Regulation of gene expression of pituitary gonadotropins in cyprinid fish.

在硬骨鱼中，人们认为GTH有两种类型，即GTH-I和GTH-II，它们的分子由共同的α和不同的β亚基组成。为了从分子水平上了解两种GTH对性腺发育的调控，我们检测了GTH-Ibeta和-IIbeta亚基的基因表达，并对GTH-Ibeta和-IIbeta基因在金鱼中的表达进行了分析。在产卵早期，雌鱼脑垂体GTH-Iβ和GTH-IIβ的mRNA水平同步升高，而雄鱼只有GTH-IIβ的mRNA水平升高，而GTH Iβ的水平没有升高。性激素的作用。睾酮和雌二醇-17β对GTH-Iβ基因的表达有抑制作用，而对GTH-IIβ基因的表达有刺激作用。这两个基因都是由两个内含子隔开的三个外显子组成的，但在GTH-Ibeta和-IIbeta基因的5个侧翼区域中，推测的调控元件的位置模式是不同的。尽管对GTH基因表达的研究仅限于硬骨鱼，但这些研究表明，GTH-Ibeta和GTH-IIbeta的基因表达在金鱼中受到性激素的不同调控，可能是通过基因的上游调节区。

In teleosts, it is considered that two types of GTH, GTH-I and GTH-II, are produced in the pituitary, and their molecules arc comprised of common alpha and distinct beta subunits. In order to understand regulation of gonadal development by two GTHs at molecular level, we examined gene expression of GTH-Ibeta and -IIbeta subunits, and then characterized GTH-Ibeta and -IIbeta genes in goldfish.Seasonal changes. In females, pituitary mRNA levels of the GTH-Ibeta and -IIbeta increased synchronously in early spawning period, while in males, only GTH-IIbeta mRNA levels, but not GTH I beta, showed an increase. Effect of sex steroids. Testosterone and estradiol-17beta exerted an inhibitory effect on GTH-Ibeta gene expression but a stimulatory effect on GTH-IIbeta gene expression.Characterization of the genes. Both genes consisted of three exons separated by two introns.However, the pattern of the location of the putative regulatory elements was distinct between the 5-flanking regions of the GTH-Ibeta and -IIbeta genes.Although the studies on GTH gene expressions are limited in teleosts, these studies indicate that the gene expressions of GTH-Ibeta and GTH-IIbeta are differentially regulated by sex steroids in goldfish, probably via upstream regulatory regions of the genes.