Lin Chien-Ju, Fan-Chiang Yi-Chun, Dufour Sylvie, Chang Ching-Fong
Department of Aquaculture, National Taiwan Ocean University, Keelung, 20224, Taiwan.
Research Unit BOREA, Biology of Aquatic Organisms and Ecosystems, CNRS 7208/IRD 207/UPMC/UCBN, Muséum National D'histoire Naturelle, Paris, France.
Dev Neurobiol. 2016 Feb;76(2):121-36. doi: 10.1002/dneu.22303. Epub 2015 Jun 8.
The early brain development, at the time of gonadal differentiation was investigated using a protandrous teleost, black porgy. This natural model of monosex juvenile fish avoids the potential complexity of sexual dimorphism. Brain neurogenesis was evaluated by histological analyses of the diencephalon, at the time of testicular differentiation (in fish between 90 and 150 days after hatching). Increases in the number of both Nissl-stained total brain cells, and Pcna-immunostained proliferative brain cells were observed in specific area of the diencephalon, such as ventromedialis thalami and posterior preoptic area, revealing brain cell proliferation. qPCR analyses showed significantly higher expression of the radial glial cell marker blbp and neuron marker bdnf. Strong immunohistochemical staining of Blbp and extended cellular projections were observed. A peak expression of aromatase (cyp19a1b), as well as an increase in estradiol (E2 ) content were also detected in the early brain. These data demonstrate that during gonadal differentiation, the early brain exhibits increased E2 synthesis, cell proliferation, and neurogenesis. To investigate the role of E2 in early brain, undifferentiated fish were treated with E2 or aromatase inhibitor (AI). E2 treatment upregulated brain cyp19a1b and blbp expression, and enhanced brain cell proliferation. Conversely, AI reduced brain cell proliferation. Castration experiment did not influence the brain gene expression patterns and the brain cell number. Our data clearly support E2 biosynthesis in the early brain, and that brain E2 induces neurogenesis. These peak activity patterns in the early brain occur at the time of gonad differentiation but are independent of the gonads.
利用一种雄性先熟的硬骨鱼——黑鲷，对性腺分化时的早期脑发育进行了研究。这种单性幼鱼的天然模型避免了性二态性潜在的复杂性。在睾丸分化时（孵化后90至150天的鱼），通过对间脑的组织学分析来评估脑神经元发生。在间脑的特定区域，如丘脑腹内侧和视前区后部，观察到尼氏染色的全脑细胞数量和增殖细胞核抗原免疫染色的增殖脑细胞数量增加，揭示了脑细胞增殖。定量聚合酶链反应分析显示，放射状胶质细胞标志物脑脂质结合蛋白（blbp）和神经元标志物脑源性神经营养因子（bdnf）的表达显著更高。观察到脑脂质结合蛋白（Blbp）有强烈的免疫组织化学染色以及细胞突起延长。在早期脑中还检测到芳香化酶（cyp19a1b）的峰值表达以及雌二醇（E2）含量的增加。这些数据表明，在性腺分化期间，早期脑表现出E2合成增加、细胞增殖和神经元发生。为了研究E2在早期脑中的作用，对未分化的鱼用E2或芳香化酶抑制剂（AI）进行处理。E2处理上调了脑cyp19a1b和blbp的表达，并增强了脑细胞增殖。相反，AI降低了脑细胞增殖。去势实验并未影响脑基因表达模式和脑细胞数量。我们的数据清楚地支持早期脑中E2的生物合成，并且脑E2诱导神经元发生。早期脑中的这些峰值活动模式发生在性腺分化时，但与性腺无关。
