Laboratory of Advanced Animal and Marine Bioresources, Graduate School of Bioresource and Bioenvironmental Sciences, Kyushu University, Fukuoka 812-8581, Japan.
Gen Comp Endocrinol. 2010 May 15;167(1):153-63. doi: 10.1016/j.ygcen.2010.01.018. Epub 2010 Feb 4.
Grass puffer, Takifugu niphobles, has unique spawning behavior; spawning occurs on beach only for several days around new moon and full moon from spring to early summer. To investigate the role of gonadotropin-releasing hormone (GnRH) in the reproductive function, genes encoding three types of GnRHs, namely seabream GnRH (sbGnRH), chicken GnRH-II (cGnRH-II) and salmon GnRH (sGnRH), were cloned and changes in their mRNA amounts were examined over the spawning season. In addition, changes in the pituitary gonadotropin subunit mRNAs and the plasma steroid hormones were examined over the spawning season. Fishes were assessed at four reproductive stages, i.e., in December (early maturation), in April (maturing), in May (spawning), and in July (post-spawning). Moreover, spawning fish just after releasing eggs and sperm were taken at a spawning bed. The amounts of sbGnRH mRNA were substantially elevated in May and the spawning fish in both sexes, concomitant with considerable elevations of follicle-stimulating hormone and luteinizing hormone beta subunit mRNAs and plasma estradiol-17beta (E(2)) and testosterone (T) levels. There were strong positive correlations between the sbGnRH mRNA and the plasma E(2) and T levels over the spawning season in both sexes. The amounts of cGnRH-II mRNA showed no noticeable changes except for an increase in the post-spawning females. The amounts of sGnRH mRNA in the males were significantly increased in May, but they were low in the spawning males. In the females, sGnRH mRNA increased from the maturing stage and reached a maximum in the post-spawning stage, in which a positive correlation with the plasma cortisol levels was observed. These specific changes suggest that the expression of three types of GnRH genes is differentially regulated during the spawning season, and sex steroids may be important for the differential expression of GnRH genes.
赤点石斑鱼具有独特的产卵行为；仅在新月和满月前后的春末至初夏的数天内在海滩产卵。为了研究促性腺激素释放激素（GnRH）在生殖功能中的作用，克隆了编码三种 GnRH 类型的基因，即真鲷 GnRH（sbGnRH）、鸡 GnRH-II（cGnRH-II）和鲑鱼 GnRH（sGnRH），并检查了它们在产卵季节的 mRNA 量变化。此外，还检查了垂体促性腺激素亚基 mRNA 和血浆类固醇激素在产卵季节的变化。鱼类在四个生殖阶段进行评估，即 12 月（早期成熟）、4 月（成熟）、5 月（产卵）和 7 月（产卵后）。此外，在产卵床上取刚刚释放卵子和精子的产卵鱼。sbGnRH mRNA 的量在 5 月和雌雄鱼的产卵期大量增加，伴随着促卵泡激素和黄体生成素β亚基 mRNA 以及血浆雌二醇-17β（E（2））和睾酮（T）水平的显著升高。在整个产卵季节，sbGnRH mRNA 与血浆 E（2）和 T 水平之间存在强烈的正相关。除了产卵后雌鱼的增加外，cGnRH-II mRNA 的量没有明显变化。雄鱼的 sGnRH mRNA 量在 5 月显著增加，但在产卵雄鱼中较低。在雌鱼中，sGnRH mRNA 从成熟阶段开始增加，并在产卵后阶段达到最大值，与血浆皮质醇水平呈正相关。这些特定的变化表明，三种 GnRH 基因的表达在产卵季节期间受到差异调节，而性激素可能对 GnRH 基因的差异表达很重要。
