金钱鱼促性腺激素受体基因克隆及其在性腺发育不同时期mRNA表达水平的分析

Gene cloning of gonadotropic hormone receptors and their mRNA expressions at different development stages of the gonad in Scatophagus argus

为了解金钱鱼促性腺激素受体基因(GtHRs)在金钱鱼性腺发育中的作用,采用反转录PCR(Rt-PCR)与cDNA末端快速克隆(RACE)首次克隆了金钱鱼卵泡刺激素受体(FSHR)和促黄体生成素受体(LHR)的cDNA序列全长。FSHR的cDNA全长2538 bp,编码702个氨基酸,LHR的cDNA全长3315 bp,编码722个氨基酸,它们都含有属于糖蛋白激素受体(GHR)家族的典型跨膜螺旋结构区域(TM helix)。同源性分析显示金钱鱼GtHRs与欧洲鲈的相似性最高,且GtHRs在进化中具有一定的保守性。性腺不同时期表达分析表明,在卵巢Ⅰ期时,FSHR高水平表达,Ⅱ、Ⅲ、Ⅳ期时在较低水平表达。在精巢中,FSHR的表达水平在Ⅰ、Ⅱ、Ⅲ期逐渐升高并在Ⅲ期达到最高,Ⅳ期开始下降。LHR在金钱鱼卵巢和精巢的Ⅰ、Ⅱ、Ⅲ期低水平表达,在Ⅳ期表达水平达到最高。研究表明,FSHR在金钱鱼性腺发育早期扮演重要作用,LHR与卵子和精子的成熟有关。

In the present study, follicle-stimulating hormone receptor（FSHR） and luteinizing hormone receptor（LHR） genes were cloned by using reverse transcription-polymerase chain reaction（RT-PCR） and rapid amplification of cDNA 5′ and 3′ ends（RACE） in Scatophagus argus. The full-length of FSHR cDNA was 2538 bp, encoding a 702 amino acid protein and the full-length of LHR cDNA was 3315 bp, encoding a 722 amino acid protein. Both of them contain seven TM helix domains, a feature of glycoprotein hormone receptor（GHRs） family.Multiple sequence alignment shows that S. argus GtHRs have the highest homology with that of Dicentrarchus labrax. mRNA expression patterns showed that a high expression level of FSHR was detected at stage I in ovary,followed by an obvious decrease at stage II, III and IV. In the testis, the expression of FSHR gene increased gradually during early stages（stage I, II and III）, and apparently reduced at stage IV. Our results indicates that according to H.E staining, sperm maturation started at stage III, implying FSHR played an important role in early stages of the gonadal development, and LHR is vital for sperms/oocytes maturation and release as well as sperms.