamamura1, Kanjun Hirunagi2 & Shizufumi Ebihara1

  1. Division of Biomodeling, Graduate School of Bioagricultural Sciences, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, 464-8601, Japan
  2. The Nagoya University Museum, Furo-cho, Chikusa-ku, Nagoya, 464-8601, Japan
  3. Department of Applied Biological Chemistry, Faculty of Agriculture, Utsunomiya University, Mine-Machi, Utsunomiya, Tochigi 321-8505, Japan

Correspondence to: Takashi Yoshimura1 Email: takashiy@agr.nagoya-u.ac.jp

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Reproduction of many temperate zone birds is under photoperiodic control. The Japanese quail is an excellent model for studying the mechanism of photoperiodic time measurement because of its distinct and marked response to changing photoperiods. Studies on this animal have suggested that the mediobasal hypothalamus (MBH) is an important centre controlling photoperiodic time measurement1, 2, 3, 4, 5, 6, 7, 8. Here we report that expression in the MBH of the gene encoding type 2 iodothyronine deiodinase (Dio2), which catalyses the intracellular deiodination of thyroxine (T4) prohormone to the active 3,5,3'-triiodothyronine (T3), is induced by light in Japanese quail. Intracerebroventricular administration of T3 mimics the photoperiodic response, whereas the Dio2 inhibitor iopanoic acid prevents gonadal growth. These findings demonstrate that light-induced Dio2 expression in the MBH may be involved in the photoperiodic response of gonads in Japanese quail.