オス特有の行動には、脳で作られる女性ホルモンが必要～オスの脳でも大量の女性ホルモンが作られる意義が明らかに～

2026-01-13 東京大学

図1:脳で女性ホルモンを作れなくなったオスは、メスにあまり求愛しなくなる

<関連情報>

• https://www.a.u-tokyo.ac.jp/topics/topics_20260113-1.html
• https://elifesciences.org/articles/97106

脳由来のエストロゲンはメダカのアンドロゲン受容体シグナル伝達を増強することで雄特有の行動を促進する Brain-derived estrogens facilitate male-typical behaviors by potentiating androgen receptor signaling in medaka

Yuji Nishiike,Shizuku Maki,Daichi Miyazoe,Kiyoshi Nakasone,Yasuhiro Kamei,Takeshi Todo,Tomoko Ishikawa-Fujiwara,Kaoru Ohno,Takeshi Usami,Kataaki Okubo
eLife  Published:Jan 13, 2026
DOI:https://doi.org/10.7554/eLife.97106.4

Abstract

In rodents, estrogens aromatized from androgens in the brain are essential for the development of male-typical behaviors. In many other vertebrates, including humans and teleost fish, however, androgens facilitate these behaviors directly via the androgen receptor without aromatization into estrogens. Here, we report that mutagenesis-derived male medaka fish lacking Cyp19a1b (a subtype of aromatase predominantly expressed in the brain) exhibit severely impaired male-typical mating and aggression, despite elevated brain androgen levels. These phenotypes can be rescued by estrogen administration, indicating that brain-derived estrogens are pivotal for male-typical behaviors even in teleosts. Our results further suggest that these estrogens facilitate male-typical behaviors by potentiating androgen action in the brain via the direct stimulation of androgen receptor transcription. Taken together, these findings reveal a previously unappreciated mode of action of brain-derived estrogens in facilitating male-typical behaviors.