Wu Xuemei, Wang Pei, Brown Christopher A, Zilinski Carolyn A, Matzuk Martin M
Department of Pathology, Baylor College of Medicine, Houston, Texas 77030, USA.
Biol Reprod. 2003 Sep;69(3):861-7. doi: 10.1095/biolreprod.103.016022. Epub 2003 May 28.
Zygote arrest 1 (ZAR1) is an ovary-specific maternal factor that plays essential roles during the oocyte-to-embryo transition. In mice, the Zar1 mRNA is detected as a 1.4-kilobase (kb) transcript that is synthesized exclusively in growing oocytes. To further understand the functions of ZAR1, we have cloned the orthologous Zar1 cDNA and/or genes for mouse, rat, human, frog, zebrafish, and pufferfish. The entire mouse Zar1 gene and a related pseudogene span approximately 4.0 kb, contain four exons, and map to adjacent loci on mouse chromosome 5. The human ZAR1 orthologous gene similarly consists of four exons and resides on human chromosome 4p12, which is syntenic with the mouse Zar1 chromosomal locus. Rat (Rattus norvegicus) and pufferfish (Fugu rubripes) Zar1 genes were recognized by database mining and deduced protein alignment analysis. The rat Zar1 gene also maps to a region that is syntenic with the mouse Zar1 gene locus on rat chromosome 14. Frog (Xenopus laevis) and zebrafish (Danio rerio) Zar1 orthologs were cloned by reverse transcription-polymerase chain reaction and rapid amplification of cDNA ends analysis of ovarian mRNA. Unlike mouse and human, the frog Zar1 is detected in multiple tissues, including lung, muscle, and ovary. The Zar1 mRNA appears in the cytoplasm of oocytes and persists until the tailbud stage during frog embryogenesis. Mouse, rat, human, frog, zebrafish, and pufferfish Zar1 genes encode proteins of 361, 361, 424, 295, 329, and 320 amino acids, respectively, and share 50.8%-88.1% amino acid identity. Regions of the N-termini of these ZAR1 orthologs show high sequence identity among these various proteins. However, the C-terminal 103 amino acids of these proteins, encoded by exons 2-4, contain an atypical eight-cysteine Plant Homeo Domain motif and are highly conserved, sharing 80.6%-98.1% identity among these species. These findings suggest that the carboxyl-termini of these ZAR1 proteins contain an important functional domain that is conserved through vertebrate evolution and that may be necessary for normal female reproduction in the transition from oocyte to embryonic life.
合子阻滞1（ZAR1）是一种卵巢特异性母体因子，在卵母细胞向胚胎的转变过程中发挥着重要作用。在小鼠中，Zar1 mRNA被检测为一种1.4千碱基（kb）的转录本，仅在生长中的卵母细胞中合成。为了进一步了解ZAR1的功能，我们克隆了小鼠、大鼠、人类、青蛙、斑马鱼和河豚的直系同源Zar1 cDNA和/或基因。整个小鼠Zar1基因和一个相关的假基因跨度约为4.0 kb，包含四个外显子，并定位在小鼠5号染色体上相邻的基因座上。人类ZAR1直系同源基因同样由四个外显子组成，位于人类4号染色体p12上，与小鼠Zar1染色体基因座同线。大鼠（褐家鼠）和河豚（红鳍东方鲀）的Zar1基因通过数据库挖掘和推导的蛋白质比对分析得以识别。大鼠Zar1基因也定位在与大鼠14号染色体上小鼠Zar1基因座同线的区域。青蛙（非洲爪蟾）和斑马鱼（斑马鱼）的Zar1直系同源基因通过逆转录-聚合酶链反应和卵巢mRNA的cDNA末端快速扩增分析进行克隆。与小鼠和人类不同，青蛙Zar1在包括肺、肌肉和卵巢在内的多个组织中都能检测到。Zar1 mRNA出现在卵母细胞的细胞质中，并在青蛙胚胎发育的尾芽阶段之前一直存在。小鼠、大鼠、人类、青蛙、斑马鱼和河豚的Zar1基因分别编码361、361、424、295、329和320个氨基酸的蛋白质，氨基酸同一性为50.8%-88.1%。这些ZAR1直系同源物N端区域在这些不同蛋白质之间显示出高度的序列同一性。然而，这些蛋白质由外显子2-4编码的C端103个氨基酸包含一个非典型的八个半胱氨酸的植物同源结构域基序，并且高度保守，在这些物种之间的同一性为80.6%-98.1%。这些发现表明，这些ZAR1蛋白质的羧基末端包含一个重要的功能域，该功能域在脊椎动物进化过程中保守，可能是卵母细胞向胚胎生命转变过程中正常雌性生殖所必需的。
