Key Laboratory of Freshwater Fish Reproduction and Development (Ministry of Education), Key Laboratory of Aquatic Science of Chongqing, School of Life Sciences, Southwest University, Chongqing, China.
Key Laboratory of Freshwater Fish Reproduction and Development (Ministry of Education), Key Laboratory of Aquatic Science of Chongqing, School of Life Sciences, Southwest University, Chongqing, China.
Gen Comp Endocrinol. 2024 Jan 1;345:114395. doi: 10.1016/j.ygcen.2023.114395. Epub 2023 Oct 23.
The Nile tilapia (Oreochromis niloticus), with a system of XX/XY sex determination, is a worldwide farmed fish with a shorter sexual maturation time than that of most cultured fish. Tilapia show a spawning cycle of approximately 14 days and can be artificially propagated in the laboratory all year round to obtain genetically all female (XX) and all male (XY) fry. Its genome sequence has been opened, and a perfect gene editing platform has been established. With a moderate body size, it is convenient for taking enough blood to measure hormone level. In recent years, using tilapia as animal model, we have confirmed that estrogen is crucial for female development because 1) mutation of star2, cyp17a1 or cyp19a1a (encoding aromatase, the key enzyme for estrogen synthesis) results in sex reversal (SR) due to estrogen deficiency in XX tilapia, while mutation of star1, cyp11a1, cyp17a2, cyp19a1b or cyp11c1 affects fertility due to abnormal androgen, cortisol and DHP levels in XY tilapia; 2) when the estrogen receptors (esr2a/esr2b) are mutated, the sex is reversed from female to male, while when the androgen receptors are mutated, the sex cannot be reversed; 3) the differentiated ovary can be transdifferentiated into functional testis by inhibition of estrogen synthesis, and the differentiated testis can be transdifferentiated into ovary by simultaneous addition of exogenous estrogen and androgen synthase inhibitor; 4) loss of male pathway genes amhy, dmrt1, gsdf causes SR with upregulation of cyp19a1a in XY tilapia. Disruption of estrogen synthesis rescues the male to female SR of amhy and gsdf but not dmrt1 mutants; 5) mutation of female pathway genes foxl2 and sf-1 causes SR with downregulation of cyp19a1a in XX tilapia; 6) the germ cell SR of foxl3 mutants fails to be rescued by estrogen treatment, indicating that estrogen determines female germ cell fate through foxl3. This review also summarized the effects of deficiency of other steroid hormones, such as androgen, DHP and cortisol, on fish reproduction. Overall, these studies demonstrate that tilapia is an excellent animal model for studying reproductive endocrinology of fish.
尼罗罗非鱼（Oreochromis niloticus），具有 XX/XY 性别决定系统，是一种全球性养殖鱼类，其性成熟时间比大多数养殖鱼类都短。罗非鱼的产卵周期约为 14 天，并且可以在实验室中全年人工繁殖，以获得完全的雌性（XX）和完全的雄性（XY）鱼苗。其基因组序列已经开放，并建立了一个完善的基因编辑平台。其体型适中，方便采集足够的血液来测量激素水平。近年来，我们使用罗非鱼作为动物模型，证实了雌激素对鱼类雌性发育至关重要，因为：1）在 XX 型罗非鱼中，star2、cyp17a1 或 cyp19a1a（编码芳香酶，雌激素合成的关键酶）突变会导致由于雌激素缺乏而出现性反转（SR），而在 XY 型罗非鱼中，star1、cyp11a1、cyp17a2、cyp19a1b 或 cyp11c1 突变会影响生育能力，因为雄激素、皮质醇和 DHP 水平异常；2）当雌激素受体（esr2a/esr2b）突变时，性从雌性转变为雄性，而当雄激素受体突变时，性无法逆转；3）分化的卵巢可以通过抑制雌激素合成转化为功能性睾丸，分化的睾丸可以通过同时添加外源性雌激素和雄激素合酶抑制剂转化为卵巢；4）XY 型罗非鱼中，amhy、dmrt1、gsdf 等雄性途径基因缺失会导致 cyp19a1a 上调引起的 SR；5）XX 型罗非鱼中，foxl2 和 sf-1 等雌性途径基因缺失会导致 cyp19a1a 下调引起的 SR；6）foxl3 突变体的生殖细胞 SR 不能被雌激素治疗挽救，表明雌激素通过 foxl3 决定雌性生殖细胞的命运。本综述还总结了其他类固醇激素（如雄激素、DHP 和皮质醇）缺乏对鱼类生殖的影响。总的来说，这些研究表明，罗非鱼是研究鱼类生殖内分泌学的理想动物模型。
