黄颡鱼20β-羟基类固醇脱氢酶Ⅰ和Ⅱ基因特征分析和表达模式研究

CHARACTERATION OF THE DUPLICATED 20β-HSD GENES IN PELTEOBAGRUS FULVIDRACO AND THEIR EXPRESSION PATTERNS AND REGULATIONS

为探讨20β-羟基类固醇脱氢酶Ⅰ和Ⅱ(20β-HSDⅠ/Ⅱ)在黄颡鱼中的基因特征和表达模式,研究从黄颡鱼中克隆了这2个基因的全长c DNA。对鱼类2个20β-HSD的系统进化分析和共线性分析结果发现,20β-hsd基因的复制可能不是TSGD的结果。序列对比结果表明,鱼类2个20β-HSD可能具有相似的空间结构,结合相似的辅酶和底物,但催化产物可能有差异。黄颡鱼2个20β-hsd基因均表达于多个组织,其中20β-hsdⅠ主要表达于精巢、卵巢、头肾和肾脏中,而20β-hsdⅡ则高表达于精巢、卵巢、心脏、头肾、肾脏、肠、垂体和肝脏。季节表达模式的研究发现,在繁殖季节(5月)的黄颡鱼精巢中,20β-hsdⅠ的表达相对较低,而20β-hsdⅡ高表达。对黄颡鱼雄性成鱼注射人绒毛膜促性腺激素(h CG)(1000 IU/kg体重)后,20β-hsdⅠ的表达先显著升高,随后迅速显著下调;而20β-hsdⅡ的表达则持续显著上升。上述结果表明,黄颡鱼20β-hsdⅠ和20β-hsdⅡ在h CG处理下表达模式存在较大差异。

Maturation inducing hormone(MIH)plays pivotal roles in gamete maturation,ovulation and spermiation offish.In most teleost species,17α,20β-dihydroxy-4-pregnen-3-one(DHP)is the major MIH.The steroidogenic enzyme,named20β-hydroxysteroid dehydrogenase(20β-HSD),is responsible for DHP production in several teleost species.Todate,only one copy of20β-hsd has been characterized in vertebrates,including fish.In this study,two copies of20β-hsd genes were identified in genomes of several fish species.Phylogenetic and syntenic analyses revealed that the duplicationof20β-hsd gene may not result from the teleost specific genome duplication(TSGD).Multiple-alignment resultsindicated that these two enzymes might possess similar spatial structures and co-enzyme/substrate binding motifs,whereas,their catalytic activities might differ.The duplicated copy of20β-hsd was further cloned from yellow catfish(Pelteobagrus fulvidraco).Tissue distribution results showed that,20β-hsdⅠmRNA was mainly expressed in testis,ovary,head kidney and kidney,while20β-hsdⅡmRNA was mainly located in testis,ovary,heart,head kidney,kidney,intestine,pituitary and liver.Seasonal expression results revealed that,lower20β-hsdⅠexpression and higher20β-hsdⅡexpression were observed in male fish during reproductive time window(in May).Three hours after injectionof hCG(1000IU/kg body weight),the expression of20β-hsdⅠwas up-regulated and then suppressed significantly,while the expression of20β-hsdⅡwas up-regulated in a time dependent manner in male fish.These resultsdemonstrated the differential regulation pattern of20β-hsdⅠand20β-hsdⅡin response to hCG.