van Nes Solveig, Moe Maren, Andersen Øivind
AKVAFORSK-Institute of Aquaculture Research, University of Life Sciences, As, Norway.
Mol Reprod Dev. 2005 Dec;72(4):437-49. doi: 10.1002/mrd.20373.
P450aromatase (CYP19) is an essential part of the enzyme complex catalyzing the conversion of androgens into estrogens, which is a key reaction in the sex differentiation in vertebrates. Two full-length cDNAs encoding the genetic distinct CYP19A and CYP19B isozymes were isolated from Atlantic halibut (Hippoglossus hippoglossus) by RT-PCR of ovarian and brain RNA, respectively. The deduced enzymes CYP19A and CYP19B of 523 and 508 residues, respectively, showed less sequence homology with each other than with their orthologs in other teleost species. This indicates an ancient duplication of the common cyp19 gene that was supported by the constructed phylogenetic tree. Whereas cyp19b mRNA was ubiquitously expressed in the adult male and female, the cyp19a expression was more restricted and showed sex specificity in the gonads as verified by RT-PCR. The detection of transcripts encoding both CYP19A and CYP19B in the embryo clearly preceding any morphological gonadal sex differentiation provides evidence that these genes play important roles in early developmental stages in teleosts. The distinct temporal and spatial expression of the two cyp19 genes in larvae and adults, respectively, together with their low sequence similarity strongly indicate that the genes are differently regulated and that the encoding isozymes have adopted distinct functional roles in Atlantic halibut.
细胞色素P450芳香化酶（CYP19）是催化雄激素转化为雌激素的酶复合物的重要组成部分，这是脊椎动物性分化中的关键反应。分别通过对卵巢和脑RNA进行逆转录聚合酶链式反应（RT-PCR），从大西洋庸鲽（Hippoglossus hippoglossus）中分离出编码遗传上不同的CYP19A和CYP19B同工酶的两个全长互补DNA（cDNA）。推导得出的酶CYP19A和CYP19B分别有523和508个残基，它们彼此之间的序列同源性低于与其他硬骨鱼物种中的直系同源物的同源性。这表明常见的cyp19基因发生了古老的复制，这一点得到了构建的系统发育树的支持。虽然cyp19b信使核糖核酸（mRNA）在成年雌雄个体中普遍表达，但通过RT-PCR验证，cyp19a的表达更具局限性，且在性腺中表现出性别特异性。在胚胎中明显先于任何性腺形态性别分化检测到编码CYP19A和CYP19B的转录本，这证明这些基因在硬骨鱼的早期发育阶段发挥重要作用。两种cyp19基因在幼体和成体中分别有不同的时空表达，再加上它们较低的序列相似性，有力地表明这些基因受到不同的调控，且编码的同工酶在大西洋庸鲽中发挥着不同的功能作用。
