Wu Guan-Chung, Li Hau-Wen, Huang Chih-Hsiang, Lin Hong-Jia, Lin Chien-Ju, Chang Ching-Fong
Department of Aquaculture, National Taiwan Ocean University, Keelung, Taiwan Center of Excellence for the Oceans, National Taiwan Ocean University, Keelung, Taiwan
Department of Aquaculture, National Taiwan Ocean University, Keelung, Taiwan.
Biol Reprod. 2016 Jun;94(6):132. doi: 10.1095/biolreprod.115.137463. Epub 2016 Apr 20.
In most hermaphroditic fish, the sexual phase of the gonad responds to external stimuli so that only one sex remains functional while the other sex becomes dormant. However, protandrous black porgy are male during their first two reproductive cycles. Estradiol (E2)-induced female growth results in a transient and immature female, and the sexual phase reverts from female to male after E2 is withdrawn. Conversely, excising the testis results in a precocious female when performed during the second reproductive cycle. We used these characteristics to study epigenetic modifications of cyp19a1a promoter in black porgy. Our results showed that higher levels of gonadotropins receptors were observed in testis than in ovary during the alteration of sexual phase from induced femaleness to maleness, and hCG treatment did not stimulate ovarian gene expression in male (1-yr-old maleness) and female phase (testis excision-induced femaleness) fish. The cyp19a1a promoter exhibited tissue- and lineage-specific methylation patterns. The follicle cells in the ovary had a hypomethylated (0%-20%) cyp19a1a promoter region. In the ovary, the first sign of female phase decision was decreased methylation levels and increased numbers of hypomethylated clones of cyp19a1a promoter during the natural sex change process. Similar methylation patterns were observed in the testis-removed ovary 1 mo after surgery, with no histological difference between the sham and the testis-removed fish. Conversely, there was no increase in methylation levels of cyp19a1a promoter in E2-fed fish. These results suggest that in the digonic gonad of black porgy, the testis is the primary tissue that affects epigenetics of the ovary.
在大多数雌雄同体鱼类中，性腺的性阶段会对外界刺激做出反应，从而只有一种性别保持功能，而另一种性别则进入休眠状态。然而，先雄后雌的黑鲷在其前两个繁殖周期中是雄性。雌二醇（E2）诱导的雌性生长会产生一个短暂且不成熟的雌性，在撤去E2后，性阶段会从雌性恢复为雄性。相反，在第二个繁殖周期进行睾丸切除会导致雌性早熟。我们利用这些特征研究了黑鲷中cyp19a1a启动子的表观遗传修饰。我们的结果表明，在性阶段从诱导雌性转变为雄性的过程中，睾丸中促性腺激素受体的水平高于卵巢，并且hCG处理不会刺激雄性（1岁雄性）和雌性阶段（睾丸切除诱导的雌性）鱼类的卵巢基因表达。cyp19a1a启动子表现出组织和谱系特异性的甲基化模式。卵巢中的卵泡细胞具有低甲基化（0%-20%）的cyp19a1a启动子区域。在卵巢中，在自然性转变过程中，雌性阶段决定的第一个迹象是cyp19a1a启动子的甲基化水平降低和低甲基化克隆数量增加。在手术后1个月的睾丸切除卵巢中观察到类似的甲基化模式，假手术组和睾丸切除组鱼之间没有组织学差异。相反，在E2喂养的鱼中，cyp19a1a启动子的甲基化水平没有增加。这些结果表明，在黑鲷的两性性腺中，睾丸是影响卵巢表观遗传学的主要组织。
