Molecular cloning of gonadotropin genes and their regulation of expression.

与其他脊椎动物一样，鱼类的生殖活动由脑-垂体-性腺轴组成的内分泌系统调节。以往认为鱼类只有单一的垂体促性腺激素（GTH），但近年来在鲑鱼中发现了两种类型的GTH。虽然鲤科鱼类已被用作研究鱼类生殖内分泌的模式物种，但对鱼类GTH合成的调控还没有很好的研究。为了研究鱼类垂体GTH合成或GTH基因表达的调控机制，特异性cDNA探针是必需的。去年我从金鱼脑垂体中克隆了GTH亚基（Ⅰ和Ⅱ）的cDNA，获得了金鱼GTH的特异性探针，今年我用Norhtern blot分析了GTH基因在性腺成熟过程中的表达。与GTHI在性腺发育早期占主导地位，GTHII在成熟期占主导地位的鲑科鱼类不同，GTHI和II的表达随着金鱼性腺成熟的进展而增加。结果可能反映了鲑鱼和金鱼之间的产卵周期的不同模式，鲑鱼产卵一次，而金鱼产卵几times.I还研究了水温对GTH基因表达的影响。GTHI在低温下表达量较高，GTHII在中温下表达量较高。这些结果表明，水温参与了金鱼GTH基因差异表达的调节。

As in other vertebrates, reproductive activities in fish is regulated by an endocrine system, consisting of brain-pituitary-gonad axis. It had been thought that fish had only single type of pituitarty gonadotropin (GTH), but recently two types of GTH were identified in salmon.Althogh cyprinid species have been used as model species for the study of reproductive endocrinology of fish, it is not well studied on the regulation of GTH synthesis in these species.For the study of regulatory mechanism of GTH synthesis or GTH gene expression in the pituitary, specific cDNA probes are necessities. I cloned cDNA of GTH subunits (I and II) from the pituitary of goldfish last year and obtained specific probes for goldfish GTH.This year, I examined GTH gene expression during gonadal maturation by Norhtern blot analysis. Unlike salmonids in which GTHI dominates during eary stage of gonadal development and GTHII in maturational stage, expression of both GTHI and II showed an increase with the progression of gonadal maturation in goldfish. The results may reflect different patterns of spawning cycle between salmonids and goldfish ; salmonids spawn once during their spawning period, whereas goldfish spawns several times.I also examined effects of water temperature on GTH gene expression. Expression of GTHI was higher at low temperature and that of GTHII at moderate temperature. These results suggest that water temperature is involved in the regulation of differential expression in goldfish GTH genes.